▎ 摘　　要

NOVELTY - Preparation of composite quantum dots, involves adding pi -bond graphene quantum dots and sodium lignosulfonate to sodium hydroxide solution, stirring at room temperature for 1-5 hours to obtain a light yellow solution, adjusting pH to neutral using sodium hydroxide solution to obtain a colorless solution, dialyzing using bag of 3500 Da for more than 48 hours to obtain purified composite quantum dot aqueous solution, and freeze-drying the solution. USE - Preparation of composite quantum dots for fluorescence enhancement type probes used for detecting trivalent iron ions in water bodies (all claimed). ADVANTAGE - The method enables simple and easy preparation of composite quantum dots using economical raw materials and wide source of biomass resource, under mild reaction conditions. The obtained quantum dots have high fluorescence intensity.