▎ 摘　　要

NOVELTY - Fluorescence-enhanced graphene quantum dot-rare earth down-conversion fluoride composite material comprises histidine functionalized graphene quantum dot as stabilizer to hydrothermally synthesize rare earth fluoride to make rare earth fluoride. There are a large number of functional groups on the surface of the compound. The fluorescence resonance energy transfer between the graphene quantum dots and the rare earth down-converting fluoride is performed to improve the fluorescence emission intensity of the graphene quantum dots. USE - Fluorescence-enhanced graphene quantum dot-rare earth down-conversion fluoride composite material for fluorescence imaging of tumor cell imaging or cupric concentration in electronic devices, biodetection, and cell imaging (all claimed). ADVANTAGE - The fluorescence-enhanced graphene quantum dot-rare earth down-conversion fluoride composite material has small grain diameter, high crystallinity and is easy to disperse in water, is simple, efficient, green and eco-friendly to prepare. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is inlcuded for a method for preparing fluorescence-enhanced graphene quantum dot-rare earth down-conversion fluoride composite material, which involves: (A) preparing composite precursor, and adopting histidine, formulating functionalized graphene quantum dots into an aqueous solution to adjust the pH to neutral to obtain histidine functionalized graphene quantum dot aqueous solution and using as a stabilizer; (B) adding histidine function to the rare earth ion solution under stirring to form graphene quantum dot aqueous solution to form a graphene quantum dot-rare earth complex dispersion; (C) adding certain amount of sodium fluoride aqueous solution dropwise, or a certain amount of ammonium fluoride and sodium hydroxide/lithium, mixing the aqueous solution to form precursor; (D) heating the precursor at a certain temperature for a period of time; (E) collecting the supernatant, centrifuging at a high speed for a period of time, removing the free graphene quantum dots; and (F) washing the precipitate with water for 2-5 times, freeze-drying to obtain graphene quantum dot-rare earth down-conversion fluoride composite.