▎ 摘　　要

NOVELTY - Preparation of graphene quantum dots involves mixing graphene powder and a mixed acid containing concentrated sulfuric acid and auxiliary acid, oxidizing to obtain a mixed solution containing a reaction intermediate, ultrasonically treating, calcining in a heating vessel having an exhaust gas recovery device to obtain a graphene quantum dot crude product, dispersing in distilled water, filtering through a microporous membrane and dialyzing by a dialysis bag. USE - Preparation of graphene quantum dots for preparing graphene quantum dot probe used in phosphate quantitative assay method. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) preparation of graphene quantum dot probe, which involves mixing europium nitrate and graphene quantum dots in molar ratio of 50:1-1:50; and (2) phosphate quantitative assay method, which involves mixing graphene quantum dot probe solution with standard phosphate solution, adding tris(hydroxymethyl) aminomethane hydrochloride buffer solution, measuring final concentration of phosphate ions as 0.6x 10-6 mol/L, 3x 10-5 mol/L, 6x 10-5 mol/L, 3x 10-4 mol/L and 4x 10-4 mol/L, measuring fluorescence intensity of each standard solution, plotting standard curve of phosphate ion concentration-fluorescence intensity, and calculating linear equation of phosphate ion concentration and fluorescence intensity.