Effect of Ag Doping on Antibacterial and Photocatalytic Activity of Nanocrystalline TiO2

Abstract

In the present study, nanocrystalline pure TiO2 and 5 mol% silver doped TiO2 (Ag-TiO2) powders were prepared by sol-gel route. The prepared powders were characterized by X-ray diffraction (XRD) and UV-Visible spectroscopy (UV-Vis) for their phase composition and optical properties, respectively. The antibacterial property of TiO2 and Ag-TiO2 was assessed by spread plate method against Escherichia coli as test bacteria. The photocatalytic activity of Ag-TiO2 was studied by measuring degradation of Methylene blue (MB) under UV Irradiation and the results were compared with pure TiO2. Further, the effect of temperature and dye concentration on degradation efficiency of pure TiO2 was studied. XRD results confirm the presence of anatase phase in both the samples and the average crystallite size of both samples were found in the order of 6-15 nm. Addition of Ag reduces the band gap of TiO2 from 3.1 eV to 2.9 eV. In 24 h of incubation period, Ag-TiO2 showed complete inhibition of growth of Escherichia coli compared to pure TiO2. It was observed that the degradation efficiency was more for TiO2 annealed at 500 ˚C compared to as-synthesis TiO2 and it decreases with further increase in temperature. In addition, as the dye concentration increases, the degradation efficiency of pure TiO2 decreases. Among, TiO2 and Ag-TiO2 samples, MB degradation efficiency was higher for Ag-TiO2 compared to pure TiO2. Photo degradation of MB was modeled with power law kinetics and was observed to follow first order kinetics and the rate constant was enhanced with Ag doping in TiO2.