Preparation Of Rare Earth NaYF₄/CaF₂Nanocrystalline And The Research On Upconversion Fluoreascence Property

For the past few years, rare-earth upconversion luminescence nanometermaterials have been widely applied in the fields of solar cells, integrated optics,biomedical imaging systems and so forth due to the excellent optical performance.Since nanoscal materials are seriously affected by the surface defects, however, alayer of shell material should be wrapped on the nanocrystalline surface, in order toimprove the surface performance, and improve the fluorescence efficiency. Thearticle prepares rare-earth upconversion luminescence nanometer materials ofdifferent doping conditions with hydrothermal method. Then wraps shell on itssurface by the method of pyrolysis, and gets the nanocrystalline of core/shellstructure, furthermore, the upconversion fluoresencence properties are studied.The process of hydrothermal method is studied in this paper. The effects tonanocrystal particle sizes of oleic acid and water proportions in the hydrothermalprocess are explored. Thus, the conclusion is reached that in the hydrothermalprocess, as the oleic acid increases gradually, the synthetic nanocrystalline particlesizes become smaller. As a result, the optimum synthetizing plan of nanometercrystal nucleus is determined, What is more, nanocrystals of NaYF₄:20%Yb,2%Er,NaYF₄:20%Yb,2%Tm and NaYF₄:20%Yb,2%Ho are prepared by hydrothermalmethod respectively, and the morphology of which are tested. and nano-sized NaYF₄crystal nucleus of different doping conditions are prepared.A shell of CaF₂is wrapped on the surface of the crystal nucleus prepared by themethod of thermal cracking, as a result, the core/shell structure is obtained.Furthermore, the upconversion fluorescence of which is tested using980nmsemiconductor laser as the excitation light source. Upconversion luminescencemechanism of rare earth ions in nanocrystals under different doped conditions areanalyzed. Morphology of the nanocrystalline is tested by TEM, and theenhancement potentiation of the core-shell structure to the luminous efficiencies ofrare earth doped upconversion fluorescence materials are discussed.