SURFACE ENHANCED RAMAN-SCATTERING AT ELECTRODES - A STATUS-REPORT

Progress during the first decade of surface enhanced Raman scattering (SERS) is briefly reviewed. Examples of SERS of adsorbed H//2O, OH**+31,and H//3O** plus on Ag electrodes which have undergone an oxidation-reduction cycle (ORC) are discussed in some detail in order to bring out the unique and general features of SERS in an electrochemical system. Experimental techniques to further enhance the SERS signal, as well as to decrease the SERS signal after an ORC, are reviewed as such results can provide clues to possible surface enhancment mechanisms. The two enhancement mechanisms (electromagnetic and charge transfer) are presented in a unified but simplistic picture which involves the nearly free s,p-electron band and the more localized d-electron band for the noble metals (Ag, Cu, and Au).