Synthesis And Properties Of NaYF₄:Yb³⁺,Er³⁺@SiO₂ Upconversion Fluorescence Nanocapsules

Rare earth doped upconversion nanocrystals with excellent optical properties,has shown significant potential in biological tag,cellular imaging and photon dynamics treatment of biomedical fields.Generally,the common synthesized upconversion fluorescent nanocrystals were usually modified with long alkyl chain molecules.by most synthetic methods,so the products is hydrophobic,which limits its application in organisms in aqueous environments.Therefore,pursuing suitable methods for the synthesis of high fluorescence efficiency,water solubility and biocompatibility of upconversion fluorescent nanoparticles materials is an urgent problem to be solved in the fields of materials science and biomedical.To solve the above problems,hexagonal phase NaYF4:Yb3+,Er3+ upconveision fluorescent nanocrystals were controlled synthesized by high boiling temperature organic phase synthesis strategy.Then through the soft template method,using self-assembly process of F127 segmented copolymer,the hydrophobic surface of upconversion fluorescent nanocrystals were modified to water solubility.In this way,the water solubility and biocompatibility of NaYF4:Yb3+,Er3+ upconversion fluorescent nanocrystals were enhanced,and the optical properties of it were not affected at the same time.Major research results listed as following:(1)Pure hexagonal phase NaYF4+:Yb3+,Er3+ upconveision nanocrystals were successfully synthesized by high boiling temperature organic phase synthesis strategy.The effects on morphologies,sizes,crystal structure and optical properties of NaYF4:Tb3+,Er3+ nanocrystals were studied by modifying the reaction temperature.Research shows that,When the temperature is higher than 310 ?,the synthesis of NaYF4:Yb3+,Er3+ upconversion fluorescent nanocrystals are pure hexagonal phase;(2)The effects of Yb3+ and Er3+ concentration on morphology and optical properties of hexagonal phase NaYF4:Ybo3+,Er3+ upconveision nanocrystals were studied.The results show that the fluorescence intensity of the pure hexagonal phase NaYF4:Yb+3,Er3+ nanocrystals was 47 times stronger than that of cubic phase nanocrystals in this work.When the concentration of Yb3+ and Er3+ are 20%and 2%,the fluorescence intensity is strongest;(3)The silica coated NaYF4:Yb3+,Er3+ upconversion nanoparticles by a soft template method,to form NaYF4:Yb3+,Er3+@SiO2 upconveision fluorescence nanocapsule.The optical properties of NaYr4:Yb3+,Er3+@SiO2 upconveision fluorescence nanocapsule and load factor of SiO2 capsule were studied by varied the quality of F127-COOH and upconversion nanoparticles.Research show that,when the ratio of F127-COOH and upconversion nanoparticles is 10:2,the fluorescence intensity is strongest,and the optimum loading rate of capsule is 10:6.