Development%20of%20Nanofluidic%20Cells%20for%20Ultrafast%20X%20rays%20Studies%20of%20Water

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Development of Nanofluidic Cells for Ultrafast X
rays Studies of Water

• Melvin E. Irizarry-Gelpí
• Aaron Lindenberg

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Brief Outline

• Background
• Water and its structure
• Experiments
• Confined liquids
• Nanofluidic cells
• The apparatus
• Sample Characterization
• Results

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Water
Liquid water
Ice structure

• 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?

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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 (lt500 nm thickness) are required

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Previous Methods
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Nanofluidic Cells

• Two Si3N4 1 mm x 1 mm and 0.5 mm x 0.5 mm windows
• Thickness lt 500 nm
• Photoresist spacer and Polystyrene nanospheres
  with different diameters (200 nm and 500 nm)

http//www.silson.com/pics/standard10.jpg
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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

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Sample holder
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Sample characterization
FTIR at SU
XAS at beamline 6.3.2 ALS - LBNL
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Results (FTIR)
Peaks related to vibrational modes
http//www.lsbu.ac.uk/water/vibrat.htmld
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Results (XAS)
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Thickness (FTIR)
Plain water Polystyrene spheres
1000 nm 1010 nm
450 nm 520 nm
220 nm 1750 nm
145 nm 1500 nm
150 nm 500 nm
1800 nm
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Thickness (XAS)
Plain water Polystyrene spheres
15 nm 1 nm
5 nm 10 nm
15 nm 17 nm
25 nm
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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

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Confined Liquids
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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

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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

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Thank you for your attention

• Questions

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References

• 1 L. Naslund, Probing unoccupied electronic
  states in aqueous solutions, Ph.D. dissertation,
  Stockholm University, Stockholm, 2004. Online.
  Available http//urn.kb.se/resolve?urnurnnbnse
  sudiva-294
• 2 J. E. Bertie and Z. Lan, Applied
  Spectroscopy, vol. 50,no. 8, pp. 10471057, 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.
  Naslund, 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. 995999, 2004.
  Online. Available http//www.sciencemag.org/cgi
  /content/abstract/304/5673/995