Highly Luminescent Carbon Dots Synthesized by Microwave-Assisted Pyrolysis and Evaluation of Their Toxicity to Physa acuta

As a newly emerging class of nanomaterials, carbon dots have increasingly attracted researchers' attention. However, their potentially adverse environmental effects are yet largely unknown. In this work, the highly luminescent carbon dots were synthesized by microwave-assisted pyrolysis of tris(hydroxymethyl)aminomethane (Tris) and citric acid. Then acute and chronic toxicities of carbon dots to Physa acuta (P acuta), as well as their effect on reproduction, were evaluated using the as-synthesized dots as an example. The quantum yield of the as-synthesized carbon dots was up to 53.5% excited at 360 nm with the most fluorescent fraction of 82.6% after simple purification by gel column. The results showed that no acute but chronic toxicities to P acuta exposed to different treatment concentrations of the as-synthesized carbon dots were observed with dose dependence. In addition, the fecundity of P acuta was promoted significantly by the carbon dots at the concentrations of 0.5 and 1.0 mg/mL, yet inhibited at the concentration of 3.0 mg/mL after 12-day exposure. Mainly distributing in the visceral mass might be responsible for the effects of the carbon dots on the survival and fecundity of P acuta. And there was no further evidence to confirm that the carbon dots can cause malformation in developing embryos.