Combinatorial synthesis and high throughput evaluation of doped TiO2 thin films for the development of photocatalysts

TiO2 thin films doped with various transition metals were systematically fabricated by combinatorial laser MBE technique. Alternating KrF excimer laser (lambda = 248 nm) ablation of TiO2 and Ti1-x MxO2 (M = transition metal) was employed to deposit combinatorial library of 18 samples for each dopant with different concentrations. Anatase films with c-axis orientation were grown epitaxially on SrTiO3(001) substrate while the rutile phase films with a-axis orientation were on Al2O3(0001) substrate. Solid solubility of transition metals in both the phases was determined by X-ray diffraction. The anatase phase was found to dissolve the transition metals in higher concentrations than rutile phase. The parallel evaluation of the photocatalytic activity of the doped TiO2 in combinatorial libraries was performed with respect to photodecomposition of water in presence of a small amount of oxidizing or reducing agent which induced pH changes on the pixels. The high throughput evaluation of combinatorially deposited photocatalytic thin films was realized by adopting a potentiometric pH field effect transistor for sensing such pH changes.