Abstract: To explore the preparation method of cubic AgNPs and its toxic effect on aquatic organisms, silver nanocubes were synthesized by liquid reduction method through the reduction of silver nitrate with NaBH₄ (sodium borohydride) in the presence of PVP (polyvinyl pyrrolidone) and NaCl (sodium chloride). We examined its exposure toxicity on Chlorella vulgaris under the conditions of AgNPs colloidal solution concentrations of 0, 0.5, 1, 2 and 5 mg·L^-1 cubic AgNPs. Results showed that the concentration of NaCl and NaBH₄ solution had great influence on the morphology and size of AgNPs particles. When the concentration of NaCl and NaBH₄solution was 0.5 mol·L^-1, the morphology of silver nanocubes was the most regular, and their size was within a range of 200-300 nm. The cell densities and chlorophyll were markedly decreased, with a dose-effect. The content of reactive oxygen species (ROS) and superoxide dismutase (SOD) in treatment groups increased significantly after 48 h exposure. Obviously damaged cell morphology in C. vulgaris caused by cubic AgNPs was observed by TEM, suggesting that cubic AgNPs had toxic effect on C. vulgaris. Our results revealed the potential risks of AgNPs in aquatic environment.

Key words: liquid-phase reduction, silver nanocube, Chlorella vulgaris, exposure, toxicity.