Lanthanide Coordination Polymers As Ratiometric Fluorescent Sensors:Design, Synthesis And Sensing

In recent years,fluorescence analysis is widely used due to its diversity of probes,high sensitivity,fast response,easy operation,and good selectivity.Lanthanide coordination polymers?LnCPs?are formed by self-assembly of lanthanide ions and organic ligands via the coordination bonds,and have excellent properties of inorganic and organic components.With these superior properties,such as long fluorescence lifetime,higher quantum yield,good biocompatibility and stronger adaptive encapsulation ability,LnCPs have provided unique advantages for fabricating fluorescence sensors.As a fluorescence sensing platform,the interaction between the target and the lanthanide ion or ligand in LnCPs,can be used to design the stretagy for slectivly recongnanizing the target through the change of fluorescence intensity.Besides,with the adaptive encapsulation ability of LnCPs,it is facile to design dual-signal fluorescent probes by encapsulating fluorescent guest materials such as dye molecules,quantum dots,and luminescent metal nanoclusters.In this work,we designed and synthesized three kinds of dual-signal fluorescent probes based on the LnCPs,and constructed three ratiometric fluorescence sensors to selectively detect the corresponding targets.The specific work is as follows:1.A ratiometric fluorescence sensor based on coumarin@AMP-Tb for ciprofloxacin?CIP?assayIn this work,we proposed a ratiomatric fluorescent strategy for sensing CIP by using coumarin doped LnCPs.Herein,the AMP-Tb LnCPs were prepared by self-assembly of AMP and Tb³⁺.Coumarin molecules were encapsulated in polymers as guest molecules,and the obtained coumarin@AMP-Tb only emitted the characterized fluorescence of coumarin.CIP can act as a second ligand to coordinate with Tb³⁺,and transfer its energy to Tb³⁺for sensitizing its luminescence.In this process,the fluorescence of coumarin remained constant and servied as the internal control for self-calibration.Based on the phenomenon,a ratiometric fluorescence sensor was constructed to detect CIP.2.Ratiometric fluorescence sensing of Fe^2+/3+based on CDs@AMP/Phen-Tb LnCPswe proposed a ratiomatric fluorescent strategy for sensing Fe²⁺by using the carbon dots?CDs?doped LnCPs.Herein,the AMP-Tb LnCPs were prepared by self-assemble of AMP and Tb³⁺,and CDs were encapsulated during the assembly process as guest materials.Phenanthroline?Phen?could coordinate with Tb³⁺,and strongly sensitize its luminescence through energy transfer.Therefore,the obtained CDs@AMP/Phen-Tb could emit dual fluorescence signals of CDs and Tb³⁺.The fluorescence signal of Tb³⁺could be specifically quenched by Fe²⁺due to the high affinity between Phen and Fe²⁺,while that of CDs remained constant serving as the internal control for self-calibration.In addition,with the help of a reducing agent,which can reduce Fe³⁺to Fe²⁺efficiently,the proposed method can also be applied to detection Fe³⁺indirectly.3.Ratiometric fluorescent sensing of an anthrax biomarker based on bimetallic lanthanide coordination polymersHerein,the LnCPs were constructed by self-assembly of 1,3,5-benzenetricarboxylic acid?BTC?and adenosine monophosphate?AMP?with Tb³⁺and Eu³⁺,i.e.Tb/Eu-BTC/AMP.BTC played as a linker and sensitizer in the LnCPs,and as another linker,AMP was introduced to enable the LnCPs disperse well in water,and thus make the probe can work in water.Under irradiation,the Tb/Eu-BTC/AMP emitted both characteristic luminescence of Tb³⁺and Eu³⁺.Upon addition of DPA,the luminescence of Tb³⁺significantly increased,while that of Eu³⁺decreased.Therefore,a novel ratiometric fluorescent sensor for detecting DPA was fabricated by measuring the ratio of fluorescent intensity of the Eu@Tb-BTC/AMP.