▎ 摘　　要

NOVELTY - Preparing graphene hydrogel comprises (i) dissolving graphene oxide in distilled water, stirring at room temperature to fully dissolve it, and obtaining uniform mixed solution; (ii) adding ascorbic acid into the mixed solution, stirring at room temperature, and ultrasonically dispersing to obtain reduced graphene oxide solution; (iii) dissolving the solid sample of dopamine in the tris solution and shaking to obtain buffer solution; (iv) pouring the buffer solution into the reduced graphene oxide solution, and stirring, ultrasonic dispersing at room temperature, and sealing the container; (v) adding the container in a thermostat for heat preservation; and (vi) filtering the solution in step (v), and evaporating the water in the gel. USE - The graphene hydrogel is useful for detecting trace copper ion in copper sulfate solution by linear voltammetry (claimed). ADVANTAGE - The hydrogel has easily available raw materials, mild preparation condition and short preparation time and is environmentally-friendly, low cost and safe, and consumes less energy. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for use of graphene hydrogel, comprising smearing the graphene hydrogel on the platinum carbon electrode, adding into a thermostat to steam away excess water, adsorbing the graphene gel on the platinum carbon electrode without falling off, and forming modified platinum carbon electrode.