Antibacterial Activity of TiO<sub>2</sub>-Ag-Nanoparticle under Visible Light

Abstract

A visible active antibacterial agent, namely TiO2-Ag-Nanoparticle has been prepared, characterized, and examined to combat E.coli bacteria in the present of the visible light. The preparation was carried out by reduction of AgNO3solution over TiO2photocatalyst under UV light exposure. TiO2-Ag nanoparticle was characterized using XRD, SEM and DRS instruments. The activity as an antibacterial agent has been tested for disinfection of E. coli bacteria in the contaminated well water. The antibacterial assay was carried out by visible light irradiation of the contaminated well water in the present of TiO2-Ag, as well as TiO2for comparison, for the various period. The antibacterial performance was represented as the number of the bacteria determined by colony counting method. Their XRD patterns probe that the Ag doping leads to the crystalline of TiO2partially destroyed and the average particle size of TiO2in TiO2-Ag is larger thanTiO2bare, and no peaks of Ag metal appeared, implying that the Ag silver is very small(nanoparticle) that may be inserted into the TiO2crystal lattice. Based on the DRS spectra it is observed that TiO2-Ag has visible light absorption meanwhile TiO2only can absorb the UV light. The antibacterial assessment demonstrates that the TiO2-Ag has high performance in the bacterial inactivation under visible light. Meanwhile, very low activity is shown by TiO2. Moreover, the increase of Ag loaded gives rise in the bacterial inactivation, but further increase leads to the inactivation slightly reduced. The extension time of the visible light exposure is found to promote more effective antibacterial process up to maximum level, and no effect was observed with the much longer time. It is also confirmed that a small amount of Ag is dissolved from TiO2-Ag NP during the antibacterial testing.