Characterization of Colloidal Metal Films for Use in Surface Enhanced Raman (SERS) Studies of Surface Mediated Photolysis

Substrates for surface-enhanced Raman (SERS) studies of surface-mediated photochemical reactions were prepared. Gold and silver colloidal metal films (CMFs) were formed when colloidal particles were covalently bound to a substrate through alkoxysilanes (specifically 3-aminopropylmethoxysilane or 3-mercaptopropylalkoxysilane) with functional groups that have high affinities for binding noble metals. A set of 47 unique CMFs with systematically varying optical (and therefore electromagnetic) properties were prepared by adjusting the starting materials (colloidal particle size and alkoxysilane). The surfaces were characterized optically through their visible extinction spectra. It was shown that gold colloids had an extinction maximum in the red region of the visible spectra, while silver colloids exhibited an extinction maximum in the blue region. It was also shown that the extinction spectra of the colloids changed very little when bound to the surface. The use of BPE (trans-1,2-bis(4-pyridyl)ethylene) during slide derivatization caused a narrow extinction peak, while the use of PVP (polyvinylpyrrolidone) caused the spectra to be moderately narrow. Preliminary SERS studies were conducted using pyridine in the colloidal solutions. The observed enhancement was on the order of 103. Preliminary SERS tests using the CMFs were inconclusive. The set of CMFs will be used in future studies of the effects of local electric fields on the surface-mediated photolysis of p-nitrobenzoic acid