Violet Phosphorus Nanosheets Exhibit Higher Toxicity in the Freshwater Microalgae Tetradesmus obliquus than Black Phosphorus Nanosheets

The potential environmental risks of two-dimensional (2D) phosphorene nanomaterials are gaining attention as their promising applications continue to expand. Violet phosphorus (VP) has been demonstrated to be a more stable phosphorene nanomaterial compared to black phosphorus (BP). However, current research has primarily focused on the toxic effects of BP, with limited information available regarding the toxicity of VP. This study comparatively analyzed the ecotoxicity and mechanisms of action of environmentally relevant concentration exposures of the common green algae Tetradesmus obliquus to BP and VP nanosheets. The results revealed that VP exhibited a greater growth inhibitory effect on the algae compared to BP, which was linked to disruptions in cell membrane function. Both BP and VP induced intracellular oxidative stress responses, yet they did not cause oxidative damage to algal cells. Transcriptional responses suggested that the number of differentially expressed genes in the algae exposed to VP was 29 times higher than that in the algae exposed to BP. Metabolomic analysis indicated that the number of differentially expressed metabolites induced by VP exposure in the algae was twice as high as the changes induced by BP. Furthermore, integrated transcriptome and metabolome analyses highlighted significant differences between BP and VP in core pathways, key metabolites, and driving genes. The findings of this study underscore the importance of considering the impact of different types of phosphorene materials when assessing their environmental risks.