The Application Of Lanthanide Complex In Luminescent Sensor And Near-Infrared Emission

The research of luminescent lanthanide complexes is the interdisciplinary field of inorganic,organic and noctilucence.The luminescence from lanthanide ions is narrow emission spectra,long-lived and large stokes' shifts,which was widely used in chromophore, sensors,bioimaging,materials science,and so on.While the design of sensitizer-functionalized lanthanide complexes that exhibit efficient luminescence in the near-infrared region is currently of interest because of their potential applications in fluoro-immuno assays,laser systems,optical signal amplifiers,etc.In this work,two organic chromophores were used as antenna to sensitize the lanthanide ions,and the property of the complexes was researchedThe 1,10-phenanthroline and quinoline were linked through the method for imidazole ring,and the europium complex was obtained by a simply reaction of the ligand and Eu(TTA)₃(TTA=thiophentrifluoroactone) in ethanol solution,its molecular structure was confirmed by single-crystal X-ray diffraction.The research showed that the complex exhibits high selectivity and sensitivity for Pb²⁺.In the absence of Pb²⁺,the FRET from the quinoline donor to the Eu(â…¢) acceptor might be blocked by the electron-rich imidazole spacer,only blue donor emission was observed upon the excitation of the quinoline chromophore.While the selective complexation with Pb²⁺,the FRET window will be unblocked and the excitation of the quinoline chromophore is capable of efficiently sensitizing lanthanide luminescence via energy transfer,consequently increased red Eu(â…¢) emission can be observed.The coexistent two fluorescent windows afford the the possibility of ratiometric Pb²⁺ sensing.The Uv-vis titration and ESI-MS spectra revealed that the 1:1 stoichiometric host-guest complex was formed in solution.Three Coumarin amine derivative ligands were synthesized and used as an antenna sensitizer for lanthanide ions(Yb³⁺,Nd³⁺).The ESI-MS spectra and elemental analysis revealed that the ligand formed a complex with the lanthanide ion in a ratio of 1:1.The fluorescent investigation of the complex in water revealed that the ligand formed excimer and causes the red shift of the corresponding excitation wavelength.The results showed that the diketonate-like structure could bind lanthanide ions closely and get ride of the interference of H₂O molecules,and overcome the difficult of sensitizing lanthanide NIR emitting in aqueous solution.Upon the addition of lanthanide ions(Yb³⁺,Nd³⁺) with their TTA salts,typical linelike lanthanide emission could be observed in the NIR region upon the excitation of coumarin chromophore(415nm).In the meanwhile,successive quenching of excimer emission were observed,which suggest the energy transfer took place from the excimer triplet state to the excited state of lanthanide centers.