Surface modification and photosensitisation of TiO2 nanocrystalline films with ascorbic acid

Semi-transparent microporous TiO2 films on SnO2-coated conductive glass were prepared by applying a sol-gel process. Surface topography analysis was conducted with atomic force microscopy, which revealed a highly textured and rough surface, possessing a high capacity for adsorption of a diverse variety of compounds. Surface modification of the films with ascorbic acid results in the formation of a stable, coloured surface complex which red shifts the absorption threshold of TiO2, enhancing utilisation of the solar spectrum. Upon illumination in a liquid electrochemical cell, ascorbic acid injects electrons into the conduction band of the semiconductor, giving rise to electrical current. The incident-photon-to-current efficiency presents a maximum at 415nm (5.29%). (C) 2000 Elsevier Science S.A. All rights reserved.