Construction And Application Of Highly Selective Fluorescent Sensors Of Sulfur Dioxide Derivatives

Sulfur oxide?SO₂?,one of the main atmospheric pollutants produced by fuel combustion and industry,is easy to form two derivatives sulfites(SO₃^2-)and bisulfite?HSO₃^-?after dissolving to water.In vivo,SO₂ has unique biological activity,which is benefit to the reduction of blood pressure and vasodilation.And SO₂ as well as its derivatives can improve the water solubility of harmful substances,which is conducive to promote the elimination of harmful substances.It's worth noting that excessive sulfite,however,is detrimental to human,such as hypotension,migraines stroke,and diseases.Therefore,it is of great significance to develop a method that can specifically identify SO₂ derivatives and detect them high efficiency and accuracy.Benzothiazole compounds with good biological activity have special applications in antitumor drugs and anticancer drugs.In addition,its two structural forms,ketone type and enol type,can form excited state intramolecular transfer,which are well-known as fluorescent dye.They enjoy advantages of high fluorescence quantum yield,easy regulation of fluorescence,and good light stability.At present,some progress has been made in the design of the fluorescent probe of SO₂ derivative based on Michael's addition mechanism with benzothiazole as the fluorophore,but the ideal results are still far from being achieved.In this thesis,based on the previous reports,four D-?-A structure fluorescence sensors were constructed with three different electron-supplying units and benzothiazoles modified with iodized salt to detect SO₂ derivatives SO₃^2-and HSO₃^-.The effects of the structure of the donor unit on the optical performance and sensing performance of the four sensors were systematically studied,and the relationship between the structure and performance was revealed.Four types of fluorescence sensors with high selectivity,high sensitivity,and low detection limit were obtained,which are also applied to real sample detection,and achieved satisfactory results.1.Based on donor methylpyrrole unit and acceptor unit benzothiazole iodized salt,two kinds of D-?-A structure HSO₃^-fluorescence sensors PVBTI and HPVBTI were designed and synthesized.The two sensors can detect HSO₃^-in phosphate buffer salt solution based on Michael addition mechanism,and they are well verified by ¹H NMR and lc-ms spectra.The sensors PVBTI and HPVBTI showed good time response.After 5 minutes of addition of HSO₃^-,the fluorescence quenching was complete,and the introduction of cationic groups effectively avoided the interference of common cations in environmental samples.PVBTI and HPVBTI can detect HSO₃^-with low detection limits of 13.3 n M and 26.7 n M,respectively,which are more selective for HSO₃^-than other anions and cations.The two fluorescence sensors were used to detect HSO₃^-in tap water,lake water,river water and paddy field water,which indicates that PVBTI and HPVBTI can be used as practical sensing platforms for sensitive and high selective analysis of HSO₃^-in the environment.2.The donor unit with greater electron supply ability was introduced to effectively reduce the response time and detection limit of the sensor BCVTI,which provides a great opportunity for the development of HSO₃^-fluorescence sensor with higher sensing performance.The fluorescence sensor BCVTI has higher selectivity,and it is significantly higher for HSO₃^-than for other cations and anions,such as HS^-and SCN^-,etc.The reason is that the introduction of the electron-deficient group C=C for HSO₃^-.Besides,BCVTI is used as a visual detection sensor for HSO₃^-because of the high molar absorption rate.Thirdly,the introduction of benzyl carbazole reduced the response time to 4 minutes between BCVTI and HSO₃^-.And the fluorescence intensity was linearly correlated with the concentration of HSO₃^-,with the detection limit as low as 3.3 n M.Finally,we proposed that the sensor can be used to detect trace HSO₃^-in real samples with high precision.3.Amino unit with electron donor unit can effectively red shift the emission wavelength of the fluorescence sensor,and the red-emissive sensor ASHTI can effectively avoid the interference of the detection material's spontaneous fluorescence,improve the signal-to-noise ratio,and enhance the practical value of the HSO₃^-fluorescence sensor.Based on Michael addition mechanism,the D-?-A structure colorimetric fluorescence sensor ASHTI with red fluorescence is synthesized to minimize the background noise and thus improve the signal-to-noise ratio.The HSO₃^-specifically recognizes the C=C double bond of the offensive sensor,showing good selectivity and sensitivity with a detection limit of 0.27?M.Its sensing mechanism was confirmed by ¹H NMR and LC-MS spectra.In addition,the sensor ASHTI can be applied as a HSO₃^-detection test paper.The preliminary screening of HSO₃^-in the actual sample can be completed by visual observation,and the HSO₃^-in the sample can be accurately detected by fluorescence sensing.