HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY INTERNATIONAL TRAINING INSTITUTE FOR MATERIALS SCIENCE (ITIMS)

ABSTRACTs AND PROCEEDINGS THE 12TH ASIAN CONFERENCE ON CHEMICAL SENSORS ACCS2017

Bachkhoa Publishing House

Proceedings Editorial board:

Nguyen Duc Hoa Chu Manh Hung Nguyen Van Toan

Sponsors: Japan Association of Chemical Sensors National Foundation for Science and Technology Development (Nafosted, Vietnam) Taiwan Chemical Sensor Society HORIBA Vietnam Company Limited Hanoi University of Science and Technology (HUST) International Training Institute for Materials Science (ITIMS)

25th anniversary of the International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology: 1992-2017

A. COMMITTEE ACCS International Steering Committee Chair Prof. Chii-Wann Lin, National Taiwan University, Taiwan Vice Chair Prof. Yasuhiro Shimizu, Nagasaki University, Japan Members Prof. Jun-ichi Anzai, Tohoku University, Japan Prof. Wan-Young Chung, Pukyong National University, Korea Prof. Shin-Won Kang, Kyungpook National University, Korea Prof. Jong-Heun Lee, Korea University, Korea Prof. Chao-Sung Lai, Chang Gung University, Taiwan Prof. Osamu Niwa, Saitama Institute of Technology, Japan Prof. Ali Yeon Md Shakaff, Universiti Malaysia Perlis, Malaysia Prof. Youichi Shimizu, Kyushu Institute of Technology, Japan Prof. Ooi Kiang Tan, Nanyang Technological University, Singapore Prof. Zi-Long Tang, Tsinghua University, China Dr. Adisorn Tuantranont, National Science and Technology Development Agency, Thailand Prof. Tatsuo Yoshinobu, Tohoku University, Japan Prof. Ping Wang, Zhejiang University, China

i

Advisory Committee Prof. Dr. Jong-Heun Lee, Korea University, Korea Prof. Dr. Yasuhiro Shimizu, Nagasaki University, Japan Prof. Dr. Osamu Niwa, Saitama Institute of Technology, Japan General Chair Prof. Dr. Dinh Van Phong, Vice-Rector of Hanoi University of Science and Technology Prof. Dr. Nguyen Duc Chien, Chair of Vietnam Materials Research Society Conference Chair Prof. Dr. Nguyen Van Hieu, Hanoi University of Science and Technology Assoc. Prof. Dr. Nguyen Duc Hoa, Hanoi University of Science and Technology Local Organizing Committee Assoc. Prof. Dr. Nguyen Phuc Duong, Hanoi University of Science and Technology Assoc. Prof. Dr. Mai Anh Tuan, Hanoi University of Science and Technology Assoc. Prof. Dr Nguyen Van Duy, Hanoi University of Science and Technology Assoc. Prof. Dr Nguyen Van Quy, Hanoi University of Science and Technology Assoc. Prof. Dr Hoang Sy Hong, Hanoi University of Science and Technology Assoc. Prof. Dr Nguyen Van Duy, Hanoi University of Science and Technology Assoc. Prof. Dr Dang Duc Vuong, Hanoi University of Science and Technology Assoc. Prof. Dr Nguyen Huu Lam, Hanoi University of Science and Technology Assoc. Prof. Dr Truong Thi Ngoc Lien, Hanoi University of Science and Technology Dr. Nguyen Xuan Viet, Hanoi University of Science Dr. Ho Truong Giang, VietNam Academy of Science and Technology ii

Secretariat Dr. Chu Manh Hung, Hanoi University of Science and Technology Dr. Bui Thi Hang, Hanoi University of Science and Technology Dr. Tran Thi Viet Nga, Hanoi University of Science and Technology Dr. Dao Thi Thuy Nguyet, Hanoi University of Science and Technology Dr. Chu Thi Xuan, Hanoi University of Science and Technology Dr. To Thanh Loan, Hanoi University of Science and Technology Dr. Dang Thi Thanh Le, Hanoi University of Science and Technology Publicity & Website Assoc. Prof. Nguyen Van Duy Dr. Ngo Ngoc Ha Mr. Hoang Quoc Khanh Local Arrangement & Transportation Dr. Nguyen Van Toan, Hanoi University of Science and Technology Dr. Luong Ngoc Anh, Hanoi University of Science and Technology Ms. Nguyen Thi Phuong Loan, Hanoi University of Science and Technology

iii

the 12th Asian Conference on Chemical Sensors (ACCS2017) November 12-15, 2017, Pan Pacific Hanoi, Vietnam PROGRAM: Time 14:0018:00 18:0021:00

1st Day: November, 12, 2017 Registration, Pancific Ballroom Welcome Reception (Pancific Ballroom, 2nd Floor)

2nd Day: November, 13, 2017 8:00-8:30

Registration (cont.)

8:30-8:45

Opening (Pacific Ballroom, 2nd Floor)

8:45

PLENARY SESSION 01: Charis: Prof. Nguyen Duc Chien & Prof. Dojin Kim

8:45-9:25

Keynote Speech 1: Prof. Shen-Ming Chen, National Taipei University of Technology, Taiwan Title: Application of Nanocomposite Materials Modified Electrodes in Electrochemical Sensing of Biomolecules and Biosensors

9:25-10:05

Keynote Speech 2: Prof. Jong-Heun Lee, Korea University, Korea Title: Morphological, Compositional, and Heterostructural Design of Oxide Semiconductor Chemiresistors: New Challenges and New Opportunities

10:0510:25

Coffee break (Conference corridor)

iv

PARALLEL SESSION ROOM A (Pacific 1) 10:2512:00

10:2510:50

10:5011:15

11:1511:30

11:3011:45

ROOM B (Pacific 2)

A – Sensor Fundamentals (A1); B – Sensor System & Devices (B1); Chairs: Prof J.R.Morante & Prof. Inkyu Chairs: Prof. Young-Woo Heo & Park Prof. Giorgio Sberveglieri Adsorption/combustiontype micro VOC sensors —Effects of Nanocarbon Film Inv. Prof. Takeo Prof. Osamu catalytic combustion Based Sensors for 01 Hyodo Niwa activities of VOCs on Heavy Metal their gas-sensing Detection behaviour Nanostructured heterojunctions for Core-Shell Structured high performance Inv. Prof. Sang Prof. Ho Nanomaterials for chemoresistive gas 02 Sub Kim Won Jang Sensitive Gas Sensors sensors based metal oxides and 2dimensional materials

Oral 01

Oral 02

Ni Luh Wulan Septiani

Effect of Zinc Oxide Morphology on the Carbon Monoxide Sensing Properties

Ayaka Yamamoto

Dr. Rawat Jaisutti

Photochemically Activated IndiumGallium-Zinc Oxide for Flexible and RoomTemperature Operable Gas Sensors

Yuta Kuwaki

v

ROOM C (Pacific 3) C– Application & Technology (C1); Chairs: Prof. Shinji Tamura & Dr. Adisorn Tuantranont

Prof. WanYoung Chung

Battery-free Technology for Wireless Sensor Applications

Prof. Tulliani Jean marc Christian

Biochar as a sensing material for gas sensors

Utilization of a Solid Electrolyte CO2 Sensor for the Performance Yang Li Evaluation of CO2 Capture Materials Solid electrolyte gas sensor using proton conductive graphene oxide

Dr. Kumi Y. Inoue

Determination of Nitrate Ions in Potable Water Using a Miniaturized Electrochemical Sensor Liquid-junction-free reference electrode system for amperometry using a closed bipolar electrode

11:4512:00

Oral 03

Dr. Sen Liu

High-performance NO2 sensor based on MoS2modified reduced graphene oxide

Bin Wang

12:0013:30

13:5514:20

14:2014:35

Retno Rahmawati

The potency of Fe3O4 / MWCNT nanocomposite synthesized from local iron sand for electrochemical biosensor

LUNCH A – Sensor Fundamentals (A2); Chairs: Prof. Ho Won Jang & Dr Nicolae Barsan

13:3013:55

Fabrication of wellordered porous array mounted with gold nanoparticles and enhanced sensitivities for mixed potentialtype zirconia-based NH3 sensor

Inv. 01

Inv. 02

Oral 01

Prof J.R.Morante

Fully integrated electrochemical micro machined sensor based on silicon platforms

Prof. Shinji Tamura

Low-temperature Operative Catalytic Combustion-type Hydrogen Gas Sensors Incorporating Cerium Oxide-Zirconium Oxide Based Catalysts

Youichi Shimizu

Solid Electrolyte Impedancemetric NOx Sensor Using Zeolite Receptor

B – Sensor System & Devices (B2); Chairs: Prof. Takeo Hyodo & Prof. Nguyen Van Quy

C– Application & Technology (C2); Chairs: Prof. Osamu Niwa & Prof. Nguyen Van Hieu

Prof. Giorgio Sberveglieri

Metal oxides nanowires for chemical sensors and Electronic Noses

Prof. Chatchawal Wongchoosuk

Prof. Inkyu Park

A new route to the fabrication of heterogeneous metal oxide nanomaterial array for integrated chemical sensors

Dr. Adisorn Tuantranont

Xusheng Zhang

The Design of Module e-Nose Combining with Pattern Recognition for Lung Cancer Screening

vi

Ani Mulyasuryani

Flexible Gas Sensors Based on Zero- to Three-Dimensional Carbon Nanostructures

Printed Graphene Sensors: From research to commercialization Nata de Coco Membrane on Screen Printed Potentiometric Phenol Sensors

14:3514:50

14:5015:05

15:0515:20

Oral 02

Oral 03

Oral 04

Dr. Eadi Sunil Babu

Gas Sensor Based on FeDoped ZnO nanorods for the detection of Volatile Organic gases (VOCs) at Room Temperature

A.P. Teng Fei

Humidity sensors based on stable polyelectrolytes

Dr. Xueli Yang

Hydrothermal synthesis and gas sensing property of Zn2SnO4/SnO2 flowerlike composite

15:2015:35 15:2017:25

15:3516:00

Ching-Hsu Yang

Surface Functionalization of Gold Surfaces with Polypeptide: A LowFouling Zwitterionic Surface for Detecting Placenta Growth Factor

Lanlan Guo

Detection of triethylamine with fast response by Al2O3/αFe2O3 composite nanofibers

Hua Quoc Trung

Organophosphate Pesticides Determination by 3D microPADs and ePADs

Jun-Sik Kim

Highly sensitive and selective NO2 gas sensors using multishelled WO3 yolkshell structures

You-Xiang Wu

Potentiometric Ascorbic Acid Determination by MBs-Ascorbate Oxidase/GO/IGZO/A l Membrane Assembled

Lingwei Ma

Design of Ag Nanorods for SERS with Sensitivity and Thermal Stability

Coffee break (Conference corridor) A – Sensor Fundamentals (A3); Chairs: Prof. Sang Sub Kim & Prof. WanYoung Chung

Inv. 01

Prof. Dojin Kim

Nanostructural Oxide Gas Sensors toward Room Temperature Operation

B – Sensor System & Devices (B3); Chairs: Prof. Tatsuo Yoshinobu & Prof. Tran Dai Lam

Prof. Ping Wang

vii

The Biomimetic Cellbased Biosensors for Applications in Biomedical and Environmental Detection

C– Application & Technology (C3); Chairs: Prof. Sungjin Kim & Prof. Hoang Sy Hong

Prof. YoungWoo Heo

Energy bandgap tuning of halide perovskites for optical-sensors

16:0016:25

16:2516:40

16:4016:55

16:5517:10

17:1017:25

Inv. 02

Oral 01

Oral 02

Oral 03

Oral 04

Dr. Nicolae Barsan

Anna Staerz

Noble Metal Sensitization of SnO2 and WO3 based Gas Sensors – How Does it Work

The Fundamental Characteristics of WO3 Based Sensors

Prof. Masanobu Matsuguchi

Poly(Nisopropylacrylamide) Nanoparticle?Based Gas Sensor Coating Prepared from Binary Aqueous

Dr. Hao Wan

Wearable and rapid gas sensing with microfabricated room temperature ionic liquid electrochemical sensors

Ying Gan

Impedimetric Determination of Mercury(II) Based on Electrochemical DNA Biosensor

Prof. ChingChou Wu

Rolf Seifert

A Cell-Based Chip Integrated with Microfluidic Control and Dissolved Oxygen Sensors for Estimation of Cellular Respiratory Activity Breath Control in Respiratory Air and Simultaneous Analysis of Sensor Data

Dr. Linh Viet Nguyen

Sumeng Zou

Biochemical sensing with microstructured optical fibers

Quantitative analysis of chemicals in unknown system by surface-enhanced Raman scattering spectroscopy A study of deformed TiO2 aggregates graphene nanocomposites as photoanode for dyesensitized solar cell

Hui-Pin Cheng

Development of a rapid and sensitive biosensor for biological toxins

Jianghao Li

Plasmonic Resonance Modes and SERS Performance of Outof-plane Silver Vshape Substrates

Yuki Shiraishi

Myotube cell-based sensing of insulin analogs with a SPR imaging system

Cian yi Wu

Enzymatic Flexible Arrayed Urea Biosensor Based on GO/TiO2 Films Modified by Magnetic Beads

Dr. Ngo Ngoc Ha

On the dynamics of photo-generated carriers in Si-Ge quantum dots

viii

Cheng-Yueh Chen

3rd Day: November, 14, 2017 A – Sensor Fundamentals (A4); Chairs: Prof. Kengo Shimanoe & Prof. Dang Duc Vuong

8:3010:05

8:308:55

8:559:20

9:209:35

9:359:50

Inv. 01

Inv. 02

Oral 01

Oral 02

Prof. Tatsuo Yoshinobu

On the Possibility of LAPS as a Sensing Element in Microfluidic Devices

Prof. HanSheng Chuang

Rapid Disease Screening with a Diffusometric Immunosensor

Anna Roosdiana

Enzymatic synthesis of cellulose succinate as raw material of uric acid biosensor membrane

QuangHuy Do

3D FEM simulation of the effects of humidity sensing layer (ZnO) on response of SAW sensor based on ZnO/IDTs/AlN/Si structure

D – Chemometrics, Modelling & Evaluation (D1); Chair: Prof. Manabu Tokeshi & Prof. Ching-Chou Wu

Prof. ShinWon Kang

Prof. M. Teresa S.R.Gomes

Hui-Wen Liu

Dr. Jochen Niemeyer

ix

Development of Fast and Highly Sensitive Interdigitated Capacitor Based Taste Sensor Array Evaluation of VOC’s emitted from historic papers using a nondestructive approach: an electronic nose based on acoustic wave sensors Spatial Selective Surface Functionalization of Surface Plasmon Resonance Biosensor via Thiol-Ene Click reaction Rigidly tethered bisphosphoric acids: Novel probes for the detection of ferric ions by fluorescence and CD-spectroscopy

E – Advanced Materials and Nanotechnology (E1); Chairs: Prof. Chih-Ting Lin & Prof. Nguyen Huu Lam Electrochemilumines cence biosensors for Prof. Eiichi high sensitive Tamiya medical diagnosis and rapid antioxidants detection

Prof. Chao Sung Lai

Transistor Based Biosensors and its Applications

Shengming Cheng

QCM-based humidity sensor and sensing properties employing colloidal SnO2 nanocrystals

Xiaobing Hu

Highly sensitive H2S gas sensors based on Pd-doped CuO nanoflowers with low operating temperature

9:5010:05

Oral 03

Ming-Jie Lin

The Impedimetric Bioaffinity Sensing Chip Integrated with an Electrohydrodynamic Centripetal Vortex

10:0510:20 10:2011:55

10:2010:45

10:4511:10

11:1011:25

A – Sensor Fundamentals (A5); Chair: Prof. M. Teresa S.R.Gomes & Dr Truong Thi Ngoc Lien

Inv. 01

Inv. 02

Oral 01

Volatile imaging system “Sniff-cam” using alcohol Kenta dehydrogenase Iitani for ethanol and acetaldehyde after drinking Coffee break (Conference corridor) D – Chemometrics, Modelling & Evaluation (D2); Chair: Prof. Hiroshi Ishida & Dr. Toshio Itoh

Prof. Changduk Yang

Improving efficiency and stability of polymer solar cells via addition of n-type macromolecular additive

E – Advanced Materials and Nanotechnology (E2); Chair: Prof. Shin-Won Kang & Dr. Linh Viet Nguyen How to get multiselectivity from Dr. Matteo resistive gas sensors Tonezzer, based on nanostructured metal oxides

Prof. Genxi Li

Electrochemical and colorimetric biosensors for the assay of disease marker proteins with clinical applications

Prof. Sungjin Kim

Growth of Heterostructured Bi2O3– ZnO Photocatalyst and Its Enhanced Photocatalytic Activity

Prof. Yutaka Ohno

Highly-sensitive, flexible electrochemical biosensor based on carbon nanotube thin film

Prof. Manabu Tokeshi

Fluorescence Polarization Measurement System for Multi-Sample Immunoassay

Prof. Geyu Lu

High performance gas sensors based on mesoporous semiconducting oxides

Chang-Hoon Kwak

Highly selective and sensitive ethanol sensor using urchin-like Mgdoped ZnO nanowire networks

Satoshi Ono

VOC-sensing properties of YSZ-based mixedpotential type gas sensors: Effects of fabrication methods and microstructure of Aubased electrodes

Prof. Tomoyuki Yasukawa

Array of Precise Cell-pairs Based on Positive Dielectrophoresis

x

11:2511:40

11:4011:55

Oral 02

Oral 03

Prof. HyungGi Byun

Short-term drift compensation techniques based on chemical sensors array

Seong-Yong Jeoong

Highly selective and sensitive benzene gas sensor using Pd-SnO2 yolk-shell microreactors with a catalytic Co3O4 overlayer

Dr. Koichi Suematsu

Analysis of Oxygen Adsorption on Surface of Metal Oxide to Understand Sensing Mechanism of Semiconductor Gas Sensors

Krishnan Murugappan

Seo Yun Park

Fast response and reliable humidity sensors based on rGO/TiO2 hybrid composites

Yi-Hung Liao

Electrochemical Bridging of Conducting Polymers at the Percolation Threshold for Chemiresistors Investigation of wireless potentiometric glucose biosensor sensing system based on ruthenium dioxide membrane used for homecare

LUNCH

13:3015:30

13:3013:55

13:5514:20

A – Sensor Fundamentals (A6); Chairs: Prof. Genxi Li & Dr. Matteo Tonezzer

Inv. 01

Inv. 02

Prof. Toshio Itoh

Semiconductive Gas Sensors for LowConcentrate Volatile Organic Compounds (VOCs)

Prof. Kengo Shimanoe

Gas sensing properties of MEMS-type metal oxide gas sensor: Design of receptor function for pulse-heating mode

D – Chemometrics, Modelling & Evaluation (D3); Chairs: Prof. Chao-Sung Lai & Prof. Han-Sheng Chuang Mobile Robot Prof. Olfaction: Using Hiroshi Actively Generated Ishida Airflow to Enhance Chemical Reception

Prof. ChihTing Lin

xi

CMOS-based Biomolecular Diagnosis Technologies

E – Advanced Materials and Nanotechnology (E3); Chairs: Prof. Phuong Dinh Tam & Dr. Eadi Sunil Babu Prof. C. GomezYanez

Defect chemistry in ferroelectric materials

Prof. Tran Dai Lam

Ultrasensitive acetylcholine sensor based on the electron transfer promotion on electrochemically activated graphene electrodes

14:2014:35

14:3514:50

14:5015:05

15:0515:20

15:2015:35

Oral 01

Oral 02

Oral 03

Oral 04

Oral 05

Yeon Hoo Kim

Two-dimensional NbS2 gas sensor for room temperature NO2 detection

Nguyen Minh Hieu

A room temperature ammonia gas sensor based on iron oxide plus carbon nanotube structure

Knittable and wearable gas sensors using reduced graphene oxide Chung won covered carbon fabrics Lee decorated with metal catalysts for enhanced selectivity Tailoring Chemically Converted Graphenes Using a Water-soluble Prof. Pyrene Derivative with a Joohoon Kim Zwitterionic Arm for Sensitive Electrochemiluminescen ce-based Analyses

Prof. Zhigang Zhu

Highly sensitive H2S gas sensors based on Pddoped CuO nanoflowers with low operating temperature

Tae Hoon Kim

Gas Sensing Characteristics of metal-doped Tungsten Oxide prepared from (NH4)2WS4 precursor

Prof. Izumi Kubo

Hui-Yun, Luo

A Novel Monolithic Phase sensitive Surface Plasmon Resonace Biosensor

Ching-Hsu Yang

Jun Min Suh

Nickel Oxide Decorated Cobalt Oxide Nanorods for Enhanced Benzene Selectivity

Dr. Hafiza Mohamed Zuki

Development of Electrochemical Sensing System for the Detection of Domoic Acid

Prof. Huan Liu

Solution-processed metal sulfides for room-temperature NO2 detection

xii

Electrochemical Insulin Sensor Utilizing a DNA AptamerImmobilized Electrode Development of a Sensitivity-Enhanced Surface Plasmon Resonance Aptasensor for the Detection of Arsenic

Dong-Yun Lee

Electrochemical Properties of Miniature Gas Sensors using SemiSolid Electrolytes

You Lun Deng

Photoelectric Characteristics of Au Nanoparticles Modified ZnO Nanorods Composite Films on ITO Glass

Jae-Hyeok Kim

Cr2O3/ZnCr2O4 heteronanostructures for ultraselective and sensitive detection of xylene

15:3515:50

Coffee break (Conference corridor)

15:5016:35

POSTER SESSION (Conference corridor); Chairs: Prof. Nguyen Van Duy, Dr. Ngo Ngoc Ha, Dr. Chu Manh Hung, Dr. Dang Thi Thanh Le PLENARY SESSION 02 Chairs: Prof. Chii-Wann LIN, & Prof. Yasuhiro SHIMIZU

16:3517:15

Keynote Speech 3: Prof. Jun-ichi Anzai, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan Title: Layer-by-layer assemblies as key materials in biosensing and controlled release

17:2018:00

Meeting of ACCS International steering committee

18:3021:30

Closing & Banquet (Pancific Ballroom, 2nd Floor)

4th Day: November, 15, 2017 8:0012:00 9:0012:00

Conference tour (Optional: A free tour (25-30 people) to Vietnam Museum of Ethnology (Please registration in advanced by sending Email to: [email protected] (Dr Dang Thi Thanh Le) Meeting and Discussion about International Collaboration

xiii

CONTENTS

No.

TITLES AND AUTHORS

Page

PART I: ABSTRACT KEYNOTE SPEECHES 1

1

Application of Nanocomposite Materials Modified Electrochemical Sensing of Biomolecules and Biosensors

Electrodes

in 3

Prof. Shen Ming Chen

2

Morphological, Compositional, and Heterostructural Design of Oxide Semiconductor Chemiresistors: New Challenges and New Opportunities

6

Prof. Jong Heun Lee 3

Layer-by-layer assemblies as key materials in biosensing and controlled release

7

Prof. Jun-ichi Anzai 9

INVITED TALKS

1

Adsorption/combustion-type micro VOC sensors —Effects of catalytic combustion activities of VOCs on their gas-sensing behavior

11

Takeo Hyodo, Takeru Hiura, Kazunori Nagae, Takahiko Sasahara, Kai Kamada, Taro Ueda and Yasuhiro Shimizu 2

Core-Shell Structured Nanomaterials for Sensitive Gas Sensors

13

Jae-Hun Kim, Ali Mirzaei, Jae-Hyoung Lee, Sang Sub Kim

3

Fully integrated electrochemical micro machined sensor based on silicon platforms

15

A. Morata, F. Baiutti, N. Alayo, I. Garbayo, F. Chiabrera, L. Fonseca, A. Tarancón, J. R.Morante

4

Low-temperature Operative Catalytic Combustion-type Hydrogen Gas Sensors Incorporating Cerium Oxide-Zirconium Oxide Based Catalysts Shinji Tamura, Shun Yasuhara, Ayaka Hosoya, Nobuhito Imanaka

xiv

17

5

Nanostructural Oxide Gas Sensors toward Room Temperature Operation

19

Nguyen Duc Chinh, Nguyen Minh Hieu, Chunjoong Kim, Dojin Kim

6

Noble Metal Sensitization of SnO2 and WO3 based Gas Sensors: How Does it Work

21

Nicolae Barsan, Udo Weimar 7

On the Possibility of LAPS as a Sensing Element in Microfluidic Devices

23

Tatsuo Yoshinobu 8

Rapid Disease Screening with a Diffusometric Immunosensor

25

Han-Sheng Chuang

9

Electrochemical and colorimetric biosensors for the assay of disease marker proteins with clinical applications

29

Prof. Genxi Li

10

Highly-sensitive, flexible electrochemical biosensor based on carbon nanotube thin film

31

Prof. Yutaka Ohno

11

Semiconductive Gas Sensors for Low-Concentrate Volatile Organic Compounds (VOCs)

33

Toshio Itoh, Ichiro Matsubara, Takafumi Akamatsu, Akihiro Tsuruta, and Woosuck Shin

12

Gas sensing properties of MEMS-type metal oxide gas sensor: Design of receptor function for pulse-heating mode

35

Kengo Shimanoe, Ken Watanabe, Koichi Suematsu Nanocarbon Film Based Sensors for Heavy Metal Detection 13

Osamu Niwa, Tatsuya Machida, Daiki Kato, Shunsuke Shiba, Tomoyuki Kamata, Dai Kato

37

Nanostructured heterojunctions for high performance chemoresistive gas sensors based metal oxides and 2-dimensional materials 14

39

Ho Won Jang

xv

15

Metal oxides nanowires for chemical sensors and Electronic Noses

41

V. Sberveglieri, E. Comini, D Zappa, V. Galstyan, G. Sberveglieri

16

A new route to the fabrication of heterogeneous metal oxide nanomaterial array for integrated chemical sensors

43

Inkyu Park

17

The Biomimetic Cell-based Biosensors for Applications in Biomedical and Environmental Detection

45

Ping Wang

18

A Cell-Based Chip Integrated with Microfluidic Control and Dissolved Oxygen Sensors for Estimation of Cellular Respiratory Activity

48

Ching-Chou Wu, Chieh-Jen Wang, Lee-Tian Chang 19

Battery-free Technology for Wireless Sensor Applications

50

Wan-Young Chung Biochar as a sensing material for gas sensors 20

21

Daniele Ziegler, Andrea Marchisio, Mauro Giorcelli, Pravin Jagdale, Alberto Tagliaferro, Jean-Marc Tulliani Flexible Gas Sensors Based on Zero- to Three-Dimensional Carbon Nanostructures

52

54

Chatchawal Wongchoosuk, Yotsarayuth Seekaew, Kriengkri Timsorn, Gun Chaloeipote 22

Printed Graphene Sensors: From research to commercialization

56

Adisorn Tuantranont Energy bandgap tuning of halide perovskites for optical-sensors 23

Young-Woo Heo, Se-Yun Kim, Sang-Wook Lee, Joon-Hyung Lee, JeongJoo Kim

58

Biochemical sensing with microstructured optical fibers 24

Linh Viet Nguyen, Stephen Warren-Smith, Kelly Hill, Erik Schartner, Heike Ebendorff-Heidepriem

xvi

60

25

Development of Fast and Highly Sensitive Interdigitated Capacitor Based Taste Sensor Array

62

Md. Rajibur Rahaman Khan, Shin-Won Kang Evaluation of VOC’s emitted from historic papers using a non-destructive approach: an electronic nose based on acoustic wave sensors 26

Marta I.S. Veríssimo, José A.F. Gamelas, Dmitry Evtyugin, M. Teresa S. R. Gomesa

65

Growth of Heterostructured Bi2O3–ZnO Photocatalyst and Its Enhanced 27

Photocatalytic Activity

67

Eadi Sunil Babu, Sengeragchaa, Bolortuya, Azimov Farkhod, Min Ji Hong, Yong Sik Kim, Hee Jun Kim, Young Hwa Woo, Sungjin Kim Fluorescence Polarization Measurement System for Multi-Sample Immunoassay 28

29

69

Manabu Tokeshi Mobile Robot Olfaction: Using Actively Generated Airflow to Enhance Chemical Reception

71

Hiroshi Ishida 30

CMOS-based Biomolecular Diagnosis Technologies

73

Chih-Ting Lin 31

Electrochemiluminescence biosensors for high sensitive medical diagnosis and rapid antioxidants detection Eiichi Tamiya Transistor Based Biosensors and its Applications

32 33

75

77

Chao Sung Lai How to get multiselectivity from resistive gas sensors based on nanostructured metal oxides

78

Matteo Tonezzer High performance gas sensors based on mesoporous semiconducting oxides 34

Geyu Lu, Yuan Gao, Yinglin Wang, Qiuyue Yang

xvii

80

Defect chemistry in ferroelectric materials 35

M. C. Martínez-Morales, F. Ambriz-Vargas, L. Lartundo-Rojas, J. OrtizLanderos and C. Gomez-Yanez

82

Ultrasensitive acetylcholine sensor based on the electron transfer promotion on electrochemically activated graphene electrodes 36

Vu Thi Thu, Nguyen Van Quynh, Dau Thi Ngoc Nga, Bui Quang Tien, Ly Cong Thanh, Dang Thi Thu Huyen, Vu Van Hung, Do Thi Thuy, Nguyen Thu Tuyet, Phan Van Thang, Nguyen Nguyet Minh, Bui Thi Thu, My Ngoc, Cao Thi Thanh, Nguyen Van Chuc, Tran Dai Lam

ORAL SECTION

83

85

Effect of Zinc Oxide Morphology on the Carbon Monoxide Sensing Properties 1

2

Ni Luh Wulan Septiani, Yusuke Yamauchi, Yusuf Valentino Kaneti, Brian Yuliartoa, Nugraha, Hermawan K Dipojono Photochemically Activated Indium-Gallium-Zinc Oxide for Flexible and RoomTemperature Operable Gas Sensors

87

88

Rawat Jaisutti and Yong-Hoon Kim High-performance NO2 sensor based on MoS2-modified reduced graphene oxide 3

4

Sen Liu, Ziying Wang, Tianyi Han, Teng Fei, and Tong Zhang Solid Electrolyte Impedancemetric NOx Sensor Using Zeolite Receptor

89

90

Youichi Shimizu, Hikaru Nakano, and Satoko Takase Gas Sensor Based on Fe-Doped ZnO nanorods for the detection of Volatile Organic gases (VOCs) at Room Temperature 5

6

Eadi Sunil Babu, Sengeragchaa, Bolortuya, Azimov Farkhod, Min Ji Hong, Yong Sik Kim, Hee Jun Kim, Young Hwa Woo, Sungjin Kim Humidity sensors based on stable polyelectrolytes

91

92

Teng Fei, Hongran Zhao, Jianxun Dai, Rongrong Qi, Tong Zhang Hydrothermal synthesis and gas sensing property of Zn2SnO4/SnO2 flower-like composite. 7

93

Xueli Yang, Peng Sun, Geyu Lu

xviii

8

The Fundamental Characteristics of WO3 Based Sensors

94

Anna Staerz, Udo Weimar, Nicolae Barsan

9

Poly(N-isopropylacrylamide) Nanoparticle−Based Gas Sensor Coating Prepared from Binary Aqueous Solutions

95

Masanobu Matsuguchi, Shinnosuke Fujii, Hajime Yagi Wearable and rapid gas sensing with microfabricated room temperature ionic liquid electrochemical sensors 10

11

96

Hao Wan, Heyu Yin, Sina Parsnejad, Andrew J. Mason Impedimetric Determination of Mercury(II) Based on Electrochemical DNA Biosensor

97

Ying Gan, Jiadi Sun, Jiawei Tu, Qiyong Sun, Ping Wang 12

Enzymatic synthesis of biosensor membrane

cellulose succinate as raw material of uric acid 98

Anna Roosdiana, Diah Mardiana, Ellya Indahyanti 3D FEM simulation of the effects of humidity sensing layer (ZnO) on response of SAW sensor based on ZnO/IDTs/AlN/Si structure 13

14

Hai-Ha Nguyen, Ngoc-Tuan Truong, Quang-Huy Do, Hoang-Nam Nguyen, Hang-Phuong Nguyen, Si-Hong Hoang The Impedimetric Bioaffinity Sensing Electrohydrodynamic Centripetal Vortex

Chip

Integrated

with

99

an 100

Ming-Jie Lin, Yan-Fu Liu, Ching-Chou Wu

15

Highly selective and sensitive ethanol sensor using urchin-like Mg-doped ZnO nanowire networks

101

Chang-Hoon Kwak, Hyung-Sik Woo, Jong-Heun Lee 16

Short-term drift compensation techniques based on chemical sensors array

102

Jin-Young Jeon, Jang-Sik Choi, Joon-Boo Yu, Hyung-Gi Byun Highly selective and sensitive benzene gas sensor using Pd-SnO2 yolk-shell micro-reactors with a catalytic Co3O4 overlayer 17

Seong-Yong Jeong, Ji-Wook Yoon, Tae-Hyung Kim, Hyun-Mook Jeong, Chul-Soon Lee, Yun Chan Kang, Jong-Heun Lee

xix

103

Two-dimensional NbS2 gas sensor for room temperature NO2 detection 18

Yeon Hoo Kim, Ki Chang Kwon, Seo Yun Park, Tae Hoon Kim, Junmin Suh, Ho Won Jang

104

Iron oxide - carbon nanotube composite structure for room temperature ammonia gas sensor 19

20

Nguyen Minh Hieu, Truong Thi Hien, Nguyen Duc Chinh, Nguyen Duc Quang, Cao Van Phuoc, Chungjoong Kim, Dojin Kim Knittable and wearable gas sensors using reduced graphene oxide covered carbon fabrics decorated with metal catalysts for enhanced selectivity

105

106

Chung won Lee, Jun Min Suh, Ho Won Jang

21

Tailoring Chemically Converted Graphenes Using a Water-soluble Pyrene Derivative with a Zwitterionic Arm for Sensitive Electrochemiluminescencebased Analyses

107

Jihye Kwon, Seo Kyoung Park, Yongwoon Lee, Je Seung Lee, Joohoon Kim

22

Highly sensitive H2S gas sensors based on Pd-doped CuO nanoflowers with low operating temperature

108

Xiaobing Hu, Zhigang Zhu, Yihua Wu, Lijun Cai 23

Utilization of a Solid Electrolyte CO2 Sensor for the Performance Evaluation of CO2 Capture Materials

109

Ayaka Yamamoto, Armand Quitain, Mitsuru Sasaki, and Tetsuya Kida Solid electrolyte gas sensor using proton conductive graphene oxide 24

25

Yuta Kuwaki, Azumi Miyamoto, Armando T. Quitain, Mitsuru Sasaki, Tetsuya Kida Fabrication of well-ordered porous array mounted with gold nanoparticles and enhanced sensitivities for mixed potential-type zirconia-based NH3 sensor

110

111

Bin Wang, Xishuang Liang, GeyuLu

26

The Design of Module e-Nose Combining with Pattern Recognition for Lung Cancer Screening

112

Xusheng Zhang, Fan Gao, Xi Zhang, Jiajing Sheng, Ping Wang 27

Surface Functionalization of Gold Surfaces with Polypeptide: A Low-Fouling Zwitterionic Surface for Detecting Placenta Growth Factor W.E. Hsu, C.H. Yang, C.C. Chang, S.C Wei, C.W. Lin

xx

113

28

Detection of triethylamine with fast response by Al2O3/α-Fe2O3 composite nanofibers

114

Lanlan Guo, Yanfeng Sun, Geyu Lu 29

Organophosphate Pesticides Determination by 3D µPADs and ePADs

115

Hua Quoc Trung, Daniel Citterio Breath Control in Respiratory Air and Simultaneous Analysis of Sensor Data 30 31

116

Rolf Seifert, Thorsten Conrad, Jens Peter, Hubert Keller Development of a rapid and sensitive biosensor for biological toxins

117

Hui-Pin Cheng, Han-Sheng Chuang

32

Plasmonic Resonance Modes and SERS Performance of Out-of-plane Silver Vshape Substrates

118

Jianghao Li, Yihang Fan, Xiaotian Xue and Zhengjun Zhang Enzymatic Flexible Arrayed Urea Biosensor Based on GO/TiO2 Films Modified by Magnetic Beads 33

34

Cian-Yi Wu, Jung-Chuan Chou, Yi-Hung Liao, Chih-Hsien Lai, Siao-Jie Yan, You-Xiang Wu, and Hong-Yu Huang Determination of Nitrate Ions in Potable Water Using a Miniaturized Electrochemical Sensor

119

120

Yang Li, Yu Song, Jianhua Tong, Chao Bian, Jizhou Sun, Shanhong Xia Liquid-junction-free reference electrode system for amperometry using a closed bipolar electrode 35

36

Kumi Y. Inoue, Miho Ikegawa, Takahiro Ito-Sasaki, Shinichiro Takano, Hitoshi Shiku, Tomokazu Matsue The potency of Fe3O4 / MWCNT nanocomposite synthesized from local iron sand for electrochemical biosensor

121

122

Retno Rahmawati, Ahmad Taufiq, Sunaryono, Yusuke Yamauchi, Yusuf Valentino Kaneti, Brian Yuliarto, Suyatman, Nugraha, Deddy Kurniadi 37

Nata de Coco Membrane on Screen Printed Potentiometric Phenol Sensors Ani Mulyasuryani, Afifah Muhimatul Mustaghfiroh

xxi

123

38

Highly sensitive and selective NO2 gas sensors using multi-shelled WO3 yolkshell structures

124

Jun-Sik Kim, Ji-Wook Yoon, Yun Chan Kang, Jong-Heun Lee Potentiometric Ascorbic Acid Determination by MBs-Ascorbate Oxidase/GO/IGZO/Al Membrane Assembled on Flexible Sensor Array 39

40

You-Xiang Wu, Jung-Chuan Choua,, Yi-Hung Liao, Chih-Hsien Lai, SiaoJie Yan, and Cian-Yi Wu Design of Ag Nanorods for SERS with Sensitivity and Thermal Stability

125

126

Lingwei Ma, Zhengjun Zhang, and Hanchen Huang 41

Quantitative analysis of chemicals in unknown system by surface-enhanced Raman scattering spectroscopy at trace level

127

Sumeng Zou, Lingwei Ma, Jianghao Li, Zhengjun Zhang 42

A study of deformed TiO2 aggregates - graphene nanocomposites as photoanode for dye-sensitized solar cell

129

Hsueh-Tao Chou, Cheng-Yueh Chen, Ho-Chun Hsu 43

Myotube cell-based sensing of insulin analogs with a SPR imaging system

130

Yuki Shiraishi, Hiroaki Shinoharaa, Minoru Suga

44

On the dynamics of photo-generated carriers in Si-Ge quantum dots Ngo Ngoc Ha

131

Spatial Selective Surface Functionalization of Surface Plasmon Resonance Biosensor via Thiol-Ene Click reaction 45

46

Yi-Ming Chen, Tzu-Heng Wu, Hui-Wen Liu, Ya-Ting Tsai, Hsien-Yeh Chen, Chii-Wann Lin Rigidly tethered bis-phosphoric acids: Novel probes for the detection of ferric ions by fluorescence and CD-spectroscopy

132

133

Jochen Niemeyer, Frescilia Octa-Smolin Volatile imaging system “Sniff-cam” using alcohol dehydrogenase for ethanol and acetaldehyde after drinking 47

Kenta Iitani, Munire Naisierding, Yuuki Hayakawa, Koji Toma, Takahiro Arakawa, Kohji Mitsubayashi

xxii

134

VOC-sensing properties of YSZ-based mixed-potential type gas sensors: Effects of fabrication methods and microstructure of Au-based electrodes 48

Satoshi Ono, Taro Ueda, Takayuki Suzuki, Kai Kamada, Takeo Hyodo,

135

Yasuhiro Shimizu Analysis of Oxygen Adsorption on Surface of Metal Oxide to Understand Sensing Mechanism of Semiconductor Gas Sensors. 49

Koichi Suematsu, Sun Yongjiao, Ken Watanabe, Maiko Nishibori, Kengo Shimanoe

136

Fast response and reliable humidity sensors based on rGO/TiO2 hybrid composites 50

Seo Yun Park, Seung-Pyo Hong, Yeon Hoo Kim, Jun Min Suh, Tae Hoon Kim, Ho Won Jang

137

Gas Sensing Characteristics of metal-doped Tungsten Oxide prepared from (NH4)2WS4 precursor 51

Tae Hoon Kim, Amirhossein Hasani, Yeon Hoo Kim, Jun Min Suh, Seo Yun Park, Soo Young Kim, Ho Won Jang

138

A Novel Monolithic Phase sensitive Surface Plasmon Resonace Biosensor 52

Tzu-Heng Wu，Zu-Yi Wang，Julien Vaillant，Hui-Yun Luo Aurelien Bryant, Chii-Wann Lin

139

Nickel Oxide Decorated Cobalt Oxide Nanorods for Enhanced Benzene Selectivity 53

Jun Min Suh, Young-Seok Shim, Woonbae Sohn, Taemin L. Kim, Ho Won Janga

140

Development of Electrochemical Sensing System for the Detection of Domoic Acid 54

Hafiza Mohamed Zuki, Norhidayah Mohd Nasri, Fatin Nabilah Muhamad, Azrilawani Ahmad, Marinah Mohd Ariffin

141

Solution-processed metal sulfides for room-temperature NO2 detection 55

Hao Kan, Min Li, Baohui Zhang, Jingyao Liu, Shuqin Yang, Zhixiang Hu, Huan Liu

142

QCM-based humidity sensors and sensing properties employing colloidal SnO2 nanocrystals 56

Naibo Gao, Shengming Cheng, Zhaokun Jing, Zhilong Song,Shuqin Yang, Qian Liu, Wenkai Zhang, Hao Kan, Huan Liu

xxiii

143

57

Highly sensitive H2S gas sensors based on Pd-doped CuO nanoflowers with low operating temperature

144

Xiaobing Hu, Zhigang Zhu, Yihua Wu, Lijun Cai 58

Improving efficiency and stability of polymer solar cells via addition of n-type macromolecular additive

145

Changduk Yang 59

Array of Precise Cell-pairs Based on Positive Dielectrophoresis

146

Tomoyuki Yasukawa, Fumio Mizutani Electrochemical Bridging of Conducting Polymers at the Percolation Threshold for Chemiresistors 60

61

Krishnan Murugappan, Tabitha Jones, Merel Lefferts, Ben Armitage, Martin R. Castell Investigation of wireless potentiometric glucose biosensor sensing system based on ruthenium dioxide membrane used for homecare

147

148

Yi-Hung Liao

62

Electrochemical Insulin Sensor Utilizing a DNA Aptamer-Immobilized Electrode

149

Izumi Kubo, Taiga Eguchi Development of a Sensitivity-Enhanced Surface Plasmon Resonance Aptasensor for the Detection of Arsenic 63

64

L.T. Fan, C.H. Yang, C.C. Chang, T.L. Chuang, J.S. Lai, W.S. Lin, C.W. Lin Electrochemical Properties of Miniature Gas Sensors using Semi-Solid Electrolytes

150

151

Dong-Yun Lee, Hana Cho, Min-Ho Kang, Sang-Do Han, Kie-Won Lee

65

Photoelectric Characteristics of Au Nanoparticles Modified ZnO Nanorods Composite Films on ITO Glass

152

Hsueh-Tao Chou, You-Lun Deng, Wei-Hao Huang, Yi-Keng Yu, Ho-Chun Hsu. Cr2O3/ZnCr2O4 hetero-nanostructures for ultraselective and sensitive detection of xylene 66

Jae-Hyeok Kim, Hyun-Mook Jeong, Chan Woong Na, Ji-Won Yoon, JongHeun Lee

xxiv

153

POSTER SECTION

155

Hydrothermal synthesis of CuO nanoplates and their gas sensing characteristics 1

2

Ngo Thi Ut, Dang Thi Thanh Le, Nguyen Duc Hoa P-N Sensing Response of SnS2-SnO2 Nanoflowers Exposed to NH3 Gas

157

158

Di Liu, Zilong Tang, Yesheng Li, Zhongtai Zhang 3

Buffered-oxide-etchant Post-treated silicon Nanowire Network for Enhanced Hydrogen Sensing Performance.

159

Min Gao, Inkyu Park 4

CO2 sensing properties of Zr-added CaFe2O4-based sensor

160

Yuki Obukuro, Keisuke Mizuta, Kenji Obata, Shigenori Matsushima 5

Quick detection of IgA for mobile stress monitoring

161

Takeshi Ito, Takeshi Nanushigawa, Tomohiro Shimizu, Shoso Shingubara 6

Chemometric analysis of sensory data obtained with an electronic nose Marta I.S. Veríssimo, João A.B.P. Oliveira, M. Teresa S.R.Gomes

162

Fabrication of electrochemical electrodes based on platinum and ZnO nanofibers for biosensing applications 7

Nguyen Thi Hong Phuoc, Nguyen Van Hoang, Dang Thi Thanh Le, Matteo Tonezzer, Tran Quang Huy, Nguyen Van Hieu

163

Adsorption Behavior of H2O, OH and H to Sr–Ca–Cu–O Superconducting Materials 8

9

Akira Fujimoto, Satoshi Shinoda, Tadachika Nakayama and Hisayuki Suematsu Effect of other atoms on CO2 sensing properties of CaFe2O4

164

166

Kenji Obata, Keisuke Mizuta, Yuki Obukuro, Shigenori Matsushima 10

One-pot hydrothermal synthesis of rGO/WO3 nanocomposites

167

Do Quang Dat, Chu Manh Hung, Nguyen Duc Hoa 11

VO2 nanostructures for temperature sensing applications Amir Abidov, Sungjin Kim

xxv

168

12

Primitive Study of Dual Biosensor Coupling with Localized Surface Plasmon Resonance and QCM-D Using Anodic Aluminum Oxide Substrate

169

H. Terasawa, T. Shimizu, S. Shingubara, T. Ito Keratin modified carbon paste electrode for arsenic detection 13

14

Hannah C. Valencia, Marivic S. Lacsamana, Milagros M. Peralta, Veronica C. Sabularse Design of Gold Nanoband Sensor for Determination of Mercury Ion in Water

170

171

Jiawei Tu, Qiyong Sun, Ying Gan, Tao Liang, Qiongwen Hu, Ping Wang

15

Characteristics of Counter Electrode Modified by Reduced Graphene Oxide for Dye-sensitized Solar Cell

172

Chung-Ming Yang, Jung-Chuan Choua, Yi-Hung Liao, Chih-Hsien Lai, Wan-Yu Hsu, Pei-Hong You

16

Enhanced-electrochemiluminescence of Ru(bpy)32+ with Mn:ZnSe Quantum Dots

173

Suphawuth Siriket, Sirirat Phaisansuthichol, and Sakchai Satienperakul

17

Heterojunction of SnO2 nanowire mat and MWCT film for room temperature gas sensors

174

Quan Thi Minh Nguyet, Nguyen Van Duy, Nguyen Duc Hoa, Dang Thi Thanh Le, Nguyen Van Hieu

18

Aptamer - conjugated multifunctional nanoparticles: A promising tool for fast detection and collection of cancer cells

175

Chu Tien Dung, Nguyen Thi Thuy Ha, Tran Thi Hong, Nguyen Hoang Nam

19

Effect of Ca2+ and V5+ substitution on the atomic structure, microstructure and oxidation state of YIG nanoparticles

176

Vu Thi Hoai Huong, To Thanh Loan, Dao Thi Thuy Nguyet, Nguyen Phuc Duong Synthesis and Photocatalytic Activity of (N, Ta) Co-doped TiO2 Nanopowders 20

177 Vu Duy Thinh, Ngo Thi Hong Le

xxvi

21

Fabrication of SnO2 (n)–SnO (p) Core-Shell Nanowires on the Copper Foil by Thermal Evaporation Process

178

Pham Tien Hung, Sang-Wook Lee, Joon-Hyung Lee, Jeong-Joo Kim, Young-Woo Heo

22

An Electrical Assay for Protein Kinase A Based on Carbon Nanotube FieldEffect Transistor

179

Chang-Seuk Lee, Su Hwan Yu, Sujeong Hong, Sujin Shim, Tae Hyun Kim Method Development and Validation for the Determination of Inorganic Arsenic using Differential Pulse Anodic Stripping Voltammetry (DPASV) 23

24

Maritess L. Magalona, Milagros M. Peralta, Marivic S. Lacsamana, Veronica C. Sabularse, Constancio C. de Guzman, Stephanie Britania, Ma. Theresa Glenn Bea Manguiat Measurement of saltiness concentration and intensity using saltiness sensor and ISE

180

181

Y. Kaneda, Y. Muto, Y. Tahara, H. Ikezaki, H. Sano, K. Toko

25

The Characteristic of ZnO:(Al,P) Thin Films with ZnO Buffer Layer by the RFMagnetron Sputtering.

182

Seunghak Shin, Sangwook Lee, Joon-Hyung Lee, Young-Woo Heo, JeongJoo Kim Organic FET Based BioFETs towards Stress Monitoring 26

27

Shin-ichi Wakida, Tsuyoshi Minami, Tsukuru Minamiki, Yui Sasaki, Ryoji Kurita, Osamu Niwa, Shizuo Tokito Preparation and Characterization of Electrospun Poly(vinyl Alcohol)/Salicylic Acid-Modified Chitosan Microfibers as a Modifier for Carbon Paste Electrode in the Detection of Arsenic by Stripping Voltammetry

183

184

Maris Asuncion L. Bayhon, Milagros M. Peralta, Marivic S. Lacsamana, Jose Rene L. Micor Electrochemical detection of Sudan I using nickel nanoparticles decorated graphene oxide modified screen printed carbon electrode 28

Nguyen Truong Anh, Luong Thi Thuy Dung, Nguyen Xuan Hoan, Nguyen Xuan Viet

xxvii

185

H2S Gas Sensor Based on Ru-MoO3 Thick Film 29

30

Ungkana Inpan, Viruntachar Kruefu, Anurat Wisitsoraat, Sukon Phanichphant Sensing for cardiac differentiation of model stem cells with a surface plasmon resonance (SPR) imager

186

187

Shiori Kawashima, Hiroaki Shinohara, Yuki Shiraishi, Minoru Suga 31

Hydrothermal synthesis of nanostructured MoS2 and its electrochemical properties

188

Truong Cong Dinh, Vy Anh Vuong, Chu Manh Hung, Nguyen Duc Hoa 32

Flexible Piezopolymer Pressure Sensor for Structural Health Monitoring

189

Toan Thanh Dao

33

Development of Multichannel Highly Sensitive Interdigitated Capacitor Based Glucose Biosensor

190

Md. Rajibur Rahaman Khan, Sae-Wan Kim, Shin-Won Kang

34

Analysis of Counter Electrode Modified by Reduced Graphene Oxide and Black Phosphorus with IGZO/TiO2 Photoelectrode for Dye-sensitized Solar Cell

192

Chang-Yi Wu, Jung-Chuan Choua, Yi-Hung Liao, Chih-Hsien Lai, ChangChia Lu and Pei-Hong You Investigation of the Temperature Effect for the Chlorine Ion Sensor 35

Tong-Yu Wua, Shi-Chang Tseng, Jung-Chuan Chou, Yi-Hung Liao, ChihHsien Lai, Siao-Jie Yan, You-Xiang Wu, Cian-Yi Wuand Ting-Wei Tseng

193

Exhalation analysis of diabetic patients using e-nose system 36

37

Joon-Boo Yu, Byoung Kuk Jang, Chong-Yun Kang, Hae-Ryong Lee, Hyung-Gi Byun Development of Polyaniline-Coated Cotton Yarn for Wearable Ammonia Gas Sensor

194

195

Naraporn Indarit, Nattasamon Petchsang, Rawat Jaisutti 38

Template-free Synthesis and Gas Sensing Property of Indium-doped Zinc Oxide Nanoflowers Siriprapa Khemthong, Kithipong Thana, Rawat Jaisutti

xxviii

196

39

Chemical Sensor based on Indium-Gallium-Zinc Oxide/Cobalt Phthalocyanine Heterojunctions

197

Kittiphong Thana, Yong-Hoon Kim, Rawat Jaisutti

40

Study on the change of properties and morphology of polyoxymethylene/nanosilica composites according to accelerated weather testing

198

Tran Thi Mai, Nguyen Thuy Chinh, Vu Viet Thang, Nguyen Thi Thu Trang, Dang Thi Thanh Le, Thai Hoang 41

Alizarin Red S-Modified Film-Coated Electrodes for Biosensing

199

Daichi Minaki, Jun-ichi Anzai

42

VOC Gas Sensor Fabrication and Characteristics Based on Au doped ZnO Thin Film by Ion Beam Sputter

200

Sang-Do Han, Hana Cho, Min-Ho Kang, Dong-Yun Lee, Kie-Won Lee 43

UV-light-activated TiO2 thin film for H2S sensing at room temperature

201

Nguyen Duc Chinh, Chunjoong Kim, Dojin Kim Electronic nose based on temperature modulated response of bi-layer Pt/SnO2 44

thin film multi-sensor array toward environmental monitoring

202

Nguyen Xuan Thai, Nguyen Van Duy, Nguyen Duc Hoa, Nguyen Van Hieu

45

Development of a Sensitivity-Enhanced Surface Plasmon Resonance Aptasensor for the Detection of Arsenic

203

L.T. Fan, C.H. Yang, C.C. Chang, T.L. Chuang, J.S. Lai, W.S. Lin, C.W. Lin

46

Electrochemical Gas Sensor Employing Quasi Solid-State Polymer Electrolyte with High Conductivity

204

Sang-Hyung Kim, Seung Hark Park, Dong-Yun Lee, Sang-Do Han, JinSeong Park, Dong-Won Kim A Novel Monolithic Phase sensitive Surface Plasmon Resonace Biosensor 47

Tzu-Heng Wu，Zu-Yi Wang，Julien Vaillant，Hui-Yun Luo，Aurelien Bryant, Chii-Wann Lin

xxix

205

48

Enhanced ammonia sensing based on vapour phase polymerisation of PANi/PPy/TiO2 hybrid nanocomposite

206

Chu Van Tuan, Hoang Thi Hien, Ho Truong Giang, Tran Trung 49

On the dynamics of photo-generated carriers in Si-Ge quantum dots

207

Ngo Ngoc Ha

50

Unravelling the nanostructures of supramolecular assemblies of intermolecular bonding of hydroxyquinolines on Au (111)

208

Thu-Hien Vu, Thomas Wandlowski

51

An Au-TiO2-Ti Structure Based Schottky Barrier Surface Plasmon Resonance Sensor Enables Miniaturization of SPR Sensing System

209

Chao Wang, Chen-Hsuan Hsia, Jian-Hong Yang, Chii-Wann Lin

52

Surface Functionalization of Gold Surfaces with Polypeptide: A Low-Fouling Zwitterionic Surface for Detecting Placenta Growth Factor

210

W.E. Hsu, C.H. Yang, C.C. Chang, S.C Wei, C.W. Lin

53

Spatial Selective Surface Functionalization of Surface Plasmon Resonance Biosensor via Thiol-Ene Click reaction

211

Yi-Ming Chen, Tzu-Heng Wu, Hui-Wen Liu, Ya-Ting Tsai, Hsien-Yeh Chen, Chii-Wann Lin 54

55

Gas-Sensing Performance Study of Indium Oxide Material Chen Yang, Xie LiLi, Zhu ZhiGang Facile synthesis of MnFe2O4/graphene nanocomposite and its application for electrcatalytic oxidation of hydrogen peroxide

212

213

Xueling Zhao, Cheng Chen, Zhanhong Li, Yihua Wu, Zhigang Zhu

56

A Study on measuring dissolved H2 gas in transformer oil using the SnO2 thin film resistive sensor sensitized with Pd islands

214

Hoang Si Hong, Hoang Van Phuoc, Nguyen Van Dua, Nguyen Thi Lan Huong, Nguyen Thi Hue, Nguyen Van Hieu, Nguyen Van Toan

57

P-type semiconducting NiO nanoannulars: synthesis and application for gas sensors Pham Long Quang, Tran Thai Hoa, Hoang Thai Long, Nguyen Duc Cuong

xxx

216

58

Nanosphere Lithography for Fabrication of Downscaled Nanoporous Biosensor

217

Agnes Purwidyantri, Chao-Sung Lai

59

The Research on Photovoltaic Performances of Dye-sensitized Solar Cell by Appling TiO2-Reduced Graphene Oxide - IGZO Photoelectrode

218

Chien-Hung Kuo, Jung-Chuan Chou, Yi-Hung Liao, Chih-Hsien Lai, PeiHong You, Chang-Chia Lu

60

Self-heating H2S gas sensor using a network of SnO2 nanowires functionalized with Ag

219

Trinh Minh Ngoc, Chu Manh Hung, Nguyen Ngoc Trung, Nguyen Duc Hoa, Nguyen Van Duy, Nguyen Van Hieu Low Resistance, Energy Band-Aligned 0D/2D PbS/MoS2 Hybrid Gas Sensors 61

Jingyao Liu, Zhilong Song, Zhixiang Hu, Shuqin Yang, Naibo Gao, Qian Liu, Wenkai Zhang, Hao Kan, Huan Liu

220

H2S-Sensing Properties and Mechanism of Nanocrystalline WO3 Films 62

Zhixiang Hu, Haoxiong Yu, Zhilong Song, Jingyao Liu, Shuqin Yang, Huan Liu

221

H2S sensing properties of α-Fe2O3 nanofibers fabricated by electrospinning method 63

64

Nguyen Van Hoang, Phan Hong Phuoc, Nguyen Van Dung, Nguyen Duc Hoa, Nguyen Van Duy, Dang Thi Thanh Le, Chu Manh Hung, Nguyen Van Hieu Flexible hydrogen gas sensor based on Pt-SnO2 thin film Sputtered on polyimide substrate

222

223

Vo Thanh Duoc, Nguyen Xuan Thai, Nguyen Van Duy, Nguyen Van Hieu

65

Controlling of the diameter and density of silicon nanowires prepared by silver metal-assisted chemical etching

224

Le Thanh Cong, Nguyen Thi Ngoc Lam, Nguyen Truong Giang, Nguyen Duc Dung, Ngo Ngoc Ha 66

Electrochemical behaviors of Fe2O3 inside carbon nanotubes in alkaline solution Bui Thi Hang, Vu Manh Thuan, Doan Ha Thang

xxxi

225

Co-implanted electrospun ZnO nanostructure sensor for superior detection of NO2 gas 67

68

Le Thi Hong, Nguyen Van Hoang, Nguyen The Nghia, Nguyen Van Duy, Nguyen Duc Hoa, Chu Manh Hung, Nguyen Van Hieu Controlled growth of indium oxide nanowires for gas sensing applications

226

227

Dang Ngoc Son, Nguyen Van Duy, Le Xuan Thanh, Nguyen Duc Hoa

69

Carbon monoxide sensing of Pd nanoparticles functionalized on the surface of hydrothermally synthesized WO3 nanorods

228

Pham Van Tong, Nguyen Thi Hanh, Do Thi Thu Hanh, Luu Hoang Minh, Nguyen Duc Hoa

70

Strong effect of ZnO nano-structures on response/recovery times to room temperature NO2 gas sensing under UV assistance

229

Do Thi Anh Thu, Do Thi Thu, Hoang Thi Hien, Pham Quang Ngan, Giang Hong Thai, Chu Van Tuan, Ho Truong Giang,Tran Trung

71

Growth of SnO nanoplates at low temperature by chemical vapour deposition method for gas sensor application

230

Pham Tien Hung, Sang-Wook Lee, Joon-Hyung Lee, Jeong-Joo Kim, Young-Woo Heo

72

Nano-film aluminum-gold for ultra-high dynamic range surface plasmon resonance chemical sensor

231

Briliant Adhi Prabowo, Kou-Chen Liu

73

A highly sensitive and selective impedimetric sensor based on surface molecularly imprinted polymer (MIP) film coated gold nanoparticles for fluoroquinolone antibiotic detection

232

Phi Van Toan, Nguyen Quoc Hao, Nguyen Vu Quynh, Hoang Trung Anh, Truong TN Lien

74

Development of an impedimetric immunobiosensor for alpha-fetoprotein detection based on disposable screen-printed carbon ink electrode Tram Do Thi Ngoc, Lien Truong Thi Ngoc

xxxii

234

75

Electrochemical behaviours of ZnO nanowires grown on-chip for biosensing applications

235

Nguyen Thi Hong Phuoc, Nguyen Van Toan, Matteo Tonezzer, Vo Thanh Duoc, Dang Thi Thanh Le

76

CO Gas Sensor Based on Quartz Crustal Microbalance Coated with Iron Oxide Nanorods via Co-precipitation Method

236

Nguyen Thanh Vinh, Nguyen Duc Hoang, Vu Thu Trang, Ngo Xuan Dinh, Nguyen Van Quy

PART II: FULL PAPER

237

A Study of Deformed TiO2 Aggregates - Graphene Nanocomposites as Photoanode for Dye Sensitized Solar Cell 1 Hsueh-Tao Chou, Cheng-Yueh Chen, Chun-Hsin Wang, Ho-Chun Hsu, Jing-Hua Lu

239

Investigation of the Temperature Effect for the Chloride Ion Sensor 2

Tong-Yu Wu, Shi-Chang Tseng, Jung-Chuan Chou, Yi-Hung Lia, ChihHsien Lai, Siao-Jie Yan, You-Xiang Wu, Cian-Yi Wu, Ting-Wei Tseng

244

3D FEM simulation of the effects of humidity on response of SAW sensor based on ZnO/IDTs/AlN/Si structure 3 Hai-Ha Nguyen, Ngoc-Tuan Truong, Quang-Huy Do, Hoang-Nam Nguyen, Hang-Phuong Nguyen, Si-Hong Hoang

4

248

Potentiometric Ascorbic Acid Determination by MBs-Ascorbate Oxidase/GO/IGZO/Al Membrane Assembled on Flexible Sensor Array You-Xiang Wu, Jung-Chuan Chou, Yi-Hung Liao, Chih-Hsien Lai, Siao-Jie Yan, Cian-Yi Wu

253

A Cell-Based Chip Integrated with Microfluidic Control and Dissolved Oxygen Sensors for Estimation of Cellular Respiratory Activity 5

Ching-Chou Wu, Chieh-Jen Wang, Lee-Tian Chang

xxxiii

259

Adsorption Behavior of H2O, OH and H to Sr-Ca-Cu-O Superconducting Materials 6 Akira Fujimoto, Satoshi Shinoda, Tadachika Nakayama, Hisayuki Suematsu

7

An Au-TiO2-Ti Structure Based Schottky Barrier Surface Plasmon Resonance Sensor Enables Miniaturization of SPR Sensing System

263

267

Chao Wang, Chen-Hsuan Hsia, Jian-Hong Yang, Chii-Wann Lin CO2 sensing properties of Zr-added CaFe2O4-based sensor 8 Yuki Obukuro, Keisuke Mizuta, Kenji Obata, Shigenori Matsushima

9

Study of interaction between Japanese Encephalitis Visus antigens and IgG antibody on basis of nanocomposite polyanilne/multi walled carbon nanotubes/ manganese dioxide

271

275

Chu Van Tuan, Hoang Thi Hien, Tran Trung Study on the ability to measure dissolved H2 gas in transformer oil using resistive sensor based on SnO2 thin film sensitized with microsized Pd islands 10 Nguyen Thi Hue, Nguyen Van Dua, Hoang Van Phuoc, Nguyen Thi Lan Huong, Nguyen Van Toan, Hoang Si Hong

11

280

Effect of nanosilica content and accelerated weather testing on some properties and morphology of Polyoxymethylene/silica nanocomposites Tran Thi Mai, Nguyen Thi Thu Trang, Nguyen Thuy Chinh, Dang Thi Thanh Le, Thai Hoang

285

Characteristics of Counter Electrode Modified by Reduced Graphene Oxide for Dye-sensitized Solar Cell 12

Chung-Ming Yang, Jung-Chuan Chou, Yi-Hung Liao, Chih-Hsien Lai, Chien-Hung Kuo Wan-Yu Hsu, Pei-Hong You

293

Analysis of Counter Electrode Modified by Reduced Graphene Oxide and Black Phosphorus with IGZO/TiO2 Photoelectrode for Dye-sensitized Solar Cell 13

Chang-Yi Wu, Jung-Chuan Chou, Yi-Hung Liao, Chih-Hsien Lai, Chien Hung Kuo, Chang-Chia Lu, Pei-Hong You

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Enzymatic Flexible Arrayed Urea Biosensor Based on GO/TiO2 Films Modified by Magnetic Beads 14

Cian-Yi Wu, Jung-Chuan Chou, Yi-Hung Liao, Chih-Hsien Lai, Siao-Jie Yan, You-Xiang Wu, Hong-Yu Huang

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An Investigation on Applying Indium Gallium Zinc Oxide and Reduced Graphene Oxide to Photoelectrode for Dye-sensitized Solar Cells 15

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Chien-Hung Kuo, Jung-Chuan Chou, Yi-Hung Liao, Chih-Hsien Lai, PeiHong You Effect of other atoms on CO2 sensing properties of CaFe2O4 Kenji Obata, Keisuke Mizuta, Yuki obukuro, Shigenori Matsushima

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Electrochemical Properties of Miniature Gas Sensors Using Semi-SolidElectrolyte Hana Cho, Min-Ho Kang, Dong-Yun Lee, Sang-Do Han, Kie-Won Lee

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Electrochemical behaviors of Fe2O3 inside carbon nanotubes in alkaline solution 18

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Bui Thi Hang, Doan Ha Thang Controlling of the diameter and density of silicon nanowires prepared by silver metal-assisted chemical etching

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Le Thanh Cong, Nguyen Thi Ngoc Lam, Nguyen Truong Giang, Nguyen Duc Dung, Ngo Ngoc Ha

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Electrochemical behaviours of ZnO nanowires grown on-chip for biosensing applications 20

Nguyen Thi Hong Phuoc, Nguyen Van Toan, Matteo Tonezzer, Vo Thanh Duoc, Dang Thi Thanh Le

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Enhancement of Ammonia gas sensor based on SnO2/Pd bi-layer thin film 21

Nguyen Xuan Thai, Chu Manh Hung, Nguyen Duc Hoa, Nguyen Van Toan, Nguyen Van Hieu, Nguyen Van Duy Carbon monoxide sensing of Pd nanoparticles on the surface of hydrothermally synthesized WO3 nanorods

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Pham Van Tong, Nguyen Thi Hanh, Do Thi Thu Hanh, Luu Hoang Minh, Nguyen Duc Hoa

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Investigating NO2 sensing capabilities of the electrospun α-Fe2O3 nanofibersbased sensors 23

Nguyen Van Hoang, Phan Hong Phuoc, Chu Manh Hung, Nguyen Van Hieu Unravelling the nanostructures of supramolecular assemblies of intermolecular bonding of Phenylboronic acid on Au(111) single crystal

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Pham Duc Thanh, Ngoc Son Nguyen, and Thu-Hien Vu

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H2S Sensing Characteristics of Self-heated Ag-coated SnO2 nanowires 25

Trinh Minh Ngoc, Hugo Nguyen, Chu Manh Hung, Nguyen Ngoc Trung, Nguyen Van Duy

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Synthesis and Photocatalytic Activity of (N, Ta) Co-doped TiO2 Nanopowders 26

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Vu Duy Thinh, Ngo Thi Hong Le

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Development of Polyaniline-Coated Cotton Yarn for Wearable Ammonia Gas Sensor Naraporn Indarit, Nattasamon Petchsang, Rawat Jaisutti

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The 12th Asian Conference on Chemical Sensors (ACCS2017)

12-15 November, 2017, Hanoi, Vietnam

Keynote Speeches

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The 12th Asian Conference on Chemical Sensors (ACCS2017)

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The 12th Asian Conference on Chemical Sensors (ACCS2017)

12-15 November, 2017, Hanoi, Vietnam

Keynote Speaker Professor: Shen-Ming Chen PhD. in Chemistry, Distinguished Professor Department of Chemical Engineering and Biotechnology National Taipei University of Technology No. 1, section 3, Chung-Hsiao East Road Taipei, Taiwan 106 (ROC) Email: [email protected] Tel: +886 2270 17147, Fax: +886 2270 25238 Educational background 6/1991 PhD in chemistry from National Taiwan University, Taipei, Taiwan 6/1983 Master in chemistry from National Taiwan University, Taipei, Taiwan. Professional Experiences 2/2010-present 8/2013-present 8/2000-7/2006 8/1997-1/2010 8/1991-7/1997 8/1995-7/2000 1997 8/2012-7/2014 8/2010-7/2012 6/2015-present 1/2015- present 8/2013- present 8/2014-7/2016 7/2016-present

Distinguised Professor, National Taipei University of Technology, Taiwan. Chairperson, EOMP , National Taipei University of Technology, Taiwan. Dean (Curator) of library, National Taipei University of Technology, Taiwan. Professor, National Taipei University of Technology, Taiwan. Associate Professor, National Taipei Institute of Technology, Taiwan. Director of Extracurricular Activity, National Taipei University of Technology, Taiwan Visiting professor, Institute of Inorganic Chemistry, Friedrich-Alexander University Erlangen-Nuremberg, Germany President, Taiwan Chemical Sensors Technology Association Vice President, Taiwan Chemical Sensors Technology Association MOST Chemical Center to promote chemical sensing group - Convenor Ministry of Education, Taiwan. Academic adviser(consultant) Taiwan Electrochemical Society - executive director Taiwan Science and Technology Association of Chemical Sensors Supervisor Taiwan Science and Technology Association of Chemical Sensors Executive director

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Field of Research His research interest includes electrochemical sensors, biosensors, nanocomposites, enviromental electrochemical sensors , energy storage applications, electroanalytical chemistry, electrocatalysis, electroanalysis, photoelectrochemistry, bionanomaterials, bionanotechnology, bioelectrochemistry,, chemical materials, metalloproteins, metalloporphyrins, nanotechnology, spectroscopic techniques, scanning probe techniques, quartz crystal microbalance, materials research, fuel cells, solar cell and photovoltaic cells. Memberships ➢ ➢ ➢ ➢ ➢ ➢ ➢

International Association of Advanced Materials Association of Chemical Sensors in Taiwan Chemistry Society in Taiwan Chemical Engineering Society in Taiwan Taiwan Electrochemical Society International Society of Electrochemistry The Electrochemical Society

Research outcome Prof. Shen-Ming Chen (h-index > 50, total citation > 10000), Prof. Shen-Ming Chen has published above 550 research and review papers in international SCI journals. He have edited or attended two books for NOVA publications titled “Nanostructured Materials for Electrochemical Biosensors” and “Biosensors: Properties, Materials and Applications” and contributed four book chapters.

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12-15 November, 2017, Hanoi, Vietnam

Application of Nanocomposite Materials Modified Electrodes in Electrochemical Sensing of Biomolecules and Biosensors Shen Ming Chen Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, Taiwan. Email: [email protected] Recently, many investigations have been carried out for the fabrication of chemically modified electrodes on the use of micro and nanocomposites for different applications. Possibly nanomaterials modified electrodes are emerging as a real candidate for verity of potential applications due to its high surface area and biocompatibility along with better antifouling ability. The emerging applications of modified electrodes are in the fabrication of devices for biosensors and environmental sensors. Since, the environmental pollution has become a worldwide problem and the wastewater from the industries contains many organic pollutants and heavy metal ions which cause serious effect on the environment. Hence, we have prepared different chemically modified electrodes on the use of micro and nanomaterials for electrochemical sensing of biomolecules and environmental pollutants. For instance, the βcyclodextrin entrapped graphite modified screen printed carbon electrode (SPCE) can selectively detect the dopamine (DA) with the low limit of detection (LOD) of 11 nM. 1 The biomass-derived activated carbons, fullerene-C60/Pd nanoparticles and fullerene C60 wrapped graphene oxide composite modified electrodes show the LOD of 4.5 5.6 and 8 nM, respectively for DA. 2–4 The aforementioned modified electrodes can detect the DA in the real samples such as snail hemolymph, human blood serum, rat brain solution and commercial DA injection samples. The Cu nanoparticles/pectin scaffold on graphene modified electrode detects the hydrogen peroxide and glucose with a LOD of 2.5 and 3.1 µM, respectively.5 The zinc oxide–copper oxide heterostructures modified electrode shows the LOD of glucose about 3.8 nM.6 While, the glucose oxidase immobilized reduced graphene oxide (rGO) and fullerene-C60 composite modified electrode shows the LOD for glucose about 35 µM.7 On the other hand, we have also developed the sensitive modified electrodes for trace level detection of Environmental Hazardous Chemicals such as hydrazine, nitrite, Hg ions, Pb ions and nitrobenzene. For example, the Pd nanoparticles on porous activated carbons modified electrode can simultaneously detect Cd, Pb, Cu, and Hg ions with the LOD of 41, 50, 66 and 54 nM, respectively.8 The Ni nanoparticles on carbon porous materials modified electrode shows the LOD for Hg ions as 2.1 nM.9 The Bi nanoribbon modified electrode detect the lead and cadmium ions with a lower LOD of 0.104 µg/L and 0.145 µg/L.10 The pectin stabilized Au nanoparticles exhibited high catalytic activity towards amitrole and shows the LOD of 35 pM.11 Green synthesized Ag nanoparticles/rGO modified can detects the NB even up to 0.5 µM with the LOD of 0.26 µM.12 The Au nanoparticles decorated activated graphite modified SPCE shows LOD of 0.57 nM for hydrazine.13 Notes and references 1. S. Palanisamy et al, Carbohydrate Polymers 135, 2016, 267-273. 2. V. Veeramani et al, Scientific Reports 5:10141 | DOI: 10.1038/srep10141. 3. S. Palanisamy et al, Journal of Colloid and Interface Science 448, 2015, 251–256. 4. B. Thirumalraj et al, Journal of Colloid and Interface Science 462, 2016, 375–381. 5. V. Mani et al, Electrochimica Acta 176, 2015, 804-810. 6. C. Karuppiah et al, Sensor and Actuator B: Chemical 221, 2015, 1299-1306. 7. B. Thirumalraj et al, RSC Advances 5, 2015, 77651-77657. 8. P. Veerakumar et al, ACS Applied Materials & Interfaces 7, 2015, 24810–24821. 9. P. Veerakumar et al, ACS Applied Materials & Interfaces DOI: 10.1021/acsami.5b10050. 10. R. Devasenathipathy et al, Electroanalysis 27, 2015, 2341-2346. 11. V. Mani et al, Analyst 140, 2015, 5764-5771. 12. C. Karuppiah et al, RSC Advances 5, 2015, 31139-31146. 13. C. Karuppiah et al, Electrochimica Acta 139, 2014, 157-164.

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The 12th Asian Conference on Chemical Sensors (ACCS2017)

12-15 November, 2017, Hanoi, Vietnam

Keynote speaker Prof. Jong-Heun Lee Materials Science & Engineering Korea University, Korea Email: [email protected]

Title: Morphological, Compositional, and Heterostructural Design of Oxide Semiconductor Chemiresistors: New Challenges and New Opportunities Prof. Jong-Heun Lee received his BS, MS, and PhD degrees from Department of Inorganic Materials and Engineering, Seoul National University, Seoul, Korea in 1987, 1989, and 1993, respectively. Between 1993 and 1999, as a senior researcher, he developed automotive air-fuelratio sensors at the Samsung Advanced Institute of Technology. He was a Science and Technology Agency of Japan (STA) fellow at the National Institute for Research in Inorganic Materials (currently NIMS, Tsukuba, Japan) from 1999 to 2000 and a research professor at Seoul National University from 2000 to 2003. Dr. Lee has been a professor at the Department of Materials Science and Engineering, Korea University since 2003. He has actively participated in his academic societies as journal editors of Sensors and Actuators B: Chemical (SCI) and Science of Advanced Materials (SCIE), international advisory board member in Analytical and Bioanalytical Chemistry (SCI), conference co-chairman in International Meeting on Chemical Sensors 2016, and conference organizers and so on. He is a fellow member of the Korean Academy of Science and Technology. In 2014, he has been selected as ‘Highly Cited Researchers’ by Thomson Reuters for ranking in the top 1% most cited papers. He has won the awards including ‘POSCO TJ Award’ (2017) by POSCO TJ Foundation, ‘Korea University Alumni Prize for Best Research’ (2016), ‘Knowledge Creation Award’ (2014) by Ministry of Science, ICT, and Future Planning of Korea, ‘100 future-leading technologies and their developers’ (2013) by National Academy of Engineering of Korea, ‘the patent of year’ (Ji-Seok-Young Prize, 2001) from Korean Intellectual Property Office, and ‘Granite Tower Best Teaching Awards’ (2008 and 2009) from Korea University. He published 277 peer-reviewed papers (H-index: 47, total citation: 7,618 by web of science) and holds 40 domestic and international patents.

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The 12th Asian Conference on Chemical Sensors (ACCS2017)

12-15 November, 2017, Hanoi, Vietnam

Keynote Speaker Professor Jun-ichi Anzai PhD. in Pharmaceutical Science Graduate School of Pharmaceutical Sciences Tohoku University, Sendai, Japan Office: +81-22-795-6841 Email: [email protected] Educational background 3/1981 Ph.D, Graduate School of Pharmaceutical Sciences, Tohoku University, Japan 3/1978 Master, Graduate School of Pharmaceutical Sciences, Tohoku University, Japan Professional Experiences 4/2000-present 2/1997-3/2000 8/1991-1/1997 5/1989-9/1990 4/1983-7/1991

Professor, Graduate School of Pharmaceutical Sciences, Tohoku University, Japan Professor, Faculty of Pharmaceutical Sciences, Tohoku University, Japan Associate Professor, Faculty of Pharmaceutical Sciences, Tohoku University, Japan Research Associate, Electronics Design Center, Case Western Reserve University, Cleveland, USA Research Associate, Faculty of Pharmaceutical Sciences, Tohoku University, Japan

Field of Research ➢ Electrochemical biosensors ➢ Drug delivery systems Memberships ➢ Japan Association of Chemical Sensors Research outcome He has published nearly 300 original papers in international journals and several book chapters (hindex: 42, as of March 2017). He is currently an editorial board member or editor of international journals including “Sensors & Actuators B”, “Biotechnology & Bioengineering”, and “Materials”.

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12-15 November, 2017, Hanoi, Vietnam

Layer-by-layer assemblies as key materials in biosensing and controlled release Jun-ichi Anzai Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba 6-3, Aramaki, Sendai 980-8578, Japan Email: [email protected]

Layer-by-layer (LbL) films are prepared by the successive deposition of polymeric materials on the surface of solid substrates, such as metals and glass through attractive forces, including electrostatic interactions, hydrogen bonding, and biological affinity. In a typical procedure, the solid substrate is alternately immersed in aqueous solutions of the polymers, followed by rinsing to remove nonspecifically or weakly adsorbed polymers (Figure 1a). The thickness of the film can be regulated simply by changing the number of deposited layers, because film thickness increases with the number of depositions. Biopolymers, such as proteins, polysaccharides, and DNA can also be used as building blocks for constructing LbL films, because these biopolymers contain net electric charges. Hollow microcapsules can be constructed by LbL deposition of polymers on the surfaces of colloidal particles, followed by dissolution of the core (Figure 1b). These microcapsules are stable over a wide pH range. Therefore, LbL microcapsules are being widely studied as drug carriers. An advantage of LbL microcapsules is that the structure of their shell membrane can be tailored at the molecular level. LbL films and microcapsules have been used in the construction of optical and electrochemical sensors and drug delivery systems. Recent progress in the development of biosensors and controlled release systems based on LbL assemblies are discussed here.

Figure 1. Preparation of LbL films (a) and microcapsules (b). References: 1)Adv. Drug. Del. Rev., 63, 809(2011); 2)Anal. Sci., 28, 929(2012); 3)J. Mater. Chem. B, 2, 5809(2014); 4)Mater. Sci. Eng. C, 34, 384(2014); 5)Langmuir, 30, 9247(2014); 6) J. Mater. Chem. B, 3, 7796(2015); 7)Polymers, 9, 202(2017).

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Invited Talks

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12-15 November, 2017, Hanoi, Vietnam

The 12th Asian Conference on Chemical Sensors (ACCS2017)

12-15 November, 2017, Hanoi, Vietnam

A1-Inv. 01 Associate Professor: Takeo Hyodo Graduate School of Engineering, Nagasaki University, Japan Office: +82-95-819-2644 E-mail: [email protected] Educational background 3/1997 Doctor, Graduate School of Engineering Sciences, Kyushu University, Japan 3/1994 Master, Graduate School of Engineering Sciences, Kyushu University, Japan Professional Experiences 4/2011–present 8/2010–3/2011 4/2005–7/2010 4/1997–3/2005

Associate Professor, Division of Chemistry and Materials Science, Graduate School of Engineering, Nagasaki University, Japan Associate Professor, Department of Materials Science and Engineering, Faculty of Engineering, Nagasaki University, Japan Assistant Professor, Department of Materials Science and Engineering, Faculty of Engineering, Nagasaki University, Japan Research Associate, Department of Materials Science and Engineering, Faculty of Engineering, Nagasaki University, Japan (11/2003–8/2004: Visiting Researcher, Department of Materials Science and Technology, Massachusetts Institute of Technology (MIT), USA)

Field of Research ➢ Chemical gas sensors (semiconductor, catalytic combustion, adsorption/combustion, solid electrolyte, and electrochemical gas sensors) ➢ Mesoporous and macroporous materials for various electrochemical devices Memberships ➢ [International] The Electrochemical Society, International Society of Electrochemistry ➢ [Domestic] The Electrochemical Society of Japan (ECSJ), Japan Association of Chemical Sensors (JACS), The Ceramic Society of Japan, The Chemical Society of Japan Research outcome He published 119 peer-reviewed papers and proceedings, and holds 10 domestic and international patents (number of patent applications: 23). He received some awards (Sano Award from ECSJ in 2002, Seiyama Award from JACS in 2010, Distinguished Paper Awards from ESCJ in 2001 and 2005, and Best Paper Presentation Award in ACCS2011).

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12-15 November, 2017, Hanoi, Vietnam

Adsorption/combustion-type micro VOC sensors —Effects of catalytic combustion activities of VOCs on their gas-sensing behavior Takeo Hyodo1,*, Takeru Hiura1, Kazunori Nagae1, Takahiko Sasahara2 Kai Kamada1, Taro Ueda1 and Yasuhiro Shimizu1 1

Graduate School of Engineering, Nagasaki University, Japan; *E-mail: [email protected] 2 Gas Equipment R & D Center, Yazaki Energy System Corporation, Japan

Adsorption/combustion-type micro gas sensors, which were fabricated by utilizing the microelectromechanical system (MEMS) technology and an oxide-film fabrication technique employing an air-pulse fluid dispenser, excel at detecting a low concentration of volatile organic compounds (VOCs) in comparison with other types of gas sensors [1–7]. The sensor structure is similar to that of general catalytic combustion-type gas sensors, but the sensor-operating conditions are quite different from that of the catalytic combustion-type gas sensors, as shown in Fig. 1. VOC molecules are firstly adsorbed on the surface of the sensor materials at lower temperatures (generally for 9.6 s) and their dynamic combustion with abruptly rising temperature by pulse heating (generally for 0.4 s) realizes large dynamic responses to VOCs. Our group showed that the dynamic VOC responses are largely dependent on the amount of VOCs adsorbed, in the last ACCS conference in Penang, Malaysia (ACCS2015) and in our paper [6], but the catalytic oxidation behavior of the adsorbed VOCs over the sensing materials is also a quite important factor in determining their dyanmic VOC-response behavior. We will discuss the effects of the catalytic combustion activities of representative VOCs on their VOC-sensing behavior, together with their temperature-programmed desorption and oxidation (TPD and TPO, repsectively) properties. References [1] T. Sasahara et al., Sens. Actuators B, 99 (2004) 532. [2] T. Sasahara et al., Sens. Actuators B, 108 (2005) 478. [3] T. Hyodo et al., Chemical Sensors, 24 (2008) 67. [4] Y. Yuzuriha et al., Sensor Lett., 9 (2011) 409. [5] T. Hyodo et al., Sens. Actuators B, 202 (2014) 748. [6] T. Hyodo et al., Sens. Actuators B, 220 (2015) 1091. Figure 1. Schematic drawing of a [7] K. Nagae et al., ECS Trans., 75(16) (2016) 23. representative adsorption/combustiontype gas sensor and its typical sensorsignal profile.

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A1-Inv. 02 Prof. Sang Sub Kim Ph.D. in Materials Science Department of Materials Science and Engineering Inha University, Republic of Korea Office: +82-32-860-7546 Email: [email protected] Educational Background 2/1994 Ph.D., Materials Science, POSTECH, Korea 2/1990 Master, Materials Science, POSTECH, Korea 2/1987 BS, Metallurgical Engineering, Seoul National University, Korea Professional Experiences 3/2007- Present 8/2002-2/2007 12/2005-1/2007 3/1996-7/2002 3/1999-2/2000 9/1995-2/1996 8/1994-8/1995

Professor, Inha University, Korea Associate Professor, Chonnam National University, Korea Visiting Professor, University of Alberta, Canada Assistant Professor, Associate Professor. Sunchon National university, Korea Visiting Scientist, National Institute for Materials Science (NIMS), Japan Senior Researcher, Korea Institute of Science and Technology (KIST), Korea Visiting Scientist, National Institute for Materials Science (NIMS), Japan

Field of Research ➢ ➢ ➢ ➢

Thin film processing and characterization Surface and interface analysis Synthesis and application of nanostructure and nanomaterials Chemical sensors

Memberships ➢ Materials Research Society of Korea ➢ The Korean Institute of Surface Engineering ➢ The Korean Sensor Society ➢ The Korean Ceramic Society Research outcome He is the author of over 240 peer-reviewed papers regarding thin films, surface and interfaces, synthesis of nanomaterials, and semiconducting chemical gas sensors. He is an editorial board member of such journals as Scientific Reports, Journal of Sensors, Metals and Materials International, and Electronic Materials Letters.

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12-15 November, 2017, Hanoi, Vietnam

Core-Shell Structured Nanomaterials for Sensitive Gas Sensors Jae-Hun Kim, Ali Mirzaei, Jae-Hyoung Lee and Sang Sub Kim Department of Materials Science and Engineering, Inha University, Incheon 22212, Republic of Korea; Email: [email protected]

High-performance gas sensors are needed to improve safety in daily life. Even though the gas sensing performance of new nanostructured metal oxides has improved significantly, some aspects of these new nanomaterials have not been fully explored yet. Core-shell (C-S) and hollow shell nanostructures are two types of advanced materials for gas sensing applications. Their popularity is mainly due to the synergetic effects of the core and shell in C-S nanostructures, the high surface areas of both C-S and hollow nanostructures, and the possibility of tuning the shell thickness within the range of the Debye length for such nanostructures. In addition to the type of sensing material, morphology, sensing temperature, and porosity, shell thickness is one of the most important design parameters. Unfortunately, less attention has been paid to shell thickness. Herein, we demonstrate that the thickness has an undeniable role in the gas sensing response of the resulting material. In this presentation, this aspect of sensing materials is overviewed. By referring to related works, we show how shell thickness can affect the sensing properties of both C-S and hollow nanostructures. Researchers in this field will be able to fabricate more sensitive gas sensors for real applications by better understanding the role of shells in gas sensing properties.

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A2-Inv. 01 Professor: J.R.Morante PhD. in Physics, Electronics Materials. Physics Faculty, University of Barcelona. Spain and IREC, Catalonian Institute for Energy Research Jardins de les Dones de Negre,1. Sant Adrià del Besòs. 08930. Spain Phone: +34-661443271 Email: [email protected]

Professor J.R. Morante is, since 1985, full professor of the Faculty of Physics of the University of Barcelona. Since 2009 he has been the director of the advanced materials for energy area of the Energy Research Institute of Catalonia, IREC, and since the end of 2015 he has been appointed as director of this institute. Previously he has been Vice Dean and dean of the Faculty of Physics of the University of Barcelona, director of the Department of Electronics of this university, head of studies in Electronic Engineering and co-coordinator of the interuniversity master between the University of Barcelona and the Polytechnic University of Catalonia of the master on Engineering in Energy. His activities have been centered in electronic materials and devices; the assessment of their related technologies and production processes, specially emphasizing materials technology transfer. He was involved on sensors, actuators and Microsystems, especially on chemical sensors. Currently, he is also focused in the mechanisms of energy transfer in solid interfaces involving electrons, photons and phonons as well as chemicals. Likewise, he is specialized in the development of renewable energy devices and systems for applications in the field of energy and environment based on nano structures and their functionalization. His special attention is focused on advanced materials and structures for artificial photosynthesis including the production of hydrogen and solar fuels as well as on the development of fully integrated autonomous systems for smart energy management in building communities and cities. He has co-authored more than 600 publications with more than 16,300 citations (h> 66) according scopus data base and 19 patents, has directed 41 doctoral theses, has participated / coordinated numerous projects in different international and industrial programs (> 50), organized various international technological scientific conferences in the field of sensors / microsystems and "nanoenergy" and has been distinguished with the medal Narcís Monturiol of the Generalitat de Catalunya. He has also served as vice president of the European Materials Society and is the editorin-chief of the Journal of Physics D: Applied Physics.

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Fully integrated electrochemical micro machined sensor based on silicon platforms A. Morata1, F. Baiutti1, N. Alayo1, I. Garbayo1, F. Chiabrera1, L. Fonseca2, A. Tarancón1, J. R.Morante 1,3 1

Institut de Recerca en Energia de Catalunya (IREC), E-08930 Sant Adrià del Besòs, Spain; 2 Institut de Microelectrònicade Barcelona, CNM-CSIC, Bellaterra. Barcelona.Spain; 3 Universitat de Barcelona, Barcelona, Spain. Email: [email protected]

A cross plane fully integrated potentiometric micro sensor based on a thin ion conducting membrane and micromachined silicon hotplate has been developed. A new fabrication route is shown that combines silicon industrial micro fabrication processes with the use of nanometric thin films of Ytria Stabilized Zirconia (YSZ) as solid electrolyte. This cross plane configuration allows a huge reduction of the electrolyte thickness. YSZ membranes of 500 nm or even less can be used, leading to a drastic drop of the working temperature and thermal mass of the active area of the device. This new paradigm opens the way for the fabrication of reliable, low cost, low consumption and rapid gas electrochemical gas sensors. Examples of oxygen measurements based on the Nerst law will particularly be reported and discussed. To the best of our knowledge, up to now, there is no reported integration of potentiometric membrane designed according electrochemical or lambda sensors requirements on silicon microelectronics combining the advantages of silicon micro fabrication industrial processes with those based on the thin film deposition techniques keeping complete technology compatibility. Compared to the planar configuration, where the separation between the electrodes is of the order of some tens of microns, the cross plane configuration allows an enormous reduction of the electrolyte thickness. YSZ membranes are deposited by Pulsed Laser Deposition (PLD). The ultrathin dense YSZ membrane remains self-supported after several typical microelectronic processes according to the IREC patent Nº P26999ES01.

Figure 1. (a) Scheme of the fabricated device. (b) Top-view optical image of a YSZ selfsupported membrane

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A2-Inv. 02 Associate Professor: Shinji Tamura PhD. of Engineering, Department of Applied Chemistry, Faculty of Engineering, Osaka University, Japan Office: +81-6-6879-7353 Email: [email protected] Educational background 3/2001 Ph.D, Engineering, Osaka University, Japan

Professional Experiences 04/2015-present 04/2004-03/2015 04/2001-03/2004

Associate Professor position, Osaka University, JAPAN Assistant Professor position, Osaka University, JAPAN Postdoctoral fellow, Japan Society for the Promotion of Science, JAPAN

Field of Research ➢ Gas Sensors ➢ Solid Electrolytes ➢ Inorganic Pigments Memberships ➢ ➢ ➢ ➢ ➢ ➢ ➢

Japan Association of Chemical Sensors The Electrochemical Society of Japan The Rare Earth Society of Japan The Chemical Society of Japan The Ceramic Society of Japan The Solid State Ionics Society of Japan Japan Society of Colour Material

Research outcome He is the author of over a hundred of scientific articles published in reputed journals. He has also published thirteen book chapters related his research field.

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12-15 November, 2017, Hanoi, Vietnam

Low-temperature Operative Catalytic Combustion-type Hydrogen Gas Sensors Incorporating Cerium Oxide-Zirconium Oxide Based Catalysts Shinji Tamura, Shun Yasuhara, Ayaka Hosoya, Nobuhito Imanaka Department of Applied Chemistry, Faculty of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan; E-mail: [email protected]

Hydrogen (H2) is accepted as a clean energy resource, however, its treatment should be very sensitive because of its high explosive nature. Therefore, it is necessary to use the H2 monitoring tool for the practical use of H2 as the energy resource in our lives. From the viewpoints of cost and easy treatment, compact H2 sensor such as catalytic combustion-type sensor is considered to be a promising candidate for its demand. However, the selective H2 detection is difficult for the catalytic combustion-type sensor with conventional H2 oxidizing catalysts because they require relatively high temperatures for the oxidation of H2 on the catalyst. In this research, we have successfully fabricated a novel catalytic combustion-type H2 gas sensor that could operate at low temperatures by employing a Pt-loaded cerium oxide-zirconium oxidetin oxide solid solution (10 wt% Pt/Ce0.68Zr0.17Sn0.15O2.0) as the H2 oxidizing catalyst. The 10 wt% Pt/Ce0.68Zr0.17Sn0.15O2.0 catalyst showed high oxidizing activity toward hydrogen; the complete H2 oxidation was achieved at 55 °C (Figure 1(a)) and over 95% H2 was oxidized even at 40 °C. As a result, we realized stable and quantitative H2 detection at as low as 40 °C with high sensitivity by selecting the 10 wt% Pt/Ce0.68Zr0.17Sn0.15O2.0 as the H2 oxidation catalyst of the catalytic combustion-type sensor (Figure 1(b)).

Figure 1. (a) H2 conversion of 10 wt% Pt/Ce0.68Zr0.17Sn0.15O2.0 catalyst as a function of temperature and (b) representative sensor response curve obtained by varying H2 concentration from 0 to 10000 ppm and vice versa at 40 °C. Here, we defined the sensor sensitivity as the normalized difference of resistance in target gas and in air: (Rgas−Rair)/Rair.

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A3-Inv. 01 Prof. Dojin Kim Prof./Ph.D. in Dept. Materials Science & Engineering, Chungnam National University, Korea CP: +82-10-8225-4157 Email: [email protected] Educational background 2/1989 Ph.D., Mater. Sci. & Eng., Univ. Southern California, USA 2/1981 MS, KAIST, Korea Professional Experiences 9/1992-present 3/1981-8/1992

Professor, Chungnam National University, Korea Researcher, Electronics & Telecommunication Res. Inst., Korea

Field of Research ➢ Nano semiconductor materials and photo-electronic application ➢ Gas sensors: oxide nanostructure, mechanism, room temperature operation ➢ Photocalatytic semiconductor: water splitting electrode, photoelectrochemistry, and energy application

Memberships ➢ Material Research Society of Korea ➢ International Society of Electrochemistry

Research outcome He published more than 250 peer reviewed articles in the areas of semiconducting materials synthesis and electronic/optical/magnetic device application. Recently focusing on nanostructures synthesis and their electronic and energy applications including gas/bio sensors, photoelectrochemical cell electrode, displays, transparent conducting films, solar cells, etc.

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Nanostructural Oxide Gas Sensors toward Room Temperature Operation Nguyen Duc Chinh, Nguyen Minh Hieu, Chunjoong Kim, Dojin Kim Department of Materials Science and Engineering, Chungnam National University, Daejeon, 305-764 Republic of Korea; Email: [email protected]

Metal oxide materials have been extensively used as resistive gas sensors at elevated temperatures typically in the range 150-300 oC. The thermal energy is basically required because the sensing mechanism is based on the adsorption/desorption process of gas molecules, which are the thermally activated processes. Heat-up of the sensor materials facilitates either the adsorption/desorption of the analyte gas molecules and environmental oxygen on the oxide surface or the chemical reaction of the analyte gas molecules with preadsorbed oxygen on the surface, consequently to observe reasonably enhanced sensor response kinetics. However, the heating not only requires additional circuitry, but also can limit its use for flammable gases. Furthermore, recent progress of IoT requires room temperature operating sensors to be compatible with other components in the system. Therefore, a cool energy such as light has been considered to substitute the thermal energy for activation of the surface processes. We examined various oxide nanostructures and/or their composites (ZnO, In2O3, Fe2O3/CNT composite) for room temperature operation with assistance of light irradiation. The films were fabricated by various techniques of hydrothermal, arc discharge, sputtering methods. The surface morphology and structural properties were examined by SEM, TEM, X-ray diffraction, and X-ray photoelectron spectroscopy. The oxidizing and reducing gas sensing properties were examined at room temperature. The sensing mechanism of the nanostructures was also discussed.

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A3-Inv. 02 Dr. Nicolae Barsan PhD. in Solid State Physics, Institute of Physical and Theoretical Chemistry University of Tübingen, Germany Office: +49 70712978761 Email: [email protected] Educational background 1993 PhD in Solid State Physics, Institute of Atomic Physics, Bucharest, Romania 1982 Diploma in physics, University of Bucharest, Department of Physics, Romania Professional Experiences 1982-1983

High School teacher of Physics, Vulcan, Romania

1983-1984

Physicist, Geophysical and Geological Prospect Enterprise, Bucharest, Romania

1984 – to date

Institute of Physics and Technology of Materials, Bucharest, Romania (senior researcher/research professorship since 2005)

November 1995 – to date

Researcher at the Institute of Physical and Theoretical Chemistry, University of Tübingen, Germany

Field of Research • Physical chemistry and technology of chemical sensors • Gas/chemical sensors applications • Surface Physics and Chemistry • Semiconductor Physics • Memberships Founding member (May 2008) and member of the Steering Committee of the International Society for Olfaction and Chemical Sensing (ISOCS) Member of the American Chemical Society Research outcome (Web of Science H-index: 48. More than 8500 citations) He is the author of more than 100 of scientific articles published in reputed journals. He has also published nine book chapters related to chemical sensors and chemical sensors applications.

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Noble Metal Sensitization of SnO2 and WO3 based Gas Sensors: How Does it Work Nicolae Barsan and Udo Weimar Institute of Physical and Theoretical Chemistry, University of Tübingen, Germany; Email: [email protected]

Hetero-structures – metal-oxide or oxide-oxide – determine the gas sensing performance of noble metal loaded semiconducting metal oxides. The current understanding is based on models that distinguish between a chemical and an electronic effect and are based on fragmentary experimental evidence. Two major mechanisms are reported in literature: The spill-over and the Fermi-level control mechanism. A spill-over related sensitization mechanism is ascribed to noble metal clusters with a metallic nature, i.e. reduced, which improve the adsorption of a reactive gas. This mechanism solely influences the gas reception. A spill-over related activation of oxygen was shown for Au-loaded SnO2. The Fermi-level control mechanism is ascribed to oxidized/partially oxidized noble metal clusters; the different work functions of the materials (SMOX and noble metal oxide) lead to an alignment of the two Fermi-levels at the oxide-oxide interface and cause a bending of the electronic bands at the surface, which has a large impact on the charge transport in the sensing layer and thus controls the measured resistance; if the oxidation state of the noble metal changes, the Fermi-levels will realign and thus change the resistance. Here, we will show based on complex investigation techniques that for the case of Pt, Pd and Rh the sensitization process is very complex and includes changes in the surface chemistry as well as changes of the conduction mechanisms in the sensing layer. In special cases, the sensing is completely controlled by the heterojunctions formed at the surface of the SMOX materials.

Scheme 1. DRIFTS spectra illustrating the reaction of an undoped (uIPC), Pd (PdIPC) doped and Pt (PtIPC) doped SnO2 polycrystalline thick film gas sensor with 240 ppm CO in a background of 3% r.h. D2O; Reference 3% r.h. D2O. 22

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A4-Inv. 01 Professor Tatsuo Yoshinobu a) Department of Electronic Engineering, Tohoku University, 6-6-05 Aza-Aoba, Aramaki, Aoba-ku, Sendai, Japan b) Department of Biomedical Engineering, Tohoku University, 6-6-05 Aza-Aoba, Aramaki, Aoba-ku, Sendai, Japan Email: [email protected]

Tatsuo Yoshinobu was born in Kyoto, Japan, in 1964. He received PhD from Kyoto University for his study on gas source molecular beam epitaxy of silicon carbide. In 1992, he joined Osaka University, where he started the development of silicon-based chemical sensors. From 1999 to 2000, he was a guest scientist at Research Centre Jülich, Germany. Since 2005, he is a professor for electronic engineering at Tohoku University, Sendai, Japan. Since 2008, he is also a professor at the Graduate School of Biomedical Engineering, Tohoku University.

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On the Possibility of LAPS as a Sensing Element in Microfluidic Devices Tatsuo Yoshinobu Department of Biomedical Engineering, Tohoku University, 6-6-05 Aza-Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan. Email: [email protected]

The light-addressable potentiometric sensor (LAPS) is a semiconductor-based chemical sensor that can measure the ion concentration on the sensing surface in a spatially resolved manner. It has been applied to multi-analyte sensors as well as chemical imaging sensors [1]. The flat sensing surface facilitates construction of microfluidic devices on LAPS, allowing the entire floor of the flow channel to serve as a sensing area. The ion concentration can be monitored at an arbitrary location in the course of reaction inside the channel. Figure 1 shows an example of measurement system for dynamic analysis of reaction and diffusion across the boundary of two laminar flows in a Y-shaped channel. Two flows, typically those with analyte and reagent respectively, are injected from two inlets. They meet each other in the channel and the reaction proceeds along the stream. The distribution of ion concentration under steady state is visualized, in which the distance along the boundary corresponds to the time of reaction and diffusion. Prospects of LAPS as a sensing element in microfluidic devices will be discussed. (a)

(b)

Figure 1. (a) Y-shaped channel on the sensing surface of LAPS for analysis of reaction and diffusion across the boundary of laminar flows. (b) Visualization of ion concentration under steady state. [1] T. Yoshinobu, K. Miyamoto, C. F. Werner, A. Poghossian, T. Wagner and M. J. Schöning, "Lightaddressable Potentiometric Sensors for Quantitative Spatial Imaging of Chemical Species", Annual Review of Analytical Chemistry, 10 (2017) pp.225-246.

