Sulfur vacancies affect the environmental fate, corona formation, and microalgae toxicity of molybdenum disulfide nanoflakes

Sulfur vacancy (SV) defects have been engineered in two-dimensional (2D) transition metal dichalcogenides (TMDs) for high performance applications in various fields involving environmental protection. Understanding the influence of SVs on the environmental fate and toxicity of TMDs is critical for evaluating their risk. Our work discovered that SVs (with S/Mo ratios of 1.65 and 1.32) reduced the dispersibility and promoted aggregation of 2H phase molybdenum disulfide (2H-MoS2, a hot TMD) in aqueous solution. The generation capability of •O2- and •OH was increased and the dissolution of 2H-MoS2 was significantly accelerated after SVs formation. Different with pristine form, S-vacant 2H-MoS2 preferentially harvested proteins (i.e., forming protein corona) involved in antioxidation, photosynthetic electron transport, and the cytoskeleton structure of microalgae. These proteins contain a higher relative number of thiol groups, which exhibited stronger affinity to S-vacant than pristine 2H-MoS2, as elucidated by density functional theory calculations. Notably, SVs aggravated algal growth inhibition, oxidative damage, photosynthetic efficiency and cell membrane permeability reduction induced by 2H-MoS2 due to increased free radical yield and the specific binding of functional proteins. Our findings provide insights into the roles of SVs on the risk of MoS2 while highlighting the importance of rational design for TMDs application.