Componential and molecular-weight-dependent effects of natural organic matter on the colloidal behavior, transformation, and toxicity of MoS2 nanoflakes.

The potential widespread applications in water processing have rendered the necessity for investigations of the fate and hazard of molybdenum disulfide (MoS 2) nanosheets. Herein, it was found that humic acid (HA) had better performances toward stabilizing pure 2H phase MoS 2 and chemical-exfoliated MoS 2 (ce-MoS 2) in electrolyte solutions than fulvic acid (FA), and molecular weight (MW)-dependent manners were disclosed due to steric repulsions. Compared with darkness, the extent to which the aggregation and sedimentation of ce-MoS 2 facilitated by visible light irradiation was greater in the presence of HA and FA fractions, likely due to the introduction of stronger plasmonic dipole-dipole interaction and Van der Waals attraction forces. HA-triggered structural disintegration of nanosheets was performed after irradiation and it was observed to be more significant with the increase in MWs, whereas the MW-dependent dissolution of MoS 2 caused by FA was much quicker than that by HA owing to the higher generation of singlet oxygen. Moreover, FA lowered the bioavailability of MoS 2 and relieved its toxicity to zebrafish more effectively than HA. Our findings boost the insights into the effects of organic molecules on the fates and hazards of MoS 2 , providing guidance for the MoS 2 -based nanotechnological development on environment. [Display omitted] HA exhibited better performance toward stabilizing 2H-MoS 2 and ce-MoS 2 than FA. Illumination remarkably accelerated the aggregation and sedimentation of ce-MoS 2. Low MW HA and FA fractions strengthened the light-assisted ce-MoS 2 aggregation. Higher 1O 2 production led to faster MW-dependent MoS 2 dissolution in FA than HA. FA reduced MoS 2 bioavailability and relieved its toxicity more effectively than HA. [ABSTRACT FROM AUTHOR]