"AOT has sulfonate head groups with sodium counterions that form the interface with the reverse micelle's water nanopool. The extent of excited-state deprotonation is observed by steady-state fluorescence measurements. Proton-transfer kinetics and orientational relaxation are measured by time-dependent fluorescence using time-correlated single photon counting. The time dependence of deprotonation is related to diffusive proton transport away from the photoacid. The fluorescence reflecting the long time scale proton transport has an approximately t-0.8 power law decay in contrast to bulk water, which has a t-3/2 power law. For a given hydration level of Nafion, the excited-state proton transfer and the orientational relaxation are similar to those observed for a related size AOT water nanopool," wrote D.B. Spry and colleagues, Stanford University, Department of Chemistry.

The researchers concluded: "The effective size of the Nafion water channels at various hydration levels are estimated by the known size of the AOT reverse micelles that display the corresponding proton-transfer kinetics and orientational relaxation."

Spry and colleagues published their study in the Journal of the American Chemical Society (Proton transport and the water environment in nafion fuel cell membranes and AOT reverse micelles. Journal of the American Chemical Society, 2007;129(26):8122-30).

For additional information, contact D.B. Spry, Stanford University, Dept. of Chemistry, Stanford, CA 94305 USA..

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