Design,Synthesis,Performance And Application Of Fluorescent Probes For Sulfur Dioxide And Uranyl Ions

Fluorescent probe technology is a detection technology that has attracted much attention in recent years and has significant advantages,such as simplicity,high sensitivity,low detection limit,short response time,and in situ real-time monitoring.This technology is widely used in energy,medical,military,science and technology fields,such as ion detection,food analysis,pesticide residue detection,biomarker and tracking,fluorescence imaging,etc.,and gradually becomes one of the research hotspots in various fields.In recent years,with the progress of society and the development of the country,ecological and environmental issues have become the focus of attention in various countries.The concentration of various substances in the environment has a prescribed standard,and once this standard is exceeded,environmental pollution will result,and most environmental pollutants will pose a certain threat to the human body,affecting human health and leading to various diseases.Therefore,in order to protect the environment and safeguard the lives of the people,the harmful substances in the environment must be effectively tested to ensure that they meet the national standards.The environmental pollutants,sulfur dioxide and uranium can damage the ecological environment if they exceed the prescribed standards,and can cause damage to the organism if they are consumed in excess by the human body.Therefore,in this thesis,four new organic small molecule fluorescent probes were designed and synthesized based on the detection of sulfur dioxide（SO₂）and uranyl ions(UO₂²⁺)and their performance was systematically investigated.The details of the study are as follows:Firstly,two water-soluble fluorescent probes DPQ-1 and DPQ-2 targeting mitochondria were designed and synthesized by introducing the quinoline methyl portion on quinolinonitrile and pyranenitrile for the detection of sulfur dioxide derivatives in organisms and the environment.Nucleophilic addition reactions of carbon-carbon double bonds with SO₂derivatives change the electronic configuration and produce changes in fluorescence signals.The excitation wavelengths of DPQ-1 and DPQ-2 were obtained by testing the UV absorption spectra and fluorescence spectra at 490 nm and 470 nm respectively,and the emission wavelengths obtained under this excitation are 590 nm and600 nm,respectively.Both probes have good selectivity and can achieve the quantitative detection of SO₂derivatives and imaging of exogenous SO₂derivatives in organisms.Compared with most of the reported probes,DPQ-2 shown a faster response（less than 5 s）and lower detection limit（3.11 n M）,and has been successfully applied to the detection of SO₂derivatives in environmental water samples and wine samples.Secondly,a fluorescent probe PT-OBD was designed and synthesized by linking phenothiazine moiety with o-phenylenediamine through Schiff base reaction using phenothiazine as fluorophore,and the detection of UO₂²⁺was successfully achieved through the coordination of nitrogen-oxygen atom with uranyl ion(UO₂²⁺).The results of fluorescence spectroscopy tests showed that PT-OBD had a distinct fluorescence signal at515 nm,and the fluorescence was quenched after the addition of UO₂²⁺.The titration experiments showed that the fluorescence intensity and UO₂²⁺concentration（0-1μM）had a good linear relationship and the detection limit was 95 n M.PT-OBD achieved better results in terms of response speed,with a response time of 1 min,and successfully achieved the detection of UO₂²⁺concentration in actual environmental samples.Thirdly,an AIE small molecule fluorescent probe TPE-ADX was designed and synthesized for the detection of uranyl ion(UO₂²⁺)using tetraphenylene（TPE）as the fluorophore and amidoxime group as the recognition group,and its structure was characterized by nuclear magnetic resonance spectroscopy,mass spectrometry and infrared spectroscopy.The results of UV absorption spectroscopy and fluorescence spectroscopy tests showed that TPE-ADX shown a significant AIE effect,emitting a distinct blue-green fluorescence in H₂O/THF（f_w=90%）solution,and the fluorescence was quenched upon the addition of UO₂²⁺,and the mechanism of fluorescence quenching was further investigated by mass spectrometry,nuclear magnetic resonance spectroscopy and infrared spectroscopy:（1）the addition of UO₂²⁺leads to partial depolymerization of TPE-ADX,which weakens the fluorescence;（2）the heavy atom effect of U.These two factors together lead to the fluorescence quenching of the system.The good coordination effect of UO₂²⁺by the amidoxime group in the structure of TPE-ADX not only achieved a fast response of 1 min,but also a low detection limit of 7.4 n M and good selectivity.Meanwhile,TPE-ADX was successfully used for the rapid detection of UO₂²⁺concentration in environmental water samples with good recovery.