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A4-Inv. 02 Professor: Han-Sheng Chuang PhD. in Mechanical Engineering, Department of Biomedical Engineering National Cheng Kung University, Taiwan Office: +886-6-2757575#63433 Email: [email protected] Educational Background 5/2010 Ph.D, Mechanical Engineering, Purdue University, IN, U.S.A. 6/2000 M.S., Mechanical Engineering, National Cheng Kung University, Taiwan

Professional Experiences 2/2015-present 8/2011-2/2015 5/2009-present 2/2010-7/2011 10/2008-1/2010 1/2001-7/2005

Associate Professor, Department of Biomedical Engineering, National Cheng Kung University, Taiwan Assistant Professor, Department of Biomedical Engineering, National Cheng Kung University, Taiwan Cofounder, Microfluidic Innovations LLC, IN, U.S.A. Postdoctoral Researcher, Mechanical Engineering and Applied Mechanics, University of Pennsylvania, PA, U.S.A. Research Assistant, Birck Nanotechnology Center, Purdue University, IN, U.S.A. Associate Engineering, Center for Measurement Standards, Industry Technology Research Institute (ITRI), Hsinchu, Taiwan

Fields of Research ➢ ➢ ➢ ➢

Bio-microfluidics/naofluidics MEMS/NEMS Technologies Optical Diagnostics Biomechanics of C. elegans

Memberships ➢ ➢ ➢ ➢

American Society of Mechanical Engineering (ASME) Association of Chemical Sensors in Taiwan (ACST) Taiwanese Society of Biomedical Engineering (TSBE) Nanotechnology and Micro System Association (NMST)

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BioSketch Han-Sheng Chuang is currently an associate professor in the Department of Biomedical Engineering at National Cheng Kung University, Taiwan. Dr. Chuang received his bachelor and master degrees from the Department of Mechanical Engineering at National Cheng Kung University in 1998 and 2000, respectively. He joined Industrial Technology Research Institute (ITRI) as a R&D engineer in 2001. After then, he worked with Professor Steve T. Wereley for advanced microfluidics and received his Ph.D. from the School of Mechanical Engineering at Purdue University in 2010. After graduation, he received an appointment as a postdoctoral researcher at University of Pennsylvania and worked with Professor Haim H. Bau on cell sorting and Caenorhabditis elegan manipulation. In 2005, he was awarded a competitive fellowship from Ministry of Education, Taiwan. He and his research fellows were the finalists of the prestigious Burton D. Morgan Business Competition in 2008 and 2009, respectively. Lately, he received the 2014 Young Researcher Career Grant from the Ministry of Science and Technology, the 2015 Young Scholar Award from the Taiwan Comprehensive University System, and the 2016 Excellent Teaching Award from NCKU. In addition, he is also a cofounder of a US-based start-up, Microfluidic Innovations, since 2009 and an executive director of the Association of Chemical Sensors in Taiwan. Dr. Chuang has dedicated to the field of microfluidics for more than 10 years. His current research interests focus on Bio-micro/nano-fluidics, MEMS/NEMS technologies, optical diagnostics, and biomechanics of C. elegans.

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Rapid Disease Screening with a Diffusometric Immunosensor Han-Sheng Chuang Department o fBiomedical Engineering, National Cheng Kung University, Taiwan; Email: [email protected]

Diffusometry is sensitive to the geometric change of particle. By functionalizing the particle surface with a specific antibody, the target antigens can be detected through the diffusivity change resulting from their immunoreactions. Considering Brownian motion is a self-driven phenomenon, the diffusometric immunosening features no washing steps, rapid detection, high flexibility, and high sensitivity. Up to now, the technique has been applied in many biomedical fields, such as monitoring of microorganism motility and diagnosis of diseases with biomarkers. Despite the mentioned advantages, the diffusivity change of the conventional diffusometry can be compromised at low abundance antigens because the proteins are much smaller than the capture particles in size. To lift the restriction, we hereby present an improved diffusometric immunosensing technique by grafting additional gold nanoparticles to the capture particles to enhance the size changes (Scheme 1). A diabetic retinopathy biomarker, TNF-α, was chosen to evaluate the proposed immunosensing technique. Spherical gold nanoparticles (AuNPs) showed better enhancement than gold nanorods in the measurement. The limit of detection (LOD) was improved by at least 10 folds down to 10 pg/mL. In addition, a dichotomous method was also developed to enable rapid detection yet avoid the tedious calibration process. By comparing the diffusivity of an unknown concentration of target molecules with that of a reference solution, the relationship of concentrations between the two solutions could be explicitly determined in 1 min. The minimum distinguishable concentration reached as low as 2-fold higher or lower than the basal concentration. For a proof of concept in the diagnosis of diabetic retinopathy, tear samples were collected from four volunteers including three healthy subjects and one proliferative diabetic retinopathy patient. All of the data showed good agreements with the preset conditions. The technique eventually provides an insight to rapid diagnoses of diseases in the early stage.

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Scheme 1 (A) Schematic of the optical diffusometric platform. (B) Fluorescent particles with grafted AuNPs suspended in the PDMS microchip. (C) Compasion of the diffusivities of TNFα with concentrations 2 folds lower or higher the basal concentration of 1 ng/mL.

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A5-Inv. 01 Professor: Genxi Li PhD. in Analytical Chemistry Department of Biochemistry Nanjing University, Nanjing 210093, P. R. China Office: +86-25-83592510 Email: [email protected] Educational background 6/1994 Ph.D, Analytical Chemistry, Nanjing University, P. R. China 6/1991 Master, Analytical Chemistry, Nanjing University, P. R. China 6/1988 Bachelor, Polymer Chemistry, Nanjing University, P. R. China Professional Experiences 5/2001-present 11/2008-10/2011 1/2006-present 1/1999-5/2010 7/1998-6/2001 7/1994-5/1996

Professor position, Nanjing University, P. R. CHINA Dean, School of Life Sciences, Shanghai University, P. R. CHINA Professor affiliated with Shanghai University, P. R. CHINA Chair, Department of Biochemistry, Nanjing University, P. R. CHINA Visiting Scholar, Munich University, GERMANY; Tohoku University, JAPAN; Harvard University, USA Postdoc fellow, Biochemistry, Nanjing University, P. R. CHINA

Field of Research ➢ Electrochemical biosensor ➢ Colorimetric biosensor ➢ Nano-based biosensor Memberships ➢ 2006-2011 Deputy Secretary-General, 2011-2016 Vice-President and Secretary-General, Chinese Protein Society ➢ 2006-Present Member of the Committee for Chemical Sensor, China Instrument & Control Society ➢ 2009- Present Member of the Council of the Biophysical Society of China ➢ 20010- Present Member of the Council of the Chinese Society of Biochemistry and Molecular Biology Research outcome He is the author of 290 scientific articles published in reputed journals. He has also published one book and six book chapters related to biosensor.

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Electrochemical and colorimetric biosensors for the assay of disease marker proteins with clinical applications Genxi Li State Key Laboratory of Pharmaceutical Biotechnology, Department of Biochemistry, Nanjing University, Nanjing 210093, P. R. China, and Center for Molecular Recognition and Biosensing, School of Life Sciences, Shanghai University, Shanghai 200444, P. R. China. Email:[email protected]

With the development of proteomic technologies, lots of disease marker proteins have been discovered for many kinds of diseases. Due to the high importance and potential application in the diagnosis of these diseases, detection of the disease marker proteins receives more and more attention. So, detection methods are required to be developed towards the assay of the newly discovered disease makers. In the meantime, the proposed methods are expected to be simple, rapid, sensitive and cost-effective, so as to be employed for the diagnosis and treatment of these diseases. Among the techniques for the detection of disease marker proteins, electrochemistry and colorimetry have been known to be simple, rapid, sensitive and convenient to be operated. Moreover, the great achievements in the related research fields such as surface modification, molecular assembly, molecular recognition, especially nanotechnology, and the employment of many kinds of nanomaterials have opened more opportunities for the development of such kind of immunoassays. Therefore, remarkable progress has been made on the design of electrochemical and colorimetric sensing systems for disease marker detection over the years. In this talk, I would like to present some typical strategies recently proposed in my lab for electrochemical and colorimetric detection of some disease marker proteins, and even the direct and specific detection of targets from clinical samples by making use of the advantages of electrochemical and colorimetric biosensors. For instance, based on the "host-guest" inclusion of peptide side chain groups into synthetic macrocyclic host, the coordination of metal ion by short 3-mer peptides, and the bioconjugation of therapeutic function groups to peptides, several electrochemical biosensors have been developed for the detection of disease markers in cancer of various origins, as well as in Alzheimer’s disease. Furthermore, by conjugating the smallmolecule peptide probe with some kinds of macromolecules, the modified peptide probe can be used together with the original probe to electrochemically study the relationship between the number of nitrated amino acids and functional state of the target proteins. In the meantime, by assembly of dynamic DNA “walker” nanostructure on an electrode surface, fg/mL concentrations of several disease-related proteins can be assayed with impressive selectivity.

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A5-Inv.02 Professor: Yutaka Ohno Ph. D, Vice-director Educational background March 2000, Ph.D, Quantum Engineering, Nagoya University, Japan March 1997, Master, Quantum Engineering, Nagoya University, Japan March 1995, Bachelor, Electronics, Nagoya University, Japan Professional Experiences 2015-Present Professor, Vice-director, Center for Integrated Research, Institute of Materials and Systems for Sustainability, Nagoya University, Japan 2015 Visiting Professor, Institute of Advanced Energy, Kyoto University, Japan 2015 Professor, Ecotopia Institute, Nagoya University, Japan 2013-2014 Visiting Professor, Department of Applied Physics, Aalto University, Finland 2008-2014 Associate Professor, Department of Quantum Engineering, Nagoya University, Japan 2003-2007 Researcher, Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST) 2000-2002 Assistant Professor, Department of Quantum Engineering, Nagoya University, Japan 1999-2000 Research Fellow, Japan Society for the Promotion of Science (JSPS) Field of Research ➢ Nanocarbon-based electronics ➢ Flexible electronics ➢ Electron devices and sensors Memberships ➢ ➢ ➢ ➢

Member, The Japan Society of Applied Physics Member, The Institute of Electronics, Information and Communication Engineers Experts committee member, Technical Group on Electron Devices, IEICE Electronics Society Vice-president, The Fullerenes, Nanotubes and Graphene Research Society

Research outcome He is the author of 125 scientific articles published in reputed journals and 21 book chapters and reviews. He also presented 90 invited talks in major conferences.

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Highly-sensitive, flexible electrochemical biosensor based on carbon nanotube thin film Yutaka Ohno Center for Integrated Research of Future Electronics, Institute of Materials and Systems for Sustainability, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan Email: [email protected]

Neurotransmitters are emitted by nerve cells to convey information in brain. They are also known as one of stress markers in saliva. The concentrations of neurotransmitters are 10-1000 nM in cerebrospinal fluid and ~100 pM in saliva [1, 2]. Carbon nanotube (CNT) is promising electrode material for flexible electrochemical sensors to detect neurotransmitters [3]. With integrating such flexible biosensors to high-performance and flexible integrated circuits based on CNTs, wearable healthcare/medical devices can be realized, which have the potential to revolutionize preventive medical care and health promotion. In our recent works, we have studied CNT thin film technologies from the growth of CNTs and the thin film formation to device fabrication and characterization on flexible and stretchable films. High-mobility flexible thin-film transistors (TFTs) and their integrated circuits have been realized on a transparent plastic film. We have also demonstrated highly-sensitive, flexible CNT biosensors with excellent uniformity in the sensing property. Here, we introduce novel adsorption voltammetry for ultrahigh sensitivity detection of neurotransmitters using a CNT film. We also show the possibility of selective detection of neurotransmitters. [1] K. O. Schwab et al., Eur. J. Clin. Chem. Clin. Biochem., 30, 541 (1992) [2] T. Okumura et al., J. Chromatogr. B, 694, 305 (1997) [3] C. B. Jacobs et al., Analyst, 136, 3557 (2011)

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A6-Inv. 01 Dr. Toshio Itoh Ph.D. in Crystalline Materials Science National Institute of Advanced Industrial Science and Technology (AIST), Japan Office: +81-52-736-7089 Email: [email protected] Educational background 3/2005 Ph.D., Crystalline Materials Science, Nagoya University, Japan 3/2002 Master, Crystalline Materials Science, Nagoya University, Japan Professional Experiences 4/2013-present 4/2005-3/2013

Senior Researcher, National Institute of Advanced Industrial Science and Technology (AIST), Japan Researcher, National Institute of Advanced Industrial Science and Technology (AIST), Japan

Field of Research ➢ ➢ ➢ ➢ ➢ ➢ ➢

Low-concentrate volatile organic compound gas sensors Semiconductive gas sensors for room air Semiconductive gas sensors for breath analysis Noble metal-loaded metal oxides as semiconductive gas sensors Layered organic-inorganic hybrid materials as semiconductive gas sensors International standardization for portable VOC detectors Semiconductive gas sensors working at high temperatures

Memberships ➢ The Chemical Society of Japan ➢ The Ceramic Society of Japan ➢ Japan Association of Chemical Sensors Research outcome He is the author of several dozens of scientific articles about semiconductive gas sensors published in reputed journals. He has also been involved in developing a prototype for breath analyzer, commercializing a mouth odor detector, and developing an international standard for portable VOC detectors.

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Semiconductive Gas Sensors for Low-Concentrate Volatile Organic Compounds (VOCs) Toshio Itoh, Ichiro Matsubara, Takafumi Akamatsu, Akihiro Tsuruta, and Woosuck Shin National Institute of Advanced Industrial Science and Technology, Shimo-shidami, Moriyama-ku, Nagoya 463-8560, Japan; Email: [email protected]

Volatile organic compounds (VOCs) are contained in various kinds of airs, such as indoor air and exhaled breath. Most of VOCs contained in the airs are extremely low concentration, i.e. ppb level. Sick building syndrome is caused by harmful VOCs, which are diffused from building materials, bonding agents, and items brought by residents. For example, the Ministry of Health, Labour and Welfare in Japan regulates that formaldehyde and total VOCs (TVOCs) should not exceed 80 ppb and 400 g/m3 in residences for human health. In order to keep the quality for residences and working places, it is desired to provide gas sensors which can detect ppb level of VOCs. Exhaled breath also includes many kinds of VOCs, which are associated with metabolism, mouth odor, and diseases. Specifically, the concentrations of VOCs indicated as biomarkers of diseases are also ppb level, so that the gas sensors for breath analysis are also required high sensitive properties. We have investigated gas sensor materials of layered organic-inorganic hybrids (organic/MoO3 hybrids; Figure 1a) for formaldehyde and noble metals-loaded tin oxide (Pt,Pd,Au/SnO2; Figure 1b) for TVOCs. Moreover, we have developed prototype system for VOC detection in exhaled breath (Figure 1c), which equipped with a gas condense unit, gas chromatography columns, and the Pt,Pd,Au/SnO2 sensors as detectors.

(a)

(b)

(c) Size: 4 x 4 mm2

Size: 9.5 x 5 mm2

Figure 1. (a) Depiction of the organic/MoO3 hybrid sensing material and the fabricated organic/MoO3 hybrid sensor, (b) the Pt,Pd,Au/SnO2 sensor, and (c) the prototype system for VOC detection in exhaled breath.

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A6-Inv. 02 Prof. Kengo Shimanoe Department of Energy and Material Sciences, Faculty of Engineering Sciences, Kyushu University 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580, Japan Tel:+81-92-583-7876, Fax:+81-92-583-7538, E-mail: [email protected] Career * Graduated from Department of Applied Chemistry, Faculty of Engineering, Kagoshima University in 1983. * Obtained Master of Engineering Degree from Kyushu University in 1985. Doctor degree: April 1993 (Doctor of Engineering, Kyushu University) * Advanced Technology Laboratory, Nippon Steel Corporation Researcher 1985-1991 Senior Researcher 1991-1995. * Appointed as a staff of Department of Materials Science and Technology, Graduate School of Engineering Sciences, Kyushu University Research associate 1995-1998 Shifted to Department Energy of Material Sciences, Faculty of Engineering Sciences in 1998 (due to Reorganization of the graduate school) Research associate 1998-1999 (Sept.) Associate Professor1999 (Oct.)-2005 (Jan. 15th) Professor 2005 (Jan. 16th). Field of Researches: 1. Chemical sensors 2. New functional materials 3. Solid catalysts Activities in scientific societies (Main items) * Journal of Sensor Science and Technology, Editorial Boad Member (2011-) * Korean Journal of Materials Research (K-MRS) Editorial Board Member (2008-) * Research adviser in “National Institute for Material Sciences (NIMS)” (2007-2010) * Member of editors in Journal “Electrochemistry” (2002). * General affairs of Kyushu branch in “The Electrochemical Society of Japan” (2001) * A member on the board in “Japan Association of Chemical Sensor”(1999-present) * Assistant editor for Asia in “Sensors and Actuators B: Chemical” (1995-2004.3)

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Gas sensing properties of MEMS-type metal oxide gas sensor: Design of receptor function for pulse-heating mode Kengo Shimanoe, Ken Watanabe, Koichi Suematsu Faculty of Engineering Sciences, Kyushu University, Japan Email: [email protected]

Metal oxide semiconductor gas sensors are widely used for various purposes such as detection gas leakage and toxic gas, breath analysis, environmental protection and so on. Our lab. has reported material designs, receptor function, transducer function and utility factor, for metal oxide gas sensors [1, 2]. In addition, we found the possibility of ppb-level detection by using integration of such three factors [3], as shown in Fig. 1. Now such high performance gas sensors are desired for an MEMS-type because of low power and compact devices. MEMS-type gas sensors are operated by pulse-heating mode and such an operation gives some problems. Many gas molecules including water vapor adsorb on the metal oxides. By heating at a moment, the complicated reactions are caused at the surface. To control such complicated reactions, we need to optimize sensing materials as well as operation mode. For example, small size Pd (< 3nm) is useful for water vapor effect. In addition, the sensor in pulse-heating mode gives interesting sensing properties different from that of constant-heating mode (Fig. 2). The gas response in pulse-heating mode was high at first 100ms and gradually reached to value obtained by constant-heating. The magnitude of first response was dependent on the concentration of inflammable gas. Furthermore, perovskite oxide as a second receptor enhances sensor response in pulse-heating mode. In this presentation, the details will be shown clearly.

Fig. 2 Gas response to C7H8 for SnO2 operated by pulse-heating.

Fig. 1 Material design for MEMS-type gas sensor.

[1] N. Yamazoe, G. Sakai, K. Shimanoe, Catalysis Surveys from Asia, 7(1), pp. 63-75 (2002). [2] N. Yamazoe, K. Shimanoe, Semiconductor gas sensors, pp.1-34 (2013), WOODHEAD PUBLISHING. [3] K. Shimanoe, M. Yuasa, T. Kida, N. Yamazoe, IEEE Nanotech. Mater. Dev. Conf., pp. 38-43 (2011).

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B1-Inv. 01 Professor: Osamu Niwa PhD. in Engineering (Applied Chemistry) Advanced Science Research Laboratory Saitama Institute of Technology, Japan Office: +81-48-585-6304 Email: [email protected] Educational background 3/1990 PhD. in Engineering (Applied Chemistry), Kyushu Univ., JAPAN 3/1983 Master, Department of Chemistry, Faculty of Engineering, Kyushu Univ. JAPAN Professional Experiences 10/2015-present 4/2004-9/2015 2/2009-10/2009 4/1983-1/1999

Professor, Advanced Science Research Laboratory, Saitama Institute of Technology, Fukaya, Saitama, 369-0293 JAPAN Group Leader, Materials Science and Engineering, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, JAPAN Group Leader, NTT Lifestyle and Environmental Technology Laboratories, JAPAN, Atsugi, Kanagawa, JAPAN Researcher, NTT Ibaraki Laboratories and NTT Basic Research Laboratories, Nippon Telegraph and Telephone Corporation, JAPAN

Field of Research ➢ ➢ ➢ ➢

Electrochemical biosensors Micro and nanoelectrodes based sensing devices Nanocarbon film electrode for electroanalysis and chemical sensors Surface plasmon resonance (SPR) based biosensors

Memberships ➢ ➢ ➢ ➢

The Chemical Society of Japan Electrochemical Society of Japan The Japan Society for Analytical Chemistry American Chemical Society

Research outcome He is the author of over 200 scientific articles published in the international journals. He developed interdigitated array microelectrodes and portable type SPR system and SPR imaging system. 37

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Nanocarbon Film Based Sensors for Heavy Metal Detection Osamu Niwa1, Tatsuya Machida1, Daiki Kato2, Shunsuke Shiba1,2, Tomoyuki Kamata2, Dai Kato2 1

Advanced Science Research Laboratory, Saitama Institute of Technology, Fukaya, Saitama, 369-0293 Japan, 2National Institute of Advanced Industrial Science and Technology, Japan ; Email: [email protected]

Detection of heavy metal ions such as Cd2+, Pb2+ and As3+ in environmental and drinking water is very important to prevent serious health problem. We have been studying sputter deposited nanocarbon films consisting of sp2 and sp3 bonds using sputtering technology. Since the film shows wide potential window in negative potential region, the metal ion can be selectively accumulated onto the electrode surface and a low detection limit could be achieved in anodic stripping voltammetry (ASV). Recently, we developed Au nanoparticle (AuNP) embedded carbon film electrode with a one-step reproducible process by using unblanced magnetron (UBM) cosputtering. The film can be successfully applied to detect As3+ ion in ASV measurement because As3+ ion can be accumulated onto AuNP embedded carbon film more efficiently than bulk Au electrode. Figure 1 shows plan(A) and cross-sectional(B) view of AuNP embedded carbon film electrode. The size of AuNP is about 5 nm, uniformly dispersed in the carbon film. Figure 2 shows ASV curves of 1000 ppb As3+ in 0.1M Na2HPO4 with the AuNP embedded UBM carbon film(red solid line, Au=17%) and the bulk Au electrode. The red dotted line is ASV result corrected by Au concentration [1]. The nomalized curent at uNP embedded UBM carbon film shows much larger current than that of bulk Au electrode, indicating high electrocheical activity of AuNP. AuNP embedded carbon film shows stable response by continuous ASV measurement, whereas, the current reduced rapidly with bulk Au electrode. Recently, we tried to control effective surface area of AuNP by plating Au onto AuNP embedded electrode and succeeded in controlling sensitivity of As3+ in ASV measurement [1] D. Kato, T. Kamata, D. Kato, H. Yanagisawa, O. Niwa, Anal. Chem., 88, 2944-2951 (2016)

Figure 2. ASV curves of 1000 ppb As3+at AuNP embedded (Red solid), bulk Au (black solid) and normalized current (red dotted) with Au concentration

Figure 1. Plan (left) and cross-sectional(right) TEM image of AuNP embedded carbon film

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B1-Inv. 02 Ho Won Jang, Ph.D Associate Professor Department of Materials Science and Engineering Seoul National University, Korea Office: +82-2-880-1720 Email: [email protected] Educational background 8/2004 Ph.D., Materials Science and Engineering, POSTECH, Korea 2/2001 Master, Materials Science and Engineering, POSTECH, Korea Professional Experiences 3/2012-present 6/2009-2/2012 1/2006-5/2009

Associate Professor, Seoul National University, Korea Senior Research Scientist, Korea Institute of Science and Technology, Korea Research Associate, University of Wisconsin-Madison, USA

Field of Research • Wafer-scale synthesis of oxide thin film nanostructures using physical vapor deposition and wet solution process • Synthesis of 2-dimensional materials including graphene and transition metal disulfides • Heteroepitaxy of complex oxide thin films by atomic layer control • Chemical sensors for electronic nose and electronic tongue • Photoelectrodes and catalytic electrodes for water splitting and CO₂ reduction • Mott insulators for nanoelectronics and smart window • Localized Surface Plasmon Resonance for optoelectronics Memberships ➢ Korea Institute of Metals and Materials ➢ Korean Ceramic Society ➢ Korean Sensors Society Research outcome He published about 160 publications in international referred journals and the h-index of the publications is 35 (based on Web of Science). He is serving as an Editor for Electronic Materials Letters. He received Shinyang Academic Award from the College of Engineering of Seoul National University in 2016.

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Nanostructured heterojunctions for high performance chemoresistive gas sensors based metal oxides and 2-dimensional materials Ho Won Jang Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Korea; Email: [email protected]

Nanostructuring, heterostructuring and surface decoration are powerful methods to enhance chemoresistive gas sensing properties of semiconducting metal oxides and 2-dimensional materials such as graphene and MoS2. Here we introduce various approaches to significantly promote gas sensing performance of metal oxides and 2-dimensional materials. Heterostructured nanostructures with surface metal decoration were synthesized and the gas sensing properties were compared with pristine samples (dense planar or bare). The enhanced properties were attributed electronic and chemical sensitizations induced by making the heterojunctions. We propose a strategy to realize room temperature or heater-less gas sensor array based on 2-dimensional materials for the Internet of Things, emphasizing that lower power consumption with faster response and recovery speed, reproducible fabrication process, and long-term stability are critical.

Figure 1. Various applications of chemoresistive gas sensnors based on 2-dimensional (2D) materials.

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B2-Inv. 01 Professor Giorgio Sberveglieri University of Brescia, Department of Information Engineering Via Valotti 9, 25133 BRESCIA, Italy Office: +39 030 3715771; Mobile: +39 335 395005; Fax: +39 030 2091271; E-mail: [email protected] Positions and education 1996: Full Professor in experimental Physics, University of Brescia (Italy) 1994: Full Professor in Physics, University of Ferrara (Italy) 1987: Associate Professor in Physics, University of Brescia (Italy) 1980: Laurea Degree in Physics, cum laude, University of Parma (Italy) Research activity My research activity is focused on applied physics and the development of functional materials and their applications. I started in the 70s working in the field of thin film solar cells (1971-1987). I after moved to the field of gas sensors focusing first on the development of thin film techniques and then on nanowire technology to develop functional metal oxide layers. My activity addressed both the study of the synthesis techniques to control and optimize the material structure at the micro and nanoscale to optimize its receptor and transductor function and the exploitation of these devices and electronic nose systems in different applicative fields including environmental monitoring, medicine, food quality, safety and security. Working in the field of gas sensors, in 1988 I founded the SENSOR laboratory (http://sensor.ing.unibs.it/). Originally composed by myself and a technician, it’s now a well established lab in the field of gas sensors and solar cells (see next) where about 20 people work, including personnel from both the University of Brescia and the National Council for Research (CNR). In the period 20012003 I was the coordinator of the industrial-applicative network of the National Institute for the Physics of Matter (INFM), contributing to start about 23 spin-off companies in Italy. Recently, the activity on functional materials at SENSOR lab has been dedicated to explore applications other than gas sensors, including biosensors and solar cells, leading to several publications on high impact papers, including some cover papers and funded projects. I published over 310 papers on peer-reviewed journals, including 3 cover papers, 1 internal-cover paper, getting about 7000 citations and an h-index of 42. http://sensor.unibs.it/people/prof-giorgio-sberveglieri

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Metal oxides nanowires for chemical sensors and Electronic Noses V. Sberveglieri2,3 , E. Comini1,3, D Zappa1, V. Galstyan1 and G. Sberveglieri1,3 1

2

SENSOR, University of Brescia, Via Branze, 38, Brescia, Italy CNR - Institute of Biosciences and Bioresources, Sesto Fiorentino (FI), Italy 3

NANO SENSOR SYSTEMS srl, Via Branze,38, Brescia, Italy *Corresponding author: [email protected]

Abstract: In this paper we present the synthesis of MOX NWs using diverse technologies such as thermal evaporation, thermal oxidation and anodization. The results obtained for tin, zinc, copper, nickel, tungsten, titanium oxides and will be extensively described. All these metal oxides nanowires have been integrated in functional devices, as the Small Sensors Systems (S3) Electronic Nose developed in SENSOR Lab, for chemical sensing and then tested towards a wide range of chemicals, including security and food safety applications. The S3 Electronic Nose has been successfully employed in various areas including the whole food-chain for the evaluation of quality, safety and authenticity (DPO, geographical origins). Regarding food applications where including the diagnosis of microbial and chemical contamination. While regarding the security filed the EN was applied for hidden-people detection, using its capability to detect odour related to human-sweat and to control the possible cross-contamination. To this aim, artificial sweat samples have been prepared starting from a chemical blend simulating the human-sweat environment added with a culture of indigenous bacteria of human-skin. Our results show the potentiality and flexibility of the proposed NWs MOX technology in both security field or food safety. In particular, the authors have developed a portable and battery operated EN called S3 (Small Sensor System) mini. The S3 mini, after a training process with the creation of a specific database, will be able to give selectivity and analysis capability in different fields.

Keywords: Metal oxides, Nanowires, Electronic Nose, Food safey, human health, artificial sweat.

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B2-Inv. 02 Professor: Inkyu Park PhD. in Mechanical Engineering, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea Office: +82-10-2786-7337 Email: [email protected] Educational background 12/2007 Ph.D, Mechanical Engineering, UC Berkeley, USA 8/2003 M.S. Mechanical Engineering, University of Illinois at Urbana-Champaign, USA 2/1998 B.S. Mechanical Engineering, KAIST, Korea Professional Experiences 1/2009-present 2/2014-2/2015 1/2008-1/2009 12/2007-11/2008 5/2005-11/2008 Field of Research ➢ ➢ ➢ ➢ ➢

Assistant Professor (’09-’12), Associate Professor (’12-’16) and Tenured Associate Professor (’16-present), KAIST Visiting Professor, University of California at San Diego, USA Co-founder & CTO, nPrintSolutions, inc., USA Research Specialist, Berkeley Sensor and Actuator Center (BSAC), USA Visiting Researcher, Hewlett Packard (HP) Laboratory at Palo Alto, USA

Nanomaterial based sensors for flexible and wearable applications Controlled synthesis and assembly of one dimensional nanomaterials MEMS-Nano integration Ultra-low power gas sensors based on MEMS platform and CMOS-based Si nanowires Soft materials and nanocomposites for stretchable force, strain and pressure sensors

Memberships ➢ Board Member: Korea Society of Mechanical Engineers (KSME), Korean Society of Manufacturing Technology Engineers (KSMTE), The Korean Society of Micro and Nano Systems, Korean Sensors Society (KSS) / Member: ASME, ACS, IEEE, MRS ➢ Editorial Board member: Scientific Reports, International Journal of Precision Engineering and Manufacturing – Green Technology, Journal of Sensor Science and Technology, etc. Research outcome He is the author of more than 60 SCI journal papers and 100 international conference proceeding papers. He is a recipient of several awards including IEEE NANO Best Paper Award, Hewlett Packard (HP) Open Innovation Research Award, etc.

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A new route to the fabrication of heterogeneous metal oxide nanomaterial array for integrated chemical sensors Inkyu Park Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea; Email: [email protected]

Chemically synthesized 1D nanomaterials have shown unique properties and great promises for numerous engineering applications such as nanoelectronics, display, energy conversion and bio/chemical sensing. However, their real-life comm ercial applications are still quite limited mainly due to the lack of economic, well-controlled and reliable assembly/integration process on functional devices. Accordingly, various methods such as dielectrophoresis, optical trapping and nanomanipulation have been actively developed for the controlled integration and assembly of 1D nanomaterials. However, these methods still cannot provide high controllability, reproducibility and throughput. Furthermore, there exist only weak bonding forces (eg. van der Waals force or hydrogen bonding) between nanomaterials and device electrodes, greatly limiting the robustness and reliability of the 1D nanomaterial-based devices. In this talk, I will explain an alternative approach called “focused energy field (FEF) synthesis” in order to resolve the abovementioned limitations in the assembly and integration of 1D nanomaterials on functional microelectronic devices. This method is based on a localized, lowtemperature and liquid-phase reaction for the selective synthesis and in-situ integration of 1D nanomaterials at desired locations on the microelectronic devices. In specific, the local synthesis and direct integration of nanomaterials is enabled by localized Joule heating at the desired local hot spots, convective heat and mass transfers of precursor solutions and selective endothermal chemical reaction at the hot spots, all in liquid phase. The advantages of this method are (a) direct, self-aligned synthesis of nanomaterials without further assembly or integration steps required, (b) extremely simple and inexpensive setup for the fabrication, (c) minimal requirement of chemicals and energy for the process, (d) robust contact between nanomaterials and device substrates. I will explain these advantages with indepth explanation of process mechanisms, fabrication results with mechanical and electrical characterization, and its applications to physical / chemical sensors.

Scheme 1. Localized synthesis of 1D nanomaterials and application to chemical sensor array

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B3-Inv. 01 Professor Ping Wang Biosensor National Special Laboratory Department of Biomedical Engineering No.38 Zheda Road Zhejiang University, Hangzhou, 310027 China Tel/Fax: 86 571 87952832 (o) Email: [email protected]; [email protected] Homepage: http://mypage.zju.edu.cn/cnpwang Educational Background 1984-B.S. degree, Electrical Engineering from Harbin Institute of Technology 1987-M.S. degree, Electrical Engineering from Harbin Institute of Technology 1992-Ph.D. degree, Electrical Engineering from Harbin Institute of Technology 1992-1994: Post-doctoral Fellow, Biosensors National Special Lab, Dept. of Biomedical Engineering, Zhejiang University, China Employment 6/1987-6/1989 Lecturer, Electrical Engineering from Harbin Institute of Technology, China; 12/1994-present Professor in Biosensors National Special Lab, Dept. of Biomedical Engineering of Zhejiang University 1/2002-7/2002 Visiting professor in Electronic Design Center of Case Western Reserve University, USA. 1/2005-3/2005 Visiting professor in Biosensor and Bioinstrumentation Laboratory in University of Arkansas, USA. Field of Researches: 1. Biosensors and Bioelectronics, Bioinspired Electronic Nose and Electronic Tongue 2. Cell and Molecular-based Biosensors, Biomimetic Olfaction and Taste Sensors 3. Bio-MEMS and Bio-NEMS (Bio-Micro and Nano-Electro-Mechanical System) Memberships He is an International advisory/organising board member of Biosensors and Bioelectronics Symposium (BBS), a member of The International Society for Olfaction and Chemical Sensing(ISOCS), a member of Asia-Pacific Regional Steering Committee of International Meeting on Chemical Sensors (IMCS).a member of International Steering Committee of Asian Conference on Chemical Sensors (ACCS). He is also a Director of Biomedical Measurement Society of China, Vice-Director of Ion & Biosensor Society and ViceDirector of Biomedical Sensors Technique Society of China. Research outcome He is the author of over two hundred of scientific articles published in reputed journals. He has also published four books related to biomedical sensors, cell and molecule-based biosensors and applications.

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The Biomimetic Cell-based Biosensors for Applications in Biomedical and Environmental Detection Ping WANG Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Ministry, of Education, Department of Biomedical Engineering, Zhejiang University, Hangzhou, 310027, China State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Shanghai, China, Tel/Fax: 86 571 87952832; Email: [email protected] Cell-based biosensors is a research hotspot in biosensors and bioelectronics fields because they can detect the functional information of biological active analytes. They characterize with high sensitivity, excellent selectivity and rapid response, and have been applied in many fields, such as biomedicine, environmental monitoring and pharmaceutical screening and so on. Currently, cell-cultured technology, silicon micromachining technology and genetic technology have promoted exploration of cell-based biosensors dramatically. The cell-based biosensors consist mainly two parts: one is living cells or neural network cultured on the surface of transducer and another is transducer including potential sensing and chemical sensing, and maybe also with stimulus elements. The live cell serves as the sensing element or primary transducer to respond to external stimuli such as electric and chemical stimulus, antiviral drugs and various receptor ligands and so on, and then it will produces corresponding output or changes, such as extracellular changes of molecular and ion, action potential and impedance change induced by the cellular metabolism and so on. The transducer or secondary transducer such as silicon field-effect device can detect these responses and convert them into electrical signals. All this make up the whole cell-based biosensors. The experimental setup of biomimetic cell-based biosensors systems for measurement of drugs, food and chemical odorants and tastants are described. The future possible development and perspective of these biosensors in biomedical and environmental detection fields are also discussed. Keywords: biosensors; biomimetic sensors; cell-based biosensors; smell sensors; taste sensors

1. Fig. 1 The basic principle and its applications of biomimetic cell-based biosensors

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Acknowledgements: This work was supported by the National 973 Project of China (grant no. 2015CB352101) and National Natural Science Foundation of China (grant no. 31571004, 61320106002, 31627801, 31661143030). Reference: 1. S. Prasad, E. Tuncel, and M. Ozkan, Biosensors and Bioelectronics, vol. 21, no. 7, pp. 1045–1058, 2006. 2. T. Wang, N. Hu, J. Cao, J. Wu, K. Su, and P. Wang, Biosensors and Bioelectronics, vol. 49, pp. 9–13, 2013. 3. Q. Wang, J.R. Fang, D.C. Cao, H.B. Li, N. Hu, P. Wang, Biosensors and Bioelectronics, 2015, 72: 10-17. 4. L Zou, C Wu, Q Wang, J Zhou, K Su, H Li, N Hu, P Wang, Biosensors and Bioelectronics, 2015, 67: 458–464.P. Wang, Q Liu, “Cell-based Biosensors: Principles and Applications”, Artech House Press Inc., USA, 2010.

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B3-Inv. 02 Prof. Ching-Chou Wu Department of Bio-Industrial Mechatronics Engineering National Chung Hsing University, Taichung City 402, Taiwan E-mail: [email protected] Tel: +886-4-22851268 Fax: +886-4-22879351

•

•

•

Education: • Bachelor of Engineering (Biomedical), June, 1994, Neuroscience Lab., Department of Biomedical Engineering, Chung-Yuan University, Chung-Li, Taiwan. • Master of Engineering (Biomedical), June, 1996, Neuroscience Lab., Institute of Biomedical Engineering, Chung-Yuan University, Chung-Li , Taiwan. Professional experience: • Assistant professor, National Chung- Hsing University, 2005/02-present. • COE fellow, 2004/04~2005/01, Graduate School of Science, Tohoku university, Sendai, Japan • Post doctor fellow, 2003/11~2004/03, Graduate School of Environmental Studies, Tohoku university, Sendai, Japan • Doctor of Philosophy in Biomedical Engineering, June, 2003, Biosensing Technology Lab., Institute of Biomedical Engineering, National Cheng-Kung University, Tainan, Taiwan Areas of Expertise: • Electrochemical Bio-sensing Technology • Capillary-Electrophoresis Microchip & Electrokinetic Microfluidic Control • Lab-on-a-chip Applications • Scanning Probe Microscopy in Biomedical Science.

• http://bimewww.nchu.edu.tw/en-teacher/en-Pro_now_16.htm

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A Cell-Based Chip Integrated with Microfluidic Control and Dissolved Oxygen Sensors for Estimation of Cellular Respiratory Activity Ching-Chou Wua, Chieh-Jen Wanga, Lee-Tian Changb a

Department of Bio-industrial Mechatronics Engineering, National Chung Hsing University, b Department of Veterinary Medicine, National Chung Hsing University, Addr: No. 145 Xingda Rd. Taichung, Taiwan. Email: [email protected]

Adipocyte activity determines the metabolism of carbohydrate and fatty acid of human beings, related to the formation of diabetes. Evaluation of adipocyte activity allows the researchers to realize the causes of type II diabetes and therapeutic methods. In the study, a microfluidic chip containing dissolved oxygen (DO) sensors of three-electrode electrochemical system was developed for the measurement of DO around the cultivated adipocytes. All gold electrodes were made by the lift-off microfabrication process. Moreover, the iridium oxide (IrOx) layer was electrodeposited on a gold electrode as the reference electrode. The DO sensing chip was fixed by the homemade polymethylmethacrylate (PMMA) clamp. Adipocytes were estimated with the stimulation of different glucose concentration (0 mM, 11 mM) and insulin, and then the DO signal was analyzed by three kinds of methods. The respiratory activity can be defined as a DO consumption ratio of the drug-stimulated adipocytes versus normal status adipocytes. The results show that the respiratory activity obtained by the diffusion-model of ultramicroband electrode presented high reproducibility and good physiological behavior. The DO microfluidic chip has a great promise in the application of estimating the effect of drugs on the cellular physiological behavior to replace animal and clinical experiments.

Figure 1. (a) Scheme of the chip design. (b) The chronoamperometry measured under different solutions containing glucose and insulin. 49

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C1-Inv. 01 Prof. Wan-Young Chung Dept. of Electronic Engineering Pukyong National University, Busan 48513, South Korea Office: +82-51-629-6223 Email: [email protected] Educational background 12/2009 Dr.Sc., Electrical and Information Eng., University of Oulu, Finland 5/1998 Dr.Eng., Material Science and Technology, Kyushu Univ., Japan 8/1992 Ph.D., Semiconductor Eng., Kyungpook Nat’l Univ., Korea Professional Experiences 9/2008-present 3/1993-8/2008

Professor, Pukyong National University, South Korea Assistant Professor, Associate Professor in Semyung Univ. and Dongseo Univ., South Korea

Field of Research ➢ ➢ ➢ ➢ ➢ ➢ ➢

Wireless sensor network Wireless sensors, chemical sensors, health sensors Battery-less smart sensor module IoT applications Visible light communications Wearable sensors Brain computer interface

Memberships ➢ Principle vice chair of The Korean Sensor Society ➢ Associate Editor, IEEE Sensors Journal ➢ Associate Editor, Int’l Journal on Smart Sensing and Intelligent Systems Awards ➢ ➢ ➢ ➢ ➢ ➢

Best Award of Korean Patent Property in 2000 Silver Medal, Korea Venture Fair-2002 Annual Best Article Award in 2009 Presidential Award for Technology Innovation in 2012 Busan Science and Technology Award in 2013 First Prize Paper Award, 2017 IEEE ICASI

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Battery-free Technology for Wireless Sensor Applications Wan-Young Chunga a

Dept. of Electronic Engineering, Pukyong National University,Busan 48513, South Korea Email: [email protected]

A next wave in the ear of computing technologies cuts across many areas of modern day living. In the Internet of Things (IoT) paradigm, many of the objects that surround us are on the network in one form or another. Sensor network technology is rising to meet this new challenge, in which information and communication systems are invisibly embedded in the environment around us. A sensor node is a node in a sensor network that is capable of performing some processing, gathering sensory information and communicating until other connected nodes in the network. For the operation of the node, the importance of a battery which operates the sensors, processor and communicating is not well-known but it is very important. Battery attached in a sensor node increases the size of the sensor node, and increase the cost for battery itself and periodical battery change, and the weight of the node. In addition, the battery material contaminates our surrounding environment. We have developed a battery-free sensor node by RF energy harvesting technology. And the developed battery-free sensor technology was applied for several applications such as meat or food freshness monitoring, ambient environment monitoring, and human activity morning in a short range between 10 and 40 cm, or in a long range upto 2 ~ 3 m. Acknowledgments: This work (2016R1A2B4015) was supported by Mid-Career Researcher Program through an NRF grant funded by MEST, Korea.

Figure 1. Photographic top-view and bottom-view of a smart sensor tag.

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C1-Inv. 02 Professor Jean-Marc Tulliani Ph.D. Materials Engineering Politecnico di Torino DISAT - Department of Applied Science and Technology Turin, Italy 10129 Torino - Italy Tel: +39 (0)11 090 47 00 Fax: +39 (0)11 090 46 99 Email: [email protected] [email protected]

Biochar as a sensing material for gas sensors Daniele Zieglera, Andrea Marchisioa, Mauro Giorcellia, Pravin Jagdalea, Alberto Tagliaferroa, Jean-Marc Tulliania a

Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi, 24, 10129 Torino, Italy Email: [email protected]

Biomass is available in huge amounts and constitutes a high quality carbon raw material source for carbon-based material synthesis. Nonetheless, different residues of biomass pyrolysis are becoming available from pilot plants producing energy. Thus, in the last years, biochar has been studied as potential substitute of more expensive carbon materials like carbon nanotubes, graphene and others for different applications. In this work, gas sensors based on different biochars were studied. The sensing materials and the sensors were investigated by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and laser granulometry measurements. The thick-films were prepared by drop-coating technique and their impedance determined at room temperature towards humidity, ammonia, methane and NOx. The best

Figure 1. Graphical abstract of the work. 52

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response was obtained towards relative humidity (RH): the thick films gave a response from around 5 RH%, and their impedance varied of 2 orders of magnitude after exposure to 100 RH%. Moreover, response and recovery times were reasonably fast (in the order of 1 minute). To conclude, sensors performances of biochars appear extremely promising for new applications of these “waste” materials as humidity sensors, both for environmental monitoring and for many industrial processes.

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C2-Inv. 01 Assistant Professor: Chatchawal Wongchoosuk Ph.D. in Physics, Department of Physics, Faculty of Science Kasetsart University, Thailand Office: +662-562-5555 ext. 3008 Email: [email protected] Educational Background 2011 Ph.D. in Physics, Mahidol University, Thailand 2007 M.Sc. in Physics, Mahidol University, Thailand 2005 B.Sc. in Physics (First Class Honors), Prince of Songkla University, Thailand Professional Experiences 1/2014-present 6/2011-1/2014 6/2010-9/2010

9/2009-5/2010

Assistant Professor position, Department of Physics, Faculty of Science, Kasetsart University, Thailand Lecturer position, Department of Physics, Faculty of Science, Kasetsart University, Thailand Assistant Researcher, Quantum Chemistry Group, Institute for Advanced Research and Department of Chemistry, Graduate School of Science, Nagoya University, Nagoya, Japan Assistant Researcher, Laboratory for Nanotechnology at the Institute of Microsystem Engineering (IMTEK), Albert Ludwigs University Freiburg, Germany.

Field of Research ➢ Quantum calculations and molecular dynamic simulation for the nanoscale systems ➢ Synthesis of nanomaterials, i.e. ZnO nanostructures, carbon nanotube, SiC nanotube, Graphene, 0D-3D nanostructures etc. ➢ Fabrication of molecular devices, i.e. hybrid gas sensors, FET, printed electronics, flexible electronics, electroluminescence gas sensors, chemiluminescence ➢ Electronic nose and intelligent systems, i.e. smart farm, smart cars, and smart home Research Outcome He has received over 10 research awards. He has served as a reviewer for several scientific journals such as Journal of Applied Physics, Applied Physics Letters, Crystal Growth & Design, Journal of Physics D: Applied Physics, Food Research International, New Journal of Chemistry, RSC Advances, Organics Electronics, Soft Matter, etc. He has published several dozens of articles in journals and two book chapters with four patents. 54

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Flexible Gas Sensors Based on Zero- to Three-Dimensional Carbon Nanostructures Chatchawal Wongchoosuk*, Yotsarayuth Seekaew, Kriengkri Timsorn, Gun Chaloeipote Department of Physics, Faculty of Science, Kasetsart University, Chatuchak, Bangkok 10900 Email: [email protected]

Flexible sensors have gained a great deal of attention in recent years due to their potential applications in healthcare monitoring, biomedicine, electronic skin, wearable sensing technology, soft robotics, safety equipments, smart systems and future space applications. Carbon-based nanomaterials possess unique structures and properties including high porous frameworks, high stability, high conductivity and low cost. Moreover, carbon-based nanostructures are one of the best candidate sensing nanomaterials in order to operate at room temperature for gas sensing application. In this work, we present fabrications of flexible gas sensors based on 0D (graphene quantum dots; GQDs), 1D (metal oxides doped carbon nanotubes) , 2D (bilayer graphene) and 3D (pillared graphene) carbon-based nanostructures. The GQDs were prepared by using the cutting and chemical reactions from graphene oxide. The carbon nanotube, graphene and pillared graphene were synthesized by thermal vapor deposition processes. The sensing carbon-based nanomaterials were deposited on flexible substrates with prefabricated electrodes via a modified inkjet printing method. Various gases and volatile organic compounds over a wide range of concentrations were used to characterize the sensing properties of each carbon-based sensing film. The sensing mechanisms of the flexible printed gas sensors on the desired targeted gases will be proposed and highlighted.

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C2-Inv. 02 Dr. Adisorn Tuantranont Ph.D. in Electrical Engineering Thailand Organic and Printed Electronics innovation Center (TOPIC) National Electronics and Computer Technology Center (NECTEC) 112 Thailand Science Park, Pahol Yothin Rd., Klong Luang, Pathumthani 12120 THAILAND Tel: (662) 564-6900 Ext. 2111, Fax: (662) 564-6756 Email:[email protected] [email protected] Educational background 2001 M.S.-Ph.D, Electrical Engineering, University of Colorado at Boulder, USA 1995 B.S., Electrical Engineering, King Mongkut Institute of Technology Ladkrabang, Thailand Professional Experiences 2010-Present 2016-Present 2016-Present 2014-Present

Research Unit Director, Thailand Organic and Printed Electronics Innovation Center (TOPIC), NECTEC General Secretary, Materials Research Society of Thailand (MRSThailand)-Member of IUMRS Adjunct Faculty, Suranaree University of Technology, Thailand Policy Fellow, National Science Technology and Innovation Policy Office (STI), Ministry of Science and Technology, Thailand

Field of Research ➢ Graphene, carbon nanotubes: synthesis, characterization and application ➢ Printed Electronics and Nanodevices, Micro-Electro-Mechanical Systems Memberships ➢ Materials Research Society of Thailand (General Secretary: MRS-Thailand) Research outcome He is the author and co-authors of more than 130 of scientific articles published in reputed journals. He is Editor, Applications of Nanomaterials in Sensors and Diagnostics (Springer Series on Chemical Sensors and Biosensors), Springer Verlag, Berlin, 2013. He has also published 4 book chapters related to graphene and nanomaterials in sensor applications.

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Printed Graphene Sensors: From research to commercialization Adisorn Tuantranont Thailand Organic and Printed Electronics Innovation Center (TOPIC), National Electronics and Computer Technology Center (NECTEC), National Sciences and Technology Development Agency (NSTDA), Thailand Email: [email protected], www.graphenethailand.com, www.topic.in.th,

Graphene, emerging as a true 2-dimensional material, has received increasing attention due to its unique physicochemical properties (high surface area, excellent conductivity, high mechanical strength, and ease of functionalization and synthesis). Printed Electronic also is a new wave of large-area electronics and flexible electronics manufactured by printing technology. The fusion of these two emerging technologies created the new opportunity to invent variety of novel electronic devices with low cost including nano sensors. Recent development on printed graphene sensors are comprehensively presented. Printed graphene based biosensors exhibited promising properties with good reliability suitable for commercial applications such as food pathogen sensors, biomedical sensors etc. Aflatoxin Sensors (AflaSense) using LAMP and electrochemical sensing technique on screen printing graphene sensor electrode will be presented to show the successful development of research to real commercialized products.

Our screen printed graphene electrode and Graphene-based Electrochemical Biosensors researched and commercialized by TOPIC.

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C3-Inv. 01 Professor: Young-Woo Heo Professor in School of Materials Science and Engineering Kyungpook National University, Korea Office: +82-53-950-7587, Email: [email protected] Educational background 12/2000 Ph.D, Materials Science and Engineering, University of Florida, USA, 02/1996 Master, Inorganic Materials Engineering, Kyungpook National University, Korea Professional Experiences 09/2015-present 01/2017-present 02/2005-present 01/1996-07/2000

Vice Dean, College of Engineering, Kyungpook National University, Korea Vice President, The Korean Vacuum Society, Korea Faculty, Materials Science and Engineering, Kyungpook National University, Korea Researcher, LG Chemicals Ltd./Research Park, Korea

Field of Research ➢ Sensors (Optical, Chemical, etc.,) ➢ ➢ ➢

Transparent Semiconducting Oxides for Transparent Electronics Materials and Devices for Solar Cell Growth and Characterization of Thin Film & Nanostructured Materials and Fabrication of their Devices

Memberships ➢ Editorial Board, Results in Physics ➢ The Korean Vacuum Society ➢ Materials Research Society Research outcome -

Author of 140 articles in journals and one book chapter. Publications have been cited over 7,040 times. Top 100 Materials Scientists of The Past Decade, 2000~2010 released by Thomson Reuters(2011).

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Energy bandgap tuning of halide perovskites for optical-sensors Young-Woo Heo, Se-Yun Kim, Sang-Wook Lee, Joon-Hyung Lee, Jeong-Joo Kim School of Materials Science and Engineering, Kyungpook National University, Korea; Email: [email protected]

Optical-sensors, which can convert incident light signals into electric signals, are very important components for realizing a wide range of industrial applications. Halide perovskite material is an emerging low-cost, solution-processable material with a tunable bandgap from the violet to nearinfrared, which has attracted a great deal of interest for applications in high-performance opticalsensors. In AMX3 formula, the band gap can be tuned through exchange of A site cation (A=Cs, Rb, CH3NH3 (methyammonium, MA), CHN2H4 (formadinium, FA)), B site metal cation (M=Sn, Pb) and halide anion (X=Cl, Br, I). For example, the energy bandgap can be tuned from 1.55eV to 1.48eV by exchange of organic cation (MA1-xFAxPbI3), and it can be tuned from 1.17eV to 1.55eV by exchange of metal cation (MASn1-XPbXI3), also the optical bandgap of perovskite material can be tuned by exchange of halide anion, from 1.55eV to 2.25eV and from 2.25eV to 2.96eV by MAPb(I1-XBrX)3 and MAPb(Br1-XClX)3 system, respectively, due to their homogeneous solid solution. In this presentation, energy bandgap, the solubility limit and structural type were investigated in the ternary phase diagram of MAPbI3, MAPbBr3 and MAPbCl3. In the single phase region, the bowing parameters about variation of lattice distance and energy bandgaps as function of halide composition were obtained. As a result, it was found that the change of lattice constant and Eg according to halide composition were well expected within a small error range using the obtained bowing parameter. Also, we suggested the origin of the small bowing of halide perovskite Eg. The life times of photo-excited carrier of single phases were investigated using time resolved Photoluminescence (TRPL) measurement. Also, the photoconductivity characteristics were analyzed, as a results, and it was possible to establish a composition design strategy to maximize photoelectric properties.

Scheme 1 (A) halide perovskite structure (MAPbX3, X=Cl, Br, I); (B) Kubelka-Munk plot of mixed halide perovskite

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Doctor Linh Viet Nguyen

C3-Inv. 02

Institute for Photonics and Advanced Sensing (IPAS) The University of Adelaide (UoA), North Terrace, SA 5005, Australia Office: +61-8-8313-2329 Email: [email protected] Educational background 08/2009 Ph.D., Information and Communications, Gwangju Institute of Science and Technology (GIST), Republic of Korea 02/2005 Ms., Information and Communications, GIST, Republic of Korea 06/2002 Bs., Applied Physics, Vietnam National University, Hanoi, Vietnam Professional Experiences 07/2014 - present 07/2011- 07/2014

Research associate and Chief Investigator, IPAS, UoA, Adelaide, Australia Australian Research Council (ARC) Super Science Research Fellow, IPAS, UoA, Adelaide, Australia 2/2010 - 07/2011 Postdoctoral Research Fellow, Electron Science Research Institute (ESRI), Edith Cowan University, WA, Australia 09/2009 - 01/2010 BK21 Postdoctoral Researcher, GIST, Republic of Korea

Field of Research ➢ ➢ ➢ ➢ ➢

Optical Fiber Technologies Optical Fiber sensing Optical communications Micro and nano-engineered optical fiber Biochemical sensing

Memberships ➢ IEEE Research outcome Linh’s research has led to 28 technical papers and conference proceedings with approximately 400 citations, including invited papers, and generated approximately 1 million AUD in research income (cash).

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Biochemical sensing with microstructured optical fibers Linh Viet Nguyen1,*, Stephen Warren-Smith1, Kelly Hill2, Erik Schartner1 and Heike Ebendorff-Heidepriem1,2 1

Institute for Photonics and Advanced Sensing, The University of Adelaide, Adelaide, SA 5005, Australia; 2 South Australian Research and Development Institute, 2b Hartley Grove, Urrbrae, SA 5064, Australia; 3 ARC Centre of Excellence for Nanoscale Biophotonics, The University of Adelaide, Adelaide, SA 5005, Australia; *Email: [email protected]

Optical fibers have traditionally found use in carrying optical communications signals over very long distances. This fundamental technology has given birth to the Internet that has transformed how mankind works, communicates and entertains. This rapid communication is achieved essentially because the signal is well isolated from the surrounding environments, leading to extremely low optical losses, and long transmission distances. In recent years, optical fibers have also been finding applications in sensing, particularly in biochemical sensing. In this domain, as opposed to signal transmission optical fibers, it is essential that optical signal strongly interacts with the environment to enable high sensitivities. This paper describes several specialty optical fiber designs a for biochemical sensing, by allowing direct interaction of the light propagating in the fiber core with the environment. Optical transduction techniques based on the proposed microstructured optical fibers such as multimode interference effects, fiber Bragg gratings, fiber micro cavites, excitation and collection of fluorescence using fibers, or Raman scattering based sensing, as well as functionalization strategies for realizing both label and label-free biochemical sensing with our in-house developed microstructured optical fibers. The fiber sensor platform offers numerous advantages including low sample volumes, high sensitivities at low cost. Figure 1 (a) SEM image of an suspended core fiber, (b) SEM image of an exposed core fiber (ECF), (c) Dual molecular beacons immobilized on SCF, (d) Bragg grating on ECF, (e) Ultra small Fabry Perot cavity on tapered fiber tip (f) SEM image of a hollow core fiber for Raman based sensing, (g) functionalized fiber pH probe for cancer detection and (h) Fiber probe for in-vivo sensing of brain temperature.

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D1-Inv. 01 Prof. Shin-Won Kang (Ph.D.) School of Electronics Engineering, College of IT Engineering, Kyungpook National University, 1370 Sankyuk-dong, Bukgu, Daegu, Republic of Korea. Tel: +82-53-950-6829 Fax: +82-53-950-7932 E-mail: [email protected] Educational background 7/1993 Ph.D., Biomedical Engineering, Keio University, Tokyo, Japan 8/1980 Master, Electronic Engineering, Yeungnam University, Daegu, Republic of Korea Professional Experiences 3/1994 - Present 9/2009 - Present 1/2012 - 12/2012 1/2013 - Present 3/2015 - Present

Full Professor, School of Electronics Engineering, College of IT Engineering, Kyungpook National University, Republic of Korea Chief Director, Center for Functional Devices Fusion Platform, Kyungpook National University President, The Korean Sensors Society Honorary President, The Korean Sensors Society Chief Director, Institute of Semiconductor Fusion Technology Kyungpook National University

Field of Research ➢ Interdigitated capacitor (IDC) based electronic tongue, nose, and biosensor ➢ Fiber-optic volatile organic compounds (VOCs) detectors, optoelectronic nose, tongue, Intergrated optical sensor, and Semiconductor sensor ➢ Nanocrystal Quantum Dots (QDs) Display & Memory ➢ Organic Solar Cells and UV/SWIR photodetector Memberships ➢ ➢ ➢ ➢ ➢

The Korean Sensors Society The Korean Physical Society The Korean Information Display Society Optical Society of Korea IEEE Member

Research outcome He is the author of more than 230 scientific articles published in reputed journals and over than 500 well known international conference proceedings.

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Development of Fast and Highly Sensitive Interdigitated Capacitor Based Taste Sensor Array Md. Rajibur Rahaman Khan, Shin-Won Kang* School of Electronics Engineering, Kyungpook National University, 80 Daehakro, Bukgu, Daegu 41566, South Korea. Email: [email protected]

In our study, we proposed an interdigitated capacitor (IDC) based taste sensor array/electronic tongue (e-tongue) to detect different types of tastes, such as sweetness (glucose), saltiness (NaCl), sourness (HCl), bitterness (quinine-HCl), and umami (monosodium glutamate). The operation of the proposed taste sensor array is based on the capacitance variation principle as the taste solution comes into contact with the taste sensitive sensing membrane of the IDC sensing element of the taste sensor array. Four different types of solvatochromic dyes, such as Nile red, Reichardt’s dye (R-dye), Auramine-O, Rhodamine-B, as well as four different types of lipids, as for example oleic acid (OA), dioctylphosphate (DOP), trioctylmethylammonium chloride (TOMA), and oleylamine (OAm) containing polymer sensing membrane were individually deposited into the eight interdigitated electrodes by a spin coater to prepared eight different kinds of IDC taste sensing elements of the taste sensor array. The proposed IDC taste sensor array offer a high sensing ability over a wide taste measurement range about 1 µM to 1 M. The sensitivity of the proposed IDC taste sensor array for glucose solution was approximately 1.45 nF/decade with a linear sensing performance with the correlation coefficient, R2 = 0.998. The response and recovery times of the proposed taste sensor array were approximately 6 s and 5 s, respectively. The proposed IDC taste sensor array/e-tongue has several other advantages, such as easy to fabricate, low cost, real-time monitoring capabilities, good reproducibility performance, high sensing stability with a standard deviation of about 0.021 and compactness. The performance of the proposed IDC e-tongue was compared with the potentiometric, cascoded compatible lateral bipolar transistor (C-CLBT), and fiber-optic-based taste sensing systems with respect to dynamic range width, response time, sensitivity, and linearity. We found that the proposed e-tongue has better sensing performance than the mentioned sensors. Finally, in our study, we applied principal component analysis (PCA) to distinguish between various kinds of taste in mixed taste compounds. Acknowledgements This study was supported by the BK21 Plus project funded by the Ministry of Education, Korea (21A20131600011), the National Research Foundation of Korea (NRF) Grant funded by the Korean Government (MSIP) (No. NRF 2014R1A2A1A11050377), and Samsung Electronics.

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Figure 1. Sensing performance of the proposed IDC taste sensor array: (a) Capacitance variation with respect to different concentration of glucose solution and (b) linearity.

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D1-Inv. 02 Professor Maria Teresa Seabra dos Reis Gomes Department: Chemistry, University of Aveiro, Portugal Research group: Environ. Processes and Pollutants Phone: +351 234370722 E-mail: [email protected] http://www.cesam.ua.pt/mtgomes Professional Carreer: 2000 - Present Associate Professor, Department Chemistry, University of Aveiro 1997-2000 Assistant Professor, Department Chemistry, University of Aveiro 1989 - 1997 Teaching Assistant, Department of Chemistry, University of Aveiro 1984 - 1989 Trainee Teaching Assistant, Department of Chemistry, University of Aveiro 1983 - 1984 Trainee Teaching Assistant, University of Beira Interior Scientific Interests: • Chemical Sensors • Analytical Chemistry

Brief CV After a degreee in Chemical Engineering at the University of Coimbra (1983), she became a teacher assistent. In 1989 she presented the lesson "Stochastic Methods in the simulation of experiments in chemical kinetics" and a scientific review on " quantitative analysis by mass spectrometry" for a public evaluation of pedagogical and scientific capabilities. In 1997 she obtained a PhD in Chemistry with the thesis "Development of sensors based on piezolectric quartz crystals for CO2 and SO2 ". This work marked the begining of the development of chemical sensors at the Chemistry Department, which became, since then, her major field of research. At the present, she is a member of the permanent comitee of the sensors forum IBERSENSOR and is a vowel of the centre regional college of Chemical and biological engineer of the Ordem dos Engenheiros

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Evaluation of VOC’s emitted from historic papers using a non-destructive approach: an electronic nose based on acoustic wave sensors Marta I.S. Veríssimoa,b, José A.F. Gamelasb, Dmitry Evtyuginb, M. Teresa S.R.Gomesa* a b

CESAM &University of Aveiro, 3810-193 Aveiro, Portugal CICECO &University of Aveiro, 3810-193 Aveiro, Portugal *E-mail: [email protected]

Cultural heritage is irreplaceable and generations are responsible for its preservation. The identification of early signs of material degradation is mandatory for effective preventive conservation. However, sampling restrictions in the analysis of cultural heritage materials limits the choice of the appropriate analytical method. Analytical techniques solvent free and with nondestructive sampling are preferred. Volatile organic compounds (VOCs) are the source of what is referred as the smell of books. Besides, they are important indicators of the conditions of historic books, and specific VOC markers have been related to cellulose degradation. A new electronic nose, composed of bulk acoustic wave sensors sensitive to VOCs identified as markers of cellulose origin and those connected to cellulose degradation is presented. Fig.1 shows the six port valve that distributes the gaseous sample to six mass sensors, each one with a different recognition layer, along with the sensors responses. A flow injection methodology was used. A nitrogen carrier flow transported the desorbed compounds from an SPME fibre, initially left in contact with the book atmosphere, and used to concentrate the VOCs evolved from the paper.

Figure 1. Electric nose composed of 6 sensors connected to the sample distribution valve, and the responses of the array of sensors to the volatile compounds extracted from a 1878 book.

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D2-Inv. 01 Professor Sungjin Kim School of Advanced Materials and Engineering Kumoh National Institute of Technology Korea, south E-mail: [email protected]

Education and Carrier Mar. 1979 – Feb. 1987, Ph. D. Metallurgical Engineering, Sung KyunKwan University, Korea

Research Experience  Synthesis technologies of TiO2 based photocatalystic powders under visible light (Nitrogen, nitrogen and Iron codoped TiO2/transition metal doped TiO2).  Gas sensors of ZnO/TiO2/WO3 based powders with double junction  Extensive knowledge of transition metal doped nano-TiO2 tube for hydrogen generation and synthesis of methanol and urea using doped TiO2 and WO3  Research in (1) powders and rods of electrode: transition metal doped TiO2 and ZnO electrode, (2) tubes: metal doped nano-TiO2 tube and membrane.  Research in VO2/TiO2 junction for thermochromism materials.  Perovskite PV for wearable device and hydrogen generation.

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Growth of Heterostructured Bi2O3–ZnO Photocatalyst and Its Enhanced Photocatalytic Activity Eadi Sunil Babu, Sengeragchaa, Bolortuya, Azimov Farkhod, Min Ji Hong, Yong Sik Kim, Hee Jun Kim, Young Hwa Woo, Sungjin Kim* School of Advanced Materials & Engineering, Kumoh National Institute of Technology 61, Daehak-Ro, 39177, Gumi, Korea.. Email: [email protected] In this study, photocatalytic degradation studies of Rhodamine B using heterostructured Bi2O3–ZnO nano-composite under visible light irradiation is reported. Bi2O3–ZnO nano-composite nanoparticles are prepared by simple hydrothermal method. The prepared nano-composite are characterized by X-ray diffraction studies, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption the Brunauer–Emmett–Teller (BET) measurements. The photocatalytic degradation of Rhodamine B using Bi2O3–ZnO nano-composite are investigated with different concentration of solution, and amount of catalyst and the results are discussed. Keywords:

Bismuth Oxide, Zinc Oxide, Hydrothermal, Photocatalysts, Rhodamine B Dye

Acknowledgment: This work was supported by the Research Funding by Kumoh National Institute of Technology. We would like to acknowledge and thank for the funding of WC 300 Project partially supported by Business for global cooperative R&D funded by Korea Small and Medium Business Administration in 2015. We would like to acknowledge and thank for the funding of Project – 10063553 partially supported by MOTIE in 2016.

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D2-Inv. 02 Professor: Manabu Tokeshi PhD. in Engineering, Division of Applied Chemistry Faculty of Engineering, Hokkaido University, Japan Office: +81-117066744 Email: [email protected] Educational background 3/1997 Ph.D, Department of Molecular Sciences and Technology, Kyushu University, Japan 7/1994 Master, Department of Molecular Sciences and Technology, Kyushu University, Japan Professional Experiences 11/2011-present 9/2011-3/2012 12/2005-10/2011 11/2004-11/2005 1/2004-10/2004 4/1999-12/2003 4/1998-3/1999 4/1997-3/1998

Professor, Division of Applied Chemistry, Hokkaido University, JAPAN Visiting Researcher, Swedish Medical Nanoscience Center, Karolinska Institute, SWEDEN Associate Professor, Department of Applied Chemistry, Nagoya University, JAPAN President, Institute of Microchemical Technology, Co. Ltd., JAPAN Group Leader, Kanagawa Academy of Science and Technology, JAPAN Sub-Leader, Kanagawa Academy of Science and Technology, JAPAN Researcher, Kanagawa Academy of Science and Technology, JAPAN JSPS Postdoctral Fellow, The University of Tokyo, JAPAN

Field of Research ➢ μ-TAS ➢ Lab on a Chip ➢ High sensitive detection Memberships ➢ ➢ ➢ ➢

American Chemical Society Chemical Society of Japan The Japan Society of Analytical Chemistry The Society of Chemistry and Micro-Nano System

Research outcome The author or co-author of 175 scientific papers, 36 book chapters, 87 reviews, and 149 proceedings related to μ-TAS applications and high sensitive detection.

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Fluorescence Polarization Measurement System for Multi-Sample Immunoassay Manabu Tokeshi Division of Applied Chemistry, Hokkaido University, Japan, and ImPACT Research Center for Advanced Nanobiodevices, Innovative Research Center for Preventive Medical Engineering and Institute of Innovation for Future Society, Nagoya University, Japan; Email: [email protected]

Fluorescence polarization (FP) is a versatile solution-based method that enables the study of molecular interactions such as protein-protein, protein-DNA, and protein-ligand binding interactions. Since this method is rapid and easy to implement, it is used in clinical and biomedical applications. In particular, fluorescence polarization immunoassay (FPIA) that combines FP and competitive immunoassay is a well-established technique for monitoring of therapeutic drugs in the blood and quantitative analysis of drug residues in foods. In the FP measurement, P is determined by the following equation: P = (I‖ - I) / (I‖ + I) where I‖ and I are fluorescence intensity with parallel and perpendicular polarizations to the excitation plane, respectively. Therefore, to obtain P value, we have to measure I‖ and I separately. A combination of polarizer and rotating polarizer or a polarizer and polarizing beam splitter is usually used for those measurements. In order to measure multiple samples, it is necessary to scan the optical component including those polarizers or to scan the samples. Recently, we developed a unique FP measurement system based on the synchronization between the orientation of the liquid-crystal molecules of a LC display and the sampling frequency of an image sensor to realize simultaneous FP analysis of multi-samples (Figure 1) [1]. The feature of our system developed here is to be able to acquire a 2D image of FP. By this feature, FP of multipe samples on the image can be acquired simultaneously. Using the system, we demonstarated the multisample FPIA of prostaglandin E2. Reference 1. O. Wakao et al., Anal. Chem., 2015, 87, 96479652. Figure 1 Experimental setup for FP measurements.

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D3-Inv. 01 Professor: Hiroshi Ishida PhD. in Electrical and Electronic Engineering, Graduate School of Bio-Applications and Systems Engineering Tokyo University of Agriculture and Technology, Japan Office: +81-42-388-7420 Email: [email protected] Educational Background 3/1997 Ph.D, Electrical and Electronic Engineering, Tokyo Institute of Technology, Japan 3/1994 Master, Electrical and Electronic Engineering, Tokyo Institute of Technology, Japan Professional Experiences 1/2017-present 4/2004-12/2016 8/2000-3/2004 10/1998-8/2000 4/1997-9/1998 Field of Research ➢ ➢ ➢ ➢

Professor, Tokyo University of Agriculture and Technology, Japan Associate Professor, Tokyo University of Agriculture and Technology, Japan Research Associate, Tokyo Institute of Technology, Japan Postdoctoral Fellow, Georgia Institute of Technology, USA Research Associate, Tokyo Institute of Technology, Japan

Autonomous mobile robots for gas sensing applications Underwater robots that mimics olfactory search behavior of animals Active chemical sensing systems Olfactory displays

Memberships ➢ IEEE ➢ ISOCS (International Society for Olfaction and Chemical Sensing) Research Outcome He is well known as a pioneer in the field of mobile robot olfaction. He has developed various types of robotic sensing systems for chemical source localization and chemical distribution mapping.

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Mobile Robot Olfaction: Using Actively Generated Airflow to Enhance Chemical Reception Hiroshi Ishida Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Japan; Email: [email protected]

Mobile robots can be used as moving platforms for various gas sensing tasks in the field. In the presentation, it will be shown that actively generated airflow can be used to facilitate such robotic gas sensing tasks. For example, a robot equipped with a suite of gas sensors can be used to monitor methane emission in landfill sites. The robot can bring the sensors to specified locations and autonomously collect sensor data to assess the total amount of methane emission in a landfill site. Although most of the gas sensing robots reported so far are wheel based, a multirotor drone appears to be a promising platform for gas sensing applications because of its high maneuverability. However, strong airflow generated by a drone when it flies poses a serious problem. As shown in Scheme 1(a), a multi-rotor drone generates a strong airflow in the downward direction. This airflow spreads radially after impinging on the ground. Therefore, any gas wafting near the ground is blown away from the drone and is not detected by the gas sensors placed on the drone. However, we can utilize this problematic airflow if we can somehow guide it in a preferable way. Suppose that two quadcopters are connected by a rod (or a string) as shown in Scheme 1(b). If the two quadcopters are flying side by side, the airflows spreading from the two quadcopters along the ground impinge with each other and are deflected upward from the ground. If a gas sensor is attached at the midpoint of the rod, the airflows generated by the quadcopters bring gas samples from the surface of the ground to the gas sensor in the mid air. Thus, the quadcopters flying over the ground can detect the presence of gas wafting near the ground surface. Experimental results are presented to show the soundness of this idea. One of the problems in using airflows for collecting gas samples is that the target gas is always diluted while being transported by the airflow. However, this problem can be alleviated to some extent by using a preconcentrator system together with a gas-sensing device. This work was supported in part by JSPS KAKENHI Grant Numbers 25289055, 15K13997, and 17K19964. (A)

(B)

Scheme 1 (A) Schematic diagram of the airflow field generated by a single quadcopter; (B) schematic diagram of the airflow field generated by two connected quadcopters.

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D3-Inv. 02 Professor: Chih-Ting Lin Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan Office: +886-2-33669603 Email: [email protected] Educational background 7/2006 Ph.D, Electrical Engineering and Computer Science, University of Michigan, Ann arbor, Michigan, U.S.A. 1/2003 Master, Electrical Engineering and Computer Science, University of Michigan, Ann arbor, Michigan, U.S.A. Professional Experiences 08/2016-present 08/2012-07/2016 10/2006-07/2001

Professor, Department of Electrical Engineering, National Taiwan University Associate Professor, Department of Electrical Engineering, National Taiwan University Assistant Professor, Department of Electrical Engineering, National Taiwan University

Field of Research ➢ ➢ ➢ ➢ ➢ ➢

Silicon-based biosensors Inkjet-printable organic electronics High-k organic dielectrics Graphene devices and applications Electrochemical biosensing technologies Electrokinetic microfluidics

Memberships ➢ ➢ ➢ ➢

Association of Chemical Sensors in Taiwan IEEE Electro-Chemical Society American Chemical Society

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CMOS-based Biomolecular Diagnosis Technologies Chih-Ting Lin Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan E-mail: [email protected]

Growing with modern societies, healthcare paradigms have been shifted from centralized hospitals to local-distributed clinics. At the same time, blooming consumer electronics envision potentials of convenient and personalized lives. As a consequence, it is intriguing to harness momentums of electronics for next-generation affordable healthcare technologies. In-vitro diagnosis (IVD) is essential in diagnosis and prognosis and its market size is around billions of dollars. Aside from traditional electrophysiological diagnoses, e.g. EEG and ECG, IVD is one of key candidates, which can be promoted by ICT, for future personalized healthcare technologies. To address this vision, we have developed a series of complementary metal-oxidesemiconductor (CMOS) based bimolecular analysis chip technology. Taking advantages of COMS-compatible characteristics, the developed bio-sensor-on-chip (BSoC) has demonstrated capabilities to be monolithically integrated with analog interface circuits, digital process circuits, and wireless transceiver circuits. Since CMOS technology has capabilities of low cost and mass production, this result shows potentials to employ the developed BSoC technology for future consumer bioelectronics in different applications, such as personal healthcare management and on-site diagnosis in clinics. Therefore, we believe a CMOS based handheld device for cardiac biomarkers is promising and has great market potential in both diagnosis and prognosis.

Scheme 1 Schematic of CMOS-based biomolecular diagnosis technologies

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E1-Inv. 01 Professor: Eiichi Tamiya Nano-bioenginneing and Biosensor Lab. Department of Applied Physics Photo Graduate School of Engineering Osaka University 2-1 Yamadaoka, Suita, Osaka 565-0871 Japan Phone: +81-6-6879-4087 Fax: +81-6-6879-7840 E-mail: [email protected] Web URL: http://dolphin.ap.eng.osaka-u.ac.jp/nanobio/ Education: 1980 B.Sci. in Chemistry, Faculty of Science, Osaka University 1982 M.S. in Science and Engineering, Graduated School, Tokyo Institute of Technology 1985 Ph.D. in Science and Engineering, Graduated School, Tokyo Institute of Technology Professional career: 1985-1987 Assistant Professor, Tokyo Institute of Technology 1987-1988 Associate Professor, Tokyo Institute of Technology 1988-1993 Associate Professor, The University of Tokyo 1993-2007 Professor, Japan Advanced Institute of Science and Technology 2007-present Professor, Osaka University 2017-present Executive director, Photonics Center, Osaka University Director, AIST-Osaka University Advanced Photonics and Biosensing Open Innovation Laboratory Research projects: 1. Biochips and Biosensors 2. Nanotechnology based bioscience and bioengineering 3. Biomass energy conversion systems 4. POC (point-of-care) biosensors for medical diagnosis, food safety and environmental protection 5. Cell based chips for tissue and stem cell engineering Honors and awards: 1. Progressive Award for young researchers (The Chemical Society of Japan, 1989) 2. Industrial Collaboration Promotion Award (Ishikawa Prefecture,2000) 3. New technology and production Award (Small and Medium Enterprise Agency, 2001) 4. Ichimura Academic Award (The New Technology Development Foundation, 2005) 5. Invention Encouragement Award of Minister of Education, Culture, Sports and Science (2010) 6. Osaka University Presidential Awards for Achievement (2014) 7. Nakatani Award (Gland Prix), Nakatni Foundation (2016)

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Electrochemiluminescence biosensors for high sensitive medical diagnosis and rapid antioxidants detection Eiichi Tamiya*1,2 *1 *2

Department of Applied Physics, Graduate School of Engineering, Osaka University

AIST-Osaka University Advanced Photonics and Biosensing Open Innovation Laboratory, Photonics Center, Osaka University 2-1, Yamadaoka, Suita, Osaka 565-0871, Japan

Abstract In this review paper we present the luminol based electrochemiluminescence (ECL) biosensors which perform enzymatic reaction and bioanalysis linked with antioxidant molecules by controlling spatiotemporal production of luminescent substrate, catalase activity and glycated albumin(GA). The ECL intensity depends on the antioxidant capacity because the radicals are neutralized by the antioxidants, suppressing the luminous reaction. An antioxidant capacity of beverages (22 types) was evaluated by comparing with the standard curve of Trolox. The time necessary for the ECL measurement of antioxidant capacity is only two minutes with screen printed electrodes and a portable ECL measurement system. Our system was also applied to monitoring reactive oxygen species released from neutrophils which played important role of biological defense mainly against virus and bacteria infection. The quenching of ECL imaging by catalase reaction localized in the multi-chamber electrode using electro-generated substrate was examined for a potential candidate for sensitive reporter system. The substrate was successfully generated at applied potential between -1 to -0.4 V in multichamber electrodes and the substrate confinement within the chamber was observed up to 60 seconds generation time. The microchamber electrode system demonstrated detection limit of 90 fM catalase. We also demonstrated the detection limit of 0.1 μM GA in human serum albumin, which has seen improvement of about 70 times more than the colorimetric methods. We have proposed a platform that performs enzymatic reaction and bioanalysis linked with antioxidant molecules by controlling spatiotemporal production of luminescent substrate, catalase activity, glycated albumin. We also showed a novel measurement system that performs digital biomolecular analysis by linking microfluidic control chip technology and ECL system.

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E1-Inv. 02 Professor: Chao Sung Lai Chang Gung University, Taoyuan · Department of Electronic Engineering No. 259, Wenhua 1st Road, Guishan District, Taoyuan City, Taiwan 333 Tel:+886-3-2118800 ext 5786, Email: [email protected] Education: 1991: B.S. Electronic Engineering, National Chiao Tung University, Taiwan 1996: Ph.D. Electronic Engineering, National Chiao Tung University, Taiwan Transistor Based Biosensors and its Applications Chao-Sung Lai1,2 1 Department of Electronic Engineering, Chang Gung University, Taiwan 2 Department of Nephrology, Chang Gung Memorial Hospital, Taiwan Integrated Circuit (IC) manufacturing is a matured industry in Asia-Pacific. For the transistors, one of the possible applications for next generation is bio-sensors. The Ion Sensitive Filed-Effect Transistor (IS-FET) and extended gate (EG) FETs were well developed and demonstrated. In this talk, full integration viewpoints including material, device structure, sensing membrane, measurement system and clinical study will be introduced. Silicon based nanowire and new 2D materials contributes more possibilities for high quality of biosensors. Moreover, the clinical study by transistor based biosensors are successfully demonstrated on the diagnostics for bladder cancer, cervical cancer and ovarian cancer and so on. A programmable EIS structure was fabricated with silicon oxide (SiO2)/silicon nitride (Si3N4)/silicon oxide on a p-type silicon wafer, namely electrolyte-oxide-nitride-oxide-Si (EONOS). Overall, it has been proven that the voltage program on the nonvolatile memory-like structure of EONOS is a notable candidate for genosensor development, scoping the diagnosis of a single nucleotide polymorphism (SNP)-related disease. 1,2,3) Keywords: Ion Sensitive Filed-Effect Transistor (IS-FET), extended gate (EG) FETs, nanowire, 2D materials, bladder cancer, cervical cancer, ovarian cancer, vascular endothelial growth factor (VEGF). References: 1) Yi-Ting Lin et al. Biosensors and Bioelectronics, 79, 63 (2016): 2) Agnes Purwidyantri et al. Sensors and Actuators B: Chemical, 92, 217 (2015); 3) Kuan-I Ho et al. Advanced Materials, 27, 6519 (2015); 4) Hsiao-Chien Chen et al. Analytical Chemistry, 86 (2014, Mar), Pages 9443-9450

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E2-Inv. 01 Dr. Matteo Tonezzer PhD. in Physics, Institute of Materials for Electronics and Magnetism (IMEM) Italian National Research Council (CNR), Italy Office: +39-0461-314828 Email: [email protected] Educational background 11/2011 Ph.D, Physics, Trento University, Italy 3/2008 Master, Physics of the Matter, Trento University, Italy Professional Experiences 10-11/2013 11/2011-present 6-7/2009 2/2006-2/2009 2/2002-2/2006

Visiting Researcher, Georgia Institute of Technology, USA Nanofabrication Expert, Institute of Materials for Electronics and Magnetism (IMEM), ITALY Marie Curie Fellow, Ecole Polytechnique Fédérale de Lausanne (EPFL), SWITZERLAND Nanofabrication Expert, Institute for Photonics and Nanotechnologies (IFN), ITALY Clean Room Technician, Institute for the Physics of Matter (INFM), ITALY

Field of Research ➢ Nanowires growth mechanisms ➢ Chemo-resistive gas sensors ➢ Nanostructured metal oxides (SnO2, ZnO, CuO, NiO WO3, TiO2 etc.) ➢ Organic quasi-crystalline ultra-thin films by Supersonic molecular beams ➢ Hybrid nanomaterials and devices Awards 5/2011 Young Scientist Award by European Materials Research Society (EMRS) Research outcome He participated in 13 national and international research projects, and was principal investigator for 3 of them. He is author of some dozens of papers on international journals and contributed, also with invited talks, to tens of international conferences. He is reviewer for 39 international peer-review journals (editor for 5 of them), organizer and chairman of 6 international conferences.

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How to get multiselectivity from resistive gas sensors based on nanostructured metal oxides Matteo Tonezzer Institute of Materials for Electronics and Magnetism (IMEM), Italian National Research Council (CNR), Italy; Email: [email protected]

Detection of volatile compounds is nowadays important in a broad variety of applications. Metal oxide gas nanosensors are tiny, cheap devices that can be integrated in any application, but unfortunately they lack of selectivity. On the other hand, electronic noses consisting in sensors arrays comprising different active materials are complex and expensive to fabricate and use. In this presentation we introduce two different approaches using nickel oxide polycrystalline nanowires at different working temperatures in order to achieve multi-selectivity. In one case we create a virtual sensors array exploiting the thermal fingerprints of different gases, while in the other we encode the different response of a specific gas in a RGB signal. With only one nanostructured material (NiO) and 3 or 5 temperature values, both systems are able to qualitatively discriminate 7 different reducing gases. The sensor is stable and fast (response and recovery times are usually less than 20 seconds) and can selectively detect which gas is present, with an accuracy of 100%. One of the two approaches allows also to distinguish the gas concentration with an error lower than 15%. Our results show that single metal oxide resistive nanosensors could achieve real selectivity exploiting thermal fingerprints or RGB encoding from a temperature gradient.

Figure 1 Visual response of the NiO nanosensor to different gases at different concentrations.

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E2-Inv. 02 Professor: Geyu Lu State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012, China Email: [email protected] Biography Prof. Geyu Lu received his BS and MS degrees from Department of Electronic Science, Jilin University, China in 1985 and 1988, respectively, and received Dr. of Eng. from Department of Materials Science and Technology, Graduate School of Engineering Sciences, Kyushu University, Japan in 1998. Between 1988 and 1994, he was a lecturer in Department of Electronic Science, Jilin University, China. From 1998 to 2006, as a senior research scientist, he developed gas sensors and gas alarms in Yazaki Meter Co. Ltd. He has been a professor at the College of Electronic Science and Engineering, Jilin University since 2006. His research field includes Chemical sensors (gas sensors based on semiconducting oxides, solid electrolytes, polymers and catalysts, humidity sensors), sensor systems and smart instruments, nanomaterials, as well as dye sensitized solar cell. He obtained some awards including China National Outstanding Youth Science Funds (2006), Scientific and Technological Progress Prize of Ministry of Machinery (1997), Scientific and Technological Progress Prize of State Education Commission (1991) and Significant Achievement Rewards of State Science and Technology Commission (1990). He has published 110 peerreviewed papers.

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High performance gas sensors based on mesoporous semiconducting oxides Geyu Lu*, Yuan Gao*, Yinglin Wang, Qiuyue Yang State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012, China Email: [email protected]

Gas sensors based on mesoporous metal oxides have drawn a great deal of attention for its unique structure and high performance. Mesoporous metal oxide has interconnected porous structure and great specific surface area, which provide more active sites and facile gas diffusion path. These virtues are beneficial for full utilization of sensitive materials. The mesoporous metal oxides were prepared by soft/hard template, such as SnO2, WO3, In2O3, and ZnFe2O4. The obtained materials showed ordered mesoporous structure with excellent crystallinity and uniform pore size. In addition, the strategies of aliovalent ion doping and noble metal decorating were employed to further improve sensing properties of mesoporous semiconducting oxide. Aliovalent ion doping modulated carrier and adsorbed oxygen density, and noble metal possessed catalytic activity and electronic sensitization effect, which all promote the recognition function and transformation function of sensitive matrix. Zr and Ni were adopted for aliovalent ion doping into In2O3 lattice. Noble metal (Ag/Au/Pt) were impregnated on mesoporous WO3. Moreover, we designed a pulsedriving mode that provided two operating temperature levels for mesoporous material to elevate sensitivity. Adsorbing more gases on mesoporous materials at low temperature, and then detecting at high temperature. Gas sensors based on the above strategies presented excellent properties.

Figure 1. TEM images and gas-sensing properties of mesoporous metal oxide.

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E3-Inv. 01 Professor: C. Gomez-Yanez Department of Materials and Metallurgical Engineering Instituto Politecnico Nacional Tel: +5255-57296000 Ext 54208 Mexico City, DF, Mexico Email: [email protected] https://www.researchgate.net/profile/Carlos_Gomez-Yanez

Defect chemistry in ferroelectric materials M. C. Martínez-Morales1 , F. Ambriz-Vargas, L. Lartundo-Rojas2, J. Ortiz-Landeros1 and C. Gomez-Yanez1 1

Department of Metallurgical and Materials Engineering Center of Nano Sciences and Micro and Nano Technologies Instituto Politécnico Nacional, U. P. Adolfo López Mateos, Zacatenco, 07738, Mexico city, Mexico 2

Abstract: Many sensors and other devices are built taking advantage of ferroelectric properties. Bismuth titanate (Bi4Ti3O12 or BiTO) is known for its high resistance to dielectric fatigue and relatively large remnant polarization when doped with La. BiTO is also known to be a potential ionic conductor. In both applications, crystalline defects play an important role. In this work, a standard thermochemical equilibrium procedure is used to analyze defect chemistry in BiTO. The results indicate a strong oxidized state. To obtain a reduced condition, extremely low oxygen partial pressures and high temperatures have to be achieved. Even at normal conditions, results show a relatively high concentration of holes, which is in agreement with the p-type leaking experimentally observed, relatively high concentration of oxygen vacancies, which suggest the potential application of BiTO as ion conductor, and relative high concentration of bismuth vacancies, in accordance with the known problem of bismuth volatilization observed during the processing of this material. To verify these calculations, some spectroscopic characterization technics have been used as well as electrical conductivity at high temperature. Also, the influence of point defects on ferroelectric and dielectric properties of BiTO is reported. Keywords: Defect chemistry, ferroelectrics, bismuth titanate

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E3-Inv. 02 Ultrasensitive acetylcholine sensor based on the electron transfer promotion on electrochemically activated graphene electrodes Vu Thi Thu1,2,7, Nguyen Van Quynh1, Dau Thi Ngoc Nga1, Bui Quang Tien3, Ly Cong Thanh3,4, Dang Thi Thu Huyen5, Vu Van Hung1, Do Thi Thuy1, Nguyen Thu Tuyet1,4, Phan Van Thang1,4, Nguyen Nguyet Minh1, Bui Thi Thu1,5, My Ngoc1,5, Cao Thi Thanh6, Nguyen Van Chuc6, Tran Dai Lam2,3,8 1

University of Science and Technology of Hanoi (USTH), Vietnam Academy of Science and Technology (VAST), 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam 2 Center for High-Technology Development (HTD), Vietnam Academy of Science and Technology (VAST), 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam 3 Graduate University of Science and Technology (GUST), Vietnam Academy of Science and Technology (VAST), 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam 4 Hanoi University of Pharmacy, 13-15 Le Thanh Tong, Hoan Kiem, Hanoi, Vietnam 5 Hanoi Pedagogical University 2, Nguyễn Văn Linh, Xuan Hoa, Vinh Phuc, Vietnam 6 Institute of Materials Science (IMS), Vietnam Academy of Science and Technology (VAST), 18 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam 7 E-mail: [email protected]; 8E-mail: [email protected]

An amperometric acetylcholine biosensor based on electrochemically activated graphene sheet has been developed. The biosensor was constructed with a CVD-grown graphene sheet (double-layers) at the bottom, a very thin film of conducting polyaniline (~ 80 nm) at the middle, and acetylcholinesterase (20 U) on the top. The electron transfer promotion was enabled by cycling graphene sheet in one electroactive solution. The results reveal that the current response was increased at least 20 times after activating the carbonaceous layer. We do believe that this signal enhancement is rooted from the electrochemical reduction of funtional groups containing oxygen naturally existed on grown graphene material. Also, the incorporation of electroactive species into this carbonaceous nanomaterial might have provided invisible shuttles that accerlerate electron transfer on the electrode surface. The biosensor could detect acetylcholine in the linear range from 12.5 μM to 187.5 μM. The proposed biosensor could restore over 80% of its original current, which demonstrated good reactivation of enzyme. Thus, the development of this biosensor will probably provide a promising tool for analysis of acetylcholine inhibitors such as pesticides and neurotoxins. Keywords: Acetylcholine, neurotoxins, graphene, electrochemical biosensors, activation.

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Fig 1. Configuration of acetylcholinesterase sensors

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Fig 2. Current responses of acetylcholinesterase sensors

References: [1]. S. M. Tan, A. Ambrosi, C. K. Chua, M. Pumera, J. Mater. Chem. A, 2014, 2, 10668. [2]. S. Kurbanoglu, S. Ozkan, A. Merkoci, Biosens. Bioelectron., 2016, 89, 886. [3]. H. Shimada, S. Noguchi, M. Yamamoto, K. Nishiyama, Y. Kitamura, T. Ohara, Anal. Chem., 2017, 89, 5742. [4]. D. M. Subbiah, N. Nesakumar, A. J. Kulandaisamy, J. B. B. Rayappan, Sens. Actuators B, 2017, 248, 708. Acknowledgements: This work was supported by VAST.DLT.01/17-18, AGRI-SENS1 and HTD.CS.02/17.

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Oral Section

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A1-Oral-01 Effect of Zinc Oxide Morphology on the Carbon Monoxide Sensing Properties Ni Luh Wulan Septiania,b, Yusuke Yamauchic,d, Yusuf Valentino Kanetic, Brian Yuliartoa,b*, Nugrahaa,b, Hermawan K Dipojonoa,b a

Advanced Functional Materials Laboratory, Engineering Physics, Institut Teknologi Bandung, Ganesha 10, Bandung 40132, Indonesia b Research Center for Nanoscience and Nanotechnology, Institut Teknologi Bandung, Jl. Ganesha10, Bandung 40132, Indonesia c International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan d Australian Institute for Innovative Materials (AIIM) University of Wollongong, North Wollongong, NSW 2500, Australia *Email: [email protected]

Carbon monoxide is highly dangerous gas that can threat human health. Its properties which are colorless and odorless make it very hard to be detected by human. Hence, decreasing human health due to its concentration in atmosphere must be avoided by gas sensor. Zinc Oxide or ZnO is one of metal oxide semiconductor which has high potential to be used as gas sensor because it has high sensitivity and controllable morphology. Its properties can change significantly when interact with toxic gas. In this research, morphology of ZnO was varied by varied the concentration of hexamethylenetetramine (HMTA) during synthesize. ZnO powder was synthesized by solvothermal method. X-Ray Diffraction (XRD) characterization show that all ZnO have wurzite hexagonal crystal structure and concentration of HMTA didn’t affect crystal structure of ZnO significantly. Scanning Electron Microscope (SEM) characterization show concentration of HMTA highly affect the morphology shape of ZnO. 1:1 of Zn(NO)3 : HMTA yield nanoporous sphere structure whereas 1:2 of Zn(NO)3 : HMTA yield nanosheet structure. Sensor properties toward 30 ppm CO were investigated to know the effect of morphology structure on their sensing properties. From the CO gas sensor testing, nanoporous sphere structure has higher response toward 30 ppm CO than nanosheet structure. High porosity of ZnO nanoporous sphere make it has high response toward CO gas.

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A1-Oral-02 Photochemically Activated Indium-Gallium-Zinc Oxide for Flexible and Room-Temperature Operable Gas Sensors Rawat Jaisuttia and Yong-Hoon Kimb a

Department of Physics, Faculty of Science and Technology, Thammasat University, Pathumthani, Thailand. b School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Korea. c SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon, Korea. Email: [email protected]

Flexible and room temperature operable gas sensor have been examined using ultraviolet (UV) activated amorphous indium-gallium-zinc oxide films. The IGZO gas sensor was fabricated on polyacrylate flexible substrate by using solution-based photochemical process. Gas sensor measurements were carried out at room temperature under various UV light intensities range of 1-30 mW/cm2. The sensing response to ethanol was found to be increased as the UV intensity increases. At optimized UV light intensity, the flexible IGZO sensor showed enhanced ethanol sensing performance with excellent mechanical flexibility, even at a bending curvature angle of 70° and after 1000 cycles of the bending/relaxing process.

Sensing response

10 8 6 4 2 0

0

5

10 15 20 25 30 2

Power Intensity (mW/cm )

Figure 1. Sensing response as a function of UV intensity during exposed to 100 ppm of ethanol.

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A1-Oral-03 High-performance NO2 sensor based on MoS2-modified reduced graphene oxide Sen Liu, Ziying Wang, Tianyi Han, Teng Fei, and Tong Zhang* State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Addr: No. 2699 Qianjin Street, Changchun, P.R. China. Email: [email protected]

Recently, the fabrication of graphene-based gas sensors has attracted considerable attention due to the excellent properties of graphene-based materials ensuring them as good sensing materials. In this work, high-performance NO2 sensors based on MoS2-modifed reduced graphene oxide (MoS2/RGO) hybrids have been successfully constructed. MoS2/RGO hybrids were prepared by hydrothermal treatment of MoS2 nanoparticles modified GO obtained by self-assembly of MoS2 nanoparticles and GO, where MoS2 nanoparticles were synthesized by the sonication exfoliation method from bulky MoS2. Most importantly, MoS2/RGO hybrids exhibit good sensing performances for NO2 sensing operating at 160 ºC, including high response, fast response and recovery rate, as well as good selectivity. Furthermore, the NO2 sensor based on MoS2/RGO hybrids exhibits no obvious response or resistance change by putting the sensor into various humidity ranging from 11%RH to 95%RH. Our present work is of importance because it provides a new strategy for fabrication of high-performance NO2 sensors.

Figure 1. The response and recovery curve of the sensor based on MoS2/RGO hybrids toward various NO2 ranging fron 200 ppb to 2 ppm operating at 160 ºC.

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A2-Oral-01 Solid Electrolyte Impedancemetric NOx Sensor Using Zeolite Receptor Youichi Shimizu*, Hikaru Nakano, and Satoko Takase Department of Applied Chemistry, Kyushu Institute of Technology, City of Kitakyushu, 884-8550, Japan; Email: [email protected]

Development of compact NOx sensors become important for protection of global environments. We are developing sensors with solid-electrolyte impedance transducer [1-4]. In this study, NOx sensor was tried to be investigated using a zeolite as a receptor and a lithium ionic conductor (Li1.5Al0.5Ti1.5(PO4)3: LATP) as a transducer, respectively. The sensor device was consisted of an LATP disc, a receptor layer, and Au electrodes as shown in Fig. 1(A). A receptor paste prepared with zeolite was painted on surface of LATP, and dried, sintered at 500°C. Frequency properties of this sensor were analyzed between 50 Hz to 5 MHz, and the responses were measured at various concentrations of each NOx gas with an impedance analyzer at 300-500°C. It found that the impedance properties of the sensor devices changed with depending on NOx concentration, as shown in Fig. 1(B). Cation-exchange in zeolites gave a change in micro pore distribution, gas adsorption-desorption properties, and sensor responses. Among the ion-exchanged zeolites, the K+-exchanged Y-type zeolite showed the highest sensitivity and selectivity to NO2. The sensor responses were better than other sensors attached with ferrierite- or L- type of zeolites in which micro pores were smaller than that of Y type. The results indicate that the sensor using solidelectrolyte transducer make it possible to apply insulator materials as a receptor. Zeolite (receptor) Solid-electrolyte （transducer） Au-wire Au- electrode

Z

(A)

(B)

Fig. 1 (A) A schematic diagram of a sensor device, (B) Resistance and capacitance responses of K+-doped Y- zeolite / LATP device at 400 ºC.

This work was partially supported by Grants of JSPS KAKENHI 25410240, 16K05939, Japan. References [1] Y. Shimizu, D. Koba, H. Saitoh, S. Takase, ECS Transactions, 1 (7), 131 (2006). [2] Y. Shimizu, S. Takase, D. Koba, Advanced Materials Research, 47-50, 479 (2008). [3] H.-C. Cho, S. Kuramoto, S. Takase, J.-H. Song, Y. Shimizu, Sensors and Materials, 24 (1), 31 (2012). [4] H.-C. Cho, S. Takase, J.-H. Song, Y. Shimizu, Sensors & Actuators B, 187, 94 (2013).

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A2-Oral-02 Gas Sensor Based on Fe-Doped ZnO nanorods for the detection of Volatile Organic gases (VOCs) at Room Temperature Eadi Sunil Babu1, Sengeragchaa, Bolortuya1, Azimov Farkhod1, Min Ji Hong1, Yong Sik Kim1, Hee Jun Kim1, Young Hwa Woo1, Sungjin Kim1*

1

School of Advanced Materials & Engineering, Kumoh National Institute of Technology 61, Daehak-Ro, 39177, Gumi, Korea.. Email: [email protected]

Here in, we demonstrate the fabrication of Fe doped ZnO nanorods by simple hydrothermal method. The morphologies of these nanowires have been evaluated by X-ray diffraction studies, scanning electron microscopy, transmission electron microscopy. The results shows the nanorods with diameter range of 45~50nm, with uniform Fe doping are obtained. The gas-sensing properties of the resulting materials have been carefully studied at different operating temperature and under VOCs concentration. The sensing mechanism and the influence of doping elements on the sensing characteristics were also discussed. Keywords:

Zinc Oxide, Hydrothermal, Doping, Gas sensor, Ethanol

Acknowledgment: This work was supported by the Research Funding by Kumoh National Institute of Technology. We would like to acknowledge and thank for the funding of WC 300 Project partially supported by Business for global cooperative R&D funded by Korea Small and Medium Business Administration in 2015. We would like to acknowledge and thank for the funding of Project – 10063553 partially supported by MOTIE in 2016.

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A2-Oral-03 Humidity sensors based on stable polyelectrolytes Teng Fei, Hongran Zhao, Jianxun Dai, Rongrong Qi, Tong Zhang* State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, PR China Email: [email protected]

The main challenge of impedance type polymeric humidity sensors is the durability under high humidity environments. So the good chemical and physical stability is an important requirement for the humidity sensitive materials. Cross-linking polymerization is an effective method to construct stable humidity sensitive polymers. Click chemistry, as a useful tool for construct functional materials in a short time, has been utilized to develop different stable polyelectrolytes for humidity sensitive materials. Polyelectrolytes with good stability could be obtained by UV irradiation. Humidity sensors based on the polyelectrolytes were prepared, and the sensing properties could be adjusted by the ratio and structure of the monomers (Fig. 1). Furthermore, in situ sensitive films were prepared on the interdigitated electrodes, which could guarantee the good stability of the sensitive films (the films could endure solvents after cross-linking). In addition, hybrid materials with chemically modified polyelectrolytes on silica particles were also developed. The obtained composites could enhance the durability of polyelectrolytes under high humidity environments. Humidity sensors with high sensitivity, small hysteresis, rapid response and good stability were obtained based on the stable polyelectrolytes.

Figure 1. (a) Synthesis of the crosslinked polyelectrolytes; (b) humidity hysteresis of the sensor, (c) the sensor to continuous expiratory, and (d) the long-term stability of the sensor.

