Multi-Complex Of Rare Earth Ions As Fluorescence Probes For The Sensitive And Selective Detection Of Typical Inorganic Contaminations

With the rapid development of the social economy,environmental problems are becoming increasingly prominent,quick and accurate monitoring of pollutants in the environment is of great significance.Compared with traditional detection methods,fluorescence analysis has gradually become a hot spot for analysis in recent years due to the advantages of fast,sensitive and convenient.Rare-earth ion based fluorescent probes can emit the unique fluorescence of rare-earth ions with sharp fluorescence peaks,longer fluorescence lifetime and larger Stokes shift.These unique luminescence characteristics make it popular in the construction of fluorescent probes.Phosphate?Pi?and copper ions are not only widely present in the environment,but also in the human body.Sensitive and selective detection of them is of great significance for ensuring environmental safety and human health.At present,most of the fluorescence detection methods for inorganic anions and cations are based on single-emission fluorescent probes,and the preparation of fluorescent materials has disadvantages of complicated processes and high-temperature during synthesis.In this paper,a dual emission ratiometric fluorescent probe which can be used to visually detect phosphate was constructed by selecting organic ligands rationally;At the same time,a multiple rare earth ion complex fluorescent probe was constructed to realize the rapid,sensitive and selective detection of copper ions in aqueous solution.The details are as follows:?1?Bifunctional lanthanide metal-organic frameworks?MOFs?used as ratiometric fluorescence probes for visualized super-sensitive detection of Pi.In the MOFs material,ciprofloxacin?CIP?functions as an energy donor and results in the fluorescence enhancement of Eu³⁺;the introduction of pyromellitic acid?BTEC?can cause the aggregation of the CIP-Eu³⁺complex,and red characteristic fluorescence of Eu³⁺at 614 nm is further enhanced?about 40times?.When Pi is added to the MOFs solution,CIP is released from the MOFs,red fluorescence of Eu³⁺is quenched and blue fluorescence of CIP is simultaneously recovered,the logarithm of the ratio of fluorescence intensity at 415 nm and 614 nm(log(F₄₁₅/F₆₁₄))has a good linear relationship with the concentration of Pi in the range of 0.01?10?M,thereby a ratiometric fluorescent probe for the detection of Pi was fabricated.The analysis of the fluorescence quenching mechanism shows that the quenching of fluorescence of Eu³⁺by Pi belongs to the dynamic and static quenching process,and the static quenching is dominant.The Eu-MOFs material show good selectivity and ultra-high sensitivity?detection limit up to 4.4 n M?towards phosphate,and has been applied for detecting phosphate sensitively and selectively in environmental samples and human urine samples.?2?The sensitive and selective detection of copper ions by multiple rare earth ion complex fluorescent probes.Pyridine-2,6-dicarboxylic acid?DPA?can coordinate with Eu³⁺and sensitize Eu³⁺to emit red fluorescence through energy transfer process;Polyethyleneimine?PEI?can not only coordinate with Eu³⁺but also can selectively recognize copper ions and quench the red fluorescence from DPA-Eu³⁺-PEI.The copper ion has almost no effect on the fluorescence of DPA-Eu³⁺.Experiments show that DPA-Eu³⁺-PEI can achieve the fluorescence response to copper ions within 1 min,and the fluorescence quenching efficiency has a good linear relationship with the concentration of copper ions in the range of 0.02-10?M with a detection limit of 8 n M.The analysis of the fluorescence quenching mechanism shows that the fluorescence quenching caused by copper ions is based on the charge transfer process between the excited state complex DPA-Eu³⁺-PEI-Cu²⁺,which is the so-called photoinduced charge transfer?PET?quenching.The fluorescent probe has been applied to the detection of copper ion concentration in waste water and human urine samples with satisfactory results.