▎ 摘　　要

NOVELTY - Silver-graphite-coated silica composite upconversion nanocrystals comprise composite fluorescent nanoparticles loaded with metallic silver where surface is coated with graphene connected with rare earth upconversion nanocrystalline silica. The mass ratio of metallic silver and graphene is 1:5-1:10. The surface of the silica is connected with the rare earth upconversion nanocrystals where mass ratio of upconversion nanocrystals and silica is 1:7-1:15. USE - Silver-graphite-coated silica composite upconversion nanocrystals. ADVANTAGE - The method makes up conversion luminescence intensity of rare earth up to 50 times. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for preparation of silver-graphite-coated silica composite upconversion nanocrystals comprising: (A) dissolving graphene oxide in ultrapure water to prepare 0.25-0.35 mg/ml solution, adding silver nitrate and ethylene glycol where mass ratio of graphite oxide, ethylene glycol, and silver nitrate is 0.25:20:0.1-0.35:20:0.15, mixing, heating at 90-100 degrees C for 3-6 hours, centrifuging and washing to obtain silver/graphene mixture; (B) dispersing silver/graphene mixture in ethanol to prepare 20-30 mg/ml dispersion liquid, stirring, mixing, adjusting pH value to 6-8, adding tetraethylorthosilicate, ultrasonically dispersing for 4-9 hours, adding 3-aminopropyl triethoxysilane, stirring for 6-24 hours to obtain amino-modified silica-coated silver/graphene where mass ratio of silver/graphene mixture, tetraethylorthosilicate and 3-aminopropyl triethoxysilane is 20:0.04:0.03-20:0.06:0.04; (C) taking rare earth metal oxide, sodium carbonate and trifluoroacetic acid at mass ratio of 1:1-1:3, dissolving in ultrapure water, mixing at 70-95 degrees C, evaporating to dryness, drying at 80 degrees C to trifluoroacetic acid salt, mixing with oil at volume ratio of 1:20-1:30, heating at 110-120 degrees C under inert atmosphere, heating at 300-330 degrees C for 2-3.5 hours, cooling to room temperature, centrifuging and washing with ethanol and cyclohexane to obtain upconversion nanocrystals; and (D) dissolving upconversion nanocrystals in ethanol, dissolving sodium citrate in ultrapure water where mass ratio of upconversion nanocrystals and sodium citrate is 1:10-1:15, mixing, stirring for 6-12 hours to obtain carboxyl-modified nanocrystalline, mixing carboxyl-modified nanocrystalline and 4-dimethylaminopyridine nanocrystals at ratio of 1:10-1:20, stirring for 12-24 hours, washing and centrifuging.