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A2-Oral-04 Hydrothermal synthesis and gas sensing property of Zn2SnO4/SnO2 flowerlike composite. Xueli Yanga, Peng Suna∗, Geyu Lua∗ a

State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012, China. Email: [email protected]

Zn2SnO4/SnO2 flower-like composite was prepared via a hydrothermal process, whose crystalline and morphology were characterized by FESEM, TEM and XRD. The XRD pattern of the product is a mixed one of the standard PDFs of Zn2SnO4 (JCPDS No. 74-2184) and SnO2 (JCPDS No. 41-1445), suggesting the product with high crystallinity is a Zn2SnO4/SnO2 composite. FESEM and TEM show that the Zn2SnO4/SnO2 composite has a good dispersity and a flower-like morphology with a diameter of about 200 nm (Figure 1A). The Zn2SnO4/SnO2 composite was applied to fabricate gas sensor device, and exhibits excellent gas sensing behavior toward triethylamine (TEA). The investigated optimum operating temperature is 250 °C. Under 250 °C, the Zn2SnO4/SnO2 gas sensor shows fast response, recovery and high selectivity (Figure 1B). The detection limit of the Zn2SnO4/SnO2 gas sensor to TEA is 500 ppb. The response values of the Zn2SnO4/SnO2 gas sensor of 500 ppb, 10 ppm and 100 ppm TEA are about 1.7, 16 and 48, respectively.

Figure 1. The morphology (A), XRD patterns, and gas sensing property (B) of the Zn2SnO4/SnO2 composite

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A3-Oral-01 The Fundamental Characteristics of WO3 Based Sensors Anna Staerz , Udo Weimar , Nicolae Barsan Institute of Physical and Theoretical Chemistry, Eberhard Karls University of Tuebingen, Auf der Morgenstelle 15, 72076 Tuebingen, Germany Email: [email protected]

WO3 is a one of the most widely used metal oxides for commercial gas sensors. The complementary response of WO3 to other commonly used n-type semiconductors, SnO2 and In2O3, can be seen in polar plot A. Here sensors based on three differently prepared WO3 samples are compared; prepared by Epifani et al. via methanolysis [1], commercially available WO3 from Sigma Aldrich and surfactant tailored WO3 using the block polymer Pluronic P123 [2]. Although the samples show varying morphologies and grain sizes, all three WO3 materials show some similar tendencies. The signals to NO2 decrease with increased humidity, the response to CO is low overall, and all show remarkably high responses to breath analysis relevant concentrations of acetone. All three samples show an increase in resistance with humidity, indicating that water vapor acts as an oxidizing gas. These responses appear to be fundamental characteristics of WO3. In addition to grain size and morphology, the effect of temperature and crystal structure will be examined. The surface reactions will be examined using diffuse reflectance infrared Fourier transform spectroscopy. This research will reveal which characteristics are inherent to WO3, and which can be tuned, i.e. through synthesis or operation temperature. It provides a necessary basis for future research on WO3.

Figure 1. Polar Plot A: The signals of sensors based on commercially available WO3, SnO2 and In2O3 from Sigma Aldrich are compared. The responses of sensors based on the P123 sample (Polar Plot B), the sample from Sigma Aldrich (Polar Plot C) and the sample from Epifani et al. are shown. 1. M. Epifani, T. Andreu, J. Arbiol, R. Díaz, P. Siciliano, and J. R. Morante, Chem. Mater., vol. 21, no. 21, pp. 5215–5221, 2009. 2. S. Pokhrel, C. E. Simion, V. S. Teodorescu, N. Barsan, and U. Weimar, Adv. Funct. Mater., vol. 19, no. 11, pp. 1767–1774, 2009.

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A3-Oral-02 Poly(N-isopropylacrylamide) Nanoparticle−Based Gas Sensor Coating Prepared from Binary Aqueous Solutions Masanobu Matsuguchi, Shinnosuke Fujii, Hajime Yagi Department of Materials Science and Engineering, Graduate School of Science and Engineering, Ehime University, 3-Bunkyocho, Matsuyama, Ehime 790-8577, Japan Email: [email protected] Poly(N-isopropylacrylamide) (PNIPAM) is a thermo-responsive polymer that exhibits a well-known lower critical solution temperature (LCST). We have been studying a possible application of PNIPAM nanoparticles as a mass-sensitive gas sensor coating. In order to increase the sensitivity of the PNIPAM nanoparticle sensor, it is important to prepare densely packed nanoparticle layers on a quartz resonator without losing the particles’ reversible and reproducible sensing nature. However, one problem in the previous study was that all deposition processes of the PNIPAM nanoparticle coating had to be performed at a temperature as high as 80 °C, because the LCST of PNIPAM in water is around 32 ºC and nanoparticles are soluble in water below this temperature. As a result, the formation of densely packed PNIPAM nanoparticles was difficult, and the production of sensor devices often lacked reproducibility. It is well known that the addition of a small amount of a good solvent may promotes a decrease in LCST due to the “cononsolvency” effect. This study aims to develop a simple new approach for preparing a PNIPAM nanoparticle coating based on PNIPAM nanoparticles prepared in water-methanol mixtures. Figure 1 shows typical SEM images of the PNIPAM nanoparticle coating prepared by the present method. As shown in Fig. 1(a), nanoparticles with diameters of ~100 nm appear to be sparsely distributed on the surface. However, Fig. 1(b) and (c), which are magnified images of specific portions shown in Fig. 1(a), show that primary particles having an average diameter of 10 nm agglomerate and distribute on the resonator surface homogeneously. The response of the present nanoparticle coating toward HCl gas was examined. The present nanoparticle coating was more sensitive but less reversible than that prepared by the former method.

(a)

(c)

(b)

100 nm

10 m

100 nm

Figure 1. SEM images of PNIPAM nanoparticles on the quartz resonator surface: (a) x10 k, (b) x500 k (the portion surrounded by the red circle in (a), and (c) x 500 k (the portion surrounded by the blue circle in (a)).

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A3-Oral-03 Wearable and rapid gas sensing with microfabricated room temperature ionic liquid electrochemical sensors Hao Wan*a,b, Heyu Yina, Sina Parsnejada, Andrew J. Masona a

Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI, 48824, USA b Biosensor National Special Laboratory, Department of Biomedical Engineering, Zhejiang University, Hangzhou, Zhejiang, 310027 China Email: [email protected]

Hazardous gas exposure monitoring is of great importance due to severe threats of gas pollutants to human health. Sensors and instruments that enable wearable and rapid gas monitoring are of great demand. This paper presents a wearable electrochemical platform integrating microfabricated electrochemical gas sensors and a miniaturized instrumentation for gas monitoring. The gas sensors feature a porous polytetrafluoroethylene (PTFE) substrate for fast gas diffusion and room temperature ionic liquid as an electrolyte to achieve long life time. Three electrode system was integrated on the same substrate for miniaturization of the sensor. A transient double potential amperometry method was employed to implement rapid gas monitoring in acute exposures as well as to reduce drifts by reversing byproducts. A multi-mode miniaturized electrochemical instrumentation has been developed for signal acquisition and communication using a custom analog interface and a microcontroller. The sensor has presented good sensitivity, linearity and repeatability in oxygen measurement utilizing the transient method. With the elaborately designed gas sensors, instrumentation and transient method, this highly miniaturized platform is very promising for hazardous gas exposure monitoring in a wearable and rapid format.

Figure 1. (a) A miniaturized platinum gas sensor using a PTFE substrate; (b) The multimode electrochemical instrumentation; (c) The response of the gas sensor for oxygen measurement; (d) The calibration of the sensor for oxygen measurement with error bars (red).

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A3-Oral-04 Impedimetric Determination of Mercury(II) Based on Electrochemical DNA Biosensor Ying Gan, Jiadi Sun, Jiawei Tu, Qiyong Sun, Ping Wang* Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, Zhejiang University, Hangzhou,310027,China * Corresponding Tel/Fax:+86 571 87952832, Email: [email protected]; [email protected]

Abstract: Heavy metal contamination in aquatic environment is increasingly more serious, which has made a great negative impact on human health and environment. Thus it is of great significance for ecosystem and human health to monitor heavy metal ions on site. In this paper, a label free electrochemical DNA sensor based on thymine-Hg2+-thymine(T-Hg2+-T) coordination chemistry for the detection of mercury(II) was developed. Gold electrode was modified by T-rich DNA via self-assembly of the terminal thiol moiety at the 5' end. In the presence of mercury(II), single-stranded DNA probe will capture the mercury ions thus inducing the conformational change from vertical state to the hairpin structure. Impedance Spectroscopy (EIS) was used to characterize the self-assembled monolayer on the gold electrode and also to detect the Hg2+mediated conformational changes, which led to a decreased RCT and provide a rapid quantitative analysis of Hg2+. The detection limit of the sensor is as low as 0.2nM (S/N=3) and its linear range of Hg2+ concentration is from 0.5 nM to 500 nM. Furthermore, the purposed DNA biosensor shows a great potential to detect Hg2+ in drinking water. Keywords: Electrochemical DNA Biosensor; Impedance Spectroscopy; Hg2+ detection

Figure 1. (A) Schematic view of the DNA sensor for Hg2+ detection;(B) CV of bare electrode and DNA hairpins-based sensor;(C) EIS responses of bare electrode, DNA hairpins-based sensor and DNA modified electrode immersed in Hg2+ 97

The 12th Asian Conference on Chemical Sensors (ACCS2017)

12-15 November, 2017, Hanoi, Vietnam

A4-Oral-01 Enzymatic synthesis of cellulose succinate as raw material of uric acid biosensor membrane Anna Roosdiana, Diah Mardiana, Ellya Indahyanti 1

Department of chemistry, Faculty of Mathematics and Natural Sciences, Brawijaya University Jl. Veteran, Malang65145, East Java, Indonesia. Email: [email protected]

The aims of this study were to determine the optimum conditions of enzymatic esterification of bacterial cellulose and succinic acid using immobilized lipase and to apply the resulted cellulose succinate as biosensor membrane. The optimum condition was observed by the effects of time and mass ratio of cellulose: succinic acid towards degree of esterification. The esterification reaction carried out in a heterogeneous system using n-butanol as solvent at 50 °C. The esterification of cellulose was conducted in various reaction time (6, 12, 18, 24 and 30 hours) and various the mass ratio of cellulose: succinic acid (1: 1, 1: 2, 1: 3, 1: 4, 1: 5 and 1: 6). Product was characterized its functional group analysis by Fourier Transform Infra Red (FTIR), determining degree of substitution (DS) by saponification, swelling index by gravimetric method, and crystallinity by X-Ray Diffraction (XRD), while the cellulose succinate was mixed with uricase and applied as uric acid biosensor membrane. The results showed that condition of esterification was optimum in 24 hours of reaction with mass ratio 1:3. The FTIR showed absorption peak at 1743,1141-1176 cm-1. DS of cellulose succinate was 0.59. The swelling and crystallinity index of cellulose succinate was smaller than bacterial cellulose. The cellulose succinate was applied as uric acid biosensor membrane performed sensitivity 2.479µs/ppm and linearity 0.982.

Figure 1. The XRD of bacterial cellulose and cellulose succinate.

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12-15 November, 2017, Hanoi, Vietnam

A4-Oral-02 3D FEM simulation of the effects of humidity sensing layer (ZnO) on response of SAW sensor based on ZnO/IDTs/AlN/Si structure Hai-Ha Nguyen*1, Ngoc-Tuan Truong2, Quang-Huy Do1, Hoang-Nam Nguyen1, HangPhuong Nguyen1, Si-Hong Hoang*1 1

School of Electrical Engineering, Hanoi University of Science and Technology, No 1 - Dai Co Viet Str. Hanoi, Vietnam 2 Hung Yen University of Technology and Education *Corresponding author: [email protected]; [email protected]

Surface acoustic wave (SAW) devices are favored for chemical sensing application because of their small size, good response time, diverse sensor coatings, inexpensive cost, high sensitivity to virtually all gasses and wireless ability. In the context of chemical and gas sensor research, temperature and humidity of air flow have much influence on experimental results; therefore, deeply studying these effects becomes a very important task. There were many studies that analyzed SAW devices via finite element method (FEM), in which most of them utilized 2D model while only a few used 3D model. Particularly, a group at the University of Ulsan built a 2D model of SAW sensor to simulate ZnO humidity sensing layer. Another group at the Chinese Academy of Sciences conducted research on ZnO(11 2 0)/R-Sapphire structure through a 3D analysis, but they considered water layer induced by adsorption of water vapor as a mass layer. On the other hand, Other groups simulated humidity sensor based on polymer sensing layer. Accordingly, in this research, we analyzed the influence of humidity on SAW sensor with ZnO/IDTs/AlN/Si multilayer structure, as shown in Fig.1, by changing chemical characteristics of the ZnO humidity sensing. 3D FEM model of SAW sensor, as Fig.2, was created to account for the simulation accuracy. Figure 1. Figure 2. Meshing Schematic of the process. humidity SAW sensor coated with a ZnO sensing layer The operation of the SAW humidity sensor presented in this paper is based on the frequency shift of the frequency response which is affected by the change of mass density and electrical conductivity of sensing layer material. In similar temperature conditions, the growth of humidity would result in an increase in mass density and electrical conductivity of ZnO thin film.The simulation results showed a decrease in resonant frequency from 126.3 MHz to 121.0 MHz corresponding to the increase of the mass density of ZnO from 5675 kg/m3 to 5685 kg/m3 and a decrease in resonant frequency from 126.3 MHz to 124.6 MHz corresponding to the increase of the conductivity of ZnO from 1 S/m to 104 S/m.

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12-15 November, 2017, Hanoi, Vietnam

A4-Oral-03 The Impedimetric Bioaffinity Sensing Chip Integrated with an Electrohydrodynamic Centripetal Vortex Ming-Jie Lin, Yan-Fu Liu, Ching-Chou Wu Department of Bio-industrial Mechatronics Engineering, National Chung Hsing University, Addr: No. 145 Xingda Rd. Taichung, Taiwan. Email: [email protected]

Immunoglobulin-binding proteins that are commonly used in conventional immunoreaction typically utilize diffusion dominated transport of antibody, which is limited by slow reaction rates, numbers of bound antibody and long detection times for immunosensors. In this research, a single-disk multi-ring gold electrode chip was construct with the integration of the dc-biased alternating current electrokinetic flow (ACEKF) mixer and the electrochemical impedance spectrum (EIS) measurement. ACEKF chip integrated with electrochemical three-system gold electrodes were

made by the lift-off microfabrication process. Moreover, the Pt metal particle was electrodeposited on a gold electrode multi-ring due to prevention of antibody binding. The ACEKF could produce a vortex to improve bio-affinity interaction between biological molecular and recognition element. The result showed that the secondary antibody (IgG) reacted an affinity plateau with protein A under ACEKF control for 8 min. The numbers of bound antibody at saturation driven by ACEKF was 3.5 times larger than that kept in stationary solution. The EIS-based sensing chip had a good linearity in the range of 1 ng/mL-10 μm/mL for IgG antibody. The chip design can achieve the purpose of rapid.

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Figure 1. (a) Scheme of the chip design. (b) The EIS measured with dc-biased ACEK for 8 min after different antibody concentration binding Protein A on gold electrode surface.

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12-15 November, 2017, Hanoi, Vietnam

A5-Oral-01 Highly selective and sensitive ethanol sensor using urchin-like Mg-doped ZnO nanowire networks Chang-Hoon Kwak, Hyung-Sik Woo, and Jong-Heun Lee* Department of Materials Science and Engineering, Korea University, Seoul, 136-713, South Korea Email: [email protected]

Oxide nanowire networks with high surface area-to-volume ratios, thin diameters, high crystallinity, and less agglomerated configurations are promising gas-sensing materials with high gas response, excellent gas accessibility, and stability. In this contribution, urchin-like Mg-doped ZnO nanowire networks were prepared by MgO-seeded vapor-phase growth of ZnO nanowires, and their potential as gas-sensing materials was investigated. The slurry containing MgO powders ([Mg] = 0.05 and 0.1mol/L) was drop coated on a substrate with electrodes and dried. The Mg-doped ZnO nanowire networks were grown by placing MgO-coated alumina substrate at the center of quartz tube in the horizontal furnace with Zn metal powders and subsequent heating and kept at 500 oC for 10 min to grow Mg-doped ZnO nanowire networks. The response (resistance ratio) of the urchin-like Mg-doped ZnO nanowire networks to 5 ppm C2H5OH at 350 o C was as high as 343, which is significantly higher than that of pure ZnO nanowire networks (7.0). In addition, the Mg-doped ZnO nanowire network sensors showed high response to 5 ppm C2H5OH with negligibly low cross responses to other representative and indoor air pollutants such as H2, NH3, benzene, toluene, p-xylene, and HCHO. The sensor exhibited and an unprecedentedly high response (28.8) even to 0.25 ppm C2H5OH. The improvement of the gas response and selectivity to C2H5OH was attributed to Mg-doping-induced decrease of the charge carrier concentration, the change of nanowire thickness/morphology, increase of the bandgap and the catalytic promotion of the C2H5OH sensing reaction.

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A5-Oral-02 Short-term drift compensation techniques based on chemical sensors array Jin-Young Jeon, Jang-Sik Choi, Joon-Boo Yu, Hyung-Gi Byun Division of Electronics, Information & Communication Engineering, Kangwon National University, 346, Jungang-ro, Samcheok-si, Gangwon-do, Korea Email: [email protected]

The ideal chemical sensors must show the similar results under the same conditions regardless of the time passing. However, the chemical sensors responses are shown lack of reproducibility following by measurement periods. It is called as drift effect. It may be occurred over several days or weeks and can be caused by a various problems, including hardware defects in the gas measurement system or various environmental factors (temperature, humidity, etc.). If the problem is not properly taken into consideration, the stability and reliability of the system using chemical sensors would be decreased. In this paper, we present drift compensation techniques to improve reproducibility for chemical sensors array in short term period. We continuously measured ethanol of 1ppm 73 times for 4 days using an array containing 4 sensors, and drift compensation techniques were performed using measured data in that periods. For the short-term drift compensation, three techniques (Discrete Wavelet Transform (DWT), Baseline Manipulation, and Internal Normalization) were applied, and the results were compared by using the trend line graph and CV(Coefficient of Variation). As a result of comparison, the mean CV of DWT was showed the lowest value. (Before compensation: 6 %, DWT: 1.432 %, Baseline Manipulation: 3.491 %, Internal Normalization: 3.734 %).

Figure 1. Trend line graph of compensation results Acknowledgements: This work was supported by Institute for Information & communications Technology Promotion (IITP) grant funded by the Korea government (MSIP) (No.2015-0-00318, Olfactory Bio Data based Emotion Enhancement Interactive Content Technology Development)

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12-15 November, 2017, Hanoi, Vietnam

A5-Oral-03 Highly selective and sensitive benzene gas sensor using Pd-SnO2 yolk-shell micro-reactors with a catalytic Co3O4 overlayer Seong-Yong Jeonga, Ji-Wook Yoona, Tae-Hyung Kima, Hyun-Mook Jeonga, Chul-Soon Leea, Yun Chan Kanga and Jong-Heun Leea, * a

Department of Materials Science and Engineering, Korea University, Seoul 02841, South Korea Email: [email protected]

Benzene is a highly toxic and ubiquitous volatile organic compound, which is known to induce serious disease such as leukemia and aplastic anemia. Accordingly, carcinogenic benzene should be measured precisely for monitoring of air quality and to protect human being. Unfortunately, the BTX (Benzene, Toluene, and Xylene) gases with aromatic ring are chemically stable and thus less reactive to oxide semiconductor gas sensors. Moreover, similar chemical structures of BTX gases hamper the discrimination among them. In the present contribution, we report a new strategy to detect the sub-ppm-level benzene in a highly selective manner using oxide semiconductor chemiresistors. The gas sensors based on the Pd-loaded SnO2 micro-reactor sensing layer and thin catalytic Co3O4 overlayer exhibited ultrahigh response (resistance ratio = 89) to 5 ppm benzene with negligibly low cross responses to other representative and indoor air pollutants such as toluene, p-xylene, HCHO, CO, and ethanol. These unprecedentedly high selectivity and gas response about benzene vapor, which can be hardly achieved by simple loading of noble metal catalysts on oxide nanostructures, were attributed to the synergetic combination between catalytic Co3O4 layer and Pd-SnO2 yolk-shell micro-reactor. The low responses toward toluene, p-xylene, HCHO, CO, and ethanol was explained by the complete oxidation of reactive analyte gases into less- or non-reactive oxidized species (CO2 or H2O) prior to the gas-sensing reaction. This selective and sensitive benzene sensor can be used for monitoring indoor and outdoor air quality.

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12-15 November, 2017, Hanoi, Vietnam

A6-Oral-01 Two-dimensional NbS2 gas sensor for room temperature NO2 detection Yeon Hoo Kima, Ki Chang Kwona, Seo Yun Parka, Tae Hoon Kima, Junmin Suha, and Ho Won Janga* a

Department of Materials Science and Engineering, Research Institute of Advanced Materials Seoul National University, Seoul, 08826, Republic of Korea Email: [email protected]

Chemoresistive sensors based on semiconducting metal oxides have attracted enormous attention due to its diverse applications, such as environmental monitoring, tranportation industries, and deascease dianosis. However, gas sensors based on metal oxides require external heaters for high operating temperatures leading to thermal safety problems, complex device structures, and high power consumption. For these reasons, two-dimensional (2D) transition metal disulfides (TMDs) have been attracting rapidly increasing interest for gas sensing applications because of its moderate band gap energy, high specific surface area, and high sensitivity at room temperature. Among the various TMDs, however, gas sensing properties and the mechanisms of 2D NbS2 has never been reported yet. Herein we present gas sensing properties of 2D NbS2 synthesized by chemical vapor deposition method. The NbS2 sensors showed high sensitivity, selectivity and reversibility NO2 sensing behaviors at room temperature. The sensing mechanisms are investigated by density functional theory calculations. We believe that these high performance of 2D NbS2 sensors will broaden the potential use of not only NbS2, but also other 2D TMDs in various sensing applications.

Figure 1. (a) Dynamic sensing transient of NbS2 to three consecutive pulses of 5 ppm NO2. (b) Response NbS2 gas sensors to various gases.

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12-15 November, 2017, Hanoi, Vietnam

A6-Oral-02 Iron oxide - carbon nanotube composite structure for room temperature ammonia gas sensor Nguyen Minh Hieu, Truong Thi Hien, Nguyen Duc Chinh, Nguyen Duc Quang, Cao Van Phuoc, Chungjoong Kim, and Dojin Kim* Department of Materials Science and Engineering, Chungnam National University (CNU), 99 Daehang-ro, Yuseong-gu, Daejeon 34134, Republic of Korea Email: [email protected]

Fe2O3:CNT nanoporous structures were fabricated and characterized for ammonia detection at room temperature. The porous structures were synthesized by the arc-discharge method followed by oxidation. The sensor showed a good response, repeatability, and stability at room temperature for measurement at a concentration of 500 ppm NH3. Specially, our sensor showed the highest response behavior at room temperature, and we claim the optimum temperature of room temperature. The result is a unique phenomenon when compare to the other popular oxide gas sensors. However, the response and recovery kinetics remained slow, and need to be improved. Sensing mechanisms and detail sensing properties will be discussed.

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12-15 November, 2017, Hanoi, Vietnam

A6-Oral-03 Knittable and wearable gas sensors using reduced graphene oxide covered carbon fabrics decorated with metal catalysts for enhanced selectivity Chung won Lee, Jun Min Suh, and Ho Won Jang† Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Republic of Korea

Email: [email protected]

In recent days, gas sensors have been attracting great interests for various purposes such as monitoring indoor air quality, detecting harmful gases, or providing information on food storage. Among them, researches on gas sensors to detect the gaseous substances from human body have been extensively conducted. The composition of gaseous substances from human activity like breathing contains information about health status such as diabetes, respiratory diseases, or even cancers. Even if there exist various gas sensor technologies to detect those substances from human breath, however, they cannot continuously monitor every single breath due to their rigid platform restricting them from being attached close to human breath. Therefore, gas sensors with a simple and flexible structure with capability of positioning near human breath are required. Here, we report knittable and wearable gas sensors based on reduced graphene oxide (rGO) covered carbon fabrics (CFs) decorated with metal catalysts for enhanced selectivity. The rGO junctions between rGO covered CFs synthesized by annealing graphene oxide (GO) electrodeposited CFs, function as an active material for gas sensing, and metal catalysts (Cu, Pt, and Pd) were decorated to enhance selectivity between various gases (H2S, H2, volatile organic compounds). Since CFs are flexible and soft, gas sensors based on them are knittable and ultimately capable of direct application into clothes, the optimal location for monitoring human breath.

Figure 1. (a) Photograph and (b) response curve to 10 ppm NO2 of a carbon fabric junction

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12-15 November, 2017, Hanoi, Vietnam

A6-Oral-04 Tailoring Chemically Converted Graphenes Using a Water-soluble Pyrene Derivative with a Zwitterionic Arm for Sensitive Electrochemiluminescencebased Analyses Jihye Kwon, Seo Kyoung Park, Yongwoon Lee, Je Seung Lee, and Joohoon Kim* Department of Chemistry, Kyung Hee University, Seoul 130-701, Republic of Korea Email: [email protected]

Here, we report a method to tailor chemically converted graphenes (CCGs) using water-soluble pyrene derivative 1 with a zwitterionic arm, which facilitates the integration and functionalization of the CCGs on indium tin oxide (ITO) electrodes for highly sensitive electrochemiluminescence (ECL)-based analyses.[1] The compound 1 consisted of a pyrene appended with a 3-(imidazolium)propionate zwitterionic arm, which serves the dual purpose of improving the dispersion of the CCGs in aqueous solutions and further tailoring the catalytic activity of the CCGs with dendrimer-encapsulated catalytic nanoparticles. Specifically, we synthesized the pyrene derivative 1, and prepared aqueous dispersion of 1-functionalized CCGs via non-covalent anchoring of the aromatic pyrene moiety of 1 onto the hydrophobic basal planes of the CCGs. The stability of the aqueous dispersion of the 1-functionalized CCGs was greatly improved due to the hydrophilic zwitterionic arm in 1 anchored onto the CCGs, which thus facilitates the processability for integration of the CCGs onto ITO substrates. In addition, the carboxylic group of the zwitterionic arm in 1 allowed the facile secondary functionalization of the CCGs on the ITOs via the covalent conjugation of amine-terminated dendrimers encapsulating catalytic nanoparticles for highly enhanced ECL emission. As a model system, we conjugated well-defined dendrimer-encapsulated Pt nanoparticles (diameter 1.8  0.2 nm) to the 1-functionalized CCGs on ITOs. The resulting ITOs exhibited significantly increased ECL emission of the luminol/H2O2 ECL system; i.e. two orders-of-magnitude enhancement in the ECL compared to that obtained from bare ITOs, which allowed a ~154 times more sensitive ECL-based analysis of cholesterol using the modified ITOs compared with the use of bare ITOs. Reference [1] Biosensors and Bioelectronics, 87 (2017) 89-95.

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A6-Oral-05 Highly sensitive H2S gas sensors based on Pd-doped CuO nanoflowers with low operating temperature Xiaobing Hu, Zhigang Zhu *, Yihua Wu, Lijun Cai School of Environmental and Materials Engineering, College of Engineering, Shanghai Polytechnic University, Shanghai, 201209

Abstract: A facile method was used to prepare Pd-doped CuO nanoflowers with various doping concentrations. The samples were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), inductively coupled plasma atomic emission spectrometer (ICP-AES), and Brunauer - Emmett - Teller (BET) specific surface area analysis. The responses (Rg/Ra or Ra/Rg, where Rg is the resistance in gas, and Ra is the resistance in air) of such sensors exposed to 50 ppm CH4, NO2, C2H5OH, H2S, NH3, and H2 were measured for comparison. For 1.25 wt% Pd-doped CuO nanoflowers, the response (Rg/Ra) to 50 ppm H2S was 123.4 at 80 oC, which was significantly higher than that of pure CuO (Rg/Ra=15.7). Furthermore, excellent stability and repeatability of the gas sensor were also demonstrated. The observed results clearly revealed that it is an important and facile approach to detect the H2S at low operating temperature for practical applications. Keywords: CuO; gas sensor; Pd doping; p-type; low temperature

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B1-Oral-01

Utilization of a Solid Electrolyte CO2 Sensor for the Performance Evaluation of CO2 Capture Materials Ayaka Yamamoto1, Armand Quitain1, Mitsuru Sasaki1,2, and Tetsuya Kida1* 1

Department of Applied Chemistry and Biochemistry, Kumamoto University 2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, Japan 2 Institute of Pulsed Power Science, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto 860-8555, Japan * Corresponding author: Fax: 81-096-342-3665, E-mail: [email protected]

Continuous monitoring of CO2 concentration is important to various fields to monitor global warming, volcanic activity, indoor environment, and human health. Generally, non-dispersive infrared analyzer (NDIR) is used for CO2 concentration measurements. NDIR has high accuracy, and excellent reliability. However, this sensor is large, complex and expensive. Therefore, more compact and inexpensive sensors are demanded. Here, we focus on a solid electrolyte CO2 sensor because it is compact, inexpensive and applicable for continuous measurements. The solid electrolyte CO2 sensor is made of sodium super ionic conductor (NASICON), binary carbonate, composite of BiCuVOx and perovskite oxide as the solid electrolyte, CO2 sensing layer, and solid-reference electrode, respectively. The CO2 concentration is detected as an electromotive force (EMF) of the sensor according to the Nernst equation. In this study, to demonstrate the applicability of the sensor for various applications, the developed sensor was used for the performance evaluation of CO 2 capture materials. We show that it is possible to monitor a change in CO2 concentration during adsorption and desorption processes using the CO2 sensor.

Figure 1. (a)Response transient of the sensor to change in CO2 concentration. (b) Change in EMF during adsorption and desorption processes.

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12-15 November, 2017, Hanoi, Vietnam

B1-Oral-02 Solid electrolyte gas sensor using proton conductive graphene oxide Yuta Kuwakia, Azumi Miyamotoa, Armando T. Quitaina, Mitsuru Sasakib, Tetsuya Kidaa a

Department of Applied Chemistry and Biochemistry, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, Japan b Institute of Pulsed Power Science, Kumamoto University 2-39-1 Kurokami, Chuo-ku, Kumamoto, Japan Email: [email protected]

Hydrogen has been attracting much attention as a clean energy that emits only water after combustion. However, compared with other fuels (e.g. LNG, Propane and Gasoline), hydrogen has a wide explosion range and small minimum ignition energy. Thus, a highly sensitive sensor capable of detecting leakage of hydrogen is necessary for safety use of hydrogen. Solid electrolyte sensor using proton conductors such as Nafion is the one of the most successful sensors to detect hydrogen in ppm concentrations. In this study, we focus on a proton conducting graphene oxide membrane as a new solid electrolyte sensor material. Graphene oxide (GO), synthesized from abundant graphite by oxidation and exfoliation processes, shows high proton conductivity (About 2×10-2 S/cm) at room temperature due to the presence of a variety of oxygen functional groups such as hydroxyl and epoxy groups on the surface. GO membranes were fabricated by filtration using a colloidal solution containing GO nanosheets synthesized by a modified Hummers’ method. In this study, we studied the hydrogen sensing properties of GO membrane-based sensors with concentration cell- and planar-type structures at room temperature. The GO sensor with Pt/C electrodes showed good electromotive force (EMF) responses to hydrogen in ppm concentrations in air. The sensing mechanism can be explained in terms of the mixed potential theory.

Fig.2 Hydrogen response of a planar-type sensor at room temperature.

Fig.1 Structure of the GO membranebased sensor device.

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12-15 November, 2017, Hanoi, Vietnam

B1-Oral-03 Fabrication of well-ordered porous array mounted with gold nanoparticles and enhanced sensitivities for mixed potential-type zirconia-based NH3 sensor Bin Wanga, XishuangLianga, GeyuLua a

State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012, China Email:[email protected]

The nano-bowl shaped structure and gold nanoparticle array were successfully fabricated on the YSZ substrate and examined to improve the sensitivity of mixed potential type NH3 gas sensor. The nano-bowl shaped structure was constructed by solution-dipping template (polystyrene spheres) strategy and gold nanoparticle inlaid in the nanostructure was fabricated by vacuum evaporation plating technology. The present study mainly explored the influence of gold layer’s thickness on the nanostructure. The perfect ordered gold nanoparticle array inlaid in nano-bowl shaped structure was obtained when the evaporated gold film thickness was about 50 nm. The mixed potential type gas sensor which based on processed YSZ substrate displayed a high sensitivity of -59.6 mV/decade to NH3 in the range of 10–400 ppm and larger response (63mV)to 100 ppm NH3 at elevated temperature. All the enhanced sensing properties might due to the enlarged three phase boundary (TPB) and inlaid gold nanoparticle array.

Figure 1. (a) AFM image of nano-bowl shaped structure mounted gold nanoparticle; (b) Schematic diagram of the YSZ-based NH3 sensors; (c) Dependence of ΔVon thelogarithmof NH3 concentrations for the sensors; (d) Sensitivities of different sensors to 100 ppm various gases.

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12-15 November, 2017, Hanoi, Vietnam

B2-Oral-01 The Design of Module e-Nose Combining with Pattern Recognition for Lung Cancer Screening Xusheng Zhang, Fan Gao, Xi Zhang, Jiajing Sheng, Ping Wang* Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, Zhejiang University, Hangzhou,310027,China * Corresponding Tel/Fax:+86 571 87952832, Email: [email protected] (Ping Wang)

This paper presents a new module e-Nose combining with pattern recognition for lung cancer screening. The e-Nose uses new module design. A sensor array consisting of 10 MOS sensors is placed in the gas chamber to detect the exhaled breath. The exhaled breath is collected by the gas sampling bag, then adsorbed by the adsorption tube. The adsorbed VOCs is desorbed at high temperature and then swept into the gas chamber. The response data of the sensor array is collected by PC software and analyzed by recognition algorithm. For each sensor response data, we can extract 10 characteristic values, such as response peak value, steady-state value, response time, response peak area, etc. Then, the dimension of the characteristic values is reduced by the principle components analysis (PCA) method. Finally, the back propagation (BP) neutral network algorithm is used to recognize lung cancer. The experimental results show a relatively high recognition rate of lung cancer. The ANN performs a high sensitivity and specificity (91.49% and 85.71% respectively). Keywords: e-Nose devices and application; Pattern recognition; Lung cancer screening

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Figure 1. e-Nose system for lung cancer screening. (a) Collect the patient's exhaled breath into the sample bag. (b) Inside of the module e-Nose. (c) The typical response curves of the sensors array. (d) Pattern recognition software based on PCA and ANN algorithms.

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B2-Oral-02 Surface Functionalization of Gold Surfaces with Polypeptide: A Low-Fouling Zwitterionic Surface for Detecting Placenta Growth Factor W.E. Hsua, C.H. Yangb, C.C. Changa, S.C Weic, C.W. Lina a

Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan c Department of Internal Medicine, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan. Email: [email protected] b

In Taiwan, the incidence rate of colorectal cancer has become first for seven consecutive years. Placental growth factor (PlGF) is a biomarker of colorectal cancer which can be used as one of the risk factors for prognosis recurrence. In this study, we use surface plasmon resonance (SPR) for detection of PlGF in patient's serum. SPR has many advantages, including high sensitivity, real-time detection, and non-fluorescent labeling. However, non-specific adsorption results in error signals. We used mixed amino acid sequences for protein anti-fouling and antibody modification. This method can detect the presence of PlGF in serum, and the limit of detection(LOD) is 2pg/ml. We also used clinical samples to compare ELISA and SPR, our method showed 60% accuracy.

Figure: (a) Fabrication of Au film with antifouling properties: anti-fouling peptide (AFP): EKEKEKEPPPP-C and probe peptide (PP): RRGW-EKEKEKE-PPPP-C. (b) SPR detection of PlGF in 1xPBS solution, ranging from 2 pg/ml to 100 pg/ml. (c) Calibration curve of PlGF in 1xPBS solution.

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B2-Oral-03 Detection of triethylamine with fast response by Al2O3/α-Fe2O3 composite nanofibers Lanlan Guo, Yanfeng Sun*, Geyu Lu* State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012, People’s Republic of China. Email:[email protected] Pure α-Fe2O3 nanotubes and a series of Al2O3/α-Fe2O3 (the mass ratios of Al source and Fe source were 12.5wt%, 25.0wt% and 37.5wt%) composite nanofibers have been successfully synthesized via a facile electrospinning method and subsequent calcination at 500 °C for 2 h. The characterizations of these samples were obtained by various techniques. It was found that the composite samples were composed of amorphous Al2O3 and crystal α-Fe2O3. The composite Al2O3/α-Fe2O3 nanofibers have smaller grain size than that of pure α-Fe2O3 nanotubes prepared by the same process. Comparative gas sensing studies between Al2O3/α-Fe2O3 composite nanofibers and pure α-Fe2O3 nanotubes were performed to show the superior sensing properties of the composite samples. As expected, the sensor using Al2O3/α-Fe2O3 (25 wt% Al) exhibited the highest response to 100 ppm triethylamine (TEA) at 250 °C (Fig. 1a). The response and recovery times of the sensor were about 1 and 17s, respectively, which were superior to pure αFe2O3 nanotubes (Fig. 1b). The enhancement of the gas sensitivity would be attributed to the addition of Al. Al2O3 could lead to large surface area and adjust the carrier concentration, inducing the change of the oxygen deficiency and chemisorbed oxygen of α-Fe2O3 nanofibers.

Figure 1. (a) Responses of the as-fabricated four gas sensors to 100 ppm TEA at different operating temperatures, the inset is the SEM image of Al2O3/α-Fe2O3 (25 wt% Al). (b) The dynamic response–recovery curves of pure α-Fe2O3 and Al2O3/α-Fe2O3 (25 wt% Al) at 250°C. 114

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B2-Oral-04 Organophosphate Pesticides Determination by 3D PADs and ePADs Hua Quoc Trunga, Daniel Citterio a

Analytical Chemistry Laboratory, Department of Applied Chemistry, Faculty of Science and Technology, Keio University, Address: 3-14-1 Hiyoshi, Kohoku-ku, 223-8522, Yokohama, Japan. Email: [email protected]

In this research, organophosphate pesticides were analyzed by either 3D microfluidic paper-based analytical devices (3D PADs) or electrochemical paper-based analytical devices (ePADs). The simple 3D PADs was designed optimally to minimize all unnecessary steps so that only sample and buffer solution were added. The significantly important key-point of this device is based on the enzymatic reactivity enhancement by flow control using sucrose in 3D devices. Pesticides inhibited AChE enzyme that was immobilized on skim milk surfaces. The remaining AChE was eluted continuously to indoxyl acetate containing surface through a pH control disc by adding 600 L of Tris-buffer 25 mM and further afforded enzymatic reaction which resulted in blue color at sensing areas. The blue indigo color was additionally stabilized by PDDA due to electrostatic attraction between DO- produced by enzyme hydrolysis and positively charged polymer. After incubation, the obtained blue color was measured and characterized by scanner and imageJ respectively. Moreover, ePADs was also developed to analyze organophosphate pesticides due to highly selective binding of zirconium to organophosphates. This ePADs consists of three electrode systems printed on paper surfaces by dimatix printer including Ag/AgCl, ZrO2/AuNPs, and polyaniline conducting polymers (PANi). Interestingly, PANi could be used as a counter electrode in our research for the first time, which is a great alternative to costly commercially available platinum electrode. B. A

A.

I S

Figure 1. A. Design of 3D PADs by assembling multi-layers of paper containing different reagents in according to following orders: 1. Acetylcholinesterase (A); 2. pH control disc; 3. Indoxyl acetate (I); 4. Paper disc; 5. Sucrose for flow control (S); 6. Absorbent pad. B. 3 electrode systems (Commercial Ag/AgCl; AuNPs; PANi) for ZrOCl2 deposition on working electrode by cyclic voltammertry. 115

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B3-Oral-01 Breath Control in Respiratory Air and Simultaneous Analysis of Sensor Data Rolf Seiferta, Thorsten Conrad, Jens Peter, Hubert Keller a

Karlsruhe Institute of Technology (KIT), Hermann-von-Helmhotz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany Email: [email protected]

There is a broad field of applications of breath monitoring in human health care, medical applications and alcohol control. In this report, an innovative mobile sensor system for breath control in the respiratory air called AGaMon will be introduced which is able to recognize a multitude of different gases like ethanol (which is the leading component for alcohol), H2S (which is the leading component for halitosis), H2 (which is the leading component for dyspepsia and food intolerance), NO (which is the leading component for asthma) or Acetone (which is the leading component for diabetes), thus covering almost all significant aspects. An innovative calibration and evaluation procedure called SimPlus was developed which is able to evaluate the sensor data simultaneously. That means, SimPlus is able to identify the gas samples simultaneously, for example whether the measured gas sample is ethanol or another gas under consideration. Furthermore, SimPlus is able to determine the concentration of the identified gas sample. This will be demonstrated in this report for the application of ethanol, H2, acetone and the binary mixture ethanol-H2. It could be shown that SimPlus could identify the investigated gases very well and also that the relative analysis errors were smaller than 10% in all considered applications.

Figure 1. Pre-release Version of the Mobile Sensor System.

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B3-Oral-02 Development of a rapid and sensitive biosensor for biological toxins Hui-Pin Cheng 1, Han-Sheng Chuang 1,2 * 1

Department of Biomedical Engineering, National Cheng-Kung University, Tainan, Taiwan 2 Medical device innovation center, National Cheng-Kung University, Tainan, Taiwan *Email: [email protected] Abstract Bacterial toxins in food and environmental samples have long been a threat to public health1. Prescreening of biosensors ensures food safety in manufacturing and storage processes. Bacterial toxins such as aflatoxin, botulinum toxin, or ocher aflatoxin is environmentally stable and will not decompose naturally. Among them, botulinum toxin is the deadliest one and its lethal dose in unvaccinated humans is estimated to be 1 ng/kg. However, the conventional detection methods are impractical because testing needs to be conducted on a series of benchtop instrtuments, resulting in tedious processes. Most of the instruments are also limited by low sensitivity and low selectivity. As a result, developing a rapid and sensitive method for bio-toxins remains urgently required. To tackle the problems, we herein proposed a diffusometry enabled bead-based immunosensing technique to achieve rapid, simple, and quantitative detection of biological toxins. The technique was based on Brownian motion of functionalized particles combining with immunoassays2. By capturing the toxic proteins with the particles, Brownian motion of the particles will decline due to the increased particle diameter3. Therefore, the concentration of the toxic proteins can be associated with Brownian motion. In this study, we conducted three calibration curves for purified botulinum toxin in phosphate buffer, whole milk, and bovine serum in the range of 0.01–500 ng/ml. In addition, we designed a dichotomy method based on a competitive immunoassay comparison between the diffusivities of an unknown sample and a sample with base concentration of toxin in this study. The diffusivity will increase when the concentration of unknown toxin is higher than the base and vice versa. Therefore, a competitive immunoassay was used in dichotomy screening to achieve rapid detection. This technique featured rapid detection (< 20 min), high precision, and low limit of detection (~10 pg/mL). Overall, the success of this technique will eventually provide a powerful tool for the food safety in the food and medical instrument industries. References 1. Cheung MY et al. J Microbiol. 2013; 51 (1): 1-10. 2. H.S. Chuang, A. Kumar and S.T. Wereley, in Methods in Biology: Biomicrofabrication and Biomicrofluidics. 2010; 281-310. 3. Kumar A et al. Journal of Fluids Engineering. 2008; 130: 111401.

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B3-Oral-03 Plasmonic Resonance Modes and SERS Performance of Out-of-plane Silver V-shape Substrates Jianghao Li*, Yihang Fan, Xiaotian Xue and Zhengjun Zhang School of Materials Science and Engineering, Tsinghua University, Beijing, China Email: [email protected] Kinks of the out-of-plane V-shape nanostructures may form more hot spots for Surface-enhanced Raman scattering (SERS). Here we analyze the localized surface plasmonic resonance (LSPR) of silver V shapes by studying the gradual development process of LSPR from sphere to out-ofplane V shape using numerical calculations. This approach allowed us to relate LSPR of out-ofplane V shapes to the well-studied spheres and gain in-depth knowledge concerning the origin of LSPR modes in a V shape. Major LSPR modes in V shapes gradually evolve from dipole and quadrupole modes in silver nanospheres and resemble their charge distribution patterns. Relations between LSPR wavelength and l/d ratio are predicted theoretically and verified experimentally. Through fitting, we found resonance wavelengths of all three modes appear quadratic relations as a function of length/diameter ratio (l/d ratio) ranging from sphere to V shapes. We further verified this quadratic relation experimentally by measuring the reflectivity of samples prepared by GLAD. V-shape samples with various l/d ratios were measured and clear dips of reflectivity within the range of 600nm to 900nm contributed by “quadrupole” mode were identified. Trend of Raman signal results were consistent with numerical simulated Raman signal enhancement factor. This work introduces novel approach to understand out-of-plane irregular nanostructures’ LSPR modes and can guide researchers in the design and optimization of out-ofplane V-shape SERS substrates.

Figure 1. (a) Charge density distribution evolution of “dipole” plasmon mode. (b) SEM, (c) TEM and (d) simulation model of silver V-shape nanorods prepared by GLAD.

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B3-Oral-04 Enzymatic Flexible Arrayed Urea Biosensor Based on GO/TiO2 Films Modified by Magnetic Beads Cian-Yi Wua, Jung-Chuan Choua, b, *,Yi-Hung Liaoc, Chih-Hsien Laia,b, Siao-Jie Yana, You-Xiang Wua, and Hong-Yu Huangb a

Graduate School of Electronic Engineering, National Yunlin University of Science and Technology, No. 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan, R.O.C. b Department of Electronic Engineering, National Yunlin University of Science and Technology, No. 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan, R.O.C. c Department of Information and Electronic Commerce Management, TransWorld University, No. 1221, Zhennan Rd., Douliu City, Yunlin County 640, Taiwan, R.O.C. E-mail: [email protected] (MOST 105-2221-E-224-049) We proposed an enzymatic flexible arrayed urea biosensor based on graphene oxide (GO)/titanium dioxide (TiO2) films modified by magnetic beads (MBs). The urea biosensor was comprised of polyethylene terephthalate (PET), arrayed conductive wires and reference electrode, insulation layer and sensing films. The PET, used as substrate, has the advantages of portability, costeffectiveness, flexibility and easy to preserve. Arrayed conductive wires and reference electrode were prepared by screen-printing with silver paste. Epoxy was used as insulation layer in encapsulated process, and which could define the sensing area by screen-printing. TiO2 was acted as sensing film, which is environmentally friendly and has better electron transition, and it was deposited by sputtering. The GO has a large specific surface area and rich functional groups, which is employed as an ideal matrix for enzyme immobilization and can improve enzyme absorption. The MBs were utilized to flexible arrayed urea biosensor based on GO/TiO2 film because MBs could enhance the enzyme-immobilization ability and have superior biocompatibility. The performances of flexible arrayed urea biosensor based on GO/TiO2 film, modified by MBs were measured via potentiometric measurement system. The electrochemical impedance spectroscopy (EIS) was utilized to investigate the electrochemical impedances of urease/GO/TiO2 and ureaseMBs/GO/TiO2 films. It could be found, that MBs could effectively enhance the catalytic reaction. Therefore, we provided a high sensitive platform for urea detection.

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C1-Oral-01 Determination of Nitrate Ions in Potable Water Using a Miniaturized Electrochemical Sensor Yang Li a, Yu Song a, b, Jianhua Tong a, Chao Bian a, Jizhou Sun a and Shanhong Xia a a

State Key Laboratory of Transducer Technology, Institute of Electronics, Chinese Academy of Sciences, Addr: No.19 Bei-Si-Huan West Rd., Haidian, Beijing, China. b University of Chinese Academy of Sciences, Addr: No.19 Yuquan Rd., Beijing, China. Email: [email protected]

This paper describes the fabrication, characterization and application of a miniaturized electrochemical sensor for nitrate detection in potable water. The miniaturized sensor employed in the electrochemical measurements was fabricated by micromachining technology based on standard photolithography and liftoff process. As the sensitive material, copper nanoparticles was successfully prepared on the surface of the working-electrode using controlled-potential reduction in acidic copper sulphate electrolyte directly. The electrocatalytic reduction of nitrate ions on copper surface under acidic condition (pH = 2.0) was measured by linear sweep voltammetry (LSV) scan to implement the ion recognition and quantification process. The experimental results reveal that the sensor performed high sensitivity of 0.0332 µA/µmolL−1 for nitrate detection with the concentration range from 6.25 µmolL−1 to 1000 µmolL−1. Concentrations of five standard nitrate samples and two real water samples were measured. The results given by the sensors were in good agreement with the data obtained by standard ultraviolet (UV) spectrophotometric method for nitrate measurement. The maximum deviation between this two methods is of 16.2%. (a) Glass Wafer Cleaning

(b) Photolithography

(c) Cr/Pt Layer Sputtering

(d) Lift Off

(e) The 1st SU-8 Patterning

(f) The 2nd SU-8 Patterning

Glass

AZ1500

(A)

Platinum

SU-8

(B)

(C)

Figure 1. The miniaturized nitrate sensor: (A) The fabrication process and photograph of the sensor; (B) SEM micrographs of modified copper layer; (C) The electrochemical responses towards standard nitrate samples.

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C1-Oral-02 Liquid-junction-free reference electrode system for amperometry using a closed bipolar electrode Kumi Y. Inoue, Miho Ikegawa, Takahiro Ito-Sasaki, Shinichiro Takano, Hitoshi Shiku, Tomokazu Matsue Graduate School of Environmental Studies, Tohoku University, 6-6-11-604 Aramaki, Aoba, Sendai 980-8579, Japan Email: [email protected]

We report a liquid-junction-free reference electrode system for amperometry using closed bipolar electrode. Liquid junction between a cell containing a reference electrode (reference cell) and another cell contain analyte (sample cell) was replaced by a bipolar electrode to supply not ion but electron transfer between the cells. Under the condition that the redox reaction of analyte at a pole of bipolar electrode is a limiting process of the whole system, we can conduct voltammetric and amperometric quantitative detection using this system. After a basic characterization of the system, we fabricated a chip-type device having six sample cells with one reference cell (Fig. 1A). We successfully calibrated 0.1-0.5 mM ferrocenemethanol by simultaneous six amperometric measurements using the device (Fig. 1B). This is an innovative technology for electrochemical measurements to solve the problem derived from liquid junction of the reference electrode, including the sample contamination by chloride ion, high liquid junction potential especially in case of non-aqueous sample solution, and complicated fabrication process of the proper reference electrode on a chip.

Figure 1. (A) Photograph showing a part of our fabricated device. (B) Detection mechanism of our liquid-junction-free reference system using a closed bipolar electrode.

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C1-Oral-03 The potency of Fe3O4 / MWCNT nanocomposite synthesized from local iron sand for electrochemical biosensor Retno Rahmawatia,b, Ahmad Taufiqc, Sunaryonoc, Yusuke Yamauchid,e, Yusuf Valentino Kanetid, Brian Yuliartoa*, Suyatmana, Nugrahaa, Deddy Kurniadia a

Department of Engineering Physics, Faculty of Industrial Technology, Institut Teknologi Bandung, Jl. Ganesha10, Bandung 40132, Indonesia b Departement of Physics, Faculty of Sciences and Technology, UIN Sunan Kalijaga Yogyakarta, Jl. Marsda Adisucipto No 1 Yogyakarta 55281, Indonesia c Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Negeri Malang (State University of Malang), Jl. Semarang 5 Malang 65145, Indonesia d International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan e Australian Institute for Innovative Materials (AIIM) University of Wollongong, North Wollongong, NSW 2500, Australia *Email: [email protected]

The electrochemical biosensor is the easiest methods for detect biological samples, however the sensitivity and selectivity of biosensor are very depend on sensitive layer of working electrodes. The aim of this research is produce the sensitive layer for working electrode based on Fe3O4/ MWCNT nanocomposite. Moreover, the Fe3O4 for nanocomposite was synthesized from local iron sand as starting material. The methods for obtain Fe3O4/MWCNT nanocomposite using sonochemical methods. The results of X-Ray Diffraction (XRD) show that there are two phase of crystalline of MWCNT and Fe3O4, where in MWCNT has a hexagonal structure and Fe3O4 has invers spinel cubic structure, respectively. The results of Fourier Transform Infrared Spectroscopy (FTIR) data analysis show that the process of functionalization of MWCNT was successfully generated carboxyl and carbonyl groups for bind Fe3O4 on MWCNT surfaces. Meanwhile, the morphology of nanocomposite is strongly influenced by variations of FeCl solution and MWCNT mass. Some of Fe3O4 particles are attached to the MWCNT surface and some are agglomerated with fellow Fe3O4 particles because of the magnetic forces between the particles. Finally, the electrochemical characterization with Cyclic Voltammetry (CV) show that Fe3O4/MWCNT nanocomposites can be excellent electron transfer material and have high sensitivity. The Fe3O4/ MWCNT nanocomposites with iron sand as starting materials have better electrochemical performance than synthetic chemicals. Based on the result from this research, Fe3O4/MWCNT nanocomposites from local iron sand is very potential for electrochemical biosensor.

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C2-Oral-01 Nata de Coco Membrane on Screen Printed Potentiometric Phenol Sensors Ani Mulyasuryani, Afifah Muhimatul Mustaghfiroh Analytical Chemistry Laboratory, Chemistry Department University of Brawijaya, Jl.Veteran, Malang, East Java, Indonesia Email: mulyasuryani.ub.ac.id

Nata de coco is a bacterial cellulose which is the result of coconut water fermentation. Nata de coco is conducting polymer with 553 µS/cm conductivity and has high mechanical stability. The nata de coco was used as a supporting membrane for the development of potentiometric phenol sensors. The nata de coco membrane containing phenol is coated on the surface of the screen printed carbon electrode. The amount of phenol in the membrane has an effect on the Nernstian factor. The optimum Nernstian factor is generated on the membrane with 70.5 μg phenol. Measurement of phenol solution was carried out at pH = 11, with a cross-sectional area of 1 x 5 mm2 electrode, potential measured versus Ag / AgCl. The electrodes can be used five times the measurement of phenol solution at the concentration range of 10-8-10-4 mol / L with an average Nernstian factor of 55.055 mV / decade.

(a)

(b)

Figure 1. SEM image of membrane nata de coco surface (a) and performance of phenol sensors (b).

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C2-Oral-02 Highly sensitive and selective NO2 gas sensors using multi-shelled WO3 yolkshell structures Jun-Sik Kim, Ji-Wook Yoon, Yun Chan Kang, and Jong-Heun Lee* Department of Materials Science and Engineering, Korea University, Seoul 02841, Republic of Korea Email: [email protected]

Yolk-shell structures are hollow spheres composed of a movable core, multiple shells and void space between them. Since they have high surface-to-volume ratio, rapid and effective mass transfer via thin and permeable shells and potentiality to control gas reforming reactions within micro-reactors, they have recently drawn a lot of attention in the fields of catalysts, batteries, micro-reactors and gas sensors. Especially in the gas sensor application, yolk-shell structures are very useful morphology because high gas accessibility of them could maximize the reaction between the target gas and sensing materials. In this study dense and yolk-shell WO3 spheres (double-shelled and triple-shelled WO3 spheres) were successfully prepared via one-pot ultrasonic spray pyrolysis by simply changing the concentration of source materials. The gas sensing characteristics of dense, double-shelled and triple-shelled WO3 spheres to 50 ppb NO2 and other interference gases were examined in the temperature range of 100-300 ºC. Tripleshelled WO3 showed highest response (resistance ratio = 100-49.0) to 50 ppb NO2 and even had excellent selectivity over 5 ppm acetone, CO, NH3, toluene and ethanol while dense WO3 spheres showed low NO2 response (8.9-3.1) and low selectivity over interfering gases. This results can be attributed to the highly gas accessible yolk-shell morphology with thin and permeable multiple shells formed by the active combustion of sucrose during spray pyrolysis.

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C2-Oral-3 Potentiometric Ascorbic Acid Determination by MBs-Ascorbate Oxidase/GO/IGZO/Al Membrane Assembled on Flexible Sensor Array You-Xiang Wua, Jung-Chuan Choua,b,*, Yi-Hung Liaoc, Chih-Hsien Laia,b, Siao-Jie Yana, and Cian-Yi Wua a

Graduate School of Electronic Engineering, National Yunlin University of Science and Technology, Addr: No. 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan, R.O.C b Department of Electronic Engineering, National Yunlin University of Science and Technology, Addr: No. 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan, R.O.C. c Department of Information and Electronic Commerce Management, TransWorld University, Addr: No.1221, Zhennan Rd., Douliu City, Yunlin County 640, Taiwan R.O.C. Corresponding author: [email protected] (MOST 105-2221-E-224-049)

The magnetic beads (MBs) has been widely applied to biosensor because the MBs can bind specific moieties for biomolecules or particular biomolecules. Therefore, in this study, we proposed the ascorbic acid biosensor based on the graphene oxide (GO)/IGZO/Al sensing membrane modified by the MBs-ascorbate oxidase. The IGZO layer was as sensing membrane because IGZO possessed the high chemical stability. Moreover, we deposited the GO layer onto the IGZO sensing membrane to increase the sensing area of specific surface area and enhanced immobilization of enzyme. The MBs was mixed with ascorbate oxidase solution, and which was immobilized onto the GO layer by covalent binding. To obtain the optimized ratio of MBs-ascorbate oxidase, we investigated the effect of MBs concentration on the average sensitivity. We measured the MBs-ascorbate oxidase/GO/IGZO/Al ascorbic acid biosensor through the voltage-time (V-T) measurement system, and the linear range of L-ascorbic acid concentration were from 0.003 to 2 mM. We observed the biosensor had good average sensitivity, linearity and short response time. Besides, we investigated the stability and selectivity of the biosensor from drift test and interfering test.

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C2-Oral-04 Design of Ag Nanorods for SERS with Sensitivity and Thermal Stability Lingwei Maa*, Zhengjun Zhanga, and Hanchen Huangb a

b

School of Materials Science and Engineering, Tsinghua University, Beijing, China Department of Mechanical and Industrial Engineering, Northeastern University, Boston, USA Email: [email protected]

Surface-enhanced Raman scattering (SERS) has emerged into an important analytical technique for trace molecule detections. The sensitivity and thermal stability of sensors are two critical factors for practical applications. The sensitivity allows the detection of molecules at extremely minute amount, and the thermal stability allows the application in challenging environments such as high temperatures. To simultaneously maximize the sensitivity and thermal stability of nanorod-based SERS substrates, we use the strategies of vacuum control and capping in the glancing angle deposition (GLAD) mode. By adjusting the deposition pressures, we could tailor the mean free path of evaporated particles and accordingly, maximize the nuclei density of Ag nanorod so as to minimize the diameter and maximize the number density of nanorods. Capping the Ag nanorods with high-melting temperature Al2O3 by GLAD without vacuum breaking, we prevent the mass transport from the tips to sides of nanorods through surface diffusion and thereby minimize the coarsening of nanorods at elevated temperatures. The coated substrate maintains well its morphology and SERS performance at temperatures as high as 150 °C, which has been significantly improved by ~100 °C compared with that of bare Ag nanorods. Such tremendous improvement offers us a pathway to fabricate sensitive, thermally stable and easily produced SERS sensors with great potential for practical applications especially at harsh conditions.

Figure 1. (a) SEM and (b) TEM images of Ag nanorods prepared at 87° and under 6×10 −5 Torr, after coating with an ultrathin Al2O3 layer at glancing deposition angle.

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C3-Oral-01 Quantitative analysis of chemicals in unknown system by surface enhanced Raman scattering spectroscopy at trace level Sumeng Zou, Lingwei Ma, Jianghao Li and Zhengjun Zhang School of Materials Science and Engineering, Tsinghua University, Beijing, China Email: [email protected] In recent years, there has been an increased demand for analytical techniques that can provide sensitive, rapid and accurate quantitative measurement. Surface-enhanced Raman scattering (SERS) spectroscopy was demonstrated as a powerful method for ultrasensitive and facile detection widely, e.g., chemical sensing, food safety, environment monitoring, etc. SERS is theorized to utilize a combination of an electromagnetic (EM) mechanism which originated from the excitation of localized surface plasmons at the surface of substrates (e.g., silver, gold, and copper) and a chemical mechanism related to charge transfer (CT) between the substrate and the analyte molecules. The chemical quantitative analysis at trace level has been widely explored with the SERS techniques. However, it still remains a challenge to achieve ultrasensitive but facile, rapid, and inexpensive detection method. In the study, the possibility of portable Raman system based surface-enhanced Raman scattering for a rapid quantitative analysis of specific chemical in unknown environment was investigated. We proposed an approach to calculate concentration of chemicals by serial addition of interest to initial solution to be measured, finding special Raman peak intensity which growth up with the addition of interest and making relationship between peak intensity and incremental of interest. We demonstrated this validity by calculating concentration of Rhb and MG aqueous solution which matches their real concentrations well. Results achieved in this study clearly demonstrate the potential application of this approach for SERS quantitative analysis. Figure1a shows the standard addition of Rhb into aqueous, and it reveals that the intensity of 1507 cm-1 increases with the concentration of Rhb. We plotted the relationship between concentrations of Rhb added compared with the initial solution which is to be estimated vs the peak intensity growth of 1507 cm-1 in Figure 1b.At low concentration, the growth peak intensity of 1507 cm-1 vs the concentration of Rhb added is in a good liner with slope of 7.4e+08. Based on this, we can calculate the concentration of Rhb in the initial solution.

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(A)

(B)

Figure 1. (a) SERS spectrum of Rhb under a serial concentration. (b) Incremental of SERS intensity (ISERS) at 1507 cm-1 as a function of the added Rhb content (CΔRhb) in terms of ISERS vs. CΔRhb.

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C3-Oral-02 A study of deformed TiO2 aggregates - graphene nanocomposites as photoanode for dye-sensitized solar cell Hsueh-Tao Chou1, *, Cheng-Yueh Chen1, Ho-Chun Hsu2 1 2

Department of Electronic Engineering, National Yunlin University of Science and Technology

Graduate School of Engineering Science and Technology, National Yunlin University of Science and Technology; Addr:123 University Rd., Yunlin, Taiwan E-mail: [email protected]

In this study, Deformed TiO2 aggregates (DTA) were mixed with graphene for improving the energy conversion efficiency applied in the photoanode for dye sensitized solar cells (DSSCs). The composite layer (DTA-Graphene) had been successfully deposited on the transparent conductive oxide substrate using the spray coating system. The morphology and photovoltaic properties of composite films were observed by using field emission scanning electron microscope (FESEM) and solar simulator measurement system. The overall thickness of composite layer was 10μm. The particle size of DTA were investigated to be about 350 nm. The dye adsorption of composite film was investigated by using spectrophotometer (V-650). We expected that energy conversion efficiency can be improved by high electron mobility of graphene and high dye adsorption of DTA.

(B)

(A)

Figure 1. (A) Structure of composite layer deposited on the transparent conductive oxide substrate. (B) TEM image shows that the DTA morphology and particle size of DTA.

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C3-Oral-03 Myotube cell-based sensing of insulin analogs with a SPR imaging system Yuki Shiraishia, Hiroaki Shinoharaa,b and Minoru Sugab a b

Graduate School of Innovative Life Science, University of Toyama, 3190 Gofuku Toyama-8555, Japan Graduate School of Science and Engineering, University of Toyama,3190 Gofuku Toyama-8555, Japan Email: [email protected]

The two-dimensional SPR sensor is a bio-imaging system that can observe intracellular protein movement non-invasively without any probes. In our previous study, the intracellular reactions of a rat myotube cell upon the wild type (WT) insulin stimulation were observed with the highresolution of SPR imaging system and the sensing of WT insulin was achieved. In this paper, the SPR responses of rat myotube cell against recombinant insulin analogs were observed. Rat myotube cells were cultured on a gold thin film deposited high refractive glass with a silicone resin chamber. The cell-adhere gold chip was set on the prism in the Kretschmann configuration and subjected to 1hr SPR imaging. HBSS solution was added into the chamber at 5 minutes from the start of observation and subsequently, various concentrations of ultra fast-acting insulins were added at 10 minutes from the start. By the stimulation with ultra-fast-acting insulins, the gradual increase of reflection intensity at individual myotube cell regions started after 10 minutes from the insulin analog injection as similar as WT insulin stimulation. A similar pattern of reflection intensity increase was observed at almost cell regions. On the other hand, the early transient increase of reflection intensity at cell regions was not observed upon the stimulation with the ultra fast-acting insulin, while WT insulin stimulation induced the early response. From the SPR response pattern and the rate of reflection intensity change, the sensing of insulin analogs will be discussed. HBSS Au thin film (50 nm)

Rat myotube cells

Glass substrate M agnificent lens (7 x)

P-polarizer

Prism LED CCD camera

Fig.1 Schematic illustration of the cell-based 2D-SPR sensing system.

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C3-Oral-04 On the dynamics of photo-generated carriers in Si-Ge quantum dots Ngo Ngoc Ha International Training Institute for Materials Science, Hanoi University of Science and Technology, Addr: No 1 - Dai Co Viet Str. Hanoi, Vietnam. Email: [email protected]

Binary alloys of SiGe have attracted much attention as functional materials for advanced electronics in recent years. In this study, we report preparation and characterization SiGe alloys quantum dots with various Ge compositions. The materials have been obtained by co-sputtering, followed by a heat treatment process. X-ray diffraction data and high-resolution electronic transmission images have revealed the formation of single phase nanoparticles in face-centered cubic structure of the SiGe alloys with lattice constant increased with a large range of the Ge composition. Photo-generated carriers in the quantum dots were investigated by mean of transient induced absorption. The carrier relaxation features multiple components, interpreted for different photogenerated carrier relaxation routes. Deep carrier traps, characterized by a long-range Coulombic potential, are identified at the boundary between the Si-Ge quantum dots and the SiO2 host with the ionization energy of about 1 eV. These are responsible for rapid depletion of free carrier population within a few picoseconds after the photo-excitation, which explains the low emissivity of the investigated materials, and also sheds light on the generally low luminescence of SiGe alloy systems.

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12-15 November, 2017, Hanoi, Vietnam

D1-Oral-01 Spatial Selective Surface Functionalization of Surface Plasmon Resonance Biosensor via Thiol-Ene Click reaction Yi-Ming Chen1, Tzu-Heng Wu2, Hui-Wen Liu1, Ya-Ting Tsai3, Hsien-Yeh Chen3*, Chii-Wann Lin1,2* 1

Institute of Biomedical Engineering, National Taiwan University, No. 49, Fanglan Rd., Da'an Dist., Taipei, Taiwan 2 Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, No. 49, Fanglan Rd., Da'an Dist., Taipei, Taiwan 3 Institute of Chemical Engineering, National Taiwan University, No.1, Sec. 4 Roosevelt Rd., Taipei, Taiwan *Corresponding author, email: [email protected], [email protected]

In this study, we proposed a method of surface functionalization using parylene (Poly(pxylylenes) thin film. The polymer film is deposited via chemical vapor deposition (CVD)[1-3], which provides vinyl group for further click reaction. As a proof-of-concept experiment, a 25 mer thiolated DNA probe molecule is anchored on the polymer layer through UV triggered thiol-ene reaction [4,5]. During functionalization, a digital light processing (DLP) system directs UV light to exert spatiotemporal control of the reaction (Fig.1a), while the reaction is closely monitored via Surface Plasmon Resonance (SPR). According to the simulation and experimental results (Fig.1b and Fig.1c), the optimized parylene film thickness should be around 20 nm. Overly thick polymer layer leads to large SPR angle shift beyond working range. Through the DNA functionalization experiment, we demonstrate spatially selective functionalization as shown by SPR signal (Fig.1d). Moreover, the reaction rate is about 8.9 times faster than widely applied thiol-gold reaction.

Figure 1. (a)The cross-section of SPR biosensor chip. (b) Simulation result for SPR angle shift with different thickness of parylene film coated on the chip. (c) Simulation result for SPR curve of the thickness of gold film. (d)The result of spatially selective functionalization. The UV exposure was performed only on Area1. Reference [1] Chen, Hsien-Yeh, et al. (2007) Proceedings of the National Academy of Sciences 104.27: 11173-11178. [2] Chen, Hsien-Yeh, et al. (2010) Langmuir 27.1: 34-48. [3] Wu, Jyun‐Ting, et al. (2012) Macromolecular rapid communications 33.10: 922-927. [4] Posner, Theodor. (1905) European Journal of Inorganic Chemistry 38.1: 646-657. [5] Hoyle, Charles E., et al. (2010) Angewandte Chemie International Edition 49.9: 1540-1573. Acknowledgement: The authors would like to thank National Taiwan University Nano-Electro-Mechanical-Systems research center and Dr. Hsien-Yeh Chen’s research group (National Taiwan University). We thank Minister of Science and Technology of Taiwan for funding support through project MOST105-2221- E-002- 016-MY3.

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D1-Oral-02 Rigidly tethered bis-phosphoric acids: Novel probes for the detection of ferric ions by fluorescence and CD-spectroscopy Jochen Niemeyer*, Frescilia Octa-Smolin University Duisburg-Essen, Institute of Organic Chemistry, Universitätsstr. 7, 45141 Essen, Germany. Email: [email protected]

The 1,1´-binaphthyl-2,2´-diol (BINOL) framework has emerged as one of the privileged chiral backbones for sensing applications. Especially linked and macrocyclic bis-BINOLs were successfuly used for the sensing of chiral analytes.[1] Surprisingly the closely related bis-1,1´-binaphthyl-phosphoric acids have found little attention in this context so far. Diederich reported on the use of covalently tethered bis- and tetraphosphoric acids for the detection of monoand disaccharides by NMR,[2] while our group has reported on a [2] catenane-based bisphosphoric acid, which was used for the stereoselective complexation of chiral diamines.[3] In this account, we describe the straightforward synthesis of a series of bisphosphoric acids (1a-d), featuring two chiral 1,1´-binaphthyl-units which are tethered by rigid, π-conjugated linkers. The nature of the linker has a profound influence on the properties of the bisphosphoric acids, such as their self-association behavior and their interaction with metal ions. This led to the identification of one preferred bisphosphoric acid 1d, which shows selective fluorescence quenching by ferric ions, even in the presence of a variety of other metal ions. Due to the chiral nature of the bisphosphoric acid, the interaction with ferric ions can also be followed by CD-spectroscopy, giving a complementary detection mode with the same probe.[4]

[1] L. Pu, Acc. Chem. Res. 2012, 45, 150-163. [2] U. Neidlein, F. Diederich, Chem. Commun. 1996, 1493-1494; S. Anderson, U. Neidlein, V. Gramlich, F. Diederich, Angew. Chem. Int. Ed. 1995, 34, 1596-1600. [3] R. Mitra, M. Thiele, F. Octa-Smolin, M.C. Letzel, J. Niemeyer, Chem. Commun. 2016, 5977-5980. [4] F. Octa-Smolin, R. Mitra, M. Thiele, C. Daniliuc, L. Stegemann, C. Strassert, J. Niemeyer, Chem. Eur. J. 2017, DOI: 10.1002/chem.201700954.

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D1-Oral-03 Volatile imaging system “Sniff-cam” using alcohol dehydrogenase for ethanol and acetaldehyde after drinking Kenta Iitania, Munire Naisierdinga, Yuuki Hayakawaa, Koji Tomab, Takahiro Arakawab and Kohji Mitsubayashia,b a

Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo, Japan, 113-8510 b Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, 2-3-10 Kanda-Surugadai, Chiyoda-ku, Tokyo, Japan, 101-0062 Email:[email protected]

An volatile imaging system (Sniff-cam) was developed for visualization of spatiotemporal distribution of gaseous ethanol (EtOH) and acetaldehyde (AcH), and it was applied to visualize both volatiles in exhaled breath and skin gas after drinking. The Sniff-cam was constructed with a nicotinamide adenine dinucleotide (NADH) dependent alcohol dehydrogenase (ADH) immobilized mesh, a CCD-camera and a UV-LED array sheet. ADH has been known as one of enzymes that catalyze pH dependent reversible reactions (oxidation/reduction). ADH catalyze oxidization of EtOH with production of AcH and NADH at pH 9.0–10.0. Vice versa, ADH also catalyzes reduction of AcH with consumption of NADH at pH 6.0–7.0. Coenzyme NADH shows auto-fluorescence at 490 nm wavelength by UV irradiation at 340 nm wavelength. Therefore, quantitative imaging of EtOH (or AcH) was possible by measuring increase (or decrease) of fluorescence intensity of NADH on the ADH-immobilized mesh. The ADH Sniff-cam shows the wide dynamic range against EtOH (0.5–150 ppm) and AcH (0.1–10 ppm) by changing pH value of buffer solutions. As physiological applications, the Sniff-cam succeeded to visualize the gaseous EtOH and AcH in exhaled breath and skin gas after drinking. The Sniff-cam would be useful for non-invasive imaging of volatile chemicals that related some diseases and metabolism conditions.

Figure 1. (a) Detection principles of EtOH and AcH by ADH with NADH. (b) Schematic diagram of the Sniff-cam system. (c) Typical responses to 100 ppm EtOH (left) and 10 ppmd AcH (right), respectively.

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D2-Oral-01 VOC-sensing properties of YSZ-based mixed-potential type gas sensors: Effects of fabrication methods and microstructure of Au-based electrodes Satoshi Ono1, Taro Ueda1, Takayuki Suzuki2, Kai Kamada1, Takeo Hyodo1, and Yasuhiro Shimizu1, * Graduate School of Engineering, Nagasaki University, Japan; *E-mail: [email protected] 2 Gas Equipment R & D Center, Yazaki Energy System Corporation, Japan

1

Volatile organic compounds (VOCs) are harmful gases even in a very low concentration, and hence sensitive and selective gas sensors are necessary to minimize health risks. Among various kinds of gas sensors, solid-electrolyte gas sensors have shown enhanced sensing properties to VOCs by optimizing the sensing electrodes (SE) [1]. We have also reported that the addition of CeO2 to the Au SE of yttria-stabilized zirconia (YSZ)-based gas sensors increased the toluene response [2], probably due to the increase in the electrochemical activities for toluene oxidation. In this study, we focused on the control of thickness and/or composition of the Au and CeO2-added Au SEs, which were fabricated by screen printing or magnetron sputtering, in order to increase the VOCsensing properties. Typical structure of the sensor fabricated is shown in Fig. 1, and response transients of representative sensors, which were fabricated by screen printing, to 50 ppm toluene are shown in Fig. 2. The addition of 4 wt% CeO2 to the Au SE improved the toluene response. In our Figure 1. Schematic view of a YSZpresentation, other compositional and microstructural based sensor. effects on the toluene-response properties and the response mechanism will be discussed in detail. [1] N. Miura et al., Ionics, 20, (2014) 901-925. [2] T. Ueda et al., Sens. Actuators B, submitted.

Figure 2. Response transients of YSZbased sensors using a Au or CeO2added Au SE, which were fabricated by screen printing, to 50 ppm toluene at 550ºC in dry air. 135

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12-15 November, 2017, Hanoi, Vietnam

D2-Oral-02 Analysis of Oxygen Adsorption on Surface of Metal Oxide to Understand Sensing Mechanism of Semiconductor Gas Sensors Koichi Suematsua, Sun Yongjiaob, Ken Watanabea, Maiko Nishiboria, Kengo Shimanoea a

Department of Energy and Material Sciences, Faculty of Engineering Science, Kyushu University, Kasuga, Fukuoka, 816-8580, Japan b Department of Molecular and Material Science, Interdisciplinary Graduate School of Engineering Science, Kyushu University, Kasuga, Fukuoka, 816-8580, Japan Email: [email protected]

Metal oxide based semiconductor gas sensors materials such as SnO2 and In2O3 are widely applied for the base material of commercial gas sensors. Generally, such gas sensors can detect by the surface reaction between adsorbed oxygen and inflammable gases such as CO and C2H5OH with changing the electric resistance. Such change is caused by the consumption of the adsorbed oxygen on the particle surface. However, investigation of the principle effect of the oxygen adsorption on the electric properties using SnO2 and In2O3 based gas sensors is not so much. Recently, we have proposed that two types of oxygen adsorption, O- and O2-, are existed on the SnO2 surface at 300°C in dry atmosphere, and main oxygen adsorption species are transferred to O2- at 350oC. In this study, we investigated the influence of oxygen adsorption on the In2O3 surface as compared with that on SnO2 surface and clarify the relationship between the oxygen adsorption and the electric properties on the In2O3 gas sensors.

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D2-Oral-03 Fast response and reliable humidity sensors based on rGO/TiO2 hybrid composites Seo Yun Park, Seung-Pyo Hong, Yeon Hoo Kim, Jun Min Suh, Tae Hoon Kim and Ho Won Jang* Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Republic of Korea. *

E-mail: [email protected]

It is of great importance to measure and control environmental humidity in industrial, medical, agricultural, aerospace and human comfort. In order to be applicable to various fields, humidity sensors with high response, short response and recovery time, wide humidity detection range are required. Humidity sensors are typically classified into capacitive and resistive-type. Moreover, diverse materials such as metal oxides, polymers have been studied to manufacture sensing devices to detect humidity. However, critical problems of each materials still remained such as significant degradation of sensing performance of metal oxide based humidity sensors and poor stability under high concentration of humidity of polymer based humidity sensors. Therefore, another sensing materials such as two-dimensional (2D) materials have been studied. 2D materials are one of the most attractive sensing materials for humidity sensors due to its large surface to volume ratio and numerous active sites which can adsorb with humidity molecules. Here, we report the synthesis and fabrication of reduced graphene oxide/titanium oxide hybrid composites (rGO/TiO2) based resistive-type humidity sensor. The rGO/TiO2 show great sensing properties such as high sensitivity, short response time and long reliability. In addition to these excellent properties, the significantly simple fabrication process enlarges the potential of rGO/TiO2 humidity sensors for use in next generation on humidity sensors.

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12-15 November, 2017, Hanoi, Vietnam

D3-Oral-01 Gas Sensing Characteristics of metal-doped Tungsten Oxide prepared from (NH4)2WS4 precursor Tae Hoon Kima, Amirhossein Hasanib, Yeon Hoo Kima, Jun Min Suha, Seo Yun Parka, Soo Young Kimb, Ho Won Jang*, a a

Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Republic of Korea. E-mail: [email protected] b

School of Chemical Engineering and Materials Science, Chung-Ang University, Seoul 06974, Republic of Korea

In recent days, there have been increasing attentions toward Internet of Things (IoT) and one of the emerging research area on IoT is about gas sensors to detect harmful agents that can damage human body. In order to fulfill the needs for the IoT, low cost, miniaturized size, and ease of integration with electronic circuits along with high sensing performance are essential for gas sensors. A lot of effort has been made to develop high performance gas sensors that satisfy those criteria. Among various types of gas sensors, semiconducting gas sensors based on metal oxides such as SnO2, In2O3, WO3, TiO2, CuO, and NiO are considered to be the strongest candidates for application in the IoT owing to their small size, simple operation, low cost, and compatibility with integrated circuits. Gas sensing properties of metal oxide nanostructures can be improved by metal decoration on the surface, since metal nanoparticles behave as chemical and electronic sensitizers. Here, we report a facile fabrication method of Au-decorated tungsten oxide thin film using a thermally annealed (NH4)2WS4 precursor under air ambient. It was demonstrated that the (NH4)2WS4 precursor decomposed into WO3 after annealing at 500 oC. Compared to bare WO3 thin film, Au-decorated WO3 thin film showed higher performance in sensing characteristics such as sensitivity, response time and recovery time. We have demonstrated Au-decorated WO3 thin film with simple fabrication process and this method can be used to decorate another metals such as Ag, Ni, and Mo. Metal-decorated WO3 thin films are expected to be applicable to sensor array.

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12-15 November, 2017, Hanoi, Vietnam

D3-Oral-02 A Novel Monolithic Phase sensitive Surface Plasmon Resonace Biosensor Tzu-Heng WU1，Zu-Yi WANG2，Julien VAILLANT3，Hui-Yun LUO 2， Aurelien BRYANT3* and Chii-Wann LIN1,2＊， a

Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, No. 49, Fanglan Rd., Da'an Dist., Taipei, Taiwan b Institute of Biomedical Engineering, National Taiwan University,No. 49, Fanglan Rd., Da'an Dist., Taipei, Taiwan c Laboratoire de Nanotechnologie, Optique et Instrumentation, Universite de Technologie de Troyes, Addr: 12 Rue Marie Curie, 10430 Rosières-prés-Troyes, France Email: [email protected] , [email protected]

In this work we propose novel phase sensitive SPR system based on a homodyne monolithic sensor chip design. A low wavelength tenability source is applied together with a novel phase extraction method [1-2]. Fig.1 (a) demonstrate the results of the phase sensitive chip. We observed a clear interference pattern in overlapping zone of signal beam and reference beam is demonstrated. At Kretschmann angle, we observe a clear decay of signal beam intensity. To extract the phase information from such a homodyne signal, we proposed new phase extraction method. Fig.1 (b) demonstrates the interference signal of our system. The key of this algorithm is that with a phase modulation depth (∆𝜙𝑎 ) of 3.8317, we can simplify our math process and be able to calculate the phase and amplitude signal of our sample. The expression of phase extraction is

𝜙𝑆𝑃𝑅 =

[1+𝐽0 (2∆𝜙𝑎 )−2𝐽02 (∆𝜙𝑎 )]𝑅𝑦 −𝜇𝐽1 (2∆𝜙𝑎 )𝑅𝑋 (1−2𝐽0 (∆𝜙𝑎 ))𝑅𝑋 −𝜇𝐽1 (2∆𝜙𝑎 )𝑅𝑦

.

We measure phase and amplitude signal under different concentration of glucose (cf. Fig.1 (c)). From this result, we estimate a sensitivity around 10-6 RIU.

Figure 1. (a) Interference Fringe observed in water. (b) interferogram signal. (c) phasogram and amplitude signal under D.I. water and concentration from 0.75% to 11% of glucose. References [1] Chang, Chia‐Chen, et al. "Comparative assessment of oriented antibody immobilization on surface plasmon resonance biosensing." Journal of the Chinese Chemical Society 60.12 (2013): 1449-1456. [2] Chuang, Tsung-Liang, et al. "Disposable surface plasmon resonance aptasensor with membrane-based sample handling design for quantitative interferon-gamma detection." Lab on a Chip 14.16 (2014): 2968-2977.

Acknowledgement We thank Minister of Science and Technology of Taiwan for funding support through project MOST 105-2221-E002-016-MY3.

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12-15 November, 2017, Hanoi, Vietnam

D3-Oral-03 Nickel Oxide Decorated Cobalt Oxide Nanorods for Enhanced Benzene Selectivity Jun Min Suha, Young-Seok Shimb, Woonbae Sohna, Taemin L. Kima, Ho Won Janga,* a

Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Republic of Korea b Center for Electronic Materials, Korea Institutes of Science and Technology (KIST), Seoul 02791, Republic of Korea Email: [email protected]

In modern residence, human activities inside buildings has become extensive and recent researches revealed that individuals spent approximately 88% of their day inside buildings. Therefore, indoor air quality has attracted great attention due to potential harmful gases which arise from building products. Since repeated exposure to harmful gases can induce various illnesses and damages to human body, highly sensitive and selective detection of harmful gases is demanded. Herein, we report a facile fabrication method of NiO-decorated Co3O4 nanorods using glancing angle deposition (GAD) in multiple steps. The distribution of NiO is controlled by changing thickness of Ni film. Compared to bare Co3O4 nanorods, NiO-decorated Co3O4 nanorods show enhanced responses to various gases. It is attributed to the utilization of p-p heterojunction between Co3O4 and NiO by forming a hole accumulation layer on NiO and a hole depletion layer on Co 3O4. As Co3O4 nanorods provide major current path, hole depletion layer can contribute to enhanced sensitivity upon gas molecule adsorption. Our results demonstrate that the decoration of NiO by multiple step GAD is an effective method for enhancing gas sensing performance of p-type metal oxide nanostructures.

Figure 1. Cross-sectional SEM images and response transient to various gases (50 ppm) of bare Co3O4 nanorods and NiO-decorated Co3O4 nanorods. 140

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D3-Oral-04 Development of Electrochemical Sensing System for the Detection of Domoic Acid Hafiza Mohamed Zuki*, Norhidayah Mohd Nasri, Fatin Nabilah Muhamad, Azrilawani Ahmad, Marinah Mohd Ariffin School of Marine and Environmental Sciences, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia. Email: [email protected]

Entrapped ninhydrin in PVC film was constructed and immobilised directly on the surface of gold screen–printed electrodes (Au-SPE). Ninhydrin acts as a potential reagent for the detection of toxic domoic acid (DA) in the modified Au-SPE sensing system. The modified ninhydrin-Au-SPE was characterized using cyclic voltammetry (CV) where the electrochemical behaviour of ninhydrinAu-SPE surface was investigated in the range of -0.6 to +0.85 V at 50 mVs-1 scan rate in the presence of 10mM ferricyanide in 0.1 M potassium chloride with 2 hours electrodeposition time. Good responses were observed for ninhydrin-DA redox reactions with linear relationship obtained between peak currents and concentrations. The correlation coefficients obtained were 0.9607 and 0.933 for anodic and cathodic peaks respectively with the evaluated limit of detection obtained in a range of 10-3 M. Meanwhile, the stability studies showed that the sensing system displayed excellent reproducibility and stability (RSD obtained between 0.8% to 1.2% ranges). The data obtained will be further utilized in the development of a biochemical sensor for the detection of domoic acid.

Figure 1. Detection of domoic acid using modified ninhydrin-Au-SPE.

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12-15 November, 2017, Hanoi, Vietnam

D3-Oral-05 Solution-processed metal sulfides for room-temperature NO2 detection Hao Kan, Min Li, Baohui Zhang, Jingyao Liu, Shuqin Yang, Zhixiang Hu, Huan Liu* School of Optical and Electronic Information, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei, 430074, P. R. China. Corresponding Author Email: [email protected]

The recent increase in economic development and environmental awareness has resulted in the need for low-cost and highly efficient detection of toxic gases with low concentrations (ppb-level). Metal sulfides are emerging as a novel class of sensing materials owing to their excellent selectivity to specific compounds, stability, and the possibility to operate at room temperature compared to the metal oxides. Our research focuses on exploring and understanding the room-temperature NO2-sensing properties of lead sulfide (PbS) and bismuth sulfide (Bi2S3) gas sensors. There exist many degrees of freedom in the solution-processable metal sulfides processing, including stoichiometric ratio and materials morphology control, as well as ligand exchange. PbS and Bi2S3 nanostructures of different dimension such as quantum dots, nanorods and nanosheets were investigated. The results suggested that the surface defects and foreign atoms on the surface introduced via the ligand exchange are critical to the gassensing properties of metal sulfides, possibly by influencing the competitive adsorption of NO2 over oxygen in air. With the solution-processed metal sulfides, we have achieved excellent NO2 sensing performance at room temperature, including rapid response and high sensitivity, good reversibility, and outstanding mechanical bending ability.

Figure 1. (a) Absorption spectra of the as-synthesized PbS quantum dots. (b) TEM image of the as-synthesized PbS nanosheets. (c) TEM images of the as-synthesized Bi2S3 nanocrystals. (d) Response curves of gas sensors based on (d) PbS quantum dots and (e) PbS nanosheets toward 50 ppm of NO2 at 25°C. (f) Response curves of gas sensors based on different Bi2S3 nanocrystals toward 10 ppm of NO2 at 25°C.

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E1-Oral-01 QCM-based humidity sensor and sensing properties employing colloidal SnO2 nanocrystals Naibo Gao, Shengming Cheng, Zhaokun Jing, Zhilong Song,Shuqin Yang, Qian Liu, Wenkai Zhang, Hao Kan and Huan Liu* School of Optical and Electronic Information, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei, 430074, P. R. China. Corresponding Author Email: [email protected]

Quartz crystal microbalance (QCM) is one of highly sensitive methods for quality detection, deriving on their simple structure, low operating temperature even at room temperature, and high accuracy (as possible as nano-gram level). In order to improve the sensitivity of QCM gas sensors as well as response/recovery properties, colloidal SnO2 nanocrystals as sensitive materials were employed to detect H2S because of its large specific surface area and filmdeposition at room temperature. The film was uniformly deposited on the surface of QCM by spin coating method. The effects of the film thickness and the microscopic characteristics of the colloidal SnO2 nanocrystals on the gas sensing properties were systematically studied. By optimizing the preparation conditions, the response sensitivity and response/recovery properties at room temperature were highly improved, and the response toward 10 ppm H2S was 300 Hz with the response and recovery time of 150 s/180 s, respectively.

Figure 1. Frequency curve of the SnO2 nanocrystals QCM gas sensor to 10 ppm H2S.

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12-15 November, 2017, Hanoi, Vietnam

E1-Oral-02 Highly sensitive H2S gas sensors based on Pd-doped CuO nanoflowers with low operating temperature Xiaobing Hu, Zhigang Zhu *, Yihua Wu, Lijun Cai School of Environmental and Materials Engineering, College of Engineering, Shanghai Polytechnic University, Shanghai, 201209

Abstract: A facile method was used to prepare Pd-doped CuO nanoflowers with various doping concentrations. The samples were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), inductively coupled plasma atomic emission spectrometer (ICP-AES), and Brunauer - Emmett - Teller (BET) specific surface area analysis. The responses (Rg/Ra or Ra/Rg, where Rg is the resistance in gas, and Ra is the resistance in air) of such sensors exposed to 50 ppm CH4, NO2, C2H5OH, H2S, NH3, and H2 were measured for comparison. For 1.25 wt% Pd-doped CuO nanoflowers, the response (Rg/Ra) to 50 ppm H2S was 123.4 at 80 oC, which was significantly higher than that of pure CuO (Rg/Ra=15.7). Furthermore, excellent stability and repeatability of the gas sensor were also demonstrated. The observed results clearly revealed that it is an important and facile approach to detect the H2S at low operating temperature for practical applications. Keywords: CuO; gas sensor; Pd doping; p-type; low temperature

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E1-Oral-03 Improving efficiency and stability of polymer solar cells via addition of n-type macromolecular additive Changduk Yang Department of Energy Engineering, School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulju-gun, Ulsan, 44919, Republic of Korea Email: [email protected]

Discovery of an easy and powerful way to further improve and stabilize the performance of organic solar cells (OSCs) from the current levels can advance their commercialization. In this work, an unprecedented power-conversion efficiency (PCE) of 11.6% with improved stability is demonstrated by using high-quality n-type macromolecular additive P(NDI2OD-T2) via a simple route without additional processing steps, where the high-quality P(NDI2OD-T2) is isolated by a THF-soaking treatment. We attribute the improved performance to advantageous changes in morphology of photoactive materials induced by the macromolecular additive. In addition, using the ITO-free architecture on flexible PET substrate, we obtain an impressive PCE of 5.66% in macromolecular additive-processed devices. Due to its great applicability and easy accessibility, the use of the macromolecular additive introduced in this study has great potential for broad applications with other OSC systems, which can accelerate the commercial viability of photovoltaic technology.

Figure 1. Chemical structures and characterizations. a, Molecular structures of donors (PTB7 and PTB7-Th), acceptor (PC71BM), and macromolecular additive (P(NDI2OD-T2)). b, Schematic flatband energy diagram. c, GPC profiles of P(NDI2OD-T2) polymers with different molecular weight (High (H-), Initial (I-), and Low (L-)), extracted by THF-soaking. d, UV-Vis absorption spectra of P(NDI2OD-T2) polymers with different molecular weights dissolved in chlorobenzene and formed to film. e, GIWAXD images.

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12-15 November, 2017, Hanoi, Vietnam

E2-Oral-01 Array of Precise Cell-pairs Based on Positive Dielectrophoresis Tomoyuki Yasukawa, Fumio Mizutani Graduate School of Material Science, University of Hyogo Addr: 3-2-1 Kouto, Kamigori, Ako, Hyogo 678-1297, Japan Email: [email protected]

A microwell array electrode has been used to produce vertical pairs with two different types of cells by positive-dielectrophoresis (p-DEP). A microwell array (250,000 wells, 500 × 500) was fabricated on a substrate with indium tin oxide (ITO) layer. Microwells were designed in width for single cell and depth for two cells. Another ITO substrate was mounted on the microwell array via 30 m thick polyester film to form a fluidic channel. Mouse myeloma cells stained in blue were guided in individual microwells by p-DEP within 1 s and stayed at positions with microwells. K562 cells stained in green were also guided into microwells occupied with myeloma cells in blue by p-DEP. Myeloma cells in blue and K562 cells in green were successively trapped into microwells by p-DEP. Both blue and green signals which are indicated the presence of myeloma cells and K562 cells are clearly observed from the individual microwells. These results strongly indicated that two different types of cells are vertically aligned in microwells to form single-cell pairs. We can obtain pairs of different cells within 1 min with the pairing efficiency of approximately 68 %. Next, DC electric pulses were applied to the upper and lower electrodes to form the fused cells. After we applied DC pulses, the green fluorescence signals were observed from the K562 cells. These cells which were removed from microwells by negative DEP (n-DEP), were in spherical shape with both blue and green signals. Thus, the cell pairs can be easily and rapidly fused for producing couplets using electric pulse fields.

10 m 20 m Figure 1. Combined image of myeloma cells stained in blue and K562 cells stained in green fluorescence and microscopy image. Both blue and green fluorescence images and microscopy image of cell collected from microwells after applying DC electric pulses for fusing the single-cell pairs.

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E2-Oral-02 Electrochemical Bridging of Conducting Polymers at the Percolation Threshold for Chemiresistors Krishnan Murugappan, Tabitha Jones, Merel Lefferts, Ben Armitage and Martin R. Castell Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH. Email: [email protected]

Interdigitated Electrodes (IDEs) are electrodes where two opposing metal electrodes are deposited on an inert substrate with a ‘comb’ like structure. IDEs are increasingly being investigated for their use in electrochemical sensors especially in chemiresistors as they exhibit high sensitivity due to their favourable geometry. The fingers in the two combs are separated by a distance usually in the µm range. In this work a thin layer of gold is evaporated onto the IDEs and then annealed at high temperatures to form gold nano islands through the process of ‘dewetting’ thereby converting the micro gaps in between the fingers to nano gaps, which further improves their geometry. These nano gaps are then bridged by conducting polymers at the ‘electrical percolation region’. In a chemiresistor, the conducting polymer/sensing layer is usually deposited as a thin film on the IDEs, which is termed as the ‘thin film region’. However by operating the IDE in the ‘electrical percolation region’ an enhancement of sensitivity and response times can be achieved. The analytic behaviour of these percolation sensors towards the detection of ammonia gas will be investigated.

Figure 1. A thin film chemiresistor is depicted on the left and a chemiresistor in the percolation region containing a network of gold nanoparticles and conducting polymers is shown on the right.

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E2-Oral-03 Investigation of wireless potentiometric glucose biosensor sensing system based on ruthenium dioxide membrane used for homecare Yi-Hung Liaoa a

Department of Information and Electronic Commerce Management, TransWorld University, Addr: No.1221, Zhennan Rd., Douliu City, Yunlin County 640, Taiwan R.O.C. Email: [email protected]

In this study, the wireless glucose biosensor sensing system was proposed. The sensig system which consisted of the glucose biosesor, micorcontroller with liquid crystal display (LCD) and wifi module. The glucose biosensor was prepared with GOx to immobilize on rutenium dioxide membrane by entropment method. The wireless system included a arduino microcontroller which integrated the LCD and wifi modlues. The experimental results will be shown in LCD display in local area and illustrated in the ThingSpeakTM website in remote area, respectively. The ruthenium dioxide (RuO2) sensing membrane was deposited onto indium tin oxide (ITO) andpolyethylene terephthalate (PET) substrates by radio frequency (r. f.) sputtering system. The sputtering operating pressure was 10 mtorr in Ar gas mixed O2 for 5 min. The gas flow rate of the Ar: O2 was 8:4 (in sccm). The radio frequency power was 100W, at 13.56MHz. The ITO and PET substrates was cut into squares 0.5cm × 0.5cm and packaged with epoxy resin. The fabrication processes of the Nafion-GOx/RuO2/PET (ITO) glucose biosensor were shown as follows: the GOx powder was added into the 1ml 0.1M phosphate buffer solution (PBS) as the GOx solution, the GOx solution was uniformly mixed nafion with a volume ratio of 4:3. The nafion-GOx mixture as glucose sensing membrane, and then was dropped on RuO2/PET (ITO).The sensing characteristic measurement for RuO2 based glucose biosensor was used by the voltage-time (V-T) measurement system with a working electrode (biosensor) and Ag/AgCl reference electrode. The wireless glucose biosensor sensing system was shown in Fig. 1.

Figure 1. The schematic diagram of wireless glucose biosensor sensing system, which consisted of glucose biosensor, Ag/AgCl reference electrode, instrument amplifier, arduino microcontroller with LCD and WiFi modules.

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E3-Oral-01 Electrochemical Insulin Sensor Utilizing a DNA Aptamer-Immobilized Electrode Izumi Kuboa, Taiga Eguchia a

Graduate School of Engineering, Soka University 1-236, Tangi-machi, Hachioji, Tokyo, 192-8577, Japan. Email: [email protected]

Certain guanine-rich DNA oligomers form G-quadruplex structure and bind hemin inside. Such DNA oligomers are called hemin-binding DNA aptamer. DNA oligomer with the sequence of 5’GTGGTGGGGGGGGTTGGTAGGGTGTCTTC- 3’ is guanine-rich one and has been reported to bind insulin selectively. This sequence is named IGA3. In this study, we investigated the application of DNA aptamer IGA3 as sensing material for insulin detection. IGA3 forms antiparallel G-quadraplex folding single strand DNA. IGA3 was immobilized onto a gold electrode to determine its activity electrochemically and to examine insulin binding effct to the activity. Peroxidase activity of immobilized IGA3 with hemin was determined by Cyclic Voltammetry using H2O2 as substrate. Cathodic current was observed through electron transfer. Cathodic peak current around -0.4V of the electrode showed the dependence on the concentration of H2O2 up to 30 M and at higher concentration the current reached steady state. Thus the peroxidase activity of IGA3 was confirmed electrochemically. At the concentration of 20-30 M of H2O2, the cathodic peak current decreased by addition of insulin and the decrease depended on the concentration of insulin at the range of 1-5 M. As a result, we demonstrated the usability of IGA3 aptamer for detection insulin.

+

+

2H

2H

H2O2

H2O2

insulin

G GGG G GGG 2e G

GGG G hemin G GGG G 2e

-

-

Figure 1. Scheme of electrochemical detection of insulin

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E3-Oral-02 Development of a Sensitivity-Enhanced Surface Plasmon Resonance Aptasensor for the Detection of Arsenic L.T. Fana, C.H. Yangb, C.C. Changa, T.L. Chuanga , J.S. Laic, W.S. Linc, C.W. Lina a

b

Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan c Hydrotech Research Institute, National Taiwan University, Taipei, Taiwan Email: [email protected]

Arsenic has been contaminating water and soil worldwide due to mineral distribution and industrial pollution. The current detecting technologies are mostly lab-based with complex and delicate equipment, though with extremely low limit of detection (LOD), they are impractical for on-site screening and real-time monitoring. Thus, a rapid screening method is in demand with high sensitivity and a LOD low enough for inspections of agricultural water, reservoir water and wastewater from industrial discharge. The introduction of Systematic Evolution of Ligands by Exponential Enrichment (SELEX) made it possible to develop DNA aptamers affinitive to assigned targets including arsenic. Based on the arsenic-affinitive aptamer developed by M. Kim’s research team, we were able to develop a surface plasmon resonance aptasensor for the detection of arsenic. However, during our research we discovered that the secondary structure of the DNA aptamer inhabited its own sensitivity to the target when being immobilized on the gold nano-film, so we developed a solution to bind a complementary DNA segment to the aptamer on its non-functional site to erect its secondary structure, allowing better exposure to analytes. It was proved effective with enhanced sensitivity by lowered LOD from 10 ppb to 1 ppb, the slope of reaction kinetic line became two times higher. This method was also tested with field sample, resulting in good reproducibility.

(A)

(B)

Figure. (A) The schematic drawing of a bare DNA aptamer and a modified DNA aptamer. (B) The calibration curves of the arsenic sensor with bare aptamers and modified aptamers as probes.

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E3-Oral-03 Electrochemical Properties of Miniature Gas Sensors using Semi-Solid Electrolytes Dong-Yun Lee, Hana Cho, Min-Ho Kang, Sang-Do Han*, Kie-Won Lee* Shinwoo Electronics Co. Ltd., 641, Pureundeulpan-ro, Paltan-myeon, Hwaseong-si, Gyeonggi-do, Republic of Korea * Email: [email protected]

Currently, tocix gas sensors are important using electrochemical method for health, medical, and industrial applications. The most importance of developing electrochemical gas sensors is size miniaturization and lifetime including enhanced electrode and electrolyte. The electrochemical sensor has various advantages because it has various sensing gas depending on the electrode and electrolyte. In addition, attempts to make the sensor devices more intelligent and more quantitative are also important for further advancements of gas sensor technology. In this paper, the miniature electrochemical sensors (square size, 20205mm) are optimized with electrode and part design. Also, the electrochemical properties of gas sensors are investigated with semi-solid electrolyte through the voltage-current graph using the cyclic voltammetry (CV) and measured the current change with the pico-ammeter. And then, the electrical conductivity was measured by the sheet resistance. The CO and SO2 gas are detected high sensitivity and selectively, which is expected to be applicable to various industries.

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E3-Oral-04 Photoelectric Characteristics of Au Nanoparticles Modified ZnO Nanorods Composite Films on ITO Glass Hsueh-Tao Chou1, *, You-Lun Deng1, Wei-Hao Huang1, Yi-Keng Yu 1, Ho-Chun Hsu 2 1.

2.

Department of Electronic Engineering, National Yunlin University of Science and Technology Graduate School of Engineering Science and Technology, National Yunlin University of Science and Technology National Yunlin University of Science and Technology, Addr:123 University Rd., Yunlin, Taiwan E-mail: [email protected]

In this study, Au nanoparticles modified ZnO nanorods composite films on indium tin oxide (ITO) glass were investigated. First, Au nanoparticles solution was prepared by using photochemical method. Then, the ZnO seed layer was deposited on ITO glass with a spin coater, ZnO nanorods were grown by using chemical bath deposition (CBD). Finally, the Au nanoparticles modified on ZnO nanorods was using self-assembly method with APTES solution, and it was annealed at 350 ºC for 30 minutes. The AuNPs/ZnO composite films were measured by using field emission scanning electron microscopy (FE-SEM), UV–vis absorption spectroscopy, cyclic voltammetry (CV) and the electrochemical impedance spectroscopy (EIS). Au nanoparticles successfully modified on ZnO nanorods was observed by SEM image. The results showed the ZnO film enhanced its visible light absorption range by coating Au nanoparticles, the absorbance peak was significantly improved after annealing. Moreover, the electrochemical characteristics were examined by using the CV and the EIS, the results showed the reversibility of AuNPS/ZnO composite film, and the impedance was decreased by coating Au nanoparticles. All results showed the potential application of AuNPs/ZnO composite film for biosensor.

