The effects of trace element doping on the optical properties and photocatalytic activity of nanostructured titanium dioxide

The electronic and optical properties of many solids are due to crystal defects and impurities. The oxidized doping elements in TiO2 studied were Cr, V, Nb, Fe, Si, P, K, and Zn. The diffuse reflectance spectrum, brightness and tone values, and lightfastness and photochromic values were characterized, and the photocatalytic activity was measured for the degradation of methylene blue. In small amounts, chromium and vanadium were found to be the most effective doping elements. The photocatalytic activity was good with undoped and chromium-doped anatase samples, but it was at its worst with iron-doped samples. Cr doping was detrimental to the brightness value, but it increased the lightfastness of rutile. Vanadium was the most effective doping element in making anatase photochromic. When the photocatalytic uses of TiO2 were considered, the calcination temperature of the samples was, in general, optimum at 873 K. Some chromium-doped samples showed optimum photocatalytic activities at 673 K.