Simple Technique for Measuring Surface-Enhanced Fourier Transform Raman Spectra of Organic Compounds

Abstract

A silver surface, suitable for Fourier transform surface-enhanced Raman scattering (FT-SERS), has been prepared by subjecting a polished silver surface to an oxidation-reduction cycle in an electrochemical cell with KCl solution as the electrolyte. The surface produced by this method is shown, by scanning electron microscopy, to be very rough. The preparation of this surface is quite reproducible because the significant parameters of starting surface, electrolyte concentration, and potential can all be well controlled. After removal from the cell followed by washing and drying, organic compounds can be placed on the surface as solutions in aqueous or organic solvents, or by exposure of the surface to vapor. Typically, good FT-SERS spectra are obtained from 0.1–2 μg of sample, after evaporation of the solvent. These experiments were not optimized for minimum detection limits. The technique is very simple, and spectra can be obtained with ease for a wide variety of compounds. Most compounds gave FT-SERS spectra which were similar to their solid Raman spectra; however compounds containing groups expected to interact strongly with the silver surface gave FT-SERS spectra very different from their normal Raman spectra.