Figure 1. Structure of Au nanoparticle modified ZnO composite film on ITO glass, and the UV-Visible absorption spectra of AuNPs/ZnO film.

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E3-Oral-05 Cr2O3/ZnCr2O4 hetero-nanostructures for ultraselective and sensitive detection of xylene Jae-Hyeok Kim, Hyun-Mook Jeong, Chan Woong Na, Ji-Won Yoon, and Jong-Heun Lee Department of Materials Science and Engineering, Korea University, Seoul 02841, Republic of Korea. Email: [email protected]

Gas sensing characteristics of metal oxide semiconductor chemiresistors can be significantly enhanced by forming hetero-nanostructures. In this study, Cr2O3/ZnCr2O4 hetero-nanostructures were synthesized by galvanic replacement reaction and their gas sensing characteristics were investigated. In the present contribution, the ZnO hollow spheres were prepared by ultrasonic spray pyrolysis, which were gradually replaced by Cr component in solution to form ZnCr2O4 phase and Cr2O3/ZnCr2O4 nanocomposites. The uniform composite between nanocrystalline Cr2O3 and ZnCr2O4 showed a high gas response of 69.2 to 5 ppm xylene and its response was significantly higher than other interfering gases (Rg/Ra) such as ethanol, acetone, methanol, benzene, formaldehyde, carbon monoxide, and ammonia (Rg/Ra = 1.2 - 3.9) at 275 °C. In contrast, both pure ZnO and Cr2O3 showed higher responses to ethanol than xylene, and no significant response and selectivity to any specific gas were found for the single-phased ZnCr2O4 powders. Considering the sensing characteristics, designing of oxide hetero-nanostructures is an effective way to enhance specific gas response and selectivity. This result can be explained by synergistic catalytic effect between Cr2O3 and ZnCr2O4 both with high catalytic activity to oxidize methyl benzenes. Galvanic replacement reaction is a facile method to form uniformly and intimately mixed nanocomposites, which enables synergistic combination of catalytic activity of two different materials. Therefore, the galvanic replacement reaction is a promising method for synthesizing high-performance gas sensors using oxide hetero-nanostructures.

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Poster Section

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P001 Hydrothermal synthesis of CuO nanoplates and their gas sensing characteristics Ngo Thi Ut1,2, Dang Thi Thanh Le1 and Nguyen Duc Hoa1* 1

International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, Hanoi, Vietnam 2 School of Engineering Physics, Hanoi University of Science and Technology, Hanoi, Vietnam Email: [email protected]

Metal oxides have been the most selected candidates used for resistive type gas sensors due to their advanced characteristics such as high thermal stability but still offer high gas sensitivity. Among others, CuO is one of the most important p-type semiconductor metal oxides with a narrow band-gap between 1.2 and 1.5 eV, and has been extensively applied in gas sensors. To maximize the sensor response and reduce the fabrication expense, nanostructures are of priority. Thus efforts have been focused on the fabrication of nanostructured CuO with various geometries such as nanorods, nanowires, and nanoflowers. Herein, we prepared CuO nanoplates by hydrothermal method for gas sensor applications. The hydrothermally synthesized CuO nanoplates have a two dimensional morphology of few hundreds nanometers in size and about dozen nanometers in thickness, thus offering exceptional high surface area for gaseous molecules to absorb in sensor applications. 1.6k

(A)

(A) (B)

Resistance ()

1.6k

0.5 ppm H2S

1.5k 1.5k 1.4k 1.4k

200 nm

0

200

400

600

800

1000

1200

Time (s)

Figure 1. (A) SEM image, and (B) H2S response of CuO nanoplates prepared by hydrothermal method.

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P002 P-N Sensing Response of SnS2-SnO2 Nanoflowers Exposed to NH3 Gas Di Liua, Zilong Tang*a, Yesheng Lib and Zhongtai Zhangb a

State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China Email: [email protected]

Tin disulfide nanostructured material has become a new gas sensing material thanks to its room temperature sensing properties. In this study, tin disulfide nanoflowers have been synthesized using SnCl4•5H2O obtained through hydrolysis method as tin source. SnS2-SnO2 nanoflowers have been successfully prepared by in-situ thermal oxidizing pristine SnS2 in air at 350 ℃. Chemiresistor gas sensors based on thick films of synthesized SnS2-SnO2 were fabricated by means of screen-printing technology. The SnS2-SnO2 nanoflower gas sensor exhibited sensitive response to NH3 at room temperature and abnormal p-n response behaviors were observed. The abnormal p-n sensing response may be attributed to the electron transfer from the SnS2 nanosheets to the SnO2 nanoparticles leading to p-type channels at the heterogeneous interfaces of SnS2-SnO2. The sensing mechanism of SnS2-SnO2 has been investigated in details. The results show that the as-synthesized SnS2-SnO2 nanoflowers can be used as a promising selective gas sensor material.

Figure 1. (A) TEM image of the as-prepared SnS2-SnO2 nanoflower; (B) Repeatability of SnS2-SnO2 sensor to 1000 ppm NH3 during the three testing cycles at room temperature.

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P003

Buffered-oxide-etchant Post-treated silicon Nanowire Network for Enhanced Hydrogen Sensing Performance. Min Gaoa, Inkyu Parka a

Deparment of Mechnical Engineering, Korea Advanced Institute of Science and Technology (KAIST) Addr: 291 Daehak-ro, Guseong-dong, Yuseong-gu, Daejeon, South Korea Email: [email protected]

In this work, an n-type silicon nanowire network structure with palladium (Pd) is applied as a highperformance hydrogen (H2) gas sensor. The silicon nano-patterned structure is fabricated by using the self-assembly of polystyrene nanospheres, which is a cost-efficient and scalable fabrication technique up to wafer-level. Simple buffered-oxide-etchant (BOE) treatment for the silicon structure is found to be effective for H2 sensing enhancement after the functionalized with Pd nanoparticles. Herein, H2 sensing properties are explored based on the structure with various BOE treating time. Ultimately, the sensor device shows enlarged sensitivity with BOE treating time from 0 to 2 min, and the sensing resolution becomes better with 2 min BOE treated silicon structure. The sensor is working in stable, and no noticeable performance degradations occurred after one month. The cost-effective, IC compatible and scalable method for nano-patterning of Si via selfassembly of nanosphere and effective BOE treated structure for doped silicon could be further applied to other gas/chemical sensor application based silicon nanostructure.

Figure 1. (a) schematics of the hydrogen sensor based on Pd-decorated Si nanowire network and (b) real-time sensing performance under different BOE treating time.

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P004 CO2 sensing properties of Zr-added CaFe2O4-based sensor Yuki Obukuroa, Keisuke Mizutab, Kenji Obatab, Shigenori Matsushimab* a

Department of Materials System Engineering, National Institute of Technology (NIT), Kurume College, 1-1-1 Komorino, Kurume, Fukuoka 830-8555, Japan b Department of Creative Engineering, National Institute of Technology (NIT), Kitakyushu College, 5-20-1 Shii, Kokuraminami-ku, Kitakyushu 802-0985, Japan E-mail: [email protected] Abstract CO2 sensing properties of Zr-added CaFe2O4-based sensor were examined in the temperature range of 250 – 450 °C under dry air condition. The gas sensitivity of Zr-added CaFe2O4-based sensor at 300 and 350 °C was estimated to be 2.9 times higher than that of the sensor made from pure CaFe2O4 powder. The 90% response time of the Zr-added CaFe2O4-based sensor was much faster at 350 °C than that at 300 °C. Also, the Zr-added CaFe2O4-based sensor responded reversibly as well as continuously to CO2.

Gas sensitivity

1. Introduction Recently, we found that the addition of Zr into CaFe2O4 forms a characteristic porous structure, resulting in higher specific surface area compared with unadded one [1]. In the present study, we investigated the CO2 sensing properties of Zr-added CaFe2O4 materials in detail. 2. Experimental method Zr-added CaFe2O4 powders were prepared from a malic acid complex method [1]. The Zr-added CaFe2O4 powders were mixed with -terpineol, and the resulting paste was applied on an alumina tube attached to a pair of Pt-wire electrodes. The sensor element was fabricated by heating the entire assembly at 600 °C in air. The CO2 sensing properties were measured in a gas flow apparatus equipped with heating facilities in the temperature range of 250 – 450 °C. The CO2 concentration was changed in the range of 0 – 5000 ppm by diluting CO2 gas with dry air. The gas sensitivity (S) was defined as Rair/Rgas, where Rair and Rgas were the electric resistances of a sensor element in air and in a sample gas, respectively. 3.8 3. Results and discussion 1 mol% Zr 3 mol% Zr Fig. 1 compares the CO2 sensitivities of Zr-added 3.3 5 mol% Zr CaFe2O4-based sensors to 5000 ppm CO2 in the 7 mol% Zr 10 mol% Zr 2.8 temperature range of 250 – 450 °C. Among six unadded kinds of the sensors examined, 5 mol% Zr-added 2.3 CaFe2O4-based sensor showed a maximum at 300 1.8 and 350 °C. However, the 90% response time of the Zr-added CaFe2O4-based sensor was much quicker 1.3 at 350 °C than that of at 300 °C. Therefore, the optimal gas sensing performance of the Zr-added 0.8 250 300 350 400 450 CaFe2O4-based sensor would be obtained at the Temperature / ℃ measuring temperature of 350 °C, considering the Fig. 1 Dependence on operating temperature still higher sensitivity to CO2. of the gas sensitivity of Zr-added CaFe O – 2

based sensors to 5000 ppm CO2.

4

Acknowledgment This work was partially supported by a Grant-in-Aid for Scientific Research [Grant No. (C) 16K06782] and Mazda Motor Corporation [Grant No. 14KK-144]. References [1] Y. Obukuro, K. Obata, R. Maeda, S. Matsushima, Y. Okuyama, N. Matsunaga, G. Sakai, J. Ceram. Soc. Japan, 123, 995-998 (2015).

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P005 Quick detection of IgA for mobile stress monitoring Takeshi Ito, Takeshi Nanushigawa, Tomohiro Shimizu, Shoso Shingubara Faculty of Engineering Science, Kansai University, Japan; Email: [email protected]

Monitoring psychological stress level is very important for workers to live a life with healthy. There are some stress markers such as adrenaline, cortisol, amylase, and IgA (immunoglobulin A). IgA has a relationship with immune function, and the concentration of IgA responds in a load of acute stress. In addition, IgA is involved in human saliva. Then, it is easy to analyze the IgA level in the saliva without invasive method. We propose a mobile IgA detection system coupling with a microfluidic device and a quartz crystal microbalance (QCM) method for easy to use as shown in Fig. 1. In fact, there is no kinetic pump and valves, only dropping a sample solution. QCM is known as a real time measurement with simplicity, convenience and low cost. QCM is one of candidates for highly sensitive immune sensor, however, it has the problem about considerable noise level caused by measurement environment, such as temperature and density of surrounding media. Since twin sensor removes these environmental influences, noise level can be decreased drastically. Twin sensor has two reaction regions on one AT–cut quartz crystal substrate. One channel was used as a reference (Ch2) and the other channel measured IgA adsorption corresponding to antigen-antibody reaction (Ch1). Then, difference of the frequency change between the Ch1 and Ch2 was monitored. We compared two detection techniques for IgA. One was using flow injection analysis method (FIA) composed of microsyringe pump, injection valve, and tubes. The other was named as a mobile, using capillary force with a micro fluidic device and a sponge. Analytical curve on using mobile device is equivalent with that on FIA as shown in Fig. 2.

Fig. 2 Analytical curves of the IgA detection in case of the FIA (solid circles) and the mobile system (open squares).

Fig. 1 Schematic figure of mobile IgA detection system composed of a QCM, a microfluidic device and a sponge. 161

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P006 Chemometric analysis of sensory data obtained with an electronic nose Marta I.S. Veríssimoa,b, João A.B.P. Oliveiraa, M. Teresa S.R.Gomesa* a b

CESAM/University of Aveiro, Campus of Santiago, 3810-193 Aveiro, PORTUGAL CICECO/University of Aveiro, Campus of Santiago, 3810-193 Aveiro, PORTUGAL *Email: [email protected]

The detection of volatile compounds (VC) is an important issue since they are everywhere in outdoor and indoor environments, and in other contexts to flag the presence drugs of abuse, weapons and even diseases. To achieve this there is an increasing use of arrays of chemical sensors which constitutes an electronic nose (e-nose) a technique that can be used remotely. The drawback is that the output of such an array is multivariate therefore needs chemometric techniques to extract useful information. In this study we compared three classification methods, principal component analysis (PCA), linear discriminant analysis (LDA) and cluster analysis (CA), applied to the concentration patterns of the VC isolated from books from different provenances, with the aim of distinguishing them according to their condition. The analysis of these compounds present in the books using the e-nose method, has a series of advantages over other analytical techniques due to simplicity of the sample-preparation and reduced time of analysis and might be considered as a more convenient choice for routine process control in a library environment.

Figure 1. Chemometric analysis of sensory data from volatile compounds of books.

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P007 Fabrication of electrochemical electrodes based on platinum and ZnO nanofibers for biosensing applications Nguyen Thi Hong Phuoc1, Nguyen Van Hoang1, Dang Thi Thanh Le1,*, Matteo Tonezzer2, Tran Quang Huy3, Nguyen Van Hieu1 1 ITIMS, Hanoi University of Science and Technology (HUST), No.1, Dai Co Viet Str., Hanoi, Vietnam 2 IMEM-CNR, sede di Trento - FBK, Via alla Cascata 56/C, Povo - Trento, Italy 3 NIHE, No.1 Yersin, Hanoi, Vietnam *Corresponding author: [email protected] Abstract. Platinum (Pt) electrodes were designed in imitation of screen-printed electrodes, and prepared by microelectronic techniques, these electrodes were then modified with zinc oxide (ZnO) nanofibers for biosensing applications. ZnO nanofibers with average length 20-30 μm and diameter 150 nm in hexagonal crystalline structure prepared using electrospinning method. Their surface characteristics were analyzed by field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. Electrochemical properties of modified Pt electrodes were investigated in comparison with commercial carbon screen-printed electrodes. The results showed that the cyclic voltammogram of modified Pt electrodes was stable, but have much lower resistance comparing to that of carbon screen-printed electrodes.

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P008 Adsorption Behavior of H2O, OH and H to Sr–Ca–Cu–O Superconducting Materials Akira Fujimoto, Satoshi Shinodaa, Tadachika Nakayamaa and Hisayuki Suematsua National Institute of Technology, Numazu College, 3600, Ooka, Numazu, Shizuoka 410-8501 Japan. a Nagaoka University of Technology, 1603-1, Kamitomioka Nagaoka, Niigata 940-2188, Japan. Email: [email protected]

Adsorbed oxygen affects strongly to the superconducting characteristics such as critical current and irreversibility magnetic field of the Sr-Ca-Cu-O. Adsorption behavior of H2O, H and O to the Sr–Ca–Cu–O material was investigated by molecular orbital calculations. Figure 1 shows Sr-Ca-Cu-O cluster for calculation. H2O molecular, H+ and OH- species were closing to the cluster from (100) and (110) direction as shown in figure 2. Total heats of formations were calculated for the cluster and closing molecular or species. PM5 Hamiltonian was used for the calculation. Figure 3 shows the heat of formation change with closing H2O molecular to (100) plain of the cluster. The heat of formation increases monotonically with closing H2O molecular. It is supposed that no adsorption and reaction will occur under this situation. On the other hand, the heat of formation touch bottom at distance of 3 angstroms between the cluster and OH species in the case of OH close to (110) plane of the cluster. OH species will be adsorbed stably at the distance on the cluster surface and will affect to superconducting characteristics. Heats of formation changes were calculated for several kinds of species and molecular with closing to different plane of the cluster. These results suggest that Sr-Ca-Cu-O material can detect H2O, OH and H by superconducting characteristics change as a new sensor.

O Sr Cu Ca

Fig.1

Fig.2 164

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Fig.3

Fig.4

Figure 1. Sr-Ca-Cu-O cluster for molecular orbital calculation. Figure 2. Schematic view of Sr-Ca-Cu-O cluster with closing H2O, OH and H. Figure 3. Heat of formation change of Sr-Ca-Cu-O cluster with closing H2O molecular to (100) plane. Figure 4. Heat of formation change of Sr-Ca-Cu-O cluster with closing OH species to (110) plane. OH will adsorb at 3 angstroms from cluster surface.

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P009 Effect of other atoms on CO2 sensing properties of CaFe2O4 Kenji OBATAa, Keisuke MIZUTAa, Yuki Obukurob, Shigenori MATSUSHIMAa* a

Department of Creative Engineering, National Institute of Technology (NIT), Kitakyushu College, 5-20-1 Shii, Kokuraminami-ku, Kitakyushu 802-0985, Japan b

Department of Materials System Engineering, National Institute of Technology (NIT), Kurume College, 1-1-1 Komorino, Kurume, Fukuoka 830-8555, Japan E-mail: [email protected]

Abstract In this study, we investigated the effect of other atoms on the CO2 sensing properties of CaFe2O4. We prepared CaFe2O4 powders using the malic acid complex (MAC) and polymerized complex (PC) methods. Then, we examined the CO2 sensing properties of a CaFe2O4-based sensor with other added atoms, inclusing Si, Ti, Hf, and Zr in the temperature range of 250 °C to 450 °C in dry air. At 300 °C and 350 °C, the CO2 sensitivity of the CaFe2O4 in MAC was improved by adding a small amount of impurity atoms such as Zr or Hf in comparison with that having no added atoms. The 90% response time of the M-added CaFe2O4-based sensor was much quicker at 350 °C than at 300 °C. The CO2 sensitivity of the 5 mol% Zr-added CaFe2O4 sensor reached maximum at 300 °C and 350 °C, which we estimated to be 2.9 times higher than that of pure CaFe2O4. Keywords: CaFe2O4, Zr addition, CO2 sensor, Morphology, resistive-type sensor

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P010 One-pot hydrothermal synthesis of rGO/WO3 nanocomposites Do Quang Dat1,2, Chu Manh Hung2, Nguyen Duc Hoa2*, 1

Department of Natural Sciences, HoaLu University, Ninh Nhat, Ninh Binh City, Vietnam International Training Institute for Materials Science, Hanoi University of Science and Technology, Addr: No 1 - Dai Co Viet Str. Hanoi, Vietnam. Email: [email protected]

2

Resistive gas sensor is a device which measures the change in electrical resistance of sensing materials upon exposure to analytic gases. Due to their simple design and fabrication, as well as high sensitivity, resistive gas sensors have been applied in various fields such as air quality monitoring, breath analysis, etc. Recently, rGO/WO3 nanocomposite has been extensively studied for room temperature gas sensors thanks to its exceptional physical properties. There are many methods used to synthesize rGO/WO3 nanocomposite. However, synthesis of rGO/WO3 nanocomposite mostly used complicate processes. Herein, we report a facile synthesis of rGO/WO3 nanocomposite by a one-pot hydrothermal method. By varying the synthesis condition, we can control the morphology and composition of materials. Material characterization confirms that the synthesized rGO/WO3 nanocomposite is high quality for application in room temperature gas sensors.

rGO/WO3

Intensity

WO3

WO3 D-band G-band

200 400 600 800 1000 1200 1400 1600 1800 2000 -1

Raman shiftcm 

Figure 1. SEM image and Raman spectrum of rGO/WO3

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P011 VO2 nanostructures for temperature sensing applications Amir Abidov, Sungjin Kim Department of Advanced Materials Science and Engineering, Kumoh National Institute of Technology, 61 – Daehak-ro, Gumi-si, Gyeongbuk, Republic of Korea. Email: [email protected]

Vanadium dioxide is under high attention due to its unique thermochromic properties. Such as electrical properties reversible change due to temperature. Here were present VO2 nanostructures for temperature sensing applications. Sensor was fabricated on glass substrate with predeposited silver contacts pattern. Temperature was increased from 20 to 80 degrees Celsius with 1 oC step. It was observed that resistance of sensor decreases with increasing temperature until 80 oC. Samples were analyzed using X-ray diffractometer for crystal structure. Morphology was obtained using Scanning Electron Microscope. Data was analyzed and discussed.

Figure 1. Resistivity of VO2 film as function of temperature

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The 12th Asian Conference on Chemical Sensors (ACCS2017)

12-15 November, 2017, Hanoi, Vietnam

P012 Primitive Study of Dual Biosensor Coupling with Localized Surface Plasmon Resonance and QCM-D Using Anodic Aluminum Oxide Substrate H. Terasawa, T. Shimizu, S. Shingubara, and T. Ito* Faculty of Engineering Science, Kansai Univ., Japan; *Email: [email protected]

Localized surface plasmon resonance (LSPR) is due to plasmon excited in nanostructured metals, and is a highly sensitive to change in the refractive index of the sensing surface. Advantage of the LSPR comparing to surface plasmon resonance (SPR) is simplicity of the equipment. Then, LSPR attracts attention during the past decade for biosensing. In the contrast, QCM-D reveals the information of molecular interactions by viscoelasticity of materials, and measure mass change corresponding to adsorption of target material onto the sensor surface by frequency shift. These two sensing techniques have been compared indirectly by using independent measurement equipment by many researchers. Then, these techniques have strong and weak points with each other. We developed a dual biosensor coupled with LSPR and QCMD on a sensor device and report primitive characteristics of it in this report. We used Anodic Aluminum Oxide (AAO) to excite LSPR. AAO has some advantages that it can easily fabricated periodic nanoporous structure at a low cost. We fabricated an optical sensor using both the excitation of LSPR and the interference effect by depositing a metal thin film on the AAO, which was fabricated by anodizing Al thin film deposited on a QCM chip. As a primary evaluation of the biosensor application, Bovine Serum Albumin (BSA) which is one of major protein was absorbed on the sensor surface and measured response by both sensors.

Figure 1 (A) Photo of the fabricated sensor chip which excited LSPR. The surface of a QCM chip coated with Au/AAO showed red color. (B) Reflectance spectra on the fabricated sensor chip. Red and blue lines shows the spectrum before and after the adsorption of BSA (1mg/mL).

References [1] N. Asai, T. Ito, T. Shimizu, S. Shingubara, ECS Transactions, 75 (16), 229-232 (2016). [2] T. Ito, Y. Matsuda, T. Jinba, N. Asai, T. Shimizu, S. Shingubara, Japanese Journal of Applied Physics, 56, 06GG02 (2017). 169

The 12th Asian Conference on Chemical Sensors (ACCS2017)

12-15 November, 2017, Hanoi, Vietnam

P013 Keratin modified carbon paste electrode for arsenic detection Hannah C. Valenciaa, Marivic S. Lacsamana, Milagros M. Peralta and Veronica C. Sabularse Institute of Chemistry, University of the Phiippines Los Baños, College, Laguna, Philippines 4031. Email: [email protected]

Keratin from human head hair was used as modifier for carbon paste electrode for the detection of arsenic. The reduction of arsenic (III) was carried out in 0.1 M acetate buffer pH 4.7 solution and the oxidation peak wave was measured using Ag/AgCl as reference electrode and Ti/Pt as auxillary electrode by differential pulse anodic stripping voltammetry. Arsenic (III) was accumulated on the surface of the electrode based on its interaction with the thiol and disulfide groups of keratin. The limit of detection of arsenic (III) was 5.74 ppm at 180 s accumulation time, -300 mV deposition potential and 180 s deposition time.

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12-15 November, 2017, Hanoi, Vietnam

P014 Design of Gold Nanoband Sensor for Determination of Mercury Ion in Water Jiawei Tu, Qiyong Sun, Ying Gan, Tao Liang, Qiongwen Hu, Ping Wang* Biosensor National Special Laboratory, Department of Biomedical Engineering, Zhejiang University, Hangzhou, 310027, China *Corresponding Tel/Fax:+86 571 87952832, Email: [email protected]; [email protected]

Abstract: The mercuric ion is a widespread pollutant in the environment, with high toxicity and several dangers to both environment and human health. A gold nanoband sensor with a very simple structure for mercury ion determination is described in this study. The gold nanoband sensor is integrated of three electrodes by microfabrication technology, including of the gold nanoband working electrode, the silver reference electrode and gold counter electrode. The silver reference electrode and gold counter electrode is fabricated by photolithography with several lithography masks. The gold nanoband working electrode is exposed by sawing wafer with precision silicon knife. The gold nanoband sensor has the advantages of high nonlinear diffusion, low analyte consumption, fast sensing time and suited for target metal ion determination. Herein, the sensor was used for Hg2+ ion measurement, and both the capabilities of the gold nanoband working and silver reference electrodes were characterized by using electrochemical techniques. The results show that the sensor performed with high sensitivity, and good reproducibility in Hg2+ determination by square wave stripping voltammetry (SWSV). The detection range extends from 100 to 400 ng/L with a good linear correlation and the detection limit is 50ng/L. Keywords: Nanoband sensor, Mercury ion determination, Electrochemical sensor

Figure 1. (a) Photograph of gold nanoband sensor (b) Diagram of gold nanoband sensor with and without Si3N4 insulating layer. (c) Voltammetry curves of Hg2+ detection. (d) Standard curves of Hg2+ detection with R2 of 0.9906. 171

The 12th Asian Conference on Chemical Sensors (ACCS2017)

12-15 November, 2017, Hanoi, Vietnam

P015 Characteristics of Counter Electrode Modified by Reduced Graphene Oxide for Dye-sensitized Solar Cell Chung-Ming Yanga, Jung-Chuan Choua, b,*, Yi-Hung Liaoc, Chih-Hsien Laia,b, Wan-Yu Hsua and Pei-Hong Youb a

Department of Electronic Engineering, National Yunlin University of Science and Technology, Yuniln, Taiwan. Addr: No. 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan, R.O.C. b

Graduate School of Electronic Engineering, National Yunlin University of Science and Technology, Yunlin, Taiwan. Addr: No. 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan, R.O.C

c

Department of Information and Electronic Commerce Management, TransWorld University, Yunlin, Taiwan. Addr: No.1221, Zhennan Rd., Douliu City, Yunlin County 640, Taiwan R.O.C. *

Email: [email protected]

Abstract In this research, we used radio frequency (R. F.) sputtering method to deposit the aluminum doped zinc oxide (AZO) film as a barrier layer on titanium dioxide (TiO2) double layers of photoelectrode for dye-sensitized solar cell (DSSC). Reduced graphene oxide (rGO), a two dimensional material, has the advantages such as large specific surface area (a theoretical value of 2630 m2/g), high chemical tolerance and high structural flexibility. Because of its excellent electrochemical properties, which is widely used as a material for optoelectronic components. To reduce the volume of platinum (Pt) for counter electrode, we used rGO to modify the counter electrode. The rGO was deposited on Pt counter electrode, which deposition time was less than normal Pt counter electrode and enhanced the electrocatalytic ability of counter electrode. We not only measured the photovoltaic parameters but also used cyclic voltammetry (CV) and Tafel polarization measurements to verify the electrocatalytic activity. The structure of DSSC was shown in Fig.1.

Fig. 1. The structure of DSSC.

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12-15 November, 2017, Hanoi, Vietnam

P016 Enhanced-electrochemiluminescence of Ru(bpy)32+ with Mn:ZnSe Quantum Dots Suphawuth Siriketa, Sirirat Phaisansuthichol, and Sakchai Satienperakul a

Department of Chemistry, faculty of Science, Maejo University, 50290 Chiang Mai, Thailand Email : [email protected]

Electrochemiluminescence (ECL) of Ru(bpy)32+ with Mn-doped ZnSe quantum dots was synthesized, characterized and investigated. Mn:ZnSe QDs was synthesized in aqueous by capped with MPA at low temperature pyrolysis procedure. The properties of Mn:ZnSe QDs was characterized by UV-Vis/PL spectrophotometer, TEM and EDS. The maximum absorption and emission of Mn:ZnSe are 385 and 602 nm, respectively. The average size of quasi-spherical ddots are around 3.0 nm and the Mn:Zn ratio is 1:20 using EDS. This QDs will be applied to enhanced-electrochemiluminescence measurement for tetracycline.

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12-15 November, 2017, Hanoi, Vietnam

P017 Heterojunction of SnO2 nanowire mat and MWCT film for room temperature gas sensors Quan Thi Minh Nguyet1,2, Nguyen Van Duy1, Nguyen Duc Hoa1, Dang Thi Thanh Le1, Nguyen Van Hieu1* 1

International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, No 1, Dai Co Viet, Hanoi. 2 School of Engineering Physics, Hanoi University of Science and Technology, No 1, Dai Co Viet, Hanoi. *

Email: [email protected]

Room temperature gas sensors are advantage in practical applications because they do not require a heater. In this study, Schottky junction made of SnO2 nanowires and multiple walled carbon nanotubes (MWCNTs) thin film was prepared for room temperature NO2 gas sensor. The device was fabricated by first growing SnO2 nanowires on one Pt electrode using a thermal chemical vapour deposition method. Thereafter, the device was dipped in a solution of MWCNTs to form a thin film connecting between the two Pt electrodes. The current-voltage (I-V) characteristics and gas sensing properties of the SnO2/MWCNT device were investigated. Results demonstrate that the fabricated device has a good rectifying behavior in both air and NO2 gas. The SnO2/MWCNT Schottky device has ultrahigh enhancement in gas sensing performance for NO2 compared to the pristine SnO2 NWs or MWCNTs. The sensor response S (Rgas/Rair) to 1 ppm NO2 at room temperature is 450. Device’s parameters such as ideality factor, barrier height, and the series resistance are extracted from the dc I-V measurements to clarify the sensing mechanism.

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12-15 November, 2017, Hanoi, Vietnam

P018 Aptamer - conjugated multifunctional nanoparticles: A promising tool for fast detection and collection of cancer cells Chu Tien Dunga,b, Nguyen Thi Thuy Haa, Tran Thi Hongc, and Nguyen Hoang Nama,d a

Faculty of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi. Department of Physics, University of Transport and Communications, 3 Cau Giay, Hanoi. c VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi. d Vietnam Japan University, Vietnam National University, Luu Huu Phuoc, My Dinh 1, Nam Tu Liem, Hanoi b

Email: [email protected]

Multifunctional magnetic-plasmonic Fe3O4/Ag nanoparticles (MNPs) exhibit strong surface plasmon resonance, which is widely applicable for detection and diagnosis of cancer cells. Simultaneously, MNPs display a high saturation magnetization at room temperature, which are promising for collection and separation of targeted cells. Moreover, aptamers are a group of molecules, which can specifically detect, bind, and inhibit cancer cells. In this study, the aptamer – conjugated MNPs are fabricated by self-assembling of aptamers on the surface of MNPs via covalent Ag-S linker. The results of the Fourier transform infrared spectroscopy and the Raman scattering showed that aptarmer – conjugated MNPs are promising tool for fast detection and collection of cancer cells.

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The 12th Asian Conference on Chemical Sensors (ACCS2017)

12-15 November, 2017, Hanoi, Vietnam

P019 Effect of Ca2+ and V5+ substitution on the atomic structure, microstructure and oxidation state of YIG nanoparticles Vu Thi Hoai Huong, To Thanh Loan*, Dao Thi Thuy Nguyet, Nguyen Phuc Duong International Training Institute for Materials Science, Hanoi University of Science and Technology, No 1 - Dai Co Viet Str., Hanoi, Vietnam. *Email: [email protected]

In the present paper, we report a detailed study on the atomic structure, microstructure and oxidation state of Ca2+ and V5+ substituted yttrium iron garnet nanoparticles by using a combination of synchrotron X-ray diffraction and X-ray absorption spectroscopy. The Y32xCa2xFe5-xVxO12 nanoparticles (x = 0, 0.2, 0.4, 0.6, 0.8 and 1) were synthesized by using sol-gel method and followed by heat treatment at 900 C for 5 h. The single phase of garnet ferrite structure was observed in the samples. All the structure information in term of long-range order including lattice constant, atomic positions, ion occupancy, average coherent scattering region and lattice microstrain were determined from synchrotron X-ray powder diffraction data on applying the full pattern fitting of Rietveld refinement. Valence state of iron in the samples was obtained by analysis of X-ray absorption near edge spectrum at Fe K-edge. In addition, the distribution of Ca2+ and V5+ ions over lattice sites was determined, in which Ca2+ ions occupy in C site only while V5+ ions distribute in both A and D sites. The results were discussed and compared with the reported data.

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The 12th Asian Conference on Chemical Sensors (ACCS2017)

12-15 November, 2017, Hanoi, Vietnam

P020 Synthesis and Photocatalytic Activity of (N, Ta) Co-doped TiO2 Nanopowders Vu Duy Thinh 1, Ngo Thi Hong Le,2 1 Hanoi University of Mining and Geology 18 Pho Vien – Duc Thang, Tu Liem North, Hanoi, Vietnam 2 Institute of Materials Science, Vietnam Academy of Science and Technology 18 Hoang Quoc Viet Road, Hanoi, Vietnam *Corresponding author: [email protected] TiO2 has the most efficient photoactivity, the highest stability and the lowest cost, safety to humans and the environment. But TiO2 has high recombination rate of electron-hole and absorbs only the ultraviolet radiation, make up 4% of solar radiation due to this material has large band gap (3.2 eV). To improve the performance of TiO2 is to increase its optical activity, one found out method of TiO2 material structure changing with other doped elements to reduce the band gap and shift the absorption wavelength to visible light region. In this paper, nitrogen and tantalum co-doped TiO2 nanopowders were fabricated by hydrothermal method, followed by calcination at 300oC for 1 h. The results showed that the single phase of anatase TiO2 with particle size of about 20 nm was obtained in all samples. The effects of N and Ta co-doping on the average grain size and strain were also detected by micro-Raman spectroscopy. Comparing to the case of pure TiO2, nitrogen and tantalum co-doped nanopowders exhibited a higher visible light photocatalytic activity for degradation of methylene blue.

Figure 1. Photocatalytic degradation of MB of the TiO2, N doped TiO2, (N, Ta) co-doped TiO2 samples in 180 min.

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12-15 November, 2017, Hanoi, Vietnam

P021 Fabrication of SnO2 (n)–SnO (p) Core-Shell Nanowires on the Copper Foil by Thermal Evaporation Process Pham Tien Hung, Sang-Wook Lee, Joon-Hyung Lee, Jeong-Joo Kim, Young-Woo Heo* School of Materials Science and Engineering, Kyungpook National University, Daegu, 702-701, Korea E-mail: [email protected]

Abstract: In the past decades, various attemps have been made to improve further the electrical properties of multiple networked oxide nanowire. The application of hetorostructure has been to be beneficial for enhancing electrical properties of nanomaterial. Recently, the p-n heterostructures materials have been attracting a growing number of concerns because of their potential applications e.g. photoluminescence, electro-chromic devides, photocatalysts and gas sensors due to form p-n junction and increase the material defect sites at the interface. In this study, the n-p core-shell nanowires were synthesized by a two-step process, in which the core SnO2 nanowires were grown on the copper foil by thermal oxidation process and subsequently the SnO shell layers were deposited by the thermal evaporation. The morphologies and crystal structures of SnO2 nanowires and core-shell structure SnO2-SnO were characterized using x-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM) and selective area electron diffraction (SAED). In addition, the possible formation mechanism and growth mechanism of SnO2 nanowires and n-p core-shell SnO2-SnO nanowires were proposed and discussed. Keywords: SnO2-SnO, p-n junction, core-shell structure, nanowires, thermal evaporation.

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12-15 November, 2017, Hanoi, Vietnam

P022 An Electrical Assay for Protein Kinase A Based on Carbon Nanotube FieldEffect Transistor Chang-Seuk Lee, Su Hwan Yu, Sujeong Hong, Sujin Shim, Tae Hyun Kim* Department of Chemistry, Soonchunhyang University, Asan, 31538, Republic of Korea Email: [email protected]

The protein kinase a (PKA) plays a key role in the human biological system, especially involving in peptide phosphorylation and enzymatic signal amplification. The detection of PKA gives a lot of information about diverse disease, such as cancer, leukaemia, HIV, etc. PKA has traditionally been measured using radioactive isotope-labelled ATP. To overcome the radiological hazards, various new methods have been reported, including colorimetry, fluorescence spectroscopy, mass spectrometry, Raman spectroscopic assay, and surface plasmon resonance imaging technique. Although these methods greatly improved the determination of PKA, there are still limitations, such as the complicated sample pretreatments, expensive instruments, or low sensitivity. Recent advances in nano- and biotechnology have led to great progress in bio- and chemical sensing applications. These approaches are highly efficient and remarkably sensitive, with detection limits down to the picomolar range. In particular, field-effect transistors (FETs) based on single-walled carbon nanotubes (swCNTs) have attracted much attention because of numerous advantages such as, label-free, real-time detection, easy operate system, and mobility for the detection of bio- and chemical species. Here, we developed a nanoscale-based biosensor for the detection of PKA by modifying swCNT-FET with self-assembled monolayer of Ckemptide (CLRRASLG). Adenosine triphosphate (ATP) was used as the co-substrate. The detection limit of PKA was 0.0012 unit/mL.

Figure 1. A schematic of Kemptide-modified swCNT-FET for PKA activity assay.

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12-15 November, 2017, Hanoi, Vietnam

P023 Method Development and Validation for the Determination of Inorganic Arsenic using Differential Pulse Anodic Stripping Voltammetry (DPASV) Maritess L. Magalona, Milagros M. Peralta, Marivic S. Lacsamana, Veronica C. Sabularse, Constancio C. de Guzman, Stephanie Britania, Ma. Theresa Glenn Bea Manguiat Institute of Chemistry, University of the Philippines Los Baños, Laguna, Philippines, 4031 Email: [email protected]

The maximum contamination limit set by the U.S. Environmental Protection Agency for arsenic in drinking water is 10µg/L (10pbb) in view of the adverse effects of chronic arsenic exposure on human health. Hence, there is a need to develop an inexpensive method that can quantify arsenic at or below this concentration to ensure compliance with EPA regulations. An electroanalytical method was developed and validated to analyze trace inorganic arsenic as As(III) and total As using DPASV equipped with a gold disk as the working electrode, Pt/Ti rod as the auxiliary electrode, and Ag/AgCl as the reference electrode. The method was found to be precise and sensitive based on the resulting relative standard deviation values (< 12.7%) of the peak heights of standard arsenic solutions and the slopes of calibration. It also has a satisfactory percent recovery of 91% for As(III) and 81% for As(V). The limit of detection of As(III) and As(V) were 2.24 and 6.96µg/L, respectively while the limit of quantification of As(III) and As(V) were 7.49 and 23.19µg/L, respectively. The total arsenic content of groundwater samples obtained by this method was compared with inductively coupled plasma – optical emission spectrophotometry, and statistical analysis using the t-test showed that the two methods were not significantly different.

Figure 1. The equipment and the parameters used to develop the DPASV method

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12-15 November, 2017, Hanoi, Vietnam

P024 Measurement of saltiness concentration and intensity using saltiness sensor and ISE Y. Kaneda a, Y. Muto a, Y. Tahara b, H. Ikezaki c, H. Sano d and K. Toko a, b a

Graduate School of Information Science and Electrical Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan b Research and Development Center for Taste and Odor Sensing Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan c Intelligent Sensor Technology, Inc., 5-1-1 Onna, Atsugi-Shi, Kanagawa 243-0032, Japan d Fuji Foods Corp., 5-14, Haneda Asahicho Ota-ku, Tokyo 144-0042, Japan Email: [email protected]

Response (mV)

A taste sensor enables us to quantify basic taste qualities of foods. This sensor consists of a reference electrode and working electrodes which respond to each taste substances selectively using several lipid/polymer membranes [1]. The saltiness sensor, one of the working electrodes, works by electrostatic interaction between the membrane and anions because of its positively charged lipids. Namely, the sensor doesn’t respond to saltiness derived from Na+, different from the actual situation where human perceives as salty substances. Further, although it is reported that tartaric acid and citric acid enhance saltiness [2], the sensor doesn’t reflect this effect. The purpose of the present work is to measure saltiness intensity more strictly. Based on the above, we carried out two kinds of measurement. Firstly, we measured saltiness intensity derived from Na+ using the saltiness sensor and an ion-selective 10 electrode (ISE) which selectively responds to Na+. Secondly, we measured the salty taste enhancement 8 effect using a new modified ISE sensor. As a result, the saltiness sensor responded to Cl- of NaCl in 170 6 mM NaCl and 300 mM MSG solution. On the other hand, the ISE sensor responded to Na+ of both NaCl 4 and MSG. These results indicate that combined use of the saltiness sensor and the ISE sensor can measure saltiness concentration and intensity caused by Na+ not 2 containing Cl-. Moreover, the new modified ISE sensor was able to respond to 170 mM NaCl with tartaric acid 0 or citric acid higher than 170 mM NaCl alone, which 0 0,033 0,1 0,3 corresponds to the salty taste enhancement effect [Fig. Tartaric acid (mM) 1]. In conclusion, we measured saltiness concentration Fig.1 The measurement of the salty taste and intensity by combination of the saltiness sensor enhancement effect by tartaric acid. Tartaric acid was mixed in 170 mM NaCl. and the modified ISE sensor. [1] Y. Tahara and K. Toko, IEEE Sensors Journal, 13(8), 3001-3011, 2013 [2] K. Ishikawa, Y. Takahashi et al., Bull. Soc. Sea Water Sci., 67, 219-223, 2013 [in Japanese]

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12-15 November, 2017, Hanoi, Vietnam

P025 The Characteristic of ZnO:(Al,P) Thin Films with ZnO Buffer Layer by the RF-Magnetron Sputtering Seunghak Shin, Sangwook Lee, Joon-Hyung Lee, Young-Woo Heo, Jeong-Joo Kim* School of Materials Science and Engineering, Kyungpook National University, Daegu 41566, Republic of Korea Email: [email protected]

ZnO has received much attentions as a next generation transparent conduction oxides (TCOs) material due to its wide direct band gap (3.37eV) and large excition binding energy (60meV). ZnO is a Ⅱ-Ⅵ compound semiconductor and it has well known that pure ZnO exhibits mostly n-type conduction. So making a p-type conduction ZnO is difficult because of its native defects, which make electron, such as zinc interstitial (Zni), oxygen vacancies (Vo) and hydrogen impurities. Co-doping of both acceptor (such as N, P) and donor (such as Ga, Al) increased the solubility of acceptors in ZnO. Some reports have suggested that using a ZnO buffer layer could enhance TCOs properties by reducing the film roughness and improving crystallization. This research was focused on reducing native defect by using a ZnO buffer layer. The deposition temperatures and post-annealing effect of ZnO buffer layer were investigated. ZnO:(Al,P)/ZnO thin films were prepared by RF-magnetron sputtering. To observe the microstructure and electrical properties, we used FE-SEM, XRD, Hall measurement, AFM and etc. ZnO:(Al,P)/ZnO thin films can be deposited stably when the deposition and annealing temperature of ZnO buffer layer is higher than ZnO:(Al,P)’s deposition temperatures.

Figure 1. XRD φ-scans of (a) ZnO buffer layer (Tg,ZnO = RT–600°C) and (b) APZO on ZnO buffer layers (Tg,ZnO:Al,P = 600°C, Tg,ZnO = RT–600°C) grown at various temperatures on c-plane sapphire substrates.

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12-15 November, 2017, Hanoi, Vietnam

P026 Organic FET Based BioFETs towards Stress Monitoring Shin-ichi Wakidaa,b, Tsuyoshi Minamic,d, Tsukuru Minamikic, Yui Sasakid, Ryoji Kuritab,d, Osamu Niwae,d and Shizuo Tokitod a

AIST-Osaka University Advanced Photonics and Biosensing Open Innovation Laboratory, National Institute of Advanced Industrial Science and Technology (AIST), Photonics Center, Osaka University, Suita, Osaka 565-0871, Japan; b Biomedical Research Institute, AIST, Tsukuba, Ibaraki 305-8566, Japan; c The University of Tokyo, Komaba, Tokyo 153-8505, Japan; d Yamagata University, Yonezawa, Yamagata 992-8510, Japan; e Saitama Institute of Technology, Fukaya, Saitama 369-0293, Japan Email: [email protected]

We have several kinds of BioFETs based on silicon, conventional MOSFET and organic transistors. Especially, organic FET (OFET) based biosensors can be one of the most promising candidates for mobile healthcare fields, because of their mechanical flexibility and bendability. We have designed an almost the same extended-gate type OFET based biosensors as conventional MOSFET based Coated Lead-wire FET, which have superior stable responses in solution. In the designed OFET device as shown in Fig. 1, the main OFET part is completely separated from the sensing site to prevent degradation of organic transistor by water and also the device can be operated at a low voltage because of the advanced gate design. We have carried out several R&D on BioFETs have been much attention for salivary stress marker candidates. Here, we will report some challenges for salivary stress BioFETs using the OFET platform for nitrate, human glycoprotein (CgA) and secretory IgA in saliva. We observed a reproducible negative shift of the OFET transfer characteristics with increase of the stress marker concentration. The other experimental results on several BioFETs will be shown in the presentation.

Figure 1. Extended-gate configuration compared with conventional OFETs (left) and (a) Photograph of the fabricated BioOFETs (upper: receptor immobilized Au electrodes; below: OFET). (b) Schematic illustration of OFETs part and materials (right).

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P027 Preparation and Characterization of Electrospun Poly(vinyl Alcohol)/Salicylic Acid-Modified Chitosan Microfibers as a Modifier for Carbon Paste Electrode in the Detection of Arsenic by Stripping Voltammetry Maris Asuncion L. Bayhona, Milagros M. Peralta, Marivic S. Lacsamana, Jose Rene L. Micor Institute of Chemistry, University of the Philippines Los Baños, College Laguna, Philippines. Email: [email protected]

a

Salicylic acid-modified chitosan (SAMC)/polyvinyl alcohol (PVA) electrospun microfibers with an average width of 1.726µm were used to modify the carbon paste electrode (CPE) for the detection of arsenic. The CPE was prepared using 10% PVA/SAMC modifier mixed with the activated carbon. The arsenic analysis was done using differential pulse anodic stripping voltammetry with the following optimized parameters: supporting electrolyte = 0.5M acetate buffer at pH 4.5; accumulation time = 400s; deposition potential = -500mV; and deposition time = 180s. Using two-way ANOVA analysis, it was concluded that PVA/SAMC microfiber - modified carbon paste electrode was significantly different from the unmodified carbon paste electrode. The analytical performance of the modified CPEs are satisfactory and reproducible with relative standard deviation (RSD) of 3.1233% for As(III) and 4.1550% for As(V), which is lower than 20%, the acceptable upper limit for trace analysis. The limits of detection (LOD) were found to be 45.47 ppb for As(III) and 45.28 ppb for As(V). Thus, PVA/SAMC microfibers CPE can be used as cheap and alternative working electrode for detecting arsenic concentrations greater than 50 ppb in water.

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P028 Electrochemical detection of Sudan I using nickel nanoparticles decorated graphene oxide modified screen printed carbon electrode Nguyen Truong Anha, Luong Thi Thuy Dunga, Nguyen Xuan Hoana, Nguyen Xuan Vieta Faculty of Chemistry, VNU University of Science, addr: 19 Le Thanh Tong, Hanoi, Vietnam. Email: [email protected]

A simple and sensitive electrochemical sensor was developed to determine Sudan I, illegal food colorants in food samples based on nickel nanoparticles decorated graphene oxide modified screen printed carbon electrode (Ni/GO/SPCE). Cyclic voltammetry and linear sweep voltammetry were used to investigate the electrochemical behaviour of Sudan I. It is found that the Ni/GO/SPCE can catalyze the reduction of azo group, -N=N- followed by electrochemical oxidation of OH- group present in Sudan dye molecule. The components showed good synergic interaction in sensing Sudan I, thus the modified electrode presented higher sensitivity. Quantitative detection of Sudan I present in food products was carried out by amperometry technique in which reduction potential was fixed at 0,55V vs AgCl/Ag. The amperometry techniqe showed an excellent performance with a sensitivity of 9,13 A.M-1cm-2 and a detection limit of 171.8 nM. A wide dynamic range graph was constructed in the ranging 0,33 M to 35 M (see figure 1). The modified electrode had good stability and repeatability. It was applied to the detection of Sudan I in food products such as red chili powder and ketchup samples, and the recovery was acceptable.

Figure 1. The photograph of SPCE and the amperometric responses of Sudan I with successive addition of Sudan I into 0.1 M KOH under potential of 0.55 V vs AgCl/Ag

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12-15 November, 2017, Hanoi, Vietnam

P029 H2S Gas Sensor Based on Ru-MoO3 Thick Film Ungkana Inpana, Viruntachar Kruefua,b, Anurat Wisitsoraatc, Sukon Phanichphantd a

Nanoscience and Nanotechnology Program, Faculty of Science, Maejo University, Chiang Mai 50290, Thailand b Program in Applied Physics, Faculty of Science, Maejo University, Chiang Mai 50290, Thailand c National Electronics and Computer Technology Center, National Science and Technology Development Agency, Pathumthani 12120, ThailandcMaterials d Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand Email: [email protected]

Sensing characteristics of the spin-coated ruthenium loaded molybdenum trioxide (Ru-MoO3) nanof l a k e thick films with 0.5 wt%Ru concentrations have been studied for H2S gas. The influence on a dynamic range of Ru concentration on H2S response of thick film sensor elements was studied at the operating temperatures ranging from 250 to 350C. It was found that 0.5 wt%Ru-MoO3 thick film has been improved by increasing the surface area with the response to the H2S gas (10 ppm) at 3.61 rising from 1 .32 of pure MoO3 thick film. Plausible mechanisms explaining the enhanced H2S response by thick films of Ru-MoO3 are discussed.

Figure 1. SEM cross-section image of Ru-MoO3 nanoflake sensing film.

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P030 Sensing for cardiac differentiation of model stem cells with a surface plasmon resonance (SPR) imager Shiori Kawashima, Hiroaki Shinohara, Yuki Shiraishi, Minoru Suga Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku Toyama 930-8555,Japan. [email protected]

Tissue regeneration using iPS cells requires to evaluate whether the stem cells have differentiated as planned. However, conventional methods are complicated, invasive, and timeconsuming. In the current study, we have developed a new method for non-invasively evaluation of cardiac differentiation with a high resolution of surface plasmon resonance (SPR) imager. Here P19CL6 cell, a mouse embryonal carcinoma cell line was used and differentiated into cardiac cell by DMSO treatment . We expected that the SPR imager could distinguish cardiac differentiated cells from undifferentiated cells by observing the cell response in the SPR imaging upon muscarine stimulation. Figure 1 shows the time-course of reflection intensity changes at P19CL6 cell regions upon muscarine stimulation after 16 days from DMSO treatment. After the muscarine injection, gradual decrease of reflection intensity about 40% was observed at many cell regions. On the other hand, slight change was observed at a little cell regions. We considered that cells showed large reflection intensity change might be differentiated into cardiac cells. The differentiation rate by SPR response was almost consistent with the differentiation rate by immunohistochemistry with anti-cardiac troponin T (cTnT) antibody. These results supported SPR imaging upon muscarine stimulation was useful for sensing of cardiac differentiated cells.

Figure 1. Reflection intensity changes at P19CL6 cell regions upon muscarine stimulation. The cells were treated with 1.0% DMSO for 16 days.

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12-15 November, 2017, Hanoi, Vietnam

P031 Hydrothermal synthesis of nanostructured MoS2 and its electrochemical properties Truong Cong Dinh1,2, Vy Anh Vuong1, Chu Manh Hung1, Nguyen Duc Hoa1* 1

International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, Hanoi, Vietnam 2-Department of Advanced Materials Science and Nanotechnology, University of Science and Technology of Hanoi- USTH, Hanoi, Vietnam Email: [email protected]

Two-dimensional (2D) materials have become the topic of interest in materials science and engineering, due to their unique properties and great potential application in various fields. Among others, transition metal dichalcogenides (TMDCs), which have unusual electrical, optical and electrochemical properties, have been attracted the most concern. In more specific, TMDCs have widely and almost infinite potential in various fields, including electronic, optoelectronic, sensing, and energy storage applications. Thus, there are many methods used to prepare TMDCs, such as chemical vapor deposition method (CVD), mechanical exfoliation, liquid exfoliation, and hydrothermal method. Of those used techniques, hydrothermal pathway appears to be the most effective method for inexpensive and scalable synthesis of TMDCs with ability to turn their characteristics. The aim of this study is first to successfully synthesis TMDCs by hydrothermal method in different conditions to control their characteristics for electrochemical applications. The obtained materials were characterized by some advanced techniques such as scanning electron microscope (SEM), and X-ray diffraction (XRD). Electrochemical characteristics of materials were also studied to examine their potential application.

Figure 1. (A) SEM image, and (B) XRD of synthesized MoS2

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12-15 November, 2017, Hanoi, Vietnam

P032 Flexible Piezopolymer Pressure Sensor for Structural Health Monitoring Toan Thanh Dao Faculty of Electrical-Electronic Engineering, University of Transport and Communications (UTC), No. 3, Cau Giay Street, Dong Da, Hanoi, Vietnam E-mail: [email protected]

A pressure sensor is a critical component in a structural health monitoring (SHM). Currently commercial pressure sensor with a relatively small size in a range from mm2 to several cm2 can help to sense data at a narrow area only. In civil engineering or construction building, sensing area is usually much larger, thus, many sensors are required in order to collect the structure health at high resolution. In terms of electronic engineering, that results in the signal processing system and computer program are complicated, leading to high-cost product, establishment and maintain. In recent year, a pressure sensor based on organic/polymer material has received much attention and proposed for SHM thanks to its unique advantages of low-cost and large-size ability. Here, author would like to demonstrate a beam bending monitoring system based on large-area pressure sensor, which are made and tested with a laminated bamboo beam at our University. The pressure sensor with a size of 0.10.1 m2 was carefully fabricated using piezopolymer material and printing technique (Fig. 1a). Fig. 1b shows the illustration of the system including readout circuit and computer software written by C#. A load diagram and a photo of the system under test taken are shown in Figs. 1c and 1d, respectively. As can be seen, the system can dynamically detect the bending process of the Figure 1. Large-area pressure sensor based- system for monitoring construction beam. Significantly, laminated bamboo beam bending by loading. even the beam is broken down, the sensor still maintains its shape and property and can be reused. The sensor manufacturing, system development and testing procedure will be discussed in detail at conference time.

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P033 Development of Multichannel Highly Sensitive Interdigitated Capacitor Based Glucose Biosensor Md. Rajibur Rahaman Khan, Sae-Wan Kim, Shin-Won Kang* School of Electronics Engineering, Kyungpook National University, 80 Daehakro, Bukgu, Daegu 41566, South Korea. Email: [email protected]

In this study, we proposed a multichannel interdigitated capacitor (IDC) biosensor to detect glucose 1 µM to 1 M. The operation principle of the sensor is based on the capacitance variation. Four different types of solvatochromic dyes such as: Nile red, Reichardt’s dye, Auramine-O, and Rhodamine-B, were individually mixed with the polyvinylchloride and N,N-dimethylacetamide, to create four different types of sensing solutions, which were then used in the interdigitated electrodes to create IDC glucose biosensors. The IDC capacitance changes due to changes in the concentration of glucose solutions, consequently, the received sensing signal’s amplitude changes as well. The sensitivity of the proposed glucose biosensor was about 29.4 mV/decade with fast response and recovery times of about 6 s and 5 s, respectively. The proposed biosensor offers a stable sensing responses, linear sensing performance with the correlation coefficient R2 ≈ 0.9849 over the wide dynamic range, excellent reproducibility with a relative standard deviation of about 0.029. Finally, the performance of the proposed IDC glucose biosensor was compared with other glucose sensors such as: a potentiometric, IDC, FET, and fiber-optic with respect to response time, dynamic range width, sensitivity, and linearity. We found that the designed IDC glucose sensor offered excellent performance.

Figure 1. (a) Schematic diagram of the IDC glucose biosensor and (b) sensing response of the proposed IDC glucose biosensor.

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Acknowledgements This study was supported by the BK21 Plus project funded by the Ministry of Education, Korea (21A20131600011) and Samsung Electronics. References [1] Md. R. R. Khan, and S. W. Kang, “Highly sensitive multi-channel IDC sensor array for low concentration taste detection”, Sensors, Vol. 15, pp. 13201–13221, 2015. [2] Md. R. R. Khan, and S. W. Kang, “Highly sensitive temperature sensors based on fiber-optic PWM and capacitance variation using thermochromic sensing membrane,” Sensors, Vol. 16, No.7, 1064, 2016.

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P034 Analysis of Counter Electrode Modified by Reduced Graphene Oxide and Black Phosphorus with IGZO/TiO2 Photoelectrode for Dye-sensitized Solar Cell Chang-Yi Wua, Jung-Chuan Choua, b,*, Yi-Hung Liaoc, Chih-Hsien Laia,b, Chang-Chia Lua and Pei-Hong Youb a

Department of Electronic Engineering, National Yunlin University of Science and Technology, Yuniln, Taiwan, Taiwan. Addr: No. 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan, R.O.C. b

Graduate School of Electronic Engineering, National Yunlin University of Science and Technology, Yunlin, Taiwan. Addr: No. 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan, R.O.C.

c

Department of Information and Electronic Commerce Management, TransWorld University, Yunlin, Taiwan. Addr: No.1221, Zhennan Rd., Douliu City, Yunlin County 640, Taiwan R.O.C. *

Email: [email protected]

Abstract In this study, titanium dioxide (TiO2) colloid was deposited on the fluorine doped tin oxide (FTO) substrate by spin coating and blade coating. Indium gallium zinc oxide (IGZO) was sputtered on the TiO2 film to form IGZO/TiO2 phototelectrode. Graphene was excellent carbon material, which had outstanding electrochemical catalysis, large specific surface area and high mobility. Black phosphorus was impressive two dimensional material, which had high electrical conductivity and direct energy gap. Pt counter electrode was modified by reduced graphene oxide (rGO) and black phosphorus (BP), which was fabricated with rGO/BP colloid by spin coating on the Pt film. IGZO/TiO2 photoelectrode exhibited high absorption and lower reverse recombination. Moreover, rGO/BP counter electrode demonstrated good catalytic activity and charge transport. The photovoltaic conversion efficiency of the IGZO/TiO2 photoelectrode and rGO/BP counter electrode dye sensitized solar cell (DSSC) was increased, which was comparable to TiO2 photoelectrode and Pt counter electrode DSSC.

Fig. 1. The structure of DSSC in this study.

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P035 Investigation of the Temperature Effect for the Chlorine Ion Sensor Tong-Yu Wua,*, Shi-Chang Tsenga, Jung-Chuan Choub,c, Yi-Hung Liaod, Chih-Hsien Laib,c, Siao-Jie Yanc, You-Xiang Wuc, Cian-Yi Wuc and Ting-Wei Tsengb a

Graduate School of Mechanical Engineering, National Yunlin University of Science and Technology, Yunlin, Taiwan. b Department of Electronic Engineering, National Yunlin University of Science and Technology, Yunlin, Taiwan. c Graduate School of Electronic Engineering, National Yunlin University of Science and Technology, Yunlin, Taiwan. d Department of Information and Electronic Commerce Management, TransWorld University, Yunlin, Taiwan. Email: [email protected]

Abstract In this study, the different temperatures of the solutions were investigated at different solution temperatures for the chlorine ion sensor. The temperature coefficient is an important parameter for ion sensing devices. The screen printing system and radio frequency (R. F.) sputtering system were used to prepare the arrayed flexible ruthenium dioxide (RuO2) hydrogen (H+) ion sensor. The weight ratio of the poly (vinyl chloride) (PVC), bis (2-ethylhexyl) sebacate (DOS), chloride ionophore III (ETH9033) and tridodecylmethy-lammonium chloride (TDDMACl) was 33: 66: 2: 10 (wt%), and which was used to prepare the arrayed flexible chlorine ion sensor. The arrayed flexible chlorine ion sensor was dried at room temperature 25oC. We used the voltage-time measuring system, electrochemical impedance spectroscopy (EIS) and temperature controller system to investigate the temperature effects of the arrayed flexible chlorine ion sensor. The temperature controller was used to control the solution temperature, which was from 5±0.2 oC to 50± 0.2 oC. The sensitivities of arrayed flexible chlorine ion sensors were increased by the thermal convection from 5 oC to 35 oC. When the temperature was more than 35 oC, the sensitivity was decreased. The characteristic was caused because the chlorine ion sensing film could not catch more chlorine ions with the increasing temperatures.

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12-15 November, 2017, Hanoi, Vietnam

P036 Exhalation analysis of diabetic patients using e-nose system Joon-Boo Yua, Byoung Kuk Jangb, Chong-Yun Kangc, Hae-Ryong Leed, Hyung-Gi Byuna a Division

of Electronics, Information & Communication Engineering, Kangwon National University, 346, Jungang-ro, Samcheok-si, Gangwon-do, Korea b Department of Internal Medicine, Keimyung University Dongsan Medical Center, Daegu, Korea c Center for Electronic Materials, KIST, Seoul, Korea d Division of electronic & Information Communication Engineering, ETRI, Korea Email: [email protected]

The analysis of exhale breath provides information on various biochemical processes and status in the human body. Volatile organic compounds(VOCs) from the exhalation can be a potential biomarker due to physiological and pathological symptoms and will allow early screening or monitoring of several diseases. An acetone is one of the large quantities of VOCs from the exhalation, and it comes from the breath of diabetics. In this study, we implemented an e-nose system using metal oxide sensors to analyze the expiration of diabetic patients. Metal oxide sensors were made using indium and tungsten, and were provided by KIST. To the collection and concentration of exhalation, a teddler bag and SPME fiber were used. Exhalation samples were collected from 25 patients and control subjects, respectively. The PCA results of the samples after excluding the error data in the measurement process are generally well distinguished between the patient group and the control group.

Figure 1. The result of PCA to control and diabetics group (circle: control, square: patients) Acknowledgements This work was supported by Institute for Information & communications Technology Promotion(IITP) grant funded by the Korea government(MSIP) (No.2015-0-00318, Olfactory Bio Data based Emotion Enhancement Interactive Content Technology Development)

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P037 Development of Polyaniline-Coated Cotton Yarn for Wearable Ammonia Gas Sensor Naraporn Indarita, Nattasamon Petchsangb and Rawat Jaisuttia,* a

Department of Physics, Faculty of Science and Technology, Thammasat University, Khlong Nueng, Khlong Laung, Pathumthani 12121, Thailand. b Department of Materials Science, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand * Email: [email protected]

Wearable ammonia gas sensors have been fabricated by dip coating of single cotton yarn in polyaniline precursors. The structure and surface morphology of polyaniline-coated cotton yarn are characterized by fourier transformed infrared spectroscopy with attenuated total reflection (ATR-FTIR) and scanning electron microscope (SEM). The observation of AIT-FTIR spectra showed that strong interaction between cotton yarn and polyaniline molecules. The SEM images confirm the adsorption of polyaniline onto cotton surface. In addition, the resistance of polyaniline-coated cotton yarn has been measured using Keithley 2400 source meter, and was found to be 18 kΩ/cm. Furthermore, the as-prepared polyaniline-coated cotton yarn was utilized as sensing material for gas sensor operated at room temperature. The results exhibited good response and high selectivity toward ammonia gas. As a proof-of-concept demonstration for wearable gas sensor, the sensing device-based cotton yarn was sewed on the fabric and exhibited fast change upon exposed to ammonia gas.

35

Ammonia gas

30

50 ppm

25

(Rg-R0)/R0

75 ppm

25 ppm

20 15 10 5 0

0

5

10

15

20

25

30

35

Time (min)

Figure 1. Sensor responses of polyaniline-coated cotton yarn exposed to ammonia gas at various concentration ranging from 25 ppm to 75 ppm. 195

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P038 Template-free Synthesis and Gas Sensing Property of Indium-doped Zinc Oxide Nanoflowers Siriprapa Khemthong, Kithipong Thana and Rawat Jaisutti* Department of Physics, Faculty of Science and Technology, Thammasat University, Khlong Nueng, Khlong Laung, Pathumthani 12121, Thailand. * Email: [email protected]

Indium-doped zinc oxide nanoflowers (IZO NFs) have been prepared by a facile hydrothermal process. The morphological, microstructure and optical properties of nanoflowers were investigated by scanning electron microscope (SEM), x-ray powder diffraction and UV-VIS spectroscopy, respectively. The observation of SEM images showed that a high density of indium oxide nanoparticles grew on ZnO nanosheet-assembled hierarchically flower-like architecture. The diameter of indium oxide nanoparticles was about 45 nm and the thickness of ZnO nanosheet was about 60 nm. The morphologies of IZO hierarchical NFs could be tailored by changing the amounts of indium precursor. In addition, gas sensors based on the hierarchical IZO NFs were fabricated and exhibited good response to ethanol at room temperature and under ultraviolet light illumination.

UV-LED

500 nm

IZO NFs

ITO

ITO

2µm

Glass-substrate (a)

(b)

Figure 1. (a) Schematic illustration of IZO NFs gas sensor operated under UV illumination and (b) SEM images of hierarchically IZO NFs.

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12-15 November, 2017, Hanoi, Vietnam

P039 Chemical Sensor based on Indium-Gallium-Zinc Oxide/Cobalt Phthalocyanine Heterojunctions Kittiphong Thanaa, Yong-Hoon Kimb,c and Rawat Jaisuttia a

Department of Physics, Faculty of Science and Technology, Thammasat University, Pathumthani, Thailand. b School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Korea. c SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon, Korea. Email: [email protected]

Heterostructured p-n junction gas sensors consisting of cobalt phthalocyanine (CoPc) and amorphous indium-gallium-zinc-oxide (a-IGZO) thin film have been investigated as a novel sensing element for chemical sensor applications. The CoPc thin film was prepared by thermal evaporation and coated on the top of solution-based process a-IGZO thin film. For this sensing architecture, the CoPc thin film acts as gas sensitive layer while a-IGZO film serves as a high mobility channel layer. Atomic force microscope, scanning electron microscope and x-ray diffraction were employed to confirm the formation of CoPc/a-IGZO heterojunctions. The gassensing measurement was examined at room temperature for various nitrogen dioxide (NO2) gas concentrations. The sensing results showed the good response and high selectivity toward NO2.

Au/Ni

CoPc

Au/Ni

a - IGZO

Substrate

Figure 1. Schematic illustration of CoPc/a-IGZO heterostructured gas sensor.

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P040 Study on the change of properties and morphology of polyoxymethylene/nanosilica composites according to accelerated weather testing Tran Thi Mai 1, 2, Nguyen Thuy Chinh1, Vu Viet Thang1, Nguyen Thi Thu Trang1, Dang Thi Thanh Le2, Thai Hoang1,* 1

Institute for Tropical Technology, VAST, No. 18, Hoang Quoc Viet Str., Cau Giay dist., Ha Noi 2 International Training Institute for Materials Science, HUST, No. 1, Dai Co Viet Str., Ha Noi Email: [email protected]

This paper presents the change of properties and morphology of nanocomposites based on polyoxymethylene (POM) and nanosilica (NS) according accelerated weather testing (ASTM D 4329-99 for 168 hours – 14 cycles). The FTIR spectra of POM, NS and POM/NS composites after testing show the appearance of characteristic peaks of POM and NS in the composites. Carbonyl index (CI) of POM after testing is increased from 0.96 to 1.43 corresponding to increasing of C=O group in polymer matrix. The CI of the nanocomposites has tend to drop due to NS particles inhibited the decomposition of POM. The tensile strength and elongation at break of POM/NS nanocomposites are reduced significantly while their Young modulus is decreased slightly in comparison with their tensile properties of the nanocomposites before testing. The tensiles strength, elongation at break and Young modulus of the nanocomposites POM/NS (using NS 0 - 1.5 wt.%) are larger than those of POM after testing in the same testing condition. The dielectric properties (dielectric constant, dielectric loss tangent and volume resistivity) of the nanocomposites are reduced according to testing time. Scanning Electrion Microscopy images on the surface of the nanocomposites indicate the number of cracks and size of cracks of the samples are rose and the cracks become bigger and deeper with increasing NS more than 1.5 wt.%.

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P041 Alizarin Red S-Modified Film-Coated Electrodes for Biosensing Daichi Minaki, Jun-ichi Anzai Graduate School of Pharmaceutical Sciences, Tohoku University 6-3 Aoba, Aramaki, Aoba-ku, Sendai 980-8589, Japan Email: [email protected]

Variety of coating materials have been used in combination with redox-active compounds to fabricate electrochemical biosensors. In this study, alizarin red S (ARS) was confined in layerby-layer (LbL) films composed of modified and unmodified poly(ethyleneimine) (PEI) and carboxymethylcellulose (CMC) to study the redox properties. A gold (Au) disc electrode coated with PEI/CMC LbL film was immersed in an ARS solution to uptake ARS into the film. ARS was successfully confined in the LbL film. The cyclic voltammogram (CV) of ARS-confined PEI/CMC film-coated electrodes thus prepared exhibited redox waves in the potential range from −0.5 to −0.7 V originating from 9,10-anthraquinone moiety in ARS, demonstrating that ARS preserves its redox activity in the LbL film. An additional oxidation peak appeared around −0.4 V in the CV recorded in the solution containing phenylboronic acid (PBA), due to the formation of a boronate ester of ARS (ARS-PBA) in the film. The oxidation peak current at −0.4 V decreased upon addition of sugars and catechol compounds to the solution. Thus, the results suggest a potential use of the ARS-confined PEI/CMC films for constructing voltammetric sensors for these compounds.

Figiure 1. Typical CV (A) and DPV (b) for ARS-confined PEI/CMC film-coated Au electrode in the absence (a) and presence (b) of 1 mM PBA in 10 mM HEPES buffer at pH 7.5.

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P042 VOC Gas Sensor Fabrication and Characteristics Based on Au doped ZnO Thin Film by Ion Beam Sputter Sang-Do Han*, Hana Cho, Min-Ho Kang, Dong-Yun Lee, Kie-Won Lee* Shinwoo Electronics Co. Ltd., 641, Pureundeulpan-ro, Paltan-myeon, Hwaseong-si, Gyeonggi-do, Republic of Korea * Email: [email protected]

Semiconductor type VOCs (volatile organic compounds) gas sensor based on Au doped ZnO thin film was prepared on alumina substrate by using ion beam sputter deposition and heat treatment of the film. Heater and electrode of the sensor were designed together on the alumina substrate (about 0.25 mm thick) to enhance thermal efficiency, and was fabricated by a simple screen-printing method with Pt paste. The clearance of the electrode to electrode is 85μm and width of the electrode was 100μm. The ZnO sputter target was prepared by cold pressing of zinc oxide powder. The ZnO sensing layer and Au catalyst were continuously deposited on the substrates at Ar/N2 gas ambient of 1.5x10-4 torr and then the deposited films were heat-treated in the range of 800℃ for 1hr in air atmosphere to obtain a reduction and stability of resistance. The sensing layer was examined by scanning electron microscopy and energy dispersive spectrometer. The fabricated sensors were tested against 2-methy1-1-propanol (C4H10O) and acetaldehyde (C2H4O) which are a kinds of the VOCs (volatile organic compounds). The sensitivity, selectivity, linearity and reproducibility of the sensor showed good level. These gases as low as 10ppm can be detected by the present fabricated sensors.

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P043 UV-light-activated TiO2 thin film for H2S sensing at room temperature Nguyen Duc Chinh, Chunjoong Kim, and Dojin Kim Department of Materials Science and Engineering, Chungnam National University (CNU), 99 Daehang-ro, Yuseong-gu, Daejeon 34134, Republic of Korea

UV- light activated TiO2 thin film for H2S sensing at room temperature is reported. TiO2 thin films are fabricated by bar coating of a mixture of TiO2 powder and acetic acid. The morphology and structural properties were examined by scanning electron microscopy, X-ray diffraction, photoluminescence spectroscopy, absorption spectroscopy, and X-ray photoelectron spectroscopy. The UV irradiation significantly enhanced the H2S response signals and response/recovery kinetics. The sensor also showed high selectivity for H2S. The effects of UV light intensities and humidity on the sensing performance was also investigated. The results exhibited simple way of detecting parts per million concentrations of H2S at room temperature. The possible mechanism of photoconduction sensing for detecting H2S is also discussed.

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P044 Electronic nose based on temperature modulated response of bi-layer Pt/SnO2 thin film multi-sensor array toward environmental monitoring Nguyen Xuan Thaia,b, Nguyen Van Duya*, Nguyen Duc Hoaa, Nguyen Van Hieua a

International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, Hanoi, Vietnam b Volume and flow Laboratory, Vietnam Metrology Institute (VMI), Hanoi, Vietnam Email: [email protected]

Electronic nose applications in environmental monitoring are nowadays of great interest, because of the instrument’s proven capability of recognizing and discriminating between a variety of different gases and odors using just a small number of sensors. The aim of this work is to design and development of an electronic nose system based on multi gas sensor array of bi-layer platinum/tin oxide toward environmental monitoring. A novel structure for integrating individual sensors into a gas sensor array was developed in this work. The sensor array was composed of 4 sensors using the same micro-heater. Four sensing elements of the array sensor are fabricated by reactive DC sputtering method. The sensor array was exposed to ethanol, acetone, H2S, H2 and NH3 in part per million (ppm) concentrations level. The results showed that the prototype electronic nose is able to measure the level of relevance gases in polluted air and make a database for categorizing gases.

(A)

(A)

(B)

(B)

Fig 1. Prototype of electronic nose: (A) Hardware data acquisition system; (B) Self-made software data acquisition based on Labview programming

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P045 Development of a Sensitivity-Enhanced Surface Plasmon Resonance Aptasensor for the Detection of Arsenic L.T. Fana, C.H. Yangb, C.C. Changa, T.L. Chuanga , J.S. Laic, W.S. Linc, C.W. Lina a

b

Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan c Hydrotech Research Institute, National Taiwan University, Taipei, Taiwan Email: [email protected]

Arsenic has been contaminating water and soil worldwide due to mineral distribution and industrial pollution. The current detecting technologies are mostly lab-based with complex and delicate equipment, though with extremely low limit of detection (LOD), they are impractical for on-site screening and real-time monitoring. Thus, a rapid screening method is in demand with high sensitivity and a LOD low enough for inspections of agricultural water, reservoir water and wastewater from industrial discharge. The introduction of Systematic Evolution of Ligands by Exponential Enrichment (SELEX) made it possible to develop DNA aptamers affinitive to assigned targets including arsenic. Based on the arsenic-affinitive aptamer developed by M. Kim’s research team, we were able to develop a surface plasmon resonance aptasensor for the detection of arsenic. However, during our research we discovered that the secondary structure of the DNA aptamer inhabited its own sensitivity to the target when being immobilized on the gold nano-film, so we developed a solution to bind a complementary DNA segment to the aptamer on its non-functional site to erect its secondary structure, allowing better exposure to analytes. It was proved effective with enhanced sensitivity by lowered LOD from 10 ppb to 1 ppb, the slope of reaction kinetic line became two times higher. This method was also tested with field sample, resulting in good reproducibility.

(A)

(B)

Figure 1. (A) The schematic drawing of a bare DNA aptamer and a modified DNA aptamer. (B) The calibration curves of the arsenic sensor with bare aptamers and modified aptamers as probes. 203

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P046 Electrochemical Gas Sensor Employing Quasi Solid-State Polymer Electrolyte with High Conductivity Sang-Hyung Kima, Seung Hark Parka, Dong-Yun Lee, Sang-Do Hanb, Jin-Seong Parkc, Dong-Won Kima* a

Department of Chemical Engineering, Hanyang University, Seoul 04763, Korea b ShinWoo Electronics Co.Ltd, Hwa Seoung 445-915, Korea c Deartment of Materials Engineering, Chosun University, Kwangju 501-759, Korea Email: [email protected], [email protected]*

Electrochemical gas sensors are gas detectors that measure the concentration of a target gas by oxidizing or reducing the gas at an electrode and measuring the resulting current. They have fast response, excellent sensitivity and gas selectivity, and thus are suitable for sensing a toxic gas. These sensors usually consist of two or three electrodes in contact with an electrolyte solution. The working electrode contacts both the electrolyte and the ambient air to be monitored via a porous membrane. The electrolyte commonly used in the electrochemical gas sensors are an acid-based and alkaline-based electrolytes. Since these liquid electrolytes are directly contacted with air, their characteristics can be affected by the external environment such as humidity and temperature. Moreover, the reliability and long-term stability of electrochemical gas sensor employing liquid electrolyte is not good due to the leakage problem of liquid electrolyte. In this study, we prepared highly conductive quasi solid-state polymer electrolytes by combining different types of polymer materials and liquid electrolytes (H2SO4 and KOH), and their electrochemical properties were investigated for application in electrochemical gas sensor with enhanced durability. The quasi solid-state polymer electrolytes was applied to electrochemical gas sensors, and their performance was evaluated.

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P047 A Novel Monolithic Phase sensitive Surface Plasmon Resonace Biosensor Tzu-Heng Wu1，Zu-Yi Wang2, Julien Vaillant3, Hui-Yun Luo 2, Aurelien Bryant3* and Chii-Wann Lin1,2 a

Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Addr: No. 49, Fanglan Rd., Da'an Dist., Taipei, Taiwan b Institute of Biomedical Engineering, National Taiwan University, Addr: No. 49, Fanglan Rd., Da'an Dist., Taipei, Taiwan c Laboratoire de Nanotechnologie, Optique et Instrumentation, Universite de Technologie de Troyes, Addr: 12 Rue Marie Curie, 10430 Rosières-prés-Troyes,France Email: [email protected] , [email protected]

In this work we propose novel phase sensitive SPR system based on a homodyne monolithic sensor chip design. A low wavelength tenability source is applied together with a novel phase extraction method [1-2]. Fig.1 (a) demonstrate the results of the phase sensitive chip. We observed a clear interference pattern in overlapping zone of signal beam and reference beam is demonstrated. At Kretschmann angle, we observe a clear decay of signal beam intensity. To extract the phase information from such a homodyne signal, we proposed new phase extraction method. Fig.1 (b) demonstrates the interference signal of our system. The key of this algorithm is that with a phase modulation depth (∆𝜙𝑎 ) of 3.8317, we can simplify our math process and be able to calculate the phase and amplitude signal of our sample. The expression of phase extraction is

𝜙𝑆𝑃𝑅 =

[1+𝐽0 (2∆𝜙𝑎 )−2𝐽02 (∆𝜙𝑎 )]𝑅𝑦 −𝜇𝐽1 (2∆𝜙𝑎 )𝑅𝑋 (1−2𝐽0 (∆𝜙𝑎 ))𝑅𝑋 −𝜇𝐽1 (2∆𝜙𝑎 )𝑅𝑦

.

We measure phase and amplitude signal under different concentration of glucose (cf. Fig.1 (c)). From this result, we estimate a sensitivity around 10-6 RIU.

Figure 1. (a) Interference Fringe observed in water. (b) interferogram signal. (c) phasogram and amplitude signal under D.I. water and concentration from 0.75% to 11% of glucose. References [1] Chang, Chia‐Chen, et al. Journal of the Chinese Chemical Society 60.12 (2013): 1449-1456. [2] Chuang, Tsung-Liang, et al. Lab on a Chip 14.16 (2014): 2968-2977.

Acknowledgement We thank Minister of Science and Technology of Taiwan for funding support through project MOST 105-2221-E002-016-MY3.

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P048 Enhanced ammonia sensing based on vapour phase polymerisation of PANi/PPy/TiO2 hybrid nanocomposite Chu Van Tuana*, Hoang Thi Hiena,b, Ho Truong Giangb, Tran Trunga a

Hung Yen University of Technology and Education, Hung Yen, Vietnam Institute of Materials Science, Vietnamese Academy of Science and Technology, Hanoi, VietNam

b

Email: [email protected]

Abstract A new ammonia sensing made from hybrid nanocomposite of titan dioxide (TiO2)-was fabricated on polyaniline (PANI) and polypyrrol (PPy) through a simple vapour phase polymerisation method. The surface structure analysis conducted through scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the diameters of the synthesized PANi/PPy/TiO2 was about 50–100 nm. The chemical composition structure of the PANi/PPy/TiO2 composites was studied by Fourier-transform infrared (FT-IR) spectroscopy. Energy-dispersive X-ray spectroscopy (EDS) was applied to identify the composition of PANi/PPy/TiO2 hybrid nanocomposite. The obtained results demonstrate the applicability of the PANi/PPy/TiO2 hybrid nanocomposite to improve the sensitivity, response time, and recovery time of NH3 gas sensors.

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P049 On the dynamics of photo-generated carriers in Si-Ge quantum dots Ngo Ngoc Ha International Training Institute for Materials Science, Hanoi University of Science and Technology, Addr: No 1 - Dai Co Viet Str. Hanoi, Vietnam. Email: [email protected]

Binary alloys of SiGe have attracted much attention as functional materials for advanced electronics in recent years. In this study, we report preparation and characterization SiGe alloys quantum dots with various Ge compositions. The materials have been obtained by co-sputtering, followed by a heat treatment process. X-ray diffraction data and high-resolution electronic transmission images have revealed the formation of single phase nanoparticles in face-centered cubic structure of the SiGe alloys with lattice constant increased with a large range of the Ge composition. Photo-generated carriers in the quantum dots were investigated by mean of transient induced absorption. The carrier relaxation features multiple components, interpreted for different photogenerated carrier relaxation routes. Deep carrier traps, characterized by a long-range Coulombic potential, are identified at the boundary between the Si-Ge quantum dots and the SiO2 host with the ionization energy of about 1 eV. These are responsible for rapid depletion of free carrier population within a few picoseconds after the photo-excitation, which explains the low emissivity of the investigated materials, and also sheds light on the generally low luminescence of SiGe alloy systems.

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P050 Unravelling the nanostructures of supramolecular assemblies of intermolecular bonding of hydroxyquinolines on Au(111) Thu-Hien Vua, Thomas Wandlowskib a

International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, No. 1 Dai Co Viet, Hanoi, Vietnam b Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland Email: [email protected]

We study the formation of hydrogen bonding in 8-, 5-, and 2-hydroxyquinolines (8-, 5- and 2hqs) molecular assemblies on a Au(111) substrate surface, using cyclic voltammetry (CV) and in situ scanning tunneling microscopy (STM). Our results indicate that, at a negatively charged surface, three molecules form highly ordered physisorbed adlayers with their phenyl rings parallel to the substrate surface. High resolution STM images reveal the packing arrangement and internal molecular structures. Stripe patterns are composed of dimer rows of 8- and 2-hqs, which are stabilized by hydrogen bonds between two functional groups, OH and N. A different position of the OH moiety in 5-hq results in a distinctly different structure (grid-like motif). Increasing the electrode potential further to positive charge densities of Au(111) destabilizes all hydrogen-bonded networks of the planar adsorbed molecules. 2-hq forms disordered chemisorbed adlayers. The molecules of 8- and 5-hqs undergo an electrochemical oxidation.

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P051 An Au-TiO2-Ti Structure Based Schottky Barrier Surface Plasmon Resonance Sensor Enables Miniaturization of SPR Sensing System Chao Wang1, Chen-Hsuan Hsia1, Jian-Hong Yang2, Chii-Wann Lin1* 1

Institute of Biomedical Engineering, National Taiwan University, No.49, Fang-Lan Rd., Taipei City 10672, Taiwan 2 Institute of Mechanical Engineering, National Taiwan University, No.1, Sec.4, Roosevelt Rd., Taipei City 10617, Taiwan Email: [email protected]

In this article, we propose a Surface Plasmon Resonance (SPR) sensor design based on MetalDielectric-Metal (MDM) structure on a prism coupler, which merges the merits of SPR with this miniaturized Au-TiO2-Ti MDM device. The detecting theory of the sensor could be explained by electro-optical energy conversion theory. The damping of SP waves, namely the perturbation to the thermal equilibrium, happens simultaneously when wave propagates along the Au-TiO2 interface. As a result, hot electrons and equivalent hot holes are excited and emitted from metal to dielectric. Schottky barrier formed with well-matched metal and semiconductor helps to collect the plasmonic hot electrons as photocurrent and block the noise. Performance of the sensor is discussed and predicted by FDTD and MATLAB simulations. A dynamic range covers refractive index from 1.332 to 1.338 R.I.U could be obtained by concentration identification simulation. The electric field strength near the TiO2-water interface is ~16 times of incident field, and the penetration depth of e-field into water is over 180nm, which meets the requirements of using it as a biosensor.

Figure 1 a) The exterior details of the proposed MDM sensor. b) The cross section view of the sensor together with prism coupler, and the layers information. c) Band diagram of device. d) MATLAB simulation results. e) FDTD simulation results. Acknowledgement: This study was supported in part by the Ministry of Science and Technology of R.O.C. under grant MOST 106-2221-E-002-059-MY2. 209

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P052 Surface Functionalization of Gold Surfaces with Polypeptide: A Low-Fouling Zwitterionic Surface for Detecting Placenta Growth Factor W.E. Hsua, C.H. Yangb, C.C. Changa, S.C Weic, C.W. Lina a

b

Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan c Department of Internal Medicine, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan. Email: [email protected]

In Taiwan, the incidence rate of colorectal cancer has become first for seven consecutive years. Placental growth factor (PlGF) is a biomarker of colorectal cancer which can be used as one of the risk factors for prognosis recurrence. In this study, we use surface plasmon resonance (SPR) for detection of PlGF in patient's serum. SPR has many advantages, including high sensitivity, real-time detection, and non-fluorescent labeling. However, non-specific adsorption results in error signals. We used mixed amino acid sequences for protein anti-fouling and antibody modification. This method can detect the presence of PlGF in serum, and the limit of detection(LOD) is 2pg/ml. We also used clinical samples to compare ELISA and SPR, our method showed 60% accuracy.

Figure (a) Fabrication of Au film with antifouling properties: anti-fouling peptide (AFP): EKEKEKEPPPP-C and probe peptide (PP): RRGW-EKEKEKE-PPPP-C. (b) SPR detection of PlGF in 1xPBS solution, ranging from 2 pg/ml to 100 pg/ml. (c) Calibration curve of PlGF in 1xPBS solution.

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P053 Spatial Selective Surface Functionalization of Surface Plasmon Resonance Biosensor via Thiol-Ene Click reaction Yi-Ming Chen1, Tzu-Heng Wu2, Hui-Wen Liu1, Ya-Ting Tsai3, Hsien-Yeh Chen3*, Chii-Wann Lin1,2* 1

Institute of Biomedical Engineering, National Taiwan University, No. 49, Fanglan Rd., Da'an Dist., Taipei, Taiwan 2 Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, No. 49, Fanglan Rd., Da'an Dist., Taipei, Taiwan 3 Institute of Chemical Engineering, National Taiwan University, No.1, Sec. 4 Roosevelt Rd., Taipei, Taiwan *Corresponding author, email: [email protected], [email protected]

In this study, we proposed a method of surface functionalization using parylene (Poly(pxylylenes) thin film. The polymer film is deposited via chemical vapor deposition (CVD)[1-3], which provides vinyl group for further click reaction. As a proof-of-concept experiment, a 25 mer thiolated DNA probe molecule is anchored on the polymer layer through UV triggered thiolene reaction [4,5]. During functionalization, a digital light processing (DLP) system directs UV light to exert spatiotemporal control of the reaction (Fig.1a), while the reaction is closely monitored via Surface Plasmon Resonance (SPR). According to the simulation and experimental results (Fig.1b and Fig.1c), the optimized parylene film thickness should be around 20 nm. Overly thick polymer layer leads to large SPR angle shift beyond working range. Through the DNA functionalization experiment, we demonstrate spatially selective functionalization as shown by SPR signal (Fig.1d). Moreover, the reaction rate is about 8.9 times faster than widely applied thiol-gold reaction.

Figure 1. (a)The cross-section of SPR biosensor chip. (b) Simulation result for SPR angle shift with different thickness of parylene film coated on the chip. (c) Simulation result for SPR curve of the thickness of gold film. (d)The result of spatially selective functionalization. The UV exposure was performed only on Area1. Reference [1] Chen, Hsien-Yeh, et al. (2007) Proceedings of the National Academy of Sciences 104.27: 11173-11178. [2] Chen, Hsien-Yeh, et al. (2010) Langmuir 27.1: 34-48. [3] Wu, Jyun‐Ting, et al. (2012) Macromolecular rapid communications 33.10: 922-927. [4] Posner, Theodor. (1905) European Journal of Inorganic Chemistry 38.1: 646-657. [5] Hoyle, Charles E., et al. (2010) Angewandte Chemie International Edition 49.9: 1540-1573. Acknowledgement: The authors would like to thank National Taiwan University Nano-Electro-Mechanical-Systems research center and Dr. Hsien-Yeh Chen’s research group (National Taiwan University). We thank Minister of Science and Technology of Taiwan for funding support through project MOST105-2221- E-002- 016-MY3.

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P054 Gas-Sensing Performance Study of Indium Oxide Material Chen Yang, Xie LiLi, Zhu ZhiGang* School of Environmental and Materials Engineering, College of Engineering, Shanghai Polytechnic University, No. 2360 Jinhai Road, PuDong New Area, Shanghai, 201209, China. Email: [email protected]

Abstract: Indium oxide has a high conductivity and high visible light transmittance, which is widely used in ultraviolet lasers, solar cells, photocatalysts, flat panel displays, sensors and many other areas. The indium oxide nanometer particles were prepared by hydrothermal method, and the indium oxide nanocomposite were prepared by hydrothermal method as well. The structure and morphology of the powder product were characterized by X-ray diffraction and SEM. Gas sensing properties of In2O3 specimens were measured by the static state method. The results show that the pure indium oxide based sensor has high sensitivity to NO2 and alcohol, but the selectivity is poor. Indium oxide nanocomposite based sensor is able to selectively detect alcohol with high sensitive and quick response/recovery time. It turned out that the sensor had almost no response to other gases. The sample of copper composited Indium oxide could be used in the preparation of Ethanol sensor．

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P055 Facile synthesis of MnFe2O4/graphene nanocomposite and its application for electrcatalytic oxidation of hydrogen peroxide Xueling Zhao, Cheng Chen, Zhanhong Li, Yihua Wu, Zhigang Zhu School of Environmental and Materials Engineering, College of Engineering, Shanghai Polytechnic University, Jinhai Rd 2360, Pudong, Shanghai 201209, P. R. China. Email: [email protected]

Determination of H2O2 turns to be of much significance because of its important roles not only as a side product of many enzyme-involved reactions but also as a signaling molecule to regulate various biological processes. In this paper, a sensitive and selective amperometric hydrogen peroxide (H2O2) biosensor was obtained by using MnFe2O4/rGO magnetic nanocomposite modified glassy carbon electrode (GCE). The morphology of the prepared MnFe2O4/rGO was characterized by transmission electron microscopy (TEM). The step-wise modification and the electrochemical characteristics of the resulting biosensor were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry methods. Thanks to the MnFe2O4/rGO-promoted fast electron transfer at the fabricated interface, the developed biosensor exhibits an excellent electrocatalytic activity and better response performance for non-enzymatic hydrogen peroxide detection than those of rGO and MnFe2O4 modified sensors. In addition, the favorable biocompatibility of this electrode interface endows the prepared biosensor with good anti-interferent ability and long-term storage stability. It is promising that the proposed sensor will be utilized as an effective tool to quantitatively monitor the dynamic changes of H2O2 in biological systems.

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P056 A Study on measuring dissolved H2 gas in transformer oil using the SnO2 thin film resistive sensor sensitized with Pd islands Hoang Si Hong*1, Hoang Van Phuoc1, Nguyen Van Dua1, Nguyen Thi Lan Huong1, Nguyen Thi Hue1, Nguyen Van Hieu2, Nguyen Van Toan2 1-School of Electrical Engineering, Hanoi University of Science and Technology, 2- International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, No 1 - Dai Co Viet Str. Hanoi, Vietnam. Email: [email protected] Recently, research on sensors that measure concentration of dissolved gases in the transformer oil are very necessary. Those dissolved gases are generated by thermal decomposition of oil at high temperatures or partial discharging in transformer oil. Results of measurement are significant important to diagnose the failure of transformer as soon as possible. Among many different dissolved gases such as hydrocarbons (CmHm), carbon oxides (COx), nitrogen oxides (NOx), and hydrogen (H2), the detection of H2 gas is the most important because the concentration of dissolved H2 varies at different levels of faults in the transformer. There are now some groups studying on dissolved H2 sensor in transformer oil. More specifically, groups of A.S.M. Iftekhar Uddin applied resistivity – type sensor structure based on palladium (Pd)-decorated zinc oxide (ZnO) nanorod (NR) array. Besides, Jerzy Bodzenta and partners fabricated sensor to detect concentration of H2 from 200 ppm – 1500 ppm in the transformer oil by optimizing Pd thin film.

Figure 1- Structure of sensor

Figure 2 - The measure system

Figure 3- Result of measurement in transformer oil condition

Additionally, our group succeeded in fabrication of H2 gas sensor based on SnO2 thin film sensitized with microsized Pd islands. The sensor composes of a micro-heater and a pair of n film, oxidized silicon (Figure 1) and the measurement condition is dry air. By using Pd islands as a catalyst helps improving H2 gas sensitivity of SnO2 thin film because of easy controlling and

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adjusting size of Pd islands to reach the highest sensitivity. Based on measurement results in dry air condition, our group tested the sensitivity of Pd/SnO2 sensor with H2 in transformer oil condition. The measurement system was set up as Figure 2. This system contains a transformer oil chamber which could control the temperature, Pd/SnO2 fabricated sensor and a resistivity meter. The result in Figure 3 shows that Pd/SnO2 fabricated sensor could detect hydrogen gas at concentrations of 0 – 2000 ppm with 40 second of response time.

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P057

P-type semiconducting NiO nanoannulars: synthesis and application for gas sensors Pham Long Quang1, Tran Thai Hoa1, Hoang Thai Long1, Nguyen Duc Cuong1,2,* 1

2

University of Sciences, Hue University, 77 Nguyen Hue, Hue City, Viet Nam School of Hospitality and Tourism, Hue University, 22 Lam Hoang, Hue City, Viet Nam

Metal oxide unique nanostructures are potential candidates for gas sensors. The present work focused on the simple and scalable fabrication of the p-type semiconducting NiO nanoannulars for application in gas sensor. The analyzed morphology and crystal structure indicated that the NiO nanostructures have a uniform population with fascinating annular shape, each containing an interior concavity in the hexagon. The gas sensing properties of the NiO unique nanostructures exhibited good sensitivity, remarkable selectivity, and high stability toward hydrogen sulfide gas. The proposed strategy has potential in the preparation of other metal oxides to achieve high-performance gas sensors. Keywords: p-type semiconductor, NiO nanoannulars, hydrosulfide, gas sensors

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P058 Nanosphere Lithography for Fabrication of Downscaled Nanoporous Biosensor Agnes Purwidyantria*, and Chao-Sung Laib,c,d* a

Biomedical Engineering, Chang-Gung University, Taoyuan, Taiwan Department of Electronic Engineering, Chang Gung University, Taoyuan, Taiwan c Department of Nephrology, Chang Gung Memorial Hospital, Taoyuan, Taiwan d Department of Materials Engineering, Ming-Chi University of Technology, New Taipei City, Taiwan Email: [email protected], [email protected]

b

Downscaling technique has gained great attention in both research and industries nowadays. Among a variety of complex and highly priced instrumentation for achieving precisely high aspect ratio of the device, such as by the use of electron beam lithography (EBL), NSL has been noted as an inexpensive alternative providing both top down and bottom up features in nanostructuring pathway [1]. However, during drop casting of the PS template onto the targeted substrate, the use of tiny sized particles (<500 nm) for monolayer coverage in the substrate is cumbersome due to the hard separation of the particles in solution phase [2]. In this research, we aim the monolayerity of 100 nm PS nanosphere template for Au nanoporous bacterial sensor through NSL. Results denote that the downscaled structure ultimately provided high electroactive surface area for effective hybridization of S. aureus 16S rRNA in electrochemical sensing system.

Figure 2. SEM figures of a. monolayer coverage of 100 nm PS nanoballs by NSL, b. generated Au nanoporous membrane after PS etching

Figure 1. Process flow of the downscaled Au nanoporous bacterial sensor by NSL using 100 nm PS Figure 3. a. CV behavior of Fe(CN6)3−/4− redox couple, b. CV signal from golden samples and c. from cDNA hybridization of S. aureus 16S rRNA

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P059 The Research on Photovoltaic Performances of Dye-sensitized Solar Cell by Appling TiO2-Reduced Graphene Oxide - IGZO Photoelectrode Chien-Hung Kuoa, Jung-Chuan Choua,b,*, Yi-Hung Liaoc, Chih-Hsien Laia,b, Pei-Hong Youa, Chang-Chia Lub a Graduate School of Electronic Engineering, National Yunlin University of Science and Technology, Yunlin, Taiwan b Department of Electronic Engineering, National Yunlin University of Science and Technology, Yunlin, Taiwan c Department of Information and Electronic Commerce Management, TransWorld University, Yunlin, Taiwan Email: [email protected]

In this study, the titanium dioxide(TiO2) – reduce graphene oxide(RGO) – IGZO composited photoelectrode(TGICP) had been fabricated. According to experimental results, the short circuit current density(JSC) was increasing from 10.2 mA/cm2 to 13.25 mA/cm2. It contributed the photovoltaic conversion efficiency increased from 4.31% to 5.89%. It could be attributed to decrease in reverse current density. The reason of causing reverse current density was reverse recombination. The main reason of causing reverse recombination was two recombination paths. One was photo-generated electron recombined with oxidized-dye, which could be improved by RGO. Due to the high mobility of RGO, which could accelerate the photo-generated electron from conduction band of TiO2 to conduction band of fluorine doped tin oxide(FTO) glass. The other path was photo-generated electron recombined with I3- which in electrolyte. This reverse recombination could be improved by IGZO, the IGZO could form an energy barrier to prevent electron from recombining with I3-. The characteristics of TGICP had been investigated by Scanning Electron Microscopy(SEM), Electrochemical Impedance Spectroscopy(EIS), Energy Dispersive Spectrometer(EDS).

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P060 Self-heating H2S gas sensor using a network of SnO2 nanowires functionalized with Ag Trinh Minh Ngoc1, Chu Manh Hung1, Nguyen Ngoc Trung2, Nguyen Duc Hoa1, Nguyen Van Duy1, Nguyen Van Hieu1 1

International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, Hanoi, Viet Nam, No. 1 Dai Co Viet, Hanoi, Viet Nam 2 School of Engineering Physics, Hanoi University of Science and Technology, No. 1 Dai Co Viet, Hanoi, Viet Nam * Corresponding author: [email protected]

In this work we demonstrate the fabrication of self-heating H2S gas sensor using a network of SnO2 nanowires functionalized with Ag. A network of SnO2 nanowires was grown on a pair of Pt/Cr electrodes by a chemical vapor deposition method. After that a thin layer of Pt was coated by using a sputtering. The device was then heat treated at 400oC for 2h to stabilize the sensor. H2S sensing properties were measured at room temperature by applying various powers ranging from 0.25 to 2 mW. Results pointed out that the device showed good response and recovery characteristics with high sensitivity. The developed device is suitable for room temperature monitoring H2S gas at low concentration.

Figure 1. Transients resistance versus time of the sensor upon exposure to 0.5 ppm H2S under various applied powers

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P061 Low Resistance, Energy Band-Aligned 0D/2D PbS/MoS2 Hybrid Gas Sensors Jingyao Liu, Zhilong Song, Zhixiang Hu, Shuqin Yang, Naibo Gao, Qian Liu, Wenkai Zhang, Hao Kan and Huan Liu* School of Optical and Electronic Information, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei, 430074, P. R. China. Corresponding Author Email: [email protected]

The hybrid 0D-2D architecture has emerged as a material platform for designing the highperformance, low cost electronic and optoelectronic devices. While having a large, sensitive surface area which is highly desirable for gas sensing, colloidal quantum dot (CQD) solids usually have a low mobility. Instead, 2D nanomaterials, such as transition metal dichalcogenides (TMDs) may serve as the high charge transport way due to their high in-plane carrier mobility, offering a unique opportunity to overcome the mobility-bottleneck of CQD-based devices. Motivated by this strategy, we constructed 0D PbS CQD/2D MoS2 hybrid structure for NO2 gas sensing. Attributed to the distinct workfunction value between PbS CQD and MoS2, the resistance of the hybrid sensor was about threefold decrease in comparison with the pristine PbS CQD sensor without compromising the sensing performance (See Figure 1). Furthermore, the p-type PbS CQD films with bandgaps ranges from 0.7 eV to 1.4 eV was tuned and the energy band alignment with the MoS2 will be investigated to achieve optimal gas-sensing response. Then 0D PbS CQD/2D MoS2 hybrid gas sensors exhibited a higher response toward NO2 compared to the pristine PbS CQDs or MoS2 owing to the synergetic effect of 0D PbS and 2D MoS2.

Figure 1. Resistance curves and response curves of the PbS CQD/MoS2 sensor compared to the pristine PbS CQD sensor towards 50 ppm NO2 respectively.

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P062 H2S-Sensing Properties and Mechanism of Nanocrystalline WO3 Films Zhixiang Hu, Haoxiong Yu, Zhilong Song, Jingyao Liu, Shuqin Yang, Huan Liu* School of Optical and Electronic Information, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei, 430074, P. R. China. Corresponding Author Email: [email protected]

Metal oxide semiconductor gas sensors simply rely on the resistance change upon gas exposure, thereby promising desirable ease of operation. Nanocrystalline metal oxides have been intensly investigated with the aim of higher sensitivity and lower operating temperature. In this work, tungsten trioxide (WO3) nanocrystals were synthesized by a solvothermal method and the effect of reaction time on their morphologies was studied. For the sensor device construction, the assynthesized WO3 nanocrystals were spin-coated onto substrates, followed by a ligand exchange treatment. The nanocrystalline WO3 films were selective and sensitive toward H2S gas, with a response of 57 to 50 ppm of H2S at 80 °C; the response and recovery time was 46 s and 126 s, respectivley. In addtion to the classic gas-sensing mechanism model of semiconductors, we studied the H2S-sensing mechanism of nanocrystalline WO3 films through the first-principles calculations based on density functional theory, where the adsorption behavior of both H2S and O2 on the reductive and oxidative surface of WO3 were respectively identified.

