The Study Of Fluorescent Probes Baed On Oligothiophenes And Salicylaldehyde Schiff Bases

Due to their advantages of high selectivity,simple synthesis and transient response,fluorescent probes are widely studied in medicine,biochemistry and environmental protection.Oligothiophene derivatives have good coplanarity,excellent luminescent properties,and electron transport channels.Salicylaldehyde derivatives have excellent liquid crystal properties and coordination groups.Therefore,oligothiophene and salicylaldehyde derivatives are good chromophores,which was great potential in the field of fluorescence detection.Therefore,fluorescent probes based on oligothiophene and salicylaldehyde derivatives were designed and synthesized.The contents are as follows:The research significance of fluorescent probes and the mechanism of recognition are briefly described in the first chapter.A novel oligothiophene-based dual-mode chemosensor A3TA was designed and synthesized for Fe³⁺and Hg²⁺in aqueous media.The sensor A3TA showed high selectivity and sensitivity toward Fe³⁺and Hg²⁺.Hg²⁺was detected by changing color from khaki to reddish brown,could be easily distinguished by bare eyes.The detection limits for Fe³⁺and Hg²⁺were found to be as low as 3.52×10^-8and 5.0×10^-8M,respectively.The stoichiometric ratio of the sensor toward Fe³⁺/Hg²⁺ions was obtained to be 1:2.In addtion,the sensing mechanism was investigated in detailby fluorescence spectroscopy,¹H NMR titrations,FT-IR and HRMS spectra analysis.A novel oligothiophene-based naked-eye colorimetric and fluorescent turn-on sensor 3TT with a typical donor-?-acceptor structure has been successfully developed,which displayed excellent selectivity and sensitivity for the dual-channel detection of toxic cyanide?CN^-?in 70%aqueous THF media.The cyanide sensing mechanism was con-firmed by optical spectral studies,FT-IR spectra,¹H NMR titration,HRMS spectra and DFT calculations.Sensor 3TT for the naked-eye detection of CN^-in aqueous media exhibited high anti-interference ability,extremely low detection limit?39.9 nM?as well as wide pH response range.Moreover,sensor 3TT displays excellent sensing performance in the solid state,and 3TT was successfully applied to the rapid detection of cyanide in real water samples,bitter seeds and food samples,demonstrating its great potential for practical applications in our daily life and environment.A new simple and multi-responsive colorimetric and fluorescent probe with aggregation-induced emission?AIE?characteristic has been designed and synthesized.The probe ADC showed turn-on fluorescent response to zinc and cyanide ions(Zn²⁺and CN^–)and fluorescence quenching behavior to copper ion(Cu²⁺),which induces obvious naked-eye color changes,respectively.The probe ADC for Cu²⁺/Zn²⁺/CN^–detection displayed fast response time and low detection limits of1.6×10^–6,1.3×10^–88 and 8.1×10^–77 M,respectively.The sensing mechanisms were confirmed by ¹H NMR titration spectrum.A simple,reversible,colorimetric andwater-soluble fluorescent chemosensor ADA for the naked-eye detection of Cu²⁺was developed.Sensor ADA showed high selectivity and sensitivity toward Cu²⁺in¹00%aqueous media over wide pH range.Sensor ADA exhibited a red-shift in the absorption spectra from466 to 480 nm that is accompanied by significant color change from light yellow to yellowish brown instantaneously.The lowest detection limit is determined to be 15.8 nM,which is much lower than the allowable level of Cu²⁺in drinking water set by U.S.Environmental Protection Agency?²0?M?and the World Health Organization?³0?M?.Moreover,sensor ADA was successfully applied for determination of trace level of Cu²⁺with 4reuse cycles in various water samples,which affords promising potential in ion-detection field.A new simple and efficient fluorescent sensor L based on 1,8-diaminonaphthalene Schiff-base for highly sensitive and selective determination of Cu²⁺in drink and water has been developed.This Cu²⁺-selective detection displayed an obvious color change from blue to colorless easily detected by naked eye.The 1:1 binding mechanismwas well confirmed by fluorescence measurements and IR analysis.Importantly,this sensor H was employed for quick detection of Cu²⁺in drink and environmental water samples with satisfactory results,providing a simple,rapid,reliable and feasible Cu²⁺-sensing method.A simple highly sensitive and selective turn-on fluorescent chemosensor L based on bis-Schiff-base for Pb²⁺ions was synthesized and characterized by spectroscopic techniques.L having high binding affinity towards Pb²⁺ions selectively detects Pb²⁺ions with almost no interference among various competitive ions by a 11-fold fluorescent enhancement in CH₃CN/H₂O solution.Moreover,sensor L displayed a lower detection limit of 3.80×10^-7M,which is low enough for sensing sub-millimolar concentration of Pb²⁺encountered practically.