▎ 摘　　要

NOVELTY - A pH sensitive response N,S-doped graphene quantum dot is prepared by heating and melting carbon source compound, nitrogen-containing compound and nitrogen and sulfur source compound, adding other nitrogen source compound, naturally cooling, adding acetone solution, precipitating to white precipitate, centrifuging to obtain white precipitate, and dialyzing using dialysis membrane with interception molecular weight of 2000 Da. USE - Method for preparing pH sensitive response N,S-doped graphene quantum dot (claimed). ADVANTAGE - The method is simple, has low cost, high yield and little impurity, and uses common material source. The dot has stable structure, excellent fluorescence property, good linearity at pH of 3-9 and urease activity detection limit reaching 2.5 U/L, measures fluorescence intensity change of detection for urease activity, and hydrolyzes urea by urease to generate hydroxide ion and ammonium cation to increase pH value of the whole solution system. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for detecting urease activity by fluorescence spectrophotometry for detecting urease concentration comprising mixing using solvent, urea and pH sensitive response N,S-doped graphene quantum dot.