Figure 1. (A)The selectivity of the WO3 nanocrystals sensor at 80 °C, the inset displays response curves toward 50 ppm H2S at 80 °C. (B) Adsorption model of H2S on WOterminated (200) surface.

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P063 H2S sensing properties of α-Fe2O3 nanofibers fabricated by electrospinning method Nguyen Van Hoanga,b*, Phan Hong Phuoca, Nguyen Van Dunga, Nguyen Duc Hoaa, Nguyen Van Duya, Dang Thi Thanh Lea, Chu Manh Hunga, Nguyen Van Hieua* a

International Training Institute for Materials Science, Hanoi University of Science and Technology, Addr: No 1 - Dai Co Viet Str. Hanoi, Vietnam. b Department of Materials Science and Engineering, Le Quy Don Technical University, Addr: No 236 – Hoang Quoc Viet Str. Hanoi, Vietnam. Email: [email protected]; [email protected]

In this study, α-Fe2O3 nanofibers were synthesized via electrospinning method, followed by annealing at the temperature of 600 oC in ambient conditions. The contents of precursor solution used for electrospinning were changed by the modulation of the amount of ferrous salt and polymer concentration. The samples were then characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDX). The impacts of the contents of the precursor solution on H2S gas sensing performances of the sensors based on α-Fe2O3 nanofibers were also investigated. The gas testing results showed that when the amount of ferrous salt increased from 0.2 g to 0.8 g, the sensor responses rose and reached the maximum of 6.2 with 0.4 g of ferrous salt, then decreased. Meanwhile, when the polymer concentration in the precursor solution increased from 7 to 15 wt.% PVA, the sensor responses decreased to 8.4 and 2.9, respectively. These results were explained by the extensive effects of the contents of the precursor solution on morphologies and structures of α-Fe2O3 nanofibers, leading to a change in H2S gas sensing performances of the sensors based on α-Fe2O3 nanofibers.

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P064 Flexible hydrogen gas sensor based on Pt-SnO2 thin film Sputtered on polyimide substrate Vo Thanh Duoc, Nguyen Xuan Thai, Nguyen Van Duy, Nguyen Van Hieu International Training Institute for Materials Science, Hanoi University of Science and Technology, Addr: No 1 - Dai Co Viet Str. Hanoi, Vietnam. Email: [email protected]

We report the gas sensing properties of SnO2 thin film - coated Pt prepared by sputtering technology onto polyimide substrate for low temperature hydrogen detection. Platinum (Pt) electrodes were fabricated by photolithographic method, followed by sputtering deposition on the flexible substrate, and then SnO2 and Pt thin film were sputtered onto and between the fringes of electrodes. Thermal annealing at 350°C was applied to stabilize the Pt-SnO2 thin film sensor. The morphology and structure of the fabricated sensor were studied by SEM, XRD, whereas hydrogen sensing properties were measured at different temperatures. The stability of the sensor after bending processes was also investigated, indicating the possibility of fabricating highly efficient and practical flexible H2 gas sensor.

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P065 Controlling of the diameter and density of silicon nanowires prepared by silver metal-assisted chemical etching Le Thanh Cong1,2, Nguyen Thi Ngoc Lam1, Nguyen Truong Giang1, Nguyen Duc Dung2 and Ngo Ngoc Ha1,* 1

International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology (HUST), No. 1 Dai Co Viet Str., Hai Ba Trung dist., Hanoi, Vietnam 2 Advanced Institute for Science and Technology (AIST), Hanoi University of Science and Technology (HUST), No. 1 Dai Co Viet Str., Hai Ba Trung dist., Hanoi, Vietnam *Corresponding author: [email protected]

Silicon nanowires (SiNWs) prepared by silver (Ag) metal-assisted chemical etching (MACE) method are investigated by mean of the electron microscopy. Ag particles, used as the catalytic metal, are formed on Si (100) wafers at room temperature after the reduction reaction in the solution of HF and AgNO3. The growth of SiNWs was carried out by the immersion of the Si substrate covered with Ag particles in a solution of HF and H2O2. Changing of AgNO3 concentration, so as to control the size of the Ag particles on the Si wafers can determine the size and density of the SiNWs. For lower AgNO3 concentrations, smaller Ag particles formed, thus larger SiNWs were made. Size and density of SiNWs decreased with the increase of AgNO3 concentration. We also found that the growth rate of SiNWs is found to depend nonlinearly on the time of etching.

Figure 1. The nonlinear dependence of SiNWs length on etching time over the investigated time scale of about 2 h

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P066 Electrochemical behaviors of Fe2O3 inside carbon nanotubes in alkaline solution Bui Thi Hanga, Vu Manh Thuana, Doan Ha Thangb a

International Training Institute for Materials Science, Hanoi University of Science and Technology, Hanoi, Addr: No 1 - Dai Co Viet Str. Hanoi, Vietnam. b Department of High Technology, Ministry of Science and Technology, Addr: No 113 - Tran Duy Hung Road, Hanoi, Vietnam. Email: [email protected];[email protected]

To find the anode material for Fe-air battery, Fe2O3 inside carbon nanotubes (CNTs) was prepared by filling iron nitrate in carbon nanotubes and followed heating process in argon flow. The structure of this material was investigated by X-ray diffraction (XRD) measurement. Their morphology and particle size were observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). It was found that morphology, particle size and amount of iron oxide that filled in CNTs depend on the amount of iron nitrate precursor. When iron content was 5 wt% almost iron oxide particles resided inside CNTs and their particle size was smaller than that of iron content was 10 wt%. The preparation conditions may affect the morphology, particle size of Fe2O3 inside CNTs material. The different in morphology, particle size of the materials will affect to their electrochemical properties that were investigated using cyclic voltammetry (CV).

Figure 1. TEM images of as-synthesized Fe2O3 inside CNTs

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P067 Co-implanted electrospun ZnO nanostructure sensor for superior detection of NO2 gas Le Thi Hong1, Nguyen Van Hoang1, Nguyen The Nghia2, Nguyen Van Duy1, Nguyen Duc Hoa1, Chu Manh Hung1,*, and Nguyen Van Hieu1 1

International Training Institute for Materials Science, Hanoi University of Science and Technology, No.1 - Dai Co Viet Str. Hanoi, Vietnam. 2 Faculty of Physics, VNU University of Science, Vietnam National University, 334-Nguyen Trai, Thanh Xuan, Hanoi, Viet Nam *Email: [email protected] / [email protected]

Zinc oxide (ZnO) nanostructures with a wide band gap of 3.37 eV and a large exciton binding energy (60 meV) at room temperature, is a multi-functional semiconductor towards electronic, optoelectronic, piezoelectric, and gas sensor device application. In the context of the gas sensor application, ZnO nanostructures with a large surface to volumn ratio has been demonstrated as a good sensing material for detecting various inflammable and toxic gases. In addition to the intrinsic property of ZnO nanostructures, ion implantation of desired elements into the sensing materials results in an enhancement of the sensor’s performance. The implantation process normally generates defects in the ZnO nanostructures as well as on surface of the nanostructure, creating more adsorption sites for oxygen and target gas molecules. The dopant may also play a role as an activator for promoting the interaction between target gas with the sensing layer. Therefore, in the present work we employ a 5SDH-2 Pelletron accelerator to implanted ion Co2+ into the as-electrospun ZnO nanostructure. The NO2 sensing property of the sensor based on asspun and Co-implanted spun ZnO nanostructures is investigated. The finding shows a significant increase of the 10 ppm NO2 gas response from 17 for the as-electrospun ZnO sensor to 208 for the Co-implanted electrospun ZnO sensor at 150 ºC as shown in Figure 1

(B)

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Figure 1. (A) and (B) are SEM images of as-electrospun and Co-implanted electrospun ZnO nanostructures, respectively. Insets are NO2 gas responses of these two sensing materials at various concentrations and temperatures.

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P068 Controlled growth of indium oxide nanowires for gas sensing applications Dang Ngoc Son 1*, Nguyen Van Duy1, Le Xuan Thanh2, Nguyen Duc Hoa1 1

International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, No 1 Dai Co Viet Road, Hai Ba Trung, Hanoi 2 Faculty of electronic, Posts and Telecommunications Institute of Technology, Nguyen Trai, Hanoi Email:[email protected] Abstract The nanowires of indium oxide semiconductor as chemical sensing material have attracted enormous attention due to their advantageous features. In this paper, we fabricated singlecrystalline indium oxide nanowires (NWs) on SiO2/Si substrate under controlled conditions via a simple thermal vapor deposition method with the gold catalyst. The temperature substrates and the ambient pressure in the quartz tube was controlled, and the dependence of NW dimension and density was investigated. The sensing properties of sensors based on In2O3 nanowires bundles toward ethanol have been tested at various operating in the temperatures range between 300 and 450 °C. Our results clearly show the potential of using In2O3 as building blocks for future chemical gas sensor. Keywords: gas sensor, nanowires, In2O3 nanowires, 1D nanostructure, growth of In2O3.

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P069 Carbon monoxide sensing of Pd nanoparticles functionalized on the surface of hydrothermally synthesized WO3 nanorods Pham Van Tonga*, Nguyen Thi Hanha, Do Thi Thu Hanha, Luu Hoang Minha, Nguyen Duc Hoab a

Department of Physics, Faculty of Mechanical Engineering, National University of Civil Engineering (NUCE), No. 55, Giai Phong Str., Hanoi, Viet Nam b International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology (HUST), No. 1, Dai Co Viet Road, Hanoi, Viet Nam Email: [email protected]

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Abstract - Decoration of noble metal nanoparticles (NPs) on the surface of nanostructured semiconducting metal oxide to increase gas-sensing performance is one of the most effective pathways. Herein, we introduce a facile method for the decoration of Pd NPs on the surface of WO3 nanorods to enhance CO gas-sensing performance. The WO3 nanorods were synthesized by hydrothermal method and heat treated before decoration Pd NPs on the surface. Thereafter, Pd NPs were decorated on the surface WO3 nanorods by direct reduction of the complex Na2PdCl4 using Pluronic as a surfactant and reducing agent. The materials were characterized by SEM, EDS, HRTEM and XRD. The gas-sensing characteristics of bare WO3 and Pd-WO3 nanorods were tested for CO, NH3, H2, CH4 and CO2 detection at different temperatures. The results show that the gas-sensor Pd-WO3 improves performance to CO at concentration (10–200 ppm) with fast response–recovery time (in seconds), and high sensitivity. 300 200 100

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P070 Strong effect of ZnO nano-structures on response/recovery times to room temperature NO2 gas sensing under UV assistance Do Thi Anh Thua, Do Thi Thua, Hoang Thi Hienb,c, Pham Quang Ngana, Giang Hong Thaia, Chu Van Tuanb, Ho Truong Gianga,*, Tran Trungb a

Institute of Materials Science, Viet Nam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Viet Nam b Hung Yen University of Technology and Education, Khoa Chau, Hung Yen, Viet Nam c Graduate University of Science and Technology, Viet Nam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi, Viet Nam Email: [email protected]

In this work, we have investigated NO2 gas sensing characteristics when utilized the ZnO nanostructures (nano-rods, nano-flowers and highly-porous surface nano-flowers) synthesized by a simple route of hydrothermal process. The calculated average diameter of the samples increases in order of the structures of nano-rods, highly-porous surface nano-flowers and nanoflowers. The ZnO nanostructures based sensors were studied when exposed to NO2 gas (1, 2, 3 and 4 ppm) at room temperature under continuous illumination of UV-LED (385 nm). The ZnO nano-rods exhibited the slowest response/recovery times while the ZnO nano-flowers had the fastest response/recovery times. Furthermore, the NO2 gas-sensing response of the ZnO nanorods sensor was observed to have sharp decrease with increase the UV intensity. Correlation between the NO2 gas sensing performance and optical property of the ZnO nanostructures were discussed. Defects of the ZnO nanostructures, particularly in their surface regions, was considered to have strong effect to the response-recovery times and sensitivity to NO2 gas. The characteristic could relate to charge carrier recombination of the ZnO nanostructures when exposed to NO2 gas under UV interaction. The results in this work also showed that the large size particles could enhance the room temperature gas sensing performance in case of using the metal-oxides (ZnO) based sensor under the UV assistant.

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P071 Growth of SnO nanoplates at low temperature by chemical vapour deposition method for gas sensor application Pham Tien Hung, Sang-Wook Lee, Joon-Hyung Lee, Jeong-Joo Kim, Young-Woo Heo* School of Materials Science and Engineering, Kyungpook National University, Daegu, 702-701, Korea; E-mail: [email protected] Tin mono-oxide nanostructures have attracted considerable attention owing to its potential application in various fields, such as a catalyst, a coating substance, a thin film transistor, a anode material for lithium-ion batteries and a gas sensor. However, SnO is unstable thermodynamically above 543 K, and the disproportionation and oxidization reaction of SnO are easily progressed under redox or inert atmosphere conditions. Therefore, it was hard to obtain SnO nanocrystal with high purity. In this article we report on the growth of SnO nano-plates below the growth temperature of 400°C by thermal chemical vapour deposition. The crystalline structure and surface morphologies of materials were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The results showed that the yellowgray-black materials were composed of SnO nano-plates (40-90 nm in plate thickness, 0.38-1.69 μm in plate diameter, layer thickness of 900 nm) which was nanotetragonal phase SnO. In addition, the influence of growth temperature on the shape and size of SnO nano-plates were also investigated. A growth mechanism was proposed to explain the growth of the SnO nano-plates. Subsequently, the NO2 sensing characteristics of the synthesized nanoplates were tested at different temperatures, and showed a reversible response to NO2 at various NO2 concentrations. Finally, the sensing mechanism based on the models of carrier transport and plate-to-plate contact has been proposed and discussed.

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Figure 1. SnO nanoplates: FE-SEM image (a) and XRD pattern of as-synthesized (b) by thermal chemical vapor deposition method. 230

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P072 Nano-film aluminum-gold for ultra-high dynamic range surface plasmon resonance chemical sensor Briliant Adhi Prabowoa, Kou-Chen Liub a

Research Center for Electronics and Telecommunication, Indonesian Institute of Sciences, Bandung 40135, Indonesia. b Department of Electronics Engineering, Chang Gung University, Taoyuan 33302, Taiwan. Email: [email protected]

An analytical study of nano-film aluminum (Al) for ultra-high dynamic range surface plasmon resonance (SPR) biosensor is presented in this article. Surface plasmon resonance is one of biochemical sensor platform that attracts a lot of attention from scientists in the recent decades[1]. A thin film of 16 nm Al is proposed for sensing metal layer for SPR sensing. For protective layer, 10 nm of gold (Au) layer is designed on the top of Al sensing as a protection layer. An analytical approach of this study was simulated and compared to the other sensing structures for the references. We found that using proposed SPR sensing layers, a dynamic range up to 1.45 RIU solution is achieved. This high value of bulk refractive index solution is comparable to the 63.5 wt% of sucrose water concentration. This huge number of refractive index value limit by this sensing design is potentially implemented in several applications, such as environmental monitoring and chemical detection study for high refractive index solution sample.

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Figure 1. (a) The Al sensing protected by thin Au film for SPR sensor lease prepare a graphical abstract for your presentation. (b) The proposed metal sensing response to the samples with various refractive index value. (a) Reflectivity dip shifting. (b) The detection response and its range of proposed sensing layers compared to the other sensing structures.

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P073 A highly sensitive and selective impedimetric sensor based on surface molecularly imprinted polymer (MIP) film coated gold nanoparticles for fluoroquinolone antibiotic detection Phi Van Toan, Nguyen Quoc Hao, Nguyen Vu Quynh, Hoang Trung Anh and Truong TN Lien School of Engineering Physics, Hanoi University of Science and Technology, No 1 Dai Co Viet, Hai Ba Trung, Hanoi, Vietnam E-mail: [email protected]

Artificial MIP bioreceptors have many advantages in terms of high durability and stability compared to natural bioreceptors in severe environment such as high degree of pH, high pressure, and extremely hot or cold temperatures. MIPs can be used in months without losing functional efficiency. It also has much simpler conservation requirement than its corresponding natural one. Because of their interesting characteristics, MIPs have increasingly attracted researchers’ considerations recently.

Figure 1. Schematic diagram of our process for producing the surface MIP film coated AuNPs and the achieved results in SEM images

Currently, there are two common techniques in MIP technology: particle MIP and membrane MIP. The particle MIP technology requires many steps with expensive equipment, time consuming (in weeks) in fabrication and using strongly toxic chemical solvents harmful to operators and environment. In contrary, the membrane MIP technology is simpler with short time of fabrication (in hours) and in particular the solution is normally distilled water that doesn’t affect template characteristics. Furthermore, measurement methods for membrane MIP outnumber the particle one. In despite of its advantages, membrane MIP technology reveals main limitations of monomer and polymerization conditions, restricted number of bioreceptors generated on the membrane, membrane conduction. Therefore, in this work we propose an applicable technical solution to overcome main limitations of current membrane MIP technology. This is innovative in terms of the new fabrication of membrane MIP, which consisted of a p-aminothiophenol outer layer and an gold nanoparticles (AuNPs) inner layer, on AuNPs-modified screen-printed electrode surface. Our results show that the the ATP SAM on 232

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the AuNPs-modified electrode created the harmonic distribution of AuNPs that helps to generate a single oriented monomer layer. In turn, this layer helps to generate a highly homogeneous membrane of polymer with thickness of only several single layers to easily remove imprinted molecules from polymer matrix to form highly specific cavities, thus increasing the efficiency of the fabrication of artificial MIP bioreceptors (illustrated in Fig. 1 below). REFERENCES 1.

Tin Phan Nguy, Toan Van Phi, Do T. N. Tram, Kasper Eersels, Patrick Wagner and Truong T. N. Lien, Sensors and Actuators B 246, 2017, pp 461–470.

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P074 Development of an impedimetric immunobiosensor for alpha-fetoprotein detection based on disposable screen-printed carbon ink electrode Tram Do Thi Ngoc and Lien Truong Thi Ngoc School of Engineering Physics, Hanoi University of Science and Technology No 1, Dai Co Viet road, Hai Ba Trung dist., Hanoi, Vietnam Email: [email protected]

Orientation of antibodies on solid-state surface has an important role in the performance of immunoassays. The sensitivity of immunoassays depends on antibody presentation that requires the antigen binding sites to be directed toward the solution phase. In ideal case, the Fc part of the immobilized antibody would be substrate facing. However, there could be some other surface orientations including “head-on,” “side-on,” and “lying-on” (see Fig. 1). In this work, we investigate two orientations of the monoclonal AFP antibody, a biomarker for liver cancer diagnosis, on screen-printed carbon ink electrode (SPCE): “end-on” and “side-on”. Fig. 2 shows the scheme, surface Fig. 1: Antibody orientation, morphology and calibration curves of our fabricated dimensions, and important immunosensors. Under optimal conditions, the designed chemical species for targeting immunosensor of the case “end-on” exhibited a wide linear [1]. range from 0.1 ng mL-1 to 10 µg mL-1 with a detection limit of 0.04 ng mL-1 (S/N = 3) for AFP antigen detection. The designed immunosensor also has high selectivity and reproducibility for potential applications in clinical monitoring of AFP antigen.

Fig. 2: SEM images and corresponding scheme as well as calibration curve of A) poly(paminothiophenol/AuNPs/SPCE, B) copolymer of pyrrole and pyrrole-2-carboxylic acid (Py-Pa)/SPCE and C) nanocomposite structure of copolymer Py-Pa and graphene oxide/SPCE. References: Judith A. Scoble; Benjamin W. Muir; Published in: Paul J. Pigram; Biointerphases 2017, 12 (2), 19348630/2017/12(2)/02D301/13.

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P075 Electrochemical behaviours of ZnO nanowires grown on-chip for biosensing applications Nguyen Thi Hong Phuoca, Nguyen Van Toana, Matteo Tonezzerb, Vo Thanh Duoca, Dang Thi Thanh Lea,* a

International Training Institute for Materials Science, Hanoi University of Science and Technology, Addr: No 1 - Dai Co Viet Str. Hanoi, Vietnam. b IMEM-CNR, sede di Trento - FBK, Via alla Cascata 56/C, Povo - Trento, Italy Email: [email protected]

Due to the high surface area and good bio-compatibility of nanostructured ZnO, it finds good utility in biosensor applications. In this study, zinc oxide nanowires (ZnO NWs) were fabricated for electrochemical characterization. ZnO nanowires with average diameter ~ 30-200 nm in hexagonal crystalline structure were grown on working electrode using hydrothermal method at low temperature. Their morphology and structure were analyzed by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). Electrochemical properties of the electrodes with ZnO nanowires were investigated in comparison with Pt electrodes. The results showed that the cyclic voltammogram and electrochemical impedence spectrum (EIS) of ZnO nanowires were stable, but have much bigger resistance comparing to that of Pt electrodes owing to the semiconducting nature of ZnO NWs as shown in Figure 1 (Inset: FE-SEM image of ZnO nanowires and the Randles circuit).

Figure 1. Nyquist plots obtained of bare platinum electrode (black line) and after growing ZnO NWs (red line). Inset: FESEM image of ZnO nanowires and the Randles circuit.

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P076 CO Gas Sensor Based on Quartz Crustal Microbalance Coated with Iron Oxide Nanorods via Co-precipitation Method Nguyen Thanh Vinh1,2, Nguyen Duc Hoang1, Vu Thu Trang1,3, Ngo Xuan Dinh2, Nguyen Van Quy1* 1

International Training Institute for Materials Science, Hanoi University of Science and Technology, No. 1 Dai Co Viet Road, Hai Ba Trung District, Hanoi, Vietnam 2 University of Transport Technology, No. 54, Trieu Khuc, Thanh Xuan District, Hanoi, Vietnam 3 Vietnam Military Medical University, No. 160, Phung Hung Street, Phuc La Ward, Ha Dong District, Hanoi, Vietnam. Email: quy@itims,edu.vn ; [email protected]

Gas sensors based on a quartz crystal microbalance (QCM) coated with iron oxide nanorods were developed for detection of CO at room temperature. Iron oxide nanorods were synthesized by chemical co-precipitation method. The structure, morphology and magnetic properties of assynthesized were characterized by X-Ray Diffraction (XRD), Scanning Electron MicroscopeEnergy Dispersive X-Ray Spectrometry (SEM-EDS). The result showed that the diameter and length of the iron oxide nanorods are about 20 nm and 100 nm, respectively. The strong peaks of Fe and O were indicated in the EDS spectra. The XRD indicated that the product of iron oxide nanorods contain mixture of Fe3O, γ-Fe2O3 and α-Fe2O3. The QCM coated with the iron oxide nanorods gas sensor showed good performance to CO gas. 0.5

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Full Papers

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A Study of Deformed TiO2 Aggregates - Graphene Nanocomposites as Photoanode for Dye Sensitized Solar Cell

Hsueh-Tao Chou 1, 2, *, Cheng-Yueh Chen 2, Chun-Hsin Wang2, Ho-Chun Hsu3, Jing-Hua Lu2 1

Department of Electronic Engineering, National Yunlin University of Science and Technology, Douliou, Yunlin, Taiwan, R.O.C. 2 Graduate School of Electronic Engineering, National Yunlin University of Science and Technology, Douliou, Yunlin, Taiwan, R.O.C. 3 Graduate School of Engineering Science and Technology, National Yunlin University of Science and Technology, Douliou, Yunlin, Taiwan, R.O.C. *Email: [email protected]

Abstract— In this study, deformed TiO2 aggregates (DTA) were mixed with graphene as a composite film for improving

the energy conversion efficiency that applied in the photoanode for dye sensitized solar cells (DSSCs). The composite film (DG film) had been successfully deposited on a transparent conductive oxide substrate using the spray coating system. The morphology and photovoltaic properties of the composite films were observed by using field emission scanning electron microscope (FE-SEM) and solar cell measurement system. The overall thickness of composite layer was about 10μm. The particle size of DTA was about 350 nm. The dye adsorption on composite film was investigated by using UV-Vis spectrophotometer. The energy conversion efficiency was improved by high electron mobility from graphene and high dye adsorption from DTA. DSSC device based on composite film showed a higher photovoltaic conversion efficiency of 3.79% with a working area of 1.0 cm2 under a standard solar light source of 100 mW/cm2. Keywords: Dye sensitized solar cells (DSSCs), Deformed TiO2 Aggregates (DTA), Graphene, and Photoanode

the morphology [5]. The deformed TiO2 aggregate (DTA) was employed in a photoanode due to its large surface area which can improve the dye loading [6].

INTRODUCTION Dye sensitized solar cells (DSSCs) are one of the promising photovoltaic devices for future clean renewable energy due to their flexible, lowcost, colorful, and applying under low illumination. But the DSSCs are the low photoconversion efficiency solar cell. Hence, it is an important topic to improve photo-conversion efficiency in the future. I.

The deformed TiO2 is a three-dimensional mesoporous microsphere that has been demonstrated to effectively increase dye loading as a photoanode [6]. Graphene was mixed with DTA to fabricate the DTA-Graphene (DG) film which is deposited by using spray coating system and the overall thickness is controlled at about 10 μm. DG film do not only enhance the electron transport but also retain the dye loading of DTA. Therefore, this kind of photoanode can effectively improve the photo-conversion efficiency of DSSCs.

Graphene has attracted a lot of attention due to its distinct mechanical, thermal, optical features, outstanding electron mobility (250,000 cm2 V−1 s−1), and large specific surface area (2630 m2/g) [1-2]. Some researchers have reported graphene mixed TiO2 working electrodes in DSSCs and have demonstrated that can effectively suppress unfavorable charge recombination process at TiO2/electrolyte and TiO2/TiO2 interface, leading to the increase of photo-conversion efficiency of DSSCs [3]. Therefore, the excellent characteristics of graphene make it widely apply in energy application.

II.

EXPERIMENTAL

A. Synthesis of deformed TiO2 aggregates For the synthesis of DTA, the DTA solution was composed of 5.5 g of tri-block copolymer (P123, (poly (ethylene glycol)-block-poly (propylene glycol)-block-poly (ethylene glycol), M = 5800)), 15 ml of DI water, 40 ml of anhydrous ethanol, 7 g of urea (purity 99%) and 6 ml of titanium tetraisopropoxide (TTIP, purity 98%). After that, the solution was stirred by using an electromagnetic stirrer for 24 hours. The resulting suspension was transferred into stainless steel autoclave for treating with hydrothermal method at 140℃ for 20 hours. Afterward, the precipitate was obtained by using

Titanium dioxide is applied in photoanode widely because it is easy acquirement, low cost, and non-toxic. In general, the photoanode is composed of TiO2 nanoparticles with an approximate size of 20 nm [4]. Its particle size and consistent shape make the structure of photoanode film compact which lead to the decrease of the dye absorption. Therefore, TiO2 is widely researched, such as the crystalline [4] and 239

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centrifuge, washed with deionized water, dried at 100℃. The dried precipitate was calcined at 500℃ for 3 hours. Then DTA powders with anatase phase have been successfully manufactured [6].

Hanoi, 2017

cells were measured by using the Keithley 2400 source meter under AM 1.5 simulated illumination. Measurement parameters were open-circuit voltage (VOC), short circuit current density (JSC), fill-factor (FF), and energy conversion efficiency (η). The impedance of photoanode was measured by using electrochemical impedance spectroscopy (EIS).

B. Fabrication of DG solution DG solution was composed of 2 g of DTA powders, 6.5 ml of DI water, 0.15 ml of Triton X100, 0.06 ml of acetylacetonate, 0.4 mg of graphene and 1.2 g of polyethylene glycol. Then the DG solution was shaken by using an ultrasonic cleaner for 30 minutes and stirred by using an electromagnetic stirrer for 24 hours.

III.

RESULTS AND DISCUSSION

A. Morphology of photoanode films The inside morphology of DTAs is shown in the TEM image of Figure 2. The DTA particle is composed of TiO2 nanoparticles with a diameter of about 350 nm, where the TiO2 nanoparticles are with stochastic shapes and their diameters are close to 13 nm. There are voids between TiO2 nanoparticles. These voids as the pores of the DTA can increase the dye loading. This result clearly means that DTA has a mesoporous structure, and it has a higher specific surface area for dye loading [6].

C. Fabrication of DG photoanode DG films were deposited on FTO substrate with a thickness of 10 μm by using spray coating system, and then DG films were annealed at a temperature of 450℃ for 30 minutes. The DG working electrodes were immersed in a 0.3Mm of N719 dye for 24 hours. Figure1 shows the schematic structure of working electrode with DG film.

Figure 1. Schematic structure of working electrode with DG film

Figure 2. TEM image of DTA particle.

There are three kinds of films observed by using FE-SEM, including DTA, DG and P25, which provides information such as deposition situation and special morphology. As shown in Figure 3 for the P25 film, P25 nanoparticles were dispersed uniformly on the surface to form a smooth film. The dense structure of P25 nanoparticle with diameters of about 21 nm can effectively provide electron transport path, but this compact structure will sacrifice the space for the absorption of dye molecules.

D. Measurements The morphology of DTA particle was investigated by using transmission electron microscope (TEM). The surface structure of films was observed by using field emission scanning electron microscopy (FE-SEM). The dye absorption of photoanode was measured by using UV-Visible spectrophotometer (JASCO V650). A sandwich structure cell of DSSC was obtained by assembling the photoanode and Pt counter electrode. The electrolyte was implanted into the gap between photoanode and Pt counter electrode. The photovoltaic characteristics of 240

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1μm 100nm

Figure 5. The top-view of FE-SEM image of DG film

Figure 3. The top-view of FE-SEM image of P25 film.

B. Measurements of dye adsorption Figure 6 showed the amount of dye adsorption for different films of DG, DTA and P25. Two main peaks are detected at 370.5 nm and 499 nm. In this graph, we can find that the dye adsorption of DTA films were more than P25. The DG films were the highest dye adsorption. Therefore, graphene was mixed with DTA can increase the N719 dye absorbance.

Figure 4 shown FE-SEM image of DTA films. The DTA film was found with sub-micrometer structure which has lots of pores for getting more dye adsorption. However, its boundary effect and excursive edge contact increase the dark current, thus electrons will easily get lost.

100nm

Figure 4. The top-view of FE-SEM image of DTA film

Then for the DG film, the graphene sheets were mixed in DTA as shown in Figure 5. The excited electrons from dye were quickly transfered to FTO substrate due to high electron mobility of graphene. It can reduce the charge combination and increase the short-current. By this way, the boundary effect of DTA films can be effectively improved.

Figure 6. The dye absorbance curves of DG, DTA and P25 films.

C. Analysis of photovoltaic characteristics Table 1. The characteristics of DSSCs with the same thickness of DG, DTA and P25 films Film DG DTA P25

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JSC (mA/cm2) 8.93 7.51 5.95

VOC (V) 0.68 0.69 0.67

F.F. 0.62 0.58 0.63

η (%) 3.79 3.07 2.54

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Figure 7 and Table 1 showed the photovoltaic properties of DG, DTA and P25. The Jsc of DG film is 8.93 mA/cm2 and the energy conversion efficiency was 3.79%. It proved that the photoconversion efficiency of DSSC was increased from 3.07% to 3.79% for DG photoanode.

Figure 8. Nyquist plots of DG, DTA, P25 photoanode.

CONCLUSION Appropriately adding graphene into DTA as the DG film can increase the dye loading, and the short-circuit current (JSC) and energy conversion efficiency (η) of the DSSC is increased from 5.95 to 8.93 and from 2.54% to 3.79%, respectively. We conclude that suitable amount of graphene mixing in DTA can decrease the resistance at the interface of TiO2/dye/electrolyte owing to the high electron mobility of graphene.

Figure 7. J-V curves of DSSCs with the same thickness of DG, DTA, P25 photoanode.

D. Analysis of Electrochemical properties A typical Nyquist plot of DSSCs was composed of three semicircles. The first semicircle displayed the charge transfer impedance at the Pt/electrolyte interface (R1). The second semicircle was the charge transfer rates at TiO2/dye/electrolyte interfaces (R2) [7]. Figure 8 and Table 2 showed Nyquist plots and EIS parameters of DG, DTA, and P25 photoanodes, respectively. DTA film had high dye loading, but its adverse interfacial structure which caused the highest R2. The R2 of P25 film was lower than DTA film due to its compact and smooth surface, which will make the electron transfer easily. However, the lowest R2 was DG film, because the graphene in DG film acted as a bridge between DTA powders and its high electron mobility made the electron transfer more quickly than the electron in P25 film.

ACKNOWLEDGMENT Ministry of Science and Technology, Republic of China have supported this study, under the contract MOST 106-2221-E-224 -040. REFERENCES [1]

[2]

[3]

Table 2. EIS results of DG, DTA, P25 photoanode photoanode DG DTA P25

RS(Ω) 13.68 13.71 12.98

R1(Ω) 2.85 1.43 2.61

R2(Ω) 0.78 3.366 1.02

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[5]

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Umer Mehmood, Shakeel Ahmed, Ibnelwaleed A. Hussein, “Improving the efficiency of dye sensitized solar cells by TiO2-graphene nanocomposite photoanode,” Photonics and Nanostructures Fundamentals and Applications, vol. 16, pp. 34-42, August 2015. Hui Ding, Ji-Tao Chen, Xiao-Ping Hud, Zhao-Fu Du, Yue-Xiu Qiu, Dong-Liang Zhao, “Reduction of graphene oxide at room temperature with vitamin C for RGO–TiO2 photoanodes in dye-sensitized solar cell,” Thin Solid Films, vol. 584, pp. 29-36, June 2015, Jie Liu, Xiao Fu, Da-Peng Cao, Le Mao, Juan Wang, Dan-Hua Mu, Bao-Xiu Mi, Bao-Min Zhao, Zhi-Qiang Gao, “Stacked graphene–TiO2 photoanode via electrospray deposition for highly efficient dyesensitized solar cells,” Organic Electronics., vol. 2, pp. 158-163, August 2015. Behzad RezaeiIsmaeil, Mohammadi, Ali AsgharEnsafi, Mohammad MohsenMomeni, “Enhanced efficiency of DSSC through ACelectrophoretic hybridization of TiO2 nanoparticle and nanotube,” Electrochimica Acta, vol. 247, pp. 410419. Sanjivani V. Umale, Sneh N. Tambat, Vediappan Sudhakar, Sharad M. Sontakke, Kothandam Krishnamoorthy, “Fabrication, characterization and

The 12th Asian Conference on Chemical Sensors (ACCS2017) comparison of DSSC using anatase TiO2 synthesized by various methods” Advanced Powder Technology, Available online 2, in press, September 2017. [6] H.-T. Chou, K.-C. Tseng, and H.-C. Hsu, “Fabrication of deformed TiO2 aggregate as photoanode in dyesensitized solar cells,” IEEE Journal of Photovoltaics, vol. 6, pp. 211-216, 2016. [7] Yu-Chao Wang, Chun-Pei Cho, “Application of TiO2graphene nanocomposites to photoanode of dyesensitized solar cell” Journal of Photochemistry and Photobiology A: Chemistry, vol. 332, pp.1-9, January 2017

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Investigation of the Temperature Effect for the Chloride Ion Sensor Tong-Yu Wu1,*, Shi-Chang Tseng1, Jung-Chuan Chou2,3, Yi-Hung Liao4, Chih-Hsien Lai2,3, Siao-Jie Yan3, You-Xiang Wu3, Cian-Yi Wu3 and Ting-Wei Tseng2 1

Graduate School of Mechanical Engineering, National Yunlin University of Science and Technology, Addr: No. 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan, R.O.C. 2 Department of Electronic Engineering, National Yunlin University of Science and Technology, Addr: No. 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan, R.O.C. 3 Graduate School of Electronic Engineering, National Yunlin University of Science and Technology, Addr: No. 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan, R.O.C. 4 Department of Information and Electronic Commerce Management, TransWorld University, Addr: No.1221 Zhennan Road, Douliou, Yunlin 640, Taiwan R.O.C. *Corresponding author: [email protected]

Abstract: In this study, the different temperatures of the solutions were investigated at different solution

temperatures for the chloride ion sensor. The temperature coefficient is an important parameter for ion sensing devices. The screen printing system and radio frequency (R. F.) sputtering system were used to prepare the arrayed flexible ruthenium dioxide (RuO2) hydrogen (H+) ion sensor. The weight ratio of the poly (vinyl chloride) (PVC), bis (2ethylhexyl) sebacate (DOS), chloride ionophore III (ETH9033) and tridodecylmethy-lammonium chloride (TDDMACl) was 33: 66: 2: 10 (wt%), and which was used to prepare the arrayed flexible chloride ion sensor. We used the voltagetime measuring system, electrochemical impedance spectroscopy (EIS) and temperature controller system to investigate the temperature effects of the arrayed flexible chloride ion sensor. The temperature controller was used to control the solution temperature, which was from 5±0.2 ℃ to 50±0.2 ℃. The sensitivities of arrayed flexible chloride ion sensors were increased by the thermal convection from 5 ℃ to 35 ℃. According to the experimental result, the temperature coefficient of the sensitivity (TCS) of the arrayed flexible chloride ion sensor was approximately 0.681 mV/pCl oC at 5 oC to 35 oC. Keywords: Ruthenium dioxide, chloride ion sensor, temperature coefficient

INTRODUCTION L. Manjakkal et al. [1] used Ag/Pd thick film paste (ESL 9695) and two commercial RuO2 pastes (ESL 3913 and ESL 3914) to construct the sensing electrode on the alumina substrate (96% Al2O3) by screen printing technology and sintering technology. They employed the scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) to investigate the sensing characteristic of RuO2 pH sensor. I.

The EIS analysis of the pH sensor was carried out in the frequency range 10 mHz-2 MHz from pH 2 to pH 12 test solutions. B. Xu et al. [2], the RuO2/ multiwall carbon nanotubes (MWCNTs) electrode was prepared by magnetron sputtering deposition. They investigated the sensitivities, hysteresis voltages, ion selective coefficients and electrochemical impedance characteristics. In our previous research [3], the electrochemical impedance characteristics of the different structure sensing films were investigated. The frequency range of EIS was set from 100 kHz to 100 mHz and alternating current (AC) voltage of EIS was set at 50 mV. The equivalent circuit was consisted 244

of the electron transfer resistance (Ret), solution resistor (Rs) and double layer capacitor (Cdl). A. Sardarinejad et al. [4] investigated the temperature effects on the sensing performance of the RuO2 pH sensor, and they found the sensitivity was increased when the solution temperature raised. The temperature coefficient of the sensitivity (TCS) is important, which could be compensated for variations and evaluated the effect of temperature on the response voltage pH sensor. In our previous research [5], the hydrogenated amorphous silicon (a-Si:H) sensing film was used to investigate the sensitivity variation with different solution temperatures. They calculated the temperature coefficient of the a-Si:H ionsensitive field effect transistor (ISFET) with different temperature pH 1-pH 7 solution from 25 ºC to 65 ºC. J. L. Chiang et al. [6] used R. F. sputtering to fabricate the aluminum nitride (AlN) hydrogen ion sensitive field effect transistor devices, the temperature effect of AlN pH sensing devices was investigated. In our previous research [7], the sensitivity and hysteresis of the Sentron 1090 Al2O3 pH-ISFET sensing device were investigated. The sensitivity of sentron 1090 Al2O3 pH-ISFET sensing device was 53.23

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mV/pH at 25 ºC. The increasing solution temperature would decrease viscosity and increase the mobility of the ions in solution. The amounts of ions in solution due to dissociation of molecules were increased with the increasing solution temperature. The conductivity of a solution is dependent on these factors so the increasing temperature will lead to an increase in its conductivity [8]. In our previous research [9], we used the arrayed flexible chloride ion sensor to investigate the sensitivity at static and dynamic states, and it could be found the sensitivity was increased with the incremental flow rate of the solutions. In addition to the sodium hypochlorite (NaClO) solution, it was also applied to detect the chloride ion of the swimming pool water. However, the temperature effect could affect the response voltage variation with different chloride concentration. Thus, we investigated TCS of the arrayed flexible chloride ion sensor, which could be compensated for variations and evaluated the effect of temperature on the response voltage chloride ion sensor.

II.

EXPERIMENTAL

A. Fabrication of the arrayed flexible chloride ion sensor The screen-printed system and R. F. sputtering system was used to prepare the RuO2 pH sensor. The weight ratio of the PVC, DOS, ETH9033 and TDDMACl was 33: 66: 2: 10 (wt%) [9-10], and it was used to drop on the sensing windows of arrayed flexible chloride ion sensor. The arrayed flexible pH sensor was dried at room temperature 25 oC for 4 days. B. Measurement of the temperature effects We investigated the variations of sensitivity, electron transfer resistances (Ret) and solution resistance (Rs) and double layer capacitor (Cdl) at different solution temperatures from 5±0.2 ºC to 50±0.2 ºC. The voltage-time measuring system (V-T measuring system), electrochemical impedance spectroscopy (EIS), cooling circulating water bath and thermometer were used to study the sensitivities with different temperatures from 5 ± 0.2 ºC to 50±0.2 ºC. The voltage-time measuring system was composed of 8-channel readout circuit with instrumentation amplifiers (LT1167), National Instruments data acquisition (DAQ) card, power supply, computer and analysis software 245

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(model: LabVIEW 2011). We used the electrochemical impedance spectroscopy (EIS; BioLogic SP 150, Aurora Biotech Inc., France) to investigate Ret, Rs and Cdl of the sensing membrane in different concentrations of 1 M NaCl solution at different solution temperatures from 5 ºC to 50 ºC. The three electrodes of electrochemical impedance spectroscopy (EIS) system were counter electrode (platinum electrode), reference electrode (silver / silver chloride electrode) and working electrode (RuO2/chloride ion sensing film). The EIS measuring system was set in the frequency range of sinusoidal excitation signal from 10 kHz to 100 mHz, and the amplitude of voltage was 0.7 mV. The cooling circulating water bath was closed loop control, which could control exactly the solution temperature. The solution temperatures were controlled from 5±0.2 ºC to 50±0.2 ºC by the cooling circulating water bath. III.

RESULTS AND DISCUSSION

A. Investigation of the temperature effects We used the temperature controlled system to maintain temperatures of NaCl solution from 5± 0.2 ºC to 50±0.2 ºC, and the experimental results of average sensitivity and linearity with different temperatures were shown in Fig. 1. The average sensitivities and linearities were 18.682±0.060 mV/pCl, 27.697±0.018 mV/pCl, 29.136±0.029 mV/pCl, 36.779±0.013 mV/pCl, 38.379±0.096 mV/pCl, 39.803±1.317 mV/pCl, 43.696±0.020 mV/pCl, 41.446±1.558 mV/pCl, 33.253±0.132 mV/pCl and 22.608±0.020 mV/pCl for different NaCl solution temperatures from 5 ºC to 50 ºC, respectively. We used 1 M NaCl solution to investigate the Ret for different solution temperatures from 10 ºC to 50 ºC. From Fig. 2 and Table I, the Ret and Rs was decreased with the increasing solution temperatures form 10 ºC to 35 ºC. The Ret and Rs were 293.44 kΩ and 10.11 kΩ in 1 M NaCl solution at 10 ºC, because the electron transfer could be affected at the lowest solution temperature. However, the smallest Ret and Rs were 70.05 kΩ and 8.63 kΩ at 35 ºC. According to the experimental result, when temperature of the NaCl solution rose, thermal convection was produced with different chloride ion concentrations from 10 -5 M to 1 M NaCl solution. The thermal convection promoted the chloride ion moving strongly, which led to decrease in the thickness of Nernst diffusion layer. The amounts of chloride ion in NaCl solution were

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70

Sensitivity (mV/pCl)

1.0 60 0.9 50

0.8

40

0.7

30

0.6

20

0.5

10

Linearity

increased when the solution temperature was increased. It could be attributed to the dissociation of molecules was increased with the higher temperature [8, 11]. It also indicated that diffusion rate would be increased so that the sensitivities were risen by the thermal convection from 5 ºC to 35 ºC. When the solution temperature was higher than 35 ºC, it could be decrease the adhesion between the chloride ion sensing film and sensing windows. Thus the sensitivity was decreased when temperature was higher than 35 ºC. The TCS of the arrayed flexible chloride ion sensor was approximately 0.681 mV/pCl ºC at 5 ºC to 35 ºC.

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0.4 0

5

10 15 20 25 30 35 40 45 50 o

Temperature ( C)

Figure 1. The measurement results of the different temperatures for NaCl solutions for the arrayed flexible chloride ion sensor. TABLE Ⅰ THE FITTING RESULTS OF Ret, Rs AND Cdl IN 1 M NaCl SOLUTION AT THE DIFFERENT SOLUTION TEMPERATURES.

Solution temperature (ºC)

Electron transfer resistance Ret (kΩ)

Solution resistance Rs (kΩ)

Double layer capacitor Cdl (F)

10

293.44

10.11

3.00E-10

20

190.12

10.52

5.79E-10

30

112.66

19.90

7.91E-10

35

70.05

8.63

7.98E-10

40

77.85

17.59

7.85E-10

50

111.69

17.78

6.70E-10

IV.

200k

Ret Rs Cdl

-Im(Z)/Ohm

150k

10 oC 20 oC

100k

30 oC 35 oC

50k

0

40 oC 50 oC

0

50k

100k

150k

200k

250k

Re(Z)/Ohm

Figure 2. The electrochemical impedance of the different solution temperatures between 10 ºC and 50 ºC.

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CONCLUSION

The sensitivities were risen by the thermal convection from 5 ºC to 35 ºC. The best average sensitivity was 43.696±0.020 mV/pCl at 35 ºC. When the solution temperature was higher than 35 ºC, it could be decrease the adhesion between the chloride ion sensing film and sensing windows. Thus the sensitivity was decreased when temperature was higher than 35 ºC. The advantages of the arrayed flexible chloride ion sensor were fast response, good specificity, good stability and better sensing characteristic at 35 ºC. According to the experimental result, the TCS of the arrayed flexible chloride ion sensor was approximately 0.681 mV/pCl ºC at 5 ºC to 35 ºC.

The 12th Asian Conference on Chemical Sensors (ACCS2017) ACKNOWLEDGMENTS

This study has been supported by Ministry of Science and Technology, Republic of China, under the contracts MOST 106-2221-E-224-023 and MOST 106-2221-E-224-047. REFERENCES L. Manjakkal, E. Djurdjic, K. Cvejin, J. Kulawik, K. Zaraska, D. Szwagierczak, Electrochemical impedance spectroscopic analysis of RuO2 based thick film pH sensors, Electrochim. Acta, 168 (2015) 246-255. [2] B. Xu, W. D. Zhang, Modification of vertically aligned carbon nanotubes with RuO2 for a solidstate pH sensor, Electrochim. Acta, 55 (2010) 28592864. [3] J. C. Chou, J. S. Chen, M. S. Huang, Y. H. Liao, C. H. Lai, T. Y. Wu, S. J. Yan, The characteristic analysis of IGZO/Al pH sensor and glucose biosensor in static and dynamic measurements, IEEE Sens. J., 16 (2016) 8509-8516. [4] A. Sardarinejad, D. K. Maurya, M. Khaled, K. Alameh, Temperature effect on the performance of RuO2 thin-film pH sensor, Sens. Actuators, A, 233 (2015) 414-421. [5] J. C. Chou, Y. F. Wang, J. S. Lin, Temperature effect of a-Si:H pH-ISFET, Sens. Actuators, B, 62 (2000) 92–96. [6] J. L. Chiang, J. C. Chou, Study on light and temperature properties of AlN pH-ion-sensitive field-effect transistor devices, Jpn. J. Appl. Phys., 44 (2005) 4831-4837. [7] J. C. Chou, C. Y. Weng, Sensitivity and hysteresis effect in Al2O3 gate pH-ISFET, Mater. Chem. Phys., 71 (2001) 120-124. [8] J. J. Barron, C. Ashton, The effect of temperature on conductivity measurement, TSP-07. https://www.reagecon.com/pdf/technicalpapers/Effe ct_of_Temperature_TSP-07_Issue3.pdf [9] S. C. Tseng, T. Y. Wu, J. C. Chou, Y. H. Liao, C. H. Lai, J. S. Chen, M. S. Huang, Research of non-ideal effect and dynamic measurement of the flexible arrayed chlorine ion sensor, IEEE Sens. J., 16 (2016) 4683-4690. [10] J. C. Chou, G. C. Ye, D. G. Wu, C. C. Chen, Fabrication of the array chlorine ion sensor based on microfluidic device framework, Solid-State Electron., 77 (2012) 87-92. [11] J. Chen, J. Liu, G. Zhang, Z. He, Study on the strength of sea sand concrete introduced by chloride ion, Proc. The 2011 Second International Conference on Mechanic Automation and Control Engineering (MACE’ 2011), Hohhot, China, 2011. [1]

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3D FEM simulation of the effects of humidity on response of SAW sensor based on ZnO/IDTs/AlN/Si structure Hai-Ha Nguyen*1, Ngoc-Tuan Truong2, Quang-Huy Do1, Hoang-Nam Nguyen1, Hang-Phuong Nguyen1, Si-Hong Hoang*1 1

School of Electrical Engineering, Hanoi University of Science and Technology, No 1 - Dai Co Viet Str. Hanoi, Vietnam 2 Hung Yen University of Technology and Education *Corresponding author: [email protected]; [email protected]

Abstract: This paper shows relationship between Surface Acoustic Wave (SAW) frequency response and variation of mass density and electrical conductivity of humidity sensing layer. The SAW sensor structure is ZnO/IDTs/AlN/Si (IDT - Interdigital Transducer). The simulation method is 3D Finite Element Method (FEM). The simulation results show that there is a decrease in resonant frequency from 126.3 MHz to 121.0 MHz corresponding to an increase of the mass density of ZnO from 5675 kg/m3 to 5685 kg/m3, and a decrease in resonant frequency from 126.3 MHz to 124.6 MHz corresponding to an increase of the conductivity of ZnO from 1 S/m to 104 S/m. Keywords: SAW sensor, mass density, electrical conductivity, sensitive layer

I. INTRODUCTION Surface acoustic wave sensors are favored for chemical sensing application because of their small size, good response time, diverse sensor coatings, inexpensive cost, high sensitivity for most of gasses and wireless ability [1] [2] [3] [4]. In the context of chemical and gas sensor research, humidity of air flow has much influence on experimental results; therefore a deeply studying in relative humidity becomes a very important task. There are many studies on SAW humidity sensor but most of them have not yet pointed out the nature of relationship between relative humidity and humidity sensitive layer. Particularly, a group at the University of Ulsan built a 2D model of SAW sensor to simulate ZnO humidity sensing layer [5]. Another group at the Chinese Academy of Sciences conducted research on ZnO(11 2 0)/R-Sapphire structure through a 3D analysis [6]. However, they only considered water layer induced by adsorption of water vapor as a mass layer. Other groups simulated humidity sensor based on polymer sensing layer [7[8] [9]. Accordingly, this research analyzed the influence of humidity on ZnO/IDTs/AlN/Si multilayer structure based on changing characteristics of ZnO humidity sensing in mass density and electrical conductivity. The simulation method is 3D FEM to improve the accuracy of result.

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II. THEORY A. Selection of structure and geometric parameters for SAW sensor The SAW sensor structure illustrates in figure 1. In this structure, AlN thin film is piezoelectric layer on Si substrate, and ZnO thin film is humidity sensing layer. ZnO was chosen because it is a humidity sensing layer which has been used most commonly and AlN thin film has good piezoelectric properties, high acoustic velocity, superior temperature, chemical stability [2] [6].

Figure 1. Structure of SAW sensor. Table 1. The value of geometric parameters used in simulation Parameter The length of SAW sensor, L [mm] The width of SAW sensor, W [mm] The thickness of the Si substrate, h1 [μm]

Value 8 3 500

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The thickness of the AlN substrate, h2 [μm] The thickness of the ZnO substrate, h3 [nm] The period of electrodes, d [μm] The IDT – IDT gap, D [mm] The length of IDT [mm] The number of IDT input/output, [pair]

0.5

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0  kc v (3) 1  kc v /  v Therefore, when the concentration of the vapor in the gas phase is increased corresponding to the relative humidity of gas is increased, the density of sensing layer is increased. Secondly, the density change Δρ of sensing layer caused the change in frequency response of the SAW resonant with a thickness of h, the density of ρ as follows [12]: 4    (4) f  (k1  k 2 )f 02  h  k 2f 02  h 2 ( ) v0   2 where k1 and k2 are the coupling constants determined by the different displacement components of SAW in the substrate; f0 is the unperturbed oscillating frequency of the SAW oscillator, which is determined by the propagation velocity of SAW and the period of the IDTs fabricated on the surface of the piezoelectric substrate; μ and λ are the shear modulus and Lame constant of the layer; v0 is the unperturbed velocity of SAW in the piezoelectric substrate. The first term in Equation (2) represents the frequency change caused by mass loading and the second term depends on the acoustic wave coupled into the layer. Because the layer formed by adsorbed gas is very thin, it can be seen as a simple mass load attached to the surface of the SAW device. Thus equation (4) can be simplified as (5) f  (k1  k 2 )f 02  h  (c v ) 

300 10 5 1 25

Figure 2. Geometric parameters of SAW sensor in detail. Figure 2 shows geometric parameters in detail and geometric values are shown in table 1. In this paper, the operation of the SAW humidity sensor is based on the resonant frequency shift when mass density and electrical conductivity of sensing layer material are changed[10]. Therefore, section II-B and II-C provide some qualitative explanations about this view. B.

Effect of relative humidity on mass density of sensing layer Firstly, the interaction between the vapor and the sensing layer can be explained as a solubility interaction where the vapor is a solute and the sensing layer is the solvent. The mass density ρ of a metal oxide thin film is taken as a function of the concentration of humidity sorbed, C as shown in Equation (1) [11]: ρ(c) = ρ(0)+ CM/(1+ CU) (1) Where, U and M are specific volume and molecular weight of the sorption species, respectively. C and U in equation 2 can be expressed as: (2) c = kCv/M ; U = M/v Where Cv is the vapor concentration, v is the density of the vapor. The k is the partition coefficient. Then, substituting equation (2) into equation (1), the polymer thickness and density depending on vapor adsorption can be described as: 249

Equation (5) means that the sensor output is proportional to the quantity of the mass loaded on the surface of a SAW device, and it is the theoretical basis for the detection of SAW sensors. Hence, the resonant frequency shift is inversely proportional to the mass density of humidity sensing layer and relative humidity. C.

Effect of relative humidity on electrical conductivity of sensing layer The relationship between conductivity ZnO thin film and relative humidity is shown as a formula [2]: 𝐻2 0 + 𝑂0 + 2𝑍𝑛𝑍𝑛 = 2(𝑂𝐻 − 𝑍𝑛) + 𝑉 00 + 2𝑒 − 00

(6)

where 𝑂0 is the lattice oxygen and 𝑉 is the vacancy created at the oxygen site. Thus, the surface conductivity of the sensing film is increased by increasing the number of free electrons with increasing relative humidity. The relation between

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the conductivity of sensing layer and SAW velocity is given by [2]: (7) v k2 1  2 v0 2 1  (v0CS /  S ) where 𝑘 2 is the electromechanical coupling factor for substrate, 𝜎𝑠 is the sheet conductivity of the sensing film, and Cs is the total of the dielectric constants of the substrate in the vacuum. Hence, as shown in reaction equations (6) and (7), the increase in the conductivity of the sensing layer with increased relative humidity decreases SAW velocity. III. RESULTS AND DISCUSSION This section shows not only simulation results but also relationships among resonant frequency and ZnO’s features in density and conductivity. First of all, some results in 3D simulation are shown here. After meshing process, SAW structure is illustrated in figure 3.

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structure was excited by a harmonic electric signal; therefore color of input ITDs is brighter than output IDTs. The output signal was given as potential difference on the electrodes of the detector IDT structure.

Figure 4. Distribution of deformation magnitude in μm unit when input IDTs were excited by a harmonic electric signal. Secondly, frequency response of SAW sensor is shown in figure 5. This is a result when ZnO’s initialization value in density and conductivity are respective 5675 kg/m3 and 104 S/m.

Figure 5. The frequency response of humidity SAW sensor with ZnO’s initialization features in density and conductivity.

Figure 3. ZnO/IDTs/AlN/Si structure after meshing process. The blue areas have fewer elements than the white ones. There are two reasons to explain this view. The first reason is that surface acoustic waves only spread on piezoelectric surface and the strongest propagation is at delay line area. The second reason is that meshing with more elements in the delay line area and less elements in the rest would reduce complex calculation for the whole simulation process. Figure 4 highlights the distribution of deformation magnitude at the end of simulation in μm unit. This 3D result represents an ideal structure and does not take into account deformations caused by manufacturing processes. The waveguide which is oriented between the two IDT transmitters parallels the piezoelectric layer surface. The input IDT 250

In figure 5, the point which has maximum magnitude is resonant point. The center frequency is 124.6 MHz. So the SAW velocity is computed by v  f .  f .4d  v  124, 6.40  4984 m / s This velocity demonstrates the correctness of simulation compared to 5030 m/s of experiment [13] (error is approximate 0.9%). Lastly, this section shows the influence of relative humidity on center frequency. However, this study only acts at simulation level, the change of relative humidity is shown correspondingly by the change of mass density and conductivity of ZnO. The results of two experiments are compared with the theory presented in section II-B and II-C. The first experiment is that simulation has no consideration to conductivity factor, and the second

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one is that simulation has no consideration to mass density factor.

Figure 6. The resonant frequencies vary with density values of ZnO. Figure 6 illustrates the relationship between resonant frequency and ZnO’s mass density in the first experiment. When the density of ZnO increases from 5675 kg/m3 to 5685 kg/m3, the resonant frequency goes down from 126.3 MHz to 121 MHz. In detail, center frequency fast decreases at 5675 kg/m3, 5678 kg/m3 and 5680 kg/m3 points and slowly decreases at 5682 kg/m3, 5683 kg/m3 and 5685 kg/m3 points.

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These results which are shown in figure 6 and figure 7 demonstrate that when mass density and conductivity increase, resonant frequency of SAW sensor decrease respectively. This view is suitable with theory [2]. IV. CONCLUSION This paper shows an accuracy definiteness between theory and 3D simulation results. Resonant frequency of SAW sensor reduces when mass density and conductivity increase. The resonant frequency shifts are 5.3 MHz corresponding to an increase of ZnO density from 5675 kg/m3 to 5685 kg/m3 and 1.7 MHz corresponding to an increase of ZnO conductivity from 1 (S/m) to 104 (S/m). However, the results have not yet researched about detail correspondence value between mass density and conductivity of ZnO and relative humidity. This issue will be studied in future researches. ACKNOWLEDGMENT This research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 103.02-2014.47. REFERENCES [1]

J. W. Grate, S. J. Martin, and R. M. White, “Jay W. Grate,” vol. 65, no. 22, 1993.

[2]

H. S. Hong, D. T. Phan, and G. S. Chung, “Highsensitivity humidity sensors with ZnO nanorods based two-port surface acoustic wave delay line,” Sensors Actuators, B Chem., vol. 171–172, no. 1, pp. 1283–1287, 2012.

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J. Devkota, P. R. Ohodnicki, and D. W. Greve, “SAW sensors for chemical vapors and gases,” Sensors (Switzerland), vol. 17, no. 4, pp. 13–15, 2017.

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B. Drafts, “Acoustic wave technology sensors,” IEEE Trans. Microw. Theory Tech., vol. 49, no. 4 II, pp. 795–802, 2001.

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“FEM MODELING SAW HUMIDITY SENSOR BASED ON ZNO / IDTS / ALN / SI STRUCTURES D . T . Phan and G . S . Chung,” pp. 1160–1163, 2011.

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X.-D. Lan, S.-Y. Zhang, L. Fan, and Y. Wang, “Simulation of SAW Humidity Sensors Based on ( 11 2 ¯ 0 ) ZnO/R-Sapphire Structures,” Sensors, vol. 16, no. 11, p. 1112, 2016.

Figure 7. The resonant frequencies vary with conductivity values of ZnO. Results in the second experiment are shown in figure 7. This paper simulates a conductivity increase of 10 times per step. Detail values of conductivity factor are 1 S/m, 10 S/m, 102 S/m, 103 S/m and 104 S/m corresponding with detail center frequencies are 126.3 MHz, 125.9 MHz, 125.6 MHz, 124.9 MHz and 124.6 MHz. Conductivity increases from 1 S/m to 103 S/m corresponding fast reduction of center frequency is from 126.3 MHz to 124.9 MHz, while it is slowdown from 103 S/m to 104 S/m. 251

The 12th Asian Conference on Chemical Sensors (ACCS2017) [7] T. M. Ha, N. T. Truyen, N. H. Phuong, N. N. Hoang, H. S. Hong, “Research on effect of humidity on frequency response of SAW filter using ZnO / AlN / Si structure,” in The 9th Regional Conference on Electrical and Electronics Engineering, November 17-18, 2016, Hanoi, Vietnam pp. 422–426, 2016. [8] U. C. Kaletta and C. Wenger, “FEM simulation of Rayleigh waves for CMOS compatible SAW devices based on AlN/SiO₂/Si(100).,” Ultrasonics, vol. 54, no. 1, pp. 291–5, 2014. [9]

Y. G. Zhao, M. Liu, D. M. Li, J. J. Li, and J. Bin Niu, “FEM modeling of SAW organic vapor sensors,” Sensors Actuators, A Phys., vol. 154, no. 1, pp. 30– 34, 2009.

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H. Wohltjen, “Mechanism of operation and design considerations for surface acoustic wave device vapour sensors,” Sensors and Actuators, vol. 5, no. 4, pp. 307–325, 1984.

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[11]

S. He, W. Wang, S. Li, and M. Liu, “Advances in polymer-coated surface acoustic wave gas sensor,” 2011 16th Int. Solid-State Sensors, Actuators Microsystems Conf. TRANSDUCERS’11, pp. 1144– 1147, 2011.

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J. Liu and Y. Lu, “Response mechanism for surface acoustic wave gas sensors based on surfaceadsorption,” Sensors (Basel)., vol. 14, no. 4, pp. 6844–6853, 2014.

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H. Hong and G. Chung, “Surface acoustic wave humidity sensor based on polycrystalline AlN thin film coated with sol–gel derived nanocrystalline zinc oxide film,” Sensors Actuators B Chem., vol. 148, no. 2, pp. 347–352, Jul. 2010.

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Potentiometric Ascorbic Acid Determination by MBs-Ascorbate Oxidase/GO/IGZO/Al Membrane Assembled on Flexible Sensor Array You-Xiang Wua, Jung-Chuan Choua, b, *, Yi-Hung Liaoc, Chih-Hsien Laia, b, Siao-Jie Yana, and Cian-Yi Wua a

Graduate School of Electronic Engineering, National Yunlin University of Science and Technology, Addr: No. 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan, R.O.C b Department of Electronic Engineering, National Yunlin University of Science and Technology, Addr: No. 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan, R.O.C. c Department of Information and Electronic Commerce Management, TransWorld University, Addr: No.1221 Zhennan Road, Douliou, Yunlin 640, Taiwan R.O.C. *Corresponding author: [email protected]

Abstract: Magnetic beads (MBs) have been widely applied to biosensor because MBs can bind specific moieties for biomolecules and particular biomolecules. In this study, we propose an ascorbic acid biosensor based on the MBsascorbate oxidase/graphene oxide (GO)/ indium gallium zinc oxide (IGZO)/aluminum (Al) sensing membrane. The IGZO layer was served as the sensing membrane because IGZO possesse the high chemical stability. Moreover, we deposited the GO layer onto the IGZO sensing membrane to increase the specific surface area and to enhance the enzyme immobilization. MBs were mixed with ascorbate oxidase solution, and then were immobilized onto the GO layer by covalent binding. To obtain the optimal ratio of MBs-ascorbate oxidase, we investigated the effect of MBs concentration on the average sensitivity of the biosensor. We measured the MBs-ascorbate oxidase/GO/IGZO/Al ascorbic acid biosensor through a voltage-time (V-T) measurement system, and the linear range of L-ascorbic acid concentrations was from 0.003 to 2 mM. According to experimental results, we observed the biosensor had good average sensitivity, linearity and short response time. Besides, we investigated the stability and selectivity of the biosensor by drift test and interfering test. Keywords: Magnetic beads, Ascorbic acid, Graphene oxide, IGZO

INTRODUCTION It has been known that ascorbic acid is also called Vitamin C. The human health is related to ascorbic acid, which was used as antioxidant to inhibit carcinogenesis, prevention of scurvy and composition of collagen. It can be known that ascorbic acid is essential for human. Therefore, the mortality can be decreased by controlling ascorbic acid, and it is important to detect the concentration of ascorbic acid in human body [1]. We developed a MBs-Ascorbate Oxidase/GO/IGZO/Al ascorbic acid biosensor to measure the concentration of ascorbic acid solution. The mechanism of detection was based on the site binding model which was proposed by Yate et al [2]. Therefore, we utilized oxidoreductase (ascorbate oxidase) to fabricate the catalytic layer. The ascorbate oxidase catalyzes ascorbic acid to produce hydrogen ions, and the hydrogen ions will be adsorbed onto the sensing membrane. Besides, because the graphene oxide (GO) possessed high specific surface area and many oxygen-containing functional groups [3], I.

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which was modified onto the IGZO sensing membrane in order to make the sensing membrane adsorb more hydrogen ions. Further, due to the magnetic beads (MBs) could be used as supports or carriers in biosensor [4]. The MBs were mixed with ascorbate oxidase in order to bind the enzyme by covalent bonding [5-6]. The reference electrodes and the conductive wires were fabricated on the polyethylene terephthalate (PET) substrate by screen printing technology. This method of fabrication could solve the problem of reference electrode’s size, and it also could decrease cost. Therefore, in this study, the biosensor possessed flexibility, which could be applied in wearable electronics in vitro diagnostics and electronic skin. Besides, the biosensor possessed six sensing windows, which could obtain the response voltages at the same time. Consequently, we could find error data at the first time to ensure that the biosensor has high reliability and accuracy.

The 12th Asian Conference on Chemical Sensors (ACCS2017) II.

EXPERIMENTAL

A. Fabrication of IGZO/Al Membrane First, the PET substrate dimension was 3 cm x 4 cm. The PET substrate was cleaned by nitrogen gun, alcohol and deionized (D. I.) water. Finally, the oven was used to remove steam of PET substrate. Then, the cleaning steps of PET substrate were finished. We adopted the screen printing technology to fabricate silver paste on the PET substrate, which was used as reference electrodes and conductive wires. Next, the thermal evaporation system was adopted to deposit aluminum (Al) membrane onto the extremity of conductive wires. Then, we adopted radio frequency (R. F.) sputtering system to deposit IGZO membrane onto the Al membrane at 3 mtorr working pressure, and which power and flow rates parameters were set 40 W and Ar/O2 of 16/2 (sccm), respectively. Lastly, we also adopted the screen printing technology to print epoxy which used as insulation layer, and defined size of sensing window by mask of screen. Therefore, arrayed IGZO/Al membrane was successfully fabricated. B. MBs-Ascorbate Oxidase Solution First, we prepare the ascorbate oxidase solution, which contain 200 μl phosphate buffered saline (PBS) solution (50 mM) and 250 U ascorbate oxidase. In order to fabricate MBsAscorbate oxidase solution, the ascorbate oxidase solution mixed with MBs. The 400 μl MBs solution was sucked out by micropipette, and we separated the MBs and maintenance liquid by DynaMag magnet device. Next, the MBs were cleaned with 1 ml PBS solution for 3 times each 10 minutes. The 10 mg N-(3Dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (EDC) were mixed with 1 ml PBS which was shaked by stirrer for 10 minutes. We used 100 μl EDC solution as carboxyl activating agent mixed with MBs which were shaked by stirrer for 30 min. Then, we separated the MBs and EDC solution by DynaMag magnet device. Finally, we mixed the ascorbate oxidase solution and MBs to fabricate the ascorbate oxidase-MBs solution, and we stored the ascorbate oxidase-MBs in a refrigerator at 4 °C for one day, the ascorbate oxidase-MBs solution was successfully prepared. After that, the ascorbate oxidase and MBs volume ratios of MBs-ascorbate oxidase solution were 1:2, 1:1 and 1:0.5, respectively.

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C. Immobilization Method for the Ascorbate Oxidase-MBs and Graphene Oxide Membrane In order to immobilize ascorbate oxidase more stable and increased specific surface area, we prepared 0.3 wt% GO to modify the IGZO membrane. We used cross-linking agent, 3-glycidoxypropyltrimethoxysilane(GPTS), which was adopted to immobilize enzyme by covalent bonding method. We used the 100 μl GPTS solution and 400 μl toluene to prepare the crosslinking solution, and the cross-linking solution was dropped on the GO membrane. Then, the samples were baked by oven at 80 °C for 1 hour. Next, in order to remove unlinked cross-linking layer, the samples were immersed in the PBS solution. Finally, the MBs-ascorbate oxidase solution was dropped onto the cross-linking layer, and we stored the samples in refrigerator at 4 °C. III.

RESULTS AND DISCUSSION

A. Average Sensitivity and Linearity of Ascorbic Acid Biosensor In this study, the enzyme was used to increase the specificity for biosensor. The enzyme (ascorbate oxidase) belongs to oxidoreductase which can catalyze the redox between two molecules. Electrons and hydrogen ions were formed by using of ascorbate oxidase in L-ascorbic acid solution. The MBs-ascorbate oxidase/GO/IGZO/Al sensing membrane will adsorb the hygroden ions, and which resulted in the formation of the surface charge. The ascorbate oxidase reacts with L-ascorbic acid, which reaction mechanism was shown as the reaction (1) [7]: 2L-Ascorbate + O2 + 2H + Ascorbate oxidase

→

2Dehydro-L-Ascorbate + 2H2 O

(1)

The MBs-ascorbate oxidase/GO/IGZO/Al ascorbic acid biosensor was detected in L-ascorbic acid by above reaction mechanism. The volume ratios of ascorbate oxidase and MBs were investigated, which were 1:2, 1:1 and 1:0.5, respectively. The optimal volume ratio of ascorbate oxidase and MBs was 1:1, which could observe the biosensor possessed high average sensitivity of 78.9 mV/decade from Table I. Compared with other ascorbic acid biosensors, the average sensitivity of MBs ascorbate oxidase/GO/IGZO/Al ascorbic acid biosensor was higher than most literatures of potentiometric ascorbic acid biosensor [8-11].

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Table 1. The comparisons of the average sensitivity and linearity with various l-aa biosensors Sensing membrane Concentration Volume ratio Linearity Average Ref. range of L-AA of ascorbate sensitivity (mM) oxidase and (mV/decade) MBs MBs- ascorbate oxidase 0.003-2 1:2 0.992 74.9 This study /GO/IGZO/Al MBs- ascorbate oxidase 0.003-2 1:1 0.997 78.9 This study /GO/IGZO/Al MBs- ascorbate oxidase 0.003-2 1:0.5 0.989 74.0 This study /GO/IGZO/Al Graphite/resin2/PVC 0.008-3 N/A N/A 85.4 [8] 2004 Ethylene vinylacetate0.008-0.45 N/A N/A 50.3 [9] membrane 1999 ZnO nanorods 0.001-50 32 [10] N/A N/A 2011 PPy-MIPox/GCE 0.005-2 N/A N/A 56.8 [11] 2011 N/A: Not available

GO/IGZO/Al and MBs-ascorbate oxidase/GO/IGZO/Al membranes, we used the atomic force microscope (AFM) to measure the surface roughness of sensing membrane. It could be found that surface roughness of IGZO/Al, GO/IGZO/Al and MBs-ascorbate oxidase/GO/IGZO/Al membranes were 6.40 nm, 14.1 nm and 123 nm, respectively. The AFM results was shown in Fig. 2, Fig. 3 and Fig. 4. These experimental results could show not only the GO and MBs modified IGZO membrane successfully but also there were significant improvement on the surface roughness.

Besides, the biosensor possessed linearity of 0.997, which demonstrated biosensor possessed evident change of response voltage for each concentration from Fig. 1.

Fig. 1. The different volume ratios of ascorbate oxidase and MBs for MBs-ascorbate oxidase/GO/IGZO/Al ascorbic acid biosensor.

B. Surface Roughness for IGZO/Al, GO/IGZO/Al and MB/GO/IGZO/Al Membranes According to Table 1, in this study, the biosensor showed high average sensitivity. This significant improvement could be attributed to the high surface roughness of MBs. In general, surface roughness could affect electrochemical properties, catalytic activity and immobilization of enzyme [12-13]. Therefore, in order to analyze the surface roughness of IGZO/Al,

Fig. 2. The AFM surface morphology of IGZO membrane.

C. Response Time of Ascorbic Acid Biosensor In order to observe the response time for MBsAscorbate Oxidase/GO/IGZO/Al ascorbic acid biosensor responded to different concentrations of ascorbic acid solutions, we immersed the biosensor in three specific ascorbic acid solutions which were 0.007 mM, 0.031 mM and 0.125 mM, respectively. The definition of 255

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response time was described in the literature [14]. The response time was the time that response voltage achieved 90 % total response voltage. From Table II, it could be observed the biosensor possessed about 14 s response time for detection of ascorbic acid in ascorbic acid solution. However, this experimental result was the best in this study, but the literature [10] was better than our result. Therefore, in the future, it will need to be improved.

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D. Drift Effect of Ascorbic Acid Biosensor It is significant whether biosensor can be detected in test solution for long time. Therefore, the drift effect for MBs-ascorbate oxidase/GO/IGZO/Al ascorbic acid biosensor was investigated in this study. The drift effect was generally considered to be the effect resulted from the thickness of the hydrated layer. In this study, L-ascorbic acid solution consisted of the KH2PO4, K2HPO4 and L-ascorbic acid powders. Therefore, this solution has many positive ions and negative ions. If the sample is measured for the long time, positive ions or negative ions will adsorb H2O molecules to form hydrated layer [15], it could affect the formation of surface charge, and the surface charge increased with time. In this study, the concentration of L-ascorbic acid was set at 0.007 mM, and the drift rate is average voltage variation between the 12th hr and the 5th hr. The drift rate was shown in Fig. 5, and the response voltage only increased about 0.2% at 0.007 mM, 0.031 mM and 0.125 mM during 7 hr, which could confirm the MBs-ascorbate oxidase/GO/IGZO/Al ascorbic acid biosensor possessed the small drift effect.

Fig. 3. The AFM surface morphology of GO/IGZO/Al membrane.

Fig. 5. The drift effects of flexible arrayed MBs-ascorbate oxidase/GO/IGZO/Al ascorbic acid biosensor in different concentration ascorbic acid solutions.

Fig. 4. The AFM surface morphology of MBs-ascorbate oxidase/GO/IGZO/Al membrane.

E. Anti-interfering Effect of Ascorbic Acid Biosensor Selectivity of the biosensor for L-ascorbic acid was investigated in this experiment. First, we waited for steady state of response voltage in Lascorbic acid solution of 0.007 mM. Next, seven interfering substances, such as uric acid (UA), acetaminophen (AP), Urea, L-cysteine monohydrochloride (L-cy), L-glutathione (GSH), glucose and lactate were sequentially

Table 2. The comparaisons of the response time for different l-aa biosensors Structure of L-AA Response Ref. biosensor time (s) MBs-Ascorbate 14 This study Oxidase/GO/IGZO/Al/PET Ethylene vinylacetate300 [9] membrane 1999 ZnO nanorods <10 [10] 2011

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injected in L-ascorbic acid solution at the 60th second, the 120th second, the 180th second, the 240th second, the 300th second, the 360th second and the 420th second. Finally, L-ascorbic acid solution with higher concentration was injected at the 480th second in mixed solution. According to the experimental result of Fig. 6, it could be observed that the biosensor possessed high selectivity for L-ascorbic acid in mixed solution. Besides, the response voltage of biosensor was stable for interfering substances in this experimental result. Therefore, the biosensor not only possessed high selectivity but also showed high stability in mixed solution.

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which was developed. The MBs-ascorbate oxidase/GO/IGZO/Al ascorbic acid biosensor with many outstanding merits has promising perspectives. ACKNOWLEDGMENTS

This study has been supported by Ministry of Science and Technology, Republic of China, under the contracts MOST 105-2221-E-224 -049 and MOST 106-2221-E-224-047. REFERENCES [1] J. E. Enstrom, Epidemiology of Vitamin C, Reference Module in Biomedical Sciences International Encyclopedia of Public Health, 2 (2017) 559–568. [2] D. E. Yates, S. Levine, T. W. Healy, Site-binding model of the electrical double layer at the oxide/water interface, Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases, 70 (1974) 1807-1818. [3] J. Lee, J. Kim, S. Kima, D. H. Min, Biosensors based on graphene oxide and its biomedical application, Advanced Drug Delivery Reviews, 105 (2016) 275287. [4] L. Reverte, B. Prieto-Simon, M. Campas, New advances in electrochemical biosensors for the detection of toxins: nanomaterials, magnetic beads and microfluidics systems. a review, Analytica Chimica Acta, 908 (2016) 8-21. [5] S. Kiralp, A. Topcu, G. Bayramoğlu, M. Y. Arıca, L. Toppare, Alcohol determination via covalent enzyme immobilization on magnetic beads, Sensors and Actuators B: Chemical, 128 (2008) 521-528. [6] A. Sassolas, A. Hayat, J.-L. Marty, Immobilization of Enzymes on Magnetic Beads Through Affinity Interactions,” in Immobilization of Enzymes and Cells, 1051 (2013) 139-148. [7] E. Akyilmaz, E. Dinçkaya, A new enzyme electrode based on ascorbate oxidase immobilized in gelatin for specific determination of L-ascorbic acid, Talanta, 50 (1999) 87-83. [8] P. G. Veltsistas, M. I. Prodromidis, C. E. Efstathiou, All-solid-state potentiometric sensors for ascorbic acid by using a screen-printed compatible solid contact, Analytica Chimica Acta, 502 (2004) 15-22. [9] J. C. B. Fernandes, L. T. Kubota, G. de Oliveira Neto, Potentiometric biosensor for l-ascorbic acid based on ascorbate oxidase of natural source immobilized on ethylene–vinylacetate membrane, Analytica Chimica Acta, 385 (1999) 3-12. [10] Z. H. Ibupoto, Syed M. Usman Ali, K. Khun, M. Willander, L-ascorbic acid biosensor based on immobilized enzyme on ZnO nanorods, Journal of Biosensors & Bioelectronics, 2 (2011) doi.org/10.4172/2155-6210.1000110. [11] D. Tonelli, B. Ballarin, L. Guadagnini, A. Mignani, E. Scavetta, A novel potentiometric sensor for l-ascorbic

Fig. 6. The anti-interfering effect of flexible arrayed MBsascorbate oxidase/GO/IGZO/Al ascorbic acid biosensor.

CONCLUSION In this study, we used MBs and GO to improve the biosensor. According to the experimental results of AFM, it could be found that the membrane possessed high surface roughness. Therefore, MBs-ascorbate oxidase/GO/IGZO/Al ascorbic acid biosensor was applied in detection of ascorbic acid which possessed good average sensitivity and linearity. Besides, the biosensor possessed rapid response time about 14 s for detection of ascorbic acid. The experimental results of drift effect showed that the biosensor could be detected in ascorbic acid solution for long time. The response voltage only increased about 0.2% at 0.007 mM, 0.031 mM and 0.125 mM during 7 hr. The anti-interfering effect experiment was carried out through seven interference substances, and it could be found the biosensor possessed high selectivity for ascorbic acid. In this study, a biosensor possessed rapid response, high average sensitivity, high selectivity and high stability IV.

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The 12th Asian Conference on Chemical Sensors (ACCS2017) acid based on molecularly imprinted polypyrrole, Electrochimica Acta, 56 (2011) 7149-7154. [12] S. Pakapongpan, R. P. Poo-arporn, Self-assembly of glucose oxidase on reduced graphene oxide-magnetic nanoparticles nanocomposite-based direct electrochemistry for reagentless glucose biosensor, Materials Science and Engineering: C, 76 (2017) 398405. [13] S. Ameen, M. S. Akhtar, H. S. Shin, Nanocagesaugmented aligned polyaniline nanowires as unique platform for electrochemical non-enzymatic glucose biosensor, Applied Catalysis A: General, 517 (2016) 21-29. [14] D. Yu, Y. d. Wei, G. h. Wang, Time-dependent response characteristics of pH-sensitive ISFET, Sensors and Actuators B: Chemical, 3 (1991) 279285. [15] E. Ruckenstein, H. Huang, Specific ion effects on double layer forces through ion hydration, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 459 (2014) 151-156.

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The 12th Asian Conference on Chemical Sensors (ACCS2017)

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A Cell-Based Chip Integrated with Microfluidic Control and Dissolved Oxygen Sensors for Estimation of Cellular Respiratory Activity Ching-Chou Wua, Chieh-Jen Wanga, Lee-Tian Changb a

Department of Bio-industrial Mechatronics Engineering, National Chung Hsing University, b Department of Veterinary Medicine, National Chung Hsing University, Addr: No. 145 Xingda Rd. Taichung, Taiwan. Email: [email protected]

Abstract: Adipocyte activity determines the metabolism of carbohydrate and fatty acid of human beings, related to the formation of diabetes. Evaluation of adipocyte activity allows the researchers to realize the causes of type II diabetes and therapeutic methods. In the study, a microfluidic chip containing dissolved oxygen (DO) sensors of three-electrode electrochemical system was developed for the measurement of DO around the cultivated adipocytes. All gold electrodes were made by the lift-off microfabrication process. Moreover, the iridium oxide layer was electrodeposited on a gold electrode as the reference electrode. The DO sensing chip was fixed by the homemade polymethylmethacrylate clamp. Adipocytes were estimated with the stimulation of different glucose concentration (0 mM, 11 mM) and insulin, and then the DO signal was analyzed by three kinds of methods. The respiratory activity can be defined as a DO consumption ratio of the drug-stimulated adipocytes versus normal status adipocytes. The results show that the respiratory activity obtained by the diffusion-model of ultramicrodisk electrode presented high reproducibility and good physiological behavior. The DO microfluidic chip has a great promise in the application of estimating the effect of drugs on the cellular physiological behavior to replace animal and clinical experiments. Keywords: dissolved oxygen electrode, microfluidic chip, respiratory activity, adipocyte

I. INTRODUCTION Adipocyte activity is closely related to the physiological state, and is mainly responsible for energy storage by white adipocyte and metabolism by brown adipocytes in the body, respectively. Adipocytes uptake glucose and consumes oxygen during the metabolic process to produce energy, such as adenosine triphosphate (ATP). Adipocyte activity determines the metabolism of carbo-hydrate and fatty acid of human beings, related to the formation of diabetes. The patients with type II diabetes, whose adipocytes, liver or muscle cells, have produced resistive to insulin. Therefore, it is required of insulin injections to promote the abilities of liver cells and muscle cells uptake glucose. However, it also promotes the synthesis of adipocytes. When the number of adipocytes became more or the volume of adipocytes increased, it will cause obesity. Moreover, it will case other complications, such as osteoporosis, or cardiovascular disease, etc [1]. The current study has shown that the main reason to cause type II diabetes was insulin resistance generation, which limited the ability of glucose transfer and affected the activity of mitochondria, thereby changing the rate of cellular metabolism. Mitochondria produced energy in the process of aerobic respiration, in order to promote cell growth, cell division and cell movement with 259

ATP consumption. One unit of glucose after the process of glycolysis and citric acid cycle, 38 ATP molecules can be synthesized, and simultaneously consuming six oxygen molecules. Since oxygen can enter the cell membrane randomly, it is able to measure the change of extracellular dissolved oxygen to know cell respiratory activity. The current detection techniques for cellular respiratory activity have two methods, one is optics, and the other is electrochemistry. The electrochemical method, without fluorescent dying, is fast, direct and easy to detect with high resolution of signal. Moreover, with the design of ultramicro electrodes (UMEs), the current can reach steady-state or quasi-steady state in short time. The advantages of UMEs are high current density, low oxygen consumption itself, and fast detection. In the study, a microfluidic chip containing DO sensors of three-electrode electrochemical system was integrated with a peristaltic pump for the measurement of DO around the cultivated adipocytes. The resulting microdevice containing gold electrodes as working electrodes (WE) and counter electrodes (CE), and iridium oxide (IrOx) layer was electrodeposited on one of gold electrode as the reference electrode (RE). Development of integrated microfluidic system and the dissolved oxygen electrode array chip to evaluate the cell response after different genetic

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modification of adipocyte to glucose utilization and insulin sensitivity. II.

EXPERIMENTAL

A. Chip design Development of DO electrodes integrated with microfluidic system is used to directly estimate cell activity under small-volume liquid and highthroughput situation. The steps of experiment is sequentially chip design, the integration of cell chip and microfluidic system, the flow rate test of liquid changing, the characteristic test of electrodes and assessment of cellular metabolism of adipocytes. The electrode structures are fabricated in microfabrication technology on glass substrate with 250 nm gold/20 nm titanium layer. Passivated areas and conducting paths are isolated with SU-8 negative photo resist. The area of WE and RE are 20 μm2 and 0.785 mm2, respectively. In Fig.1, the DO sensing chip was fixed by the homemade polymethylmethacrylate (PMMA) clamp with 3M adhesive tape. The 3M tape can increase 100 μm high in order to decrease the shear force to the effect of cells adhesion. A peristaltic pump was used to withdraw the solution so as to estimate the effect of fluidic flow rate to cells.

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was stirred for 10 min. Then, 250 mg of oxalic acid was added and stirred for 10 min. Anhydrous potassium carbonate was slowly added to adjust the pH of solution to 10.5. The solution was placed at room temperature for 2 days for stabilization. After stabilization, the solution was kept in a dark bottle at 4C until use [4]. IrOx film was simultaneously electrodeposited on the Au electrodes by cycling 100 times from 0.0 V to 0.6 V at the scanning rate of 10 mV/s with a multi-potentiostat (1000A, CH Instruments) in a three-electrode configuration (Fig.2). An Ag/AgCl electrode and a Pt wire acted as the RE and the CE, respectively. After electrodeposition, the IrOx electrodes were rinsed with distilled water, and then soaked in universal buffer of pH 7.00 for 2 days to stabilize the potential readings [2].When not in use, the IrOx-deposited electrodes were stored in universal buffer of pH 7.00 at 4 ºC in a dark bottle.

Fig. 2 Cyclic voltammograms performed in the deposition solution (pH 10.5) at a Au electreode with the scanning rate of 10 mV/s.

Fig. 1 The design of cell-based chip.

B. Electrodeposition of IrOx film The fabrication of IrOx electrode techniques described in our previous literature [2]. The deposition solution of IrOx used in the study was prepared as below accordind to the method first described by Yamanaka [3], 75 mg of iridium tetrachloride was dissolved in 50 ml of distilled water by stirring for 15 min. 0.5 ml of 30% hydrogen peroxide was added and the solution 260

C. Measurement of adipocytes respiratory activity The activity of adipocytes was estimated by i-t curve method relative to an IrOx RE. Put two different situations of genetic modification of adipocytes into the cultured tank for 1.5 h, then measure the cell respiratory activity at the same time by microfluidic system. Repeat the experiments for three times. With DO electrode to estimate the CP gene expression and nonexpression on adipocytes, in order to know the change of cell respiratory activity. Evaluation of adipocyte activity allows the researchers to realize the causes of type II diabetes and therapeutic methods.

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D. Measuring analysis methods Adipocytes were estimated with the stimulation of different glucose concentration (0 mM, 11 mM) and insulin, and then the DO signal was analyzed by three kinds of methods (called M1, M2 and M3) to evaluate the respiratory activity, respectively. The M1 derived from Bionas calculates the slope (pA/s) of current curve (10200 s) [4]; the M2 records the current value of 100th second (nA) after dropping a testing solution; the M3 obtains a relative DO concentration (C') from the current of 50-200 s period via the quasi steady state diffusion of band ultramicroelectrode simulation. Then, calculate the relative value of the activity, defining as a DO consumption ratio of the drug-stimulated adipocytes versus normal status adipocytes. 𝐶’ −𝐶’

𝑐−𝑑 A𝑐𝑡𝑖𝑣𝑖𝑡𝑦 = 𝐶’𝑚𝑚−𝐶’𝑐−𝑚

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B. Cell attachment When conducting the replacement of waste liquid in cul-tured tank, the shear force of liquid may influence the abil-ity of cell-attachment. Fig.4(a) shows the states of cell at-tached for 1.5 hr, and Fig.4(b) shows after replacement of test solution for 20 times, cells are not washed from the surface of chip.

Fig. 4. The pictures of cell states with and without liquid changing.

(1)

C’m defined as oxygen concentration of medium；C’c-m defined as oxygen concentration of medium with cells；C’c-d defined as oxygen concentration of drug-containing HBS with cells. III. RESULTS AND DISCUSSION A. Reproducibility of the fluid system After configured the cell chip with PMMA mold, inserting the peristaltic pump dedicated pipe, then conducting the test of liquid changing under 70 rpms. The results shows that the liquid can change completely in 90 sec both on the fluorescent and the electrochemical methods in Fig.3.

Fig. 3 (a) the fluorescent way, I: injecting fluorescent liquid for 90 s; II: fluorescent liquid drain for 90 s; III: injection of deionized water for 90 s; IV: drain the deionized water for 90 s. (b) Alternative change between PBS and ferricyanide.

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C. Measurement of cellular respiration activity The cell chip is capable of changing liquid under less influence to cells in cultured tank. Fig.5 shows the calculation of cellular respiration activity for the normal adipocytes cells of about 4000 cells/mm2 by three different kinds of analysis methods. The M1 shows that convection disturbed the initial current value, causing the measurements with three different cell lines have a greater relative standard deviation (RSD). M2 does not influence by convection, so it has less RSD value than M1 (<15%). However, to avoid affecting the stability of the vulnerable point measurement system by M2, M3 use quasi-steady state diffusion of band ultramicroelectrode theory to to fit the current value. The squared correlation (R2) of fitting results is at least larger than 0.995, imply that the measurement of oxygen sensor has a good reproducibility with RSD < 5%. With measuring the current value of oxygen-consumption and calculating the respiration activity of adipocytes cells, the results of cellular respiration activity obtained in 10 mM HEPES buffer solution (HBS) containing 11 mM glucose and HBS containing 11 mM glucose+10 μM insulin was 1.09 and 1.13 times larger than that obtained in HBS, respectively.

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adipocytes to the normal adipocyte. The results show that the respiratory activity obtained by the M3 presented high reproducibility (<5%) and good physiological behavior. The DO microfluidic chip has a great promise in the application of estimating the effect of drugs on the cellular physiological behavior to replace some animal and clinical experiments. ACKNOWLEDGMENT We gratefully acknowledge the partial support by the grants from the National Science Council (MOST104-2313-B-005-036-MY3 and MOST 104-2622-B-005-007-CC2). REFERENCES Fig. 5. (a) Estimation of the DO reduction current through amperometric of normal adipocytes; (b) three different kinds of analysis methods for cellular respiration activity. IV.

CONCLUSION

The microfluidic DO sensing chip, integrated by micro manufacturing process, electrochemical techniques and microfluidic injection system, can non-invasively estimate in situ adipocyte activity under different situation. After the modification of poly-L-lysine for 1 h, the cells can adhesion on the cell chip easily. Moreover, it is time-saving, lowcost and convenient micro-device for oxygen consumption estimation. The respiratory activity can be defined as a DO consumption ratio of the drug-stimulated

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C. L. T. Chang, H. Y. Liu, T. F. Kuo, Y. J. Hsu, M. Y. Shen, C. Y. Pan and W. C. Yang, Antidiabetic Effect and Mode of Action of Cytopiloyne, Evidence-Based Complementary and Alternative Medicine, (2013) 685642. [2] I. A. Ges, B. L. Ivanov, D. K. Schaffer, E. A. Lima, A. A. Werdich, F. J. Baudenbacher, Thin-film IrOx pH microelectrode for microfluidic-based microsystems, Biosensors and Bioelectronics, 21 (2005) 248 - 256. [3] Yamanaka K. Anodically Electrodeposited Iridium Oxide Films (AEIROF) from Alkaline Solutions for Electrochromic Display Devices, Japanese Journal of Applied Physics, 28 (1989) 632–637. [4] L. Ceriotti, A. Kob, S. Drechsler, J. Ponti, E. Thedinga, P. Colpo, R. Ehret, F. Rossi, Analytical Biochemistry, 371 (2007) 92–104. [1]

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Adsorption Behavior of H2O, OH and H to Sr-Ca-Cu-O Superconducting Materials Akira Fujimoto1, Satoshi Shinoda2, Tadachika Nakayama2 and Hisayuki Suematsu2 1

National Institute of Technology, Numazu College, 3600 Ooka, Numazu, Shizuoka 410-8501, Japan Faculty Nagaoka University of Technology, 1603-1 Kamitomioka Nagaoka, Niigata 940-2188, Japan [email protected]

2

Abstract: Adsorption behavior of H2O, H and OH to the Sr2CaCu2Oy superconducting material was investigated by molecular orbital calculations. H2O molecular, H+ and OH- species were closing to simplified cluster of Sr2CaCu2Oy to estimate adsorbed position of the molecular or the species. Total heats of formations were calculated for the cluster and closing molecular or species using MOPAC program with PM5 Hamiltonian. Calculation results showed that H2O and OH- were adsorbed stably around 1.5 Å from the cluster. Expansion of c axis resulted from intercalation was observed for closing H2O molecular and OH- species along within the (110) plane agreed with experimental results. These results suggest that Sr2CaCu2Oy material can detect H2O, OH and H by its superconducting characteristics changes. Keywords: gas sensor, Sr2CaCu2Oy, molecular orbital calculation, cluster

I. Introduction The Sr-Ca-Cu-O system was well known have many superconductive phases including Sr2CaCu2Oy, which is a zero-charge reservoir material and can be synthesized under high pressure [1-2]. The material expands along with caxis and change superconductive characteristics such as critical temperature and critical magnetic field by exposing humid ambient [3]. It was supposed that these changes were caused by forming derivation phase of the materials, but the mechanism was still unknown [4]. Adsorption behavior of alcoholic gases to SnO2 gas sensor material was investigated precisely by molecular orbital calculation [5-6]. We try to calculate the Sr2CaCu2Oy with H2O molecular to reveal adsorption behavior of H2O molecular, OH and H species to the Sr2CaCu2Oy structure by molecular orbital method.

In this paper, we calculate total heat of formation and reaction gradient of Sr2CaCu2Oy and H2O molecular, OH and H species by molecular orbital calculation with simplified Sr2CaCu2Oy cluster. The results showed the H2O molecular and OH- species adsorbed stable to the Sr2CaCu2Oy superconducting material and possibility of the materials as a sensor material to detect H2O molecular. II.

Calculation Procedure

A. Sr2CaCu2Oy cluster The Sr2CaCu2Oy original structure is shown in figure 1 to the left. The structure was simplified to small cluster for shorten calculation time. The cluster was optimized independently before calculation. The cluster used for calculation is shown in figure 1 to the right includes 10 Sr and Ca atoms, 10 Cu atoms and 18 Oxygen atoms B. Calculation method The H2O molecular or H+ or OH- species was connected to dummy atom which defines distance from the Sr2CaCu2Oy cluster to the molecular or

Figure 2. Configurations of closing molecular or species to Sr2CaCu2Oy cluster with perpendicular to the (100) plane (left) and along with the (110) plane (right).

Figure 1. Sr2CaCu2Oy structure (left) and simplified cluster using calculation (right).

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Table I Combinations of molecular/species and directions for calculation. Perpendicular Parallel Direction to (100) face to (110) face H2O

A

B

OH-

C

D

H+

E

F Distance (angstrom)

the species and also defines closing direction of the molecular or species. Total heat of formation of the cluster and the molecular or the species and reaction gradient were calculated for the distance from 5 to 0 angstroms every 0.2 angstrom with directions perpendicular to the (100) plane and along with the (110) plane shown in figure 2. Six combinations of molecular and species, direction for closing shown in Table I were calculated successfully. SCIGRESS MO Compact program from Fujitsu Co. with PM5 Hamiltonian was used for calculations. III.

Figure 4. The variations of total heat of formation and reaction gradient changes as a function of distance from the Sr2CaCu2Oy cluster to H2O molecular along with the direction parallel to the (110) plane of the cluster.

directions of parallel to the (110) plane instead of perpendicular to the (100) plane of the cluster. Figure 4 shows the total heat of formation and reaction gradient changes for closing H2O molecular to the Sr2CaCu2Oy cluster in the direction of parallel to the (110) plane. H2O molecular may be adsorbed around 1.8 Å from the cluster because total heat of formation reached minimum around the distance. Intercalation may occur in this case due to expansion of c-axis was observed.

Results and discussion

A. In case of H2O perpendicular to the (100) plane Total heat of formation and reaction gradient changes for closing H2O molecular to the Sr2CaCu2Oy cluster in the direction of perpendicular to the (100) plane is shown in figure 3. The total heat of formation increases monotonically with closing H2O molecular to Sr2CaCu2Oy cluster. No stable adsorption point will exist in the vicinity of the Sr2CaCu2Oy cluster. It is supposed that H2O molecular doesn’t adsorb stable to the cluster.

C. In case of OH- perpendicular to the (100) plane H2O may decompose to H+ and OH- when close to Sr2CaCu2Oy cluster. Figure 5 shows the total heat of formation and reaction gradient changes for closing OH- species to the cluster in the direction of perpendicular to the (100) plane. Stable adsorbed point is around 2.5 Å results from reaction gradient reach to zero and total heat of formation reach bottom. No expansion of c-axis was found. It is supposed that no intercalation occurs in this case.

B. In case of H2O parallel to the (110) plane H2O molecular is closed to the cluster with

Distance (angstrom)

Distance (angstrom)

Figure 3. The variations of total heat of formation and reaction gradient as a function of distance between the Sr2CaCu2Oy cluster and H2O molecular along with the direction perpendicular to the (100) plane.

Figure5. The variations of total heat of formation and reaction gradient as a function of distance from the Sr2CaCu2Oy cluster to OH- species along with the direction perpendicular to the (100) plane of the cluster.

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Figure 6. The variation of total heat of formation and reaction gradient as a function of distance from the Sr2CaCu2Oy cluster to H2O molecular along with the direction parallel to the (110) plane of the cluster.

0 -50

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E. In case of H+ perpendicular to the (100) plane Figure 8 shows the total heat of formation and reaction gradient changes for closing H+ species to the Sr2CaCu2Oy cluster in the direction of parallel to the (110) plane. Total heat of formation increases monotonically with closing H+ species to the cluster. H+ species doesn’t adsorb to the cluster and no optimum structure was obtained in this case. F. In case of H+ parallel to the (110) plane Figure 9 shows the total heat of formation and reaction gradient changes for closing H+ species to the Sr2CaCu2Oy cluster in the direction of parallel to the (110) plane. The total Heat of formation reaches minimum and reaction gradient reaches to zero at the distance of around 1.2 Å. Optimum structure will be obtained at the distance

-1 (kcal Reaction gradient・ angstrom )

(kcal Heat of formation・ mol-1)

0

1

-500

750

zero. Intercalation will occurs in this case by the expansion of c-axis of the cluster. Maximum expansion of 0.12 Å in c-axis was observed in this case. Figure 7 shows the optimum structure of the cluster with OH- species at distance of 1.5 Å from the cluster.

Figure 7. Optimum structure of the Sr2CaCu2Oy cluster with adsorbed OH- species.

Reaction cordinate (angstrom) Distance (angstrom)

: Heat of formation : Reaction gradient

Figure 9. The variations of total heat of formation and reaction gradient as a function of distance from the Sr2CaCu2Oy cluster to H+ species along with the direction parallel to the (110) plane of the cluster.

D. In case of OH- parallel to the (110) plane Figure 6 shows the total heat of formation and reaction gradient changes for closing OH- species to the cluster in the direction of parallel to the (110) plane. Total heat of formation reached bottom at the distance of around 1.5 Å from the cluster. It is supposed that OH- species is adsorbed stably as an optimum structure at the distance because of the reaction gradient also reached to

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0

0

Distance (angstrom)

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Figure 8. The variation of total heat of formation and reaction gradient as a function of distance from the Sr2CaCu2Oy cluster to H+ species along with the direction perpendicular to the (100) plane of the cluster.

Figure 10. Optimum structure of the Sr2CaCu2Oy cluster with adsorbed OH- species.

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of 1.2 Å from the cluster to H+ species as shown in figure 10. No expansion of c-axis was observed in the structure. IV. Conclusion Adsorption behavior of H2O, H+ and OH- to Sr2CaCu2Oy superconducting material was investigated by molecular orbital calculation successfully. H2O molecular will decompose to H+ and OH- species during closing to the cluster. Expansion of c-axis of Sr2CaCu2Oy cluster was observed by adsorbing H2O molecular and OHspecies. It may be possible to detect H2O and OHby the change of superconductive characteristics of Sr2CaCu2Oy materials. Further improvements of calculation will need to estimate interaction between Sr2CaCu2Oy materials and H2O molecular accurately. Acknowledgment The current work was partially supported by JSPS KAKENHI Grant Numbers JP16K05007 and JP15H03875.

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References [1]

[2]

[3]

[4]

[5]

[6]

T. Kawashima nd E. Takayama-Muromachi, Superconductivity in the series of compounds Sr2 Can1CunOy (n=1-4) prepared under high pressure, Physica C , 282-287, (1997) 513-514. M. Ushiki, T. Motohashi, H. Yamauchi, and M. Karppinen, High-pressure synthesis of the “zero-chargereservoir” 0223 superconductor in the Sr–Ca–Cu–O system, Physica C 378–381, Part 1 (2002) 167-172. H. Yamauchi, M. Karppinen, T. Hosomi and H. Suematsu, Water-containing phases derived from “02(n−1)n” superconductors.: II. Derivative of the Sr2Ca2Cu3O8±δ (0(Sr)223) phase, Physica C, 338 (2000) 46-51. M. Karppinen, H. Yamauchi, T. Hosomi, H. Suematsu and H. Fjellvåg, Superconducting Cuprates with Charge Reservoir Consisting of either Peroxide-type Oxygen or H2O, J. Low Temp. Phys, 117 (1999) 843–847. T. Kanashima, A. Fujimoto and M. Okuyama, Theoretical Analysis of Methanol and Hydrogen Adsorptions on SnO2 by Molecular Orbital Calculation, The 10th Int. Conf. on Solid-State Sensor and Actuators, Digest of Tech. Paper, 1 (1999) 154-157. A. Fujimoto, M. Ohsumi and Y. Ohtani, Activation Energy Dependence on Transient Response of Semiconductor Gas sensor, 13th Int. Met. On Chem. Sensors, Tech. Digest (2010) 104.

