▎ 摘　　要

NOVELTY - Preparation of manganese, boron, nitrogen co-doped graphene quantum dots involves (1) taking 0.0025-0.005 mol% citric acid, 0.01-0.04 mol% urea, 0.0001-0.0003 mol% borax, and 0.06-0.08 mol% manganese chloride tetrahydrate, dissolving in distilled water and ultrasonically treating to make the solution clear aqueous solution, (2) transferring obtained solution to a stainless steel autoclave lined with Teflon, and heating at 180degrees Celsius for 7-10 hours, (3) cooling reaction kettle to room temperature naturally, and centrifuging the obtained pale yellow clear solution by a centrifuge to remove the precipitation, (4) dialyzing the resulting fluid in a dialysis bag, (5) freeze-drying to obtain a brownish-yellow solid powder. USE - Preparation of manganese, boron, nitrogen co-doped graphene quantum dots used for detecting ferric ions (claimed). ADVANTAGE - The detection function of ferric ions in the environment is simple and easy to operate, the changes under the UV lamp are visible to the naked eye, and the concentration of ferric ions in the environment exceeding the standard is directly and quickly detected.