▎ 摘　　要

NOVELTY - Preparing nitrogen-doped graphene quantum dots, comprises using sunflower pectin as a carbon source, dissolving into a certain volume of water to obtain a pectin solution, adding aqueous ammonia, ultrasonically treating, and hydrothermally treating the pectin solution, filtering the pectin solution after the hydrothermal reaction with a 0.22 mum aqueous filter membrane, placing the filtrate in a dialysis bag, and using deionized water as a buffer, performing dialysis for 48 hours, changing the water every 12 hours, and collecting the dialysate by rotary evaporation and concentrating, and drying. USE - The nitrogen-doped graphene quantum dot is useful for detecting iron ions in simulated gastrointestinal fluid (claimed). ADVANTAGE - The method provides nitrogen-doped graphene quantum dot with good biocompatibility, and is easy to be combined with other active functional groups. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for detecting iron ions in simulated gastrointestinal fluid.