Photodegradation of dye pollutant under UV light by nano-catalyst doped titania thin films

Undoped and manganese ion-doped TiO2 powders and thin films have been prepared by sol–gel route. The concentration of the manganese in TiO2 powders and films varied from 2 to 10 mol%. These powders were annealed at different temperatures from 300 to 1000 °C while films were annealed at 450 °C for 1 h. Prepared samples were characterized by XRD, SEM, XPS, spectroscopic and contact angle measurement techniques. Photocatalytic activity, in terms of rate constant measured by degradation of methylene blue dye, under UV exposure was found to increase from 0.27 to 0.36 for 5 mol% doping while very small photo activity has been observed under visible light exposure. Hydrophillicity also shows the same behavior. Optical studies revealed the generation of allowed energy band in the forbidden gap at ∼0.63 eV below the conduction band. It has been concluded that Mn doping increases photocatalytic activity by scavenging the photogenerated electrons, thereby increasing the life time of charge carriers and increasing the exposed surface area by reducing the crystallite size.