Research Interests

In my research I apply lasers to the study of equilibrium and dynamic properties of molecules at liquid and solid interfaces. To probe the very thin region that constitutes an interface we use the interface selective techniques of second harmonic and sum frequency generation. My laboratory has succeeded in developing new methods to develop the absolute orientation of molecules at liquid interfaces to obtain the energetics of adsorption of neutral and charged molecules to the interface to study chemical equilibria and pH at interfaces that we find are markedly different from their bulk values, and to develop a polarity scale for liquid interfaces. Using second harmonic as the probe method has enabled us to observe dynamics at interfaces of excited state cis-trans isomerization, intermolecular energy transfer, solvation dynamics, and rotational molecular motions, which generally differ significantly from their bulk counterparts. We have recently shown that second harmonic spectroscopy can be used to selectively probe the surfaces of centrosymmetric microscopic particles of submicron to micron diameters. Among the surfaces of microscopic particles studied so far are polymer beads in aqueous solution, oil droplet/aqueous emulsions, semiconductor colloids, naturally occurring clay particles, and phospholipid liposomes.

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Section 14: Chemistry