Synthesis And Photoluminescence Properties Of Rare Earth Compounds Hollow Structures

As a consequence of the unique properties including low density, high specific surface area, and good permeability, compared with bulk material, hollow spheres have potential applications in many a application territories such as: drug delivery, catalysis carriers, electrochemical cells, active-materials protection and the release of proteins and enzymes. Therefore, a considerable amount of research has been focused on the exploration of different methods to synthesize these hollow structures. Among all the methods, template directing is the most direct and effective way.Due to the unique 4f valence shell electron character of their ions and the numerous transition modes of the 4f shells of ions, rare earth (RE) compounds were endowed with superior electronic, optical and magnetic properties. The synthesis and application research of rare earth compounds nano-materials becomes a attractive research area. Recently, various methods have been developed to fabricate rare earth compounds nano-structures with different morphologies. However, this strategy often suffers from many disadvantages including high cost and complicated procedures, which is unfavorable for the large scale producing and application.In this paper we have synthesised various rare earth compound hollow structure such as oxides, fluorides and phosphates of RE via template method.(1) The synthesis of nano-sized Y₂O₃: Eu³⁺ hollow spheres with enhanced photoluminescence properties via solvethermal method. In the synthesis, ethanol and water (4/3 volume ratio) acted as solvents, urea was used as precipator. The as-prepared precursor was annealed in air to generate Y₂O₃:Eu³⁺ novel hollow structures. Moreover, the growth process of these hollow spheres and their luminescence properties were also intensively studied by adjusting experiment parameters such as reaction temperature, the ratio of solvents, and the kind of precipitators. The precursor was formed without any surfactant and additional template. It was demonstrated gas bubbles were acted as soft templates for the synthesis of hollow structures. Additionally, the influence of doping concentration and calcination temperature on the photoluminescence property of Y₂O₃:Eu³⁺ was also intensively investigated.(2) Synthesis of Y₂O₃:Eu³⁺ hollow spheres via using MF spheres as hard template. The size-controlled MF spheres are of high uniform and can be easily obtained by polymerizing at low temperature. Then, the core/shell precursor was obtained through precipitating using melamine formaldehyde (MF) spheres as template. After the remolval of MF by calcination, Y₂O₃:Eu³⁺ hollow spheres were formed. Additionally, Y₂O₃:Eu³⁺ hollow spheres with different shell thickness can be obtained by adjusting the dosage of MF spheres, and the relation between photoluminescence properties and shell thickness was studied.(3) The synthesis of nano-sized EuF₃ hollow spheres via chemical conversion (self-templating) at low temperature. The EuOHCO₃ precursors were prepared by a solvethermal method and subsequently EuF₃ hollow spheres were formed through ion-exchange reaction between. The possible growth mechanism for the nano-sized hollow sphere was proposed and the photoluminescence (PL) properties of as-prepared EuF₃ products were also intensively studied. This route can be served as a general method to synthesis other rare earth compounds hollow structures.(4) A facile synthesis of GdPO4:Eu³⁺ hierarchical hollow spheres via chemical conversion(self-templating). Based on the time-dependent experiments, the mechanism of hollow shells were proposed. Furthermore, the current method can serve as a general way for the synthesis of other rare earth phosphates hollow spheres.