▎ 摘　　要

NOVELTY - Preparing nitrogen-doped graphene quantum dot comprises (i) mixing carbon nitrogen source, trimethylbenzene, sulfuric acid and ethanol, injecting into ordered mesoporous silicon dioxide, heating for 2-8 hours at 60-100 degrees C, reacting for 3-10 hours at 120-180 degrees C and heating for 1-5 hours at 700-1000 degrees C nitrogen atmosphere to obtain carbon/nitrogen/silicon dioxide nano composite, where the carbon and nitrogen source is pyrrole or quinoline, and (ii) reacting carbon/nitrogen/silicon dioxide nanometer compound in concentrated nitric acid vapor to obtain the nitrogen-doped graphene quantum dot. USE - The method is useful for preparing nitrogen-doped graphene quantum dot (claimed). ADVANTAGE - The dot has uniform size, narrow particle size distribution, good dispersibility and water solubility, and good selectivity to ascorbate and good accuracy. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for detection method of ascorbate comprising mixing nitrogen-doped graphene quantum dot solution with iron (3+) solution to obtaining Fe3+N-GQDs mixed liquid, adding fluorescence intensity mixing liquid into Fe3+ N-GQDs sample, measuring the obtained solution according to predetermined standard curve to calculate content of ascorbate examination in the liquid measuring object.