Graphene oxide decorated TiO2 and BiVO4 nanocatalysts for enhanced visible-light-driven photocatalytic bacterial inactivation

Photocatalytic disinfection of drinking water is habitually performed by an ultraviolet source that epitomizes only 4% of the total solar energy, increasing the cost and prolonging the whole process. Therefore, currently, functionalized nanomaterials are developed, which can pave the way for the utilization of visible light, thereby speeding up the disinfection process in a cost-effective manner. In this study, we synthesized titanium dioxide (anatase) and bismuth vanadate (monoclinic) nanoparticles through the sol-gel technique. This is followed by a simple-blending process with graphene oxide (GO) to produce nanocomposites, such as GO/titanium dioxide (GOT) and bismuth vanadate (GOB), by varying the ratios of nanostructures accordingly and confirmed by different characterization techniques. 1.5 GOT and 1.5 GOB (nanocomposites of 1.5 wt.% GO with TiO2 and BiVO4 nanoparticles) showed enhanced inactivation efficiency of Escherichia coli (E.coli) K12 (model microorganism). Hydroxyl (OH) and superoxide (O-2(-)) radicals were found to be responsible for producing reactive oxygen species (ROS), playing a crucial role in photocatalytic disinfection, which was evaluated through scavenger study. We attained disinfection of E.coli K12 having a concentration of 107 CFU/mL with a smaller quantity of 1.5 GOT (1.05 g/L), obtaining 99.9 % (3 log units) of inactivity in 30 min. while for 1.5 GOB (0.1 g/L) resulting in 89 % (<1 log units) disinfection in 60 min. under simulated visible-light. Here, we propose a green environmental technology for nanocatalysts' facile synthesis with enhanced disinfection of bacteria, which corroborates well with the possible mechanism.