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An Au-TiO2-Ti Structure Based Schottky Barrier Surface Plasmon Resonance Sensor Enables Miniaturization of SPR Sensing System Chao Wang1, Chen-Hsuan Hsia1, Jian-Hong Yang2, Chii-Wann Lin1,2,* 1 2

Institute of Biomedical Engineering, National Taiwan University, No.49, Fang-Lan Rd., Taipei City 10672, Taiwan Institute of Applied Mechanics, National Taiwan University, No.1, Sec.4, Roosevelt Rd., Taipei City 10617, Taiwan *Corresponding author: [email protected]

Abstract: In this article, we propose a Surface Plasmon Resonance (SPR) sensor design based on Metal-DielectricMetal (MDM) structure on a prism coupler, which merges the merits of SPR with this miniaturized Au-TiO2-Ti MDM device. The detecting theory of the sensor could be explained by electro-optical energy conversion theory. The damping of SP waves, namely the perturbation to the thermal equilibrium inside metal, happens simultaneously when wave propagates along the Au-TiO2 interface. As a result, hot electrons and equivalent hot holes are excited and emitted from metal to dielectric. Schottky barrier formed with well-matched metal and semiconductor helps to collect the plasmonic hot electrons as photocurrent and block the noise. Performance of the sensor is discussed and predicted by FDTD and MATLAB simulations. A dynamic range covering refractive index from 1.332 to 1.338 R.I.U could be obtained by concentration identification simulation. The electric field strength near the TiO 2-water interface is nearly 16 times of incident field, and the penetration depth of e-field into water is over 180nm, which meets the technical demands of using it as a biosensor. Keywords: Surface Plasmon Resonance, Schottky Barrier, Metal-Dielectric-Metal, Internal Electron Emission, Simulation

I. INTRODUCTION Surface Plasmon Resonance (SPR) is a physical phenomenon which occurs commonly at metal-dielectric or metal-vacuum interface, especially noble metal including gold and silver. This phenomenon can be described as a result of interactions of incident electromagnetic waves and the surface charges inside metal: The electro part of incident field is induced onto and propagates alone the metal-dielectric interface, while free electrons in metal are driven to oscillate collectively when surface plasmon is excited. Theoretically, surface plasmon can be excited by electromagnetic waves in visible and infrared with proper materials. The resonance condition is very sensitive to the changes of refractive index near the metal-dielectric interface, even tiny changes caused by molecules binding reaction could have a influence on the resonance status. Therefore, SPR has been extensively studied during the past decades as a cutting edge sensing technology, for its remarkable merits, such as extremely high sensitivity, rapid response, label-free, noninvasive, and good compatibility with DNA-DNA or antigen-antibody reactions. Many sensors and instruments are successfully developed in recent years, and the prism coupler-based Otto[1] or Kretschmann[2] optical excitation methods are well studied and mostly used. However, the complicated optical measurement setup of prism coupler-based SPR sensors, leads to bulky size, heavy weight, and high cost of the system. As a 267

result, those products are rigorously restricted to operate by professionals inside laboratory. Facing the growing needs of field test, bedside test or other spot test outside laboratory, kinds of attempts have been made to develop a portable SPR system also satisfied for clinical use, while this problem still remains unsolved yet. In the present research, a metal-dielectric SPR excitation structure, also a metal-semiconductor Schottky contact, is combined with a semiconductor-metal Ohmic contact to form a Metal-Dielectric-Metal (MDM) tri-layer SPR sensor, see Figure 1. The materials and parameters involved are discussed and verified by simulations.

Figure 1. 3D picture shows the detail of proposed sensor. (a) The appearance of the sensor, assembled with a prism coupler. (b) Layers information of the sensor.

II. MDM STRUCTURE-BASED SENSOR A. Theoretical basis: Plasmonic hot carrier generation, screening, & collection The photocurrent signal can be produced by plasmonic hot-carrier generation process, which

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has been reported and demonstrated by former researches on nanostructure-based localized SPR[3]. In general, when surface plasmon is excited, electro part of incident field is induced to propagate alone the metal-dielectric interface. Free electrons or the surface charges within a distance of 𝛿 from the metal-dielectric interface are driven by the electric field to accelerate and oscillate collectively. 𝛿 is the penetration depth of surface plasmon. Due to the oscillation, surface plasmon waves decay to lose energy, while the electrons become energetic and jump up to higher energy level simultaneously, which causes a perturbation to the original thermal equilibrium in the metal. The energetic electrons, which is also called hot electrons, can be emitted into a dielectric material contacted with metal and consequently form the photocurrent.

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Finally, the screened photocurrent flows out through an Ohmic contact, then the current can be converted into voltage or measured directly. B. Materials & geometry Noble metals are usually used to excite surface plasmon, especially gold. Dielectric material TiO2 and ZnO are both n-type semiconductor which has a 3.2eV wide band-gap. Figure 3-a compares the performance of TiO2 with ZnO in SPR excitation as a gold-dielectric bi-layer structure, and the result shows that Au-ZnO has a relatively better performance on sensitivity and tolerance to fabrication roughness, but a worse dynamic range than Au-TiO2. However, as an Electron-Transport Material, TiO2 can help to capture electrons when hot electron-hole pairs are excited, preventing recombination caused electron loss. Also, as a n-type semiconductor, TiO2 forms a Schottky barrier with gold, and the barrier height is about 1eV. To form an Ohmic contact with TiO2 on the other side, titanium would be a choice. a.

Figure 2. (a) Hot carrier generation by propagating SPR, and (b) electrons screening by a Schottky barrier.

Obviously, surface plasmon resonance is not the only mechanism to generate photocurrent. Hot electrons sourced from photovoltaic effect in metal and band-to-band excitation in dielectric also make contribution to the total current signal. Because their excitation statues do not change with refractive index, hot electrons produced via these two mechanisms should be removed as noise from the total current. Former researchers found that photovoltaic effect induced hot electrons have lower energy than electrons excited by surface plasmon, and these unwanted hot electrons can be effectively blocked by setting an Schottky barrier with proper height[4, 5]. In addition, band-to-band excitation in dielectric can be prevented by using wide band-gap dielectric material, for example, incident field with wavelength in ultraviolet is needed to excite hot electrons in a wide band-gap material such as TiO2. Figure 2 shows the hot carrier generation process by propagating SPR, and electrons screening by a Schottky barrier. 268

b.

c.

Figure 3. Reflectance versus incident angle relationship resulted from incident angle modulated SPR excitation simulation, (a) with different materials and thickness, (b) with different thickness of Au layer, (c) with different thickness of TiO2 layer when thickness of Au layer is 50nm.

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The thickness of each layer is confirmed by SPR excitation simulations. The result of Au monolayer simulation in Figure 3-b shows that the largest reflectance at resonance angle can be reached when Au is 50nm-thick. Based on that, the result of Au-TiO2 bi-layer simulation in Figure 3-c figures out that the thinner the dielectric layer is, the smaller the resonance angle will be. The slope and linear range of curve also varies with the thickness of TiO2. Besides, the breakdown voltage of Au-TiO2 junction should be taken into consideration. After all, the trade-off between sensitivity and dynamic range can be balanced when TiO2 layer is 20nm-thick. C. FDTD simulation As an initial research, FDTD simulation was conducted to evaluate the performance of MDM structure as a sensor. A simplified MDM structure 2D model was made as shown in Figure 4.

Figure 4. The MDM structure 2D model used in FDTD simulation contains 4 parts, cylinder prism coupler, 50nmthick Au film, 20nm-thick TiO2 film, and water representing the sample. The red arrow points at the direction of incident light.

In simulation, the incident angle was modulated from 0 to 90 degree, and the electric field strength of incident light was set to be a constant, then the electric field strength distribution of surface plasmon waves was calculated. First, the Au and TiO2 layer was set to be 50nm and 20nm-thick separately, and the incident angle was modulated from 5 to 85 degree. Figure 5 presents the results from 35 to 70 degree in an interval of 5 degree, because there is no significant surface plasmon wave excited outside this range. An obvious waveform of surface plasmon can be observed when incident angle is 47 degree. Second, the effects of thickness of TiO2 on electric field strength distribution of surface plasmon was studied, while the incident angle was settled at certain value. Figure 6 shows that the results at thickness from 10nm to 40nm in an interval of 269

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10nm. The electric field strength reaches 16 times of incident field when the thickness of TiO2 is 20nm. The penetration depth of electric field into water reaches over 180nm, which is sufficient for using as a biomedical sensor.

Figure 5. FDTD simulation of incident angle on electric field strength distribution of surface plasmon.

Figure 6. FDTD simulation of thickness of TiO2 on electric field strength distribution of surface plasmon.

Figure 7. Reflectance-concentration simulation result.

To predict the potential dynamic range of such a MDM sensor, we attempted to simulate the reflectance-incident angle relationship under different concentration or refractive indices. A group of glucose solution with concentration ranges from 0 to 200 mg/mL in an 10mg/mL

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concentration interval were used as samples in simulation. Assume the relationship between reflectance and value of photocurrent is linear. Figure 7 shows that the proposed MDM sensor is predicted to achieve a dynamic range of 0.006 R.I.U. III. CONCLUSION This paper presented a novel designed MDM structure based SPR sensor. Simulations were made to evaluate the performance of the proposed sensor, and the results indicate that MDM structure based sensor is theoretically feasible. This senor, combining with an integrated signal processing system, will surely help to realize a miniaturized SPR sensing system in the future. ACKNOWLEDGMENT This study was supported in part by the Ministry of Science and Technology of R.O.C. under grant MOST 106-2221-E-002-059-MY2.

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REFERENCES [1] Otto, A., Excitation of nonradiative surface plasma waves in silver by the method of frustrated total reflection. Zeitschrift für Physik A Hadrons and nuclei, 1968. 216(4): p. 398-410. [2] Kretschmann, E. and H. Raether, Notizen: Radiative Decay of Non Radiative Surface Plasmons Excited by Light, in Zeitschrift für Naturforschung A. 1968. p. 2135. [3] Clavero, C., Plasmon-induced hot-electron generation at nanoparticle/metal-oxide interfaces for photovoltaic and photocatalytic devices. Nature Photonics, 2014. 8(2): p. 95-103. [4] Zheng, B.Y., et al., Distinguishing between plasmoninduced and photoexcited carriers in a device geometry. Nat Commun, 2015. 6: p. 7797. [5] McFarland, E.W. and J. Tang, A photovoltaic device structure based on internal electron emission. Nature, 2003. 421(6923): p. 616-618.

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CO2 sensing properties of Zr-added CaFe2O4-based sensor Yuki Obukuroa, Keisuke Mizutab, Kenji Obatab, Shigenori Matsushimab* a

Department of Materials System Engineering, National Institute of Technology (NIT), Kurume College, 1-1-1 Komorino, Kurume, Fukuoka 830-8555, Japan b Department of Creative Engineering, National Institute of Technology (NIT), Kitakyushu College, 5-20-1 Shii, Kokuraminami-ku, Kitakyushu 802-0985, Japan *Corresponding author: [email protected]

Abstract: CO2 sensing properties of Zr-added CaFe2O4-based sensor were examined in the temperature range of 250 to 450 °C under dry air condition. At 300 and 350 °C, the gas sensitivity of Zr-added CaFe2O4-based sensor to CO2 was estimated to be 2.9 times higher than that of the sensor made from pure CaFe2O4 powder. The 90% response time of the Zr-added CaFe2O4-based sensor was much shorter at 350 °C than that at 300 °C. Also, the Zr-added CaFe2O4based sensor responded reversibly as well as continuously to CO 2. Keywords: CO2 sensor, CaFe2O4, Zr addition, Upto 5 keywords

I. INTRODUCTION CO2 monitoring and/or control technologies have attracted much attention in the industry, office, home, agriculture, bio related field, and so on. To date, some kinds of CO2 sensors such as potentiometric [1, 2], amperometric [3, 4], resistive [5, 6], and capacitive [7, 8] types have been developed. As the CO2 detection by these sensors bases on acid-base reactions, the basic substances have been adopted as the sensing materials [9, 10]. Among these types of CO2 sensors, a resistive-type sensor using oxide semiconductor has attracted attention because the electric resistance change is directly related to CO2 concentration. However, the CO2 response of the resistive-type sensor is still low due to its gas sensing mechanism, i.e., the electric resistance change comes from gas adsorption on the surface of oxide semiconductor. Therefore, it is important to synthesize sensor materials with a high specific surface area [11, 12]. We have recently found that zirconium (Zr) addition into calcium ferrite (CaFe2O4) leads to characteristic porous structure connected into a three-dimensional network, resulting in a high specific surface area [13]. The porous structure is preferable as a resistive-type sensor material [14]. In the present study, we studied the sensing properties to CO2 of the Zradded CaFe2O4 material in detail. II.

complex. The Zr atoms were added to CaFe2O4 using Zr[OC(CH3)3]4. The amount of Zr was set at 1, 3, 5, 7, and 10 mol% with respect to Fe. Then, the mixed solution was dehydrated and heated on a hot plate to prepare the precursor powder of CaFe2O4. The precursor was calcined at 700 °C in air for 12 h to form CaFe2O4. Powder X-ray diffraction (XRD) measurements were performed to analyze the crystal phase of the prepared sample powders. 2.2.Measurement of the sensor properties The CaFe2O4-based powders were mixed with α-terpinol containing 5wt% ethyl cellulose, and the resulting paste was applied on an alumina tube attached to a pair of Pt-wire electrodes, as shown in Figure 1. The sensor element was heated at 600 °C in air for 2 h. The CO2 sensing properties were measured using a conventional gas flow system at temperature in the range of 250 to 450 °C. The CO2 concentration was varied in the concentration range of 0 to 5000 ppm by diluting pure CO2 gas with dry air. The gas sensitivity (S) was defined as Rair/Rgas, where Rair and Rgas were the electric resistances of a sensor element in air and in a sample gas, respectively.

EXPERIMENTAL

2.1.Sample preparation All reagents purchased from Wako Chemical Inc., Japan, and were used without further purification. In the 1:2:3 molar ratio, Ca(NO3)2·6H2O, Fe(NO3)3·9H2O, and malic acid were dissolved in ethanol to form a malic acid 271

Figure 1. Schematic drawing of CO2 sensor element.

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RESULTS

Unadded 1% Zr 3% Zr 5% Zr 7% Zr 10% Zr

Table. BET SSA

3.1.Zr-added CaFe2O4 powder Figure 2 shows the XRD patterns of Zr-added and unadded sample powders calcined at 700 °C in air. For the unadded powder, almost all of the diffraction peaks were ascribed to the CaFe2O4 phase, while for the Zr-added samples Ca2Fe2O5 phase as an impurity was observed. The scanning electron microscope (SEM) observation revealed that unadded CaFe2O4 powder consists of tightly interconnected grains and the morphology of each grain is irregular, as shown in Figure 3. On the other hand, when Zr was added to CaFe2O4, threedimensional network connecting of small grains formed to have porous structure. From the pore size distribution analysis by the Barrett-JoynerHalenda (BJH) method [15], it was found that the Zr-added CaFe2O4 powder has a large peak in the range of 10 to 40 nm and the representative pore size is around 22 nm (Figure 4). Also, the Brunauer-Emmett-Teller (BET) specific surface area of the Zr-added CaFe2O4 powder increased largely compared with the unadded material as inserted in Fig. 4 [16]. Amount of Zr 10 mol%

Zr / mol%

0.20

dVp/d log(rp) / cm3 g-1

III.

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0.15

SSA / m2 g-1 8.0 10.2 22.3 18.9 18.7 8.9

0.10

0.05

0.00

1

10

100

Pore radii (rp) / nm

Figure 4. Pore size distribution of Zr-doped CaFe2O4 powder calcined at 700 °C in air for 12 h.

3.2.Sensing properties of CO2 gas Figure 5 depicts the dependence of the gas sensitivity (S) and the 90% response time (t90) to 5000 ppm CO2 of the sensor made from Zr-added and pure CaFe2O4 at several temperatures. The CO2 gas response of the CaFe2O4 sensor was enhanced drastically by Zr addition. Among the Zr-added sensors examined, 5 mol% Zr-added CaFe2O4-based sensor showed the highest S at 300 and 350 °C. However, the t90 of the Zr-added CaFe2O4 sensor at 350 °C was much shorter than that at 300 °C. 3.8

Ca2Fe2O5

Unadded 1% Zr 3% Zr 5% Zr 7% Zr 10% Zr

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7 mol%

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Figure 2. XRD patterns of Zr-doped CaFe2O4 powder calcined at 700 °C in air for 12 h.

35 30 25

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(b) Figure 5. Gas sensitivity (a) and 90% response time (b) of Zr-added CaFe2O4 sensor in the temperature range of 250 °C to 450 °C.

Figure 3. SEM images of Zr-doped CaFe2O4 powder calcined at 700 °C for in air 12 h.

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Figures 6 (a) and 6 (b) show the response transients to stepwise changes in CO2 concentration and the relationship between the gas response and the CO2 concentration for 5 mol% Zr-added CaFe2O4. When the CO2 concentration was changed from 0 to 5000 ppm, the gas response finally reached S = 3.5. Each 90% response time for the stepwise changes in CO2 concentration was estimated to be within 90 s. The gas response showed a linear correlation with the logarithm of CO2 concentration in the range of 500 to 5000 ppm in the operating temperature of 250 to 450 ºC. 500 ppm air

Resistance / MΩ

100 kΩ

area, and the enhancement of oxygen-speciesassisted CO2 adsorption. In the near future, we are planning to consider the detailed mechanism. V. CONCLUSION In the present study, we found that 5 mol% Zradded CaFe2O4-based sensor has an excellent gas response to CO2 in air. The gas sensitivity, S of the 5 mol% CaFe2O4-based sensor was estimated to be 2.9 times higher than the pure CaFe2O4 sensor at around 300 ~ 350 °C. The 90% response time, t90 was much shorter at 350 °C than at 300 °C. The enhanced gas response of Zr-added CaFe2O4based sensor to CO2 can be attributed to its porous structure and high specific surface area compared with the pure CaFe2O4.

1000

ACKNOWLEDGMENT This work was partially supported by a Grantin-Aid for Scientific Research [Grant No. (C) 16K06782] and Mazda Motor Corporation [Grant No. 14KK-144].

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2.5

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[3]

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[4]

(b) Figure 6. (a) Transient response to stepwise changes in CO2 concentration in air at 350 °C, and (b) the relationship between the gas response and CO2 concentration for 5 mol% Zr-added CaFe2O4 powder in air at various temperatures.

IV. DISCUSSION It is known that CaFe2O4 is known as a p-type semiconductor, and its majority carriers are holes [17]. Therefore, it is expected that the reaction of adsorbed CO2 with a negatively charged oxide ion would bring about an increase in the hole concentration, as suggested from the IR measurements [14]. The addition of Zr is effective not only for increasing the surface area but also for enhancing the CO2 adsorption on CaFe2O4 surface. This means that the change in electric resistance caused by CO2 adsorption on the CaFe2O4 surface is enhanced by the mixed effect of Zr addition, i.e., the increment in the surface 273

[5]

[6]

[7]

[8]

[9]

M. Guthier, A. Chamberland, Solid-state detectors for the potentiometric determination of gaseous oxides, J. Electrochem. Soc., 124, 1579-1583 (1997). T. Maruyama, S. Sakai, Y. Saito, Potentiometric gas sensor for carbon dioxide using solid electrolytes, Solid State Ionics, 23, 107-112 (1987). J.-S. Lee, J.-H. Lee, S.-H. Hong, Solid-state amperometric CO2 sensor using a lithium-ion conductor, Sensor. Actuat. B-Chem., 89, 311-314 (2003). Y Yang, C.-C. Liu, Development of a NASICON-based amperometric carbon dioxide sensor, Sensor. Actuat. BChem., 62, 30-34 (2000). J. Tamaki, M. Akiyama, C. Xu, N. Miura, N. Yamazoe, Conductivity change of SnO2 with CO2 adsorption, Chem. Lett., 19, 1243-1246 (1990). T. Yoshioka, N. Mizuno, M. Iwamoto, La2O3-loaded SnO2 element as a CO2 gas sensor, Chem. Lett., 20, 1249-1252 (1991). T. Ishihara, K. Kometani, M. Hashida, Y. Takita, Mixed oxide capacitor of BaTiO3-PbO as a new type CO2 gas sensor, Chem. Lett., 19, 1163-1166 (1990). S. Matsubara, S. Kaneko, S. Morimoto, S. Shimizu, T. Ishihara, Y. Takita, A practical capacitive type CO2 sensor using CeO2/BaCO3/CuO ceramics, Sensor. Actuat. B-Chem., 65, 128-132 (2000). N. Mizuno, K. Kato, T. Yoshioka, M. Iwamoto, A remarkable sensitivity of CaO-loaded In2O3 element to CO2 gas in the presence of water vapor, Chem. Lett., 1683-1684 (1992).

The 12th Asian Conference on Chemical Sensors (ACCS2017) M.Y. Kim, Y.N. Choi, J.M. Bae, T.S. Oh, Carbon dioxide sensitivity of La-doped thick film tin oxide gas sensor, Ceram. Int., 38, S657–S660 (2012). [11] C. R. Michel, A. H. Martínez-Preciadoa, R. Parra, C. M. Aldao, M. A. Ponce, Novel CO2 and CO gas sensor based on nanostructured Sm2O3 hollow microspheres, Sensor. Actuat. B-Chem., 202, 1220–1228 (2014). [12] K. Fan, H. Qin, L. Wang, L. Ju, J. Hu, CO 2 gas sensors based on La1−xSrxFeO3 nanocrystalline powders, Sensor. Actuat. B-Chem., 177, 265-269 (2013). [13] Y. Obukuro, K. Obata, R. Maeda, S. Matsushima, Y. Okuyama, N. Matsunaga, G. Sakai, Formation of CaFe2O4 porous structure by addition of Zr in malic acid complex, J. Ceram. Soc. Japan, 123, 995-998 (2015). [10]

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K. Obata, K. Mizuta, Y. Obukuro, G. Sakai, H. Hagiwara, T. Ishihara, S. Matsushima, CO2 sensing properties of Zr-added CaFe2O4 powder with porous structure, Sensor. Mater., 28, 1157–1164 (2016). [15] E.P. Barrett, L.G. Joyner, P.P. Halenda, The determination of pore volume and area distributions in porous substances. I. computations from nitrogen isotherms, J. Amer. Chem. Soc., 73, 373-380 (1951). [16] S. Barunauer, P.H. Emmet, E. Teller, Adsorption of gases in multimolecular Layers, J. Am. Chem. Soc., 60, 309-319 (1938). [17] Y. Matsumoto, M. Obata, and J. Hombo, Photocatalytic reduction of carbon dioxide on p-type CaFe2O4 powder, J. Phys. Chem., 98, 2950-2951 (1994). [14]

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Study of interaction between Japanese Encephalitis Visus antigens and IgG antibody on basis of nanocomposite polyanilne/multi walled carbon nanotubes/manganese dioxide Chu Van Tuan*, Hoang Thi Hien, Tran Trung Hung Yen University of Technology and Education, Khoai Chau, Hung Yen, Vietnam *Corresponding author: [email protected]/[email protected] Abstract: Nanocomposite Polyaniline/ multi-walled carbon nanotubes/Manganese dioxide (PANi/MWCNTs/MnO2) directly on the interdigitated platinum micro-electrode for biosensors application. The polyaniline composite samples were tested by field-emission scanning electron microscopy (FE-SEM), Fourier-transform infrared (FT-IR), Ultraviolet–visible (UV-Vis) spectroscopy for identification of the composition of modified multi-walled carbon nanotubes and manganese dioxide (MWCNTs/MnO2) available on surface of polyaniline composites. In this study, we demonstrate the use of polyaniline composite as immobilization platform in the configuration of an electrochemical immunosensor for label free detection of Japanese encephalitis virus (JEV). The results were compared with corresponding data on pure polyaniline nanowires. The developed polyaniline composite-based electrochemical immunosensor is capable to detect the Japanese encephalitis virus with the detection limit about 01 pg/ml. Our obtained results from electrochemical cyclic voltammetry (CV) analysis also indicate that when the polyaniline composite is exposed to non-specific molecules, a negligible response is found, and there was no impacts to the specificity of the sensors applied for the virus detection. This work shows the potential use of polyaniline composite in electrochemical immunosensors for label free detection of other pathogens and small biomolecules. Keywords: Biosonsor, polyaniline, compostite, multi walled carbon nanotubes, manganese dioxide.

I. INTRODUCTION

Conducting polymers have attracted the attention of scientists worldwide since Alan Heeger, Alan MacDiarmid, and Shirakawa Hideki won the 2000 Nobel Prize in Chemistry [1]. Single conducting polymers are created through linked carbon pairs (-C=C-C=C-), which are alternating C-C and C=C connections in various structures, such as nanowires, nanotubes, and nano-thin films, to obtain larger surface areas and higher efficiency of sensors [2-4]. Combination with certain dopants creates additional advantages, such as high conductivities, larger specific surface areas, more environment-friendly features, higher stabilities, and rich applicability in optical devices and sensors [5-7]. Recently, combination of conducting polymers, such as polypyrrole (PPy) and polyaniline (PANi), with nanoinorganic materials produced hybrid materials with better specifications of conductivity, stability, and brittleness than single conducting polymers, leading to new promising applications. The newly created materials connect advantageous features of nanoinorganic materials distributed in continuous polymer beds [6,8], adjustment of orientations, and improvement of other conducting polymer specifications, including changes in electron structures of polymer chains (ΔRele), enhancement of electron transfer (ΔRhop), and 275

changes in conductivity between polymer chains (ΔRmed) [9,10]. Combining nanoinorganic materials with conducting polymers by ordinary blending methods is impossible because conducting materials are not naturally soluble and meltable. However, combination through electrochemical methods proved to be simple and easy in in-situ synthesis of hybrid materials on interdigitated electrodes for fabrication of sensors. This research project aims to develop a system of nanohybrid materials from three components, including PANi, in combination with nanoinorganic materials, such as nanoparticles (NPs), and metal oxides (MWCNTs/MnO2). These nanocomposite materials will open new research directions for environmental monitoring applications. We aim to enhance the main specifications (sensitivity, selectivity, and response time/recovery time) and reproducibility of sensors in meeting requirements of environmental monitoring of biosensors in rapid detection of pathogenic viruses II. EXPERIMENTAL Before every electro-chemical process, the surface of micro-electrodes gets treated in solution of K2Cr2O7/H2SO4 (saturated) and then electrochemically activated in a solution of 0.5 M H2SO4 at voltage range from -1.5 V to +2.2 V and scanning speed of 25 mV/s. In order to synthesize

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the hybrid PANi/MWCNTs/MnO2 material, it is first needed to synthesize MWCNTs/MnO2 by adding certain volume of MWCNTs to and, by supersonic method, diffusing it well in a MnSO4 solution and then remove all the water. Then, a synthesized solution of KMnO4 is dropped slowly at temperature of 60 0C, in supersonic conditions and for duration of 2 hours. The settled mixture gets cleansed to remove SO42- and then dried at temperature of 110 0C to obtain the MWCNTs/MnO2 mixture. Next, the hybrid PANi/MWCNTs/MnO2 material is synthetized by electrolytic method in a solution of LiClO4 0,1 M, pH = 3; 0,1 M aniline 98%; scanning speed of 0,1 mVs-1; scanning range of 0,00 ÷ 0,65 V; scanning cycles: 02 cycles. After electrolytic process, the micro electrodes get cleansed by deionized water and then dried at temperature of 80 o C. The structure of the obtained samples is analyzed by SEM equipment and its chemical composition is analyzed by FT-IR equipment. The electrodes, after having been covered by the nanocomposite PANi/MWCNTs/MnO2 by electrochemical method, get cleased by de-inonized water from 3 to 5 times and dried by nitrogen gas before being incubated with 100 µg/ml of IgG antigens in a solution of 0.2/0.2 M for duration of 3 hours. Then the electrodes get cleansed by a solution of PBS pH 7.0, positions not effectively bound on surface of electrodes being blocked with 2% BSA/PBS for 30 minutes and then cleansed by PBS pH 7.0 and get dried in air. The investigation process of sensitivity features of sensors are conducted within 48 hours after the completion of preparation of samples in order to get the best experiment results and to receive well indicating comparison factors. electrochemical cyclic voltammetry (CV) evaluation, response the line, electrochemical impedance spectroscopy are measured by AutoLab electro-chemical systems at ambient temperature by using the electro-chemical system of 3 Pt counter electrodes, Ag/AgCl reference electrodes where working electrodes are sensors with IgG antibodies by covalent method. Then sensors get incubation for 45 minutes by

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JEV antigens, being subject to investigation concentration. In this study, we investigated the interaction between JEV antigens and IgG antibodies in a buffer solution of PBS 0.02 M containing KCl 0.1 M by electrochemical cyclic voltammetry. III. RESULTS AND DISCUSSION Fig. 1 is the result of SEM analysis of the shape anf disytibution of PANi/MWCNTs and PANi/MWCNTs/MnO2 wires when being covered on surface of electrodes. CNTs wires (Fig. 1a) arfe distributed almost evenly in PANi blocks. Fig. 1b is the result of analysis of PANi/MWCNTs/MnO2 nanocomposite obtained by CV method. The results show well the white deposition of MnO2 and their spheric form cristals with bound different which cover PANi/MWCNTs films. This structure of covering layers provides a very large specific surface. With this amorphous structure, the arrangement and the bound between molecules and macromolecular circuit are not tough which lead to an increase of gas absorption/disabsorption capacity in certain isothermal conditions. The gas absorption/dis-absorption capacity and sensibility depends also on dopant composition which change the surface structure of composites. In this report we use PANi with some added MWCNTs/MnO2 component for synthesizing process. The results of SEM analysis show the smaller size of CNTs wires distributed in PANi blocks bound on microelectrodes and the spherical form blocks of MnO2 covering PANi blocks. The polymers themselves are soluble but Cl- ions in the solution of LiClO4 create bridges to bind PANi which lead to higher possibility of polarization then to a better distribution of CNTs in the network of PANi wires. The film obtained when CNTs get bound on surface of PANi wires have a particular porous, evenly distributed and deep structure. This structure attracts a special attention of research and are found highly suitable for application in biosensors.

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Figure 1. FE-SEM images of (a) PANi/MWCNTs, (b) PANi/MWCNTs/MnO2

For confirmation of existence of PANi, PANi/ MWCNTs and PANi/MWCNTs/MnO2, Fig. 2 shows the UV-Vis spectrum observed in band of 200  800 nm. The differently obtained absorption intensity of spectrum reflects the strong-weak absorption peaks. The absorption optical band at 200-360 nm reflects the -* transfer in the benzoid/quinoid cycle structure which fit the form of emeraldine salt of PANi obtained in [11,12]. PANi exhibit clearly two quarter peaks at 269nm và 319 nm, and PANi/MWCNTs exhibit three medium peaks at 319 nm, 345 nm, 256 nm. Particularly we observe the absorption peak of bipolaron state shifting towards longer waves, namely in direction from PANi through PANi/MWCNTs to PANi/MWCNTs/MnO2 then the energy reduces in this direction and the bipolaron mobility increases and also the conductivity of obtained composites increases in this order. 0.9

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The obtained PANi/MWCNTs/MnO2 nanocomposite was processed also by FT-IR method. The result of this analysis in presented in Fig. 3. The FT-IR analysis results were reported in 277

a previous report [13]. Similarly to the case of PANi and PANi/MWCNTs, the shift of the band from 1600 cm-1 to 1500 cm-1 which are typical vibrations for non-symmetric C6 rings of quinoid and benzoid forms of PANi [14-16]. The form intensity rate of (benzoid/quinoid) is 12 show that the addition of dopant components leads to transfer of part of quinoid rings to benzoid rings (higher number of benzoid rings and lower number of quinoid rings) and then to higher electric conductivity of the films. This change of density includes the change of emeraldine and permegraniline components to emeraldine salt which is coupled with protonization process due to the transfer of protons from Mn6+. This process gets pushed up by the increase of H+ concentration in the solution. Nevertheless, a too high H+ concentration also reduces the volume of emeraldine salt due to the re-combination of H+ and X- of emeraldine salt which leads to a recreation of quinoid rings. The increase of absorption band is concentrated at 3133.71 cm-1 which is specific for N-H in PANi networks, and the one at 2363.86 cm-1 (Fig. 3) which is specific for NH2+ in –C6H4-NH2+-C6H4- [17,18], show well the high rate of oxydization process and lead to a creation of a big amount of emeraldine salt. More than that, the creation of NH2+ groups break the electron pairs of Nitrogen atoms which leads to a creation of positive electric positions. This may increase the movement of single electrons between polaronic positions which create the polaronic network. The C-N extended vibration ranges of secondary amine benzoid forms are also observed in the band range of 1200-1350cm-1 (Fig. 3). The vibration peak at 1300.06 cm-1 and 1117.91 cm-1 respectively are assigned to the consequense of extended C-N+ effects the derivative amine forms [14,19,20] and extended C-N+ • [20-22], they being created during the whole protonization process of PANi chains.

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Figure 3. Typical FT-IR spectra of PANi/MWCNTs/MnO2 nanocomposite.

In this initial stage, the research team conducted the study of electro-chemical properties of bio-sensors by CV method on basis of PANi/MWCNTs/MnO2 nanocomposites in a BPS buffer solution for two cases: i) absence of JEV antigens, and ii) 01 pg of JEV antigens added to the electro-chemical system. The results show a clear change. The presence of coupling between IgG antibodies and JEV antigens makes the oxidization signal peak reduce (Fig. 4).

Figure 4. The cyclic voltammogram of biosensors (a) PANi/MWCNTs/MnO2, (b) PANi/MWCNTs/MnO2 + JEV

From the above noted results show, the presence of JEV antigens reduces the current intensity. This fact demonstrates that under the absorption of JEV containing antigens into surface 278

of PANi/MWCNTs/MnO2 nanocomposites on Pt electrodes, PANi/MWCNTs/MnO2 nanocomposites search and coupled with the virus antigens in solution. However, the rate of reduction of current density is relatively low then further studies of spectral bands are required to get full information of the coupling process of antigens/antibodies. IV. CONCLUSION PANi/MWCNTs/MnO2 nanocomposites had been synthesized by electro-chemical method. The surface structure of PANi/MWCNTs/MnO2 had been analyzed. A high level of uniformity and porosity of the structure leads to high bio compatibility. The UV-Vis and FT-IR spectral analysis showed a relative high conductivity of PANi/MWCNTs/MnO2 nanocomposites. The analysis showed well that PANi/MWCNTs/MnO2 nanocomposites successfully synthesized by the research team are found suitable for fabrication of bio-sensors for fast detection of pathogenic viruses which have a simple fabrication procedure and require no expensive markers, chemical or bio masses. ACKNOWLEDGMENT The current work was financially supported by the research project of Vietnam Ministry of Education and Training under code B2017-SKH03.

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REFERENCES [1] This year’s Nobel prizes for Physics and Chemistry, Meterials Today, 10 (12) (2007) 67. [2] Seon Joo Park, Oh Seok Kwon, Ji Eun Lee, Jyongsik Jang, and Hyeonseok Yoon, Conducting PolymerBased Nanohybrid Transducers: A Potential Route to High Sensitivity and Selectivity Sensors, Sen. (Basel)., 14(2) (2014) 3604-3630. [3] Hyeonseok Yoon, Current Trends in Sensors Based on Conducting Polymer Nanomaterials, Nanomaterials, 3 (2013) 524-549. [4] Abdulla S, Dhakshanamoorthi J, Dinesh VP and Pullithadathil B, Controlled Fabrication of Highly Monodispersed, Gold Nanoparticles Grafted Polyaniline (Au@PANI) Nanospheres and their Efficient Ammonia Gas Sensing Properties, Biosens. Bioelectron., 6(2) (2015) 1000165. [5] Mihaela Baibarac, Pedro Gómez-Romero; Nanocomposites Based on Conducting Polymers and Carbon Nanotubes from Fancy Materials to Functional Applications, J. Nanosci. Nanotech., 6 (2006) 1-14. [6] Shaohuang Weng, Jianzhang Zhoua, Zhonghua Lina (2010), Preparation of one-dimensional (1D) polyaniline–polypyrrole coaxial nanofibers and their application in gas sensor, Syn. Metal., 160 (2010) 1136-1142. [7] D. Li, J.X. Huang, R.B. Kaner, Polyaniline nanofibers: aunique polymer nanostructures for versatile applications, Acc. Chem. Resear., 42 (2009) 135-145. [8] J. Wilson, S. Radhakrishnan, C. Sumathi, V. Dharuman (2012) Polypyrrole–polyaniline-Au (Ppy-PANi-Au) nano composite films for label-free electrochemical DNA sensing, Sens. Actuators B., 171-172 (2012) 216 - 222. [9] Hoang Thi Hien, Ho Truong Giang, Tran Trung, Chu Van Tuan, Elaboration of Pd-nanoparticle decorated polyaniline films for room temperature NH3 gas sensors, Sens. Actuators B., 249 (2017) 348 - 356. [10] P. Cavallo, D.F. Acevedo, M.C. Fuertes, G.J.A.A. Soler-Illia, C.A. Barbero, Understanding the sensing mechanism of polyaniline resistivesensors, Effect of humidity on sensing of organic volatiles, Sens. Actuators B., 210 (2015) 574 - 580.

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[11] C.Barbero, M.C. Miras, B.Schnyder, O. Haas, R. Kotz, Sulfonated polyaniline films as cation insertion electrodes for battery applications. Part 1-Structural and electrochemical characterization, J. Chem.Mater., 4 (1994) 1775-1783. [12] J.L.Bredas, Conjugatied Polymers and Related Materials, Ed, by W.R.Salaneck, I.Lunstrom, B. Ranby, Oxford University Press, NewYork (1993) P.195. [13] Hoang Thi Hien, Ho Truong Giang, Tran Trung, Chu Van Tuan, Enhancement of biosensors performance using polyaniline/multiwalled carbon nanotubes nanocomposites, J. Mater. Sci., 52 (2017) 1694-1703. [14] J. Tung, X. Jing, B. Wang, F. Wang, Infrared spectra of soluble polyaniline, Synth. Met., 24 (1988) 231-283. [15] Y. Cao, Spectroscopic studies of acceptor and donor doping of polyaniline in the emeraldine base and pernigraniline forms, Synth. Met., 35 (1990) 319-332. [16] Z.Ping, In situ FTIR–attenuated total reflection spectroscopic investigations on the base–acid transitions of polyaniline. Base–acid transition in the emeraldine form of polyaniline, J. Chem. Soc., Faraday Trans., 92 (1996) 3063-3067. [17] L. Lizarraga, E. M. Andrade, F. V. Mohna., Swelling and volume changes of polyaniline upon redox switching, J. Electroanal. Chem., 561, 127-135 (2004) [18] Y. Furukawa, F. Ueda, Y. Hyodo, J. Harada, T.Nakajima, T.Kawagoe, Vibrational spectra and structure of polyaniline, Macromolecules, 21 (1988) 1297-1305. [19] H. Neugebaner, In situ vibrational spectroscopy of conducting polymer electrodes, Macromol. Symp., 94 (1995) 61-73. [20] S. Quillard, G. Louarn, J. P. Buisson, M. Boyer, M. Lapkoeski, A. Pron, S. Lefrant, Vibrational spectroscopic studies of the isotope effects in polyaniline, Synth. Met., 84 (1997) 805-806. [21] A.A. Athawale, V.V. Chabukswar, Acrylic acid doped polyaniline sensitive to ammonia vapours, J.App. Polym., 79 (2001) 1994-1998. [22] J. Stejskal, L. Sapurina, M. Trehova, J. Prokes, L. Krivka, E. Tobolkova, Solid-State Protonation and Electrical Conductivity of Polyaniline, Macromolecules, 31 (1998) 2218-2222.

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Study on the ability to measure dissolved H2 gas in transformer oil using resistive sensor based on SnO2 thin film sensitized with microsized Pd islands Nguyen Thi Hue1, Nguyen Van Dua3, Hoang Van Phuoc1, Nguyen Thi Lan Huong1, Nguyen Van Toan2, Hoang Si Hong*1 1

School of Electrical Engineering (SEE), Hanoi University of Science and Technology (HUST), Viet Nam International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, Viet Nam 3 Center for MicroElectronics and Information Technology (IMET), C6 Thanh Xuan Bac, Thanh Xuan, Ha Noi *Corresponding author: [email protected]

2

Abstract: Hydrogen dissolved in transformer oil is an important gas in diagnosing and detecting failure of the transformer. In this study, our group fabricated H2 gas sensor and experimental model of transformer oil chamber. The H2 sensor consists of a micro-heater, electrodes and SnO2 sensitive layer. The sensitive layer is designed with small thickness (tens of nm). Especially, it is covered by Palladium (Pd) islands as catalysts that increase the sensitivity of sensor. Then transformer oil measuring system composes of an oil chamber, oil temperature controller, H2 gas flow controller and H2 concentration measuring instrument. The sensor is utilized for testing fabricated H 2 gas sensor. The experiments show that the sensor can detect H2 gas in range of concentration of 0 – 1200 ppm with 40 seconds of response time. Keywords: DGA (Dissolved gas analysis), Pd catalyst islands, SnO2, transformer oil

I. INTRODUCTION Recently, research on sensors that measure concentration of dissolved gases in the transformer oil are very necessary. Those dissolved gases are generated by thermal decomposition of oil at high temperatures or partial discharging in transformer oil. Results of measurement are significant important to diagnose the failure of transformer as soon as possible. Between many different dissolved gases such as hydrocarbons (CmHm), carbon oxides (COx), nitrogen oxides (NOx), and hydrogen (H2), the detection of H2 gas is the most important because the concentration of dissolved H2 varies at different levels of faults in the transformer [1-2]. There are some methods to solve above problem. Yang Dingkun and partners used PAS method (Photo Acoustic Spectroscopy). The concentration of dissolved gases is analyzed through their photo-acoustic spectrum after absorbing infrared light energy [3]. Recently, Emir ŠIŠIĆ introduced gas chromatography method to measure the amount of dissolved gases in transformer oil [4]. Other groups developed DGA (Dissolved Gas Analysis) device applied electrochemical method. When gas concentration varies, gas sensitive layer exposing to tested gases leads sensor resistance to change [5-8]. Among these methods, gas chromatography method brings out the result with high accuracy. However, the price and time consuming are much higher than the others. The photo acoustic spectroscopy method 280

has advantages of wide range, rapid response. On the other hand, its disadvantages are high fee, external other gases and vibration of transformer effect [9]. Additionally, good points of method using solid state H2 gas sensor are simple structure, low price, small size, maintenance convenience and long-term operating. Several substances usually used to fabricate H2 sensor are Pd [7-8], ZnO, SnO2… Groups of A.S.M. Iftekhar Uddin applied resistivity – type sensor structure based on palladium (Pd) - decorated zinc oxide (ZnO) nanorod (NR) array [5]. Besides, Jerzy Bodzenta and partners fabricated sensor to detect concentration of H2 from 200 ppm – 1500 ppm in the transformer oil by optimizing Pd thin film [8]. In this study, we fabricated H2 gas sensor dissolved in transformer oil using SnO2 thin film. It has many advantages such as rapid response, low price of material and easy controllable catalyst thickness in fabrication process. Technology our group utilized allows to streamline production. Pd catalysts are lifted by nanorods on SnO2 sensitive layer. They are designed to be separated round membranes instead of a complete one. This kind structure assures catalyst layer to be sturdy and stable, to avoid the breakage on surface of complete membrane that changes the properties of membrane when affected by working environment: vibration, air pressure… And using Palladium catalyst islands increases H2 gas sensitivity of SnO2 membrane. In addition, Pd

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thickness can be controlled and adjusted to accomplish maximum sensitivity of the sensor. II.

EXPERIMENTAL

A. The dissolved hydrogen gas in transformer oil measuring system using fabricated sensor The diagram of measuring system using H2 gas sensor is described in Figure 1. The system consists of a number of main parts: H2 sensor, a chamber, pressure indicator, temperature sensor, heating controller, mass flow controller (MFC), stirring motor, measuring devices and PC. Among them, element that plays an important role in measuring concentration of dissolved hydro gas in oil is H2 sensor. This sensor is a type of thin film gas sensors based on resistance variation. Sensor directly exposures to oil. The sampled oil is stored in a chamber. It ensures the operating space for the equipment. Chamber must be airtight, sturdy and free of rust and chemical reaction with oil. In addition, to obtain the nearest working condition as in real transformer where temperature must be under 900C to avoid reducing quality of the insulation of transformer [10], our group utilizes a heating controller with a heater to stabilize the temperature in the chamber. We also use a pressure indicator to monitor inside-chamber pressure and to assure safety issues. The temperature sensor put into oil of the chamber gives a feedback to help heating controller generate control signal more correctly. Besides a set of MFCs is used to adjust the amount of dissolved gas in oil to the desired level, which is corresponding to the actual level in the real transformer. Output of MFCs set is connected to the bubbling conduit in order to make the gas dissolve as quick as possible into the oil. Similarly, stirring motor helps enhance H2 dissolving process in oil. However, it must ensure fire and explosion safety in case of prolonged exposure to combustible gases. Signal from sensor is measured by resistance measuring devices. After that the data is continuously sent to PC for calculating concentration of H2 gas dissolved in transformer oil, storage and supervision. As mentioned in section A, fabricating H2 gas sensor working in transformer oil is vital. This is one of the work that our group has to implement from the beginning. The kind of sensor that we are made is becoming popular. The complete structure of hydrogen gas sensor in transformer oil is illustrated in Figure 2. Sensor has 3 main parts: a micro heater made of Chromium/Platinum is distributed around two platinum electrodes, these electrodes are covered 281

Figure 1. Measuring system diagram

B. Hydrogen gas sensor fabrication

Figure 2. Structure of gas sensor based on MEMS technique

by Palladium catalyst island on SnO2 gas sensitive thin film. Using Platinum micro-heater assures the stability of the sensor when it works in high temperature condition. All of the processes such as treating blade, oxidizing blade, photolithography, sputter, eroding,... were implemented in clean room of International Training Institute for Materials Science (ITIMS). The detailed experimental process was performed in our previous research [11].

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Figure 3. Device combining chamber with controller, stirring motor and pressure indicator, a) Front side b) Back side

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C. Chamber and Controller To save the space of system and to build up a sound architecture for reliably, stably and safely working, our group combined chamber with pressure indicator, stirring motor, heater and heating controller. Figure 3 indicates the image of designed real device. According to that, stirring motor is on the top of the device. The pressure indicator is placed under the stirring motor and is mounted on the lid of the chamber. The lid keeps chamber highly airtight. The chamber is located on top of the heater taken over by the controller which is protected by an aluminum cover contacting the flat surface. The heating controller using PID algorithm has to fulfill less than 10% overshooting of quality criteria due to slow response of thermal process and natural air cooling so that the temperature of chamber can reach the set value in a shortest time. There are two valves. One allows to direct gas flow into and one allows to direct oil flow into the chamber. Another valve on the back of the device is used to discharge oil from chamber. On the front view of the device, there is a switch to turn the device on or off. A knob is used to adjust speed of motor. Next to the knob, there is a digit screen that lets user monitor real and set temperature of the chamber and choose operating mode of controller. On the backside of the device connectors are distributed to supply electrical source, to send data from controller to PC and to transfer the control signal to stirring motor. III.

RESULTS AND DISCUSSION

A. Result of H2 gas sensor fabrication Successfully fabricated sensor is investigated about morphology and structure by FESEM and EDX spectroscopy.

Figure 1. FESEM snapshot of SnO2 thin film with catalyst island

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Figure 2. EDX spectrum of SnO2 thi-film sensor with Pd catalyst island

Figure 4 is a FESEM snapshot of a SnO2 thin film sensor with catalyst island. The islands has round shape, diameter of 5 μm and are regularly distributed as designed. The EDX spectrum of SnO2 thin film sensor with Pd catalyst islands is shown in Figure 5. The components of the sample are mainly Pt, Sn, Oxi and Pd. The sample contains no impurities. The top of the appearance of Pd material shows that the produced catalyst island is Pd. The highest peak of Pt performs that Pt has a large percentage of mass because the Pt electrode has a much larger thickness than that of thin film and catalyst island. B. Sensor response Experiment Completely fabricated sensor is tested with different temperature. The change of resistance of sensor without influence of H2 gas is revealed in Figure 6. Resistance of the sensor is decreased due to absorption of water and transitions O- → O2-, O2→ O- [12]. Figure 7 performs the change in resistance of output of the sensor in oil of the transformer when concentration of H2 dissolved gas is in range of 0 – 1200 ppm. The temperature heating the sensor comes from 100oC of transformer oil sourced by external controllable heater and over 200oC caused by a current of 0.059 A going through micro – heater. The result is explained by H2 sensitive principle of SnO2 thin film sensor. It is the change of surface conductivity following oxygen absorption mechanism. Elements (O2-, O2= and O-) on the surface of SnO2 layer trap its electrons to form poor electron layer. That results in increasing potential barrier and resistance of the surface.

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Figure 3. Resistance of sensor without effect of H2 gas at different voltage sourcing into the heater in transformer oil at 100oC

Figure 8. Practical measuring system

Figure 4. Result of measurement in transformer oil

stirring motor, measuring output of gas sensor, sending data to PC and processing, storing the received data and drawing characteristic on PC. The practical system is shown in Figure 8. H2 gas was injected into oil chamber and flow of this gas is controlled by MFCs (Mass Flow Controllers). H2 gas sensor was put near holes on gas conduit where H2 is quickly dissolved when exposing to transformer oil. Output of the sensor was retrieved by measuring device. After that the result was sent to PC for evaluating, storage and monitoring. The temperature of chamber was controlled by a heater and set manually. The set and feedback temperature were displayed on digit screen. The motor stirred regularly to increase exposure area between gas and oil.

When exposing to H2, absorbed oxygen on the surface reacts with H2 and returns electrons to SnO2 membrane, potential barrier will reduce and causes the reduction of resistance of the thin film. Reaction equation: H2(gas) + O- (absorbed)→H2O(gas) + eOn the other hand, Pd is able to absorb H2 gas [13]. When H2 stream reaches the surface of the sensor, H2 molecules are split into single atoms by Pd catalyst island. Then hydro single atoms are absorbed and caught into crystal lattice structure of Pd by Pd molecules. Pd (solid) + x/2 H2(gas) → PdHx (solid) C. Overview of the whole system After fabricating H2 gas sensor in transformer oil and designing chamber integrated with temperature controlling system, pressure indicator and stirring motor, our group implemented to connect all parts of the whole system to operate every work completely including controlling temperature, 283

IV. CONCLUSION In this study, we fabricated H2 gas sensor with SnO2 sensitive layer and Pd catalyst island. And our group designed and built up a system that includes chamber illustrating practical oil transformer, measuring instruments, the fabricated H2 gas sensor and gas controllable supplier with mass flow controller. Experimental result using system model of transformer oil shows that sensor can detect H2 in range of H2 gas concentration of 0 – 1200 ppm dissolved in transformer oil with 40 seconds of response time. ACKNOWLEDGMENT This research is funded by the research project of Vietnam Ministry of Education and Training under code B2015-01-92.

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REFERENCES [1]

[2]

[3]

[4] [5]

[6]

[7]

[8]

Shudi Peng, Gaolin Wu and Qian Wang, SnO2 Nanofibers Gas Sensor Detecting H2 Dissolved in Transformer Oil, Advanced Materials Research, Vols. 706-708 (2013), pp 1008-1011 Igor Pavlovsky, Hydrogen Sensor for Oil Transformer Health Monitoring, nanotechnology, 2008. nano '08. 8th ieee conference on, IEEE, 2008, pp 211-213, ISBN: 9781-4244-2103-9 Yang Dingkun,Chen Xingang,,Ma zhipeng, Fault detection of transformers based on Raman spectra of the dissolved gas in transformer oil, 2016 IEEE 8th International Power Electronics and Motion Control Conference. Emir ŠIŠIĆ, Chromatographic analysis of gases from the transformer, transformers magazine, Volume 2, Issue 1 A.S.M. Iftekhar Uddin, Usman Yaqoob, Gwiy-Sang Chung, Dissolved hydrogen gas analysis in transformer oil using Pd catalyst decorated on ZnO nanorod array, Sensors and Actuators B, 226(2016), pp 90-95 Anjali Chatterjee, Rajat Sarkar, Nirmal K. Roy, Pathik Kumbhakar, Online monitoring of transformers using gas sensor fabricated by nanotechnology, International Transactions on Electrical Energy Systems, 2013 Fan Yang, Dongoh Jung, and Reginald M. Penner, Trace Detection of Dissolved Hydrogen Gas in Oil Using a Palladium Nanowire Array, Anal Chem. 2011, 83(24):9472-7, doi: 10.1021/ac2021745

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Hanoi, 2017 Jerzy Bodzenta, Bogusław Burak, Zbigniew Gacek, Wiesław P. Jakubik, Stanisław Kochowski, Marian Urban´czyk, Thin palladium film as a sensor of hydrogen gas dissolved in transformer oil, Sensors and Actuators B, 87 (2002), pp82–87 Norazhar Abu Bakar, A. Abu-Siada and S. Islam, A Review of Dissolved Gas Analysis Measurement and Interpretation Techniques, IEEE Electrical Insulation Magazine, Volume: 30, Issue: 3, 2014, pp39-49 Radu Godina, Eduardo M. G. Rodrigues, João C. O. Matias and João P. S. Catalão, “Effect of Loads and Other Key Factors on Oil-Transformer Ageing: Sustainability Benefits and Challenges”, energies, ISSN 1996-1073, 2015. Nguyen Van Toan, Nguyen Viet Chien, Nguyen Van Duy, Hoang Si Hong, Hugo Nguyen, Nguyen Duc Hoa, Nguyen Van Hieu, Fabrication of highly sensitive and selective H2 gas sensor based on SnO2 thin film sensitized with microsized Pd islands, Journal of Hazardous Materials, 301 (2016), pp433-442 O.V. Anisimov, N.K. Maksimova, E.V. Chernikov, E.Y. Sevastyanov, N.V. Sergeychenko, The Effect of Humidity and Environment Temperature on Thin Film Pt/SnO2: Sb Gas Sensors, Siberian Conference on Control and Communications SIBCON-2007 Shen, Y.; Yamazaki, T.; Liu, Z.; Meng, D.; Kikuta, T. “Hydrogen sensing properties of Pd-doped SnO2 sputtered films with columnar nanostructures”, Thin Solid Films, 517 (2009) 6119–6123.

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Effect of nanosilica content and accelerated weather testing on some properties and morphology of Polyoxymethylene/silica nanocomposites Tran Thi Mai1, 2*, Nguyen Thi Thu Trang1, Nguyen Thuy Chinh1, Dang Thi Thanh Le2, Thai Hoang1* 2

1 Institute for Tropical Technology, VAST, No. 18, Hoang Quoc Viet Str., Cau Giay dist., Ha Noi, Vietnam International Training Institute for Materials Science, HUST, No. 1, Dai Co Viet Str., Hai Ba Trung dist., Ha Noi, Vietnam *Corresponding author: [email protected] and [email protected]

Abstract: This paper presents some properties and morphology of nanocomposites based on polyoxymethylene (POM) and nanosilica (NS) with different content before and after accelerated weather testing. The FTIR spectra of POM, NS and POM/NS nanocomposites showed the appearance of characteristic peaks of POM and NS in the nanocomposites. Carbonyl index (CI) of POM before and after accelerated weather testing were rose up from 0.96 to 1.43 corresponding to increase of C=O group content in the POM matrix. When the NS content was grown up from 0.5 to 2 wt.%, the CI of nanocomposites had tendency to drop due to NS particles inhibited the decomposition of POM. The results of tensile strength, elongation at break of POM/NS nanocomposites indicated that the samples had been decomposed by ultraviolet (UV) radiation and photooxidation degradation of macromolecules of PM during accelerated weather testing. The tensile strength, elongation at break and Young modulus of POM/NS nanocomposites were larger than those of POM, and they were increased when rising NS content from 0 to 1.5 wt.%. The retention of tensile strength and elongation at break of POM/NS nanocomposites were reduced significantly while their Young modulus less decreased after accelerated weather testing. The dielectric constant, dielectric loss tangent and volume resistivity of the nanocomposites were reduced after testing. Besides, the dielectric constant and dielectric loss tangent of the nanocomposites after testing were increased with rising NS content from 0 to 2 wt.%. Contrary, volume resistivity of POM/NS nanocomposites after testing was reduced with rising NS content from 0 to 2 wt.%. SEM images of the nanocomposites displayed the appearance of cracks on the surface of samples after testing. The cracks number was decreased and the cracks size of become smaller and less deeper when increasing NS content to 2 wt.%. Keywords: Polyoxymethylene, nanosilica, carbonyl index, dielectric properties, morphology

INTRODUCTION Polymer composites used in the automotive industry are mostly affected by photochemical reaction when subjected to severe weather condition [1-2]. The photochemical reaction is also referred to as photodegradation. In photodegradation process, the strength of the polymers is being affected which may be due to excessive UV penetration and thermal oxidation [3-4]. I.

Polyoxymethylene (POM) is known as polyacetals (acetal), a highly crystalline highperformance engineering thermoplastic polymer. Its advantages are low coefficient of friction, excellent wear resistance, high modulus, high strength, stiffness coupled with good impact strength and resistance to many solvents and automotive fuel [5]. POM is widely used in mechanic, automotive, and electric-electronic industries [6-8]. Because of their practical application, polyacetals are stabilized against oxidation and other environmental influences such as UV irradiation. Nanosilica (NS) is an inorganic additive, which had outstanding properties for some 285

polymers such as high tensile strength, small expansion coefficient, high reflexes of UV light, high surface activity and so on. It is popularly used in preparation of paints, coatings, plastic, rubber, adhesives [9-12]. Recently, the studies on the nanocomposites of POM/carbon nanotubes and POM/hydroxyapatite shown that the tensile, thermal and electric properties of the nanocomposites was improved by these nanoadditives [13-15]. Sirirat et al. [16] had studied the influence of particle size of ZnO on morphology, mechanical and thermal properties of POM/ZnO nanocomposites. POM/ZnO nanocomposites with varying concentration of ZnO were prepared by a melt mixing technique in a twin screw extruder. Afshin et al. investigated the tensile behavior of POM/CaCO3 particulate nanocomposites and the mechanisms of the plastic deformation of nanocomposites [17]. Zhao and Ye indicated that the nano graphite well dispersed into POM matrix. The effect of the type and the content of the graphite, the nature of the coupling agents used in the graphite modification on the properties of the composites were studied [18]. From the literature review, it can be seen that the

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above works did not mention the influence of the NS content or/and accelerated weather testing on some properties and morphology of POM/NS nanocomposites. In this paper, we have presented the effect of NS content and accelerated weather testing on properties and morphology of POM/NS nanocomposites. The decomposed mechanism and the change of their characteristics, properties based on FTIR spectra, retention tensile properties and dielectric properties, morphology after testing are investigated and discussed. II.

EXPERIMENTAL

2.1. Materials Polyoxymethylene (code F20-03) was supplied by Korea Engineering Plastics Co., Ltd (Korea) with the density of 1.41 g/cm3, melt flow index (MFI) of 9 g/10 min. Nanosilica (NS) powder with particle size about 12 nm was supplied by SigmaAldrich Co. (USA). 2.2. Preparation of POM/NS nanocomposites POM and NS particles were dried at 80 oC in vacuum for 4 hours. Then, nanocomposites based on POM and 0.5 – 2 wt. % NS (compared with total weight of two components) were prepared by melt mixing in the Haake Rheomixer (Germany) at 190oC for 5 minutes and rotor speed of 60 rpm. After melt mixing, the nanocomposites were molded by hot pressured machine (Toyoseiki, Japan) at 190oC, pressing pressure of 12-15 MPa for 2 min. The sample in sheet sharp was allowed to cool and be stored at room temperature for 48 hours before determining its properties and morphology. These samples were denoted POM, POM/0.5 NS, POM/1 NS, POM/1.5 NS and POM/2 NS corresponding to NS content of 0, 0.5, 1, 1.5 and 2 wt.%, respectively. 2.3. Accelerated weather testing Accelerated weather testing of POM and POM/NS nanocomposites were carried out on UV condensation weather device (Atlas UVCON model UC-1, USA) at Institute for Tropical Technology, Vietnam Academy of Science and Technology (VAST) according to D 4329-99 ASTM as follows: time lighting for UV ray is 8 hours at 60 oC and then moisture condensation is 4 hours at 50 oC. The time total of accelerated weather testing for all samples is 168 hours [19]. The source of UV radiation is 8 lamps UVB – 313 (maximum wavelength of 313 nm). After finishing, the samples were stored at room 286

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temperature for at least 24 hours before determining its properties and morphology. 2.4. Determination of characteristics, properties and morphology A Nicole/Nexus 670 Fourier Transform Infrared spectrometer (USA) had been used for the measurements of FTIR spectra at room temperature as follows: 16 scan with 8 cm-1 resolution and wave number ranging from 400 to 4000 cm-1. Tensile properties (Young modulus, tensile strength and elongation at break) of the nanocomposites were determined on Zwick Tensile 2.5 Machine (Germany) according to ASTM D638 at Institute for Tropical Technology, VAST. Dielectric properties (dielectric constant, dielectric loss tangent and Volume resistivity) of the nanocomposites were tested on Agilent instruments model E4980A (Japan) with the 16451B test fixture for solid materials according to ASTM D150 at Institute for Tropical Technology, VAST. Scanning electron microscopy (SEM) was used to study the morphology of the impact fracture surfaces of the POM and POM/NS nanocomposites. All specimens were coated with platinum before SEM study. Weather durability of the nanocomposites was calculated by the retention percentage of tensile properties of the nanocomposites after accelerated weather test. III.

RESULTS AND DISCUSSION

3.1. FT-IR spectra FTIR spectra of POM and POM/NS nanocomposite using 1.5 wt. % NS content before and after accelerated weather testing were displayed in figure 1. In the FTIR spectrum of POM before and after testing, some peaks characterized for stretching and bending vibrations of C=O, C-O, C-H2, O-H groups were found (figure 1a). For example, C=O group stretching at 1736.6 cm-1, C-O group stretching at 1280.3 cm-1, C-H2 group bending at 1470 cm-1 and O-H group at 3744 cm-1 [6]. It can be seen that after testing, the absorption peaks of nanocomposites corresponding to C=O, C-H2 and O-H groups had absorption intensity higher than those in the nanocomposite before testing. The spectra of FTIR of all nanocomposites using different NS contents were similar to the POM/1.5 wt.% NS nanocomposite so would not be shown. The FTIR spectra of POM/NS nanocomposite before and after testing performed the characteristic peaks of POM and NS such as

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asymmetric and symmetric stretching of Si−O group at 1082.11 and 795 cm-1, O-H group at 3442 cm-1 and Si-OH group at 955.1 cm-1 [11].

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absorption expressed the photo-oxidation degradation process takes place is corresponding to the group carbonyl (C=O). Previous studies have assigned these carbonyl groups to formyloxy (-OCHO), yielding by B-scission of –O–CH– groups in the main chain as thermo-oxidation proceeds in testing [20]. Intensity and width of this peak were slightly increased as shown in figure 2. This is caused by the formation of the carbonyl groups such as ketone (at 1766 cm-1), vinyl (at 1697 cm-1), etc. This proved that POM and POM/NS nanocomposites were decomposed by photo-oxidation degradation reactions into formic aldehydes, vinyl, ketone, etc. (as in figure 3) [21].

(a)

Figure 3. Decomposed reactions of POM [21].

Carbonyl index (CI) is parameter to quantify relatively the carbonyl group content existed in the exposed samples, it was calculated using the following equation: CI 

I1735 I 2800

Where, I1735 and I2800 are absorption peak intensity at 1735 cm-1 and 2800 cm-1.

(b) Figure 1. FTIR spectra of POM (a) and POM/NS nanocomposite using 1.5 wt.% NS (b) before and after testing.

The CI of POM and POM/NS nanocomposites before and after testing was performed in table 1. Table 1. Cacbonyl nanocomposites.

Interestingly, the absorption peak around 1735 cm-1 characterized for the stretching vibrations of carbonyl groups was seen clearly in FTIR spectra (figure 2). The band exhibiting a more obvious 287

of

POM

and

POM/NS

CI = (A1735/A2800) Before test

CI = (A1735/A2800) After test

POM

0.96

1.43

POM/0.5NS

1.36

1.27

POM/1NS

1.30

1.07

POM/1.5NS

1.17

1.06

POM/2NS

1.15

1.03

Sample

Figure 2. FTIR spectra of POM and POM/1.5 NS nanocomposite before and after testing in the band region corresponding to the carbonyl aldehyde group and the methylene bending.

index

The CI of POM and POM/NS nanocomposites using 0 to 2 wt. % NS were changed after testing. The CI of POM was increased from 0.96 to 1.43 responding to the increase of C=O group content, while the CI of POM/NS nanocomposites was reduced after testing. The extending of CI of POM demonstrated that the hydrocarbon chain of polymer was decomposed by photo-oxidation degradation. The CI of nanocomposites was

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decreased after testing due to the content of C=O group in POM macromolecules was descended. This can be explained by NS particles disperse and interact with POM macromolecules and NS particles play role as shielding, barriers and limit oxygen permeation into POM matrix. Thus, POM was inclined to break down dominant from aldehyde terminal groups of POM macromolecules leading to the reducing of C=O groups. As can be seen the CI of nanocomposites had tendency to reduce when the contents of NS was increased from 0.5 to 2 wt. %. This expressed the NS particles to reduce the photo-oxidation degradation of nanocomposites during testing. 3.2. Tensile properites Table 2 presented the tensile properties (tensile strength, elongation at break and Young’s modulus) of POM and POM/NS nanocomposites using different NS content before and after testing. It was clear that the tensile properties of the POM/NS nanocomposites before and after were higher than those of POM. The tensile strength and Young’s modulus of POM/NS nanocomposites had upward tendency with rising content of NS from 0.5 to 1.5 wt. % while the elongation at break was reached maximum value when content of NS was increased to 1 wt. %. After testing, the tensile properties of all samples were sharply decreased. This proved that the samples were decomposed caused by ultraviolet (UV) radiation and photo-oxidation degradation. According to Gardette et al. [22], the following degradation mechanism for photo-oxidation taken place in POM: the first step leads to the oxidation of the carbon atoms with the formation of secondary hydroperoxides that decomposes into two radicals: an alkoxy-macroradical and a hydroxy radical. The alkoxy-macroradical can react in two possible ways: a cage reaction may occur leading to the formation of carbonate and water, and a b-scission which leads to a formate and an alkoxy-macroradical. The tensile properties of POM/NS nanocomposites using different NS content after testing were larger than those of POM due to the NS particle was an inorganic additive reflecting UV radiation and oxygen permeation limitation into POM matrix. They were important reasons to improve the tensile properties of nanocomposites after testing.

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Table 2. Tensile properties of the POM/NS nanocomposites before and after testing. Content of NS (%)

Tensile strength (MPa)

Elongation at break (%)

Young’ modulus (MPa)

Before After Before After

Before

After

0

60.88

21.27

18.47

1.15

1736.44 1488.38

0.5

63.04

22.15

21.83

1.5

1798.56 1548.75

1

65.38

23.05

21.66

1.45

1899.93 1649.38

1.5

65.77

25.84

21.43

1.39

2001.33 1850.9

2

61.33

21.42

14.98

0.96

1653.06 1596.82

The change in tensile properties of the nanocomposites was described through retention of tensile properties. Table 3 demonstrated the retention of tensile properties of POM and nanocomposites after testing. The retention of Young’s modulus of POM/NS nanocomposites had maximum values, while the retention of elongation at break of that was minimum value. It could be seen, the retention of tensile properties of the nanocomposites was larger than that of POM. This proved that POM was affected by accelerated weather testing more than that of the nanocomposites. This is explained by the regular dispersion of NS particles into POM matrix and good adhesion with POM macromolecules. Therefore, the NS particles can be effective barriers which limit oxygen permeation into the nanocomposites as well as reduction of photooxidation degradation, thermooxidation degradation, scission reaction of POM macromolecules. As in table 3, the retention of tensile strength and Young’s modulus of the above nanocomposites reached a maximum value at 1.5 wt.% NS. When the NS content higher than 1.5 wt.%, the tensile properties of the nanocomposites after testing were decreased. May be, at the NS content higher than 1.5 wt.%, the NS particles are easy to agglomerate to form defects as micro-size pores in POM matrix that oxygen air can penetrate into the nanocomposites. Althought, the retention of elongation at break of POM/NS nanocomposites was larger than that of POM, the retention of elongation at break of nanocomposites was reduced when rising NS content. For example, the retention of elongation at breaks of nanocomposites were 6.87 %, 6.69 %, 6.40 %, and 6.47 % corresponding to 0.5, 1, 1.5 and 2 wt. %

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NS, respectively. These results in table 3 proved the weather stability of POM/NS nanocomposites was higher than that of neat POM. Table 3. Tensile properties of the POM/NS nanocomposites before and after testing. Content of NS (%)

Retention of tensile strength (%)

Retention of elongation at break ɛ (%)

Retention of Young’ modulus (%)

0

34.94

6.23

85.71

0.5

35.14

6.87

86.11

1

35.25

6.69

86.81

1.5

39.29

6.49

92.48

2

34.92

6.47

96.60

(a)

3.3. Dielectric properties The variation of dielectric constant and dielectric loss tangent of POM and POM/NS nanocomposites using different NS content after testing were expressed in Figure 4. It is clear that the dielectric constant and dielectric loss tangent of POM/NS nanocomposites at every frequency larger than that of neat POM after testing. The dielectric constant of POM/NS nanocomposites was increased with rising NS content. This can be explained by POM is less polarized than NS particles, so the polarization of nanocomposites is grew up when adding NS particles into POM matrix. Besides, when the NS is dispersed well into the polymer matrix, there is little space left between the NS particles. Thus, the dielectric constant of each NS particle is equal to the NS value (3.7-3.9 at 1000 Hz), which is higher than that of neat POM (3.28 at 1000 Hz), so the dielectric constant of nanocomposites is increased with rising NS content [23]. Figure 4b demonstrated the dielectric loss tangent (tan δ) of nanocomposites after testing was grew up with the rise up of NS content. This is explained by the presence of silanol groups on the surface of NS, which has the ability to absorb moisture so it is able to reduce the resistance of POM. As shown in figure 4, the dielectric constant and dielectric loss tangent of POM/NS nanocomposites were decreased with rising frequency. It means that at lower frequency, the material becomes more polarized, while the higher frequency, the polarity in the material can be reduced. 289

(b) Figure 4. Dielectric constant (a) and dielectric loss tangent (b) of POM and POM/NS nanocomposites after testing as function of NS content and frequency.

Table 4 presented the dielectric constant (ε), dielectric loss tangent (tan δ) and volume resistivity (v) of POM and POM/NS nanocomposites using different NS content before and after testing which were measured at 1 kHz. It can be seen that the dielectric constant and dielectric loss tangent (tan δ) of the nanocomposites after testing were increased with increasing NS content from 0 to 2 wt.%, corresponding to from 1.51 to 1.69 and from 0.0019 to 0.0166, respectively. The volume resistivity (v) of POM/NS nanocomposites after testing were reduced with rising NS content (0 to 2 wt.%) 5.9 x10+11 to 6.4 x10+10. The v of nanocomposites after testing was dropped due to the NS particles dispersed uniformly and distributed across the entire volume of the material. Therefore, the charged particles can easily move in the electric field through interphase regions with better conductivity [24-25]. From table 4, the dielectric constant (ε) and dielectric loss tangent (tan δ) of all samples after testing were smaller compared with the samples before testing. Contrary, the volume resistivity (v) of samples after testing was larger than that of

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samples before testing. This may be explained by the NS has silanol groups on the surface which has the ability to absorb moisture as aforementioned, leading to the formation of polar interactions and hydrogen bonds in the inter-phase regions of nanocompsites. Thus, the movement of molecule dipole is limited. Table 4. Dielectric constant (ε), dielectric loss tangent (tan δ) and volume resistivity (v) of POM and POM/NS nanocomposites using different NS content before and after testing. Samples

Dielectric constant (ε) Before After

Dielectric loss Volume resistivity (ρv) tangent (tgδ) (Ω.m) Before

After

Before

+11

1.51

0.0260 0.0019 9.55 x10+10 5.9x10

POM/0.5NS 3.26

1.56

0.0140 0.0067 7.69 x10+10 1.62x10

+11

POM/1NS

3.32

1.63

0.0101 0.0075 5.44 x10+10 1.56x10

+11

POM/1.5NS 3.34

1.67

0.0057 0.0114 3.88 x10+10 9.65x10

+10

POM/2NS

1.69

0.0070 0.0166 1.91 x10+10 6.4x10+10

3.56

phase (NS). The NS particles were dispersed most regularly into polymer matrix at 1.5 wt.% NS with at least the smallest crack, hole and defects (figure 5c). They were dispersed into POM with the size from 100 nm to 500 nm. The dispersion of NS particles in POM/NS nanocomposite using 2 wt.% NS (Figure 5d) was more difficult than that of the nanocomposites using less 2 wt.% NS. This can be explained by the hydrogen bond between NS particles was stronger than that between NS particles and polymer matrix at the high contents of NS [27].

After

3.20

POM

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3.4. SEM images The photodegradation of a polymer material usually begins from the surface and then develops along the depth gradually [26].

Figure 5. SEM images of POM (a), POM/NS nanocomposites using 1 wt. % (b), 1.5 wt. % (c) and 2 wt. % NS (d) before testing.

The surface of POM before testing was smooth without cracks, holes and free of any kind of defects (figure 5a). The figures 5b, c and d showed the surface of POM/NS nanocomposites with different NS contents had structure with two phases as matrix phase (POM) and dispersed 290

Figure 6. SEM images of POM (a), POM/NS nanocomposites using 1 wt. % (b), 1.5 wt. % (c) and 2 wt. % NS (d) after testing.

Figure 6 performed the SEM images of fracture surface of POM and POM/NS nanocomposites using 1, 1.5 and 2 wt. % NS after testing. It can be seen the morphology of nanocomposites was significant changed with the appearance of cracks on the surface of samples. The cracks were seen all over the surface, showing a preferential propagation of micro-cracks with further ramifications in other directions. The POM sample was highly degraded and the cracks formed with no preferential propagation tendency (figure 6a). The number of cracks and cracks size on the surface of samples were decreased and the cracks become smaller and less deeper with increasing NS content from 0.5 to 2 wt.% (figure 6b, c and d). As expressed in figures 6.c and 6.d, the surface damage of samples was somehow slighter. Only few cracks with small size were found on the surface of the samples. The surface of POM and nanocomposites using NS content less than 1.5 wt.% more appearance of cracks with size of cracks was bigger (figure 4.a and 4.b). This is explained by the formation of hydrogen bond between the C=O groups of POM and O-H groups

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of NS particles which limits photodegradation and photooxidation degradation of POM and nanocomposites. CONCLUSION Some remark related to the change of properties and morphology of POM and POM/NS nanocomposites after accelerated weather testing as follows: The FTIR spectra of nanocomposites indicated some characteristic peaks of POM and NS. Carbonyl index (CI) to quantify relatively the carbonyl group content existed of POM show the increase of C=O groups after accelerated weather testing in comparison with before test is corresponding to rose up from 0.96 to 1.43. CI of nanocomposites has tend to dropped with the increase of NS content from 0.5 to 2 wt.%. The tensile properties (tensiles strength, elongation at break and Young modulus) of all samples after testing were sharply decreased compared with before testing. The tensile properties results show that tensile strength and elongation at break of POM/NS reduced significantly while their Young modulus less decreased in comparison with before testing. The dielectric properties (dielectric constant, dielectric loss tangent and volume resistivity) of the nanocomposites after testing was reduced when compared with that before testing. The dielectric constant and dielectric loss tangent (tan δ) of the nanocomposites after testing were went up when NS content increased from 0 to 2 wt.%. The volume resistivity (v) of POM/NS nanocomposites after testing were reduced from 5.9 x10+11 to 6.4 x10+10 corresponding the rise NS content from to 2 wt.%. Scanning Electrion Microscopy (SEM) analysis on the surface of nanocomposites after testing shows the preferential propagation of micro-cracks with further ramifications in other direction. The number of cracks and size of cracks of the samples decreased when increasing NS contents of 2 wt.%. IV.

REFERENCES [1] Z. A. Mohamad, D. Yakubu, S. M. M. Y. Puteri, Effect of Environmental Degradation on Mechanical Properties of Kenaf/Polyethylene Terephthalate Fiber Reinforced Polyoxymethylene Hybrid Composite, Adv. Mater. Sci. and Engin., vol. 2013, DOI: 10.1155/2013/671481 [2] T. Lundin, S. M. Cramer, R. H. Falk, C. Felton, Accelerated weathering of natural fiber-filled polyethylene composites, J. of Mater. in Civil Engin., vol. 16, no. 6, pp. 547– 555, 2004

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[3] G. Wypych (1995), Handbook of material weathering (2nd edition): Chapter 9, Chapter 11, Chapter 13, ChemTec Publishing, Toronto, Canada, 155-163, 181201, 217-273 [4] K. Krasowska, J. Brzeska, M. Rutkowska, et al., Environmental degradation of ramie fibre reinforced biocomposites, Polish J. of Environmental Studies, vol. 19, no. 5, pp. 937–945, 2010 [5] V. M Archodoulaki, S. Lu¨ftl, S. Seidler, Degradation Behavior of Polyoxymethylene: Influence of Different Stabilizer Packages, J. App. Poly. Sci., Vol. 105, 3679– 3688 (2007) [6] L. Sigrid, P. M. Visakh, C. Sarath, Polyoxymethylene Handbook: structure, properties, applications and their nanonanocomposites, Wiley (2014) [7] W. Dziadur, The effect of some elastomers on the structure and mechanical properties of polyoxymethylene, Mater. Charac., Vol. 46, pp. 131– 135 (2001). [8] F. Wang, J.K. Wu, H.S. Xia, Q. Wang, Polyoxymethylene/carbon nanotubes nanocomposites prepared by solid state mechanochemical approach, Plastics, Rubber and Nanocomposites, Vol. 36, pp. 297–303 (2007). [9] K. Ghosh, S. Bashadi, H.J. Lehmler, S.E. Rankin, B.L. Knutson, Pore size engineering in fluorinated surfactant templated mesoporous silica powders through supercritical carbon dioxide processing, Micropor. Mesopor. Mater., Vol. 113, pp. 106-113 (2008). [10] L. Peng, W. Qisui, L. Xi, Z. Chaocan, Investigation of the states of water and OH groups on the surface of silica, Colloids and Surfaces A: Physicochem. Engin. Aspects, Vol. 334, pp. 112-115 (2009). [11] H. Zou, S. Wu, J. Shen, Polymer/Silica nanonanocomposites: preparation, characterization, properties, and applications, Chem. Rev., Vol. 108, pp. 3893-3957 (2008). [12] H. S. Katz, J. V. Milewski (1987), Handbook of Fillers for Plastics. Chapter 9. Synthertic silica, Van Nostrand Reinhold Company, New York, USA, 167-188. [13] F. Wang, J. K. Wu, H. S. Xia, Q. Wang, Polyoxymethylene/carbon nanotubes composites prepared by solid state mechanochemical approach, Plastics Rubber and Composites, Vol 36 (7/8) (2007), 297–303. [14] K. Pielichowska, Polyoxymethylenehomopolymer/hydroxyapatite nanocomposites for biomedical applications, J. App. Poly. Sci., Vol. 123 (2012) , pp. 2234–2243. [15] W. Sirirat, S. Paramaporn, S. Unchana, T. Supakanok, Mechanical and thermal properties of polyoxymethylene nanocomposites filled with different nanofillers, Poly. Plas. Technol. and Engin., Vol. 53 (2014): 181–188. [16] W. Sirirat, T. Supakanok, P. Akaraphol, E. Chaturong, Effect of particle sizes of zinc oxide on mechanical, thermal and morphological properties of polyoxymethylene/zinc oxide nanocomposites, Polymer Testing, 27 (2008), 971–976.

The 12th Asian Conference on Chemical Sensors (ACCS2017) [17] Z. Z. Afshin, S. N. Karim, The Effects of Interphase and Interface Characteristics on the Tensile Behaviour of POM/CaCO3 Nanocomposites, Nanomaterials and Nanotechnology (2014). [18] X. Zhao, L. Ye, Study on the thermal conductive polyoxymethylene/graphite composites, J. App. Poly. Sci., Vol 111 (2) (2009), pp. 759 – 767. [19] G. Wypych (1995), Handbook of material weathering (2nd edition): Chapter 9, Chapter 11, Chapter 13, ChemTec Publishing, Toronto, Canada, 155-163, 181201, 217-273. [20] V. R. Narciso, S. S. Miguel, I. Silvia, G. Antonio, Thermal Degradation of Polyoxymethylene Evaluated with FTIR and Spectrophotometry, Poly. Plas. Technol. and Engin., Vol. 48, 470–477 (2009) [21] L. Sigrid, P. M. Visakh, C. Sarath, Polyoxymethylene Handbook: Structure, Properties, Applications and their Nanocomposites(1 edition), chapter 15, WileyScrivener, 412-413 (2014) [22] J. L. Gardette, H. D. Sabel, J. Lemaire, Photooxidation of polyacetal copolymer I, Angew Makromol Chem, Vol. 188, 113-128 (1991)

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[23] B. El-Kareh, Fundamentals of Semiconductor Processing Technologies. Kluwer Academic Publishers, 1995. [24] P. M. Ajayan, L. S. Schadler, P. V. Braun, Nanocomposite science and technology, Chapter 2. Polymer-based and polymer-filled nanocomposites, Wiley-VCH Verlag, Weinheim, Germany, 77-144 (2003) [25] J. K. Nelson, R. K. MacCrone, L. S. Schadler, C. W. Reed, R. Keefe, Polymer nanocomposite dielectrics-the role of the interface, IEEE Dielectrics and Electrical Insulation Society, 12(4), 62 (2005) [26] L. D. Minh, N. T. Chinh, N. T. T. Trang, N. V. Giang, T. H. Trung, M. D. Huynh, T. T. Mai, L. D. Giang, T. Hoang, Study on change of some characters and morphology of polyethylene compound exposed naturally in Dong Hoi – Quang Binh, Vietnam Journal of Chemistry, vol. 54 (2), 153-159, 2016 [27] L. Z. Hua, L. Jian, F. Y. Fei, The effect of CF and nanoSiO2 modification on the flexural and tribological properties of POM nanocomposites, Journal of Thermoplastic Composite Materials, 1-10, DOI: 10.1177/0892705712443251 (2012).

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Characteristics of Counter Electrode Modified by Reduced Graphene Oxide for Dye-sensitized Solar Cell Chung-Ming Yang1, Jung-Chuan Chou1, 2,*, Yi-Hung Liao3, Chih-Hsien Lai1, 2, Chien-Hung Kuo2 Wan-Yu Hsu1 and Pei-Hong You2 1

Department of Electronic Engineering, National Yunlin University of Science and Technology, Yuniln, Taiwan. Addr: No. 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan, R.O.C 2 Graduate School of Electronic Engineering, National Yunlin University of Science and Technology, Yunlin, Taiwan Addr: No. 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan, R.O.C 3 Department of Information and Electronic Commerce Management, TransWorld University, Yunlin, Taiwan Addr: No.1221, Zhennan Road, Douliou, Yunlin 640, Taiwan R.O.C. *Corresponding author: [email protected]

Abstract: In this research, we used radio frequency (R. F.) sputtering method to deposit the aluminum

doped zinc oxide (AZO) film as a barrier layer on titanium dioxide (TiO2) double layers of photoelectrode for dye-sensitized solar cell (DSSC). Reduced graphene oxide (rGO), a two - dimensional material, has the advantages such as large specific surface area, high chemical tolerance and high structural flexibility. Because of its excellent electrochemical properties, which rGO is widely used as a material for photoelectric components. To reduce the volume of platinum (Pt) for counter electrode, we used rGO to modify the counter electrode. The rGO was deposited on Pt counter electrode, which deposition time was less than normal Pt counter electrode and enhanced the electrocatalytic ability of counter electrode. We not only measured the photovoltaic parameters, but also used electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) to verify the electrocatalytic activity. Keywords: aluminum doped zinc oxide, titanium dioxide, dye-sensitized solar cell, reduced graphene oxide

chemical/gas sensors, optical waveguides, and solar cells [5]. However, ZnO has lower electrical conductivity and lower thermal stability. To increase the electrical conductivity of ZnO, the aluminum (Al), the III element, is doped into ZnO and improves the electrical conductivity of ZnO by replacing zinc atom or occupying the interstice of lattices position in ZnO [5]. Due to a relatively low price, abundance, high thermal stability, high refractive index and non-toxicity, aluminum doped zinc oxide (AZO) is used widely as transparent conductive oxide film. AZO film also gradually replaces the tin-doped indium oxide (ITO) film [6].

INTRODUCTION In 1991, the group of M. Grätzel published the porous titanium dioxide (TiO2) layer to absorb dye, and this dye molecules of such ruthenium metal derivatives absorb near-fullwavelength sunlight [1]. Since then, the dyesensitized solar cell (DSSC) was researched widely because its advantages such as low cost, simple preparation method and non-toxic to the environment. Traditional DSSC is composed of five important components, which are transparent conductive oxide (TCO) glass, titanium dioxide photoelectrode, dye, electrolyte and platinum (Pt) counter electrode [2]. The electron of dye molecules is excited from ground state to excited state when the DSSC is illuminated by light. Then, the electron returns to the counter electrode by external circuit. The oxidized dye molecules obtain the electron from electrolyte and return to ground state. Triiodide (I3−) ion diffuses to surface of Pt counter electrode and is restituted by obtaining electrons from external circuit [3,4]. I.

Due to Pt is one kind of precious metals, many carbonaceous materials have been researched to replace or modify the Pt counter electrode such as carbon nanotubes, carbon black and graphene [7-9]. Among them, reduced graphene oxide (rGO), one kind of carbonaceous materials, has been applied in counter electrode, because its remarkable electrical, optical, and mechanical properties [10]. The electrocatalytic capacity of rGO for I － /I3 － redox reaction is significant, so rGO is a suitable material for counter electrode for DSSC.

Zinc oxide (ZnO) belongs to the N-type II-VI semiconductor material and the band gap of ZnO is 3.1 ～ 3.6 eV. And, ZnO has widespread applications in light-emitting diodes, 293

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EXPERIMENTAL

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A. Fabrication of AZO/TiO2 photoelectrode We prepared two kinds of TiO2 colloids in this experiment. One of the colloid was prepared for adsorption layer and the other was prepared for scattering layer. First, we coated the TiO2 colloid for adsorption layer onto the fluorine doped tin oxide (FTO) glass by spin-coating method, then we coated the second TiO2 colloid for scattering layer by doctor-blade method on the first TiO2 layer. Next, we used the radio frequency (R. F.) sputtering method to deposit the AZO barrier layer onto TiO2 double layer. The AZO/TiO2 photoelectrode was annealed at 450 ℃ for 30 min in air ambient. The thickness of AZO/TiO2 photoelectrode is 18.4 μm. Finally, the AZO/TiO2 photoelectrode was immersed in N3 dye for 24 h.

RESULTS AND DISCUSSION

A. Photovoltaic parameters for DSSC In this experiment, we tried to used AZO as a barrier layer onto the TiO2 double layer and used the rGO film to modify the Pt counter electrode. From the Table 1, we could find that the AZO/TiO2 photoelectrode based on DSSC showed the open circuit voltage (VOC), short circuit current density (JSC), fill factor (F. F.) and photovoltaic conversion efficiency (η), which was 0.74 V, 10.09 mA/cm2, 54.62 % and 4.10 %, respectively. The short circuit current density and photovoltaic conversion efficiency were greatly improved, which were attributed to that the AZO barrier layer provided outstanding blocking effect. AZO barrier layer achieved to prevent the recombination of electron and blocked the diffusion of electrolyte to TiO2 photoelectrode [11,12]. Another reason to increase photovoltaic conversion efficiency was attributed to the rGO provided the higher specific surface and increased the electrochemical activity of Pt counter electrode for I － /I3 － redox reaction [13]. Figure. 1 was shown the current density–voltage (J–V) curves for DSSCs with different counter electrodes. From Fig 1, we could find that the short circuit current density of rGO(3 mL)/Pt counter electrode was higher than other counter electrodes.

B. Fabrication of rGO/Pt counter electrode The Pt film also was deposited on FTO glass by R. F. sputtering method, which deposition time was 2 min. The rGO solution was mixed with 5mL deionized (D. I.) water, 5 mL NMethyl-2-Pyrrolidone (NMP) and 0.05 g rGO powders. After blending the rGO solution, the rGO film was coated onto Pt counter electrode by spin-coating method. Then, the rGO/Pt counter electrode was heated and dried in the oven at 75 ℃ for 15 min. The electrolyte solution was consisted of 0.6 M 1-propyl-2,3dimethylimidazolium iodide (DMPII), 0.5 M lithium iodide (LiI), 0.05 M iodine (I2), and 0.5 M 4-tert-butylpyridine (TBP) in 15 mL 3methoxypropionitrile (MPN). The AZO/TiO2 photoelectrode and rGO/Pt counter electrode were assembled into a typical sandwich-type cell. Then, added electrolyte into the middle between the photoelectrode and rGO/Pt counter electrode.

B. The Electrocatalytic capacity for rGO/Pt counter electrode Electrochemical impedance spectroscopy (EIS) is a common way to prove the electrochemical ability. Table 2 was shown the electrochemical impedance parameters for DSSCs with different counter electrodes, and the Fig. 2 showed the Nyquist plots for DSSCs with different counter electrodes. Where RS represented the serial resistance between FTO glass and wire, R1 represented the interface impedance between electrolyte and Pt counter electrode, R2 represented the impedance of electron recombination between electrolyte and TiO2 film [14,15]. We could know the R1 of different counter electrodes were 2.74 ohm, 4.76 ohm, 2.75 ohm, 6.22 ohm, respectively. When R1 was lower, the electrocatalytic capacity of counter electrode for I－/I3－ redox reaction was better, which was attributed to the higher specific surface and excellent electrocatalytic

C. Measurement We used solar simulator (MFS-PV-BasicHMT, Taiwan) to measure the photovoltaic parameters of DSSC under the sunlight intensity, which was 100 mW/cm2. We used electrochemical impedance spectroscopy (BioLogic SP-150, France) to obtain Nyquist plot and electrochemical impedance parameters. The scanning frequency was from 1 MHz to 10 mHz. The cyclic voltammetry (CV) were measure by electrochemical impedance spectroscopy. 294

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capacity of rGO. The rGO(3 mL)/Pt counter electrode demonstrated the lower R1, which was close to the R1 of Pt counter electrode. It represented the electrocatalytic capacity of rGO(3 mL)/Pt counter electrode was close to electrocatalytic capacity of Pt counter electrode. Cyclic voltammetry (CV) is another reliable measurement method to demonstrate electrochemical capacity. The CV curves for DSSCs with different counter electrodes were shown in Fig. 4. Two pairs of redox peaks could be seen and the redox peaks at negative potentials could be used to improve the electrocatalytic activity of counter electrode [2]. A higher peak current density and lower peakto-peak (EPP) potential separation will lead to an improved electrocatalytic capacity. According to Fig. 4, the EPP of rGO(3 mL)/Pt counter electrode was close to Pt counter electrode. Besides, the peak current density of rGO(3 mL)/Pt counter electrode was higher than other counter electrodes and it confirmed that the electrocatalytic activity of rGO(3 mL)/Pt counter electrode was better than other counter electrodes.

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[9]

CONCLUSION To summary, the AZO barrier layer achieved to prevent the recombination of electron. Besides, the rGO was applied the Pt counter electrode and improved the electrocatalytic capacity effectively. It was confirmed by EIS and CV measurement. The experimental data demonstrates that the AZO/TiO2 photoelectrode and rGO(3 mL)/Pt counter electrode achieved short circuit current density and photovoltaic conversion efficiency, which was 10.09 mA/cm2 and 4.10 %, respectively. IV.

[10]

[11]

[12]

ACKNOWLEDGMENT This study has been supported by Ministry of Science and Technology, Republic of China, under the contracts MOST 105-2221-E-224 049, 106-2813-C-224-015-E and 106-2221-E224 -047.

[13]

[14]

REFERENCES [1]

[2]

[3]

[4]

[5]

B. O’Regan, M. Grätzel, “A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films,” Nature, vol. 353, pp. 737-740, October 1991 J. Dong, J. Wu, J. Jia, L. Fan, J. Lin, “Nickel selenide/reduced graphene oxide nanocomposite as counter electrode for high efficient dye-sensitized solar cells,” Journal of Colloid and Interface Science, vol. 498, pp. 217-222, July 2017. H. Yuan, J. Liu, Q. Jiao, Y. Li, X. Liu, D. Shi, Q. Wu, Y. Zhao, H. Li, “Sandwich-like octahedral cobalt disulfide/reduced graphene oxide as an efficient Pt-free electrocatalyst for high-performance dye-sensitized solar cells,” Solar Energy Materials & Solar Cells, vol. 119, pp. 225-234, August 2017. J. Gong, J. Liang, K. Sumathy, “Review on dyesensitized solar cells (DSSCs): Fundamental concepts and novel materials,” Renewable and Sustainable Energy Reviews, vol. 16, pp. 5848-5860, October 2012. S. Pat, R. Mohammadigharehbagh, S. Ö zen, V. Şenay, H. H. Yudar, S. Korkmaz,“The Al doping effect on the

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surface, optical, electrical and nanomechanical properties of the ZnO and AZO thin films prepared by RF sputtering technique,” Vacuum, vol. 141, pp. 210215, July 2017. S. Boscarino, G. Torrisi, I. Crupi, A. Alberti, S. Mirabella, F. Ruffino, A. Terrasi,“Ion irradiation of AZO thin films for flexible electronics,” Nuclear Instruments and Methods in Physics Research B, vol. 392, pp. 14-20, February 2017. G. Wang, J. Zhang, S. Kuang, S. Zhuo, “Nitrogen-doped porous carbon prepared by a facile soft-templating process as low-cost counter electrode for Highperformance dye-sensitized solar cells,” Materials Science in Semiconductor Processing, vol. 38, pp. 234239, October 2015 J. Dong, J. Wu, J. Jia, L. Fan, J. Lin, “Nickel selenide/reduced graphene oxide nanocomposite as counter electrode for high efficient dye-sensitized solar cells,” Journal of Colloid and Interface Science, vol. 498, pp. 217-222, July 2017. T. N. Murakami, S. Ito, Q. Wang, Md. K. Nazeeruddin, T. Bessho, I. Cesar, P. Liska, R. Humphry-Baker, P. Comte, P. Péchy, M. Grätzelz, “Highly Efficient DyeSensitized Solar Cells Based on Carbon Black Counter Electrodes,” Journal of The Electrochemical Society, vol. 153, pp. 2255-2261, October 2006. Z. Wang, P. Li, Y. Chen, J. He, J. Liu, W. Zhang, Y. Li,“Phosphorus-doped reduced graphene oxide as an electrocatalyst counter electrode in dye-sensitized solar cells,” Journal of Power Sources, vol. 263, pp. 246-251, October 2014. J. H. Qi, Y. Li, T. T. Duong, H. J. Choi, S. G. Yoon, “Dye-sensitized solar cell based on AZO/Ag/AZO multilayer transparent conductive oxide film,” Journal of Alloys and Compounds, vol. 556, pp.121-126, April 2013 R. Sivakumar, J. Ramkumar, S. Shaji, M. Paulraj, “Efficient TiO2 blocking layer for TiO2 nanorod arraysbased dye-sensitized solar cells,” Thin Solid Films, vol. 615, pp. 171-176, September 2016. C. H. Tsai, W. C. Huang, W. S. Wang, C. J. Shih, W. F. Chi, Y. C. Hu, Y. H. Yu,“Reduced graphene oxide/macrocyclic iron complex hybrid materials as counter electrodes for dye-sensitized solar cells,” Journal of Colloid and Interface Science, vol. 495, pp. 111-121, February 2017. X. Chen, Q. Yang, Q. Meng, Z. Zhang, J. Zhang , L. Liu, X. Zhang, P. Yang,“Efficient dye-sensitized solar cells with CoSe/graphene composite counter electrodes,” Solar Energy, vol. 144, pp. 342-348, March 2017. J. Maa, W. Shen, C. Li, J. Zheng, F. Yu, “Graphene cryogel-based counter electrode materials freeze-dried using different solution media for dye-sensitized solar cells,” Chemical Engineering Journal, vol. 319, pp. 155162, July 2017.

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Analysis of Counter Electrode Modified by Reduced Graphene Oxide and Black Phosphorus with IGZO/TiO2 Photoelectrode for Dye-sensitized Solar Cell a

Chang-Yi Wua, Jung-Chuan Choua, b,*, Yi-Hung Liaoc, Chih-Hsien Laia,b, Chien Hung Kuob, Chang-Chia Lua and Pei-Hong Youb Department of Electronic Engineering, National Yunlin University of Science and Technology, Yuniln, Taiwan, Addr: No. 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan, R.O.C b

Graduate School of Electronic Engineering, National Yunlin University of Science and Technology, Yunlin, Taiwan, Addr: No. 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan, R.O.C c Department of Information and Electronic Commerce Management, TransWorld University, Yunlin, Taiwan, Addr: No.1221, Zhennan Road, Douliou, Yunlin 640, Taiwan R.O.C. *Corresponding author: [email protected]

Abstract: In this study, titanium dioxide (TiO2) colloid was deposited on the fluorine doped tin oxide

(FTO) substrate by spin coating and blade coating. Indium gallium zinc oxide (IGZO) was sputtered on the TiO2 film to form IGZO/TiO2 phototelectrode. Graphene is excellent carbon material, which is outstanding electrochemical catalysis, large specific surface area and high mobility. Black phosphorus is impressive two dimensional material, which has high electrical conductivity and direct energy gap. Pt counter electrode was modified by reduced graphene oxide and black phosphorus, which was fabricated with rGO/BP colloid by spin coating on the Pt film. IGZO/TiO2 photoelectrode exhibited high absorption and lower reverse recombination. We expected that rGO/BP counter electrode demonstrated good catalytic activity and charge transport. The photovoltaic conversion efficiency of the IGZO/TiO2 photoelectrode and rGO/BP counter electrode dye sensitized solar cell (DSSC) was increased, which was comparable to TiO2 photoelectrode and Pt counter electrode DSSC. Keywords: Indium gallium zinc oxide, titanium dioxide, dye-sensitized solar cell, reduced graphene oxide

recombination to decease photovoltaic conversion efficiency. In this study, we used indium gallium zinc oxide (IGZO) to improve reverse recombination phenomenon. IGZO thin film has long recombination time, uniformity over large area, low processing temperature, high transparency, uniform porous structure and high mobility (> 20 cm2/V．s) [57]. IGZO was deposited by the radio frequency (R.F.) sputtering method in vacuum environment, which has optimal uniform deposited surface and low pollution. Graphene is two-dimensional (2D) nanomaterial, and has sp2 hybrid orbital carbon atom, which stably forms thin film of honeycombed lattice. One property of grapheme is high electron mobility (> 125000 cm2/V·s) [810], which is comparable carbon nanotubes and monocrystalline silicon. The resistivity of grapheme is lower than copper and silver, it only has 10-6 Ω·cm, which makes graphene become

INTRODUCTION In 1991, M. Grätzel proposed porous titanium dioxide photoelectrode of dye-sensitized solar cell, which has low cost, simple fabrication and high photovoltaic conversion efficiency to alternative traditional silicon-based solar cells [1]. Dye-sensitized solar cell is consisted of transparent conductive oxide (TCO), TiO2 layer, dye, electrolyte and Pt counter electrode. The function of dye-sensitized solar cell was that ground state of dye molecule was turned into excitation state by photo excitation, excited electron was injected to TiO2 conduction band. After then, electron would transport to counter electrode by external circuit. The oxidized dye molecule would get electron to reduce ground state and, iodide (I-) would lost electron turning into triiodide (I3-).Then, triiodide (I3-) would get electron from counter electrode to reduce iodide (I-) [2-4]. However, reverse recombination current occurred between TiO2 layer and electrolyte, which resulted in non-ideal electron I.

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phosphene. After blending the rGO solution and the BP solution, the rGO/BP colloid was coated onto Pt counter electrode by spin-coating method. Then, the rGO/BP counter electrode

two-dimensional (2D) nano material with the minimal resistivity. Black phosphorus (BP) has received more attention in last three years, because black phosphorus was a kind of two-dimensional (2D) materials, which has the potential to replace graphene. Comparing with graphene, one of advantages is that black phosphorus has direct energy gap to fabricate semiconductor. black phosphorus has stable honeycomb structure, high mobility and direct energy gap. The honeycomb structure could help electrolyte and counter electrode (CE) to redox effectively, and high mobility influenced charge transport of external loop and electrolyte [11-13]. We used graphene and black phosphorus to modify the Pt counter electrode, which increases the photovoltaic conversion efficiency of DSSC. II.

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was heated and dried in the oven at 75 ℃ for 15 min. The electrolyte solution was consisted of 0.6 M 1-propyl-2,3-dimethylimidazolium iodide (DMPII), 0.5 M lithium iodide (LiI), 0.05 M iodine (I2), and 0.5 M 4-tert-butylpyridine (TBP) in 15 mL 3-methoxypropionitrile (MPN). The IGZO/TiO2 photoelectrode and rGO/BP counter electrode were assembled into a typical sandwich-type cell. Then, added electrolyte into the middle between the photoelectrode and rGO/Pt counter electrode. C. Measurement We used solar simulator (MFS-PV-BasicHMT, Taiwan) to measure the photovoltaic parameters of DSSC under the sunlight intensity, which was 100 mW/cm2. We used electrochemical impedance spectroscopy (BioLogic SP-150, France) to obtain Nyquist plot and electrochemical impedance parameters. The scanning frequency was from 1 MHz to 10 mHz. We used Multi- functional Field-Emission Scanning Electron Microscope (Hitachi S4800-I, USA) to obtain FE-SEM image.

