Sonoelectrochemical synthesis of spike-like gold–silver alloy nanoparticles from bulk substrates and the application on surface-enhanced Raman scattering

The synthesis of non-spherical spike-like gold–silver alloy nanoparticles on platinum substrates was first developed by sonoelectrochemical methods in this study. First, a silver substrate was roughened by a triangular-wave oxidation–reduction cycle (ORC) in an aqueous solution containing 0.1 M HCl. Silver-containing complexes were found in the solution after the ORC treatment. Then a gold substrate was subsequently roughened by the similar ORC treatment in the same silver complexes-containing solution. After this procedure, Au- and Ag-containing complexes were left in the solution. Subsequently, the Au working electrode was immediately replaced by a Pt electrode. A cathodic overpotential was applied under controlled sonication and slight stirring to synthesize Au–Ag alloy nanoparticles on the Pt substrate. Encouragingly, the surface-enhanced Raman scattering (SERS) of Rhodamine 6G on the Au–Ag alloy nanoparticles-deposited Pt substrate exhibits a higher intensity by eight-fold of magnitude and a better resolution, as compared to that obtained on the Au nanoparticles-deposited Pt substrate.