▎ 摘　　要

NOVELTY - Cysteine modified graphene quantum dot (GQCY) is represented by (I). USE - Cysteine modified graphene quantum dot (GQCY) for preparing dopamine fluorescence detection reagent (claimed). ADVANTAGE - The cysteine modified graphene quantum dot is convenient operation, has good bio-compatibility, strong water solubility, high selective and good detection effect, and prepared in simple manner. DETAILED DESCRIPTION - Cysteine modified graphene quantum dot (GQCY) is represented by formula (I). INDEPENDENT CLAIMS are included for: (1) a method for preparing cysteine modified graphene quantum dot, which involves taking 1.0-3.0 mg/mL graphene quantum dot solution in 100 mL of beaker, adding 0.1-0.25 mL of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and dicyclohexylcarbodiimide mixed solution as catalyst, keeping and activating 10-30 minutes, weighing 0.2 g cysteine, dissolving 10 mL in de-ionized water, stirring to completely dissolve, and then gradually adding to the activated graphene quantum dot solution in water bath at 40 degrees C and ultrasonic dispersing for 10 minutes, heating in water bath at 45-55 degrees C for 5 hours, and then stirring at normal temperature for 24 hours, placing product of molecular weight is 1000 in the dialysis bag in 1000 mL of de-ionized water dialysis for three days, changing water one time at 3 hours to obtain graphene quantum dot GQCY of cysteine modified; and (2) a method for preparing dopamine fluorescence detection reagent, which involves dissolving graphene quantum dot modified by cysteine in water or alcohol aqueous solution to obtain 0.02-2.0 mg/mL histidine fluorescent detection reagent solution.