"Galileo Galilei" Seminar (April 27th 2005)
"Solvation Dynamics in Confined and Interfacial Water"

Prof. Branka M. Ladanyi,
Department of Chemistry, Colorado State University
Fort Collins, U.S.A.

Department of Mathematics "L. Tonelli",
Aula Magna (ground level) - at 15:00

Solvation dynamics corresponds to the rate of solvent reorganization in response to a sudden change in solute-solvent interactions. It is usually measured by monitoring the time evolution of the Stokes shift in the fluorescence spectrum of a dissolved chromophore. In bulk liquids, solvation dynamics occurs primarily through reorientation of the surrounding solvent molecules. In heterogeneous environments, other solvation mechanisms, associated with changes in the location of the solute relative to the interface, are possible and can play an important role. In this talk, I will describe the results of our molecular dynamics (MD) computer simulation studies of solvation dynamics in two different heterogeneous systems: the aqueous phase of reverse micelles and the water-zirconia interface. In reverse micelles, interactions between the surfactant head groups and the chromophore determine its location relative to the interface. MD results that illustrate the effects of electrostatic repulsion or attraction between model chromophores and surfactant headgroups on solvation dynamics will be presented and discussed. In its ground electronic state, the chromophore coumarin 343 (C343) is adsorbed on the surface of zirconia nanoparticles in aqueous solution. In its electronically excited state, C343 becomes more attractive to water, which leads to its partial desorption. I will present our results for the contributions of this process to solvation dynamics.