Synthesis of carbon nitride quantum dots and biocompatibility evaluation using C. elegans as a model organism

Carbon nitride quantum dots (CNQDs) were synthesized by the solid-phase method. The obtained CNQDs were characterized by XPS, TEM, FTIR and XRD. The results suggested that the CNQDs were ball-like nanoparticles (average diameter of 5 nm) with carboxyl and hydroxyl groups on the surface. The fluorescent emissions of the CNQDs were centered at 478 nm upon excitation with 365 nm UV light. The corresponding fluorescent quantum yield was measured as 32 %. The biocompatibility of the CNQDs with the model organism Caenorhabditiselegans (C. elegans) was systematically evaluated. The synthesized CNQDs enhanced the pharyngeal pumping rate, body length and life span of nematodes in a concentration-dependent manner after 24 h of exposure. Thus, the CNQDs affected the growth of the nematodes. The reproduction and motion capability indicators, including the egg laying rate and head thrash and body bend frequencies, were not influenced by the CNQDs. Therefore, the CNQDs did not show obvious toxicity to the C. elegans nematode model organism. The CNQDs could be taken up by nematodes, as characterized by fluorescence microscopy, proving that this material could be applied as a promising in vivo fluorescent imaging reagent.