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

Abstract

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.