▎ 摘　　要

NOVELTY - Preparing nitrogen-doped graphene composite material loaded with silver-copper sulfide core-shell microspheres involves weighing 0.3-0.5 millimole copper chloride dihydrate and 0.8-1.2 millimole of thiourea, adding 7-8 mL of deionized water and 7-8 mL of N,N-dimethylformamide, and stirring for 30-60 minutes, transferring the mixed solution to the hydrothermal reactor, placing the reactor in an oven at 160-180 degrees C for 5-8 hours, and waiting for the reaction to complete separation and wash the product to obtain CuS microspheres, dispersing the obtained copper sulfide microspheres in 4-6 mL of water. USE - Method for preparing nitrogen-doped graphene composite material loaded with silver-copper sulfide core-shell microspheres used for detecting tyrosine content in food (claimed). ADVANTAGE - The method enables to prepare nitrogen-doped graphene composite material loaded with silver-copper sulfide core-shell microspheres has low detection limit, and good stability, in simple manner. DETAILED DESCRIPTION - Preparing nitrogen-doped graphene composite material loaded with silver-copper sulfide core-shell microspheres involves weighing 0.3-0.5 millimole copper chloride dihydrate and 0.8-1.2 millimole of thiourea, adding 7-8 mL of deionized water and 7-8 mL of N,N-dimethylformamide, and stirring for 30-60 minutes, transferring the mixed solution to the hydrothermal reactor, placing the reactor in an oven at 160-180 degrees C for 5-8 hours, and waiting for the reaction to complete separation and wash the product to obtain CuS microspheres, dispersing the obtained copper sulfide microspheres in 4-6 mL of water, adding 0.7-0.8 g of glucose under stirring conditions to obtain copper sulfide microsphere dispersion liquid, dissolving 0.08-0.12g silver nitrate in 0.8-1.2mL water, adding 0.5-0.6 mole/Litre ammonia solution until the precipitation disappears is the silver ammonia solution. The prepared silver ammonia solution is added dropwise to the copper sulfide microsphere dispersion liquid, stirred for 30-60 minutes, and allowed to stand for 70-100 minutes, then the product is separated and washed to obtain silver-copper sulfide core-shell microspheres, taken 0.4-0.6 mg Ag-CuS core-shell microspheres and added to 4-6mL N,N-dimethylformamide with a dispersed concentration of 0.8-1.2 mg/mL nitrogen-doped graphene, subjected to ultrasonic treatment for 50-80 minutes, the nitrogen-doped graphene composite material loaded with Ag-CuS core-shell microspheres is obtained after centrifugal drying. An INDEPENDENT CLAIM is included for a method for using a nitrogen-doped graphene composite material loaded with silver-copper sulfide core-shell microspheres, which involves: (A) using differential pulse voltammetry for the detection, nitrogen doping supported by the Ag-CuS core-shell microspheres, where the hetero-graphene composite material modified electrode is a working electrode, the platinum electrode is a counter electrode, and the saturated calomel electrode electrode is a reference electrode to form a three-electrode system, and the three-electrode system is assembled and connected to an electrochemical workstation to form an electrochemical detection device; and (B) preparing the standard solution and the actual sample solution to be measured, using differential pulse voltammetry to determine the tyrosine oxidation peak current value in different standard solutions, and obtain a linear equation based on the relationship between the tyrosine oxidation peak current value and its concentration, measuring amperometric peak current value of tyrosine in the actual sample solution determined by the method, the tyrosine concentration is converted according to the obtained linear equation, and then the tyrosine content in the actual sample to be measured is obtained, where the linear equation in the range of 0.3-300 micromole/L is: ip is 0.0183c+1.9233 x 10-7 (R2 is 0.9927), and the linear equation in the range of 300-4000 micrommole/L is: ip is 0.00348c+3.640 10- 6(R2=0.9898), the linear equation in the range of 4000-7000 micromole/L is: ip is 0.01124c+2.581 x 10-5(R2 is 0.9855); in the equation, c is the concentration of tyrosine, and the unit is mole/L. The ip is the oxidation peak current value obtained by differential pulse voltammetry, the unit is A, the detection conditions of the differentialpulse voltammetry are the pH value of the detection bottom solution is 3.96, the enrichment time is 60s, and the potential increase is 4mV, amplitude 50mV, primary pulse width 0.2 seconds, secondary pulse width 0.05 seconds, sample width 0.0167 seconds, and pulse period 0.5 seconds.