Bactericidal activities and synergistic effects of Ag-TiO_{2 and Ag-TiO_{2-SiO_{2 nanomaterials under UV-C and dark conditions

The synergistic effects of silver and titanium dioxide revealed the potential utility of Ag–TiO2–based materials as safe disinfectants in drinking water treatment. In this work, disinfection of Escherichia coli bacteria (ATCC®25922) by using impregnation–derived Ag–P25 and gel–derived Ag–TiO2–SiO2 nanomaterials was conducted under both UV–C exposure and dark conditions to elucidate their synergistic effects. Under UV–C irradiation, the bactericidal activity of impregnation–derived Ag–P25 was superior to the one observed with only UV–C, a combination of AgNO3 and UV–C, or a combination of TiO2 and UV–C. Meanwhile, the bactericidal activities of the Ag–P25 nanoparticles in dark were quite lower than those under UV–C light, but higher than that of bare TiO2(P25) or AgNO3in dark conditions. The results also proved that synergistic effect of the gel–derived Ag–TiO2–SiO2 nanomaterial made bactericidal activities stronger than those of the Ag–P25 counterpart under both UV–C light and dark conditions. This could be ascribed to the small particle size of gel–derived Ag–TiO2–SiO2 (ca. 9 nm) when compared with that of impregnation–derived Ag–P25 (ca. 21 nm).