Photocatalytic degradation of Rhodamine 6G on mesoporous titania films: Combined effect of texture and dye aggregation forms

Titania films with different textural properties have been synthesized using the so-gel spin-coating process. Titania sols were prepared with and without non ionic template agents, Pluronic (R) P123 and Brij56 (R), in order to evaluate the effect of the surface developed by the films on their photocatalytic activity. The morphology, surface composition, open porosity and pore size distribution of these films were investigated by transmission electronic microscopy, X-ray photoelectron spectroscopy and atmospheric ellipsometric porosimetry. The optical properties of the titania films were evaluated by UV-vis transmittance spectroscopy. The porosity released after burning the template at 400 degrees C reduces the refractive index of the coatings and the transmittance in the visible range becomes equal for naked and coated soda lime glasses. In parallel, the photocatalytic activity of the non porous and porous titania films was evaluated by following the photodegradation kinetics of Rhodamine 6G dye. Results show that the increase of the available active surface of the titania films affects the photocatalytic activity. However, this feature was not the only parameter responsible for the improvement of the photocatalytic efficiency. The aggregation form of the Rhodamine 6G dye was also related to titania film texture. This proved to have a marked impact on the photocatalytic performances. (C) 2011 Elsevier B.V. All rights reserved.