▎ 摘　　要

NOVELTY - Multi-fluorescent nitrogen-doped graphene quantum dots, is claimed. The multi-fluorescent nitrogen-doped graphene quantum dots are graphene quantum dots having hydroxy groups and amino groups on the surface obtained by modifying semicarbazide. USE - The multi-fluorescent nitrogen-doped graphene quantum dots are useful in selective determination of iron ions in solution (claimed). ADVANTAGE - The quantum dots: have uniform particle size; and emits blue, green, and red fluorescence in aqueous solution. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are is also included for: (1) preparing multi-fluorescent nitrogen-doped graphene quantum dots, comprising (i) performing electrolysis by taking graphite rods are as cathode and anode, and mixed solution of alkaline aqueous solution and semicarbazide is as electrolyte, and continuing electrolysis until the reaction is full after the surface layer of the graphite rod expands, and (ii) centrifuging the electrolytic solution after electrolysis to obtain solid powder, and separating and purifying the obtained solid powder to obtain multi-fluorescent nitrogen-doped graphene quantum dots; (2) use of multi-fluorescent nitrogen-doped graphene quantum dots in selective determination of iron ions in solution; and (3) use method comprises dissolving multi-fluorescent nitrogen-doped graphene quantum dots in deionized water to prepare aqueous solutions of graphene quantum dots having different concentrations and taking equal volumes of prepared different metal ion solutions having same concentration in the same amount of aqueous solution of graphene quantum dots.