Surface-enhanced Raman spectroscopy of metal-halide vibrations on Ag and Cu electrodes

Abstract

Halide ions play an important role in the surface-enhanced Raman (SER) process in electrochemical environments. They are usually specifically adsorbed at Ag and Cu electrodes in the same potential range used in the SER experiments. This intimate contact with the metal surface is not sufficient to obtain an enhancement even when a rough metal is immersed in the electrolyte. After an oxidation-reduction cycle (ORC) is performed, however, an enormous enhancement appears when highly concentrated electrolytes are used. The Raman intensities observed for M-X vibrations are comparable to those found for the ring modes of pyridine. The irreversible potential dependence of the enhancement (vanishing with sufficiently negative potential) indicates that particular silver (copper) halide structures are responsible for these effects. It is argued that these structures are different from simple specifically adsorbed halide ions. © 1981 American Chemical Society.