▎ 摘　　要

NOVELTY - A biomass-based high-efficiency fluorescent graphene quantum dot comprises composite carbon source, nitrogen source, polyvalent metal ion, and water. USE - Biomass-based high-efficiency fluorescent graphene quantum dot. ADVANTAGE - The quantum dot has high yield is high and simple preparation method. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for preparation of the quantum dot comprising mixing composite carbon source, nitrogen source and water, stirring, adding polyvalent metal ion, heating, subjecting to dialysis, and purifying.