Dynamics of nanoscopic water

PHYS 722

Michael D. Fayer, fayer@stanford.edu1, David E. Moilanen, moilanen@stanford.edu2, Emily Fenn, eefenn@stanford.edu2, David Ben Spry1, Alexei Goun, agoun@stanford.edu2, and Nancy E. Levinger, levinger@lamar.colostate.edu3. (1) Department of Chemistry, Stanford University, Stanford, CA 94305, (2) Chemistry, Stanford University, Stanford, CA 94305, (3) Department of Chemistry, Colorado State University, Fort Collins, CO 80523
The dynamics of water in nanoscopic environments are directly studied by probing water hydroxyl stretching mode using ultrafast infrared measurements of vibrational lifetimes, orientational relaxation, (pump-probe experiments) and spectral diffusion (vibrational echo experiments). Studies of AOT reverse micelles show a dramatic slowing of hydrogen bond network rearrangements as the size of the water nanopool is decreased below ~5 nm. A comparison between AOT (ionic head group) and a reverse micelle with a non-ionic head group demonstrates nanoscopic water dynamics are due to confinement rather than simply an ionic interface effect. Nanoscopic water is also studied in channels of Nafion fuel cell membranes using IR methods. Water dynamics are very different from those of bulk water and change with the degree of membrane hydration. Proton transfer dynamics inside Nafion channels are studied by experiments on a photoacid incorporated in the membrane, and the results care compared to experiments in AOT.
 

Hydration: From Clusters to Aqueous Solution
1:20 PM-5:00 PM, Thursday, August 23, 2007 BCEC -- 159, Oral

Division of Physical Chemistry

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007