▎ 摘　　要

This paper reports the preparation and application of folic acid-conjugated nitrogen-doped graphene quantum dots (N-GQDs) as a fluorescent diagnostic material for MCF-7 cells of breast cancer. N-GQDs were prepared by a hydrothermal method using citric acid as the carbon source and diethylamine as the nitrogen source. The doping of different amounts of nitrogen content was effectively controlled by diethylamine. As the amount of nitrogen increased, more binding sites on the N-GQDs were supplied to the folic acid. Laser confocal scanning microscopy showed that increased folic acid binding facilitated the recognition of and entry to cancer cells, which made the labeled cells emit a stronger fluorescence and thus the cancer cells could be better detected. Cytotoxicity tests showed that the material was of low cytotoxicity, making it a promising prospect for fluorescent probes.