Two kinds of TiO2/sulfonated polyaniline (SPAn) nanocomposite ultrathin films were fabricated by layer-by-layer (LBL) self-assembly technique on various solid surfaces. One was fabricated with self-doped sulforated polyaniline (SD-SPAn) and TiO2 sol, and another was with externally (HCl)-doped sulfonated polyaniline (ED-SPAn) and TiCl4. The linear growth of both the LBL films was proved by UV-vis spectroscopy. The ordered multilayer films were subsequently characterized by atomic force microscopy, cyclic voltammetry, and photoelectrochemical measurement. Their structure, electrochemical and photoelectrochemical properties were comparatively investigated. The morphology of ED-SPAn/TiO2 LBL films is evener and smoother than that of SD-SPAn/TiO2 LBL films. Two kinds of LBL films have different electrochemical behaviours, and ED-SPAn/TiO2 LBL films show a stabler but slower photocurrent response than SD-SPAn/TiO2 LBL films. (c) 2007 Elsevier B.V. All rights reserved.