Visible light photo catalytic inactivation of bacteria and photo degradation of methylene blue with Ag/TiO2 nanocomposite prepared by a novel method

Abstract Water purification is one of the worldwide problem and most of the conventional methods are associated with a number of drawbacks. Therefore it is the need of the day to develop new methods and materials to overcome the problem of water purification. In this research work we present a simple and green approach to synthesize silver decorated titanium dioxide (Ag/TiO 2 ) nanocomposite with an efficient photo catalytic activities. Phytochemicals of the Cestrum nocturnum leaf extract were used to synthesize silver nanoparticles (AgNPs), Titanium dioxide (TiO 2 ) and Ag/TiO 2 nanocomposite. To confirm the formation, crystal structure, particle size and shape of green synthesized nanoparticles and nanocomposite, they were characterized by UV–visible spectroscopy (UV–vis), X-ray diffraction spectroscopy (XRD), high resolution transmission electron microscopy (HRTEM), Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The AgNPs, TiO 2 and Ag/TiO 2 were evaluated for photo degradation of methylene blue (MB) and photo inhibition of Bacteria. The bio-synthesized Ag/TiO 2 nanocomposite was observed to have strong catalytic activities for photo reduction of MB and photo inactivation of bacteria as compared to bare AgNPs and TiO 2 . In the presence of Ag/TiO 2 , 90% of MB was degraded only in 40 min of irradiation. Alternatively the bare AgNPs and TiO 2 degraded less than 30% and 80% respectively of MB even in more than 100 min of irradiation. Similarly the Ag/TiO 2 has very strong photo inhibition efficiency towards Escherichia coli and Pseudomonas aeruginosa . The zone of inhibition of irradiated Ag/TiO 2 nanocomposites against E. coli and P. aeruginosa was 19 mm and 17 mm respectively which was two times higher than in dark. These promising photocatalytic activities of nanocomposite may be due to the highly decorated AgNPs over the surface of TiO 2 .