Nano-WSe(2) Is Absorbable and Transformable by Rice Plants †

As typical transition metal dichalcogenides (TMDC), tungsten selenide (WSe(2)) nanosheets (nano-WSe(2)) are widely used in various fields due to their layered structures and highly tunable electronic and magnetic properties, which results in the unwanted release of tungsten (W) and selenium (Se) into the environment. However, the environmental effects of nano-WSe(2) in plants are still unclear. Herein, we evaluated the impacts and fate of nano-WSe(2) and micro-WSe(2) in rice plants (Oryza sativa L.). It was found that both nano-WSe(2) and micro-WSe(2) did not affect the germination of rice seeds up to 5000 mg/L but nano-WSe(2) affected the growth of rice seedlings with shortened root lengths. The uptake and transportation of WSe(2) was found to be size-dependent. Moreover, W in WSe(2) was oxidized to tungstate while Se was transformed to selenocysteine, selenomethionine, Se(IV) and Se(VI) in the roots of rice when exposed to nano-WSe(2), suggesting the transformation of nano-WSe(2) in rice plants. The exposure to nano-WSe(2) brought lipid peroxidative damage to rice seedlings. However, Se in nano-WSe(2) did not contribute to the synthesis of glutathione peroxidase (GSH-Px) since the latter did not change when exposed to nano-WSe(2). This is the first report on the impacts and fate of nano-WSe(2) in rice plants, which has raised environmental safety concerns about the wide application of TMDCs, such as WSe(2) nanosheets.