Preparation And Luminescence Of SiO₂/TiO₂ Matrices Modified By Lanthanide Complexes

In recent years,lanthanide organic-inorganic hybrid materials have been widely used in optical devices,luminescent sensors,clinical diagnosis,fluorescent immune probes,laser materials and telecommunications due to their excellent luminescence.This thesis is aim at designing and preparing novel lanthanide organic-inorganic hybrid materials with tunable luminescence.Three new types of luminescent lanthanide organic-inorganic hybrid materials have been successfully prepared by covalently grafting lanthanide complexes onto silica and titania matrices choosing four kinds of bifunctional bridged organic ligands.The resulting hybrid materials were characterized by FT-IR,Raman,XPS,PXRD,SEM,TEM,EDS,TGA and PL.The tunable luminescent emission of hybrid materials depending on stoichiometric ratio of lanthanide ions,excitation wavelength and metal ion concentration was systematically investigated,and luminescent detection ability of some hybrid materials for NB and Al³⁺ion was explored.The thesis includes seven chapters,and the main contents are summarized as follows:Chapter 1:The research progress of lanthanide hybrid materials based on silica,titania and other matrices is reviewed.Chapter 2:Six kinds of lanthanide complexes Ln(?-diketone)₃(H₂O)_n(Ln=Eu,Tb,?-diketone=Htta,Hacac,Htfacac,Hhfac,Hbfa and Hdbm)were successfully prepared by the reactions of lanthanide salts with?-diketone ligands under appropriate conditions.Their luminescence properties were investigated,indicating that the energy transfer from Tb^III to Eu^III exists in the heterometallic coordination units.Chapter 3:New lanthanide hybrid materials Nano SiO₂-TESPIC-TPY-Ln(?-diketone)₃ were successfully prepared by using silylated 2,2':6',2"-tridipyridine(TESPIC-TPY)as the linker to anchor Eu(tta)₃ and Ln(dbm)₃(Ln=Eu,Tb)on the surface of Nano SiO₂.Luminescent properties of these hybrid materials were investigated,showing that TESPIC-TPY ligand can sensitize luminescence of lanthanide ions with?-diketone,and the energy can transfer partly or effectively from TESPIC-TPY ligand to lanthanide ions.In addition,a hetero-metallic hybrid material Nano SiO₂-TESPIC-TPY-Eu_0.5Tb_0.5(dbm)₃ can be used as a white light emission material.At the same time,the energy transfer from Tb^III to Eu^III phenomenon is appeared,and the energy transfer efficiency is about 13.2%.Chapter 4:Novel luminescent hybrid materials Ln(?-diketone)₃ctpy-TiO₂(Ln=Eu,Tb,?-diketone=Hacac,Htfacac,Hhfac and Hbfa,Hctpy=4'-carboxy-2,2':6',2"-tridipyridine)were prepared by sol-gel method using Hctpy as the linker.Luminescent properties of these hybrid materials were investigated,indicating that tunable luminescent emission of hetero-metallic hybrid materials depends on the stoichiometric ratio of lanthanide ions.With the increase of the mole ratio of Eu^III/Tb^III,the emission color changes from green to yellow to red.At the same time,it is found that a linear relationship between the logarithm of the intensity at ⁵D₀?⁷F₂(Eu^III)and the logarithm of Eu^III/Tb^III molar ratio,indicating that hetero-metallic hybrid materials can be used as efficient luminescent taggants.The energy transfer can be observed from TiO₂ matrix and Hctpy ligand to central Ln^III ions,and from Tb^III to Eu^III in hetero-metallic hybrid materials.With the decrease of the mole ratio of Eu^III/Tb^III,the energy transfer efficiency from Tb^III to Eu^III gradually decreased.In addition,Eu(hfac)₃ctpy-TiO₂ can be used as a luminescent probe to efficiently detect NB pollutant.Chapter 5:Novel luminescent hybrid materials Ln(?-diketone)₃L-TiO₂(Ln=Eu,Tb,?-diketone=Hacac,Htfacac,Hhfac,Hbfa and Hdbm,HL=4?-(2-carboxyphenyl)-2,2?:6?,2?-terpyridine)were prepared by sol-gel method using HL as the linker.Luminescence properties of these hybrid materials were investigated,indicating that tunable luminescent emission of hetero-metallic hybrid materials depends on the stoichiometric ratio of lanthanide ions.With the increase of the mole ratio of Eu^III/Tb^III,the emission color changes from green to yellow to red.At the same time,it is found that a linear relationship between the logarithm of the intensity at ⁵D₀?⁷F₂(Eu^III)and the logarithm of Eu^III/Tb^III molar ratio,indicating that hetero-metallic hybrid materials can be used as efficient luminescent taggants.The energy transfer can be observed from TiO₂ matrix and HL ligand to central Ln^III ions,and from Tb^IIIto Eu^III in hetero-metallic hybrid materials.With the decrease of the mole ratio of Eu^III/Tb^III,the energy transfer efficiency from Tb^III to Eu^III gradually decreased.In addition,Eu(bfa)₃L-TiO₂,Tb(bfa)₃L-TiO₂,Eu_0.5Tb_0.5(bfa)₃L-TiO₂ can be used as luminescent probes to efficiently detect NB pollutant.Chapter 6:Novel lanthanide hybrid materials Ln(hfac)₃ctpy-SiO₂@m TiO₂(Ln=Eu,Tb)and Eu_0.5Tb_0.5(acac)₃ctpy-SiO₂@m TiO₂ were successfully prepared by using Hctpy as the linker to anchor Ln(hfac)₃ and Eu_0.5Tb_0.5(acac)₃ on the surface of SiO₂@m TiO₂ core-shell microspheres.Luminescence properties of these hybrid materials were investigated,indicating that tunable luminescent emission of hetero-metallic hybrid materials depends on the stoichiometric ratio of lanthanide ions and excitation wavelength.With the increase of the mole ratio of Eu^III/Tb^III,the emission color of hetero-metallic hybrid materials Eu_xTb_1-x(hfac)₃ctpy-SiO₂@m TiO₂ changes from green to yellow to red.At the same time,it is found that a linear relationship between the logarithm of the intensity at ⁵D₀?⁷F₂(Eu^III)and the logarithm of Eu^III/Tb^III molar ratio,indicating that hetero-metallic hybrid materials can be used as efficient luminescent taggants.With the decrease of the mole ratio of Eu^III/Tb^III,the energy transfer efficiency from Tb^III to Eu^III gradually decreased.In addition,the emission color of Eu_0.5Tb_0.5(acac)₃ctpy-SiO₂@m TiO₂ alters from green to blue-green to blue color with changing the excitation wavelength.Chapter 7:A novel hybrid material Eu(tta)₃bpdc-SiO₂@m TiO₂(H₂bpdc=2,2'-bipyridine-3,3'-dicarboxylic acid)was successfully prepared by using H₂bpdc as the linker to anchor Eu(tta)₃ on the surface of SiO₂@m TiO₂ core-shell microspheres.The resulting hybrid material has uniform core-shell microsphere structure,shows bright red color and long lifetime(0.52ms).The multi-color emission of Eu(tta)₃bpdc-SiO₂@m TiO₂ from red to pink to blue color can be realized only by adjusting the concentration of Al³⁺ions through cation exchange process.By changing the conjugation of ligands(Hctpy and HL),the types of inorganic matrices(Nano SiO₂,TiO₂ and SiO₂@m TiO₂),the types of lanthanide complexes,the energy transfer pathway and luminescence mechanism of lanthanide hybrid materials were revealed.