Papers Abstract

Ag deposition effects on the photocatalytic activity of nanoparticulate TiO22 ― Comparison of gamma irradiation and UV irradiation methods
Rutile phase TiO2 nanoparticles were synthesized first by a modified polyol based sol–gel technique. One important aspect of this work is that the less common rutile phase of TiO2 could be synthesized under mild conditions of temperature and pH. Then these TiO2 nanoparticles were impregnated with Ag using radiation methods i.e. UV-radiation and γ-radiation. This resulted in the formation of Ag–TiO2 nanocomposites. The differences in structure, crystallinity and size of the Ag–TiO2 nanocomposites depends strongly on the reductive power of the reducing species involved as has been ascertained by TEM, XRD and XANES study. The weakly reducing free radicals generated from glycerol via the UV-irradiation method leads to formation of tetrapod precursor like composite nanoparticles of lower crystallinity. On the other hand, the strongly reducing hydrated electron (in the γ-irradiation method) leads to single crystalline, discrete and spherical Ag–TiO2 nanocomposites with traces of Ti2O3. We have been successful in preparing Ti2O3 which is a Magneli phase (MP) Ti sub-oxide, without calcination at very high temperatures. The photocatalytic efficiency of the composites is better than TiO2 itself. The photocatalytic efficiency of the nanocomposites depends on their structure and crystalline nature which can be ultimately correlated to the efficiency of production of active oxygen species like •OH. The presence of the narrow band gap Ti2O3 phase enhances photocatalytic activity of rutile TiO2.