Study of Nd-doping effect and mechanical cracking on photoreactivity of TiO2 thin films

Pure and Nd-doped TiO2 thin films were fabricated by reactive d.c. magnetron sputtering at low-temperature from a pure Ti target. The structure of films was analyzed by X-ray diffraction (XRD). In order to study the Nd-doping effect on TiO2 photocatalytic activity, some films were deposited on microscope glass substrates under a constant total sputtering pressure and using different Nd-doping concentrations. The effect of different Nd-dopant concentrations and its influence on the photocatalytic efficiency has been explored by measuring the photodegradation of rhodamine-B (RhB) aqueous solution under radiation of UV light. It is principally that for comparison between heat treatment and doping process on TiO2 photocatalytic efficiency (important under the point of view of energy costs related with industrial sputtering techniques), crystalline TiO2 films were also produced by thermal annealing. It was found that comparing with annealed pure TiO2 films, Nd-doping do not improve the photocatalytic activity. At the same time, it was observed that there seems to exist a dopant concentration band for optimal photoreactivity. In order to study the effect of the film mechanical strength on photocatalytic activity, fragmentation tensile tests were also done on TiO2/PET (polyethylene terephthalate) substrates at increasing applied strains. It was found that increasing the magnitude of the applied tensile strain, pure TiO2 becomes more photocatalytic efficient.