MoS₂ Nanosheet-Based Membranes for Antibacterial Applications

With the rapid development of two-dimensional nanomaterials, the applications of nanomaterials will inevitably release to the natural environment. In this study, we investigated the interactions between environmental microorganisms and nanomaterial applications, where we chose MoS2 (metallic 1T and semiconducting 2H) and MoS2 membranes as the representative two-dimensional nanomaterial applications, and Escherichia coli was selected as model bacteria to represent the environmental microorganism. In suspension, it was found that the antibacterial efficiency of 1T-MoS2 was around 30% higher than that of 2H-MoS2 nanosheets at low MoS2 concentrations. This is because the distorted octahedral coordination structure endows 1T-MoS2 with higher conductivity than 2H-MoS2, therefore benefitting the electron transfer ability to produce reactive oxygen species (ROS), such as O2·– and H2O2, which are both absent for 2H-MoS2. However, the common antibacterial pathways shared by both 1T-MoS2 and 2H-MoS2 are glutathione (GSH) oxidation that causes oxidative stress in bacterial cells and cell membrane disruption in direct contact with the sharp edges of MoS2 nanosheets. Interestingly, 1T-MoS2 and 2H-MoS2 have similar antibacterial efficiencies of around 75% when applied on the poly(ether sulfone) (PES) membrane surfaces for anti-biofouling purposes due to the similar physical damages induced by the sharp edges of two-dimensional structures with 1T-MoS2 and 2H-MoS2. The results imply that bacterial physical damages induced by 1T- and 2H-MoS2 membranes play a more important role than chemical oxidative stress. This study provides information that scientists and engineers should pay attention to the applications using nanomaterials since different application forms could have different interactions with the potential environmental microorganism.