Synthesis,Properties And Applications Of Luminescent Materials With Mn²⁺ Ions And Defects As Emission Centers

Luminescent materials play an important role in people’s daily lives.After a long period of development,luminescent materials have been widely used in lighting,displays,optoelectronic devices,bioimaging,fluorescent labeling,and so on.In this dissertation,we have fabricated two kinds of inorganic solid luminescent materials by simple and feasible methods:transition metal Mn²⁺doped phosphors and silica-based defect-related luminescent materials.The phase,structure,morphology,and luminescent properties of the as-synthesized materials have been also investigated in detail.A variety of uniform and well-dispersed one-dimensional Zn₂GeO₄:Mn²⁺phosphors have been synthesized via a facile solvothermal process with H₂O/EG as solvent.During the synthesis process,the component of solvent and the addition of PEG surfactant play an important role in determining the structure,particle size,and morphology of the final product.Under ultraviolet light excitation,the pure Zn₂GeO₄ sample shows bluish-white emission which is attributed to the native defects present in the Zn₂GeO₄ host.When Zn²⁺ions are partially substituted by Mn²⁺,the as-synthesized Zn₂GeO₄:Mn²⁺samples exhibit intense green emission that corresponds to the d-d transition（⁴T₁→⁶A₁）of Mn²⁺ions.The luminescence mechanisms of the Zn₂GeO₄:Mn²⁺samples were investigated in detail by using the CASTEP code based on density functional theory（DFT）.It is expected that the as-synthesized Zn₂GeO₄:Mn²⁺phosphors can be potentially applied in lighting,optical displays,and optoelectronic devices.Defecte-related luminescent and mesoporous silica hollow spheres with a size of about300 nm have been prepared by sol-gel and alkaline etching methods.Under UV excitation,the sample exhibits strong blue light emission.The as-prepared materials can be used as the drug carrier due to their obvious mesoporous structure,high specific surface area and good biocompatibility.The pH responsive drug delivery system can be obtained by combining the silica hollow spheres and ZnO nanoparticle that are soluble under acidic conditions as the mesoporous"switches"viaEDC chemical reaction.It can be found that the luminescent intensity increases gradually with theaccumulative release of drug（DOX）,indicating that the release process can be monitored and tracked by the change of luminescent intensity of the system.The as-synthesized luminescent silica hollow spheres may find potential applications in fields of drug delivery and disease diagnosis.