Chemical origins of surface-enhanced Raman scattering by cyanide on copper electrodes

Abstract

A simple potential-step oxidation–reduction cycle pretreatment is reported for the surface-enhanced Raman scattering (SERS) system Cu/0.1 mol dm^–3 Na₂SO₄, 0.01 mol dm^–3 KCN. Laser-assisted corrosion and dissolution processes are suggested by a combination of uniform-laser-flux perturbations of the cyclic voltammetry and laser-interruption effects in the intensity against time decay curve for the system at –1.25 V (vs SCE). The pH dependence of v(CN) intensities for both the copper/cyanide SERS surface and for related cyanocopper(I) complexes is attributed partly to the decomposition of such complexes (pH ⩽ 4.6) and partly to the decomposition of associated copper oxides (pH > 2). The identification of cyanocopper(I) complexes stabilized by copper(I) oxide as the intensely-scattering phase compares with the oxide–cyanide phase proposed for silver/cyanide SERS. The copper/cyanide SERS system is classified as type III (inorganic microzone).