Toxicity of exfoliated-MoS2 and annealed exfoliated-MoS2 towards planktonic cells, biofilms, and mammalian cells in the presence of electron donor

We demonstrate for the first time that suspensions of single-layered MoS2 nanosheets can act as photocatalytic antimicrobial materials under visible light in the presence of ethylenediaminetetraacetic acid (EDTA) as an electron donor. The antimicrobial capacity of exfoliated MoS2 (Ex-MoS2) was found to be 5.7 times higher than that of annealed exfoliated MoS2 (Ae-MoS2) against planktonic cells in the presence of 40 ppm EDTA. This difference in the antimicrobial performance was attributed to the 1T-phase of Ex-MoS2, which presents higher electron conductivity than that of Ae-MoS2. This higher electron conductivity of Ex-MoS2 led to increase generation of reactive oxygen species (ROS), as observed by the superoxide anion and hydrogen peroxide production assays under visible light. Additionally, Ex-MoS2 could also inactivate 65% of mature E. coli K12 biofilms without significant cytotoxicity to mammalian fibroblast cells. The suspension of single-layered MoS2 nanosheets opens up new opportunities for the development of advanced functional nanomaterials for biomedical and environmental applications.