Optimally electrochemically roughened silver substrates prepared in gold complexes-containing solutions for trace molecules detection

We report here the first optimally electrochemical method to prepare surface-enhanced Raman scattering (SERS)-active roughened silver substrates with bimetallic silver and gold nanoparticles. First, a gold substrate was roughened by a triangular-wave oxidation-reduction cycle (ORC) in an aqueous solution containing 0.1 mol/L KCl. Gold-containing complexes were found in the solution after the ORC treatment. Then a silver substrate was subsequently roughened by the similar ORC treatment using different parameters in the same solution. The SERS of R6G adsorbed on the optimal procedure-prepared substrate exhibits a higher intensity by one order of magnitude, as compared with that of R6G adsorbed on a normal method-prepared substrate. Moreover, the practical limit of detection (LOD) of R6G can be reduced by 5 orders of magnitude from 2 × 10^-10 to 2 × 10^-15 M. Further investigations indicate that surface morphologies of roughened Ag substrates and the oxidization states of Ag and the contents of Cl on the roughened Ag substrates are responsible for these improved SERS effects.