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Size-controlled gold nanoparticles, ranging from 2 to 15 nm in diameter, were first prepared from gold substrates in 0.1 N HCl aqueous solutions without the addition of any stabilizers by sonoelectrochemical methods. First, an Au substrate was cycled in a deoxygenated aqueous solution containing 0.1 N HCl from −0.28 to +1.22 V vs Ag/AgCl at 500 mV/s with 100 scans. The durations at the cathodic and anodic vertexes are 10 and 5 s, respectively. After this process, Au- and Cl-containing complexes were left in the solution. The Au working electrode was then immediately replaced by a Pt electrode, and cathodic overpotentials of 0.2, 0.4, and 0.6 V from the open circuit potential (OCP) of ca. 0.82 V vs Ag/AgCl were applied under sonification to synthesize Au nanoparticles. The prepared nanoparticles increase in size from 2 to 15 nm with the increase of the cathodic overpotential applied from 0.2 to 0.6 V. Furthermore, the ratio of Au nanoparticles to Au-containing nanocomplexes in solutions can be controlled by adjusting the sonoelectrochemical reduction time.

In this work, the characteristics of polypyrrole (PPy) films electrodeposited onto an electrochemically roughened gold substrate with bimetallic silver and gold nanoparticles were first investigated. First, a silver substrate was roughened by a triangular‐wave oxidation–reduction cycle (ORC) in an aqueous solution containing 0.1 M HCl. Subsequently, a gold substrate was roughened by a similar ORC treatment in this used solution. The results revealed that the surface of the roughened gold substrate demonstrated two different kinds of deposition domains because of the modification of silver nanoparticles. Encouragingly, some novel characteristics of PPy deposited onto this substrate were observed, in comparison with those on the roughened gold substrate without the modification of silver nanoparticles. They included a denser and more compact surface morphology, higher oxidation degree, increased conductivity, and improved surface‐enhanced Raman scattering. Furthermore, the nucleation and growth mechanism for PPy electropolymerization on this silver‐modified roughened gold substrate was distinguishable from that on the unmodified one. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2724–2731, 2006

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