Environmental Transformations and Algal Toxicity of Single-Layer Molybdenum Disulfide Regulated by Humic Acid

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The environmental transformations of nanomaterials are correlated with their behaviors and ecological risks. The applications of single-layer molybdenum disulfide (SLMoS 2 ) have rapidly developed in environmental fields, but the potential transformations and biological effects of SLMoS 2 remain largely unknown. This study revealed that humic acid (HA, over 10 mg/L) induced the scrolling of SLMoS 2 with light irradiation over a 56-day incubation. The colloidal stability of SLMoS 2 increased, and the aggregation ratio decreased from 0.59 ± 0.07 to 0.08 ± 0.01 nm/min after HA hybridization. Besides, compared with pristine SLMoS 2, the chemical dissolution rate of SLMoS 2 was up to 4.6-fold faster with HA exposure. These results demonstrate that HA affects the environmental fate and transformations of SLMoS 2 . SLMoS 2 –HA possessed a significantly widened direct band gap (2.06 eV) compared with that of SLMoS 2 (1.8 eV). SLMoS 2 acted as an electronic acceptor from HA, resulting in the separation of electron–hole pairs. Consequently, SLMoS 2 –HA exhibited stronger peroxidase-like catalytic activity, which was approximately 2-fold higher than that of SLMoS 2 . Moreover, the morphology and layered structure of SLMoS 2 changed, and the damage SLMoS 2 inflicted on microalgae was significantly reduced. This work provides insights into the behaviors and related biological risks of SLMoS 2 in aqueous environments.