▎ 摘　　要

The preparation and biological applications of graphene quantum dots (GQDs) have attracted much attention. Here, a one-step hydrothermal method for synthesizing nitrogen-doped GQDs (N-GQDs) using graphene oxide (GO), ethylenediamine and hydrogen peroxide, simultaneously achieved oxidative cleavage and chemical reduction of GO. The average size of the synthesized N-GQDs was about 1.84 +/- 0.28 nm and their quantum yield of the N-GQDs reached about 0.46, which was higher than that of other GQDs synthesized by top-down methods. The cytotoxicity of these N-GQDs on Hela cells was evaluated using a cell counting Kit-8 assay. The effects of N-GQDs on different cell lines and fluorescence imaging were also observed by confocal laser scanning microscopy. The results suggested that these N-GQDs penetrated into cells by endocytosis and were promising fluorescent probes for biological imaging. (C) 2020 Elsevier B.V. All rights reserved.