Development of Nanofluidic Cells for Ultrafast X rays Studies of Water Melvin E. Irizarry-Gelpí Aaron Lindenberg
Brief Outline Background
Water and its structure Experiments Confined liquids
Nanofluidic cells The apparatus Sample Characterization Results
Water
Ice structure
Liquid water
•Liquid water exhibits structural rearrangements on picosecond and femtosecond time-scales •How does the structure and dynamics of liquids confined to nanoscopic length-scales differ from the bulk?
Femtosecond x-ray absorption spectroscopy
Use femtosecond laser to drive hydrogen bond network
Ultrafast soft x-ray pulses provide the necessary resolution to probe bonding dynamics
In order to perform measurements, nanofluidic cells (<500 nm thickness) are required
Previous Methods
Nanofluidic Cells
Two Si3N4 1 mm x 1 mm and 0.5 mm x 0.5 mm windows Thickness < 500 nm Photoresist spacer and Polystyrene nanospheres with different diameters (200 nm and 500 nm)
window water layer
spacer
window
http://www.silson.com/pics/standard10.jpg
The SIMPLEtron
Simple and reproducible way to make cells Micrometer stages allow for accurate position of sample cells and application of nanoliter quantities of water Sample preparation takes minutes
Sample holder
Sample characterization
FTIR at SU XAS at beamline 6.3.2 ALS - LBNL
Results (FTIR) p w a te r1 9 & B e rtie d a ta (thic kness = 5 0 0 nm , vo lum e = 2 00 0 nL) 1 .2 B e rtie Us 1
0 .8
A b s orb a nc e
Peaks related to vibrational modes
0 .6
0 .4
0 .2
0
-0 .2
0
500
1000
1500
2000
2500
3000
3500
4000
W a ve num b e r (c m -1 )
http://www.lsbu.ac.uk/water/vibrat.html#d
4500
Results (XAS) S a m p le w a te r0 0 0 0 4 3 , thick ne ss = 2 5 nm (fro m C X R O - L B N L ) 1 .0 1
1
0 .9 9
T ra n s m issio n
0 .9 8
0 .9 7
0 .9 6
0 .9 5
0 .9 4
0 .9 3 510
520
530
540
550
E ne rg y (e V )
560
570
580
Thickness (FTIR) Plain water 1000 nm 450 nm 220 nm 145 nm 150 nm
Polystyrene spheres 1010 nm 520 nm 1750 nm 1500 nm 500 nm 1800 nm
Thickness (XAS) Plain water 15 nm 5 nm 15 nm
Polystyrene spheres 1 nm 10 nm 17 nm 25 nm
Preliminary observation of confinement effects
Observe shift in main absorption peak to lower energy as sample thickness decreases Indication of change in structure (to a more ice-like configuration) for ultrathin samples
Confined Liquids
Conclusions
A simple and reliable means of producing nanofluidic water cells has been developed A range of thickness may be produced, although random Evidence for changes in the x-ray absorption spectrum for ultrathin samples is observed Future experiments will couple a femtosecond laser into the sample to probe the structural dynamics of water on ultrafast time-scales
Acknowledgements U. S. Department of Energy, Office of
Science, SULI Program SLAC and Stanford University Advance Light Source at Lawrence Berkeley National Laboratory Special thanks to Aaron Lindenberg
Thank you for your attention Questions
References [1] L. N¨aslund, “Probing unoccupied electronic states in aqueous solutions,” Ph.D. dissertation, Stockholm University, Stockholm, 2004. [Online]. Available: http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-294 [2] J. E. Bertie and Z. Lan, Applied Spectroscopy, vol. 50,no. 8, pp. 1047–1057, 1996. [3] Henke, B. L.; Gullikson, E. M.; Davis, J. C. At. Data Nucl. Data Tables 1993, 54, 181. See also www-cxro.lbl.gov/optical_constants/ [4] P. Wernet, D. Nordlund, U. Bergmann, M. Cavalleri, M. Odelius, H. Ogasawara,L. A. N¨aslund, T. K. Hirsch, L. Ojamae, P. Glatzel, L. G. M. Pettersson,and A. Nilsson, “The structure of the first coordination shell in liquid water,” Science, vol. 304, no. 5673, pp. 995–999, 2004. [Online]. Available: http://www.sciencemag.org/cgi/content/abstract/304/5673/995
