The Preparation Of Hollow And Mesoporous Structure Of Rare-earth Fluoride And The Research Of Optical Properties

Because of the special f-orbital configurations, rare-earth luminescence materials canexhibit sharp fluorescent emissions via intra-4f or4f-5d transitions, and the luminousperformance is very excellent. Hence, they are very suitable for downconversion orupconversion materials due to the low phonon energy, large diffraction index, high physicaland chemical stability. In recent years, nano/micro-rera-earth materials with unique structureshave attracted more and more attention. And the most popular structures should be the hollowstructures and mesoporous structures. Compared with the solid structures, hollow andmesoporous structures possess some outstanding properties, such as low density, goodpermeability, large specific surface area, and high surface activity. Therefore, luminescentproperties, electrical properties, magnetic propertys and light catalytic performance of thematerials can be improved easily, only by surface modification and functional molecularassembly, resulting more extensive applications.Hard-template method is a good choice to prepare hollow strutures. In this paper, wesynthesized monodisperse hollow rare-earth fluorides NaYF₄:18%Yb,2%Er by using MF（melamine formaldehyde） colloidal particles as hard template. Firstly, a layer ofY_0.8Yb0.18Er_0.02（OH）CO₃was coated on the surface of MF microsphere by coprecipitationmethod. Then the outer layer of Y_0.8Yb0.18Er_0.02（OH）CO₃was converted intoNaYF₄:18%Yb,2%Er shell through a solvothermal method. At the same time, the MFmicrospheres will be dissolved without a post-removing treatment. Through the control ofreaction temperature and solvent volume, we have investigated the formation mechanism ofthe hollow rera-earth structures. Moreover, the up-conversion luminescence properties anddrug release performance of hollow NaYF₄:18%Yb,2%Er have been studied. Need to mention,the hollow structure can be obtained without a MF removing process. So the method haspotential applications as a convenient method in fabricating rare earth fluoride or other hollowstructures. Based on the fluorescence properties and hollow structure of the as-preparedmaterials, they hold important applications in the fields of luminescence, biology, andcatalysis.In addition, mesoporous rare-earth fluorides of Na_xGd_yF_x+3yhave been prapared by aself-template method. On the one hand, we synthesized a series of mesoporous structured Na_xGd_yF_x+3ysuccessfully for the first time by employing Gd（OH）CO₃nanosphere asself-template. On the other hand, the formation mechanism of the mesoporous structure havebeen studied through the adjustment of different reaction time, reaction temperature, kindsand dosage of reactants. Meanwhile, we investigated the luminous performance of theproducts with different rare-earth doping amount. The method is an accurate process tocontrol the synthesis of mesoporous rare earth fluorides. As a result, the method alsopossesses important potential application in luminous, biogogic and catalytic fields.