Surface enhanced Raman scattering and second-harmonic generation from CN - complexes and SO 2-4 on Ag electrodes during oxidation-reduction cycles

Abstract

Abstract The temporal evolution of the surface enhanced Raman scattering (SERS) from SO 2− 4 and CN − complexes adsorbed on a Ag electrode immersed in 0.1M K 2 SO 4 +0.01M KCN electrolytes during an electrochemical oxidation-reduction cycle (ORC) has been investigated. The appearance and the disappearance of the high frequency stretching modes of SO 2− 4 and CN − complexes, as well as the low frequency stretching and bending modes of AgSO 4 and AgCN are correlated with cyclic voltammograms recorded during an ORC. Similar correlations were made between the cyclic voltammogram and the increase and decrease of the surface enhanced diffused second-harmonic generation (SHG) from the electrochemically roughened Ag surface itself, from the adherent layer of Ag 2 SO 4 and AgCN, and from the CN − complexes adsorbed on the Ag electrode surface. Diffused SHG from Ag electrodes was investigated in the following electrolytes: (1) 0.1M K 2 SO 4 , (2) 0.1M K 2 SO 4 + 0.01M KCN, (3) 0.1M K 2 SO 4 + 0.01M NaOH and (4) 0.1M K 2 SO 4 + 0.01 M NaOH + 0.01 M KCN. The latter two electrolytes were selected to illustrate the importance of Ag 2 O in decreasing the diffused SHG signal when the Ag electrode, immersed in an electrolyte of pH > 7, is cycled through a specific potential region that involves the formation of Ag 2 O. Differences between the potential dependent evolution of the SERS and SHG signals are postulated.