Study Of Heavy Metal Ions Analysis Method Based On Lanthanide Coordination Polymers Fluorescent Probe

Rare earth coordination polymers materials can be divided into crystalline and amorphous lanthanide coordination polymers.Rare earth elements have unique internal 4F electronic structure,abundant valence electron number,strong coordination ability,various coordination modes and other characteristics.The 4F electron energy level with abundant configuration can produce F?F transition luminescence,and the fluorescence range of rare earth ions can be extended from the ultraviolet region to the near-infrared region.Based on the unique spectral characteristics such as large stokes shift,long luminous lifetime and narrow emission band,rare earth elements have been widely used in luminescent probe.After ligands with high light absorption efficiency are coordinated with rare earth to form rare earth organic coordination compounds,due to the antenna sensitization effect between the organic ligand and the rare earth ions,the energy absorbed by the organic ligand can be transferred to the resonant emission level of the rare earth ions in a non-radiative transition way,resulting in the sensitization of the rare earth to produce fluorescence or phosphorescence.Amorphous rare earth coordination polymers have been widely studied because of their advantages such as high fluorescence quantum yield,long fluorescence lifetime,large stokes shift and linear emission spectrum.At the same time,lanthanide coordination polymers have attracted much attention in the field of heavy metal ion detection,due to their abundant composition and ligand molecular selection,adjustable nano-structure and functional group modification.Amorphous lanthanide coordination polymers include single-ligand and single-ligand lanthanide coordination embedding,dual-ligand and dual-ligand lanthanide embedding type etc.Mono-ligand types are mostly single fluorescence signal sensors,which are easily disturbed by complex environment and solvent conditions due to incomplete coordination of central ions.As a result,the stability of the sensor is weak,the fluorescence signal intensity is easy to be interfered with,the quantum yield is low and the detection results are not accurate enough.In embedded lanthanide coordination polymers,energy transfer between ligand and guest molecules can be achieved by embedding guest molecules,but it is difficult to realize multiple sensitizations of embedded molecules.The dual ligand rare earth polymer fluorescent probe can fully sensitize the luminescence of rare earth ions by introducing appropriate auxiliary ligand and coordinating the central rare earth ions with the main ligand,which overcomes the shortcomings of the traditional sensor.In this paper,through the selection and utilization of biocompatible organic ligands such as 2-amino-terephthalic acid(2-ATA),luminol and nucleoside biological ligands such as GMP,Adenosine with other rare earth metal ions coordination,a new type of biocompatible rare earth coordination polymer fluorescent nano-probe was prepared and applied to the analysis and detection of heavy metal ions and biological enzymes in organisms or environment.This topic focuses on the construction and application of fluorescence probe of double ligand rare earth coordination polymer,and the main research contents are as follows:1.A novel dual-ligand lanthanide coordination polymer nanoparticles(Th T@luminol-Eu-GMP CPNPs)were synthesized for detecting alkaline phosphatase(ALP)and arsenate.The Th T@luminol-Eu-GMP CPNPs were constructed through self-assemble of central ion(Eu³⁺)with bridging ligands of guanosine phosphate(GMP)and luminol,and simultaneously embedded the guest dye molecule thioflavin T(Th T)during the process.This design boosted the fluorescent performance of Th T through two paths.The molecular rotation of Th T was restricted due to the tight embedding of Th T in CPNPs,resulting in an increased fluorescence of Th T on one hand.On the other hand,the overlapped spectra between the emission spectra of luminol and the excitation spectra of Th T induced the FRET effect,which further facilitated the fluorescence of Th T.In the presence of ALP,the ingenious structure of Th T@luminol-Eu-GMP was destroyed due to the specific shear of ALP to GMP,which not only got rid of the limiting effect of Th T,but also broken the FRET between luminol and Th T,leading to a sharply decreased fluorescence of Th T.Meanwhile,the AIE effect of the luminol was promoted,leading to an increased fluorescence of luminol.According to ratio of the fluorescence of Th T to luminol,ALP can be monitored sensitively.Moreover,the Th T@luminol-Eu-GMP can also be used to sensitively detect arsenate based on the inhibition of arsenate for ALP.2.A two-ligand ratio fluorescent probe 2-ATA-Eu-Adenosine was constructed by the synergistic sensitization of lanthanide metal Eu³⁺between Adenosine and 2-ATA ligand through the self-assembly site polymerization of Adenosine,2-ATA and Eu³⁺.In this process,2-ATA and Adenosine act to form an organic ligand containing an amide bond by synergistically effect.The sensitized Eu³⁺emits red light at 618 nm,and the blue light of 2-ATA at 425 nm is weakened due to the excited state intramolecular electron transfer(ESIPT),thus forming a double-emission fluorescent probe.In the presence of Al³⁺,the amide bond and Al³⁺specifically bind to replace Eu³⁺,which reduces the energy transferred to Eu³⁺by the ligand due to the synergistic effect.As a result,the fluorescence signal of Eu³⁺at 618 nm is decreased,while the fluorescence signal of 2-ATA at 425 nm is increased.According to the ratio of the fluorescence signal intensity of 2-ATA to Eu³⁺,a ratio fluorescence assay for the determination of Al³⁺was established.Since the addition of Al³⁺weakened ESIPT effect and enhanced fluorescence enhancement effect induced by Al³⁺chelation,the fluorescence of 2-ATA at 425 nm was further enhanced,so the detection sensitivity of Al³⁺was greatly improved.The ratio fluorescent probe has also been successfully applied to the detection of Al³⁺in lake water and drinking water through the labeled recovery experiment,which has a good application prospect.