Preparation, fractal surface morphology and photocatalytic properties of TiO2 films

Opaque nanostructured glass-supported TiO2 films were prepared from a commercial and a laboratory synthesised precursor, respectively. Qualitative film analysis was performed with atomic force microscopy (AFM), and surface parameters such as average grain diameter, roughness exponent and fractal dimension were determined. The TiO2 surfaces present important roughness due to the large aggregates formed by the interconnected TiO2 particles. Fractal dimension was found to range between 2.100 and 2.450, depending on the scanned range and the preparation method. The photocatalytic activity of the films towards the degradation of 2,4-dichlorophenol in acidic aqueous solutions has been investigated. The organic pollutant undergoes effective photodegradation upon photolysis with UV/near visible light. The film morphology, surface characteristics and efficiency remained intact after use. Comparison of the film activities showed that the films prepared from a commercial colloid possess a better photocatalytic performance than the sol-gel films and this can be understood in terms of their smaller particle size, higher roughness and specific surface area. (C) 1999 Elsevier Science S.A. All rights reserved.