Morphology and photocatalytic activity of highly oriented mixed phase titanium dioxide thin films

Abstract

Thin TiO2 films on quartz substrates were prepared by spin coating of undoped and metal-ion-doped Sol–Gel precursors. These films were characterised by Scanning Electron Microscopy, Laser Raman Microspectroscopy, X-ray Diffraction and UV–Vis Transmission. The photocatalytic performances of the films were assessed by the photo-degradation of methylene-blue in aqueous solution under UV irradiation. Films exhibited a high degree of orientation and a thermal stabilization of the anatase phase as a result of substrate effects. In the absence of dopants, the rutile phase formed as parallel bands in the anatase which broadened as the transformation progressed. TiO2 films doped or co-doped with transition metals exhibited the formation of rutile in segregated clusters at temperatures under ~800°C as a result of increased levels of oxygen vacancies. Photocatalytic activity of the films synthesised in this work was low as likely a result of poor TiO2 surface contact with dye molecules in the solution. The presence of transition metal dopants appears detrimental to photocatalytic activity while the performance of mixed phase films was not observed to differ significantly from single phase material.