Polyaniline colloidal particles were enzymatically synthesized ill aqueous media using poly(vinyl alcohol) as steric stabilizer. Hydrochloric acid, toluenesulfonic acid, and camphorsulfonic acid were used as doping agents during polymerization. Polyaniline showed chemical redox reversibility as demonstrated by changes in its electronic absorption spectra. Fourier transform infrared and UV-visible spectroscopic studies indicate a linear chemical structure of the synthesized polymer, whereas the results from X-ray photoelectron spectroscopy indicate the adsorption of poly(vinyl alcohol) at the surface of the particles. The doping agent used during the enzymatic polymerization of aniline influenced morphology and thermal stability of the synthesized particles. Polyaniline colloids prepared using P-toluenesulfonic acid showed spherical morphology and a narrow size distribution as shown by scanning electron microscopy and dynamic light scattering. (c) 2006 Elsevier Ltd. All rights reserved.