Improved surface-enhanced Raman scattering of polypyrrole electrodeposited on roughened substrates composed of Au-Ag bimetallic nanoparticles

We report here the first electrochemical method to prepare a roughened gold substrate with bimetallic silver and gold nanoparticles. First, a silver substrate was roughened by a triangular-wave oxidation-reduction cycle in 0.1 N HCl aqueous solutions. Silver-containing complexes were found in the solution after the ORC treatment. Then a gold substrate was subsequently roughened by a similar oxidation-reduction treatment in this solution. Scanning electron microscopy and atomic force microscopy reveal that the surface of the roughened gold was intrinsically modified with silver nanoparticles, which demonstrates two different kinds of deposition domains. Encouragingly, surface-enhanced Raman scattering of polypyrrole electrodeposited on the roughened gold substrate, modified with finer silver nanoparticles, exhibits an eightfold higher intensity.