A silver solution for surface-enhanced Raman scattering

A silver solution has been prepared from the reduction of silver nitrate (AgNO3) by hydrogen peroxide (H2O2) under basic conditions for surface-enhanced Raman scattering (SERS). Reaction conditions such as temperature, time, absence of oxygen, pH of the reaction mixture, and reagent purity have been found to be important factors contributing to the reaction process and the SERS performance of the substrate product. These factors have been evaluated and optimized. It was found that the T = 0 degrees C, long reaction period, nitrogen or inert gas purging, and alkaline conditions are essential for preparing the SERS-active silver solution. The purity of reagents is as important as other factors. One major advantage of this reduction process for producing the substrate for SERS is the reduction or elimination of spectral interference caused by the reaction by-products. Two series of experiments have been conducted to test the shelf life and the aging effect of the substrate on the SERS intensity. Some SERS activities of the silver solution substrate have been compared with those of other sols. An excitation profile as well as the dependence of SERS data on UV illumination, oxidizing agent and reducing agent have been collected and discussed in terms of SERS phenomena. (C) 1999 Elsevier Science B.V. All rights reserved.