Synthesis and Characterization of N-Doped Carbon Quantum Dots and Its Toxic Effects on Chlorella vulgaris

Graphical The toxicity of carbon dots synthesized using cholinium bitartrate against Chlorella vulgaris was assessed.The carbon dots with low concentration present low toxicity to microalga.The oxidative stress and cell damage were the main toxic mechanisms of carbon dots to green alga. Carbon quantum dots (CQDs) are considered as eco-friendly nanomaterials and suitable alternatives for traditional metal quantum dots. However, their high hydrophilicity and nanoscale size of CQDs pose a significant risk to aquatic organisms considering their widespread application. In this study, Chlorella vulgaris was selected as a model organism to assess the ecotoxicity of CQDs synthesized using choline bitartrate via a pyrolysis method. The effects of the CQDs on algal growth, antioxidant activity, photosynthetic pigment, and malondialdehyde levels have been extensively studied. Algal growth was inhibited by CQDs with a median effective concentration (EC 50 ) > 271 mg/L. After 4 days of exposure, chlorophyll content, respiratory rate, and protein content of the green alga declined by 14.0–91.75%, 73.4% and 24.4%, respectively. The CQDs caused excessive accumulation of reactive oxygen species (ROS) in Chlorella vulgaris and induced oxidative stress and physical damage to the algal cells. Our findings contribute to the potential application and risks assessment of the CQDs.