pH-Dependent Surface-Enhanced Raman Scattering of 8-Hydroxy Quinoline Adsorbed on Silver Hydrosol

Surface-enhanced Raman scattering (SERS) of 8-hydroxy quinoline (HQ) adsorbed on silver hydrosols are compared with the FTIR and normal Raman spectrum in the bulk and in solution. Definite evidence of the charge transfer interaction to the overall contribution in the SER enhancement has been reported. The excitation profile study also supports the evidence of a charge transfer interaction. The effect of pH variation on the SER band intensity is explained in terms of chemisorption of the molecule on bare and chlorinated silver surfaces. The apparent enhancement factor calculations of the principal Raman bands indicate that in the surface-adsorbed state, an HQ molecule is oriented neither flat nor vertical to the silver surface but is tilted. Copyright 2000 Academic Press.