The Study On Lanthnide Comlexes/Porous Boron Nitride Hybrid Luminescent Materials

In recent years,lanthanide complexes have received considerable attention because of their outstanding luminescent properties,such as characteristic and strong monochromaticity,full color emission,long lifetimes,etc.So lanthanide complexes have been widely used in many fields,including LED etc.However,the stability of the lanthanide complexes is greatly influenced by their surrounding chemical microenvironment,which limits their practical application in many fields.It is of great significance to improve the chemical microenvironment of lanthanide complexes,and then enhance their stability to obtain decent lanthanide luminescent materials with high efficiency and stability.One of the effective methods is to introduce lanthanide complexes into porous materials with high specific surface areas to obtain a kind of hybrid luminescent material.In this thesis,we report the design and synthesis of a novel kind of hybrid material via the incorporation of europium complexes into porous boron nitride?BN?microfibers with high specific surface area and excellent chemical stability.The structure and properties of the hybrid materials have been studied in detail.The main research content is as follows:?1?A novel kind of organic-inorganic hybrid material was developed via the incorporation of europium complexes?Eu?TTA?3,TTA=2-thenoyltrifluoroacetone?into porous BN.Firstly Eu³⁺ions was loaded into porous BN by adsorption of Eu³⁺ions in ethanol solution dispersed with porous BN,and then the organic ligands TTA was inserted into Eu³⁺@BN by a gas diffusion method.The confinement of the europium complexes within the pores of BN microfibers provided a stable chemical microenvironment for Eu?TTA?₃.In addition,the characteristic luminescent properties of Eu³⁺have been improved.The mechanism of luminescence can be found that the efficient energy transfer from BN host to TTA ligand and TTA ligand to Eu³⁺ions through“antenna effect”lead to the remarkable increase of luminescent.?2?The second ligand,i.e.phen?phenanthroline?,was introduced for the coordination with Eu³⁺to obtain a hybrid material Eu?TTA?₃phen@BN,and compared properties with Eu?TTA?₃@BN.After the loading of phen,the luminescent properties of the Eu?TTA?₃phen@BN were both improved.When the Eu?TTA?₃phen@BN sample was excited by UV light,efficient energy transfer from BN host to TTA and phen ligands occurred,and then the ligands with enhanced light absorption abilities transferred the energy to Eu³⁺ions through“antenna effect”,leading to the remarkable increase of luminescence.?3?We also use BN nanospheres?BNNS?and porous BN nanofibers?BNNF?as hosts to synthesis of Eu?TTA?₃@BNNS and Eu?TTA?₃@BNNF,respectively.Compared with Eu?TTA?3@BN,the quantum yield and fluorescence lifetime of hybrid samples using BN nanospheres and nanofibers as hosts all decreased obviously.This result indicates that the porous BN microfiber provides a relatively stable chemical microenvironment for Eu?TTA?₃ molecules.The low specific surface areas and pore volumes of BN nanospheres are not beneficial for the strong interaction with Eu?TTA?3 molecules.Besides,the high surface defects in BN nanofibers also have adverse effect on the luminescence of Eu?TTA?₃molecules.A large number of micropores are distributed on the surface of BN nanofibers,which can be used to reunite the lanthanide complexes,thereby reducing the efficiency of the luminescen.