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)
pwater19 & Bertie data (thickness = 500 nm, volume = 2000 nL)
1.2
Bertie
Us
1
0.8
Absorbance
Peaks related
to vibrational
modes
0.6
0.4
0.2
0
-0.2
0
500
1000
1500
2000
2500
3000
3500
4000
-1
Wavenumber (cm )
http://www.lsbu.ac.uk/water/vibrat.html#d
4500
Results (XAS)
Sample water000043, thickness = 25 nm (from CXRO - LBNL)
1.01
1
Transmission
0.99
0.98
0.97
0.96
0.95
0.94
0.93
510
520
530
540
550
Energy (eV)
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