Design,Synthesis And Detection Mechanism Research Of Multifunctional Fluorescent Probes

Mercury pollution is a fatal hazard to our health and environment.In addition,hypochlorous acid（Cl O^-）is a common reactive oxygen species in human body,and its abnormal concentration is often an important signal of some serious diseases.Fluorescent probes with the advantages of high selectivity,high sensitivity,simple operation,real-time monitoring and good reproducibility are widely used in biosensing and imaging fields.Most mono-functional fluorescent probes which only can detect one substance have limitations in detecting multiple species.In this paper,we designed and synthesized novel fluorescent probes with good water solubility and long emission wavelength,which can realize the monitoring of Hg²⁺and Cl O^-.Its sensing performance and recognition mechanism have been studied by hydrogen spectroscopy,high-resolution mass spectrometry,and density functional theory calculations.The main research contents are as follows:First,we designed and synthesized a dual-functional fluorescent probes2-amino-3-（（（E）-（5-（9-phenyl-9H-carbazol-3-yl）thiophen-2-yl）methylene）amino）maleonitrile（abbreviated as FDW）,which can be used not only for selective identification of trace Hg²⁺,but also for fluorescence imaging of Cl O^-.After adding a trace amount of Hg²⁺,under the irradiation of UV lamp,FDW showed a change in fluorescence color from dull to yellow-green easily distinguishable.High selectivity,high sensitivity,and fast response time（6 minutes）have been achieved.In addition,Hg²⁺can coordinate with FDW,and the C=N bond of the schiff base is elongated,which weakens the binding ability of C=N.Making it easy to break down and the Hg²⁺is released under UV irradiation,the FDW becomes SH,and the fluorescence emission is gradually enhanced,which we reported this phenomenon for the first time.In addition upon the addition of Cl O^-into FDW solution,the blue emission was significantly increased along with the color change from pale yellow to colorless,which could be easily distinguished by naked eyes.The emission intensity of FDW at 516 nm showed a good linear relationship with the concentration of Cl O^-（0-240μM）,and the detection limit for Cl O^-was 107 n M.In addition,FDW can be further used for fluorescence imaging of Cl O^-in RAW 264.7 cells.Then,we further synthesized a novel near infrared fluorescent probe（E）-O-（4-（2-（3-（dicyano）-5,5-dimethylcyclohexene-1-yl）vinyl）phenyl）o-phenyl thiocarbonate（ICM-Hg）for the detection of Hg²⁺.After the addition of Hg²⁺,ICM-Hg changed from pale yellow fluorescence to orange fluorescence,at the same time,the color of the solution changed from colorless to pale yellow,realizing dual sensing of fluorescence and colorimetry.With the increase of Hg²⁺concentration in the detection system,the emission wavelength of the probe is further shifted to red,the thiocarbonyl（C=S）bond is broken,and ICM-Hg becomes 2-(3-（4-hydroxystyryl-5,5-Dimethylcyclohex-2-enyl）malononitrile（ICM-OH）.The sensing mechanism of ICM-Hg for Hg²⁺was strongly demonstrated by hydrogen nuclear magnetic resonance spectroscopy（¹H NMR）,ultraviolet-visible absorption spectroscopy（UV-Vis）and fluorescence spectroscopy.Importantly,the ICM-Hg was successfully applied to the imaging of Hg²⁺in live cells and zebrafish embryos,and its utility was verified in real samples.