| Currently, there have been a large number of fluorescent probes for gas molecules, which mainly include some environmental pollutants such as SO2, NOx, small biological signal molecules such as NO, H2S, HNO, toxic gases such as nerve gas, mustard gas and so on. The concentration of these molecules in the environment or in vivo is closely related to biological systems. Therefore, the investigation of the properties and mechanism of these gases has attracted researchers’great interest. For this reason, three fluorescent probes were designed for selective detection of three typical small molecules, SO2, HNO, DCP (a simulated molecular of nerve gas) in this paper. The paper mainly includes four chapters and is listed as follows:In chapter 1, the physical and chemical properties, physiology and pathology process, and a generation introduction to the research progress on the development of fluorescence detection methods for some typical small gas molecules were described. On the basis of the corresponding literatures, the objective of this dissertation was proposed.In chapter 2, a ratiometric coumarin-benzopyran conjugated system for detecting sulfite was constructed and investigated. Based on nucleophilic reaction mechanism between sulfite and benzopyrylium, we designed a new ratiometric fluorescent probe Ⅱ-l for sulfite. Due to the large π conjugated system of the probe, it shows strong fluorescence at 640 nm. Upon reaction with SO32-, a nucleophilic reaction between SO32- and benzopyrylium occurred, and the large conjugated system was interrupted, which in turn leads to the whole system afford coumarin fluorescence emission at 485 nm. The fluorescence intensity ratio at 485 nm and 640 nm (I485/I640) showed a good linear relationship with sulfite concentration in the range of 0.05-10μM. Moreover, a ratiometric fluorescence imaging of SO32- in HepG2 cells has been performed successfully.In chapter 3, a new fluorescence sensing system for nitrosyl (HNO) was developed. Based on the nucleophilic attack of the thiol to HNO, we developed a new method for detecting HNO.2-(2’-hydroxy-3-methoxyphenyl) benzothiazole (HMBT) exists intromolecular ESIPT process in the excited light, so the molecule displays enol-like and keto-like fluorescence emission. Accordingly, we designed and synthesized two fluorescent probes Ⅲ-2 and Ⅲ-4 for HNO by using 2-(2’-hydroxy-3-methoxyphenyl) benzothiazole (HMBT) as fluorophore. Since the hydroxyl was esterified, the intromocular ESIPT process of HMBT was blocked, and it only displays enol-like fluorescence emission. Upon reaction with HNO, the thiol attacks nitrosyl to form a sulfonamide moiety. Its amino group is nucleophilic and can attack the ester group in proximity, and the free hydroxyl is released, thus the ESIPT process of HMBT being retrieved, accompanied by the keto-like fluorescence emission. Based on the above mechanism, we can detect HNO quantitively and selectively. Probe Ⅲ-2 and Ⅲ-4 show a good linear relationship with nitrosyl concentration in the range of 0-10 μM and 0-20 μM, respectively. This method provides a new strategy for the construction of fluorescent probes for HNO in vivo.In chapter 4, a ratiometric coumarin-benzopyran conjugated fluorescent system Ⅱ-1 for detecting nerve gas was preliminary studied. Due to the high toxicity of nerve gas, diethyl chlorophosphate (DCP), an organophosphonate simulated molecule of nerve gas was used to mimic the nerve gas in the experiment. Based on nucleophilic attack of hydroxy to organophosphorus, a new fluorescent probe Ⅱ-1 was designed for detection of DCP. Firstly, we compared the fluorescence property of the probe Ⅱ-1 and IV-1, and found that the fluorescence emission maximum of Ⅱ-1 is at 640 nm, while the fluorescence emission maximum of Ⅳ-1 is at 480 nm, which indicates that 7-OH of probe Ⅱ-1 can affect the whole molecule’s fluorescence behavior significantly. Thus, we envisioned that if the hydroxyl group of Ⅱ-1 is modified, the fluorescence behavior of the probe should be changed accordingly. Specifically, when a nucleophilic reaction between Ⅱ-1 and DCP occurs, the hydroxyl of Ⅱ-1 is protected, accompanied by the fluorescence emission maximum shifts from 640 nm to 510 nm. Based on the fluorescence changes of the reaction system, it can be concluded that probe Ⅱ-1 is suitable for the ratiometric sensing of DCP. |
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