Solvent Effects on the Dynamic Polarizability and Raman Response of Molecule-Metal Oxide Hybrid Clusters.

Currently, there is considerable interest in the properties of semiconducting metal oxide nanoparticle substrates because of their utility in surface-enhanced Raman scattering, dye-sensitized solar cells, and photocatalysis. While the enhancement of Raman activities of molecules adsorbed on these nanoparticles is due to a large increase in the polarizability, because of charge transfer from the molecule to the semiconducting nanoparticle, little is known about the factors responsible for modulating the polarizability, particularly the influence of the solvent. Consequently, we have carried out Monte Carlo simulations of several hybrids to study the solvent effect on the dynamic polarizabilities and electronic spectra. Our results indicate that the presence of the solvent induces a shift and an increase in the polarization response that is dependent on the identity of the hybrid. The observed enhancement can be attributed to both the resonant character of the excitation and the participation of the solvent in the charge redistribution. The methodology employed in this work could be very valuable in both identifying and developing metal oxides as novel molecular sensors.