Energy Transfer And Luminescence Of Rare Earth Hybrid Materials Based On Molecular Bridge

This paper is aim to develop a series of co-luminescent organic-inorganic hybrid molecular material.In this paper, the study concentrates on the syntheses of organic-inorganic molecular-based hybrid material with the two components equipped with covalent bonds. The functional bridge ligands with two components equipped with covalent bonds which not only can coordinate to RE ions but also occur an in situ sol-gel process with inorganic host precursor tetraethoxysilane (TEOS), resulting a kind of molecular hybrid material with double chemical bond (RE-0 coordination bond and Si-0 covalent bond). In addition, the two components are connected by covalent grafting, which can achieve true interconnection between the organic and inorganic moieties and successfully solve the problems of quenching effect of luminescent centers and separation of different phase. In nature, the organic components play a role of network modifier, which can not only realize the possibility of molecular-based material but also tailor the complementary properties of novel multifunctional advanced materials through covalent grafting between the different components. The final materials exhibit excellent luminescent and physical properties and have been applied widely in many fields.As we all know, functional bridge ligands can absorb radiant energy and then transfer it to active lanthanide ions. Because the rare earth nitrates can hydrolyze and polymerize together with functional bridge ligands and TEOS, we considered that active lanthanide ions and inert lanthanide ions coexist in the same molecular hybrids at molecular degree through the chemical bonded Si-0 network. In this sort of co-luminescence system, because the inert RE complexes and the active RE complexes are in the same molecule and the distance between them is very small, so the inert RE ions can act as a energy bridge through which the energy of ligands in the inert RE complexes can be transferred to the active lanthanide ions through intramolecular energy transfer, which lead to the enhanced luminescence in the hybrids. In addition, the concentration of inert lanthanide ions is great enough and each of active ion molecular fragments is surrounded by many inert ion molecular fragments, then these inert ion molecular fragments can form a cage which acts as an energy-insulating sheath that can prevent collision with water molecules and decrease the energy loss of active ion molecular fragments, thus luminescence quantum efficiency and increasing luminescence intensity.