▎ 摘　　要

NOVELTY - Use of graphene-cerium dioxide composite material is claimed for detecting tryptophan. USE - Graphene-cerium dioxide composite used for detecting tryptophan and to construct an electro-chemical sensor (all claimed). ADVANTAGE - The graphene-cerium dioxide composite has high sensitivity, and good stability. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) a method for preparing the graphene-cerium dioxide composite material, which involves dispersing graphene oxide and cerium nitrate in de-ionized water, adjusting the pH to alkaline with sodium hydroxide solution, adding hydrazine hydrate, subjecting hydrothermal reaction at 140-180 degrees C for 4-8 hours, cooling, centrifuging, washing, and drying to obtain final product, where the ratio of graphene oxide, cerium nitrate, de-ionized water, and hydrazine hydrate is 2-3 mg:8-11 mg:0.8-1.5 milliliter:1-1.5 micro-liter; and (2) a method for constructing electro-chemical sensor, which involves dispersing graphene-cerium dioxide composite material in ethanol to obtain concentration 1-2 mg/mL of the dispersion, transferring 5-10 micro-liter dispersion to the surface of the glassy carbon electrode, drying to obtain the working electrode, and combining a reference electrode and counter electrode to construct electro-chemical sensor.