Fluorescent Lanthanide Complex Sensor Based On Fluorinated Carboxylic Acid Ligands And Their Properties

In this paper,we examine lanthanide complexes,which are composed of lanthanide elements and organic ligands.Due to their unique inner layer 4f electron structure,lanthanide metal ions exhibit sharp emission peaks,long luminous lifetimes,high color purity,and wide Stokes shifts.As a result,they are widely used in chemical sensing for detecting cations,anions,organic small molecules,and temperature.Additionally,they are employed in optical imaging,up-conversion luminescence,near infrared imaging,photothermal therapy,and laser technology.In this study,we screen suitable organic ligands to design and synthesize lanthanide complexes with unique sensing properties.We also prepare these complexes into fluorescence sensing devices that are easily portable and user-friendly for everyday use.Specifically,we investigate the fluorescence and sensing properties of three series of lanthanide complexes with carboxylic acid ligands through single crystal analysis.This paper is organized into the following three sections:（1）Synthesis of new dinuclear lanthanide complexes and visual bifunctional sensing devices based on the Eu complexThe development of portable sensing devices and multifunctional sensors plays a crucial role in our daily lives.In this study,we successfully obtained two binuclear lanthanide complexes using Tb³⁺and Eu³⁺as metal center ions,1,10-phenanthroline as the auxiliary ligand,and 3,4-difluorobenzoic acid as the primary ligand.The precise structure of the complexes was determined by single crystal X-ray diffraction as[Ln2（DFBA）6（dmp）2（H2O）2]（Ln=Eu 2-1,Tb 2-2,HDFBA=3,4-difluorobenzoic acid,dmp=4,7-dimethyl-1,10-phenanthroline）.The fluorescence properties were studied,and we found that complex 2-1 demonstrated the ability to rapidly detect ferrous ions(Fe²⁺)and acetylacetone（acac）with low detection limits of 5.6 and 1.0ppb,respectively.Furthermore,we designed portable sensing devices using agarose gel,test paper,and film on several surfaces,including plastic tube,glass,coins,test paper,stone,leaf,carbon rod,and iron sheet surfaces,enabling visual and rapid detection of Fe²⁺in water and acac vapor in diverse and complex environments.（2）Portable and luminescent sensing device for antibiotics in human urine and real water samplesAntibiotics are important drugs for the prevention and treatment of diseases,but the abuse of antibiotics is also worrying.In this work,we designed and synthesized two new lanthanide complexes with 2,4,5,6-tetrafluoro-resorbenzoic acid（H2TFPA）as the primary ligand,and 1,10-phenanthroline（phen）as the auxiliary ligand under mild solvo-,hydro-thermal conditions.The molecular formula of the two complexes are[[Ln2（TFBA）3（phen）2（H2O）2]n,Ln=Tb 3-1,Eu 3-2].At the same time,investigation also found that 3-1 has good selectivity and anti-interference for the detection of the antibiotic of ciprofloxacin（CIP）,the limit of detection（LOD）for CIP can reach ultra-sensitive value of 0.17 ppm.In 1.0×10^-7-1.0×10^-6 M,CIP showed an excellent linear relationship with the luminescence intensity of 3-1.Most importantly,sensing device of test paper based on 3-1 has been developed,which is a fluorescence sensing device with strong selectivity,anti-interference,sensitive,which is portable and visible to the naked eye for CIP detection in real samples such as human urine,lake water,and tap water.Antibiotics are essential for preventing and treating diseases,but their overuse is concerning.Here,we synthesized two new lanthanide complexes with 2,4,5,6-tetrafluoro-resorbenzoic acid（H2TFPA）as the primary ligand and 1,10-phenanthroline（phen）as the auxiliary ligand under mild conditions.The molecular formula of the complexes are[[Ln2（TFBA）3（phen）2（H2O）2]n,Ln=Tb 3-1,Eu 3-2].We discovered that 3-1 exhibits strong selectivity and anti-interference properties for detecting the antibiotic ciprofloxacin（CIP）.Its ultra-sensitive limit of detection（LOD）for CIP is 0.17 ppm,and there is an excellent linear relationship between the luminescence intensity of 3-1 and CIP concentration in the range of 1.0×10^-7-1.0×10^-6M.We have developed a portable and visible fluorescence sensing device based on 3-1 to detect CIP in real samples such as human urine,lake water,and tap water.This test paper-based device is highly selective,anti-interference,and sensitive.（3）Multifunctional lanthanide nanoparticle for early carcinoid diagnosis and trace water detection in ethanolThe development of multifunctional and sensitive sensors for rapid early cancer diagnosis in vitro and efficient detection of trace water in organic solvent is highly desirable.To achieve this,we prepared novel lanthanide nanoparticles,including[[Ln（CFC）3（HCFC）]·4H2O,Ln=Eu 4-1,Tb 4-2],as well as Tb³⁺,Eu³⁺co-doped binuclear lanthanide nanoparticles[4-3,Tb0.33Eu0.67（CFC）3（HCFC）·4H2O].Our in-depth studies revealed that 4-1,along with its sensing devices of test paper and agarose gel,can detect trace carcinoid cancer biomarkers in real human urine.This was achieved using a dynamic luminescence quenching process,with an ultra-low limit of detection（LOD）of 0.8 ppb and a response time of 2.0 min.Furthermore,terbium and europium co-doped nanoparticle 4-3 provides dual strong line-like emissions at ⁵D₄→⁷F₅ and ⁵D₀→⁷F₂ transitions for Tb³⁺and Eu³⁺,respectively,under a single excitation.This shows high sensitivity and a low LOD for the trace of water（0.038%v/v）in ethanol through self-calibration sensing.Our findings indicate that 4-3 is the most sensitive probe for the trace of water in ethanol to date.The detection mechanisms for the detection of 5-HIAA and water were determined through both experiments and quantum chemical studies.