Rare Earth Doped Lu₂O₃, Gd₂O₃and Gd₂O₂S Hollow/Core-shell Microspheres: Preparation And Luminescence Properties

It is well known that the properties of the nano/micro materials closely interrelatewith geometrical factors such as shape, dimensionality and size. With theadvancement of modern chemistry and materials science, nano/micro structures withwell-defined morphologies and tunable sizes have attracted extensive interest due totheir potential applications in a wide range of fields. By experiments and studies,many different kinds of new nano/micro structures have been prepared recently. Forinstance, nanoparticles, nanobelts, nanoplates, nanotubes, nanoflowers, microspheresand hollow microspheres have been achieved successfully via various methods. Thesenano/micro materials with special morphologies have better performances and can beapplied potentially in various fields such as electrochemical catalysis, photonicdevices and biotechnology. This thesis mainly reports the preparation of rare earthoxysulfide hollow spheres and rare earth oxides core-shell microspheres bysolvothermal method. Specific research results are as follows:1. Highly monodisperse and homogeneous Gd₂O₂S:Eu³⁺and Gd₂O₂S:Eu³⁺/Gd₂O₂Shollow microspheres were synthesized successfully by the template method andrecoating process. The results show that the Gd₂O₂S:Eu³⁺and Gd₂O₂S:Eu³⁺/Gd₂O₂Shollow microspheres are of pure hexagonal phase of Gd₂O₂S, with diameters ofaround260and300nm, respectively. Meanwhile, the DRS result ofGd₂O₂S:Eu³⁺/Gd₂O₂S hollow microspheres exhibits that the absorption edgeapparently shifts to blue in comparison with that of the Gd₂O₂S:Eu³⁺hollowmicrospheres. Upon325nm excitation, the phosphors exhibit red emissioncorresponding to the5D0â†'7F2transition of the Eu³⁺ions, and Gd₂O₂S:Eu³⁺/Gd₂O₂Shollow spheres show a higher luminous intensity than Gd₂O₂S:Eu³⁺. Theenhancement mechanism was investigated in detail, indicating that the recoatingprocess on luminescent particles may greatly improve the luminous intensity. 2. Homogeneous and monodisperse Gd₂O₃:Eu³⁺core-shell mirospheres have beensuccessfully synthesized via a solvothermal method with polyvinylpyrrolidone （PVP）as surfactant, followed by a subsequent calcination process. The results show that theobtained Gd₂O₃:Eu³⁺mirospheres with a core-shell structure are uniform in size anddistribution, and they have diameters of³50nm，the core diameters of¹50nm, andthe shell thicknesses of⁴5nm. Under ultraviolet （UV） excitation, the correspondingGd₂O₃:Eu³⁺products exhibit strong red emission corresponding to the5D0-7F2transition of the Eu³⁺ions, which might find potential applications in the fields suchas light-emitting phosphors, advanced flat panel displays, or biological labeling.3. Highly monodisperse and homogeneous Lu₂O₃: Ln (Ln=Yb³⁺/Er³⁺, Yb³⁺/Ho³⁺)hollow microspheres were synthesized successfully by the template method andsolvethermal process. The up-conversion luminescence properties of the hollowmicrospheres have been discussed in detail.