EXPERIMENTAL

A. Fabrication of IGZO/TiO2 photoelectrode We prepared TiO2 colloids by spin coating and blade coating method in the experiment. TiO2 colloid was prepared by spin coating for adsorption layer, and the other TiO2 colloid was prepared by blade coating for scattering layer. First all, the spin-coating TiO2 colloid was coated on the fluorine doped tin oxide (FTO) glass to form adsorption layer, and the bladecoating TiO2 colloid was coated on the adsorption layer to form scattering layer. Next, we used the radio frequency (R. F.) sputtering method to deposit the IGZO/TiO2 barrier layer onto TiO2 double layer for 1 min. The IGZO/TiO2 photoelectrode was annealed at 450 ℃ for 30 min in air ambient. The thickness of IGZO/TiO2 photoelectrode is 16.7 μm. Finally, the IGZO/TiO2 photoelectrode was immersed in N3 dye for 24 h.

III.

RESULTS AND DISCUSSION

A. Photovoltaic parameters of DSSC In this study, we sputtered IGZO on the TiO2 photoelectrode to form barrier layer, and the rGO and black phosphorus was used to modify the Pt counter electrode, because we decreased content of Pt to reduce consumption. From Table 1, we could find that the rGO/Pt counter electrodes with IGZO/TiO2 photoelectrodes of DSSC exhibited the optimal open circuit voltage (VOC), short circuit current density (JSC), fill factor (F. F.) and photovoltaic conversion efficiency (η), which was 0.66 V, 9.39 mA/cm2, 62.25 % and 3.88%, respectively. From result, we seen that the short circuit current density and photovoltaic conversion efficiency were effectively improved, which were attributed to the IGZO/TiO2 barrier layer. IGZO/TiO2 barrier layer could considerably prevent the recombination of electron and blocked the diffusion of electrolyte to TiO2 photoelectrode [14-16]. Otherwise, Another reason to increase photovoltaic conversion efficiency was that rGO has higher specific surface and mobility, which

B. Fabrication of rGO/BP counter electrode The Pt counter electrode was deposited by R. F. sputtering method on FTO glass, and the deposition time was 2 min. The rGO solution was mixed with 5mL deionized (D. I.) water, 5 mL N-Methyl-2-Pyrrolidone (NMP) and 0.05 g rGO powders. The content of BP solution was 400ml N-Methyl-2-Pyrrolidone (NMP), NaOH and 200 mg black phosphorus (BP). After stirred about 2 hr, BP solution was centrifuged with 3000 rmp for 10 minutes. Then, we took floating liquid before centrifuged with 18000 rmp for 20 minutes. Final, we took sediment to get 1-7 layer 298

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increased the electrochemical activity of Pt counter electrode for I－ /I3－ redox reaction and charge transport of external loop and electrolyte [17-18]. Black phosphorus has honeycomb structure, high mobility and direct energy gap [11-13], but the photovoltaic parameters (η) of rGO/BP/Pt was 0.67 V (VOC), 8.41 mA/cm2 (JSC), 57.42 % (F. F.) and 3.27 % (η), respectively. The result was mainly due to add various materials (for example: rGO, Pt, NMP…etc.), where was confirmed by the Electrochemical impedance spectroscopy (EIS) measurement. From Table 1, we seen that short circuit current density of rGO/BP/Pt counter electrode with IGZO/TiO2 photoelectrode still higher than Pt counter electrode with IGZO/TiO2 photoelectrode, but the resistance was increased and recombination electron lifetime was decreased from EIS measurement. From the result, the fill factor of rGO/BP/Pt counter electrode with IGZO/TiO2 photoelectrode was considerably decreased. Figure 1 was shown the current density–voltage (J–V) curves for DSSCs with different counter electrodes and photoelectrodes. From Fig 1, we could find that the short circuit current density of rGO/Pt counter electrode was higher than other counter electrodes.

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would be improved, which was attributed to the outstanding mobility, higher specific surface and excellent electrocatalytic capacity of rGO. The rGO/Pt counter electrode demonstrated the lower R1, which has similar R1 comparing with Pt counter electrode. In the study, we use Eq. 1 to calculate recombination electron lifetime (τn). Rrec represent R2 and C represent C2 in the study. [22]. From Table 2 we known that the recombination electron lifetime (τn) of different counter electrodes and photoelectrodes were 23.24 ms, 305.58 ms, 426.02 ms and 357.04 ms, respectively. The property of high electron lifetime could decrease recombination of DSSC, because longer recombination time explained that needed to more time to recombine from TiO2 layer to ground state. From Table 1, the η of rGO/Pt was better than other samples. τn=RrecC

Eq. 1

C. Morphology Figure 4 (a)&(b) exhibited the SEM image of the film for TiO2 photoelectrode and IGZO/TiO2 photoelectrode on the ITO glasses and the corresponding cross section of the film of TiO2 photoelectrode and IGZO/TiO2 photoelectrode were demonstrated in the insets of Fig. 4 (c)&(d). Figure 4 (a) showed that many TiO2 molecules to form uneven surface, which average diameter was about 45 nm and random length was about 1~2 nm. Figure 4 (b) showed that molecules composed of IGZO and TiO2 to form uniform surface, which average diameter was about 80 nm and random length was about 20~30 nm. We could find that the original rugged TiO2 surface would be fixed by IGZO material, because IGZO has stable hexagons nanostructures and uniform over large area [1921]. The characteristic of IGZO influenced the morphology of TiO2 film, which helped its surface more compact to increase the chemical reaction with electrolyte. From the insert of Fig. 4 (c) and Fig. 4 (d), we seen that the corresponding cross section of TiO2 photoelectrode and IGZO/TiO2 photoelectrode were 19.5 um and 23.0 um, respectively.

B. Electrochemical impedance spectroscopy Electrochemical impedance spectroscopy (EIS) was an accurate measurement, which could through the impedance to understand the electrical properties of DSSCs with different counter electrodes and photoelectrodes. Table 2 was shown the electrochemical impedance parameters for DSSCs with different counter electrodes and photoelectrodes. Figure 2 demonstrated the Nyquist plots for DSSCs with different counter electrodes and photoelectrodes. Where R1 represented the interface impedance between electrolyte and Pt counter electrode, R2 and C2 represented the impedance and capacitance of electron recombination between electrolyte and TiO2 film, and τn showed the recombination electron lifetime of TiO2 film [22-24]. Table 2 showed that the R1 of different counter electrodes were 1.81 ohm, 1.86 ohm, 2.24 ohm, 8.61 ohm, respectively. When R1 was lower, the electrocatalytic capacity of counter electrode for I－/I3－ redox reaction was better and electrical conductivity of counter electrode 299

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Table 1 The Photovoltaic parameters for DSSCs with different counter electrodes and photoelectrodes. Counter electrode

photoelectrode

VOC (V)

JSC (mA/cm2)

F. F. (%)

η (%)

Pt

TiO2

0.63

6.74

62.09

2.64

Pt

IGZO/TiO2

0.65

8.33

63.32

3.38

rGO/Pt

IGZO/TiO2

0.66

9.39

62.25

3.88

rGO/BP/Pt

IGZO/TiO2

0.67

8.41

57.42

3.27

Table 2 The electrochemical impedance parameters for DSSCs with different counter electrodes and photoelectrodes. Counter electrode

photoelectrode

R1(Ω)

R2(Ω)

C2 (mF)

τn (ms)

Pt

TiO2

1.81

11.56

20.11

23.24

Pt

IGZO/TiO2

1.86

13.97

21.86

305.38

rGO/Pt

IGZO/TiO2

2.24

14.61

29.16

426.02

rGO/BP/Pt

IGZO/TiO2

8.61

66.04

5.41

357.04

(1) TiO2 photoelectrode with Pt counter electrode (1) TiO2 photoelectrode with Pt counter electrode

14

(2) IGZO/TiO2 photoelectrode with Pt counter electrode

(3) IGZO/TiO2 photoelectrode with rGO/Pt counter electrode

(3) IGZO/TiO2 photoelectrode with rGO/Pt counter electrode

(4) IGZO/TiO2 photoelectrode with rGO/BP/Pt counter electrode

(4) IGZO/TiO2 photoelectrode with rGO/BP/Pt counter electrode

10

(2)

(3) (2)

8 6

(3) (4)

(4)

Z''(Ohm)

2

Current Density (mA/cm )

12

(2) IGZO/TiO2 photoelectrode with Pt counter electrode

10

(1)

5

(1)

4 2 0 0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 0

Voltage (V)

20

40

Z'(Ohm)

Fig. 1 The JV curves for DSSCs with different counter electrodes and photoelectrodes.

Fig. 3 The partial magnification of Nyquist plots for DSSCs with different counter electrodes and photoelectrodes.

(1) TiO2 photoelectrode with Pt counter electrode (2) IGZO/TiO2 photoelectrode with Pt counter electrode

40

(3) IGZO/TiO2 photoelectrode with rGO/Pt counter electrode

35

(4) IGZO/TiO2 photoelectrode with rGO/BP/Pt counter electrode

30

Z''(Ohm)

25 20 15

(4)

10

(2) (3) (1)

5 0 0

20

40

60

80

100

Z'(Ohm)

Fig. 2 The Nyquist plots for DSSCs with different counter electrodes and photoelectrodes.

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Fig. 4 The SEM images of (a) TiO2 photoelectrode, (b) IGZO/TiO2 photoelectrode, (c) cross section of TiO2 photoelectrode, (d) IGZO/TiO2 photoelectrode. Photochemistry and Photobiology C: IV. CONCLUSION Photochemistry Reviews, vol. 4, pp. 145-153, 2003. [3] L. Bay, K. West, B. W. Jensen, T. Jacobsen, In conclusion, we confirmed that IGZO/TiO2 ―Electrochemical reaction rates in a dye-sensitized barrier layer could effectively block the solar cell—the iodide/tri-iodide redox system,‖ recombination of electron. Otherwise, the rGO Solar Energy Materials & Solar Cells, vol. 90, 2006, was modified the Pt counter electrode and pp. 341-351. improved electrochemical properties of DSSC. [4] G. Boschloo, A. Hagfeldt, ―Characteristics of the Iodide/Triiodide Redox Mediator in Dye-Sensitized The evidence was showed in EIS measurement. Solar Cells,‖ Accounts of Chemical Research, vol. The rGO/Pt counter electrode with IGZO/TiO2 42, pp. 1819-1826, 2009. photoelectrode exhibited optimal short circuit [5] C. Y. Chung, B. Zhu, R.G. Greene, M. O. current density and photovoltaic conversion Thompson, D. G. Ast, ―High mobility, dual layer, cefficiency, which was 9.39 mA/cm2 and 3.88 %, axis aligned crystalline/amorphous IGZO thin film respectively. transistor,＂ Applied Physics Letters, vol. 107, pp. 183503 1-5, 2015 ACKNOWLEDGMENT [6] M. Benwadih, R. Coppard, K. Bonrad, A. Klyszcz, D. Vuillaume, ―high mobility flexible amorphous This study has been supported by Ministry of igzo thin-film transistors with a low thermal budget Science and Technology, Republic of China, ultra-violet pulsed light process, ＂ ACS Appl. under the contracts MOST 105-2221-E-224-049, Mater. Interfaces, vol. 10, pp. 1-32, 2016 MOST 106-2813-C-224-015-E and MOST 106[7] H. Shin, K. Choi, H. Kim,―Low energy deposition 2221-E-224 -047. of InGaZnO channel layer using linear facing target sputtering for oxide TFTs,‖ Current Applied Physics, REFERENCES vol. 12, pp.39-43, 2012. [1] B. O’Regan, M. Grätzel, ―A low-cost, high[8] U. Mehmood, ―Efficient and economical dyeefficiency solar cell based on dye-sensitized sensitized solar cells based on graphene/TiO2 colloidal TiO2 films,‖ Nature, vol.353, pp. 737-740, nanocomposite as a photoanode and graphene as a 1991. Pt-free catalyst for counter electrode, ＂ Organic [2] M. Grätzel, ―Dye-sensitized solar cells,‖ Journal of

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Electronics, vol. 42, pp.187-193, 2017. Z. Yanting, L. Lin, C. Tingting, T. Guoxiu, W. Wenhua, ―Enhanced photocatalytic properties of ZnO/reduced graphene oxide sheets (rGO) composites with controllable morphology and composition,＂Applied Surface Science, vol. 412, pp. 58-68, 2017. C. A. Ubani,, M. A. Ibrahim, M. A. M. Teridi, K. Sopian, J. Ali, K. T. Chaudhary, ―Application of graphene in dye and quantum dots sensitized solar cell,＂ Solar Energy, vol. 137, pp. 531-550, 2016. B. Zheng, N. Sia, G. Xie, Q. Wang, ―Strain-induced modulation on phonon and electronic properties of suspended black phosphorus field effect transistor, ＂ Physics Letters A, vol.381, pp. 792-795, 2017. F. Xia, H. Wang, Y. Jia, ―Rediscovering black phosphorus as an anisotropic layered material for optoelectronics and electronics, ＂ Nature Communications, vol.10, pp. 1-6, 2014. A. Khandelwal, K. Mani, M. Harsha Karigerasi, I. Lahiri, ―Phosphorene – The two-dimensional black phosphorous: Properties, synthesis and applications, ＂Materials Science and Engineering B, vol.221, pp. 17-34, 2017. I. Hod, M. Shalom, Z. Tachan, S. Ruhle, A. Zaban, ―SrTiO3 Recombination-Inhibiting Barrier Layer for Type II Dye-Sensitized Solar Cells, ＂ J. Phys. Chem. C, vol. 114, pp. 10015-10018, 2010. S. J. Roh, R. S. Mane,S. K. Min, W. J. Lee, C. D. Lokhande, S. H. Han, ―Achievement of 4.51% conversion efficiency using ZnO recombination barrier layer in TiO2 based dye-sensitized solar cells, ＂ Applied Physics Letters, vol. 89, pp. 253512, 2006. K. J. Lee , J. S. Hwang, Y. S. Hana, ―Effects of a TiO2:CaO barrier layer on the back electron transfer in TiO2- based solar cells,＂ Journal of Industrial and Engineering Chemistry, vol. 50, pp. 96-101, 2017. X. Kaibing, Y. Jianmao, L. Shijie, L. Qian ,H. Junqing , ―Facile synthesis of hierarchical mesoporous NiCo2O4 nanoflowers with large specific surface area for high-performance supercapacitors,＂ Materials Letters, vol. 187, pp. 129-132, 2017. S. Xiao, T. A. Hatton, ―Redox-electrodes for selective electrochemical separations, ＂ Advances in Colloid and Interface Science, vol. 244, pp. 6-20, 2017. K. Nomura, H. Ohta, A. Takagi, T. Kamiya, M. Hirano, H. Hosono, ―Room-temperature fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors, ＂ Nature, vol. 432, pp.488-492, 2004. V. K. Jayaraman, A. M. Á lvarez, M. d. l. l. O. Amador, ―Effect of substrate temperature on structural, morphological, optical and electrical properties of IGZO thin films,＂ Physica E, vol. 86, pp. 164-167, 2017. J. Raja, K. Jang, H. H. Nguyen, T. T. Trinh, W. Choi, J. Yi, ―Enhancement of electrical stability of

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a-IGZO TFTs by improving the surface morphology and packing density of active channel, ＂ Current Applied Physics, vol. 13, pp. 246-251, 2017. [22] J. Bisquert, F. F. Santiago, I. M. Sero, G. G. Belmonte, S. Gimenez, ―electron lifetime in dyesensitized solar cells: theory and interpretation of measurements,‖ J. Phys. Chem., vol. 113, pp. 17278-17290, 2009. [23] Y. F. Pulido, C. Blanco, D. Anseán, V. M. García, F. Ferrero, M. Valledor, ―Determination of suitable parameters for battery analysis by Electrochemical Impedance Spectroscopy,＂ Measurement, vol. 106, pp. 1-11, 2017. [24] A. V. Murugan, M. V. Reddy, G. Campet, K. Vijayamohanan, ―Cyclic voltammetry, electrochemical impedance and ex situ X-ray diffraction studies of electrochemical insertion and deinsertion of lithium ion into nanostructured organic–inorganic poly(3,4-ethylenedioxythiophene) based hybrids, ＂ Journal of Electroanalytical Chemistry, vol. 603, pp. 287-296, 2007.

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Enzymatic Flexible Arrayed Urea Biosensor Based on GO/TiO2 Films Modified by Magnetic Beads 1

Cian-Yi Wu , Jung-Chuan Chou1,2,*, Yi-Hung Liao3, Chih-Hsien Lai1, 2, Siao-Jie Yan1, You-Xiang Wu1, and Hong-Yu Huang2 1

Graduate School of Electronic Engineering, National Yunlin University of Science and Technology, Addr: No. 123 University Road, Douliou, Yunlin 640, Taiwan, R.O.C. 2 Department of Electronic Engineering, National Yunlin University of Science and Technology, Addr: No. 123 University Road, Douliou, Yunlin 640, Taiwan, R.O.C. 3 Department of Information and Electronic Commerce Management, TransWorld University, Addr: No. 122, Zhennan Road, Douliou, Yunlin 640, Taiwan, R.O.C. E-mail: [email protected]

Abstract: We proposed an enzymatic flexible arrayed urea biosensor based on graphene oxide (GO)/ titanium dioxide (TiO2) films modified by magnetic beads (MBs). The urea biosensor was comprised of polyethylene terephthalate (PET), arrayed conductive wires and reference electrode, insulation layer and sensing films. The PET, used as substrate, has the advantages of portability, cost-effectiveness, flexibility and easy to preserve. Arrayed conductive wires and reference electrode were prepared by screen-printing with silver paste. Epoxy was used as insulation layer in encapsulated process, and which could define the sensing area by screen-printing. TiO2 was acted as sensing film, which is environmentally friendly and has better electron transition, and it was deposited by sputtering. The GO has a large specific surface area and rich functional groups, which is employed as an ideal matrix for enzyme immobilization and can improve enzyme absorption. The MBs were utilized to flexible arrayed urea biosensor based on GO/TiO2 film because MBs could enhance the enzyme-immobilization ability and have superior biocompatibility. The performances of flexible arrayed urea biosensor based on GO/TiO2 film, modified by MBs were measured via potentiometric measurement system. It could be found, that MBs could effectively enhance the catalytic reaction. Therefore, we provided a high sensitive platform for urea detection. Keywords: Enzyme biosensor, Magnetic beads, Urea detection

INTRODUCTION Urea is final product of mammals to waste nitrogen [1]. It is not as toxic as ammonia, but it still hurt human body while it is excess. For this reason, the detection of urea in a human body is indispensable role. In 1969s, G. G. Guilbault et al. fabricated the first urea biosensor with enzyme system [2]. After that, urea biosensor was gradually investigated extensively. An enzyme has specified and catalytic properties, and it also was acted as sensing element. The enzyme has been developed widespread in biosensors [3]. The coordination bonds can be formed by titanium, connecting with the amine, carboxyl groups of enzymes. Furthermore, titanium dioxide (TiO2) also can be utilized for upholding the biocatalytic activity of enzymes [4]. It often is proposed as a forward-looking interface for immobilized biomolecules, which is another important aspect of TiO2 material [5]. I.

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Until recently, we have seen mounting evidence of the usefulness of graphene oxide used in electrochemical sensors to improve the performance [6]. Graphene oxide (GO) processes high specific surface and it has abundant oxygencontaining functional groups [7, 8], which could enhance enzyme immobilization capability effectively. Nowadays, the use of magnetic beads (MBs) in biomedical region has increasingly been the object of study. The MBs are magnetic material, also named magnetic particles, and are component of Fe3O4, which has large surface-tovolume ratio, biocompatibility, less toxicity, stable magnetism as well as better absorption among biocatalyst and matrix [9]. Also, it is used for the immobilization of desired biomolecules for chemical bonding of target molecules, and which also used as biomolecule carriers [10]. Above the text, MBs can offer several advantages in enzyme-based biosensor, thus it is used to modify enzymatic flexible urea biosensor in this study. This study used polyethylene terephthalate (PET) flexible substrate to achieve wearable flexible

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sensor and personal healthcare monitor system in the past few years [11, 12]. Screen printed method and sputtering were used to prepare arrayed conductive wires, reference electrodes and sensing film, respectively. Urease as enzyme plays a bioreceptor, and which serves as catalyzer in biosensor system. Urease was immobilized by covalent bonding which was addition to available to catalyze a specific biochemical reaction, and stay stability under the normal working conditions of the biosensor [13]. Its arrayed structure with six sensing windows could confirm the accuracy of measurement even though there was one damage window. II.

EXPERIMENTAL

A.

Preparation of enzymatic flexible arrayed urea biosensor based on GO/TiO2 films First, the enzymatic flexible arrayed urea biosensor was prepared by screen printing technology and radio frequency (R. F.) sputtering. Silver paste, used as arrayed conductive wire and reference electrode, was printed onto polyethylene terephthalate (PET) flexible substrate, which is malleable to a certain extent, by screen printed method. Recently, flexible and bended substrate were widely used in personal healthcare wearable flexible sensor [11]. Sensing film was achieved by deposing TiO2 via R. F. sputtering. Epoxy was used as insulation layer, and it was printed by screen printing technology. The insulation layer could be used to avoid the device was damaged, and it could define reaction area of urea biosensor. Next, 0.3 wt% graphene oxide was titrated on the sensing windows, and it was placed for 8 hours at room temperature. The schematic diagram of enzymatic flexible arrayed urea biosensor was presented in Fig. 1. B.

Preparation of MBs - urease composite solution The magnetic beads solution in the ultrasonic oscillator evenly was shocked for 30 minutes. When the magnetic bead solution was uniform, the magnetic bead solution was sucked out using a micropipette, and then the magnetic beads and the suspension were separated by an external magnetic field.

304

Fig. 1. Schematic diagram of flexible arrayed urea biosensor [14].

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enzymatic

Therefore, used the micropipette to remove the suspension. The MBs were washed three times with PBS and the PBS was aspirated by a micropipette. 100 µl PBS, and 100 µl N-(3Dimethylaminopropyl)-N-ethylcarbodiimidehydrochloride (EDC) solution and magnetic beads were mixed by ultrasonic oscillator for 10 minutes. During the process of oscillating EDC, the surface of the magnetic bead was functionalized. MBsEDC mixture is completed. EDC was used as functionalization of the MBs surface, also named carboxylate activator. The 100 µl of urease solution was added into MBs, and the urease solution and magnetic beads mixed and vibrated for 8 hours. Finally, the urease-MBs composite solution was completed and it was stored at 4 ℃ when not in use. C.

Preparation of enzymatic flexible arrayed urea biosensor based on GO/TiO2 films modified by magnetic beads γ-APTS was titrated onto the GO/TiO2 sensing films while was placed at room temperature for 15 min and remnants were rinsed by D.I. water whereas whole step was repeated twice. γ -APTS was aimed to modify the sensing film surface and form functional group. Then, glutaraldehyde was titrated on sensing film surface and placed at room temperature for one day. Glutaraldehyde is used as crosslinking agent. However, the different volume ratios of the MBsurease composite solutions were 1:0.5, 1:1 and 1:2, and were titrated onto glutaraldehyde/GO/TiO2 sensing films while were placed and stored for 12 hours in freezer. The different volume ratios of the MBs-urease composite solutions were investigated to improve the performance of the ions absorption, and further resulted in the sensitivity and linearity. As the last step, glutaraldehyde was rinsed and removed by D. I. water.

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RESULTS AND DISCUSSION

B.

A.

Analysis of characterization of TiO2 and GO/TiO2 sensing films TiO2 sensing film was grown by R. F. sputtering, and GO film was deposited on TiO2 film. The cross section and morphologies of TiO2 and GO/TiO2 films could be observed from typical scanning electron microscope (SEM) images, as shown in Fig. 2. In Fig. 2 (a) presented SEM cross section images of thickness of TiO2 film could be observed, it was 300 ± 5 nm, and it presented excellent uniformity. The cross-section image of GO/TiO2 film was shown in Fig. 2 (b). GO film was deposited onto TiO2 film and it had wellmarked multi-layer structure. Multi-layer structure of GO offered several properties, such as pore structures, residual functional groups and specific surface areas [15]. Figure 2 (c) and (d) presented morphology images of TiO2 and GO/TiO2 film, respectively. According to the morphology images, it could be observed, the morphology has been changed that compared with TiO2 and GO/TiO2 films. And the results had exhibited rougher surface and the more cracks. It was due to the multi-layer structure of GO resulted from the stack of GO layers.

Atomic force microscopy analysis for the surface roughness of GO/TiO2 and MBs/GO/TiO2 films We adopt atomic force microscopy (AFM) to investigate the relation between the surface roughness and the sensing properties. To confirm that the GO / TiO2 characterization was modified by magnetic beads, AFM was used to analyze the surface roughness and surface area of GO / TiO2 and MBs/ GO / TiO2 films. Ra is revealed average roughness of the surface, the arithmetic average of the absolute surface height of the deviations [16]. The results of the surface roughnesses of GO/TiO2 and MBs/GO/TiO2 were indicated 43.2 nm and 201 nm, respectively. The surface roughness of GO/TiO2 film was modified by MBs which was obviously promoted. Further, the surface area of GO/TiO2 and MBs/GO/TiO2 were demonstrated 25.8 µm² and 34.6 µm², respectively. According to experiment result, the Ra and surface area of AFM analysis results indicated the surface roughness and surface area were increased by adding GO and MBs. In the previous reports has been presented that surface roughness and surface area allowed higher enzyme loading to matrix [17,18], and it could offer electrochemical properties and catalytic activity [19].

Fig. 2 SEM cross section images of (a) TiO2 and (b) GO/ TiO2 film, and morphology images of (c) TiO2 and (d) GO/ TiO2 film.

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(a)

(b)

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and linearity were calculated and plotted by Labview software. In order to investigate and obtain the optimal volume ratio of urease-MBs, different volume ratios of urease-MBs, such as 1:0, 1:0.5, 1:1 and 1:2, were used to modify the urea biosensor. From Table 1, it was demonstrated that the average sensitivity increased when the content of MBs increased. However, the average sensitivity increased till the volume ratio of urease-MBs was 1:1. In contrast to performance of the urea biosensor with volume ratio 1:1 of urease-MBs, the average sensitivity of urea biosensor with volume ratio 1:2 of urease-MBs was decreased. Figure 4 revealed the response results of the optimized urea biosensor, and which average sensitivity and linearity were 4.996 mV/(mg/dl) and 0.974, respectively.

Image Surface Area 25.8 µm² Image Projected Surface Area 25.0 µm² Image Ra 43.2 nm

Image Surface Area 34.6 µm² Image Projected Surface Area 25.0 µm² Image Ra 201 nm

Table 1 Comparisons of the sensing performances of GO/TiO2 film based urea biosensor modified by different MBs contents

Fig. 3 AFM of three-dimension image of (a) GO/TiO2 and (b) MBs/GO/TiO2 films

C.

Characteristic analysis of urea biosensor modified based on GO/TiO2 film by MBs Use of the voltage-time (V-T) measurement system proceeded characteristic analysis such as the average sensitivity and linearity. The basic sensing principle of most urea biosensors was to detect the product, which was catalyzed and hydrolyzed by the urease [20], as depicted in reaction equation (1). 𝑁𝐻& 𝐶𝑂𝑁𝐻& + 3𝐻& 𝑂

+,-./-

＋

2𝑁𝐻1 + 𝐻𝐶𝑂23 + 𝑂𝐻 3

Volume ratio of urease and MBs

Average sensitivity (mV/(mg/dl))

Linearity

1:0

2.976

0.975

1:0.5

2.957

0.921

1:1

4.996

0.974

1:2

2.213

0.893

(1)

Urea biosensor was immersed into urea test solution, and urease played a catalyze role, further formed the ammonium ions (NH4+), bicarbonate ions (HCO3-) and hydroxide ions (OH-). OHabsorb onto the sensing film surface further form the interface potential, which was detected by V-T measurement system. The potential signal was converted by data acquisition (DAQ) card from analog to digital. The curves of average sensitivity 306

Fig. 4 Sensing measurement of optimized urea biosensor.

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CONCLUSION In the summary, enzymatic flexible arrayed by MBs has been successfully realized. From SEM cross section and top-view images, the thickness of TiO2 film could be observed and it could be found GO was indeed prepared onto TiO2 film. The surface roughnesses of MBs / GO / TiO2 and GO / TiO2 films were analyzed by AFM. According to the experimental results, it could be found that MBs / GO / TiO2 film had excellent surface roughness compared with GO / TiO2 film. Then, the different contents of MBs were used to modify GO/TiO2 urea biosensor, it could be found that 1:1 of urease-MBs could achieve the optimal sensitivity. It also could be found that the sensing characteristics of the urea biosensor based on GO/TiO2 modified by MBs were superior to the urea biosensor based on GO/TiO2 film, and it was attributed to the excellent surface roughness of the MBs which could enhance enzyme loading and efficiently immobilized enzyme. IV.

ACKNOWLEDGMENT The current work was financially supported by Ministry of Science and Technology, Republic of China, under the contracts MOST 105-2221-E224-049 and MOST 106-2221-E-224-047. REFERENCES [1] [2]

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An Investigation on Applying Indium Gallium Zinc Oxide and Reduced Graphene Oxide to Photoelectrode for Dye-sensitized Solar Cells Chien-Hung Kuo1, Jung-Chuan Chou1, 2,*, Yi-Hung Liao3, Chih-Hsien Lai 1,2, Pei-Hong You1 1

Graduate School of Electronic Engineering, National Yunlin University of Science and Technology, 2

Addr: No. 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan, R.O.C Department of Electronic Engineering, National Yunlin University of Science and Technology, 3

Addr: No. 123 University Road, Section 3, Douliou, Yunlin 640, Taiwan, R.O.C Department of Information and Electronic Commerce Management, TransWorld University,

Addr: No.1221, Zhennan Road, Douliou, Yunlin 640, Taiwan R.O.C. * Corresponding author: [email protected]

Abstract: In this study, the titanium dioxide(TiO2) – reduced graphene oxide(RGO) – indium gallium zinc

oxide(IGZO) composited photoelectrode(TGIP) had been fabricated by hydro-thermal method, spin coating and sputtering. According to experimental results, the short circuit current density(J SC) was increased from 11.56 mA/cm2 to 15.07 mA/cm2, which contributed to the photovoltaic conversion efficiency increased from 4.24% to 5.91%. The increasing could be attributed to decrease in reverse current density. The reason of causing reverse current density was reverse recombination. The characteristics of TGIP had been investigated by Scanning Electron Microscopy(SEM), Electrochemical Impedance Spectroscopy(EIS), Energy Dispersive Spectrometer(EDS) and UVvisible Spectrometer (UV-vis Spectra). Keywords: Titanium dioxide, dye-sensitized solar cell, photovoltaic conversion efficiency, indium gallium zinc oxide, reduced graphene oxide

INTRODUCTION Due to shortage of energy, renewable energy source is a key point to sustainable development. There are some common renewable energy source, such as hydraulic power generation, wind power generation and solar power generation. The solar power generation or solar cell has been widely investigated, silicon solar cell especially. But silicon solar cell has some drawbacks, such as high cost, complex processes and time-consuming processes. Thus, the dye sensitized solar cell(DSSC) also has been investigated. Although the photovoltaic conversion efficiency of DSSC is still not high enough, the DSSC has three irreplaceable advantages, namely colorful external, potential for combining with glass of building and application of low illumination[1-5]. The nanostructure of phtotelectrode is very important for increasing photovoltaic conversion efficiency[6]. Many researchers modified the nanostructure of phtotelectrode by various methods, such as nanowires, microspheres and nanorods[7-9]. In general, we modify the nanostructure of photoelectrode for increasing short circuit current density(J SC), such as raising specific surface area to increase dye-loading and I.

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light harvesting, decrease in resistance of electron transmission. The hydro-thermal method was a method for composing material which proceeded chemical reaction in a conduction, which was high atmospheric pressure and high temperature[10]. The indium gallium zinc oxide(IGZO) is a kind of metal oxide semiconductor. Because of excellent characteristics of IGZO, such as wide band gap, high transparency and high mobility, it has been widely applied to thin film transistor(TFT)[11-12]. In this study, the reverse recombination and reverse current density had been investigated. The main reason of causing reverse recombination was two recombination paths. One was that photogenerated electron recombined with oxidized-dye, which can be improved by RGO. Due to the high mobility of RGO, which could accelerate the photo-generated electron from conduction band of TiO2 to conduction band of fluorine doped tin oxide(FTO) glass. The other path was photogenerated electron recombined with I 3- which was in electrolyte. This reverse recombination could be improved by IGZO, the IGZO could form an energy barrier to prevent electron from recombining with I3-. The titanium dioxide(TiO2) – reducedd graphene oxide(RGO) – indium

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gallium zinc oxide(IGZO) composited photoelectrode (TGIP) had been fabricated by spin coating and sputtering. According to experimental results, the short circuit current density(J SC) was increased from 10.2 mA/cm2 to 13.25 mA/cm2, which contributed the photovoltaic conversion efficiency increased from 4.31% to 5.89%. The increasing could be attributed to decrease in reverse current density. The characteristics of TGICP had been investigated by Scanning Electron Microscopy (SEM), Electrochemica Impedance Spectroscopy (EIS), Energy Dispersive Spectrometer(EDS) and UV-visible Spectrometer (UV-vis Spectra). Moreover, the energy band diagram of TGICP was also investigated. II.

EXPERIMENTAL

A. Materials The Ruthenium-535 (N3) was purchased from UniRegion Bio-Tech, Taiwan. The IGZO sputter target was purchased from Ultimate Materials Technology Co.,Ltd., Taiwan, which composited of 1mole% In2O3, 1mole% Ga2O3, and 2mole% ZnO, (purity 99.99%). The iodine puriss (I 2) was purchased from Riedel-de Haën, Germany. The ethanol was purchased from Katayama Chemical, Japan. The lithium iodide (LiI) and 4-TertButylpyridine (TBP) were purchased from SigmaAldrich, United States. The 1-propyl-2, 3dimethylimidazolium iodide (DMPII) was purchased from Tokyo Chemical, Japan. B. Preparation of the TiO2 – RGO composite 0.15 g of RGO was dispersed in 150 ml of deionized (D.I.)water, which became uniform by ultrasonic bath for 1 hour. Then 0.3 g of TiO 2 powder was added into RGO solution, which was vibrated by ultrasonic bath for 1 hour, and then the mixture was stirred for 1 hour. After stirring, 50 ml of the mixture was placed in autoclave. Meanwhile, the temperature was risen from room temperature to 180 °C for 2 hours. After cooling down to room temperature for 10 hours, TiO 2 – RGO composite was completed. The paste was composed of 1 g TGC, 2 ml D.I. water, 0.2 ml acetic acid, and it was stirred for 24 hours, which was named TG. For comparing, the pure TiO2 paste was fabricated, which composed of 1 g P25 TiO2 powder, 0.2 ml acetic acid, 2 ml D.I. water, which was named T. 309

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C. Prepaiation of the TiO2 – RGO - IGZO

composited photoelectrode The TG paste was coated on FTO glass by spin coating, then sputtered IGZO by sputtering. The parameters of sputtering were 40 Watt, 2 minutes and working pressure was 3 mtorr. After sputtering, the sputtered FTO glasses were sintered at 450 °C for 24 hours, then the sintered FTO glasses were soaked in N3 dye for 24 hours. The TiO 2 – RGO – IGZO composited photoelectrode(TGICP) was completed. For comparing, the pure TiO2 photoelectrode was fabricated by spin coating, which was named TP. D. Fabrication of the dye-sensitized solar cell The platinum(Pt) was sputtered on FTO glass by sputtering, which was counter electrode. The electrolyte solution was composed of 0.5 M lithium iodide (LiI), 0.05 M iodine (I 2), 0.6 M 1propyl -2,3-dimethylimidazolium iodide (DMPII), and 0.5 M 4-tert-butylpyridine (TBP) in 15 mL 3-methoxy -propionitrile (MPN). After that, the photoelectrode, electrolyte and Pt counter electrode were assembled into the sandwich structure. E. Measurement system The morphology was obtained by Scanning Electron Microscope(SEM). The absorption spectra of IGZO film, N3 dye and TiO 2 – RGO film were measured by UV-Vis Spectrophotometer(JASCO MODEL V-600, Taiwan). The mole percentages of IGZO between In2O3, Ga 2O3, ZnO were measured by Auger Electron Spectroscopy(AES). The weight percentages of TiO 2 – RGO composite between titanium, oxygen and carbon were measured by Energy Dispersive Spectrometer (EDS). The photovoltaic parameters and reverse current density of DSSC were measured by solar simulator (MFS-PV-Basic-HMT, Taiwan), and the sunlight intensity was 100mW/cm2. The Nyquist plot of interface impedance for DSSC was determined by Electrochemical Impedance Spectroscopy(EIS) (BioLogic SP-150, France) and frequency was set from 1 MHz to 50 mHz. III.

RESULTS

AND DISCUSSION

A. Analysis the components of the TiO2 - RGO composite The components of TiO2 - RGO composite

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were obtained from energy dispersive spectroscopy(EDS) Figure 1 and Table 1 showed the EDS image and atomic percentage of TiO2 – RGO composited film between carbon, oxygen and titanium, which were 3.81%, 74.92% and 21.27%, respectively. Ti ,O

Ti

C

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represented the resistance of wire. The C 1 represented the double-layer capacitance of interface between electrolyte and counter electrode and C2 was the double-layer capacitance of the interface between electrolyte and TiO 2 film. From Fig. 2(b), the first semicircle at high frequency represented resistance of interface between electrolyte and counter electrode(R1), and second semicircle at intermediate frequency was resistance of interface between electrolyte and TiO2 film(R 2)[13-17]. The R2 of DSSC based on TIGP was larger than that of based on TP, which increased from 95.73 ohm to 113.2 ohm, which meant the decrease in probability of reverse recombination. This result corresponded with measurement of reverse current density in Fig. R2 R1 2(c). (a)

C Fig. 1. The EDS image of the TiO2 – RGO composited film.

RS

Table 1 The atomic percent and weight percent of TiO2 – RGO(TG) composited film between titanium, carbon and oxygen. Weight Atomic percent(%) percent(%) Carbon 2.02 3.81 Oxygen 52.96 74.92 Titanium 45.02 21.27

C2

C1

(b)

B. Analysis the components of the IGZO film The components of IGZO film were obtained from X-ray photoelectron spectroscopy(XPS). From Table 2, the atomic% of IGZO between In, Ga, Zn and O were 7.51%, 28.65%, 21.94% and 41.9%.

(c)

Table 2 The atomic% of IGZO between In, Ga, Zn and O.

Atomic %

Indium (In)

Gallium (Ga)

Zinc (Zn)

Oxygen (O)

7.51

28.65

21.94

41.9

C. Electrochemical impedance spectroscopy and reverse current density Figure 2(a) is an equivalent circuit of the DSSC. Figure 2(b) showed the Nyquist plots of the DSSCs based on TGIP and TP. Table 3 showed the values of RS, R 1, R CT, C 1 and C2. The R S 310

Voltage(V)

Fig. 2. (a) The equivalent circuit of the DSSC ; (b)The Nyquist plots of the DSSCs based on TGIP and TP ; (c)The reverse current density of the DSSCs based on TGIP and TP.

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increased from 4.24% to 5.91%. From Fig.2(c), we could observe a decrease in the reverse current density after sputtering IGZO and adding graphene. The reason of causing reverse current density was reverse recombination. The main reason of causing reverse recombination was the two recombination paths. One was the photo-generated electron recombined with oxidized-dye, which could be improved by RGO[18]. Due to the high mobility of RGO, which could accelerate the photo-generated electron from conduction band of TiO 2 to conduction band of fluorine doped tin oxide(FTO) glass. The other path was the photo-generated electron recombined with I 3- which was in electrolyte. This reverse recombination could be improved by IGZO, the IGZO could form an energy barrier to prevent electron from recombining with I3-. Table 3 The values of components in the equivalent circuit for the DSSCs based on TIP and TP. RS (ohm)

C1 (μF)

R1 (ohm)

C2 (mF)

AD = εbc

(1)

Fig. 3. The absorptivity of the N3 dye, which was desorbed from TGIP and TP.

R2 (ohm) 17.5

TGIP

16.86

16.54

7.62

0.41

TGIP (1) TP (2)

113.2 15.0

TP

8.27

8.40

11.4

0.20

(1)

95.73

2

JSC(mA/cm )

12.5

D. Photovoltaic parameters Figure 3 showed The absorptivity of N3 dye, which was desorbed from TGIP and TP. And we calculated dye-loading by formula(1), where AD is the absorbance of the N3 dye, ε is the extinction coefficient of the N3 dye, b is the width of colorimetrical cylinder and c is the amount concentration of solution(dye-loading). In this case, AD was the absorbance of wavelength in 360 nm, ε was 14.1×103 L/mol and b was 1 cm, The dye-loading of TGIP was higher than that of TP, from 11.15×10-9 mol/cm3 to 16.17×10 -9 mol/cm3, which could be attributed the high specific surface area of RGO. The photo-generated electrons increased with increase in dye-loading, which contributed to increase in short circuit current density(JSC). Figure 4 showed the J-V curves of the DSSCs based on TGIP and TP. The JSC increased from 11.56 mA/cm2 to 15.07 mA/cm2, which could attributed to the decrease in reverse current density and increase in dye-loading, which contributed to photovoltaic conversion efficiency 311

(2)

10.0

7.5

5.0

2.5

0.0 0.00

0.15

0.30

0.45

0.60

0.75

V(V) Voltage(V)

Fig. 4. The J-V curves of the DSSCs based on TGIP and TP.

CONCLUSION In summary, titanium dioxide(TiO2) – reduced graphene oxide(RGO) – indium gallium zinc oxide(IGZO) composited photoelectrode(TGIP) had been investigated. The JSC increased 30.36%, from 11.56 mA/cm2 to 15.07 mA/cm2, which could be attributed to the decrease in reverse current density and increase in dye-loading, which contributed to photovoltaic conversion efficiency increased 39.39%, from 4.24% to 5.91%. IV.

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Table 4 The photovoltaic parameters of DSSCs based on TGIP an TP.

Photoelectrode

JSC (mA/cm2)

TGIP

15.07

TP

11.56

Specific surface area (m2/g)

Dye-loading (mol/L)

62.7

16.17×10 -9

53.2

11.15×10 -9

ACKNOWLEDGMENT This work was supported by the Ministry of Science and Technology, Republic of China, under contracts MOST 105-2221-E-224 -049 and MOST 106-2221-E-224-047.

[9]

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VOC (V)

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5.91

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57.45

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cells,”IEEE J. Photovolt., vol. 5, no. 4, pp.11061112, 2015. X. Luan, L. Chen, J. Zhang, G. Qc, J. Flake, Y. Wang,“Electrophoretic deposition of reducedd grapheme oxide nanosheets on TiO2 nanotube arrays for dye-sensitized solar cells,”Electrochim. Acta., vol. 111, pp.216-222, 2013. S. A. Kazmi, S. Hameed, A. S. Ahmed, M. Arshad, A. Azam, “Electrical and optical properties of graphene-TiO2 nanocomposite and its application in dye sensitized solar cells(DSSC),” J. Alloys Compd., vol. 691, pp. 659-665, 2017.

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Effect of other atoms on CO2 sensing properties of CaFe2O4 Kenji OBATAa, Keisuke MIZUTAa, Yuki OBUKUROb, Shigenori MATSUSHIMAa* a

Department of Creative Engineering, National Institute of Technology (NIT), Kitakyushu College, 5-20-1 Shii, Kokuraminami-ku, Kitakyushu 802-0985, Japan b Department of Materials System Engineering, National Institute of Technology (NIT), Kurume College, 1-1-1 Komorino, Kurume, Fukuoka 830-8555, Japan E-mail: [email protected] Abstract: In this study, we investigated the effect of other atoms on the CO2 sensing properties of CaFe2O4. We prepared CaFe2O4 powders using the malic acid complex (MAC) and polymerized complex (PC) methods. Then, we examined the CO2 sensing properties of a CaFe2O4-based sensor with other added atoms, inclusing Si, Ti, Hf, and Zr in the temperature range of 250 °C to 450 °C in dry air. At 300 °C and 350 °C, the CO2 sensitivity of the CaFe2O4 in MAC was improved by adding a small amount of impurity atoms such as Zr or Hf in comparison with that having no added atoms. The 90% response time of the M-added CaFe2O4-based sensor was much quicker at 350 °C than at 300 °C. The CO2 sensitivity of the 5 mol% Zr-added CaFe2O4 sensor reached maximum at 300 °C and 350 °C, which we estimated to be 2.9 times higher than that of pure CaFe2O4. Keywords: CaFe2O4, CO2 sensor, Zr addition, Hf addition, resistive-type sensor

INTRODUCTION There have been various studies of oxide semiconductor-based [1] and solid-state electrolyte-based [2] CO2 sensors. Among CO2 sensors, the oxide semiconductor-type sensor has attracted much attention since its electric resistance change is directly related to the CO2 concentration. However, there is a fundamental problem in that the CO2 response is low in this type of sensor. To improve the CO2 response, an oxide semiconductor with a high specific surface area must be synthesized and consideration given to its strong interaction with CO2 gas [3-6]. We found recently that the addition of zirconium (Zr) to the CaFe2O4 p-type semiconductor is much more effective for enhancing CO2 gas sensitivity [7]. The addition of Zr into CaFe2O4 forms a three-dimensional network structure, which results in a higher specific surface area compared sensors without Zr. Therefore, the Zr-added CaFe2O4based sensor has good CO2 sensing properties. In this research, we investigated in detail the CO2 sensing properties of M-added CaFe2O4-based sensors (M = Si, Ti, Hf, and Zr) prepared using organic acid complex (OAC) and polymerized complex (PC) methods. I.

II.

EXPERIMENTAL

2.1. Sample preparation We prepared CaFe2O4 powders from a malic acid complex (MAC) using the OAC [8] method and a PC [9]. As starting materials, we used Ca(NO3)2·4H2O, Fe(NO3)3·9H2O, and malic acid in a 1:2:3 molar ratio. We added the M atom by 314

introducing an alkoxide solution such as Si[OC2H5]4, Ti[OCH(CH3)2]4, Hf[OCH(CH3)2]4, or Zr[OC(CH3)3]4, into the above mixed solution. In this examination, we set the amount of additional atoms at 5 mol% with respect to Fe and calcined these at either 700 °C or 800 °C for 12 h in air. In all cases, the heating ratio was 10 °C min1 . We denote the Si-, Ti-, Hf-, and Zr-added CaFe2O4 by the MAC method as Si_MAC, Ti_MAC, HF_MAC, and Zr_MAC. We denote the Zr-added CaFe2O4 by the PC method as Zr_PC. We performed powder X-ray diffraction (XRD) measurements to analyze the crystal phase of the prepared sample powders. 2.2. Measurement of the sensor properties Figure 1 shows the schematic of the CO2 sensor using the alkaline earth ferrite-based material. We mixed the M-added CaFe2O4 powders with α-terpineol and applied the resulting paste on an alumina tube attached to a pair of Ptwire electrodes. We then fabricated the sensor element by heating the entire assembly at 600 °C for 2 h in air. We measured the CO2 sensing properties in a gas-flow apparatus equipped with heating facilities in the temperature range of 250 450 °C. We changed the CO2 concentration in the range of 0 – 5000 ppm by diluting CO2 gas with dry air and allowed the sample gases to flow over the sensor element at a rate of 0.1 dm3 min−1. We defined the gas sensitivity (S) as Rair/Rgas, where Rair and Rgas are the electric resistances of a sensor element in air and in a sample gas, respectively. We measured the electrical resistances on the basis of a conventional circuit in which the

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element is connected with an external resistor in a series.

Figure 1. Schematic of the CO2 sensor using the alkali earth ferrite-based material.

RESULTS AND DISCUSSION Figure 2 shows the XRD patterns for the 5 mol% M-added CaFe2O4 powders prepared from the malic acid complex. We prepared the Ti-, Zr-, and Hf-added CaFe2O4 powders (Ti_MAC, Zr_MAC, and Hf-MAC) after heating them at 700 °C in air for 12 h, and obtained the Si-added CaFe2O4 powder by calcining it at 800 °C in air for 12 h. There were no traces of an impurity phase in the Ti_MAC. However, we identified the diffraction peaks of the impurity phases as the CaFe4O7 and Ca2Fe2O5 phases in the Si_MAC, Zr_MAC and Hf_MAC. Then, we performed XRD measurement for the sample powders obtained by the PC method (Fig. 3). We could ascribe the XRD peaks of the unadded sample powder calcined at 700 °C in air to the CaFe2O4 phase. On the other hand, the XRD peaks of the 5 mol% Zr-added product could also be ascribed to the CaFe2O4 phase, with the appearance of small impurity peaks. We identified these diffraction peaks of the impurity phase as CaZrO3. III.

Figure 2. XRD patterns for M-added CaFe2O4 powders prepared from a malic acid complex.

315

Figure 3. XRD patterns for M-added CaFe2O4 powders prepared from a polymerized complex.

We fabricated M-added CaFe2O4 sensors and examined their CO2 sensing properties under dry conditions. Figure 4 shows the CO2 response curves of M-added CaFe2O4 (M = Si, Ti, Zr and Hf) to 5000 ppm CO2 in dry air at 350 ºC. When the atmosphere was changed from dry air to 5000 ppm CO2 in air, the electric resistances of the sensor decreased, suggesting that CO2 adsorbs on the surface of CaFe2O4 as a negatively charged species.

Figure 4. Transient response of M-added CaFe2O4 powder to 5000 ppm CO2 in air at 350 °C.

Figure 5 shows comparison of the CO2 sensitivities of M-added CaFe2O4 (M = Si, Ti, Zr and Hf) to 5000 ppm CO2 at various temperatures and we can see that the Zr_MAC-based sensor showed the highest CO2 sensitivity of the sensors, with high CO2 sensitivities in the operating temperature range of 300 °C to 350 °C. Fukuda and co-workers [10] analyzed the adsorption of CO2 on CaO by infrared analysis and reported that CO2 adsorbed on the CaO surface is easily desorbed above 370 ºC. In this analysis, it is possible that the desorption of CO2 on CaO caused a degradation of the CO2 sensitivity at elevated operating temperatures above 350 ºC. In contrast,

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the CO2 sensitivity of the Zr_PC-based sensor was lower than that of the Zr_MAC. We respect to the CO2 sensing of the CaFe2O4 sensor, we suppose it to be important that the Zr atom was introduced onto the surface of the CaFe2O4. Figure 6 depicts the 90% response time (t90) to 5000 ppm CO2 of the sensors made from M-added CaFe2O4 at the operating temperature. As shown in Fig. 6, the 90% response time of the M-added CaFe2O4-based sensor was much quicker at 350 °C than at 300 °C.

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comparison with that having no added atoms. The 90% response times of the M-added CaFe2O4based sensors were much quicker at 350 °C than at 300 °C. The CO2 sensitivity of the 5 mol% Zradded CaFe2O4 sensor reached maximum at 300 °C and 350 °C, and is estimated to be 2.9 times higher than that of pure CaFe2O4. ACKNOWLEDGMENT This work was partially supported by a Grantin-Aid for Scientific Research [Grant No. (C) 16K06782] and Mazda Motor Corporation [Grant No. 14KK-144]. REFERENCES

Figure 5. Dependence on operating temperature of the gas sensitivity of the M-added CaFe2O4 powders to 5000 ppm CO2.

Figure 6. Dependence on operating temperature of the 90% response time of M-added CaFe2O4 powder to 5000 ppm CO2 (t90: 90% response time).

CONCLUSION In this study, we investigated the effect of other atoms on the CO2 sensing properties of CaFe2O4. At 300 °C and 350 °C, the CO2 sensitivity of CaFe2O4 in MAC was improved by adding a small amount of impurity atoms such as Zr or Hf in IV.

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[1] J. Tamaki, M. Akiyama, C. Xu, N. Miura, N. Yamazoe, Conductivity change of SnO2 with CO2 adsorption, Chem. Lett., 19, 1243-1246 (1990). [2] M. Guthier, A. Chamberland, Solid-state detectors for the potentiometric determination of gaseous oxides, J. Electrochem. Soc., 124, 1579-1583 (1997). [3] C. Xu, J. Tamaki, N. Miura, N. Yamazoe, Grain size effects on gas sensitivity of porous SnO2-based elements, Sensor. Actuat. B-Chem., 3, 147-155 (1991). [4] T. Yoshioka, N. Mizuno, and M. Iwamoto, La2O3-loaded SnO2 element as a CO2 gas sensor, Chem. Lett., 20, 1249-1252 (1991). [5] M.Y. Kim, Y.N. Choi, J.M. Bae, T.S. Oh, Carbon dioxide sensitivity of La-doped thick film tin oxide gas sensor, Ceram. Int., 38, S657–S660 (2012). [6] M. S. Lee, J. U. Meyer, A new process for fabricating CO2-sensing layers based on BaTiO3 and additives, Sensor. Actuat. B-Chem., 68, 293–299 (2000). [7] K. Obata, K. Mizuta, Y. Obukuro, Go Sakai, H. Hagiwara, T. Ishihara, S. Matsushima, CO2 sensing properties of Zr-added porous CaFe2O4 powder, Sens. and Mater., 28, 1157-1164 (2016). [8] Y. Obukuro, K. Obata, R. Maeda, S. Matsushima, Y. Okuyama, N. Matsunaga, G. Sakai, Formation of CaFe2O4 porous structure by addition of Zr in malic acid complex, J. Ceram. Soc. Japan, 123, 995-998 (2015). [9] M. Popa, J. Frantti, M. Kakihana, Lanthanum ferrite LaFeO3+d nanopowders obtained by the polymerizable complex method, Solid State Ionics, 154–155, 437–445 (2002). [10] Y. Fukuda, K. Tanabe, Infrared Study of Carbon Dioxide Adsorbed on Magnesium and Calcium Oxides, Bull. Chem. Soc. Japan, 46, 1616-1619 (1973).

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Electrochemical Properties of Miniature Gas Sensors Using Semi-Solid Electrolyte Hana Cho, Min-Ho Kang, Dong-Yun Lee, Sang-Do Han*, Kie-Won Lee* Shinwoo Electronics Co. Ltd., 641, Pureundeulpan-ro, Paltan-myeon, Hwaseong-si, Gyeonggi-do, Republic of Korea * Corresponding author : [email protected]

Abstract: Toxic gas sensors are important that medical, safety, industry, product quality controls, military, monitoring system, automotive, home safety, and, more recently, country security. The electrochemical gas sensor has various advantages because it has various sensing gas depending on the electrode and electrolyte. Based on these advantages, attempts to make the sensor devices more intelligent and more quantitative are also important for further advancements of gas sensor technology. The most significant of developing electrochemical gas sensors is size miniaturization and lifetime including enhanced electrode and electrolyte. In this study, the miniature electrochemical sensors (size, 20×20×5mm) are optimized with electrode and part design. Also, the electrochemical properties of gas sensors are investigated with semi-solid electrolyte through the voltage-current graph using the cyclic voltammetry (CV) and measured the current change with the pico-ammeter. And then, the electrical conductivity was measured by the sheet resistance. The NO2 and SO2 gas are detected high sensitivity and selectively, which is expected to be applicable to various industries. Keywords: Gas sensor, Miniature, Semi-solid electrolyte, Redox reaction, Cyclic voltammetry

INTRODUCTION Electrochemical sensors have been extensively used in such applications as medical, safety, industry, product quality controls, military, automotive monitoring system, home safety and country security [1]. In these applications, electrochemical sensors have resulted in both economic and social benefits. So, since the gas sensor market is increasing year by year, the need for research is increasing. With electrochemical sensors, the target gas undergoes a chemical reaction, producing a current that is directly proportional to the concentration of gas present [2]. The sensors use very little power and show good responses to various gas concentrations over a wide range of ambient conditions. A miniature sensor (20×20×5 mm) using electrochemical property is available for several toxic gases including carbon monoxide, hydrogen sulfide and oxides of nitrogen and sulfur. I.

EXPERIMENTAL The miniature electrochemical sensors (square size, 20×20×5 mm) are optimized with electrode and part design. First, we made working electrode using Pt paste and the investigated detection range of toxic gases, respectively. Also, the electrochemical properties of gas sensors are examined with semi-solid electrolyte through the potential-

current graph using the cyclic voltammetry (CV) and measured the current change with the picoammeter. Cyclic voltammetry (CV) is a type of potentio-dynamic electrochemical measurement. In a cyclic voltammetry experiment, the working electrode potential is shown linearly versus time. III.

RESULTS AND DISCUSSION

A. Redox reaction The redox reaction is one of the most important sensor characteristics, and it can confirm redox reaction potential, sensor sensitivity and the like [3]. Fig. 1 shows the redox reaction of NO2 and SO2. The change of the current before and after the gas injection was shown through the potentialcurrent graph and showed high sensitivity. NO2 showed a sensitivity of 42 nA/ppm and SO2 showed a very high sensitivity of 4.5μA/ppm.

II.

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(a) NO2

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CONCLUSION In this study, we developed miniature electrochemical sensor and then measured its sensitivity by cyclic voltammetry. The miniature electrochemical sensors (size, 20×20×5 mm) are optimized with electrode and part design. IV.

(b) SO2 Figure 1. Redox reaction of (a) NO2 and (b) SO2 gas sensor.

B. Repeatability Fig. 2 is a graph of the repeatability of NO2 and SO2. The repeatability and the reactivity can be confirmed by the current value versus time in three complete voltage application curves.is a graph of the repeatability of NO2 and SO2. The reaction time of NO2 and SO2 sensor was within 30 seconds and the selectivity was within 5% of the total output.

We made working electrode using Pt paste and the investigated detection range of toxic gases, respectively. Also, the electrochemical properties of gas sensors are examined with semi-solid electrolyte through the potential-current graph using the cyclic voltammetry and measured the current change with the pico-ammeter. The change of the current before and after the gas injection was shown through the voltage/ current graph and showed high sensitivity. NO2 showed a sensitivity of 42 nA/ ppm and SO2 showed a very high sensitivity of 4.5 μA/ppm. The repeatability and the reactivity can be confirmed by the current value versus time in three complete voltage application curves.is a graph of the repeatability of NO2 and SO2. The reaction time of NO2 and SO2 sensor was within 30 seconds and the selectivity was within 5% of the total output. ACKNOWLEDGMENT This work was supported by the Technology Innovation Program funded by the Ministry of Trade, Industry and Energy (MOTIE, Korea) [Project Name: Development of Micro Electrochemical Gas Sensors and MeasuringTelecommunication Technology using Porous Electrode and high conductive Electrolyte (10076874)].

(a) NO2

REFERENCES [1] Ghenadii Korotcenkov, S. D. Han, and Joseph R. Stetter Review of Electrochemical Hydrogen Sensors, Chemical Reviews, 109 (2009) 1402-1433 [2] Di Wei, Ari Ivaska Applications of ionic liquids in electrochemical sensors, Analytica chimica acta, 607 (2008) 126-135. [3] D. Y. Lee, A. K. M. Kafi, S. H. Park, D. J. Qian, and Y. S. Kwon Influence of Anions on Electrochemical Redox Reactions and Electrical Properties using a Viologen Derivative, Japanese Journal of Applied Physics, 45 (2006) 3772-3775.

(b) SO2 Figure 2. Repeatability of (a) NO2 and (b) SO2 gas sensor

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Electrochemical behaviors of Fe2O3 inside carbon nanotubes in alkaline solution Bui Thi Hang1*, Doan Ha Thang2* 1

International Training Institute for Materials Science, Hanoi University of Science and Technology, Hanoi, Vietnam 2 Department of High Technology, Ministry of Science and Technology, Hanoi, Vietnam *Corresponding author: [email protected]; [email protected]

Abstract: To find the anode material for Fe-air battery, Fe2O3 inside carbon nanotubes (CNTs) was prepared by filling iron nitrate in carbon nanotubes and followed heating process in argon flow. The structure of this material was investigated by X-ray diffraction (XRD) measurement. Their morphology and particle size were observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). It was found that morphology, particle size and amount of iron oxide that filled in CNTs depend on the amount of iron nitrate precursor. When iron content was 5 wt% almost iron oxide particles resided inside CNTs and their particle size was smaller than that of iron content was 10 wt%. The preparation conditions may affect the morphology, particle size of Fe 2O3 inside CNTs material. The different in morphology, particle size of the materials will affect to their electrochemical properties that were investigated using cyclic voltammetry (CV). Keywords: Carbon nanotubes (CNTs), Fe2O3 inside CNTs, Fe-air battery

INTRODUCTION Rechargeable batteries with extremely large capacity are in strong demand as energy storage devices for use in electric vehicles (EVs) [1]. The metal-air battery is attracting much interest due to its large theoretical energy density because the cathode active material is not necessary for energy storage [2-6]. Metal-air batteries using several different metals have been investigated [7-10]. Among the various metal-air batteries, Fe-air batteries have received considerable attention due to their high theoretical capacity, long cycle life, high electrochemical stability, low cost, and environmental safety [11]. However, the problem of iron electrode is the a passive layer of Fe(OH)2 formed during the cycling leading to a low utilization coefficient. Further, the potential of the reduction reaction Fe/Fe(OH)2 is only slightly more negative than that of the hydrogen evolution in an alkaline solution [12, 13] thereby there is a simultaneous evolution of hydrogen evolution during charging [14, 15]. This is the cause of the low charge/discharge efficiency and high selfdischarge rate of iron electrode [16]. I.

In our previous work [17, 18], nano-sized Fe2O3-loaded carbon and Fe2O3-filled carbon nanotubes were prepared successfully and these materials provided high capacity for Fe-air battery anode. The problem of these materials is the fading capacity when repeated cycling. The main reason caused by increase in iron particle size and the dissipation of soluble HFeO2 species in electrolyte during cycling. Nano-sized Fe2O3 319

existed inside the carbon nanotubes are expected to limit the particle size of iron and inhibit the dissipation of soluble HFeO2 species upon cycling. However, the fading capacity still occurred [18]. In addition, the level of filling with these methods is often not satisfying. Thus, in this study, we present a simple method to prepare Fe2O3 inside carbon nanotubes material with high filling of Fe2O3. EXPERIMENTAL Carbon material used in this study is carbon nanotubes (CNTs) with average diameter of ca.50 nm. Iron nitrate (Wako Pure Chemical, Co.) was used as the iron source. CNTs were treated to remove catalyst before preparation of Fe2O3 inside CNTs. Carbon material was immersed in chloride acid 10% and mixture was agitated by a magnetic stirrer at room temperature for three days. CNTs were then removed, washed with ion-exchanged water and dried. CNTs were continually treated by gasification at 300oC before being used to prepare Fe2O3 inside CNTs. By gasification step, portions of CNTs walls were oxidized and the pores were formed. These pores may support for penetration of iron source into the CNTs. II.

The Fe2O3 inside CNTs material was prepared by dipping treated CNTs into the iron nitrate aqueous solution with weight ratios of iron to carbon of 5:95 wt% (Fe 5 wt%) or 10:90 wt% (Fe 10 wt%). The mixture was agitated by a magnetic stirrer within 5 days and dried at 50oC, followed by calcination for 1 h at 400oC in Ar flowing. The synthesized products were characterized by X-

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ray diffraction (RINT2100, Rigaku) with Cu Kα radiation (50 kV, 300 mA) from 2 = 1080o at a scan rate of 0.5o min−1. The morphology and microstructure of the resulting particles were observed by transmission electron microscopy (TEM), and scanning electron microscopy (SEM). To evaluate the electrochemical properties of the synthesized materials, electrode sheets were prepared by mixing 90 wt% of the synthesized materials and 10 wt% polytetrafluoroethylene (PTFE; Daikin Co.) and rolling. The electrodes were made into pellets with diameters of 1 cm. Cyclic voltammetry (CV) studies were carried out in a three-electrode glass cell assembly that had the synthesized material electrode as the working electrode, Pt mesh as the counter-electrode, and Hg/HgO as the reference electrode. The electrolyte was 8 mol dm-3 KOH aqueous solution. CV measurements were taken at a scan rate of 0.5 mV s−1 and within a range of –1.3 V to –0.1 V. In all electrochemical measurements, we used fresh electrodes without pre-cycling. RESULTS AND DISCUSSION Figure 1 shows the X-ray diffraction patterns of the as-synthesized materials with Fe:C=5:95 wt% (Fe 5wt%) and Fe:C=10:90 wt% (Fe 10wt%). At different weight ratios of iron and carbon, an Fe2O3 phase (ICDD No. 33-0664) is indeed present together with carbon in the product. No identifiable XRD signals related to other phases were observed. This result suggested that the synthesized material contains Fe2O3 and carbon and the successful synthesis of Fe2O3 particles inside CNTs was confirmed.

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To confirm the morphology of the Fe2O3 particles present inside the CNTs, TEM measurements were carried out on assynthesized materials and the results were showed in Fig. 2. (a)

(b)

III.

Figure 1. XRD patterns of the as-synthesized Fe2O3 inside CNTs with (a) Fe 5wt% and (b) Fe10wt%.

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Figure 2. TEM images of as-synthesized Fe2O3 inside CNTs with (a) Fe 5wt% and (b) Fe 10wt%

The dark particles are Fe2O3 while the fibers are CNTs. The TEM images demonstrated that the carbon nanotubes were filled with fine Fe2O3 particles. It can be seen that synthesis conditions including the iron-to-carbon ratio, carbon, heating environment had an effect on the morphologies and particle size of Fe2O3. Various morphologies of Fe2O3 could be observed, such as particles and nanorods. The size of Fe2O3 is much different between particles and nanorods. For particle, Fe2O3 is very small whereas it is much larger for nanorods. Generally, iron oxide particles are smaller than 20 nm. For Fe 5wt%, almost all of Fe2O3 nanoparticles were inside CNTs and a few Fe2O3 nanoparticles were distributed outside of CNTs. Some parts of CNTs were not filled by Fe2O3 nanoparticles. In the case of Fe 10 wt%, in addition to Fe2O3 nanoparticles inside CNTs, some free Fe2O3 particles were found on the

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surface of CNTs. Similar to Fe 5 wt%, some parts of CNTs in Fe 10 wt% material were not filled by Fe2O3 nanoparticles. The pores on CNTs in both cases will support for the penetration of electrolyte into the CNTs. Such a distribution of Fe2O3 is expected to support the redox reaction of Fe2O3 and inhibit an increase in the particle size of Fe2O3 caused by re-distribution of iron pieces during cycling via a dissolution-deposition process. Obviously, the cyclability and capacity of Fe2O3 inside CNTs will be improved.

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the reduction peak c1 occurred at around - 1.05 V, which is a lower potential than in the subsequent cycle, due to the reduction of iron oxide to form iron metal. The peak appeared at around −1.2 V was ascribed to the hydrogen evolution (c3).

Figure 4. Cyclic voltammetry of Fe2O3 inside CNTs composite electrodes with Fe 10 wt% at various scan rates.

Figure 3. Cyclic voltammetry of Fe2O3 inside CNTs composite electrodes with Fe 5 wt% at various scan rates.

To investigate the influence of scan rate, CV measurements were carried out with various scan rates and the results are shown in Fig. 3 and 4. In the both cases Fe 5 wt% (Fig. 3) and Fe10 wt% (Fig. 4), several peaks were observed, including a small oxidation peak at around -0.85 V (a1) and a corresponding reduction peak at around -1.05 V (c2) together with a sharp couple peak at around 0.65 V (a2) upon oxidation and around - 0.95 V (c1) upon reduction. The anodic peak (a1) and cathodic peak (c2) corresponds to the Fe/Fe(II) redox couple whereas peak (a2) and peak (c1) to the Fe(II)/Fe(III) redox couple. In the first cycle, 321

The CV results in Figs. 3 and 4 showed that the trend of changing in CV profiles obtained in both the cases of Fe 5 wt% and Fe 10 wt% was similar such as overpotential was increased with an increase in scan rate as evidenced by a shifting of oxidation peaks toward more positive and reduction peaks toward more negative. Consequently, the iron deposition peaks c2 were overlapped by hydrogen evolution peaks c3 in the both cases. When repeated cycling, the overpotential and redox current were decreased, however the decrease in Fe 5 wt% electrodes was smaller than that in Fe 10 wt% electrodes. The reduction peaks c2 of the Fe 5 wt% and Fe 10wt% electrodes still were covered by hydrogen evolution c3 with repeated cycling. Thus, scan rate affected the redox reactions of Fe2O3 inside CNTs electrodes and lower scan rate is better for Fe2O3 inside CNTs. Comparison CV results of Fe 5 wt%

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and Fe 10 wt% electrodes at the same sweep rates suggested that Fe 5wt% provided the sharp redox peaks while those peaks were broad for Fe 10 wt%. These behaviors will support for Fe 5 wt% during cycling. However, at sweep rate of 0.1 mVs-1, Fe 10 wt% electrode gave sharp redox peaks, high redox current, the reduction peak c2 separated from hydrogen evolution peak c3, therefore at these conditions Fe 10 wt% seem to be better than Fe 5 wt%. CONCLUSION Fe2O3 inside CNTs materials were successfully synthesized by a facile chemical route. The obtained material contains Fe2O3 and carbon without any a side product. The size of Fe2O3 was smaller than 20nm. The pores on CNTs support for penetration of iron salt into CNTs and thus almost all of Fe2O3 nanoparticles were inside CNTs and a few Fe2O3 nanoparticles were distributed on the surface of CNTs. The pores on CNTs also support for the penetration of electrolyte into the CNTs. With such a distribution of Fe2O3, the redox reaction of Fe2O3 and the cyclability of Fe2O3 inside CNTs were improved. Fe2O3 inside CNTs material is a promising candidate to apply for battery anode. IV.

ACKNOWLEDGMENT This research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 103.02-2014.20. REFERENCES [1] H. Chen, T. N. Cong, W. Yang, C. Tan, Y. Li, and Y. Ding, Progress in electrical energy storage system: A critical review, Prog. Nat. Sci., 19 (2009) 291–312. [2] K. M. Abraham* and Z. Jiang, A Polymer Electrolyte‐ Based Rechargeable Lithium/Oxygen Battery, J. Electrochem. Soc., 143 (1996) 1-5. [3] U. Sahapatsombut, H. Cheng, and K. Scott, Modelling of electrolyte degradation and cycling behaviour in a lithium-air battery, J. Power Sources, 243 (2013) 409– 418. [4] S. A. Freunberger, Y. Chen, Z. Peng, J. M. Griffin, L. J. Hardwick, F. Bardé, P. Novák, and P. G. Bruce, Reactions in the rechargeable lithium-O2 battery with alkyl carbonate electrolytes, J. Am. Chem. Soc., 133 (2011) 8040–8047. [5] D. Capsoni, M. Bini, S. Ferrari, E. Quartarone, and P. Mustarelli, Recent advances in the development of Liair batteries, J. Power Sources, 220 (2012) 253–263.

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[6] B. Dunn, H. Kamath, and J.-M. Tarascon, Electrical Energy Storage for the Grid: A Battery of Choices, Science, 334 (2011) 928–935. [7] N. Koçyiğit, Ü. E. Özen, M. Özer, B. Salih, A. R. Özkaya, and Ö. Bekaroğlu, Electrocatalytic Activity of Novel Ball-Type Metallophthalocyanines with Trifluoro Methyl Linkages in Oxygen Reduction Reaction and Application as Zn-Air Battery Cathode Catalyst, Electrochim. Acta, 233 (2017) 237–248. [8] X. X. Zeng, J. M. Wang, Q. L. Wang, D. S. Kong, H. B. Shao, J. Q. Zhang, and C. N. Cao, The effects of surface treatment and stannate as an electrolyte additive on the corrosion and electrochemical performances of pure aluminum in an alkaline methanol-water solution, Mater. Chem. Phys., 121 (2010) 459–464. [9] D. D. Macdonald, K. H. Lee, a. Moccari, and D. Harrington, Evaluation of Alloy Anodes for Aluminum-Air Batteries: Corrosion Studies, Corrosion, 44 (1988) 652–657. [10] U. Casellato, N. Comisso, G. Mengoli, X. X. Zeng, J. M. Wang, Q. L. Wang, D. S. Kong, H. B. Shao, J. Q. Zhang, C. N. Cao, T. Wang, M. Kaempgen, P. Nopphawan, G. Wee, S. Mhaisalkar, M. Srinivasan, K. F. Blurton, and A. F. Sammells, Metal/air review batteries: their status and potential, J. Power Sources, 195 (2010) 4350–4355. [11] R. D. McKerracher, C. Ponce de Leon, R. G. A. Wills, A. A. Shah, and F. C. Walsh, A Review of the Iron-Air Secondary Battery for Energy Storage, Chempluschem, 80 (2015) 323–335. [12] C. Chakkaravarthy, P. Periasamy, S. Jegannathan, and K. I. Vasu, The nickel/iron battery, J. Power Sources, 35 (1991) 21–35. [13] A. K. Shukla, M. K. Ravikumar, and T. S. Balasubramanian, Nickel/iron batteries, J. Power Sources, 51 (1994) 29–36. [14] C. A. Caldas, M. C. Lopes, and I. A. Carlos, The role of FeS and (NH4)2CO3 additives on the pressed type Fe electrode, J. Power Sources, 74 (1998) 108–112. [15] C. A. C. Souza, I. A. Carlos, M. Lopes, G. A. Finazzi, and M. R. H. De Almeida, Self-discharge of Fe-Ni alkaline batteries, J. Power Sources, 132 (2004) 288– 290. [16] N. Jayalakshmi and V. S. Muralidharan, Electrochemical behaviour of iron oxide preparation of iron oxide electrodes, 32 (1990) 277–286. [17] B. T. Hang, T. Watanabe, M. Eashira, S. Okada, J. I. Yamaki, S. Hata, S. H. Yoon, and I. Mochida, The electrochemical properties of Fe2O3-loaded carbon electrodes for iron-air battery anodes, J. Power Sources, 150 (2005) 261–271. [18] B. T. Hang, H. Hayashi, S. H. Yoon, S. Okada, and J. ichi Yamaki, Fe2O3-filled carbon nanotubes as a negative electrode for an Fe-air battery, J. Power Sources, 178 (2008) 393–401.

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Controlling of the diameter and density of silicon nanowires prepared by silver metal-assisted chemical etching Le Thanh Cong1,2, Nguyen Thi Ngoc Lam1, Nguyen Truong Giang1, Nguyen Duc Dung2, Ngo Ngoc Ha1,* 1

International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology (HUST), No. 1 Dai Co Viet Str., Hai Ba Trung dist., Hanoi, Vietnam 2 Advanced Institute for Science and Technology (AIST), HUST, No. 1 Dai Co Viet Str., Hai Ba Trung dist., Hanoi, Vietnam *Corresponding author: [email protected]

Abstract: Silicon nanowires (SiNWs) prepared by silver (Ag) metal-assisted chemical etching (MACE) method are investigated by mean of the electron microscopy. Ag particles, used as the catalytic metal, are formed on Si (100) wafers at room temperature after the reduction reaction in the solution of HF and AgNO3. The growth of SiNWs was carried out by the immersion of the Si substrate covered with Ag particles in a solution of HF and H2O2. Changing of AgNO3 concentration, so as to control the size of the Ag particles on the Si wafers can determine the size and density of the SiNWs. For lower AgNO3 concentrations, smaller Ag particles formed, thus larger SiNWs were made. Size and density of SiNWs decreased with the increase of AgNO3 concentration. We also found that the growth rate of SiNWs is found to depend nonlinearly on the time of etching. Keywords: Silicon nanowires, MACE, Photoluminescence

INTRODUCTION Silicon nanowires (SiNWs) have attracted attention and research in recent years as a potential candidate for development of advanced functional electronic devices. Innovative applications of these materials may include the field of manufacturing nanoscaled electronic and optoelectronic components, the manufacture of solar cells, biological and chemical sensors[1–7]. Developed from the most popular and abundant semiconductor on earth – silicon (Si), SiNWs inherit the advantages of the mature, wellequipped and modern micro-electronic fabrication technology - complementary metal-oxidesemiconductor. I.

Various physical and chemical methods have been used to fabricate SiNWs such as vapor liquid solid, ultra- supercritical fluid-liquid-solid method, laser ablation, metal-assisted chemical etching (MACE) and many other methods from top-down to bottom-up technologies [3,8–12]. Among these methods, MACE has certain advantages such as simple engineering technology, low fabricating cost, suitable for both manufacturing on the large scale for industrial application as well as laboratory scale. Basically, the MACE method consists of two consecutive processes, which are the process of forming metal catalysts on the surface of the Si wafers and the subsequent erosion/etching process for formation of the 323

SiNWs[13–16]. In such the fabrication processes, many factors may influence to size, direction, density and length of the SiNWs.

Figure 1. Schematical procedures of Si nanowires formation from Si wafer by MACE method. This consists of two consecutive processes, which are the process of forming Ag particles on the surface of the Si wafers and the erosion for the formation of the SiNWs

In this study, fabrication processes for the formation of SiNWs by the MACE method with the use of Ag particles as the catalytic metal are presented. This includes the two mentioned consecutive steps. First is the making Ag particles based on the precipitation process on the Si surface by reduction reaction of Ag+ ions to Ag nuclei in HF and AgNO3 solutions on the surface of the Si wafer. Ag particles deposited on the Si wafers are used to assist in erosion of the Si wafer in a mixture of HF and H2O2 solution for the formation of SiNWs. Size, density and length of the SiNWs are controlled by varying the

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concentration of the erosion/etching time.

solution

mixture

and

EXPERIMENTAL The monocrystalline Czochralski (CZ) Si wafer (100) dimension of 4-inch diameter, n-type, doped with P with 1 ÷ 10 Ohmcm-1 conductivity are cut into small pieces of about 1 cm × 1 cm. First, these small pieces of Si wafers (in short we call “Si wafers”) are washed in acetone and deionized water to remove surface dusts. II.

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10 minutes to remove organic and inorganic contaminations. The Si wafers are further immersed in a 1:10 HNO3/H2O solution for 10 minutes to remove any possible metal contamination on the Si surface. Finally, washed with a 1:20 solution of HF and H2O for 10 minutes to remove the natural surface SiO2 layer and be washed with deionized water. After being cleaned, Ag particles are deposited on the Si surface by immersion in HF and AgNO3 solution mixture for 1 minute. The mixture attains with HF concentration of 4,6 M and various concentrations of AgNO3 solutions of 15, 20, 25, 30, and 30 mM. Next, the sample was eroded in a solution mixture of HF and H2O2 for the formation of SiNWs. All the fabrication processes were carried out at room temperature. Subsequently, SiNWs samples were immersed in 1:10 HNO3/H2O solution to remove excessive residual Ag metal. Finally, the SiO2 layer on the surface of SiNWs was removed with a 1:20 HF/H2O solution and washed with deionized water and dried in air. Morphologies of the samples were investigated with the scanning electron microscopy on a JEOL JMS 7600F (Japan). RESULTS AND DISCUSSION Roles of the concentration of AgNO3 in the solution mixture of HF and AgNO3 as a controlling factor of size and the density of the SiNWs are investigated. Figure 2(a-e) present SEM images of Ag particles on the surfaces of Si wafers after the reactions of HF and AgNO3 solutions. Various AgNO3 concentrations of 15, 20, 25, 30, 35 mM were chosen, corresponding to Fig.2(a), (b), (c), (d), and (e), respectively. As it can be seen, when the concentration of AgNO3 increased from 15 mM to 25 mM, the size of Ag particles increased, leading to the decrease of the diameter of SiNWs after etching time of 90 min. The diameter of nanowires reduced from 1 µm to 100 nm shown in Fig. 2(f-h). When the AgNO3 concentration increases to 25 mM, the formation of smaller SiNWs becomes clearer, however, these SiNWs seem to be stuck together as shown in Fig. 2(h). When the concentrations AgNO3 increases to 30 mM and 35 mM, we see that the average size of Ag particles do not to change significantly, however, the number of Ag particles become bigger, thus they stack to form porous layers of Ag particles (Fig. 2(d,e)). This may explain the reason why size of the obtained SiNWs does not depend III.

Figure 2. Electron Microscopy (SEM) images of the morphologies of the Ag particles on the surfaces of Si wafers after the reduction reaction of HF and AgNO3 solutions (left panels) and the corresponding SiNWs (right panels). Various AgNO3 concentrations of 15, 20, 25, 30, 35 mM were chosen, corresponding to Fig.2(a, f), (b, g), (c, h), (d, i), and (e, k), respectively.

Subsequently, the Si wafers were soaked in the solution of H2SO4 and H2O2 with a ratio of 1: 3 for 324

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strongly on the catalytic Ag particles in this experiment. However, the higher number of Ag particles on the surface of Si wafer helps to separate the SiNWs with the average size of about 100 ÷ 200 nm, thus enables the observation of single SiNWs. The mechanism for the formation of Ag particles on Si wafers after the reaction of HF and AgNO3 solutions was described by Peng et al.[8]. When the Si wafer is embedded in the HF and AgNO3 solution mixture, the Ag+ ions in the vicinity of the Si surface receive electrons from the valence region of Si and are reduced to Ag nuclei. These Ag nuclei, on return, serve to catalyze the subsequent reduction of Ag ions, leading to the formation of catalytic Ag particles on the surface of Si wafer.

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The dependence of the length of SiNWs on the etching/erosion time was investigated. Figure 3 shows the morphologies (left panels) and crosssections (right panels) of the SiNWs after the erosion/etching of Si wafers in the solution of HF 4,8 M and H2O2 0,4 M for the etching time of 50, 70, 90, and 110 min, corresponding to Fig.3 (a,e), (b,f), (c,g), and (d,h), respectively. Ag particles on the surface of Si wafer obtained after the reduction process in the solution of HF 4,6 M and AgNO3 30 mM for 1 min at room temperature. It is shown that the etching time does not cause significant decrease of the average size of SiNWs with the observed cross-section of about 100 nm to 200 nm for all the etching. Obviously, the role of the catalytic metal is conclusive and erosion of SiNWs, also Si wafer, without the catalyst is negligible in the experiment.

Figure 4. The nonlinear dependence of SiNWs length on etching time over the investigated time scale of about 2 h.

Figure 3. (SEM) images of the morphologies (left panels) and cross-section (right panels) of the SiNWs after the erosion process of Si wafers in HF 4,8 M/H2O2 0,4 M in 50 (a,e), 70 (b,f), 90 (c,g), and 110 (d,h) min. Ag particles deposited on the Si wafer obtained in the reduction process in HF 4,6 M/AgNO3 30mM for 1 min.

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It was also shown that the length of SiNWs increases nonlinearly with the increased etching time. Figure 4 presents the dependence of the length of SiNWs on etching time obtained from the cross-section profiles in the SEM measurements. We can see that SiNWs increase from about 4 µm to 15 µm within the etching time from 50 min to 110 min. As the SiNWs are long enough, at the etching time of around 90 mins, corresponding to the SiNW length of about 12 µm, the tips of the SiNWs are observed to congregate. We suggest that the aggregation of the tips hindered further etching reaction thus reduce the etching rate over time. As a result, it influences to the dependence curve of the length of SiNWs on etching time as shown in Fig 4.

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CONCLUSION In this paper, controlling factors for the growth of SiNWs including Ag particles and etching time were described and discussed. SiNWs with the lengths as a function of erosion/etching time and diameters of 100 nm to 200 nm were successfully fabricated by MACE at room temperature with the Ag particles used as catalytic metal. Mechanism of formation of Ag particles has been explained and discussed. These results help to improve SiNWs fabrication process for application orientation, especially in new-structure Si-based solar cells[9] and lithium-ion battery anodes[4].

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IV.

ACKNOWLEDGMENT This work is financially supported by the Vietnam Ministry of Education and Training, Project number B2016-BKA-31.

[7]

[8]

[9]

[10]

[11]

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G.G. Pethuraja, H. Efstathiadis, C. Rouse, M. V Rane-Fondacaro, A.K. Sood, P. Haldar, Ieee, Silicon Nanowire Development for Solar Cell Devices, 2012 38th Ieee Photovolt. Spec. Conf. (2012) 1911–1916. doi:10.1109/PVSC.2012.6317967. A. Cao, E.J.R. Sudhölter, L.C.P.M. de Smet, Silicon nanowire-based devices for gas-phase sensing, Sensors (Switzerland). 14 (2013) 245–271. doi:10.3390/s140100245. F. Priolo, T. Gregorkiewicz, M. Galli, T.F. Krauss, Silicon nanostructures for photonics and photovoltaics, Nat. Nanotechnol. 9 (2014) 19–32. doi:10.1038/nnano.2013.271. R. Huang, X. Fan, W. Shen, J. Zhu, Carbon-coated silicon nanowire array films for high-performance lithium-ion battery anodes, Appl. Phys. Lett. 95 (2009) 67–70. doi:10.1063/1.3238572. M.D. Kelzenberg, S.W. Boettcher, J.A. Petykiewicz, D.B. Turner-Evans, M.C. Putnam, E.L. Warren, J.M. Spurgeon, R.M. Briggs, N.S. Lewis, H.A. Atwater, Enhanced absorption and carrier collection in Si wire arrays for photovoltaic applications, Nat. Mater. (2010) 1–13. doi:10.1038/nmat2635. N. Shehada, J.C. Cancilla, J.S. Torrecilla, E.S. Pariente, G. Brönstrup, S. Christiansen, D.W. Johnson, M. Leja, M.P.A. Davies, O. Liran, N. Peled, H. Haick, Silicon Nanowire Sensors Enable Diagnosis of Patients via Exhaled Breath, ACS Nano. 10 (2016) 7047–7057. doi:10.1021/acsnano.6b03127.

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Electrochemical behaviours of ZnO nanowires grown on-chip for biosensing applications Nguyen Thi Hong Phuoc1, Nguyen Van Toan1, Matteo Tonezzer2, Vo Thanh Duoc1, Dang Thi Thanh Le1,* 1

ITIMS, Hanoi University of Science and Technology (HUST), No.1, Dai Co Viet Str., Hanoi, Vietnam 2 IMEM-CNR, sede di Trento - FBK, Via alla Cascata 56/C, Povo - Trento, Italy *Corresponding author: [email protected]

Abstract: Due to the high surface area and good bio-compatibility of nanostructured ZnO, it finds good utility in biosensor applications. In this study, zinc oxide nanowires (ZnO NWs) were fabricated for electrochemical characterization. ZnO nanowires with average diameter ~ 30-200 nm in hexagonal crystalline structure were grown on working electrode using hydrothermal method at low temperature. Their morphology and structure were analyzed by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). Electrochemical properties of the electrodes with ZnO nanowires were investigated in comparison with Pt electrodes. The results showed that the cyclic voltammogram and electrochemical impedence spectrum (EIS) of ZnO nanowires were stable, but have much bigger resistance comparing to that of Pt electrodes owing to the semiconducting nature of ZnO NWs.

Keywords: biosensing, nanowires, electrochemical Pt electrodes, ZnO.

INTRODUCTION Nowadays, the increasing demand of highly sensitive devices has potential applications in biomedical, biotechnological, industrial and environmental fields, especially disease diagnosis [1]. Among those sensing devices, we have seen extensive research in the area of biosensors based on various matrixes [2–5]. A large of nanocrystalline metal oxides such as CeO2 [6], Fe3O4 [7], MnO2 [8], ZnO [9–11], CuO [12],.. has been applied in electrochemical sensors. Among them, ZnO has a number of attractive properties for making biosensors such as good biocompatibility, chemical stability, nontoxicity, high electrochemical activity and fast electronic transfer rate. ZnO is a n-type semiconductor with high isoelectric point (IEP=9.5) enables them to easily bind electrostatically with the low isoelectric point protein molecules (IEP∼1–5) [13]. ZnO has a wide range of applications in optoelectronics, sensors, transducers, energy conversion and medical sciences. Thus, there has been a rapid growth in the literature concerning the application of ZnO for the detection of various biomolecules such as glucose, DNA, antibodies and bacteria with improved stability and selectivity. Onedimensional (1D), ZnO nanowires are of particular interest for sensing applications due to their wide band gap (3.37 eV) and high exciton binding energy (60 meV) which broadens the scope of I.

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detection from purely resistive [14]. The diameter of these nanowires being comparable to biological molecules to be sensed and high surface-to-volume ratio increases the sensitivity of detection manifolds [15]. This results in higher sensitivity of the biodevices and makes them a very promising material for immobilization of biomolecules without electron mediator for use in electrochemical immunosensors. Among the various synthesizing processes of 1D nanostructures, hydrothermal technique has more advances than the other methods. The method have several advantages such as use of simple equipment, catalyst-free growth, low cost, large area uniform production, environmental friendliness, and less hazardous [11]. In this work, we demonstrate nanowires-modified Pt/SiO2/Si substrate. A simple, low cost, hydrothermal method was used to synthesize zinc oxide nanowires. The wires properties such as morphology and size can be controlled by adjusting the reaction temperature, time and concentration of precursors. The comparison on electrochemical properties between ZnO nanowires matrix based electrochemical electrode and platinum electrodes were discussed. II.

EXPERIMENTAL

A. Material preparation ZnO nanowires were hydrothermally grown on

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working electrode of the devices after sputtering a ZnO seed layer. Hydrothermal synthesis solution for the growth of ZnO nanowires was prepared by dissolving 20 mM zinc nitrate hexahydrate (Zn(NO3)2.6H2O, 98%, Aldrich) and 20 mM hexamethylenetetramine(C6H12N4,≥99%, Aldrich) in deionized water. The devices were dipped in solution at 60oC for 2 h, then at 85o C for 22 h. After the synthesis was completed, ZnO nanowires were rinsed with deionized water many times then dried. Hitachi S-4800 field-emission scanning electron microscopy (FESEM) was used to collect images of ZnO NWs at many magnifications. Bruker D5005 diffractometer recorded XRD data for the structure analysis. B. Experimental characterizations of the electrodes Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements were carried out on an instrument Palmsens 3 (Palmsens BV-Netherlands) consisting of a microprocessor and a low noise and low-current potentiostat/galvanostat in the phosphate buffer solution (PBS) (50 mM, pH 7.4, 0.9% NaCl) containing 5 mM [Fe(CN)6]3/4. The CV measurements were performed scanning from 0.5 to +0.5 V at a scan rate of 50 mV/s to evaluate the modification of Pt electrode with ZnO NWs. For the comparison study, bare (unmodified) Pt electrodes were also used. The EIS spectra were recorded at an equilibrium potential without external biasing in the frequency range of 0.001 ÷ 5× 104 Hz in a open-circuit potential value of +0.0 V with a 10 mV amplitude. RESULTS AND DISCUSSION C. Material characterization The morphology of the hydrothermally grown ZnO nanowires on electrochemical electrodes were investigated by scanning electron microscopy (SEM), as shown in Figure 1. They have a uniform morphology with the diameter in the range of ~ 30-200 nm. The diameter and morphology of the wires could be controlled either by temperature or by time of hydrothermal process. The XRD pattern of the samples was obtained to characterize the structure and phase purity of the ZnO products, as is shown in Figure 2.

Fig.1. FESEM images of ZnO nanowires at different magnifications.

III.

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Fig.2. XRD analysis of ZnO nanowires. The common peaks at 31.86◦, 34.49◦, 36.34◦, 47.63◦, 56.65◦, 62.96◦ and 68.04◦ are indexed to confirm ZnO wurtzite structure crystal planes (100), (002), (101), (102), (110), (103), and (112), in agreement with JCPDS card no. 361451 (lattice parameters: a,b=3.249 Ǻ and c=5.206 Ǻ) [16,17]. No peak from impurities has been found.

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D. Electrochemical properties The electrochemical behaviours of ZnO nanowireswere evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Figure 3 shows the cyclic voltammograms of the bare Pt-electrode (black line) were compared with ZnO NWs matrix on Pt-electrode (red line).

nature of ZnO matrix at the electrode interface. The result is in agreement with cyclic voltammetry measurements, further confirming the successful fabrication step of the electrochemical sensors for detection of biomolecules.

Fig.3. Cyclic voltammogram of bare platinum electrode and after growth of ZnO NWs.

Fig.4. Nyquist plots obtained of bare platinum electrode (black line) and after growing ZnO NWs (red line). Inset: the Randles circuit.

As can be seen, the bare Pt-electrode exhibited a well-defined Faradic current response for [Fe(CN)6]3/4, indicating the diffusion-controlled elctron transfer at the bare Pt-electrode surface. As the electrode covered by ZnO NWs, the magnitude of the electrochemical current response is decreased significantly leading to resistance is increased owing to the semiconducting nature of ZnO NWs matrix on Pt-electrode. Electrochemical impedance spectroscopy (EIS) is a powerful electrochemical technique used to investigate the binding events that occur at the electrode surface [18]. Therefore, any change of interface properties can be related to change in impedance spectra. Fig. 4 shows the impedance responses for two stages of surface modification of electrodes. The impedance spectra include a semicircle part at high frequency region corresponding to the electron transfer limited process and a linear part at lower frequencies resulting from the diffusion limiting step of the electrochemical process. Significant difference in the impedance spectra of ZnO NWs matrix on Pt-electrode (red line) and bare Ptelectrode (black line) were observed. The bare Ptelectrode with ZnO NWs matrix has much bigger semicircle diameter, indicating the semiconducting 329

CONCLUSION For the practical application of eletrochemical Pt electrodes based on ZnO nanowires matrix in the biosensing applications, the development of suitable sensing devices with low cost, fast response, and high sensitivity is very important. In this work, electrochemical Pt electrodes grown ZnO nanowires matrix have been successfully prepared through the hydrothermal method. The analyses confirmed that the ZnO NWs have the hexagonal crystalline structure (JCPDS card no. 361451) and with diameter in the range of 30-200 nm. The modified platinum electrodes showed much lower resistance comparing to unmodified platium eletrodes. IV.

We believe that the electrochemical ZnO NWs/Pt device holds great potential to apply for biosensing applications. ACKNOWLEDGMENT The research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 103.02-2015.43.

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REFERENCE S. L. Brooks, R. E. Ashby, A. P. F. Turner, M. R. Calder, and D. J. Clarke, Development of an On-line Glucose Sensor for Fermentation Monitoring, Biosensors, vol. 3, no. 1, pp. 45–56, 1987. K. L. M. Moran, J. Fitzgerald, D. A. McPartlin, J. H. Loftus, and R. O’Kennedy, Biosensor-Based Technologies for the Detection of Pathogens and Toxins, vol. 74. Elsevier Ltd, 2016. G. Aydoğdu, D. K. Zeybek, Ş. Pekyardımcı, and E. Kılıç, A novel amperometric biosensor based on ZnO nanoparticlesmodified carbon paste electrode for determination of glucose in human serum, Artif. Cells, Nanomedicine, Biotechnol., vol. 41, no. 5, pp. 332–338, 2013. Y. Lei, N. Luo, X. Yan, Y. Zhao, G. Zhang, and Y. Zhang, A highly sensitive electrochemical biosensor based on zinc oxide nanotetrapods for l-lactic acid detection,” Nanoscale, vol. 4, no. 11, p. 3438, 2012. M. Ahmad, C. Pan, Z. Luo, and J. Zhu, A single ZnO nanofiber-based highly sensitive amperometric glucose biosensor, J. Phys. Chem. C, vol. 114, no. 20, pp. 9308–9313, 2010. A. A. Ansari, A. Kaushik, P. R. Solanki, and B. D. Malhotra, Sol-gel derived nanoporous cerium oxide film for application to cholesterol biosensor, Electrochem. commun., vol. 10, no. 9, pp. 1246–1249, 2008. A. Kaushik et al., Iron oxide nanoparticleschitosan composite based glucose biosensor, Biosens. Bioelectron., vol. 24, no. 4, pp. 676–683, 2008. J. Yu, T. Zhao, and B. Zeng, Mesoporous MnO2 as enzyme immobilization host for amperometric glucose biosensor construction, Electrochem. commun., vol. 10, no. 9, pp. 1318–1321, 2008. M. Willander and O. Nur, Zinc oxide

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nanowires for biomedical sensing and analysis. Woodhead Publishing Limited, 2012. R. P. Singh, V. K. Shukla, R. S. Yadav, P. K. Sharma, P. K. Singh, and A. C. Pandey, Biological approach of zinc oxide nanoparticles formation and its characterization, Adv. Mater. Lett., vol. 2, no. 4, pp. 313–317, 2011. D. Albayrak and E. Karakuş, A novel glutamine biosensor based on zinc oxide nanorod and glutaminase enzyme from Hypocria jecorina, Artif. Cells, Nanomedicine, Biotechnol., vol. 44, no. 1, pp. 92–97, 2014. Z. H. Ibupoto, K. Khun, X. Liu, and M. Willander, Low temperature synthesis of seed mediated CuO bundle of nanowires, their structural characterisation and cholesterol detection, Mater. Sci. Eng. C, vol. 33, no. 7, pp. 3889–3898, 2013. J. Park et al., ZnO nanorod matrix based electrochemical immunosensors for sensitivity enhanced detection of Legionella pneumophila, Sensors Actuators, B Chem., vol. 200, pp. 173–180, 2014. A. Gupta, B. C. Kim, D. Li, E. Edwards, C. Brantley, and P. Ruffin, Zinc Oxide Nanowires for Biosensing Applications, 11th IEEE Int. Conf. Nanotechnol., no. 1, pp. 1615–1618, 2011. R. L. Woodfin, TRACE CHEMICAL Edited by. . M. Tonezzer, T. T. Le Dang, N. Bazzanella, V. H. Nguyen, and S. Iannotta, Comparative gas-sensing performance of 1D and 2D ZnO nanostructures, Sensors Actuators, B Chem., vol. 220, pp. 1152–1160, 2015. V. Perumal et al., Spotted Nanoflowers: Gold-seeded Zinc Oxide Nanohybrid for Selective Bio-capture, Sci. Rep., vol. 5, no. 1, p. 12231, 2015. C. Karunakaran, M. Pandiaraj, and P. Santharaman, Immunosensors. Elsevier Inc., 2015.

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Enhancement of Ammonia gas sensor based on SnO2/Pd bi-layer thin film Nguyen Xuan Thai1,2, Chu Manh Hung1, Nguyen Duc Hoa1, Nguyen Van Toan1, Nguyen Van Hieu1, Nguyen Van Duy1* 1

International Institute for Materials Science, Hanoi University of Science and Technology, Hanoi, Vietnam Laboratory of Volume and Flow, Vietnam Metrology Institute (VMI), N o. 08 Hoang Quoc Viet Road, Hanoi, Viet Nam *Corresponding author: [email protected]

2

Abstract: The enhancement of sensor performance for the detection of toxic gases, such as ammonia (NH3), is one of the most important technological issues for environmental pollution monitoring. In this report, the SnO 2/Pd bi-layer thin film sensors were prepared by DC magnetron sputtering method and investigated under various conditions to optimize NH3 gas response. The morphological properties, surface structures, components as well as thickness of SnO 2/Pd bilayer thin film sensors were also characterized by using Energy-Dispersive X-ray Spectroscopy (EDS), Field emission scanning electron microscopy (FESEM). In order to study the gas sensing performance of SnO 2/Pd thin film sensors, the sensors were exposed to NH3 in range of (25 ÷ 250) ppm concentration at temperature of 250 oC, 300oC, 350 oC, and 400oC. It was observed that the sensors with SnO2 (45 nm)/Pd (1 nm) showed best gas response compared to others. The highest gas response (Ra/Rg ~ 22) was achieved with 250 ppm NH3 at 300 oC. This research also examined the effects of thickness of SnO2 film layer as well as Pd film layer on the sensor response performance. The findings show that SnO2 and Pd layers play important role in the conductivity of SnO 2/Pd thin films, and thus affect the sensor response toward NH3. Keywords: Bilayer SnO2/Pd thin film, DC magnetron sputtering, NH3 gas sensors.

I.

INTRODUCTION

Technology for the detection of gaseous air pollutants has become a matter of critical importance because of many locations and industries that suffer from exposure to air pollutants. Ammonia (NH3), a highly toxic gas, is commonly used in agriculture, the food industry and the chemical industry and is known to be extremely harmful to the human body and the environment, so very sensitive detection is required to monitor this kind of gases. It is known that, upon exposure to around 50 ppm NH3 gas, the human skin, eyes, and respiratory system would be irritated [1].Thus, development of an NH3 gas sensors is an important goal that will reduce badly effect to human health and life. To achieve that objective, the development of a gas sensing material for metal oxides based semiconductor gas sensors in the most critical step in the development of such a gas sensor. Among the gas sensing materials investigated, Tin dioxide (SnO2), a wide band gap n-type semiconductor, has received much attention owing to its fascinating gas sensing properties including highly sensitive, non-toxicity, low cost, fast detection of a broad spectrum of species, such as NH3, H2S, H2, NO2, volatile organic compounds, etc. A SnO2 thin film can be produced using many 331

methods [2] including DC magnetron sputtering, thermal evaporation, reactive deposition, and the sol-gel methods. Among these methods, the DC magnetron sputtering is relative easy, cost-effective for mass production. N V Hieu et al. [2] have devoted considerable efforts to develop different metal oxides in the form of thin films for gas sensing applications. Bi-layer SnO2-WO3thin film sensors with high sensitivity and selectivity for NH3 were produced by DC sputtering. Besides, the sensing performance of NH3 gas sensors that are made of SnO2 thin films can also be greatly improved by modifying them with noble metals such as Pd, Pt, and Au [4]. Recently, Pi-Guey Su et al. [3] fabricated Pd/SnO2/RGO ternary nanocomposites by the one-pot route. However, relative NH3 gas responses (S=Ra/Rg) at 250 ppm NH3 is merely 1.4 in despite of remarkable improvement in working temperature. This work provides the two mask process to fabricate bi-layer SnO2/Pd by DC magnetron sputtering method for NH3 sensing. The thickness of each layer is investigated to optimize the sensor performance. This process is suitable for large-scale fabrication of cost-effective gas micro-sensors. The structure, morphology were also investigated to give a further understanding.

The 12th Asian Conference on Chemical Sensor (ACCS2017) II.

