"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.