Oxidative and membrane stress-mediated antibacterial activity of WS2 and rGO-WS2 nanosheetsElectronic supplementary information (ESI) available: Growth kinetics of four bacteria with different concentrations of rGO, WS2 and rGO-WS2; optical microscopic images of the bacterial cells exposed to rGO, WS2 and rGO-WS2 nanosheets at 100 μg mL−1 concentrations for 2 h; superoxide radical anion production by XTT experiments for 24 h by rGO, WS2 and rGO-WS2 nanosheets; ROS production by the rGO-WS2 compo

Graphene-based materials have strong cytotoxic attributes against bacteria due to their unique physicochemical properties. We examined the antibacterial activities of nanosheets of the graphene analogue tungsten disulphide (WS 2 ) and a composite of reduced graphene oxide-tungsten disulphide (rGO-WS 2 ), comparing them with reduced graphene oxide (rGO) by a time and concentration dependent viability assay and growth curve studies against four bacterial strains: Gram negative Escherichia coli ( E. coli ) and Salmonella typhimurium ( S. typhimurium ), and Gram positive Bacillus subtilis ( B. subtilis ) and Staphylococcus epidermidis ( S. epidermidis ). The nanosheets of the rGO-WS 2 composite caused a more significant retardation in bacterial growth and inhibitory effect on the tested bacterial strains than WS 2 , followed by rGO. The tested E. coli and B. subtilis strains were more susceptible than the other strains. A mechanistic study revealed that rGO and WS 2 did not produce the superoxide anion (O 2 &z.rad;− ) or reactive oxygen species (ROS), but the nanocomposite of rGO-WS 2 did produce both. However, all these materials did oxidize glutathione, which serves as a redox state mediator in bacteria. We conclude that the antimicrobial mechanism is due to the combined effect of initial cell deposition on the rGO-WS 2 materials, the membrane stress due to direct contact with the nanosheets, and the produced superoxide anion-independent oxidation mechanisms. The beneficial aspects of the physicochemical properties of rGO-WS 2 , such as its size and conductivity, can be precisely customized to reduce its health and environmental risk factors. We examined the antibacterial activities of nanosheets of the graphene analogue tungsten disulphide (WS 2 ) and a composite of reduced graphene oxide-tungsten disulphide (rGO-WS 2 ).