EXPERIMENTAL

A. Sensor fabrication Figure 1 shows the design layout and fabrication steps of a SnO2/Pd bi-layer thin film sensor. The sensors include a micro-heater, a pair of electrodes using Pt layer deposited on a thermally oxidized silicon wafer, sensing of SnO2/Pd bi-layer thin film sensors Fig. 1(A) was prepared by reactive sputtering under DC power of 30 W for SnO2 film and 10 W for Pd film. The base and working pressure were 10-6 Torr; and 5x10-3 Torr. To deposit SnO2 thin film, the Ar/O2 gas flow rate ratio was 15/15 sccm. Thickness of the SnO2 and Pd thin films were controlled by changing the deposition time. The SnO2 films were deposited for 2 min, 4 min, and 10 min, while Pd layers were 10, 20, and 40 s. Hereafter, for simplicity, the SnO2 thin film sensitized with the different thickness of Pd thin films will be referred as TP10, TP20, and TP40. In addition, the bare SnO2 sensors with different thickness of SnO2 layers will be also referred as T20, T40, and T100 respectively. Cross-section view of the sensor is shown on Fig. 1(B). As shown in Fig. 1 (B), the thin film sensor is composed of SnO2/Pd bi-layer thin film Pt micro-heater and electrodes on a stress free SiO2/Si/SiO2 diaphragm. Detailed about the sensor bilayer thin films procedure can be found in Ref. [4]. After fabricated bi-layer thin film sensors, the sensors were then annealed at 500 oC for 3h in air to ensure the stability of the

Figure 1. Design layout (A) and cross-section view of sensor’s structure (B)

sensors. The morphology of the bi-layer thin film sensors and the device geometry were characterized with the field emission scanning electron 332

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microscopy (FE-SEM model S4800). Elemental analysis was conducted using energy-dispersive Xray spectroscopy (EDS) integrated in the FE-SEM instrument. B. Gas sensing measurement The gas sensing characteristics were obtained using a flow-through technique. Detailed about the measurement system can be found in Ref.[4]. Prior to measurement, dry air was blown through the sensing chamber until reaching the stable sensor resistance. The sensor resistance was measured using a Keithley model 2602A, which is communicated to PC through UART protocol. The sensor response to the reduced gases was defined as S=Ra/Rg, where Ra and Rg are resistances of the sensor to dry air and analytic gas, respectively. In this experiment, the concentration of NH3 gas of 10000 ppm balanced in N2 is mixed with dry air as carried by using a series of mass flow controller to get a desired concentration. The sensors were studied for sensor response and response/recovery time at working temperature in rage of 250 oC to 400 o C and NH3 concentration in rage of 25 ppm to 250 ppm. Moreover, the response time is the time for Rg to reach 90% of saturated value after the gas flowed in, in recovery time is the time for Ra to reach 90% of the saturated resistance value after gas removal. III.

RESULTS AND DISCUSSION

A. Morphology and struture

Figure 2. SEM image of sensor (A), EDS spectra of bi-layer SnO2/Pd thin film (B), surface morphology of TP10 (C), surface morphology of TP40 (D), cross sectional image of 4 min 30 sec deposition of Sn target and 10 min deposition of Pd target on SiO2/Si substrate (F).

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Response (Ra/Rg)

16 14

B. Sensing characteristics to NH3 gas The gas sensing characteristics of bi-layer sensors were tested in different concentration in range of 25 to 250 ppm of NH3 at temperature of 250 oC, 300 o C, 350 oC, and 400 oC. The gas sensing characteristics of bare SnO2 and SnO2/Pd bi-layer thin film sensors were also measured to explain role of SnO2 thickness as well as the effect sensitizing Pd film on SnO2 film.The gas responses of all bare SnO2 sensors as a function of NH3 concentration at 250 oC are show in Fig. 3(A). The sensor response increases nearly linearly with increasing of NH3 concentration. The T40 sensor has the highest response, followed by T20 sensor, and T100 sensor. The gas response of T40 sensor to 25, 50, 100, and 250 ppm NH3 at 250 oC were 1.7, 3, 5.5, and 18, respectively. These values are much higher than of 1.2, 1.4, 2, 4 for T20 sensor and 1.1, 1.3, 1.5, 1.8 for

20

o

T20 T40 T100

18

2(E) and (F) are cross-section SEM images of 4.5 min and 10 min deposition time for bare SnO2 layer and Pd layer, respectively.

@250 C and 250 ppm NH3

(A)

(B) 15

o

@250 C

12 10

10

8 6

5

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The surface morphology of the SnO2/Pd bi-layer thin films was characterized using FE-SEM images; the images are shown in Fig. 2. A SEM image of the sensor shows the clear patterned micro-heater and a defined sensing area Fig. 2(A). Fig. 2(B) depicts the EDS spectra of the thin film presenting peaks of O, Si, Pt, Pd, and Sn and then confirming that Sn and O are the major elements in the film’s composition. The peaks of Si, Pt can be attributed to the SiO2 layer used to cover microheater and originated from the electrode coating. Fig. 2(C) and (D) display high magnification SEM image of TP10 and TP40 bi-layer thin film sensors deposited on thermal oxidized silicon substrate. It obvious that the particle size increases with increasing Pd time deposition. The film is porous because of polycrystalline nature of oxide derived through sputtering deposition. The SnO2/Pd boundaries became clear with increasing of Pd thickness. The Pd layer with a thickness of 0.5 nm Fig. 2(C), and 2 nm Fig. 2(D) looks like composing of discontinuous nano-granules. The average grain sizes of Pd layer with thickness of 0.5 nm and 2 nm estimate about 20 nm and 40 nm, respectively. Fig.

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Sensing material SnO2/WO3

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Table 1: Comparison of performance of NH3 gas sensor developed herein the literature Fabrication method NH3, ppm Response Ref. DC sputtering 250 7 [2]

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250

16

[5]

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nanocasting

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DC sputtering

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This work

T100 sensor at the same working temperature and range of NH3 gas concentration. Response to 250 ppm NH3 gas at 250 oC as a function of thickness of SnO2 thin film layers is presented in Fig. 3(B). Fig. 3(A), (B) reveal that the sensor with thickness of 40 nm SnO2 thin film layer is opitmal theckness for SnO2 layer. Based on above investigation, we fixed thickness of SnO2 layer that is correspondence with 4 min of deposition time for Sn target, and varied the thickness of Pd layers from 0.5, 1, and 2 nm (which are correspondence with 10, 20, and 40 s of deposition time for Pd target) to study the effect of thickness of Pd layers on sensor performance. The responses of sensor as a function of NH3 concentration at 300 oC are show in Fig. 3(C) and (D). It is obvious that Pd layer plays important role in enhanced sensor response to NH3 gas. The response of bare SnO2 thin film sensor is significantly lower than of SnO2/Pd bi-layer thin film sensors. Especially, TP10 sensor show highest response over range of (25÷250) ppm NH3 gas concentration. This values are comparable with that of SnO2 nanosheets and polypyrrole (PPy) sensors which were prepared by electrospinning method [5]. The present NH3 sensors were compared with those in the literatures [2, 4, 5, 6, 7]. The bi-layer SnO2/Pd thin film sensor exhibits the strongest response (S) because Pd exhibited a high energy of adsorption (chemisorptions) of NH3 gas. Then, we changed the thickness of Pd thin film layer from 0.5 nm, 1 nm, and 2 nm while maintaining the film thickness of SnO2 thin film layer at 40 nm. Fig4. (A) show the transient resistance of the TP10 bilayer SnO2/Pd thin film sensor as a function of time upon exposure to various NH3 gas concentrations at different temperatures in range of (250÷400) oC. The sensors can dectect low NH3 concentration to 25 ppm at all working temperatures. All the sensors manifested a good reversible response. In 334

particular, the sensors responded to NH3 gas at a relative low temperature of 250 oC. Resistance decreased upon exposure to NH3 gas and returned to the original value upon exposure to air. The results are consistent with the typical sensing characteristics of n-type semiconductor gas sensor upon exposure to reducing gas [8]. The plot of transient resistance versus time of all sensors at 300 o C also exhibit similar trend where a reversible response of sensor was observed as can be seen in Fig. 5(B). Furthermore, based resistance of SnO2/Pd bi-layer thin film (TP10, TP20, and TP40) are the same, approximatly 100 MΩ. That value is lower than that of bare SnO2 sensor, ~300 MΩ. This result show that Pd plays crucial role in enhancing the performance of the gas sensor [7]. The response of all sensors toward NH3 gas were systemically studied and compared in Fig.5. Fig. 5(A) shows response of all sensors to NH3 gas (25 ppm to 250 ppm) at 300 oC as a function of the thickness of Pd layer. For all of the sensors, the sensor response increases linearly with the NH3 concentrations in measured range and it showed also a bell-shaped variation with thickness of Pd thin film layers. However TP10 sensor showed the highest response (approximately Ra/Rg ~ 22 at 300 oC and 250 ppm) dependence on NH3 concentration. The results show also that SnO2/Pd bi-layer thin film sensors expressed the higher response to NH3 than bare SnO2 sensor. The temperature dependence of sensor response to 250 ppm NH3 of different sensors is presented in Fig.4B. For all of the sensors excepted the Pd doping sensors (TP10, TP20, TP40), the responsibility not only lower than others but increases with the increase of working temperature. This result can be attributed to role of Pd doping to sensors properties by oxygen spillover effect [9-11], which can be defined as the migration of adsorbed chemical species from the metal

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catalyst particles onto the oxide support. So far there were no any direct measurements, which confirm such as an effect for oxygen on the SnO2 surface. However, there are many reasons and indirect results to link the spill-over with enhanced catalytic activity and sensor sensitivity [2, 7, 9-12]. The sensor TP10 showed much higher response at all temperatures compared with TP20 and TP40

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sensors in Pd doping sensors and exhibited bellshaped variation with working temperature. The maximum response was achieved at approximately 300 oC, whereas TP20 was achieved at approximately 350 oC. Even though the shape of sensor response of TP40 sensor is not in bellshaped with changing of

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working temperatures, its response increases with decreasing of working temperature, but its responses are much lower than response of TP10 sensor as showing in Fig. 5(B) and its base resistances are much higher than base resistance of TP10 sensor as showing on Fig. 4(A). Base on the metal oxide semiconductor sensing mechanism [13], under air ambient, oxygen molecules could be adsorbed on the SnO2/Pd bi-layer thin film surface. Then the adsorbed oxygen molecules capture electrons from the SnO2/Pd bi-layer thin film conduction band and are changed as O- or O2oxygen ions. The captured electrons from the SnO2/Pd bi-layer thin film conduction band and are changed as O- or O2- oxygen ions. The captured electrons cause the increase of resistance of the SnO2/Pd bi-layer thin film. The adsorption reaction of oxygen species could be expressed as follows:

O2 ambience  e   O2 surface

(1)

O2 surface  e   2O  surface

(2) 335

In which O2(ambience) is the oxygen molecule in air; O2-(surface) and O-(surface) are adsorbed oxygen ions on the SnO2/Pd bi-layer surface, and eis the electron charge. When SnO2/Pd bi-layer surface, and e- is the electron charge. When SnO2//Pd bi-layer surface and e- is the electron charge. When SnO2/Pd bilayer surface is exposed to NH3 gas, the reaction between NH3 molecules and oxygen ions causes the electrons to escape from the valance band to conduction band. This claim can be explained as the following: 2𝑁𝐻3 + 3𝑂− (𝑠𝑢𝑟𝑓𝑎𝑐𝑒) → 𝑁2 + 3𝐻2 + 3𝑒 − (3) Thus, the charge carrier concentration of SnO2/Pd bilayer surface is increased as expected. However, when thickness of Pd layer film is increased (corresponding TP10, TP20, and TP40) the gas response of that sensors decreased. This can be attributed to thickness of Pd layer film can completely cover the SnO2 layer film, preventing the gas molecules diffusion and adsorption on the surface of SnO2/Pd bilayer thin film.

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Hanoi, 2017 for enhanced NH3 gas sensing performance,” Mater. Sci. Eng. B, 224 (2017) 163–170.

22

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20

[3] P. G. Su and L. Y. Yang, “NH3 gas sensor based on Pd/SnO2/RGO ternary composite operated at roomtemperature,” Sensors Actuators, B Chem., 223 (2016) 202–208.

(A) @300 oC

18 16

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[4] N. Van Hieu, L. T. B. Thuy, and N. D. Chien, “Highly sensitive thin film NH3 gas sensor operating at room temperature based on SnO2/MWCNTs composite,” Sensors Actuators, B Chem., 129 (2008) 888–895.

8 6 4

[5] Y. Li, H. Ban, and M. Yang, “Highly sensitive NH3 gas sensors based on novel polypyrrole-coated SnO2 nanosheet nanocomposites,” Sensors Actuators, B Chem., 224 (2016) 449–457.

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[6] M.-S. Park, K. H. Kim, M.-J. Kim, and Y. Lee, “NH3 gas sensing properties of a gas sensor based on fluorinated graphene oxide,” Colloids Surfaces A Physicochem. Eng. Asp., 490 (2016) 104–109.

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[7] Y. Wang et al., “NH3 gas sensing performance enhanced by Pt-loaded on mesoporous WO3,” Sensors Actuators, B Chem., 238 (2017) 473–481.

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[8] H. Liu, S. P. Gong, Y. X. Hu, J. Q. Liu, and D. X. Zhou, “Properties and mechanism study of SnO2 nanocrystals for H2S thick-film sensors,” Sensors Actuators, B Chem., 140 (2009) 190–195.

400 o

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Figure 5. Gas response as a function of the thickness of Pd films (A) and response of bare SnO2 and Pd doping sensors as a function of working temperature (B).

IV. CONCLUSION This paper reported an approach for enhancing the NH3 gas sensing properties of SnO2 sensors by sensitizing with catalytic Pd thin film. Thickness of SnO2 and Pd layer were optimized to maximize the NH3 gas response. TP10 sensor exhibited the highest sensitivity to NH3 thus should be a strong candidate for NH3 monitoring at low concentration of ppm level. The results also provide a platform for the large-scale fabrication of cost-effective, high response NH3 gas with potential applications. ACKNOWLEDGMENT This research is funded by Hanoi University of Science and Technology under project number T2017-PC-170.

[9] N. Van Toan et al., “Scalable fabrication of SnO2 thin films sensitized with CuO islands for enhanced H2S gas sensing performance,” Appl. Surf. Sci., 324 (2015) 280– 285. [10] N. Van Toan et al., “Fabrication of highly sensitive and selective H2 gas sensor based on SnO2 thin film sensitized with microsized Pd islands,” J. Hazard. Mater., 301 (2016) 433–442. [11] G. Korotcenkov, V. Brinzari, Y. Boris, M. Ivanov, J. Schwank, and J. Morante, “Influence of surface Pd doping on gas sensing characteristics of SnO2 thin films deposited by spray pirolysis,” Thin Solid Films, 436 (2003) 119–126. [12] M. Zhao, J. X. Huang, and C. W. Ong, “Diffusioncontrolled H2 sensors composed of Pd-coated highly porous WO3 nanocluster films,” Sensors Actuators, B Chem., 191 (2014) 711–718.

[13] Z. Jiao, M. Wu, J. Gu, and X. Sun, “The gas sensing characteristics of ITO thin film prepared by sol-gel REFERENCES method,” Sensors Actuators, B Chem., 94 (2003) 216– 221. [1] B. Timmer, W. Olthuis, and A. Van Den Berg, “Ammonia sensors and their applications - A review,” Sensors Actuators, B Chem., 107 (2005) 666–677. [2] N. Van Toan, C. M. Hung, N. Van Duy, N. D. Hoa, D. T. T. Le, and N. Van Hieu, “Bilayer SnO2-WO3 nanofilms

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Carbon monoxide sensing of Pd nanoparticles on the surface of hydrothermally synthesized WO3 nanorods Pham Van Tonga*, Nguyen Thi Hanha, Do Thi Thu Hanha, Luu Hoang Minha, Nguyen Duc Hoab a

Department of Physics, Faculty of Mechanical Engineering, National University of Civil Engineering (NUCE), No. 55, Giai Phong Str., Hanoi, Viet Nam b International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology (HUST), No. 1, Dai Co Viet Road, Hanoi, Viet Nam Email: [email protected]; [email protected]

Abstract: Decoration of noble metal nanoparticles (NPs) on the surface of semiconducting metal oxide nanostructured to increase material characteristics, functionalization for improving gas-sensing performance. Herein, we introduce a facile method for the decoration of Pd NPs on the surface of WO3 nanorods to enhance CO gas-sensing performance. The WO3 nanorods were synthesized by hydrothermal method and heat treated before decoration Pd NPs on the surface. The Pd NPs were decorated on the surface WO3 nanorods by direct reduction of the complex Na 2PdCl4 using Pluronic as a surfactant and reducing agent. The materials were characterized by SEM, EDS, HRTEM and XRD. The gas-sensing characteristics of bare WO3 and Pd-WO3 nanorods were tested for CO, NH3, H2, CH4 and CO2 detection at different temperatures. The results show that the gas-sensor Pd-WO3 improves performance to CO at concentration (10–200 ppm) with response–recovery time (in seconds) and high responsivity. Keywords: Keyword 1, Keyword 2, Keyword 3, Upto 5 keywords

I. INTRODUCTION Recent research has focused on the development of highly sensitive gas sensors, short response times and targeting lower detection limits for application in different files, such as disease diagnosis, military mission, environment monitoring and industrial processing control [1] [2][3]. The most interesting studies topic in the field of resistive-type gas sensors is the use of nanostructured metal-oxide semiconductor materials, such as WO3, ZnO, SnO2 and In2O3, as sensing layer; Studies indicates that the interaction between the analytical gas and the surface of the material is responsible for changing the resistance. The first study to apply tungsten oxide (WO3) material as a sensing layer revealed that WO3 material is highly sensitive to NO2 and NO [4], but not high for reducing gases, such as CO, CO2, NH3 and H2 [5]. Among the noble metals, Pd is one of the metals most commonly used as a catalyst or additive for decoration of WO3 to enhance gassensing characteristics [6]. Decoration of the surface of WO3 with Pd can be done through a number of methods. For instance, Liu et al [7] synthesized Pd nanoparticles on WO3 powders by Teflon-lined autoclave hydrothermal treatment using iodide ions as a strong adsorbate and poly as the capping agent for PdCl2 reduction. Wisitsoorat 337

et al [8] reported the decoration of Pd nanoparticles on the surface WO3 nanorods by sputter deposition followed by thermal annealing at high temperature. Chavez et al [9] decorated the surface of WO3 nanowires with Pd nanoparticles by the drop casting method. Reports dedicated to enhancement of the CO gas-sensing characteristics of tungsten oxide by surface decoration are also fairly limited despite the importance of such a gas sensor in environmental monitoring, military mission and industrial processing control applications. In this study, we introduce the facile hydrothermal synthesis of WO3 nanorods and their surface decoration with Pd nanoparticles to enhenced CO gas-sensing characteristics. The Pd NPs were decorated on the surface WO3 nanorods by direct reduction of the complex Na2PdCl4 using Pluronic as a surfactant and reducing agent. WO3 nanorods decorated with nanoparticles show excellent performance for CO gas-sensing at low concentrations ranging from 10 ppm to 200 ppm as well as fast response and recovery times. II.

EXPERIMENTAL

A. Hydrothermal synthesis of WO3 nanorods WO3 nanorods were synthesized by a hydrothermal method. In a typical synthesis, Na2WO4.2H2O (1.5 g), NaCl2 (0.5 g), and P123 (0.5 g) were dissolved in 80 ml of distilled water

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using a magnetic stirrer. pH of the solution was adjusted to 2.5 by adding a solution of HCl. This solution was poured into a Teflon-lined autoclave for hydrothermal treatment at 180 oC for 12h. After cooling to room temperature, Precipitated products were collected and washed several times using distilled water and ethanol solution by centrifugation at 4000 rpm. Finally, the collected product was air dried at 45 oC for 24 h prion to Pd decoration and characterization [10]. B. Decoration of Pd NPs on the surface of WO3 nanorods First, the WO3 nanorods were heat treated at 400 °C for 2h to activate their surface; 300 mg of the collected powers were dispersed in a 2 mL mixed aqueous solution of PdCl2 and NaCl using ultrasonic vibration and magnetic stirring. After stirring the mixture solution for several minutes, a solution of 1g of P123 dissolved in 40 mL of H2O was added to the above solution for reduction of Pd2+ into Pd nanocrystals. The reduction process was performed for 2 h in ambient atmosphere at room temperature. Finally, the products were collected and washed with ethanol through centrifugation at 4000 rpm. The morphologies of the synthesized materials were investigated by field-emission scanning electron microscopy (FESEM, JEOL 7600F) and high-resolution transmission electron microscopy (HRTEM, FEI Tecnai G2). The crystal structures of the materials were studied by powder X-ray diffraction (XRD) using CuKα X-radiation with a wavelength of 1.54178 Å. C. Gas sensor fabrication and characterization For sensor fabrication, 20 mg of the synthesized materials was gently dispersed in ethanol solution by ultrasonication. Thereafter, dispersed solution was dropped onto a thermally oxidized Si substrate equipped with a pair of interdigitated Pt electrodes. The as-obtained sensors were dried at room temperature for 2h, and subsequently heat treated at 600oC for 2h to stabilize the sensor resistance. The gas sensors were measured by a flow-through technique with a standard flow rate of 400 sccm for both dry air and balanced gas using a homemade sensing system. The sensor resistance was continuously measured during sensing measurement by using a Keithley 2700, which was interfaced with a computer. Gassensing characteristics were measured at different temperatures ranging from 250 oC to 450 oC. 338

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III.

RESULTS AND DISCUSSION

A. Materials characterization The XRD pattern of Pd-WO3 nanorods after calcination at 600 °C for 2 h (Fig. 1) displays the crystal structure of monoclinic tungsten oxide with lattice parameters of a = 0.729 nm, b = 0.7539 nm, and c = 0.7688 nm, β = 90.91° (JCPDS, 43-1035). No diffraction peak of the hexagonal structure was observed, which indicated that the hexagonal WO3 was completely transformed into the stable monoclinic WO3. The XRD pattern of Pd-WO3 nanorods exhibits typical diffraction peaks of monoclinic crystal structure of WO3 but no phase corresonding to Pd (JCPDS, 46-1043) or PdO (JCPDS, 41-1107), likely because of the extremely low Pd amount added to the nanorods [10]. .

Figure 1. XRD patterns of calcination at 600 °C for 2 h.

Pd-WO3

nanorods

after

Morphological of bare WO3 nanorods after heat treatment of 400 oC/2 h are shown in Fig. 2(A). The FE-SEM image shows that WO3 nanorods have an average diameter of about 165 nm and lengths of up to few micrometers. The surface of the WO3 nanorods was very smooth and clean. TEM images of the Pd - WO3 nanorods sample are shown in Fig. 2(B). We can see that the nanorod is not a single rod, but a bunch of small rods with an average diameter of about 25 nm. The Pd nanoparticles have diameter of about 10 nm decorated on the surface of nanorod. HR-TEM image of a Pd nanoparticle shown in Fig. 2(B) indicates the single crystallinity nature of the Palladium. From Fig. 2(B), the distance between

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two consecutive network planes is d111 = 0.24 nm, corresponding to the gap between (111) plans of cubic Pd (JSPDS, 46-1043).

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The improvement of response-recovery speed of the Pd-WO3 nanorods sensors was possibly due to the acceleration of interaction rate between CO molecules and pre-adsorbed oxygen (O2-, O-, or O2-) under the catalytic activity of Pd nanoparticles. The enhenced responsivity of the Pd-WO3 nanorods compared with that of the bare WO3 nanorods can be explained based on the spillover and Shottky barrier between Pd NPs and WO3 nanorods.

Figure 3. Comparison of the CO-sensing characteristics of bare WO3 nanorods and Pd–WO3 nanorods.

Figure 2. (A) SEM image of the bare WO3 nanorods; (B-C) TEM images of the Pd–WO3 nanorods.

B. Gas-sensing properties In our study, the CO-sensing characteristics of Pd-NPs decorated WO3 nanorods were investigated and compared with of bare WO3 nanorods (fig. 3). Both sensors decreased resistance upon exposure to CO gas, Pd-WO3 emissions of n-type semiconductors similar to bare WO3. However, decoration of Pd nanoparticles on the surface of WO3 nanorods enhanced the CO gas-sensing performance of WO3 nanorods sensor. The response S(Rair/Rgas) to 200 ppm CO at 400 o C was 2 for Pd-WO3 and 1.3 for bare WO3. The 90% response and recovery time of Pd-WO3 sensor at 400 oC were 3 and 15s, while those of bare WO3 sensors were 12 and 40 s respectively. 339

Fig. 4(A) shows the transient resistance versus time of Pd decoration on the surface of WO3 nanorods sensors upon exposure to 200, 100, 200, 25 and 10 ppm CO gas at different temperatures. At all working temperatures, the resistance of the sensors decreases when exposed to CO, and then returns to the initial value when the CO is disconnected, in contact with the dry air. This result shows that, CO molecules adsorbed on the surface of Pd-WO3 and react with oxygen ions on the surface to form carbon dioxide and return electrons that cause the sensor's resistance decrease. Increased working temperature, response time and recovery are all decreased in the measuring range. Fig. 4(B) is a graph of the temperature dependent response of the sensor at different CO gas concentrations. The results showed that the response of the sensor increased as the working temperature increased. The dependence of sensor response on the CO gas concentration is shown in Fig. 4(C). The results show that all concentration-dependent paths at different working temperatures are linearly dependent. this characteristic is advantageous for the design of electronic device read out signals

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ACKNOWLEDGMENT The current work was financially supported by Ministry of Science and Technology through the Physics Improvement Program to the year 2020 under grant No. ĐTĐL.CN.21/17. REFERENCES

Figure 4. The CO responses of Pd-WO3 nanorods sensors: (A) the change in resistance of sensor to 200, 100, 200, 25 and 10 ppm CO gas at different temperatures; (B) temperature dependence and (C) concentration dependence of sensors response, respectively.

IV. CONCLUSION We have introduced an effective facile hydrothermal method synthesis tungsten oxide nanorods and their surface decorations with the Pd nanoparticles to enhanced CO gas-sensing applications. CO sensitivity of WO3 nanorods has been enhanced by surface decoration with Pd nanoparticles. Pd nanoparticles decorated WO3 nanorods sensor can detect a very low concentrations of CO gas, down to below 10 ppm level, with short response and recovery time, for environmental pollution monitoring applications.

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[1] T. V. Dang, N. D. Hoa, N. V. Duy, and N. V. Hieu, Chlorine Gas Sensing Performance of On-Chip Grown ZnO, WO3, and SnO2 Nanowire Sensors, ACS Applied Materials & Interfaces, 7 (2016) 4828–4837. [2] K. Wetchakun, T. Samerjai, N. Tamaekong, C. Liewhiran, C. Siriwong, V. Kruefu, a. Wisitsoraat, a. Tuantranont, and S. Phanichphant, Semiconducting metal oxides as sensors for environmentally hazardous gases, Sensors and Actuators B, 1 (2011) 580–591. [3] W. Tsujita, A. Yoshino, H. Ishida, and T. Moriizumi, Gas sensor network for air-pollution monitoring, Sensors and Actuators B, 2 (2005) 304–311. [4] L. You, Y. F. Sun, J. Ma, Y. Guan, J. M. Sun, Y. Du, and G. Y. Lu, Highly sensitive NO2 sensor based on square-like tungsten oxide prepared with hydrothermal treatment, Sensors and Actuators B, 2 (2011) 401–407. [5] P. V. Tong, N. D. Hoa, V. V. Quang, N. V. Duy, and N. V. Hieu, Diameter controlled synthesis of tungsten oxide nanorod bundles for highly sensitive NO2 gas sensors, Sensors and Actuators B, 183 (2013) 372–380. [6] A. Boudiba, C. Zhang, R. Snyders, M.-G. Olivier, and M. Debliquy, Hydrogen sensors based on Pd-doped WO3 nanostructures and the morphology investigation for their sensing performances optimization, Procedia Engineering, 25 (2011) 264–267. [7] B. Liu, D. Cai, Y. Liu, D. Wang, L. Wang, Y. Wang, H. Li, Q. Li, and T. Wang, Improved room-temperature hydrogen sensing performance of directly formed Pd/WO3 nanocomposite, Sensors and Actuators B, 193 (2014) 28–34. [8] A. Wisitsoorat, M. Z. Ahmad, M. H. Yaacob, M. Horpratum, D. Phakaratkul, T. Lomas, A. Tuantranont, and W. Wlodarski, Optical H2 sensing properties of vertically aligned Pd/WO3 nanorods thin films deposited via glancing angle rf magnetron sputtering, Sensors and Actuators B, 182 (2013) 795–801. 2013. [9] F. Chávez, G. F. Pérez-Sánchez, O. Goiz, P. ZacaMorán, R. Peña-Sierra, a. Morales-Acevedo, C. Felipe, and M. Soledad-Priego, Sensing performance of palladium-functionalized WO3 nanowires by a dropcasting method, Applied Surface Science, 275 (2013) 28–35. [10] P. V. Tong, N. D. Hoa, N. V. Duy, D. T. T. Le, Nguyen Van Hieu*, Enhancement of gas-sensing characteristics of hydrothermally synthesized WO3 nanorods by surface decoration with Pd nanoparticles, Sensors and Actuators B 223 (2016) 453–460.

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Investigating NO2 sensing capabilities of the electrospun α-Fe2O3 nanofibers-based sensors Nguyen Van Hoang1,2*, Phan Hong Phuoc1, Chu Manh Hung1, Nguyen Van Hieu1,* 1

International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology (HUST), Hanoi, Vietnam 2 Department of Materials Science and Engineering, Le Quy Don Technical University, Hanoi, Vietnam *Corresponding author: [email protected]; [email protected]

Abstract: In the present work, α-Fe2O3 nanofibers are synthesized by an electrospinning method, followed by a calcination process towards the NO2 gas sensor application. Field emission scanning electron microscopy (FESEM) images shows that the typical morphology of electrospun α-Fe2O3 nanofibers looks like spider nets with the diameters of about 50-70 nm. The energy dispersive X-ray (EDX) and X-ray diffraction (XRD) measurements confirm the predicted elemental composition and rhombohedral structure of the synthesized α-Fe2O3 nanofibers, respectively. The gas sensing performances of the α-Fe2O3 nanofiber-based sensors are investigated with various NO2 concentrations ranging from 2.5 to 10 ppm at different operating temperatures between 150 and 250 oC. The maximum response of the sensors is found at 200 oC with all NO2 gas concentrations. The gas sensing mechanism of the sensor based on αFe2O3 nanofibers is also discussed in detail. Keywords: α-Fe2O3, electronspinning, nanofibers, gas sensors, NO2

I. INTRODUCTION Recently, nanofibers (NFs) have been identified as one of the most promising nanostructures for gas sensor application because of their high surface-to-volume ratio and porosity [1–4]. The sensor based on NFs often possesses a high sensitivity, fast response and recovery [3,4]. Therefore, various methods have been investigated for the preparation of the nanofibers such as drawing, template synthesis, phase separation, self-assembly and electrospinning [1]. Among them, the electrospinning method is known as a simple, versatile and low-cost approach to fabricate NFs with the multi-porous structures and large surface to volume ratio [5–8]. Numerous sensing materials such as ZnO [2,9], SnO2 [8], TiO2 [10], Fe2O3 [5,11–14], etc. were synthesized by the electrospinning. Among them, hematite (α-Fe2O3), a n-type semiconductor with band gap of about 2.2 eV, is becoming a potential gas sensing material because of its low cost and thermal stability [11–13]. The α-Fe2O3 based sensors are able to detect many gases such as NO2, NH3, H2S, H2, and CO [11,13]. The sensors based on α-Fe2O3 NFs have also been intensively developed for detecting ethanol, acetone, methanol, NH3, and H2 [5,12–14]. However, researches on α-Fe2O3 NFs-based sensors for detecting NO2, an extreme hazardous gas which can cause inflammation of lung tissues and other diseases [9], have not been reported. 341

Herein, the α-Fe2O3 NFs were fabricated by the electrospinning method, followed by an annealing process. FESEM, XRD and EDX measurements were employed to confirm the morphology, crystal structure and composition of the synthesized NFs. The sensing properties to NO2 gas of the sensors based on the α-Fe2O3 NFs were also investigated in detail. II.

EXPERIMENTAL DETAILS

A. Sample preparation Iron (III) nitrate (Fe(NO3)3.9H2O) (Xilong Chemical Co.) and polyvinyl alcohol (PVA) (Mw = 130.000) (Sigma-Aldrich Co.) were used to synthesize α-Fe2O3 NFs by means of the electrospinning method [5,12–14]. The spinnable solution was prepared by dissolving Fe(NO3)3 .9H2O and PVA in deionized water. The precursor solution was stirred at room temperature to form a homogeneous one, which was then loaded into a 10 ml syringe with a no.7 stainless needle. A voltage of 17 kV was applied between the tip of syringe and the grounded aluminum collector. The distance between the tip and the collector was fixed. As-spun fibers were finally distributed uniformly on the electrodes attached on the collector. The as-spun PVA/Fe(NO3)3.9H2O composite fibers were subsequently calcined in the air using a tube-type furnace to obtain the crystalline α-Fe2O3 NFs.

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synthesized by electrospinning method. After the thermal treatment process, the crystalline α-Fe2O3 NFs were formed [2,14] with the average diameter of about 50-70 nm as shown in Fig. 1b. The shrinkage of the fiber diameter is due to an evaporation of the solvent and PVA during annealing process. The NF surface is also rough. -Fe2O3

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B. Characterization and gas sensing measurement Hitachi S-4800 FESEM equipped with an EDX spectroscopy detector was utilized to study the mophology and composition of both as-spun spun PVA/Fe(NO3)3.9H2O fibers and annealed α-Fe2O3 NFs. The crystal structure analysis was examined by means of the Bruker D5005 diffractometer.

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Figure 1. FESEM images of (a) as-spun fibers and (b) annealed α-Fe2O3 NFs. Inset figures are lowmagnification images.

the resistances of the sensors in the NO2 gas and in dry air medium, respectively. The sensors were tested with different concentrations of NO2 gas ranging from 2.5 to 10 ppm and at the operating temperature between 150 and 250 oC. III.

RESULTS AND DISCUSSION The morphology of as-spun PVA/Fe(NO3)3.9H2O fibers and annealed α-Fe2O3 NFs are shown in Fig. 1. High magnification SEM image (Fig. 1a) displays an uniform surface of the as-spun fibers with 300 nm in diameter. Inset of Fig. 1a is low magnification FESEM image of the as-spun fibers, which exhibits the typical morphology like spider nets of the fibers 342

This is attributed to the formation of many nanograins in the fibers [5]. The inset of Fig. 1b indicates that the annealed α-Fe2O3 NFs still possess the spider-net morphology of the as-spun fibers. Fig. 2a reveals the XRD pattern of the calcined α-Fe2O3 NF sample. The XRD spectrum shows the sharp peaks at 2θ values of 23.04, 33.20, 35.45, 49.52 and 54.31 degree, which correspond to refection planes (012), (104), (110), (024) and (116), respectively. The XRD result is consistent with the rhombohedral structure of α-Fe2O3 (JCPDS card no. 33-0664). The elemental composition of α-Fe2O3 NFs is confirmed through the EDX results as shown in Fig. 2b. The spectrum reveals the presence of Si from the

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substrate, Fe and O from the NFs. There is no impurities is found in the fabricated NFs. The Fe content is quite small, compared to Si content as predicted. It is due to the α-Fe2O3 NFs dispersed across Si/SiO2 substrate with a low density as shown in Fig. 1b. The NO2 gas sensing properties of the sensors 15 10

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Figure 3. Dynamic response to different concentrations of NO2 at various operating temperatures of the sensors based on α-Fe2O3 NFs. (b) The sensitivity of the sensors based on α-Fe2O3 NFs to various NO2 concentrations as a function of operating temperatures.

based on α-Fe2O3 NFs are exhibited in Fig. 3. Fig. 3a reveals the dynamic curves of the sensor to various concentrations of the NO2 oxidizing gas from 2.5 to 10 ppm at the operating temperatures between 150 and 250 oC. When the sensor is exposed to the NO2 oxidizing gas, the resistivity of the sensors increased till a saturated level and then decreased to inital value if the gas flow was interrupted. This exhibits the typical n-type behavior of the sensors based on semiconductor metal oxides to the oxidizing gas. The sensitivity 343

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of the sensors based on α-Fe2O3 NFs to various NO2 concentrations from 2.5 to 10 ppm as a function of the operating temperature between 150 and 250 oC is depicted in Fig. 3b. The responses of the sensors based on the α-Fe2O3 NFs to all NO2 concentrations are in the volcano shape in the temperature range from 150 to 250 oC. It means that the highest performance of the NO2 sensors is obtained at the operating temperature of 200 oC. These results also indicates the raise of the sensor response corresponding to the increase of the NO2 gas concentration. The maximum response of the α-Fe2O3 NF-based sensor to 10 ppm NO2 is 6.7 at the optimal working temperature of 200 oC. In order to explain the above-mentioned gas sensing results, radial modulation and grain boundary gas sensing mechanisms must be considered [2,5,8]. When the α-Fe2O3 NFs are exposed to the air, oxygen molecules will be first adsorbed on the α-Fe2O3 NF surface. These molecules will be simultaneously diffused along grain boundaries, covering nanograins and trapping electrons from the conduction band of the NFs to generate chemisorbed oxygen species (O2−, O2−, O−). Thus, an electron-depleted layer is formed under the surface and among nanograins, resulting in the increase of the resistance of the αFe2O3 NF-based sensor. When NO2 gas is introduced to the sensing layer at the operating temperature, the NO2 molecules are absorbed on the nanofiber surfaces and diffused among nanograins, extracted more electrons by the following reaction: NO2(gas) + e− → NO2(ads)− [9], thereby broadening the electron-depleted layer, leading to a further increase of the sensor resistance. Relying on this sensing mechanism, the sensor response curvers in the volcano shape (Fig. 3b) could be explained clearly. When the operating temperature of the sensors raised to a certain value, resulting in the increase of NO2 chemisorption, reaction rate, and diffusion rate. Thus, the sensor response is enhanced. When the temperature is further increased, the NO2 desoption process takes place and therefore the the sensor response is decreased. IV. CONCLUSION To sum up, the NO2 sensors based on α-Fe2O3 NFs were successfully fabricated via electrospinning method, followed by the annealing process. The XRD analysis confirmed the rhombohedral structure of the synthesized α-Fe2O3

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NFs. The findings also indicated the typical spider-net morphology of the electrospun NFs with the average diameter of as-spun and annealed fibers of about 300 nm and 60 nm, respectively. The gas sensing properties of the sensors to NO2 were also tested. The α-Fe2O3 NF-based sensor obtained a maximum sensitivity of 6.7 times to 10 ppm NO2 at the optimal operating temperature of 200 oC. Radial modulation and grain boundary gas sensing mechanisms were discussed to explain the NO2 gas response results of the sensors.

[7]

ACKNOWLEDGMENT The current work was financially supported by Ministry of Science and Technology through the Physics Improvement Program to the year 2020 under grant No. ĐTĐL.CN.21/17.

[9]

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S. Ramakrishna, K. Fujihara, Wee-Eong Teo, T.-C. Lim, Z. Ma, An introduction to electrospinning and nanofibers, 2005. doi:10.1142/9789812567611. Z.U. Abideen, A. Katoch, J.H. Kim, Y.J. Kwon, H.W. Kim, S.S. Kim, Excellent gas detection of ZnO nanofibers by loading with reduced graphene oxide nanosheets, Sensors Actuators, B Chem. 221 (2015) 1499–1507. doi:10.1016/j.snb.2015.07.120. B. Ding, M. Wang, J. Yu, G. Sun, Gas sensors based on electrospun nanofibers, Sensors. 9 (2009) 1609– 1624. doi:10.3390/s90301609. S. Editor, D.J. Lockwood, Electrospun Nanofi bers for Energy and Environmental Applications, n.d. W. Zheng, Z. Li, H. Zhang, W. Wang, Y. Wang, C. Wang, Electrospinning route for α-Fe2O3 ceramic nanofibers and their gas sensing properties, Mater. Res. Bull. 44 (2009) 1432–1436. doi:10.1016/j.materresbull.2008.12.013. Z.U. Abideen, A. Katoch, J.H. Kim, Y.J. Kwon, H.W. Kim, S.S. Kim, Excellent gas detection of ZnO nanofibers by loading with reduced graphene oxide nanosheets, Sensors Actuators, B Chem. 221 (2015) 1499–1507. doi:10.1016/j.snb.2015.07.120.

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Hanoi, 2017 Dung, Nguyen Van; Le, Dang Thi Thanh; Trung, Nguyen Dinh; Dung, Hoang Ngoc; Hung, Nguyen Manh; Duy, Nguyen Van; Hoa, Nguyen Duc; Hieu, Nguyen Van, CuO Nanofibers Prepared by Electrospinning for Gas Sensing Application: Effect of Copper Salt Concentration, Journal of Nanoscience and Nanotechnology 16 (2016) 79107918 doi: 10.1166/jnn.2016.12747 J.Y. Park, K. Asokan, S.W. Choi, S.S. Kim, Growth kinetics of nanograins in SnO2 fibers and size dependent sensing properties, Sensors Actuators, B Chem. 152 (2011) 254–260. doi:10.1016/j.snb.2010.12.017. R. Kumar, O. Al-Dossary, G. Kumar, A. Umar, Zinc oxide nanostructures for NO2 gas sensor applications: A review, Nano-Micro Lett. 7 (2015) 97–120. doi:10.1007/s40820-014-0023-3. I.D. Kim, A. Rothschild, B.H. Lee, D.Y. Kim, S.M. Jo, H.L. Tuller, Ultrasensitive chemiresistors based on electrospun TiO2 nanofibers, Nano Lett. 6 (2006) 2009–2013. doi:10.1021/nl061197h. A.M.B.H.K. Janghorban, α-Fe2O3 based nanomaterials as gas sensors, J. Mater. Sci. Mater. Electron. (2015). doi:10.1007/s10854-015-4200-z. C. Zhao, J. Bai, B. Huang, Y. Wang, J. Zhou, E. Xie, Grain refining effect of calcium dopants on gassensing properties of electrospun α-Fe2O3 nanotubes, Sensors Actuators, B Chem. 231 (2016) 552–560. doi:10.1016/j.snb.2016.03.056. S.G. Leonardi, A. Mirzaei, A. Bonavita, S. Santangelo, P. Frontera, F. Pantò, P.L. Antonucci, G. Neri, A comparison of the ethanol sensing properties of α-iron oxide nanostructures prepared via the sol-gel and electrospinning techniques., Nanotechnology. 27 (2016) 75502. doi:10.1088/0957-4484/27/7/075502. S. Yan, G. Zan, Q. Wu, An ultrahigh-sensitivity and selective sensing material for ethanol: α-/γ-Fe2O3 mixed-phase mesoporous nanofibers, Nano Res. 8 (2015) 3673–3686. doi:10.1007/s12274-015-0867-y. N. Van Hieu, N. Van Duy, P.T. Huy, N.D. Chien, Inclusion of SWCNTs in Nb/Pt co-doped TiO2 thinfilm sensor for ethanol vapor detection, Phys. E Low-Dimensional Syst. Nanostructures. 40 (2008) 2950–2958. doi:10.1016/j.physe.2008.02.018.

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Unravelling the nanostructures of supramolecular assemblies of intermolecular bonding of Phenylboronic acid on Au(111) single crystal Pham Duc Thanh1, Ngoc Son Nguyen 1 and Thu-Hien Vu1, 2 * 1

International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, No. 1 Dai Co Viet, Hanoi, Vietnam 2 Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland *Corresponding author: [email protected]

Abstract: We study the formation of hydrogen bonding in Phenylboronic acid molecular assemblies on a Au(111) substrate surface, using cyclic voltammetry (CV) and in situ scanning tunneling microscopy (STM). Our results indicate that, at a negatively charged surface, phenylboronic molecules form highly ordered physisorbed adlayers with their phenyl rings parallel to the substrate surface. High resolution STM images reveal the packing arrangment and internal molecular structures. Linear tape pattern is composed of dimer rows of phenylboronic acid, which are stabilized by hydrogen bonds between two functional groups, B(OH)2. Increasing the electrode potential further to positive charge densities of Au(111) destabilizes all hydrogen-bonded networks of the planar adsorbed molecules. Phenylboronic acid forms disordered chemisorbed adlayers. The chemisorbed adlayer of phenylboronic acids leads to a drastic etching of the Au(111) surface. Keywords: Self-assembled structure, Au(111) single crystal, phenylboronic acid, cyclic voltammetry, electrochemical scanning tunneling microscopy

I. INTRODUCTION Basic ordering principles of a self-assembled monolayer are a compromise of (i) the ability to create strong intermolecular hydrogen bonds between adjacent molecules [1] (ii) packing constrains, (iii) the formation of interfacial stacks due to π-electron interaction [2], as well as (iv) substrate-absorbate coordination chemistry. Understanding supramolecular aggregation starting from the basic interactions of the constituent molecules is a prerequisite to eventually control the selfassembly process. At the exploring level, we performed our studies to new families of building blocks of self-assembled monolayer, such as phenylboronic acid (PhB). PhB molecules possess a -B(OH)2 functional group. Each of the hydroxyl groups bonded to the boron atom may participate in hydrogen bonds often a complex network of hydrogen-bonded molecules observed in the solid states [3]. Analogous to carboxylic acids, the most common structural motif of phenylboronic acids is a cyclic dimer generated by a pair of intermolecular hydrogen bonds. PhB is widely used in organic synthesis, catalysis [4], supramolecular chemistry, biology, medicine [5], and material science [6] as a fundamental building block. II.

EXPERIMENTAL

A. Chemicals PhB was purchased from Aldrich Chemical Co., with the highest possible grade (99%). PhB was 345

used as received. The chemical structures of PhB molecule is shown in Fig. 1. HO

B

OH

Figure 1: Chemical molecular structure of phenylboronic acid (PhB).

B. Electrochemistry The electrolyte solutions of 0.1 M HClO4 and 0.1 M HCl were prepared with Milli-Q water (18 Mcm, 3ppb TOC, HClO4 and HCl, suprapure Merck). The glassware for preparation of solutions and of the STM experiments were immersed in caroic acid (a mixture of 98% H2SO4 : 30% H2O2, v:v = 3:1) at least for 4 hours before using and followed by three cycles of rinsing and heating with Milli-Q water. The electrochemical (EC) experiments were carried out in a glass cell employing a hanging meniscus configuration. The EC cell is designed to keep an oxygen-free atmosphere and connected with two compartments for a Pt counter electrode and a trapped reversible hydrogen reference electrode (RHE). The Au(111) working electrode for EC experiments was cylinder crystals of 4 mm diameter. Before each measurement, the single crystal was annealed in a butane flame at red color for 3 to 5 min and then cooled down in a high purity argon stream (5 N,

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C. EC-STM The in situ STM experiments were carried out with a Molecular Imaging Pico-SPM using discshaped Au(111) crystals of 10 mm diameter and 2 mm height. The STM tips were prepared from a tungsten wire by electrochemical etching in 2M KOH solution and subsequent coating with polyethylene. The usual values of the tip faradic current are about 3to 5 pA. Pt wires were used as CE and quasi-reference RE. The Au(111) substrates were flame-annealed in a hydrogen flame at red color for 5 min and then cooled down slowly under argon protection. The electrodes were then immersed in 0.1 M HCl for at least 45 min for lifting reconstruction and rinsed with Milli-Q water. The solution containing target molecules was brought in contact with the atomically flat Au(111)(1×1) in the STM cell under potential control. All STM images were recorded in constant current mode with tunneling currents between 70 and 200 pA. The measurements were carried out at room temperature. III.

RESULTS AND DISCUSSION

A. Electrochemical properties The adsorption behavior of PhB was studied by CV in 0.1 M HClO4 on the Au(111) surface. The results are shown in Fig. 2. The CVs were recorded in the negative direction starting at the initial potential 0.20 V. The current responses of Au(111) in the absence of the adsorbate molecules is represented by the red line in Fig.2. The voltammograms of the bare Au(111) electrode as obtained from 0 to 1 V are consistent with CVs reported in the literatures, which indicates that a well-defined Au(111) surface is exposed to the solution [8,9]. The adsorption of organic molecules led to a distinct change in the current profiles. The black line in Fig. 2 was obtained with a solution containing 40 mM PhB. It can be seen that the 346

adsorption of the PhB molecules resulted in a reduction of the current density in the potential range 0 V < E < 0.50 V, which is labeled as region I. We note that this potential range corresponds to a negatively charged Au(111) surface [10]. A steep increase in the anodic current was observed at potentials more positive than 0.50 V and reached a maximum at around 0.70 V (P1). The backward potential scan in region II (E > 0.70 V) appears to be rather complex. No cathodic peak was found. Instead of that, two small anodic features were observed around 0.78 V and 0.98 V.

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Carbagas). The thermally-induced Au(111)(p3) of a freshly annealed electrode were lifted to obtain an atomically flat surface by immersing the electrode in 0.1 M HCl at open circuit for 30 min followed by thorough rinsing with Milli-Q water [7]. Afterwards the electrode with a droplet of water was transferred to EC. The meniscus was made at 0.10 V (RHE). All potentials in this work are quoted with respect to the RHE. An AutoLab PGSTAT-30 potentiostat was employed for the EC studies.

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II

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B. EC- STM studies Steady-state in situ STM measurements were carried out to explore structural details of the electrochemical experiments. In the following, structural details of these adlayers will be discussed. 1. 2D physisorbed adlayer, linear tape pattern in the region I of PhB Assembling PhB from aqueous solution at E = 0.10 V reveals a highly ordered "linear tape" structure of PhB on the Au electrode. Well-defined domains with parallel rows were observed, and the average domain size was about 40×40 nm2. Fig. 3 A and B display the typical organization of the linear tape pattern on Au(111)(1×1) and Au(111)-(p×3) surfaces, respectively. The molecular rows cross each other at an angle of 85 ± 5o. High resolution STM images, such as in Fig. 4A enable us to identify the internal structure and orientation of PhB molecules adsorbed on the

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gold surface. Each PhB molecule appears as rodlike protrusions with the dimensions of about (8 Å× 5 Å). From the molecular structure one can assume that each molecule adsorbs on Au(111) in a planar-orientation as in the case of benzene [11] or carboxylic acids such as benzoic acid [12,13], trimesic acid [14], terephthalic acid [15] or isophthalic acid [16] on noble metal surfaces. In addition, the cross-section profile (Fig. 4B) indicates that the apparent height of PhB layer is 0.80  1.15 Å. This value is typical for flat-lying aromatic molecules physisorbed onto the metal surfaces, which reinforces the above mentioned assumption.

imaging. However, we found that the PhB molecules form an identical structure on the reconstructed Au(111)-(p×3) surface as depicted in Fig. 3B. These experiments also show that the main rows of the linear tape structure are aligned either 60 or 120 o with respect to the {112} directions of the substrate surface. On the basis of the intermolecular distance and the flat oriented aromatic molecule, we assume a preferential location of the phenyl ring of PhB on the 3-fold hollow sites of the hexagonal substrate lattice. We propose a schematic structure model sketched in Fig. 4C for the linear tapes of the PhB layer. The molecular model shows typical lengths, angles of [011][112] B intermolecular hydrogen bonding, and all the PhB A molecules occupy 3-fold substrate coordination sites. The model is consistent with the experimental results and is also supported by the crystallographic data [18]. The PhB adlayer on Au(111) is stable in the potential range 0 V < E < 0.50 V. No other PhB adlayers were found at potentials more negative Figure 3: Large scale STM images of the linear tape than 0 V. structure of PhB on Au(111)-(1×1) (A) and on Au(111)(p×3) in 0.1 M HClO4 (B); Es = 0.10 V, iT = 70 pA and Ebias = 0.10 V.

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The intermolecular distances across and along the molecular rows were estimated by analyzing the set of high resolution STM images. We obtained (0.96 ± 0.05) nm and (1.15± 0.02) nm, respectively. The former value is attributed to the separation of PhB molecules aligned in parallel rows. The latter value, which is slightly larger than the former one, is assigned to the longitudinal intermolecular distance. We proposed that these "linear tapes" are composed of a well-ordered PhB molecules, in which each PhB molecule is bound to one adjacent molecule through a pair of OHO hydrogen bonds as a dimeric unit of the self-complementary (B(OH)2) group [3,17]. We identified an experimental rectangular unit cell with the following dimensions: side length a = (0.96 ± 0.05) nm; b = (2.2± 0.02) nm and enclosed angle α = 85 ± 5 o, as illustrated in Fig. 4A. The unit cell consists of two planar PhB molecules. The area per molecule is estimated as Aexp = (1.05 ± 0.11) nm2, corresponding to a surface coverage, Γexp = (1.58 ± 0.18)×10-10 mol·cm-2. The registry between the linear tapes of the PhB adlayer and the Au(111)-(1×1) surface could not be obtained ambiguously from the direct experimental

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2. Disordered chemisorbed PhB adlayer in region II After resolving the linear tape structure in region I, the substrate potential was changed from 0.60 V to 0.95 V into the region II (Fig. 5). This potential region causes the desorption of the 2D physisorbed layer starting at E ≥ 0.60 V (Fig. 5A), accompanied

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by the formation of a new yet temporal striped pattern on the gold surface as indicated by the white arrows, Fig. 5B, D. Concurrently with the appearance of the new stripe pattern, the gold surface also undergoes drastic changes. Small, and deep pits occur. With progressing observation time, the pits develop anisotropically and broaden, as

well as increase in depth. Two examples are indicated by the white dotted ovals in Figure 1.4D. Despite of this strong "surface-etching", on some of these areas, traces of the striped pattern still exist. This suggests that the new phase mainly contributes to the "etching" process. After 18 min at 0.95 V, the two step edges used as a marker in Fig. 5A-C can

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not be recognized anymore (Fig. 5E). In order to prevent further etching process, the substrate potential was stepped back to 0.60 V, i.e. into the region I. Fig. 5E shows an improved contrast of the surface morphology (the upper part) as obtained immediately at E = 0.60 V. No increase in the size of the holes was observed. A cross-section profile, as taken at the upper part of Fig. 5E, indicates that gold surface was restructured over several tens of nm in lateral direction and up to 5 atomic layers of Au(111) in depth. Such a destructive interaction of a chemisorbed adlayer with Au(111) does not occur in case of benzoic acid since the deprotonated COO- group is directly bound to gold atoms. Pronounced surface etching was also reported in adsorption studies of alkanethiols where the S-Au is strong enough that Au-Au bonds could break upon reductive desorption [19,20]. 348

IV.

CONCLUSION

In situ STM combined with cyclic voltammetry was employed to study the self-assembly of PhB and of three hydroxyquinoline isomers on an Au(111) electrode surface in 0.1 M HClO4. Despite the extensive use of PhB in other areas of molecular recognition, to our limited knowledge, so far there is no report related to self-assembly of monolayers of these molecules at metal surface in aqueous solutions. Our results indicate that, at a negatively charged surface, which corresponds to region I in the CVs, PhB molecules form highly ordered physisorbed adlayers with their phenyl rings parallel to the substrate surface. High resolution STM images reveal the packing arrangement and internal

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molecular structures. Linear tapes of the PhB adlayer are composed of parallel rows of dimers, in which two PhB molecules are bound through a pair of O-H···O hydrogen bonds. Increasing the electrode potential further to positive charge densities of Au(111) destabilizes all hydrogenbonded networks of the planar adsorbed molecules. PhB molecules form disordered chemisorbed adlayers. The chemisorbed adlayer of PhB leads to a drastic etching of the Au(111) surface. ACKNOWLEDGMENT The current work was financially supported by the Hanoi University of Science and Technology (Code: T2017-LN-xxx). REFERENCES [1] J. Tao, Z. Shi, Monolayer Guanine and Adenine on Graphite in NaCl Solution: A Comparative STM and AFM Study N., J. Phys. Chem. 98 (1994) 1464–1471. [2] F. Cunha, N.J. Tao, Surface Charge Induced OrderDisorder Transition in an Organic Monolayer, Phys. Rev. Lett. 75 (1995) 2376–2379. [3] J. Fournier, T. Maris, J.D. Wuest, W. Guo, E. Galoppini, Molecular Tectonics . Use of the Hydrogen Bonding of Boronic Acids To Direct Supramolecular Construction, J. Am. Chem. Soc. 125 (2003) 1002–1006. [4] N. Miyaura, A. Suzuki, Palladium-Catalyzed CrossCoupling Reactions, Chem. Rev. 95 (1995) 2457–2483. [5] S.K. Kumar, E. Hager, C. Pettit, H. Gurulingappa, N.E. Davidson, S.R. Khan, Design, Synthesis, and Evaluation of Novel Boronic-Chalcone Derivatives as Antitumor Agents, J. Med. Chem. 46 (2003) 2813–2815. [6] A.P. Côté, Porous, Crystalline, Covalent Organic Frameworks, Science 310 (2007) 1166. [7] D.M. Kolb, Phase transition in uracil adlayers on electrochemically prepared island-free Au ( 100) - (1 × 1 ), J. Electroanal. Chem. 394 (1995) 271–275. [8] Y. Ikezawa, R. Sekiguchi, T. Kitazume, Adsorption of benzoic acid on Au (111) and Au (110) electrodes in acidic media by IRAS, Electrochim. Acta. 46 (2000) 731– 736.

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[9] D.M. Kolb, J. Schneider, SURFACE RECONSTRUCTION IN ELECTROCHEMISTRY: Au100, Au111 and Au110, Electrochim. Acta. 31 (1986) 929–936. [10] U.W. Hamm, D. Kramer, R.S. Zhai, D.M. Kolb, The pzc of Au (111) and Pt (111) in a perchloric acid solution : an ex situ approach to the immersion technique, J. Electroanal. Chem. 414 (1996) 85–89. [11] S. Chiang, Scanning Tunneling Microscopy Imaging of Small Adsorbed Molecules on Metal Surfaces in an Ultrahigh Vacuum Environment, Chem. Rev. 97 (1997) 1083–1096. [12] T.-H. Vu, T. Wandlowski, CV and in situ STM study the adsorption behavior of benzoic acid at the electrified Au(100)| HClO4 interface: Structure and dynamics, J. Electroanal. Chem. 776 (2016) 40–48. [13] T.-H. Vu, T. Wandlowski, Self-assembled structures of Benzoic acid on Au(111) surface, J. Electron. Mater. 46 (2017) 3463. [14] G. Su, H. Zhang, L. Wan, C. Bai, T. Wandlowski, Potential-Induced Phase Transition of Trimesic Acid Adlayer on Au ( 111 ), J. Phys. Chem. B. 108 (2004) 1931–1937. [15] S. Clair, A.P. Seitsonen, H. Brune, K. Kern, J. V Barth, STM Study of Terephthalic Acid Self-Assembly on Au(111): Hydrogen-Bonded Sheets on an Inhomogeneous Substrate, J. Phys. Chem. B. 108 (2004) 14585–14590. [16] Z. Li, T. Wandlowski, Structure Formation and Annealing of Isophthalic Acid at the Electrochemical Au (111)-Electrolyte Interface, J. Phys. Chem. C. 113 (2009) 7821–7825. [17] P.R. Parry, C. Wang, A.S. Batsanov, M.R. Bryce, S. Sands, C. Ts, Functionalized Pyridylboronic Acids and Their Suzuki Cross-Coupling Reactions, J. Org. Chem. 67 (2002) 7541–7543. [18] J.R.A.N.D. James, J. Rettig, J. Rettig, Crystal and molecular structure of phenylboronic acid, C6H5B(OH), Can. J. Chem. 1419 (1977) 3071–3075. [19] C. Schonenberger, J.A.M. Sondag-Huethorst, J. Jorritsma, L.G.J. Fokkink, What Are the “Holes” in SelfAssembled Monolayers of Alkanethiols, Langmuir. 10 (1994) 611–614. [20] J.A.M. Sondag-Huethorst, C. Schonenberger, L.G.J. Fokkink, Formation of Holes in Alkanethiol Monolayers on Gold, J. Phys. Chem. 98 (1994) 6826–6834.

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H2S Sensing Characteristics of Self-heated Ag-coated SnO2 nanowires Trinh Minh Ngoc1, Hugo Nguyen2, Chu Manh Hung1, Nguyen Ngoc Trung3, Nguyen Van Duy1,* 1

International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology, No. 1 Dai Co Viet, Hanoi, Vietnam 2 Uppsala University, Department of Engineering Sciences, Lägerhyddsvägen 1, 751 21 Uppsala, Sweden 3 School of Engineering Physics, Hanoi University of Science and Technology, No. 1 Dai Co Viet, Hanoi, Vietnam * Corresponding author: [email protected]

Abstract: The H2S gas sensing characterization of gas sensors based on the SnO2 nanowires network has been reported by several research groups. However, the self-heated gas sensor using Ag-coated SnO2 nanowires network for sensing H2S was investigated the first times. In this study, we will report on the effected of density SnO2 nanowires network on H2S sensitivity. The SnO2 nanowires network density can be controlled by the distance between sensor electrodes. After SnO2 nanowires decorated with Ag, the results show that the H2S gas sensing properties depend on the density of the SnO2 nanowires network. As the density of SnO2 nanowires network increases, the response of sensors decreases. The sensor can operate at as low power as 2 mW to H2S gas concentration of 0.25 ppm. The response and recovery times of sensor are about 200 s. Moreover, working at low operating power gives us the benefit of energy saving as well as the elongation of lifetime.

material. The results showed that the sensitivity of the sensor was improved, high selectivity and rapid response and recovery time [9,10]. The results of Pankaj et al showed that the process of fabrication Ag-SnO2 sensor technology was simpler [11], response and recovery time were fast. However, the gas response was low. H2S gas sensor have also been studied and published by our research team [12]. The results of the study showed that the resistance of the sensor was very high. The approach of the self-heated gas sensor is to reduce the power consumption of the sensor, therefore, this H2S gas sensor would not be suitable for self-heated gas sensor. The disclosures showed that the power load of the sensor was very low when using individual nanowire [13-15]. Comparative results of the self-heated gas sensor performance using individual nanowire, multi nanowires and nanowires network have also reported the same result [16].

1. INTRODUCTION We all know that H2S is a toxic gas that affects directly on the respiratory system through inhalation, which in turn causes the depletion of brain cells [1]. On the other hand, the sources of pollution are increasing and diversifying due to the over exploitation and use of fossil fuels. Identifying high concentrations of pollutants can be easily accomplished with portable equipment, but with continuous low emission sources (< 1 ppm) remains a challenge, requires scientists to continue researching. Recent publications showed that the nanostructured materials (SnO2, ZnO, WO3) are still ideal materials for general gas sensors and H2S gas sensors in particular and for enhanced sensitivity, selectivity, reduced response and recovery time, many metals have been studied for catalyst, doped. Although the large number of publications showed that the SnO2-CuO or ZnO-CuO materials are used popularly as denatured material [2-4], these sensors still have weak-points such as high resistances, slow response and recovery time [5-7]. Therefore, Ag is also a noble metal studied to improve to H2S gas sensing properties of SnO2 nanowires sensor.

In the recent publication [16,17], we have initially studied the H2S gas sensing characteristic of self-heated gas sensors using the pure SnO2 nanowires network. However, the power consumption of the sensor was rather high and the sensors had low response. Thus, in this study, we developed a self-heated gas sensor with Ag doped SnO2 nanowires network to enhance the H2S gas sensing properties. With the control of nanowire density, the power consumption is expected to reduce remarkably.

Lantto et al reported result with Ag-doped SnO2 thin-film sensors, which showed that the sensor worked well [8]. The research team of Ji-Wook Yoon and Ji-Wook Yoon also published the study results of the H2S gas sensors, the sensors were fabricated the basis of Ag doped SnO2

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2. EXPERIMENTAL

3. RESULTS AND DISCUSSION

The fabrication process of sensor structure is described as the follows: Platinum electrodes are patterned on heatresistant glass substrates of the size 15 mm x 10 mm, 0.5 mm thick and structured as shown in Fig. 1. The sensor symbols are G2, G5 and G10. The distance between electrodes are 2µm, 5 µm and 10 µm. The source material is pure metal 99.8% tin metal from SigmaAldrich.

The SEM images of the SnO2 nanowires network sensor are shown in Figure 2. The results from the SEM image of Fig. 2(a) showed that the SnO2 nanowires density in all three sensors was different. The nanowires density of G2 and G5 is larger than that of G10. In all three sensors, we controlled that the SnO2 nanowires growth only from the edge of the electrode and that the lengths range from a few μm to about 30 μm. The nanowires grown from the two electrode sides come in contact with each other to create the junctions. Therefore, the temperature generated by the Jule effect will only be concentrated at the center space of the electrodes. Figure 2(b) shows the diameter of the SnO2 nanowires in all three sensors < 50 nm. The coated Ag material on nanowires surface is observed in Fig. 2(c) as Ag nanoparticles.

Figure 1: SEM images of the sensor electrodes.

(a)

The SnO2 NWs network was fabricated by on-chip growth on the electrode by thermal CVD method. The weight of the source material is about 0.1 g in the refractory quartz boat placed at the center of the quartz tube of a horizontal furnace. To control the density of Sn during manufacture, we used a heat-resistant quartz plate to cover part of the surface of the quartz boat, after which the electrodes were placed on the quartz plate. The entire system is cleaned with Ar gas at a flow rate of 300 sccm for 5 min. The CVD process was retained at temperature of 730 °C, the growth time of 20 min, the O2 gas flow of 0.5 sccm, and the pressure of 1.8x10-1 torr. The heating rate was 36 °C/min. After the above process, the furnace was cooled down to room temperature. To enhance the H2S sensing properties, a very thin Ag metal was coated on SnO2 NWs by sputtering method at a DC power of 10 W in 20 s. After sample sputtering was treated at 350 °C, for a period of 2 h to improve the Ag-SnO2 NWs contact.

(b)

The morphology of the SnO2 NWs network was observed by scanning electron microscopy (SEM). The sensors then were studied their H2S sensing properties at different conditions. The electric supply power was kept constant during each measurement for remaining sensor working temperature.

(c) Figure 2: (a, b) SEM images of SnO2 NWs network sensors, (c) Ag decorated SnO2 NW.

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The 12th Asian Conference on Chemical Sensors (ACCS2017) The H2S gas concentrations were selected to research the sensing properties of 0.25, 0.5, 1 and 2 ppm. The plots in Fig. 3(a, b, c) show that the resistance of the G2, G5 and G10 sensors after stabilization has increased due to the spacing between the electrodes, which is perfectly adequate because of the nanowire density SnO2 between electrodes decreases from G2 sensor (SnO2 nanowires density of G10 sensor is smallest). At the same power loads of 8 mW, the response increases as the H2S concentration increases. In particular, at the same power loads and H2S gas concentration, the response of the G10 sensor is greater than the response of the G5 and G2 sensors, Fig. 3(d). This can be explained as follows: Firstly, when the junction diminishes, the same supply power will cause the temperature at the junctions to be higher. Secondly, when the junctions density is high, the temperature at the junction points is lower and the heat loss is greater due to the heat transfer [18].

Hanoi, 2017 In Fig. 4 (c, d) shows that, as the power loads of the sensor decreases, the response time increases. The greater the junctions density, the slower the response time. The explanation for the above results can be based on the reaction equation: Ag2O + H2S → Ag2S + H2O Ag2S + 3/2 O2 → Ag2O + SO2

(a)

(c) (a)

(1) (2)

(b)

(d)

(b) Figure 4: The response to H2S gas of sensors as a function of loading power (a, b) and response time, recovery time (c, d).

(c)

When the sensor operates at low power, it corresponds to the low working temperature [17]. Reaction according to the trend of equation (1), i.e., the preferred reaction occurs in the direction of the Ag2S formation (causing the sensor resistance decreases) and almost no desorption of Ag2S to return to Ag2O. Therefore, at low power consumption, the sensitivity of the sensor is much greater than that at the higher power. Interestingly, depending on the requirement of high gas sensitivity or fast response, we could choose the applied power for the sensor.

(d)

Figure 3: Dynamic gas response characteristics at loading power of 8 mW of sensors G2 (a), G5 (b), and G10 (c) and the summary of gas response (d).

4. CONCLUSION

To investigate the H2S gas sensing properties of the sensor depend on power consumption, we chose the G10 sensor with power loads range of 2 mW - 10 mW. The results in Fig. (4a) show that the sensor response decreases as the power loads increases, with the maximum response at 2 mW, about 6 times. It proved that the power consumption of the sensor influences the gas sensing properties. Both the G2 and G5 sensors also have the similar properties that the sensor response increases when the power consumption is reduced as in Fig. (4b).

Research results show that the self-heated sensor with the Ag doped SnO2 nanowires network fabricated with simple process. The sensor can operate at low power consumption and detect low H2S concentration at the power consumption of only 2 mW. However, it needs further study for the application of the fabricated sensor in the future.

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ACKNOWLEDGEMENT

Films for the evaluation of H2S Gas Sensing Properties, PhysicaB: Physics of Condensed Matter, 524 (2017) 90-96.

This research is funded by the Vietnam National Foundation for Science and Technology Development (NAFOSTED) under Grant No. 103.02-2015.88.

12. Nguyen Van Toan, Nguyen Viet Chien, Nguyen Van Duy, Dang Duc Vuong, Nguyen Huu Lam, Nguyen Duc Hoa, Nguyen Van Hieu, Nguyen Duc Chien, "Scalable fabrication of SnO2 thin flim sensitized with CuO islands for enhanced H2S gas-sensing performance", Applied Surface Science, 324 (2015) 280-285.

REFERENCES

13. J. D. Prades, R. Jimenez-Diaz, F. Hernandez-Ramirez, S. Barth, A. Cirera, A. Romano-Rodriguez, S. Mathur, and J. R. Morante, Ultralow power consumption gas sensors based on self-heated individual nanowires, Applied Physics Letters, 93 (2008) 123110-123112.

1. U.S. Department of Health and Human Services, Toxicological profile for hydrogen sulfide and carbonyl sulfide, 2016. 2. Sudhir Kumar Pandey, Ki-Hyun Kim, Kea-Tiong Tang, A review of sensor-based methods for monitoring hydrogen sulfide, Trends in Analytical Chemistry, 32 (2012) 87-99.

14. P. Offermans, H. D. Tong, C. J. M. van Rijn, P. Merken, S. H. Brongersma, and M. Crego-Calama, Ultralow-power hydrogen sensing with single palladium nanowires, Applied Physics Letters, 94 (2009) 223110-223112.

3. Hyo-Joong Kim, Jong-Heun Lee, Highly sensitive and selective gas sensors using p-type oxide semiconductors: Overview, Sensors and Actuators B, 192 (2014) 607–627. 4. Eduard Llobet, Jérôme Brunet, Alain Pauly, Amadou Ndiaye and Christelle Varenne, Nanomaterials for the Selective Detection of Hydrogen Sulfide in Air, Sensors, 17 (2017) 391-409.

15. Junyoung Seo, Yeongjin Lim, Heungjoo Shin, Selfheating hydrogen gas sensor based on an array of single suspended carbon nanowires functionalized with palladium nanoparticles, Sensors and Actuators B:Chemical, 247 (2017) 564-572.

5. Nguyen Minh Vuong, Nguyen Duc Chinh, Bui The Huy & Yong-Ill Lee, CuO-Decorated ZnO Hierarchical Nanostructures as Efcient and Established Sensing Materials for H2S Gas Sensors, Scientific Reports, 6 (2016) 2673626748.

16. Nguyen Duc Chinh, Nguyen Van Toan, Vu Van Quang, Nguyen Van Duy, Nguyen Duc Hoa, Nguyen Van Hieu, Comparative NO2 gas-sensing performance of the self-heated individual, multiple and networked SnO2 nanowire sensors fabricated by a simple process, Sensors and Actuators B, 4 (2014) 7-12.

6. Janosch Kneer, Stefan Knobelspies, Benedikt Bierer, Jürgen Wöllensteina, Stefan Palzer, New method to selectively determine hydrogen sulfide concentrations using CuO layers, Sensors and Actuators B, 222 (2016) 625–631.

17. Ha Minh Tan, Chu Manh Hung, Minh Ngoc Trinh, Hugo Nguyen, Nguyen Duc Hoa, Nguyen Van Duy, Nguyen Van Hieu, Novel self-heated gas sensors using on-chip networked nanowires with ultralow power consumption, ACS Appl. Mater. Interfaces, 9 (2017) 6153–6162.

7. Annanouch, F.E.; Haddi, Z.; Vallejos, S.; Umek, P.; Guttmann, P.; Bittencourt, C.; Llobet, E. Aerosol-Assisted CVD-Grown WO3 Nanoneedles Decorated with Copper Oxide Nanoparticles for the Selective and Humidity-Resilient Detection of H2S, ACS Appl. Mater. Interfaces, 7 (2015) 6842– 6851.

18. Evgheni Strelcov, Serghei Dmitriev, Bradley Button, Joshua Cothren, Victor Sysoev and Andrei Kolmakov. Evidence of the self-heating effect on surface reactivity and gas sensing of metal oxide nanowire chemiresistors; Nanotechnology, 19 (2008) 355502-355506.

8. V. Lantto and J. Mizsei, H2S monitoring as an air pollutant with silver-doped SnO, thin-film sensors, Sensors and Actuators B, 5 (1991) 21-25. 9. Ji-Wook Yoon, Young Jun Hong, Yun Chan Kang and Jong-Heun Lee, High performance chemiresistive H2S sensorsusing Ag-loaded SnO2 yolk–shell nanostructures, RSC Adv., 4 (2014) 16067–16074. 10. Kwang Soo Yoo, Soo Deok Han, Hi Gyu Moon, SeokJinYoon and Chong-Yun Kang, Highly Sensitive H2S Sensor Based on the Metal-Catalyzed SnO2 Nanocolumns fabricated by Glancing Angle Deposition, Sensors, 15 (2015) 1546815477. 11. Pankaj S. Kolhe, Pankaj M. Koinkar, Namita Maiti, Kishor M. Sonawane, Synthesis of Ag Doped SnO2 Thin

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Synthesis and Photocatalytic Activity of (N, Ta) Co-doped TiO2 Nanopowders Vu Duy Thinh 1, Ngo Thi Hong Le,2 1

Hanoi University of Mining and Geology 18 Pho Vien – Duc Thang, Tu Liem North, Hanoi, Vietnam 2 Institute of Materials Science, Vietnam Academy of Science and Technology 18 Hoang Quoc Viet Road, Hanoi, Vietnam *Corresponding author: [email protected]

Abstract: TiO2 has the most efficient photoactivity, the highest stability and the lowest cost, safety to humans and the

environment. But TiO2 has high recombination rate of electron-hole and absorbs only the ultraviolet radiation, make up 4% of solar radiation due to this material has large band gap (3.2 eV). To improve the performance of TiO 2 is to increase its optical activity, one found out method of TiO2 material structure changing with other doped elements to reduce the band gap and shift the absorption wavelength to visible light region. In this paper, nitrogen and tantalum co-doped TiO2 nanopowders were fabricated by hydrothermal method, followed by calcination at 300oC for 1 h. The results showed that the single phase of anatase TiO2 with particle size of about 20 nm was obtained in all samples. The effects of N and Ta co-doping on the average grain size and strain were also detected by micro-Raman spectroscopy. Comparing to the case of pure TiO2, nitrogen and tantalum co-doped nanopowders exhibited a higher visible light photocatalytic activity for degradation of methylene blue. Keywords: TiO2, photocatalysis, co-doping, hydrothermal, Raman spectra.

INTRODUCTION In recent years, photocatalytic semiconductors have been studied intensively in both senses of basic research and applications [1]. TiO2 is known as one of the most promising photocatalytic materials for clean energy technology and environmental remediation due to its high stability and low cost, safety to humans and environment. However, the pure TiO2 demonstrated a high recombination rate of electron-hole and absorbs only the ultraviolet radiation due to its relative large band gap (3.2 eV) [2, 3]. Therefore, the investigations on narrowing the band gap and enhancing the photocatalytic activity of TiO2 photocatalysts are necessary and crucially important. Various material engineering solutions have been designed, such as doping of metals and non-metals [4-8]. Non-metal doping of TiO2 has shown a great promising in achieving visible light active photocatalysis. Among them, nitrogen was found as the most potential dopant [9, 10]. It originated from the fact that nitrogen and oxygen are similar to in atomic size, especially, nitrogen has small ionization energy and high stability. As a result, nitrogen can be easily entered into the TiO2 structure. However, it was reported by many researchers that N-doped TiO2 exhibited a poor photocatalytic efficiency due to the 2p states of nitrogen atoms are strongly localized at the top of valence band. This facilitated their isolated empty states tend to trap photogenerated electrons, I.

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leading to the reduction of photogenerated current [5, 11]. Besides, mono-doping TiO2 with transition metals may act as recombination sites for the photo-induced charges thus lowering the quantum efficiency. To resolve these problems and enhance the photocatalytic activities of TiO2, we co-doped N and Ta ion into the lattice of this compound. By incorporating both Ta and N with suitable concentrations, the neutralization of positive and negative charges, the decrease in oxygen vacancy and the increase of the photo-generated holes provided a low recombination rate of photoinduced charges. Up to now, there are few reports about the enhancement in photocatalytic activity of a Ta and N co-doping [4, 12-14]. In this work, by using a simple hydrothermal synthesis procedure, the (Ta, N) co-doped TiO2 nanopowders were prepared with higher photocatalytic performances under visible light irradiation than those of un-doped, and nitrogen doped TiO2. The effects of N and Ta co-doping on the microstructure properties, namely, average grain size, strain, of the obtained samples were also investigated. EXPERIMENTAL The synthesis of (Ta, N) co-doped TiO2 nanopowders was similar to that described elsewhere [12]. Briefly, the hydrolyzed product of titanium (IV) tetraisopropoxide was II.

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hydrothermally treated at 210oC in a 100-ml Teflon-lined stainless steel autoclave for 24 h. The obtained powders were then washed with distilled water and dried at 100oC. To receive nitrogen (N) doped TiO2 powders, same procedure was applied with the exception that the hydrolysis of the titanium (IV) tetraisopropoxide was processed in a mixture of deionized water and ammonium hydroxide. The synthesis of (N, Ta) co-doped TiO2 is slightly differed from the above-mentioned second procedure by using aqueous mixture of ammonium hydroxide, tantalum, and hydrofluoric as a medium for the hydrolysis of the titanium (IV) tetraisopropoxide instead of a mixture of deionized water and ammonium hydroxide only. The obtained product was the (N, Ta)-TiO2 powders. All of samples were annealed at 300oC for 1 hour. The photocatalytic activity of undoped and doped TiO2 powders was tested for the degradation of methylene blue (MB) in an aqueous solution under illumination of UV-VIS light (mercury-xenon vapor lamp of Japan with 15 mW/cm2) and an optical filter >420 nm. In a typical experiment, the undoped and doped TiO2 powders were added into aqueous solution of MB, and the initial MB concentration and the amount of TiO2 were fixed at 2.10-5mol.L−1 and 3g.L−1, respectively. The degradation of MB was calculated via the absorbance of the remaining MB by formula: Degradation = (C0-C)/C0, where C0 and C were the concentration of the initial and remaining MB, respectively. The obtained samples has been measured by the Raman scattered light that was dispersed by an imaging spectrometer (HORIBA Scientific; iHR320) and detected by a back illuminated, deepdepletion, liquid-nitrogen cooled CCD detector (Princeton Instruments); The morphology and particle size were observed by Field Emission Scanning Electron Microscopy (FE-SEM, Hitachi S-4800 microscope); The surface area of the nanoparticles were estimated on a Quantachrome instrument (AutosorbiQ-MP) based on the BET (Brunauer-Emmett- Teller) method with a Nitrogen adsorption. The absorption spectra were measured by using a UV-VIS (JASCO V-550) spectrometer. RESULTS AND DISCUSSION The effects of the N and (N, Ta) co-doping on crystal structure of TiO2 fabricated by hydrothermal method was analyzed by microIII.

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Raman spectroscopy at room temperature. As shown in Figure 1(a), one can observe five dominant peaks at 145 cm-1 (Eg), 196 cm-1 (Eg), 398 cm-1 (B1g), 516 cm-1 (B1g/A1g) and 640 cm-1 (Eg), which are assigned to the six Raman active modes of TiO2 anatase phase [15]. This result is in good agreement with the obtained XRD results in our previous work [12]. The shift can be determined from the peak position of the main Eg mode at 145 cm-1. In Figure 1(b) and 1(c), comparing to the Raman spectrum of the pure TiO2, it is clear that the predominant Raman bands shifted towards lower wavenumber for the N doped TiO2 and longer wavenumber for the (N, Ta) co-doped TiO2 and their intensities decrease drastically. In order to observe variations of position of Eg mode in different samples, the position and the full width at half maximum are presented in Table 1. Based on the structural characteristics of TiO2 nanopowders, key factors can contribute to the changes in the peak position of the Eg mode in anatase TiO2 that can be determined in Raman spectra: strain from doping N, Ta into TiO2 nanoparticles, particle size, and particle size distribution. For the co-doping of nitrogen and tantalum into TiO2, N3- substitutes O2- site and Ta5+ substitutes Ti4+ site, which form N-Ta-O bonds, in the lattice. The ion radius of N3ions (1.46 Å) is higher than that of O2- ions (1.40 Å) and Ta5+ ions (0.68 Å) is larger than Ti4+ ions (0.65 Å). Thus, Coulomb force between ions of NTa-O bonds is higher than O-Ti-O bonds. According to Hooke’s law: F=kX Where F is the Coulomb force, k is Hooke coefficient and X is displacement from the equilibrium position. The Coulomb becomes larger as the Hooke coefficient, k, increases. By applying the Schrödinger equation for the harmonic oscillator describes atomic vibrations in molecules: √

where i is frequency and i is reduced mass, one can realize that if ki increases then i increases because i changes insignificantly. Therefore, the Raman frequency of the (N, Ta) co-doped TiO2 shifted to longer wavenumber compared to the pure powders (Fig.1c). For the mono-doping of nitrogen into TiO2, N3- substituted at lattice site occupied by O2- anions, and oxygen vacancies

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Figure 1. (a) Raman spectra of the TiO2, N doped TiO2, (N, Ta) co-doped TiO2 samples. (b) Eg Raman mode of the TiO2, N doped TiO2 samples. (c) Eg Raman mode of the TiO2, (N, Ta) co-doped TiO2 samples Table 1. The position and FWHM of the Eg mode in the pure, N-doped and (N, Ta) co-doped TiO2 nanoparticles Sample TiO2 N doped TiO2 (N,Ta) co-doped TiO2

Position of Eg mode (cm-1) 145 144 147

FWHM (cm-1) 14.63 13.65 17.63

Figure 2. FE-SEM images of the TiO2 (a), N-TiO2 (b), (N, Ta)-TiO2 (c) samples [12]

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Quantity Adsorbed (cm3/g STP)

were formed [11]. For this case, oxygen vacancies are not bound to the direct vicinity of the N dopant atoms but are mobile. Thus, F decreases with both of ki and i and the Raman frequency of the Ndoped TiO2 shifted to the left compared to the pure powders (Fig.1b).Together with strain from doping N, Ta into TiO2 nanoparticles, particle size, particle size distribution are also main factors that influence the changes in the behavior of the Eg mode in our anatase TiO2 samples. The FESEM images of the synthesized nanopowders obtained from our previous work [12] were shown in Fig. 2. The results indicated that all pure, Ndoped and (N, Ta) co-doped TiO2 powders were comprised of spherical-shaped particles with 15– 25 nm diameter in average. Average nanoparticle sizes are estimated to be smaller than 20 nm for pure and (N, Ta) co-doped TiO2, and larger than 20 nm for N-doped TiO2. It is expected to have a

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TiO :(N, Ta)

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TiO :N 2

0 0

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Figure 3. The nitrogen adsorption-desorption isotherms for the pure, N-doped and (N, Ta) codoped TiO2 nanopowders

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degraded within 180 min under irradiation. The (N, Ta) co-doped TiO2 shows the highest photocatalytic activity of all compared materials. This result gave agreements with the above mentioned analysis. 100

80

Degradation (%)

larger BET surface area, which improves photocatalytic activity of materials. Figure 3 shows the nitrogen adsorption-desorption isotherms and orresponding pore size distributions for the pure, N-doped and (N, Ta) co-doped TiO2 nanopowders. The surface area of pure, N-doped and (N, Ta) co-doped TiO2 samples were estimated to be 145.5, 59.0, and 109.5 m2/g, respectively. The difference in BET surface area can be attributed to the particle size that is in agreement with the results obtained from FE-SEM observations, as mentioned above. The pore size distribution revealed that all samples have mesoporous materials (Fig. 4). These materials have a potential to become an alternative approach to the high photocatalytic activity.

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60

40

20 0.05 TiO

2

0

TiO2:N

0.04

TiO

N doped TiO

2

TiO :(N, Ta)

2

Pore volume (cm3/g.nm)

2

(N, Ta) co-doped TiO

2

Samples

Figure 5. Photocatalytic degradation of MB of the TiO2, N doped TiO2, (N, Ta) co-doped TiO2 samples in 180 min.

0.03

0.02

IV. 0.01

0 0

10

20

30

40

50

60

Pore width (nm)

Figure 4. Pore size distributions for the pure, Ndoped and (N, Ta) co-doped TiO2 nanopowders

Before photo-reaction, methylene blue was stirred with testing powders in the dark to ensure complete surface adsorption of MB on TiO2 nanoparticles. The photocatalytic activity of pure and doped TiO2 was investigated by the degradation of methylene blue solution under Mercury-Xenon irradiation with a filter (  420 nm) as shown in Fig. 5. Clearly, in the visible light photodegradation, the pure TiO2 exhibited a rather poor photocatalytic activity due to its limited photoresponding range and only 65% of the initial MB diminishes after 180 min. By incorporating N into TiO2, the photodegradation rate was increased to 50% after 180 min. Especially, the (N, Ta) codoped TiO2 nanopowders possessed the highest photocatalytic activity of all compared materials. For this sample, 93% of tested methylene blue was 357

CONCLUSION

In conclusion, we report hydrothemal synthesis of the pure, N-doped and (N, Ta) TiO2 powders. Samples were single phase anatase with average grain size in the range of d~15-25 nm. A Raman study of samples was presented in this paper. The results show that the frequency shift of the anatase Eg Raman mode is influenced by the strain from doping of N, Ta into TiO2 nanopowders and particle nanosize of samples. The (N, Ta) codoped TiO2 have high visible light photocatalytic, a lower band gap resulting from effective nitrogen, tantalum co-doping. The highest photocatalytic activity of the optimized sample N, Ta) co-doped TiO2 was due to the combined effect of electronhole separation. REFERENCES [1] Takashi H., Jun K. and Kazunari D., Recent advances in semiconductors for photocatalytic and photoelectrochemical water splitting, Chem. Soc. Rev., 2014, 43, 7520-7535 [2] Chen X., Mao S. S., Titanium Dioxide Nanomaterials:  Synthesis, Properties, Modifications, and Applications, Chem. Rev. 2007, 107, 2891-2959

The 12th Asian Conference on Chemical Sensors (ACCS2017) [3] Kamat P. V., TiO2 Nanostructures: Recent Physical Chemistry Advances, J. Phys. Chem. C 2012, 116, 11849-11851 [4] K. Obata, H. Irie, and K. Hashimoto, Enhanced photocatalytic activities of Ta, N co-doped TiO2 thin films under visible light, Chem. Phys. 2007, 339, 124 [5] J. Zhang, Y. Wu, M. Xing, S. A. K. Leghari, and S. Sajjad, Development of modified N doped TiO2 photocatalyst with metals, nonmetals and metal oxides Energy Environ. Sci. 2010, 3, 715 [6] C. W. Dunnill, Z. Ansari, A. Kafizas, S. Perni, D. J. Morgan, M. Wilson, and I. P. Parkin, Visible light photocatalysts—N-doped TiO2 by sol–gel, enhanced with surface bound silver nanoparticle islands, J. Mater. Chem. 2011, 21, 11854 [7] R. G. Chaudhuri and S. Paria, Visible light induced photocatalytic activity of sulfur doped hollow TiO 2 nanoparticles, synthesized via a novel route, Dalton Trans. 2014, 43, 5526 . [8] J. S. Zhong, Q. Y. Wang, and Y. F. Yu, Solvothermal preparation of Ag nanoparticles sensitized TiO2 nanotube arrays with enhanced photoelectrochemical performance, J. Alloys Compd. 2015, 620, 168 [9] K. Kalantari, M. Kalbasi, M., Sohrabia, S. J. Royaee, Synthesis and characterization of N-doped TiO2

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nanoparticles and their application in photocatalytic oxidation of dibenzothiophene under visible light, Ceramics International, 2016, 42, 14834-14842 [10] G. Yang, Z. Jiang, H. Shi, T. Xiao and Z. Yan, Preparation of highly visible-light active N-doped TiO2 photocatalyst, J. Mater. Chem., 2010, 20, 5301–5309 [11] A. K. Rumaiz, J. C. Woicik, E. Cockayne, H. Y. Lin, G. H. Jaffari, and S. I. Shah, Oxygen vacancies in N doped anatase TiO2: Experiment and first-principles Calculations, Appl. Phys. Lett 2009, 95, 262111 [12] N. T. H. Le, T. D. Thanh, V.-T. Pham, T. L. Phan, V. D. Lam, D. H. Manh, T. X. Anh, T. K. C. Le, N. Thammajak, L. V. Hong, and S. C. Yu, Structure and high photocatalytic activity of (N, Ta)-doped TiO2 nanoparticles, J. Appl. Phys. 2016, 120, 142110 [13] R. Long and N.J. English, Band gap engineering of (N,Ta)-codoped TiO2: A first-principles calculation, Chem.Phys.Lett. 2009, 478, 175-179. [14] K. Lee, P. Schmuki, Ta doping for an enhanced efficiency of TiO2 nanotube based dye-sensitized solar cells, Electro. Commun. 2012, 25, 11–14. [15] T. Ohsaka, F. Izumi, Y. Fujiki, Raman spectrum of anatase, TiO2, J. Raman Spectrosc. 1978, 7, 321

The 12th Asian Conference on Chemical Sensors (ACCS2017)

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Development of Polyaniline-Coated Cotton Yarn for Wearable Ammonia Gas Sensor Naraporn Indarit1, Nattasamon Petchsang2, Rawat Jaisutti1* 1

Department of Physics, Faculty of Science and Technology, Thammasat University, Pathumthani 12121, Thailand 2 Department of Materials Science, Faculty of Science, Kasetsat University, Pathumthani 10900, Thailand *Corresponding author: [email protected]

Abstract: Wearable ammonia gas sensors have been fabricated by dip coating of single cotton yarn in polyaniline solution. The surface morphology of polyaniline-coated cotton (PANi/Cotton) yarn is characterized by scanning electron microscope (SEM). The SEM images confirm the adsorption of polyaniline onto cotton surface in which the resistance is 18 k·cm-1. Gas sensing properties of PANi/Cotton yarn are investigated toward various gases including ammonia, acetone, methanol and ethanol at room temperature. The results exhibit a good response and high selectivity to ammonia gas. By varying the concentrations of ammonia gas ranging from 50 ppm to 150 ppm, PANi/Cotton yarn sensor demonstrate highly linear sensing response as a function of gas concentration with the extracted sensitivity of 0.009 ppm1 . Furthermore, the as-prepared PANi/Cotton yarn was utilized as sensing material for gas sensor operated at room temperature. As a proof-of-concept demonstration for wearable gas sensor, the sensing device-based cotton yarn was sewed on the fabric and exhibited fast change upon exposed to ammonia gas. Keywords: Polyaniline, Cotton yarn, Ammonia, Wearable gas sensor

polymers, polyaniline (PANi) is one of most interesting sensing materials, due to its easy fabrication process, environmental stability, and electrical properties can be tuned by redox process [9, 10]. Therefore in this work, a cost effective textile gas sensor based on PANi-coated cotton (PANi/Cotton) yarn have been fabricated by dip coating process and investigated its NH3 sensing behavior at room temperature.

I. INTRODUCTION Electronic textiles are great of interest in recently owing to their advantages in flexible and weaving circuits, light weight and cheap manufacturing cost [1, 2]. Electronic textiles have been widely developed for a variety of applications, not only health science and energy harvesting devices [3, 4], but also communications and information technology [5]. Textile-based gas sensor is one of a key wearable technology for environmental and military monitoring, therefore several textile sensors have been developed for low level detection of toxic gas. Ammonia (NH3) is a colorless toxic gas, which is used in a wide range of industry applications such as refrigeration, food processing and chemical processes. An exposure limit of NH3 gas that can detect by human nervous system is 5 ppm [6]. The standard value of NH3 concentration provided by OSHA (Occupational Safety and Health Administration) is 25 ppm [7]. Beyond this exposure limit and a long time inhalation of NH3 gas can cause human health problems, such as irritation to the respiratory and nervous system, eyes, skin and can also death [8]. Thus, NH3 gas sensor is necessary for warning and protecting the living beings in industries and in workspace.

II. EXPERIMENTAL PANi/Cotton yarn gas sensor was fabricated by a facile dip coating process of a single cotton yarn in polyaniline solution. In brief, the stock solution was prepared by dissolving PANi emeraldine base form in 1-methyl-2-pyrrolidinone (NMP) solution with a concentration of 2 wt.% under stirring for 72 h and at room temperature. In order to enhance the

Ammonia

PANi/cotton yarn

A

V

Gas sensors based conducting polymers are an important category of low cost devices and low temperature operation. Among various conducting

Figure 1. Schematic of electrical measurement circuit of PANi/Cotton yarn sensor.

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The 12th Asian Conference on Chemical Sensors (ACCS2017)

(a)

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into the chamber. The sensing response (S) was calculated from the response curves using the relation:

S

(b)

Rg  R0 R0

where, R0 and Rg are sensing resistance before and after exposing to target gas, respectively.

Current (A)

300

-1

R ~18 k•cm

150 0

-150

Figure 2. SEM images of (a) bare cotton and (b) PANi/Cotton yarn.

-2.5 0.0 2.5 Voltage (V)

5.0

Figure 3. I-V characteristic of PANi/Cotton yarn sensor at room temperature. The inset show optical image of PANi/Cotton yarn sensor.

1.5

(a)

Sensor response

adhesion of PANi on the cotton yarn, the ethylene glycol (EG) was dropped slowly in PANi-NMP solution with a mixing ratio of 2:1 (NMP:EG). The bare cotton yarns were carefully cleaned with acetone and dried at 60oC for 30 min. after that, the cleaned yarns were dipped in PANi stock solution for 10 min and dried at 60 oC for 2 h. Finally, the non-conducting form of PANi/cotton yarn was changed to conducting form by doping with 5 M HCl for 30 min. This step, the dark blue color of PANi/Cotton yarn has been changed to dark green color.

-300 -5.0

Gas in = 2 min Gas out = 10 min

1.0

150 ppm 125

100

0.5

75

Sensor response

The surface morphologies of bare cotton and 50 PANi/cotton yarns were characterized by scanning electron microscope (SEM, Quanta 450 FEI 0.0 0 10 20 30 40 50 60 model). The electrical property was performed by applying voltage and measuring current according Time (min) to 1 cm length of PANi/Cotton yarn using Keithley 1.5 2400 source meter as shown in Figure 1. (b) Gas sensing performance was studied using a home-made automated measurement system. The y = 0.009x - 0.266 1.0 sewed PANi/cotton yarn sensor was placed in a R2 = 0.995 stainless steel chamber with internal volume of 150 cm3. A constant voltage of 5 V was supply to two 0.5 terminals of sewed PANi/Cotton sensor and measured current response during exposing/deexposing to ammonia (NH3) gas. The low 0.0 concentration of target gas was adjusted by diluting 0 25 50 75 100 125 150 175 with nitrogen gas and passed into the test chamber. [NH3](ppm) The total flow rate was maintained at 200 sccm which was controlled using mass flow controller. Figure 4. (a) Sensor response and (b) sensitivity characteristic For the cleaning process, the residue gas inside the of PANi/Cotton yarn during exposure to NH3 gas concentrations ranging from 50 ppm to 150 ppm. test chamber was removed by feeding nitrogen gas 360

The 12th Asian Conference on Chemical Sensors (ACCS2017)

III. RESULTS AND DISCUSSION The surface morphologies of bare cotton and PANi/Cotton yarn are demonstrated in Figure 2. SEM image of bare cotton yarn show highly smooth surface, while PANi/Cotton yarn exhibit porous nanogranules of PANi on the cotton surface. The inner diameter of bare cotton and PANi/Cotton yarns are 9.36 m and 10.98 m, respectively. In order to evaluate the electrical properties of PANi/Cotton yarn devices, I-V test is employed to characterize the resistance performance. Figure 3 shows the I-V curve of PANi/Cotton yarn at apply voltage ranging from -5V to 5V. The result exhibit a linear I-V curve with almost symmetry between positive and negative biases, which imply ohmic transport. In addition, there is no hysteresis between increasing and decreasing scan voltage implied that the charge carriers are easily transport through a junction between the sensing material and electrodes, and charge transport carriers along the sensing material can be changed followed the increasing and releasing of supply voltage. Considering the PANi/Cotton length of 1 cm, the corresponding channel resistance was -1 approximately 18 k·cm . Figure 4 shows the sensor response of the PANi/Cotton yarn to various NH3 gas concentrations ranging from 50 ppm to 150 ppm and operating at room temperature. It was found that the sensor resistance increases when the PANi/Cotton yarn exposure to NH3 gas. Since NH3 gas is a reducing gas which is electron donating in nature, when it interacts with p-type semiconductor (hole majority carriers) like PANi via amine groups resulting in decreasing the conductivity of PANi backbone and film resistance gradually increases. As shown the results in Figure 4, it can be seen that the response of PANi/Cotton yarn sensor increases with increase in NH3 gas concentrations. By increasing the gas concentration from 50 ppm to 150 ppm, the sensing response increases from 0.2 to 0.4, 0.7, 0.9 and 1.1, respectively. At low gas concentration means a low surface coverage area of gas molecules owing to lower surface interaction between PANi and gas molecules compared to high gas concentrations. The PANi/Cotton yarn sensor exhibit linear sensor response as a function of gas concentrations which show the extracted value of R2 is ~0.995, as shown in Figure 4(b). The sensor sensitivity obtained from the slope of sensor response and gas

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Sensor response

0.25 0.20

50 ppm

0.15 0.10 0.05 0.00

l l r nia tone ano ano ate o h h w e m c t Et Am A Me

Figure 5. Selectivity of PANi/Cotton yarn sensor at 50 ppm of various gases operating at room temperature.

concentration curve is 0.009 ppm-1. Furthermore, the detection limit of the PANi/Cotton sensor is found to be 29.6 ppm. An important parameter of gas sensors is selectivity which represents the ability of sensor toward a certain gas in presence of other gases. To determine the selectivity, the sensing response of PANi/Cotton yarn to various gases including NH3, acetone, methanol, ethanol and water were investigated at fixed gas concentration of 50 ppm and the corresponding responses are shown in Figure 5. The PANi/Cotton sensor demonstrated the highest response to NH3 gas, whereas it exhibits comparatively low response towards other gases. As can be seen in Figure 4, the sensing response to NH3 gas has high selective coefficient (QNH3, Q NH3 = SNH3/Sx where SNH3 and Sx are the sensor response of sensor to NH3 and other gases, respectively) ~10 times compared to other gases. Higher value of QNH3 imply that the sensor has a better ability to distinguish NH3 gas in the mixture gases environment.

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IV. CONCLUSION Wearable gas sensor based on cotton yarn was developed by dip-coating of PANi onto single cotton yarn surface. The SEM images confirm that nanogranules of PANi coated on the surface of smooth cotton yarn. The electrical properties of PANi/Cotton yarn show linear I-V curve which the extracted resistance is ~18 k·cm-1. The sensing properties of the PANi/Cotton sensor were investigated toward various gases including NH3, acetone methanol, ethanol, and water. It was found that the PANi/Cotton has highly selectivity to NH3

The 12th Asian Conference on Chemical Sensors (ACCS2017)

gas comparatively to other gases at room temperature operating. In addition, it exhibit linear sensing response to NH3 gas ranging from 50 ppm to 150 ppm in which the extracted sensitivity is ~0.009 ppm-1. The results showed that the wearable gas sensor based on PANi/Cotton yarn is ability to monitor and discriminate NH3 gas in mixtures gases.

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ACKNOWLEDGMENT This work was supported by Thammasat University (Contract No. 17/2559, 16/2560), the financial support provided by Thammasat University Research Fund under the TU Innovative Scholar (Contract No. สป 11/2559), and by Faculty of Science and Technology (Contract No. สป 2/2559).

nanogenerator for mechanical energy harvesting," Energy & Environmental Science, vol. 6, pp. 26312638, 2013. [5] R. Salvado, C. Loss, R. Gonçalves, and P. Pinho, "Textile Materials for the Design of Wearable Antennas: A Survey," Sensors, vol. 12, p. 15841, 2012. [6] M. J. Fedoruk, R. Bronstein, and B. D. Kerger, "Ammonia exposure and hazard assessment for selected household cleaning product uses," J Expo Anal Environ Epidemiol, vol. 15, pp. 534-544, 2005. [7] F. Achouri, S. Corbel, L. Balan, K. Mozet, E. Girot, G. Medjahdi, et al., "Porous Mn-doped ZnO nanoparticles for enhanced solar and visible light photocatalysis," Materials & Design, vol. 101, pp. 309-316, 2016. [8] A. Mirzaei, S. G. Leonardi, and G. Neri, "Detection of hazardous volatile organic compounds (VOCs) by metal oxide nanostructuresbased gas sensors: A review," Ceramics International, vol. 42, pp. 15119-15141, 2016. [9] S. Abdulla, T. L. Mathew, and B. Pullithadathil, "Highly sensitive, room temperature gas sensor based on polyaniline-multiwalled carbon nanotubes (PANI/MWCNTs) nanocomposite for trace-level ammonia detection," Sensors and Actuators B: Chemical, vol. 221, pp. 1523-1534, 2015. [10] K. Ramanathan, M. A. Bangar, M. Yun, W. Chen, A. Mulchandani, and N. V. Myung, "Individually Addressable Conducting Polymer Nanowires Array," Nano Letters, vol. 4, pp. 12371239, 2004.

REFERENCES [1] Y. J. Yun, W. G. Hong, D. Y. Kim, H. J. Kim, Y. Jun, and H.-K. Lee, "E-textile gas sensors composed of molybdenum disulfide and reduced graphene oxide for high response and reliability," Sensors and Actuators B: Chemical, vol. 248, pp. 829-835, 2017. [2] Y. Huang, H. Hu, Y. Huang, M. Zhu, W. Meng, C. Liu, et al., "From Industrially Weavable and Knittable Highly Conductive Yarns to Large Wearable Energy Storage Textiles," ACS Nano, vol. 9, pp. 4766-4775, 2015/05/26 2015. [3] C. Pang, G.-Y. Lee, T.-i. Kim, S. M. Kim, H. N. Kim, S.-H. Ahn, et al., "A flexible and highly sensitive strain-gauge sensor using reversible interlocking of nanofibres," Nat Mater, vol. 11, pp. 795-801, 2012. [4] W. Zeng, X.-M. Tao, S. Chen, S. Shang, H. L. W. Chan, and S. H. Choy, "Highly durable all-fiber

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