In this work, a novel route for fabrication of platinum-polyaniline nanofilms at a liquid vertical bar liquid interface is proposed. This method synthesizes Pt nanoparticles incorporated in conductive PANI by reduction of H2PtCl6 to Pt nanoparticles and chemical oxidation polymerization of aniline simultaneously. The liquid vertical bar liquid interface offers a unique microenvironment for confining the 2D growth of PANI to form Pt-PANI nanofilms. The Pt-PANI nanofilms are characterized by field emission scanning electron microscopy, UV-Vis absorption spectroscopy, FTIR spectroscopy, X-ray photoelectron spectroscopy, H-1 NMR spectroscopy and electrochemical impedance spectra. The Pt-PANI nanofilms show enhanced electrical conductivity compared to the chemically polymerized PANI. The conductivity of Pt-PANI nanofilms is potential-dependent, which makes them promising reversibly potential-switchable materials. (c) 2004 Elsevier B.V. All rights reserved.