Design,Synthesis And Photophysical Properties Of Salamo Type Chemical Sensors

Fluorescent chemical sensors as a research hotspot in recent years,have been widely used in the fields of environmental monitoring and life sciences.Based on this,five Salamo-type colorimetric and fluorescent dual-channel chemical sensors were synthesized for the detection of cyanide（CN^-）or hydrazine（N₂H₄）.Through related physical and chemical characterization and theoretical calculation,the recognition mechanism is systematically analyzed,which provides a certain experimental and theoretical basis for the further research of Salamo-type chemical sensors.The main content is divided into the following four chapters:1.The structural composition and common recognition mechanism of chemical sensors are briefly introduced,and the research progress of chemical sensors in the field of recognition is listed in detail.2.Through a simple condensation reaction,two Salamo-type chemical sensors（NTS and DNTS）have been developed.Among them,only the NTS molecule exhibits strong solid-state luminescence properties,and spectral data indicate that this molecule has aggregation-induced luminescence enhancement（AIEE）properties.By analyzing the single crystal structure data of NTS molecules,it is speculated that the AIEE phenomenon is caused by the J-aggregation mechanism.Further research found that both the chemical sensors NTS and DNTS can identify highly toxic CN^-ions with high selectivity.In DMSO/H₂O（9/1,V/V,p H=7.0）solution system,the sensors NTS and DNTS,which have no fluorescence emission,can produce strong green fluorescence emission after interacting with CN^-ions,and the color of the solution changes from colorless to light yellow when observed with the naked eye.The response time of the two sensors to CN^-is no more than 3 seconds,and their detection limits are 2.16×10^-7 mol/L and 2.18×10^-7 mol/L,respectively.The prepared sensors NTS and DNTS can be recycled for 3 times without affecting the recognition effect.Besides,through the test strip test and the detection of trace amounts of cyanide in food raw materials,it has been confirmed that this type of sensor has good practical application value.3.A novel bifunctional-group multifunctional dye sensor p-NTS with solvent dependence was designed and synthesized.The sensor p-NTS molecules show yellow and green solid-state fluorescence under visible light and ultraviolet light（365 nm）,respectively.The sensor molecule contains unique excited state intramolecular proton transfer（ESIPT）and resonance assisted hydrogen bonding（RAHB）systems,which can detect cyanide（CN^-）and hydrazine（N₂H₄）by blocking the ESIPT effect,and the RAHB effect effectively enhances the activity of aldehyde groups,thereby quickly detect the target substance.Cyanide can change the fluorescence color from green to bright orange-red（116 nm Stokes red shift）,while hydrazine can cause the quenching of green fluorescence,and other interfering substances will basically not affect the recognition process.Through spectral characterization and theoretical calculations,a possible recognition mechanism is proposed.The sensor p-NTS can be prepared as a test strip for the detection of cyanide and hydrazine.In addition,the sensor p-NTS can also be used to detect trace cyanide in agricultural products,and detect gaseous hydrazine by direct contact,indicating that the sensor p-NTS has a good practical application prospect.4.Using benzophenone as the starting material,monoaldehyde and dialdehyde molecules with tetraphenylethylene as the skeleton were synthesized,and then two novel Salamo-type chemical sensors（TPES1 and TPES2）were obtained through simple condensation reactions.Both sensor molecules can specifically recognize CN^-in numerous analytes by turning on fluorescence.The sensors TPES1 and TPES2exhibit completely different spectral phenomena during the recognition process.Among them,the TPES1 is a ratio fluorescence sensor,and a double fluorescence emission peak appears during the titration process.This is due to the rotation of C-C single bond in tetraphenylethylene,resulting in the existence of two modes of molecules in the solution system.TPES2 is a fluorescence enhanced sensor,which goes through two reaction processes of dehydrogenation and nucleophilic addition,leading to the continuous increase of fluorescence intensity.The process of CN^-recognition by the two sensors can be directly observed through the dual-channel mode with colorimetric and fluorescence turned on.A test strip for the sensor TPES2was also prepared for the rapid and simple detection of CN^-ions.