We report here the first electrochemical polymerization of polypyrrole (PPy) on Au substrates in aqueous solutions containing additives of prepared Au nanoparticles with a diameter of ca. 2 nm. Encouragingly, the synthesized PPy films demonstrate novel characteristics due to the effects of Au nanoparticles, which provide a catalytic electroxidation pathway. The prepared PPy shows a stereomorphology, which is distinguishable from the typically granular raspberry morphology of pure PPy, and a rougher surface. The conductivity of PPy is significantly increased (similar to 10 times), which also reflects on the extremely high oxidation level of 0.36 revealed from the analysis of X-ray photoelectron spectroscopy (XPS). The mechanism of the nucleation and growth, and the X-ray diffraction (XRD) pattern were investigated to explain the specific characteristics of PPY films. (c) 2006 Elsevier Ltd. All rights reserved.