▎ 摘　　要

NOVELTY - A nitrogen-doped graphene composite material preparing method involves weighing copper(I) chloride and thiourea, dispersing in a mixed solvent of water and N,N-dimethylformamide, and pouring into the reaction kettle, carrying out the reaction, cooling to room temperature, washing and centrifuging to obtain a copper sulfide product, weighing nitrogen-doped graphene, dispersing in water, and supersonically oscillating dispersed nitrogen-doped graphene dispersion, taking palladium(II) chloride solid powder and dissolving in water to obtain palladium(II) chloride solution, ultrasonically dispersing sodium borohydride in water to obtain a sodium borohydride solution, mixing the copper sulfide product with a palladium(II) chloride solution, and ultrasonically oscillating, adding sodium borohydride solution and the nitrogen-doped graphene dispersion, adding sodium borohydride solution and the nitrogen-doped graphene dispersion dropwise, after washing and drying to obtain the finished product. USE - Method for preparing nitrogen-doped graphene composite material for detecting xanthine content in blood serum (claimed). ADVANTAGE - The method enables preparing nitrogen-doped graphene composite material with high sensitivity and wide linear range. DETAILED DESCRIPTION - A nitrogen-doped graphene composite material preparing method involves weighing 250-70 mg copper(I) chloride and 60-80 mg thiourea, dispersing in a mixed solvent of 3-8 mL water and 10-20 mL N,N-dimethylformamide, stirring for 30-60 minutes, and pouring into the reaction kettle, carrying out the reaction at 150-180 degrees C for 4-8 hours, cooling to room temperature, washing, and centrifuging to obtain a copper sulfide product, weighing 3-6 mg nitrogen-doped graphene, dispersing in 3-6 mL water, and ultrasonic oscillating for 1-3 hours until uniformly dispersed nitrogen-doped graphene dispersion, taking 1.5-2.5 mg palladium(II) chloride solid powder and dissolving it in 0.8-1.2 mL water to obtain palladium(II) chloride solution, ultrasonically dispersing 8-12 mg sodium borohydride in 0.8-1.2 mL water to obtain a sodium borohydride solution, mixing the copper sulfide product with a palladium(II) chloride solution, and ultrasonically oscillating to uniformly disperse a mixture of copper sulfide and palladium(II) chloride, adding sodium borohydride solution and the nitrogen-doped graphene dispersion to the mixture of copper sulfide and palladium(II) chloride under stirring, adding sodium borohydride solution and the nitrogen-doped graphene dispersion dropwise for 20-40 minutes, and completing the mixing, allowing to stand for 30-100 minutes, after washing and drying to obtain the finished product. An INDEPENDENT CLAIM is also included for a nitrogen-doped graphene composite material prepared by the method.