Surface enhanced Raman scattering from silver electrodes

Abstract

<p>The chemical and physical origins of the anomalously large enhancement of the Raman scattering cross section for molecules adsorbed on silver electrodes in an electrochemical cell were investigated. The effect of the chemical reactions which occur during the anodization/activation procedure were studied using the Ag-CN system. It was shown that the function of the anodization process is to roughen the electrode surface and create an activated site for bonding to the cyanide. A new nonelectrochemical technique for activating the silver surface, along with a study of the enhanced cyanide Raman scattering in different background electrolytes, showed that the Raman active entity on the surface must be a silver-cyanide complex;In order to study the physical mechanism of the enhancement,^the angular dependence of the scattered radiation was measured^from pyridine adsorbed on an evaporated silver electrode. Both^polycrystalline and single crystalline silver films were used. The^angular dependence of the scattered radiation from these films^showed that the metal surface was controlling the directional^properties of the scattered radiation, and not the polarizability^tensor of the adsorbate. Based on these experimental results, it^was concluded that for weakly roughened silver electrodes the^source of the anomalous enhancement is due to a resonant Raman;scattering process;('(DAG))USDOE Report IS-T-985. This work was performed under Contract W-7405-eng-82 with the U.S. Department of Energy.</p>