Synthesis And Magnetic-Optical Coupling Of Core-Shell Magnetic/Luminescent Composite

In recent years, rare earth doped luminescent materials have gained much popularity in material research communities because of its interesting photoluminescence (PL) characteristics and widely applied in a variety of fields ranging from solid-state lasers, optical communication to smart display devices. Therefore, extensive investigation has been conducted on luminescent materials with high PL efficiency. The tunability of luminescence parameters of rare earth ions by means of external magnetic field could open new options for both fundamental research and applications in telecommunications and smart display devices. Herein, the fabrication of magnetic-optical composite with core-shell structure and a strategy for the dependence of the remanent magnetization of the excellent magnetic core on the PL intensity is proposed in the article, as follows:1. The magnetic-optical coupling of core-shell magnetic/luminescent CoFe2O4@YVO4:Eu3+compositeA magnetic optical bi-functional composite CoFe204@YV04:Eu3+with core-shell was synthesized by solvothermal method and sol-gel method. The dependences of the magnetic field with a constant magnetization time of4h and magnetization time with a constant magnetic field of-0.25T, with the increase of the remanent magnetization, the PL peak intensity of the magnetized CoFe2O4@YVO4:Eu3+composite gradually increased and then slightly decreased. After the composite was magnetized under an external magnetic field of0.25T for4h, an enhancement of56%in the PL intensity is observed. The obvious remanent magnetization induced enhancement in photoluminescence technique in developing excellent magnetic/luminescent material for the practical display devices. The effect of magnetic field on the PL intensity of magnetic optical bifunctional composite is a very effective strategy of enhancing PL intensity.2. The magnetic-optical coupling of core-shell-shell magnetic/luminescent CoFe2O4@SiO2@Y2O3:Eu3+compositeMagnetic and luminescent bi-functional composite CoFe2O4@Si02@Y2O3:Eu3+with core-shell-shell structure was fabricated via solvothermal method, sol-gel method and homogeneous precipitation method. Their structure and properties were characterized by XRD, TEM, EDX, SEM, PPMS and luminescence spectra. The composite was magnetized under several different external magnetic field strengths for3h, and the PL intensity gradually increased with increasing magnetic field until it reached0.25T followed by a slight decrease. After the composite was magnetized under an external magnetic field of0.25T for4h, an enhancement of56%in the PL intensity is observed. This method possesses the advantages of noncontact, simple operation and high growth amplitude and has potential for practical display device applications.3. The magnetic-optical coupling of core-shell magnetic/luminescent CoFe2O4@YF3:Yb3+/Er3+compositeSolvothermal method and precipitation method are presented for the fabrication of magnetic and luminescent core-shell CoFe2O4@YF3:Yb3+/Er3+composite. After the core-shell CoFe2O4@YF3:Yb3+/Er3+composite was magnetized under an external magnetic field of-0.2T, a giant enhancement of5.81times in the upconversion luminescence intensity at656nm was experimentally observed. The obvious remanent magnetization induced enhancement in upconversion luminescence is helpful in developing excellent magnetic/luminescent material for the practical display devices.Finally, we provide a discussion and summary of the main points covered. The thesis concludes with recommendation for improving our understanding on magnetic and luminescent bi-functional composite.