▎ 摘　　要

NOVELTY - Preparation of nitrogen-doped graphene quantum dot with high selectivity comprises mixing citric acid and ammonia water at volume ratio of 2 g:20 mL to obtain mixed solution, transferring to PTFE-lined reaction kettle, hydrothermally reacting to 160-180 degrees C for 8-12 hours, naturally cooling to room temperature, heating, dialyzing, and freeze-drying. USE - Method for preparation of nitrogen-doped graphene quantum dot with high selectivity used for detection of hexavalent chromium ion (claimed), biological sensor, biological imaging, and high-sensitive fluorescence probe. ADVANTAGE - The product nitrogen-doped graphene quantum dot with high selectivity has low cell toxicity, good biological compatibility, and chromium ion strong detecting effect at detection limit of 50 nM.