Different approaches for enhancing photocatalytic properties of TiO2:Au thin films deposited by DC sputtering

INTRODUCTION: Titanium dioxide (TiO2) thin films showed as promising materials for photocatalytic degradation of pollutants in water under irradiation of UV-light. It is favorable material for photocatalytic processes because of its non-toxicity, high photosensitivity, large band gap and stability. One of the way to increase efficiency of TiO2 thin films is by doping and coating with metals. Metal-doped TiO2 can reduce electron-hole recombination and increase hydroxyl radical concentration on the surface of TiO2, resulting in increase in the photocatalytic activity1. In studies of J.M.Jung at al.1 with Au-buffered TiO2 thin films and V. S. Mohite et al.2 with doped TiO2 thin films showed that this systems have enhanced photocatalytic activity in comparison to pure TiO2 thin films. Also recent study3 showed that Au doped TiO2 thin films are great candidates beside photocatalysis for enhancing visible light water splitting. EXPERIMENTAL STUDY TiO2 and TiO2:Au thin films were obtained by DC magnetron sputtering of Ti target with Ar ions in O2 atmosphere. In the case of doped TiO2 thin films with Au, three different systems were deposited for comparison (fig.1): Buffering Au layer into the TiO2 layer (b), subsurface buffering of Au with island formation of Au on the surface and etching the surface of TiO2 layer by HF and applying Au nanoparticles on the surface. Annealing of the samples was performed in air and N2 atmospheres on 600 °C for better crystallinity and release of defects. For structural analyses XRD, XPS, TEM and SEM methods were used, while for optical characterization UV/Vis method was used. The photo-degradation rate was measured using Rhodamine B which simulated pollutant. Fig. 1: Experimental setup. RESULTS AND DISCUSSION Structural analysis has shown that as deposited films have amorphous-like structures, while post-deposition thermal annealing in air for 3 hours inducted significantly better crystallinity in thin films with anatase phase dominating. S