▎ 摘　　要

NOVELTY - Conjugated c (RGDfC) sulfur-nitrogen double-doped graphene quantum dot is claimed. The sulfur-nitrogen double-doped graphene quantum dot modified by polypeptide c (RGDfC). USE - The conjugated c (RGDfC) sulfur-nitrogen double-doped graphene quantum dot is useful in preparing anti-tumor drug (claimed). ADVANTAGE - The graphene quantum dot has tumor cell selectivity and can autonomously enter the lysosome and mitochondria of the cell; can overcome the photodynamic therapy resistance produced by the cells during repeated treatments with sulfur and nitrogen doped graphene quantum dot; produces reactive oxygen species to kill tumor cells during repeated treatments; and solves the technical problems that are difficult to solve in the existing process. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: (1) preparing conjugated c (RGDfC) sulfur-nitrogen double-doped graphene quantum dot, comprising either (i) dissolving the sulfur-nitrogen double doped graphene quantum dot in solvent, and adding polypeptide c (RGDfC) for reaction, and (ii) carrying out ultrafiltration of the reaction solution prepared in step (i) to obtain final product, preferably in step (i), the solvent is double distilled water, the reaction temperature is 4-25 degrees C, the reaction time is 2-6 hours, in step (ii), during the ultrafiltration, the molecular weight cut-off of the ultrafiltration tube is 10 kDa, during the ultrafiltration, the centrifugal temperature is 0-4 degrees C, centrifugal force is 5000-10000 g, and centrifugal time is 5-10 minutes, preferably in step (i), the reaction temperature is 4 degrees C, the reaction time is 4 hours, in step (ii), during the ultrafiltration, the centrifugal temperature is 4 degrees C, the centrifugal force is 10000 g, and the centrifugal time is 6 minutes, or (a) dissolving sulfur-nitrogen double-doped graphene quantum dot in solvent, and adding 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxysuccinimide mixture for activation, (b) adding polypeptide c (RGDfC) into activated sulfur-nitrogen double-doped graphene quantum dot, and (c) ultra-filtering the reaction solution prepared in step (v) to obtain final product; and (2) use of the conjugated c(RGDfC) sulfur-nitrogen double-doped graphene quantum dot in preparing anti-tumor drug, preferably the anti-tumor drug is photosensitizer including photosensitizer that targets tumors and overcomes resistance to photodynamic therapy.