▎ 摘　　要

NOVELTY - Method for preparing a carboxyl-modified functionalized graphene quantum dot involves (1) adding graphite and sodium nitrate into a strong acid, stirring for 3-5 hours in an ice bath, slowly adding a strong oxidizing agent, maintaining stirring, adding deionized water, heating, refluxing, cooling, adding 30(wt./vol.)% hydrogen peroxide and filtering to obtain graphene oxide, washing the filter cake with hydrochloric acid and deionized water and drying the filter cake and obtaining graphene oxide, (2) dispersing the prepared graphene oxide in water, mixing with a nitrogen-containing reagent to obtain a mixed solution, performing an ultrasonic dispersion treatment, transferring transferred to a high-pressure kettle lined with polytetrafluoroethylene, heating, filtering the black precipitate, dialyzing and freeze-drying and (3) dispersing, adding organic acid, ultrasonically treating for 2-4 hours, removing 60% water by vacuum distillation and filtering by ultracentrifugation. USE - The method is useful for preparing a carboxyl-modified functionalized graphene quantum dot used in a detection of cardiac troponin I (claimed). ADVANTAGE - The method adopts simple process, provides excellent stability and high fluorescence intensity and has the prospect of being applied to the detection of cardiac troponin I. DETAILED DESCRIPTION - Method for preparing a carboxyl-modified functionalized graphene quantum dot involves (1) adding graphite and sodium nitrate into a strong acid, stirring for 3-5 hours in an ice bath, slowly adding a strong oxidizing agent, maintaining stirring at 20-30 degrees C for 0.5-1.5 hours, adding deionized water, heating at 30-40 degrees C for 0.5-1.5 hours, heating at 80-100 degrees C after preserving heat, refluxing for 1-3 hours, cooling to 25 degrees C, adding 30(wt./vol.)% hydrogen peroxide and filtering to obtain graphene oxide, washing the filter cake with hydrochloric acid and deionized water, respectively and drying the filter cake and obtaining graphene oxide, (2) dispersing the prepared graphene oxide in water to obtain an aqueous dispersion, mixing the aqueous dispersion of graphene oxide with a nitrogen-containing reagent to obtain a mixed solution, performing an ultrasonic dispersion treatment, transferring transferred to a high-pressure kettle lined with polytetrafluoroethylene, heating at 180-200 degrees C, preserving heat for 5-10 hours, cooling to 20-30 degrees C after the reaction, filtering the black precipitate, putting the supernatant in a 1000 Da dialysis bag, dialyzing with deionized water for 2 days, and freeze-drying the obtained light yellow solution to obtain light yellow N-doped graphene quantum dot powder and (3) dispersing the N-doped graphene quantum dot powder into deionized water, adding organic acid, ultrasonically treating for 2-4 hours, removing 60% water by vacuum distillation and filtering by ultracentrifugation. INDEPENDENT CLAIMS are included for the following: the carboxyl-modified functionalized graphene quantum dot prepared by the method.