Preparation,Structures And Luminescent Properties Of Luminescent Composites Based On Rare Earth Complexes

Rare earth metal elements have great application potential due to their unique luminescent properties.The"antenna effect"can increase the luminescence intensity of rare earth ions by complexing a rare earth metal element with an organic ligand.However,the resulting rare earth complex has a disadvantage of poor light stability,unstable thermal properties and low mechanical strength,greatly limit its practical application.The combination of a rare earth organic complex with a matrix having thermal and mechanical properties is an effective way to solve the above problems.In this thesis,we used different construction methods to combine rare earth organic complexes with hybrid materials to prepare luminescent composites based on rare earth complexes,and systematically studied their structure and fluorescence properties.Firstly,the siloxane-based compound 3-（triethoxysilyl）propyl isocyanate,which can undergo sol-gel reaction,is introduced into 3,4-dihydroxybenzoic acid to form a bifunctional group by chemical modification.3,4-bis（3-（triethoxysilylpropyl）carbamoyloxy）benzoic acid ligand.Two kinds of hybrid materials containing Eu³⁺and Tb³⁺were prepared by hydrolysis and condensation of siloxane groups in the ligand to form Si-O-Si inorganic network,which were then assembled into MCM-41 molecular sieve.The experimental results show that the composites based on rare earth complexes of 3,4-dihydroxybenzoic acid have high thermal stability,good luminescent properties,long luminescent decay life and high quantum yield.Secondly,we react 2-phenylmalonic acid or malonic acid with aluminum isopropoxide,butyl orthosilicate and tetraisobutyl titanate,and coordinate with Eu³⁺or Tb³⁺in the sol state.Finally,the hybrid materials containing Ti-O-Ti,Si-O-Si and Al-O-Al inorganic networks were prepared by further polycondensation,and the structural composition and microstructure of the materials were systematically studied.The fluorescent luminescence properties of the material.These materials are amorphous,have good thermal stability,and have higher quantum efficiency and luminescence lifetime than other hybrid materials.Hybrid materials containing Eu³⁺and Tb³⁺exhibited typical red and green emission,respectively,indicating that the organic ligand can effectively sensitize Re³⁺ions in the hybrid material.Afterwards,2,5-thiophene dicarboxylic acid and 3,4-bis（4-methoxypyridine）benzoic acid are used as bifunctional compounds.They react with aluminium isopropoxide,butyl orthosilicate and tetraesopropyl titanate respectively and coordinate with Eu³⁺or Tb³⁺in the sol state.Finally,hybrid materials containing Ti-O-Ti,Si-O-Si and Al-O-Al inorganic networks are prepared by further condensation.The materials are systematically studied.The structure,morphology and fluorescence properties of the hybrid materials were also investigated.The prepared materials are amorphous and thermally stable,and the relationship between organic and inorganic parts is realized at the molecular level.Finally,a novel method for preparing fluorescent polymer colloidal crystals with a simple preparation process and low cost has been developed.First,a rare earth complex containing a double bond as a ligand is prepared and then introduced into the hydrogel nanosphere by emulsion polymerization.The hydrogel nanospheres form ordered colloidal crystals on the hot water surface under the action of gravity,buoyancy,and especially interparticle interaction（repulsive and attracting）.Finally,a large-area,high-quality colloidal crystal can be transferred to the silicon wafer by the pulling method.More importantly,due to the introduction of the rare earth complexes Eu（TTA）₂phenMA and Tb（acac）₂phenMA,the prepared photonic crystals have strong fluorescence.This composite material can greatly expand the application of photonic crystals in imaging display,optical switching,anti-counterfeiting,sensors and information storage.