▎ 摘　　要

NOVELTY - Preparing a nano-spherical silver sulfide highly dispersed and loaded nitrogen-doped graphene composite material comprises e.g. providing 0.8-1.2 mmol silver nitrate and 1.5-2.5 mmol of S powder, dissolving in 4-8 ml organic solvent (ethylene glycol) to obtain silver nitrate solution and sulfur powder solution, dropping the solution into the sulfur powder solution, adding 0.4-0.6 g of polyvinylpyrrolidone, after the PVP is completely dispersed and dissolved, transferring the solution to the reaction kettle, reacting at 150-180 degrees C for 4-6 hours, centrifuging and washing to obtain nano-spherical silver sulfide product, and taking 4-6 mg nano spherical silver sulfide into 4-6 ml organic solvent (N, N-dimethylformamide), dispersing by ultrasonication for 20-40 minutes to form A dispersion, taking 4-6 mg nitrogen-doped graphene, adding to 4-6 ml organic solvent (N, N-dimethylformamide). USE - The composite modified electrode/graphene composite material is useful for the determination of isoquercitrin content (claimed) in Chinese medicinal materials. ADVANTAGE - The composite modified electrode/graphene composite material has wide detection range, high sensitivity and easy operation. DETAILED DESCRIPTION - Preparing a nano-spherical silver sulfide highly dispersed and loaded nitrogen-doped graphene composite material comprises (1) providing 0.8-1.2 mmol silver nitrate and 1.5-2.5 mmol of S powder, dissolving in 4-8 ml organic solvent (ethylene glycol) to obtain silver nitrate solution and sulfur powder solution, dropping the solution into the sulfur powder solution, adding 0.4-0.6 g of polyvinylpyrrolidone, after the PVP is completely dispersed and dissolved, transferring the solution to the reaction kettle, reacting at 150-180 degrees C for 4-6 hours, centrifuging and washing to obtain nano-spherical silver sulfide product, and (2) taking 4-6 mg nano spherical silver sulfide into 4-6 ml organic solvent (N, N-dimethylformamide), dispersing by ultrasonication for 20-40 minutes to form A dispersion, taking 4-6 mg nitrogen-doped graphene, adding to 4-6 ml organic solvent (N, N-dimethylformamide), dispersing by ultrasonication for 20-40 minutes to form B dispersion, after mixing the two dispersions of A and B, sonicating for 40-80 minutes, after centrifugation and drying nano-spherical silver sulfide highly dispersed and loading nitrogen-doped graphene composite material. INDEPENDENT CLAIMS are also included for: (1) nano-spherical silver sulfide highly dispersed and loaded nitrogen-doped graphene composite material; (2) nano-spherical silver sulfide highly dispersed loaded nitrogen-doped graphene composite modified electrode comprising nano-spherical silver sulfide highly dispersed and loaded nitrogen-doped graphene composite material; (3) preparing nano-spherical silver sulfide highly dispersed and loaded nitrogen-doped graphene composite modified electrode comprising ultrasonically dispersing nano-spherical silver sulfide highly dispersed and loaded nitrogen-doped graphene composite material in an organic solvent to obtain an electrode modification solution, taking the electrode modification drop, adding on the surface of the glassy carbon electrode, after drying to obtain the nano-spherical silver sulfide highly dispersed and loaded nitrogen-doped graphene composite modified electrode; and (4) use method of modified electrode for determination of isoquercitrin content comprising using differential pulse voltammetry for measurement, using three-electrode system comprises a nano-spherical silver sulfide highly dispersed nitrogen-doped graphene composite modified electrode as a working electrode, a platinum electrode as a counter electrode, and a saturated calomel electrode as a reference electrode, connecting the three-electrode system to the electrochemical workstation, configuring the standard solution and the actual sample to be measured, using differential pulse voltammetry to determine the oxidation peak current of the standard solution is a linear equation, among them, in the concentration range of 1.0 -20.0 mu mol / l, the linear equations are: ip = 0.8143c + 9.4334x 106 (R2 = 0.9857), in the concentration range of 20.0-400.0 mu mol/l, ip = 0.05775c + 2.4450x 105 (R2 = 0.9976), in the equation, c is the concentration of isoquercitrin, and the unit is mol/l, ip is the differential pulse voltammetry obtained isoquercitrin oxidation peak current value, the unit is A, using differential pulse voltammetry to determine the peak current value of isoquercitrin in the test solution of the actual sample, calculating concentration of isoquercitrin to the linear equation, and obtaining the content of isoquercitrin in the actual sample.