Synthesis Of AIE-ESIPT Type Fluorescent Probes And Their Application In Hydrogen Sulfide And Sulfite Detection

Fluorescent probes based on the aggregation-induced luminescence（AIE）effect or the excited state intramolecular proton transfer（ESIPT）effect have attracted much attention in recent years because the AIE effect can overcome the shortcomings of quenching in the aggregated state of conventional dyes,while bringing the advantages of high quantum yield and high stability.The introduction of ESIPT effect can effectively increase the Stokes shift of the fluorescent probe and improve the detection signal-to-noise ratio and sensitivity.However,fluorescent probes employing both effects are still very scarce.In this study,a fluorescent dye with both AIE and ESIPT effects has been designed and synthesized,and two fluorescent probes were further fabricated using this dye for the detection of hydrogen sulfide and sulfite.The main contents are as follows:（1）The AIE-ESIPT type fluorescent dye TPA-TP based on triphenylamine group and 2-（2’-hydroxyphenyl）benzothiazole group was designed and synthesized.The structure of TPA-TP has been characterized,and the spectral properties have been measured.TPA-TP molecules exist in the aggregated state in poor solvents,and the rotation of the benzene rings within the molecule is restricted,thus emitting bright orange fluorescence with a large Stokes shift reaching 215 nm.At the same time,TPA-TP has good stability and is suitable for further development into fluorescent probes.（2）An enhanced AIE-ESIPT-type fluorescent probe TPA-H₂S,which can be used for the detection of hydrogen sulfide,was obtained by reacting the fluorescent dye TPA-TP with 2,4-dinitrofluorobenzene as a substrate.2,4-Dinitrophenoxybenzyl serves as both the fluorescence quenching group and the specific recognition group for hydrogen sulfide.The probe TPA-H₂S has been characterized,and its capability for H₂S detection has been investigated.Before it responds to hydrogen sulfide,the fluorescent probe TPA-H₂S was basically not observed to fluoresce.However,after the response,the recognition group is removed and bright orange fluorescence is given out,thereby realizing the detection of hydrogen sulfidewith a detection limit of 0.19μM.In addition,the fluorescent probe TPA-H₂S has low cytotoxicity and can be used for the detection and imaging of exogenous hydrogen sulfide in living cells.（3）A ratiometric AIE-ESIPT-type fluorescent probe TPA-SO₂,which can be used for sulfite detection,was obtained by reacting the fluorescent dye TPA-TP with levulinic acid as a substrate.levulinic acid ester acts as a specific recognition group for sulfite ions,replacing the phenolic hydroxyl group while turning off the ESIPT effect.The probe TPA-SO₂ has been characterized,and its capability for SO₂detection has been investigated.The probe TPA-SO₂before the response can only emit blue fluorescence,and after the response to the sulfite ion,the ESIPT effect is activated and bright orange fluorescence is re-emitted.The detection limit of the fluorescent probe reaches 0.88μM.Similarly,the fluorescent probe TPA-SO₂ has low cytotoxicity and can be used for the detection and imaging of exogenous sulfite in living cells.