Design And Application Of Rare Earth Coordination Polymers With Fluorescence Sensing Function

Metal-organic coordination polymers are a class of crystalline materials with periodic structures formed by organic ligands through strong interactions with metal ions or metal clusters.Due to its extremely high specific surface area,porosity,and adjustable pore structure,it has received extensive attention in the fields of adsorption,catalysis,fluorescence sensing,and drug loading.Among them,coordination polymers with rare earth ions as the center and organic ligands as linkers have rich selection of central ions and ligand molecules,adjustable structure and functional group modification.This type of material has unique properties of large stokes shift,long luminescence lifetime,strong photostability,linear emission spectrum and high fluorescence quantum yield,and is considered to be one of the most promising fluorescence sensors.Hence,the rare earth coordination polymer fluorescent probes are favored by people,and significant progress has also been made in the identification of heavy metal ions and anions,and the detection of bio-molecules and organic pollutants.Based on this,this work carried out the following researches on rare earth coordination polymers:（1）Prepared a rare earth coordination polymer（Ce-MOFs）,using Ce-MOFs and gold nanoparticles（Au NPs）to design a"turn-on"fluorescence platform（Ce-MOF/Au NPs）for quantitative analysis of glutathione（GSH）.Due to the existence of fluorescence resonance energy transfer（FRET）and electrostatic interaction between Ce-MOFs and Au NPs,the fluorescence intensity of Ce-MOFs was quenched by Au NPs.The strong Au-SH formed between Au NPs and GSH hindered the FRET and electrostatic interactions between Ce-MOFs and Au NPs lead to the recovery of fluorescence.Based on this,fluorescence detection of GSH can be achieved.（2）Synthesized a rare-earth coordination polymer with dual emission signals for the detection of alkaline phosphatase.A rare earth coordination polymer（Ce-Tb@GMP）was designed by self-assembly of guanosine monophosphate（GMP）with rare earth cerium(Ce³⁺)and terbium(Tb³⁺).GMP molecules contain phosphate groups,N and O,and have strong affinity for Ce³⁺and Tb³⁺.The probe exhibits strong Tb³⁺green fluorescence emission and weak Ce³⁺characteristic peak under excitation.In the presence of ALP,the phosphate ester in GMP was hydrolyzed,resulting in the structural destruction of Ce-Tb@GMP,which influenced the coordination and energy transfer of Ce³⁺,Tb³⁺and GMP.At the same time,the fluorescent intensity of the characteristic emission peak of Ce-Tb@GMP decreased significantly.The method showed a low detection limit of 0.12 m U/m L in the concentration range of 0.2-60 m U/m L.At the same time,this method realizes the detection of ALP in real serum samples,laying a foundation for the application of fluorescent probes in bioanalytical science.（3）Designed a rare-earth coordination polymer with dual emission signals for ratiometric fluorescence detection of phosphate.A dual-emitting rare earth coordination polymer(Eu/Ce/Ui O-66-（COOH）₂ was synthesized by introducing rare earth ions cerium(Ce³⁺)and europium(Eu³⁺)from uncoordinated carboxyl groups on Ui O-66-（COOH）₂).The prepared Eu/Ce/Ui O-66-（COOH）₂ has three emission peaks at 377 nm,509 nm and 621 nm at the excitation wavelength of 250 nm.In the presence of phosphate(PO₄^3-),there is a strong coordination interaction between Ce³⁺and the O atom in the PO₄^3-group,which can lead to the quenching of fluorescence at 377 nm,while the fluorescence at 621 nm remains almost unchanged.Based on this,a sensitive ratiometric fluorescence detection of phosphate was developed.This method can surmount wrong signals derived from the environmental influence and possess inherent self-calibration property.Under optimal conditions,the fluorescence intensity ratio of Eu/Ce/Ui O-66-（COOH）₂(I₃₇₇/I₆₂₁)and PO₄^3-exhibited a good linear response in the concentration range of 0.3-20μM,with a detection limit of 0.247μM.In addition,this ratiometric fluorescence probe can be used to detect PO₄^3-in real water samples with high sensitivity and selectivity.