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

摘要

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.