Ag deposition effects on the photocatalytic activity of nanoparticulate TiO2 — Comparison of gamma irradiation and UV irradiation methods

Abstract Rutile phase TiO 2 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 TiO 2 could be synthesized under mild conditions of temperature and pH. Then these TiO 2 nanoparticles were impregnated with Ag using radiation methods i.e. UV-radiation and γ -radiation. This resulted in the formation of Ag–TiO 2 nanocomposites. The differences in structure, crystallinity and size of the Ag–TiO 2 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–TiO 2 nanocomposites with traces of Ti 2 O 3 . We have been successful in preparing Ti 2 O 3 which is a Magneli phase (MP) Ti sub-oxide, without calcination at very high temperatures. The photocatalytic efficiency of the composites is better than TiO 2 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 Ti 2 O 3 phase enhances photocatalytic activity of rutile TiO 2 .