Photo-induced Oxidation and Reduction by Plasmonic AgTiO2 nanocomposites under UV/Sunlight

Abstract

The present study demonstrates the effect of variable (1-3 wt%) amount of deposited Ag on TiO2 surface for catalytic oxidation/reduction reactions under UV or sunlight irradiation. The physiochemical properties of prepared Ag-TiO2 nanocomposites were studied using different techniques (DRS, DLS, SEM-EDS). It was found that the hydrodynamic size of commercially available TiO2 was nearly 252 nm which further increased by increasing amount of Ag cocatalyst deposition over TiO2 where plasmonic absorption band at 463 nm is appeared in the optical absorption spectra (DRS) due to Ag deposition onto TiO2. This observed change was due to enhancement of both number and size of loaded Ag nanoparticles on the surface of TiO2. Moreover, photoluminescence intensity of Ag-TiO2 was highly quenched with increased amount of Ag loading indicating lower recombination rate of photogenerated electrons and holes during photoexcitation. The 3 wt% Ag-TiO2 nanocomposite showed highest photoactivity for oxidation of p-Nitrobenzaldehyde to Nitrobenzoic acid under UV and sunlight. However, 2 wt% Ag-TiO2 proved to be more efficient during reduction of m-Nitrobenzoic to m-Aminobenzoic acid under UV irradiation. This is probably due to blockage of active site on the surface of catalyst. Thus, different amount of Ag (1-3 wt%) co-catalyst photodeposition is highly influenced the TiO2 photocatalytic activity.