Synthesis And Fluorescence Sensing Properties Of Fluorene-based Luminescent Molecules

Environmental pollution and food safety are long-standing global concerns that are closely related to human life and health.The simple,rapid and sensitive detection of ions,small molecules and large molecules in food,environment and life systems is an urgent problem in the fields of food safety,environmental monitoring and human health.Fluorene and its derivatives are the " star molecules " due to their easily modified structure,wide energy gap and high luminescence efficiency.The development of fluorene-based fluorescence sensors is expected to achieve low cost,simple operation,fast response and sensitive detection of fluorescence analysis and detection.In this thesis,five fluorenebased luminescent molecules were designed and synthesized,and they were used for the fluorescence sensors of Tetracycline hydrochloride(TC),Folic acid(FA)and 2,4,6-Trinitrophenol(TNP),respectively.The related study mainly includes the following three parts:Part 1: Construction of an IFE-effect fluorescence probe and detection of tetracycline hydrochloride in milkTetracycline hydrochloride(TC)is the most widely used antibiotic in the tetracycline family.However,the irrational use of TC leads to environmental pollution and human health problem still exist.Therefore,it is crucial to construct a sensor for detecting TC.In this study,a fluorene-based fluorescence sensor DPF was constructed for the detection of TC.The experimental results showed that the probe molecule DPF exhibited a wide linear range(0.5-70 μM),a low limit of detection(0.24 μM),and a fast response for TC.The DPF was further used for the detection of TC in milk,and the results showed that the probe has good potential for the detection of real samples.The mechanism of TC detection by DPF is inner filter effect.This work not only constructs a fluorescent sensor for the detection of TC,but also provides a feasible method for the detection of TC in real samples.Part 2: Construction of fluorene-based fluorescence sensor with AIE effect and detection of folic acid in serumFolic acid(FA)is an essential vitamin that is essential for normal growth and development and various physiological processes in the human body.Therefore,it is important to design novel fluorene-based fluorescence probes and use them for the detection of FA.In this study,two new fluorene-based fluorescence probes F-CN-S and F-CN-N with special structure of a-cyanoethylene were designed and synthesized based on the mechanism of restricted intramolecular motion.In addition,based on the inner filter effect,we achieved the detection of FA by F-CN-N,which has a linear range of7-100 μM and limit of detection was 2.35 μM.This work provides a new method for the design and development of novel AIE fluorene-based fluorescent probes,and also has a reference value for the detection of FA in serum.Part 3: Construction of a dual-state emitting fluorene-based fluorescence probe with ICT effect and detection of TNP2,4,6-Trinitrophenol(TNP)is one of the most explosive and dangerous nitroaromatic derivatives and a "notorious" environmental pollutant.In this study,a D-π-A type fluorescent probe molecule with intramolecular charge transfer effect,F-CN-CN,was designed and synthesized.In this molecule,the fluorene unit acts as an electron donor,the malononitrile unit acts as an electron acceptor,and the benzene ring as a π-spacer group.The probe exhibits a dual-state emission effect based on a strategy of adding conjugate-induced stiffness to the distorted molecule.The probe F-CN-CN was applied for the detection of TNP,and the experimental results showed that the sensor has a wide linear range(0.9-100 μM)and low limit of detection(0.57 μM).F-CN-CN was further used for the detection of TNP in Yellow River water samples,and the probe showed good potential for the detection of actual samples.Finally,spectral overlap and density functional theory calculations showed that the detection mechanism of TNP is a synergistic effect of inner filter effect and photoinduced electron transfer effect.This work provides new ideas for the design and development of dual-state luminescent fluorescent probes based on the construction of a novel fluorescent probe for the detection of TNP.