Synthesis And Characterization Of Rare-earth Bifunctional Nanocomposites Based On Magnetic/Multicolor Luminescence Properties

Recently,with the rapid development of functional materials,composites with single function have difficult to satisfy the growing demand.Thus,multifunctional composite materials gradually attracted extensive attention.Combining the fluorescent material with magnetic material to prepare nanocomposites with bifunctional properties has become hot researches.In this thesis,the rare earth ions including Eu³⁺,Yb³⁺,Er³⁺,Tb³⁺ doped luminescence materials were served as shells,Fe₃O₄ nanoparticles were used as the core,single doped and co-doped fluorescent-magnetic bifunctional nanocomposites were prepared.The details are as follows:?1?Fe₃O₄ nanoparticles were prepared by precipitation method at 60 °C based on PEG serve as surfactant.The samples have better crystal structure,high purity,spherical morphology with the average particle diameter of 27.5 nm,and superparamagnetic property.?2?Fe₃O₄@SiO₂ composite particles were prepared by Stober method,the samples have better core-shell structure with the average particle diameter of 45 nm.The nanomaterials have the specific surface area of 110 m2/g and small pore size with pore volume of 0.35cm3/g.SiO₂ shell was well coated on the surface of Fe₃O₄ nanoparticles,which result in the decreasing for unit mass of Bohr magneton in Fe₃O₄@SiO₂ composite particles,and then the saturation magnetization was decreased slightly.?3?Fe₃O₄@Si O₂@Y₂O₃:Eu³⁺ bifunctional nanomaterials with magnetic and fluorescent properties were prepared by solvothermal method combining with high temperature calcination.The obtained samples have better crystallinity and obvious core-shell structure with the average particle diameter of 150-200 nm.The materials possess stronger red emission and good magnetic separation characteristics.Simultaneously,the saturation magnetization intensity of the bifunctional nanomaterials was decreased due to the surface coating.?4?Fe₃O₄@NaGdF₄:Yb³⁺,Er³⁺ bifunctional nanomaterials with magnetic and fluorescent properties were prepared by hydrothermal method.The samples have better crystallinity with the average diameter of about 200-300 nm and the shell thickness of 50-100 nm.The Fe₃O₄@NaGdF₄:Yb³⁺,Er³⁺ composite nanomaterials possess stronger green emission peaks?at 543 nm?and the red emission?at 655 nm?.Simultaneously,the samples still have good magnetic properties and magnetic response of the Fe₃O₄ nanoparticles.?5?Fe₃O₄@NaGdF₄:Tb³⁺ bifunctional nanomaterials with magnetic and fluorescent properties were prepared by hydrothermal method.The final samples have a sphere morphology with an average diameter of 180-270 nm.The nanocomposites still possess stronger characteristic green emission of Tb³⁺ deriving from NaGdF₄:Tb³⁺ shell layer and better magnetic properties resulting from the Fe₃O₄ core particles.