Fabrication of nitrogen-doped graphene quantum dots based fluorescent probe and its application for simultaneous, sensitive and selective detection of umami amino acids

In this work, nitrogen-doped graphene quantum dots (N-GQDs) were synthesized by an efficient one-step hy-drothermal using hydrated citric acid and urea as the carbon and nitrogen sources, respectively. The fluorescent quantum yield of the N-GQDs was up to 88.20 %, and the fluorescence lifetime was 12.29 ns. Based on the excellent fluorescence property, water-soluble and low cytotoxicity of N-GQDs, a novel fluorescent probe was fabricated and used for simultaneous detection of L-glutamic acid (L-Glu) and L-aspartic acid (L-Asp). Herein, Al3+ was used as a chelant agent for L-Glu shielding. The sensitive response of the probe towards L-Glu and L-Asp presented a wide concentration range with a low detection limit (S/N = 3). The fluorescent probe showed good selectivity, high stability and acceptable reproducibility in the application of L-Glu/L-Asp simultaneous detection in chicken soup. Meanwhile, the detection results of the fluorescent probe were correlated well with those ob-tained by amino acid analyzer.