▎ 摘　　要

NOVELTY - A nitrogen-sulfur-doped graphene quantum dot (I) is claimed. USE - Nitrogen-sulfur-doped graphene quantum dot used for preparing lysine fluorescence detection reagent. ADVANTAGE - The nitrogen-sulfur-doped graphene quantum dot is rich in oxygen-containing functional groups, and has excellent water dispersibility and biocompatibility, and high luminosity and quantum efficiency. The quantum dot preparation method is simple and carried out under mild condition. Lysine has high selectivity and sensitivity, and is detected without being affected by coexisting amino acids and carbohydrate biomolecules such as alanine, proline, glycine, methionine, arginine, leucine, glucose, glucosamine, galactose, sucrose and other substances. DETAILED DESCRIPTION - A nitrogen-sulfur-doped graphene quantum dot of formula (I), is claimed. INDEPENDENT CLAIMS are included for the following: (1) preparation of the nitrogen-sulfur-doped graphene quantum dot, which involves adding 5-35 mL deionized water to citric acid and thiourea, stirring, transferring the mixed solution into a reaction vessel, heating, and dialyzing the obtained product using dialysis bag for three days; and (2) application of the nitrogen-sulfur-doped graphene quantum dot for preparing lysine fluorescence detection reagent.