Synthesis And Characterization Of Lanthanide-based Organic-inorganic Hybrid Nano-phosphors

Lanthanide complexes are a class of useful luminophores because they exhibit high quantum efficiency, sharp and intense emission lines, long life-times and high color purity under ultraviolet excitation, through protecting metal ions from vibrational quenching and increasing light absorption cross section by the well-known "antenna effect". However, they have not so far been used extensively in practical applications as phosphor devices mainly due to their poor thermal stabilities and low mechanical strength. Many lanthanide complexes have been incorporated into solid matrices, such as sol-gel-derived hybrid materials and mesoporous silica materials. Incorporation of lanthanide complexes into these matrices has not only improved the photo and thermal stabilities of the complexes, but also avoided the self-quenching resulting from the concentration effect. In this thesis, our research is focused on the synthesis of lanthanide-based organic-inorganic hybrid nano-phosphors, and the hybrid solid matrices include mesoporous silica nanoparticles, organic-inorganic hybrid colloidal particles, rare earth oxide nanoparticles and nanoporous zeolite-like metal-organic frameworks (ZMOFs).1. Lanthanide(â…¢) (Eu and Tb)-imidazoledicarboxylic acid complexes were immobilized on colloidal mesoporous silica with diameter smaller than 100nm by covalent bond grafting technique and uniform and monodisperse luminescent Eu-idc-Si and Tb-bidc-Si functionalized mesoporous silica hybrid nano-materials (MSNs) were obtained. The lanthanide(â…¢) complexes-functionalized MSNs were characterized by fluorescence spectra, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption, and powder X-ray diffraction. The hybrid nano-materials Eu-idc-Si and Tb-bidc-Si functionalized MSNs show strong red and green photoluminescence upon irradiation with ultraviolet light, respectively. Both hybrid nano-materials exhibit long life-times. The mesoporous silica nanoparticles are stable colloid and may have some advantages for potential applications in drug delivery or optical imaging.2. We chose dipicolinic acid as a tridentate chelating units featuring ONO donors reacting with lanthanide(â…¢) ions to yield tight and protective N3O6 environments around the lanthanide(â…¢) ions, and immobilized lanthanide(â…¢)-dipicolinic acid complexes on colloidal mesoporous silica with diameter smaller than 100 nm by covalent bond grafting technique and obtained nearly monodisperse luminescent Eu-dpa-Si and Tb-dpa-Si functionalized hybrid mesoporous silica nanomaterials. The hybrid mesoporous silica nanoparticles exhibit intense emission lines upon UV-light irradiation, owing to the effective intramolecular energy transfer from the chromophore to the central lanthanidc Eu3+ and Tb3+ ions. The photoluminescence of colloidal mesoporous silica nanoparticles in water and ethanol is stable and may have some advantages for the potential applications of MSN-based luminescent nanomaterials in multifunctional optical imaging. Furthermore, the functionalized nano-materials MSNs after heat treatment exhibited a nearly white emission under UV irradiation, which might present a new way to create white emission materials.3. A general one-step route has been developed for the synthesis of rare-earth inorganic-organic hybrid colloidal (submicro-and nanospheres) particles. This kind of organic-inorganic hybrid colloidal particles can be prepared with a wide diversity of metal ions and organic ligands. The results show that organic-inorganic hybrid colloidal particles can be used as functional matrices for the encapsulation of a large variety of substances. Therefore, it is expected that this encapsulation approach will be extended to obtain amorphous/crystalline organic-inorganic hybrid particles that have novel functionalities. The combination of these capabilities with the encapsulated species open up new avenues in various fields, such as cell biology, drug delivery, diagnostics, and so on. Furthermore, the size of the colloidal particles can be controlled precisely and self-assembled into a photonic crystal.4. We present a new way to create color kinetic zeolite-like metal-organic frameworks by efficient energy transfer between host frameworks and guest lanthanide ions via ionic exchange. The tunable color emission is excited via energy transfer from H3ImDC ligands that upon filling the zeolite nanochannels act as light harvesting antenna. Furthermore, we can tune the luminescence color over a wide range (blue, green, white and red) by varying the amounts of the rare-earth cations and tailoring the excitation wavelength.