Photocatalytic antibacterial performance of TiO2 and Ag-doped TiO2 against S. aureus. P. aeruginosa and E. coli

Abstract

This paper reports the structural and optical properties and comparative photocatalytic activity of TiO 2 and Ag-doped TiO 2 nanoparticles against different bacterial strains under visible-light irradiation. The TiO 2 and Ag-doped TiO 2 photocatalysts were synthesized by acid catalyzed sol–gel technique and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–vis spectroscopy and photoluminescence (PL). The XRD pattern revealed that the annealed sample of TiO 2 has both anatase and rutile phases while only an anatase phase was found in Ag-doped TiO 2 nanoparticles. The decreased band-gap energy of Ag-doped TiO 2 nanoparticles in comparison to TiO 2 nanoparticles was investigated by UV–vis spectroscopy. The rate of recombination and transfer behaviour of the photoexcited electron–hole pairs in the semiconductors was recorded by photoluminescence. The antimicrobial activity of TiO 2 and Ag-doped TiO 2 nanoparticles (3% and 7%) was investigated against both gram positive (Staphylococcus aureus) and gram negative (Pseudomonas aeruginosa, Escherichia coli) bacteria. As a result, the viability of all three microorganisms was reduced to zero at 60 mg/30 mL culture in the case of both (3% and 7% doping) concentrations of Ag-doped TiO 2 nanoparticles. Annealed TiO 2 showed zero viability at 80 mg/30 mL whereas doped Ag-TiO 2 7% showed zero viability at 40 mg/30 mL culture in the case of P. aeruginosa only.