Surface-enhanced Raman scattering from polystyrene on gold clusters

Surface-enhanced Raman scattering (SERS) constitutes a spectroscopic method of rapidly growing importance, and polystyrene is a widely used compound of great industrial importance. In this work, SERS data were obtained from polystyrene samples prepared by vapor deposition of gold and plasma-induced polymerization of styrene gas. A thorough examination of this data is presented. The relationships between sample preparation parameters, gold-cluster morphology, and SERS intensity were elucidated. Using Wilson's notation, vibrations were assigned to all bands between 250 and 1750 cm in the ordinary Raman and SERS spectra of polystyrene. The correct assignment of these bands would be a significant achievement because they have been controversial in the literature for ~30 years. Our assignments were made by reviewing the literature and comparing the assignments found there to spectral data acquired during this study; they were confirmed using density functional theory (DFT) calculations performed on the styrene monomer. The orientation of polystyrene's phenyl ring, relative to the gold surface, was determined. It has been suggested that reactions involving silver catalyze polystyrene degradation during SERS, but we found that silver is not necessary for the degradation to occur.