VIBRATIONAL SPECTROSCOPY (SERS AND SERRS)

Surface-enhanced Raman scattering (SERS) and surface-enhanced resonant Raman scattering (SERRS) are two analytical techniques that can be applied to the study of adsorbed molecules on a number of rough metal surfaces. A current problem in experimental vibrational spectroscopy is the characterization of molecular monolayers adsorbed on metal surfaces, in particular, Langmuir-Blodgett (LB) monomolecular layers deposited onto solid substrates. SERS and SERRS have been shown to be useful in the study of sequential LB monomolecular layers, diffusion through LB layers and selective adsorption phenomena. However, the problem of molecular orientation in monolayers has been arduous due to the depolarization effect of rough metal surfaces, and to the corresponding difficulty in the interpretation of polarized data. The natural complement to SERS is the infrared spectroscopy on smooth metal surfaces such as reflection-absorption infrared spectroscopy (RAIRS). Vibrational analysis using both techniques are illustrated here. The problem of order disorder in monolayers and the temperature dependence of the SERS signal are also discussed.