Antibacterial activities of gel-derived Ag-TiO₂-SiO₂ nanomaterials under different light irradiation

Gel-derived Ag-TiO₂-SiO₂ nanomaterials were prepared by sol-gel process to determine their disinfection efficiency under UV-C, UV-A, solar irradiations and in dark condition. The surface morphology and properties of gel-derived Ag-TiO₂-SiO₂ nanomaterials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and BET specific surface area. The results showed that the average particle size of Ag-TiO₂-SiO₂ was around 10.9–16.3 nm. SiO₂ mixed with TiO₂ (the weight ratio of Si to Ti = 10:90) in the synthesis of Ag-TiO₂-SiO₂ by sol-gel process was found to increase the specific surface area of the obtained photocatalyst (164.5 m²g⁻¹) as compared with that of commercial TiO₂(P25) (53.1 m²g⁻¹). Meanwhile, Ag doped in TiO₂ (the mole ratio of Ag to TiO₂ = 1%) decreased the specific surface area to 147.3 m²g⁻¹. The antibacterial activities of gel-derived Ag-TiO₂-SiO₂ nanomaterials were evaluated by photocatalytic reaction against Escherichia coli bacteria (ATCC®25922). Ag-TiO₂-SiO₂ nanomaterials was observed to achieve higher disinfection efficiency than the catalyst without silver since both Ag nanoparticles and ions exhibit a strong antibacterial activity and promoted the e⁻ – h⁺ separation of TiO₂. The bactericidal activity of Ag-TiO₂-SiO₂ nanomaterial under light irradiation was superior to that under dark and only light. The reaction time to achieve a reduction by 6 log of bacteria of UV-C light alone and Ag-TiO₂-SiO₂ with UV-C light irradiation were 30 and 5 minutes, respectively. In addition, the superior synergistic effect of Ag-TiO₂-SiO₂ under both UV-A and solar light as compared to that under UV-C counterpart could be ascribed to the red-shift of the absorbance spectrum of the Ag doped TiO₂-based catalyst