Synthesis And Properties Of Hybrid Luminescent Materials Based On Rare Earth Complexes

Due to the common advantages of rare earth ions and matrix materials such as relatively strong photoluminescence emission,long luminescence lifetime,high luminescence quantum yield,photo-stability,thermal stability,etc.,rare earth hybrid materials have extensive application prospects in the fields of ion detection,gas sensing,drug release and so on.In this work,MCM-41-SH-Eu（phen）,MCM-41-SH-Ln（DPA）n were synthesized by Michael addition reaction,and a water-soluble hybrid luminescent material Ce₉Tb₁-EDTMP was prepared as well.The as-prepared hybrid luminescent materials were characterized by infrared spectrometer,thermogravimetric analyzer,scanning electron microscopy,transmission electron microscopy,X-ray spectrometer,UV-vis spectrophotometer,energy dispersive X-ray spectroscopy（EDS）and fluorescence spectrometer.The main investigation and results are as follows:（1）The new hybrid luminescent material MCM-41-SH-Eu（phen）was successfully prepared.In the preparation process,we firstly synthesized the double bond functionalized 1-10 phenanthroline ligand,and then the hybrid luminescent material MCM-41-SH-Eu（phen）was prepared by thiol-functionalized mesoporous silica and carbon-carbon double bond of functionalized 1-10 phenanthroline ligand via Michael addition reaction.The results indicate that after the mesoporous MCM-41 material undergoes a series of surface modification,its highly ordered two-dimensional hexagonal mesoporous structure is still mainly remained,suggesting the good thermal stability.MCM-41-SH-Eu（phen）conforms to the typical type IV,which indicates that the hybrid luminescent material has a typical mesoporous structure and a large pore volume and specific surface area.In the hybrid luminescent material MCM-41-SH-Eu（phen）,the complex Eu（phen）can absorb the light in the range of250⁴00 nm,and the energy transfer from the ligand to Eu³⁺can occurred efficiently.Thus,under the excitation of UV light,the hybrid material MCM-41-SH-Eu（phen）emits bright emission with the peaks at 577,586,611,652and 699 nm,attributed to the ⁵D₀→⁷F_J（J=0,1,2,3,4）energy level transitions respectively.The fluorescence decay curve conforms to a single exponential decay behavior,and the fluorescence lifetime is 0.36 ms.（2）the hybrid luminescent materials[MCM-41-SH-Ln（DPA）n,Ln=Tb,Eu;n=1,3]were synthesized by means of the Michael addition reaction.The synthesis process is as follows:Firstly,a sulfhydryl-functional mesoporous silica MCM-41-SH was synthesized.Then,a rare earth organic ligand containing a deficient electron double bond[Ln（DPA）n（Ln=Eu,Tb;n=1,3）]was synthesized.Finally,the rare earth hybrid materials[MCM-41-SH-Ln（DPA）n,Ln=Tb,Eu;n=1,3]were prepared by Michael addition reaction of fluorenyl-double bond.The analysis of the infrared spectrum and ultraviolet visible spectrum confirmed that the[Ln（DPA）n（Ln=Eu,Tb;n=1,3）]can be successfully grafted onto the mesoporous silica.It can be seen from XRD and TEM images that the as-prepared hybrid luminescent materials has a typical mesoporous two-dimensional hexagonal mesoporous structure.After grafting of rare earth organic ligands,the specific surface area,pore volume and pore size are significantly reduced.[MCM-41-SH-Ln（DPA）n,Ln=Tb,Eu;n=1,3]emit bright green and red light respectively under the excitation of ultraviolet light,that is emitting ⁵D₄→⁷F_J transitions of Tb³⁺（J=6,5,4,3）or ⁵D₀→⁷F_J transitions（J=0,1,2,3,4）of Eu³⁺.The fluorescence lifetimes of MCM-41-SH-Tb（DPA）₃ and MCM-41-SH-Eu（DPA）₃ are 1.31 and 1.56 ms,respectively.and their luminescence quantum efficiencies are approximately 53.8%and 66.5%,respectively.（3）Using ethylenediaminetetramethylenephosphonic acid as a ligand,we synthesized Ce³⁺doped,Ce³⁺and Tb³⁺co-doped,Tb³⁺doped aqueous rare earth hybrid materials under the condition of pH>7.5.The results indicate that the ethylenediamine tetramethylene phosphonic acid can effectively sensitize Ce³⁺,while the ability to sensitize Tb³⁺is weak.In the Ce³⁺and Tb³⁺co-doped hybrid phosphate luminescent material,It exists the efficient energy transfer phenomenon between Ce³⁺and Tb³⁺,and the energy transfer efficiency is calculated to be 13.2%.In the fluorescence titration,it indicates that the water-soluble Ce₉Tb₁-EDTMP has a fluorescent response to pyridine-2,6-dicarboxylic acid,suggesting the existence the coordination between the pyridine-2,6-dicarboxylic acid and Ce₉Tb₁-EDTMP,which leads to the change of the energy transfer pathway between luminescence systems.