Charge-transfer contribution to surface-enhanced Raman scattering and surface-enhanced resonance Raman scattering of dyes at silver and gold electrodes

The charge transfer (CT) contribution to surface-enhanced Raman scattering (SERS) and surface-enhanced resonance Raman scattering (SERRS) was compared for several dyes adsorbed at silver and gold electrodes. It was found that the CT effect is more pronounced for dyes that in solution are not in resonance with the incident light (SERS spectra). For SERRS spectra the CT contribution seems to be negligible or considerably smaller in comparison with SERS. This means that the potential changes of the SERRS intensity reproduce the changes in surface concentration more adequately than SERS.