Construction And Application Of Small Molecule Fluorescent Probes Based On AIE And ESIPT Effect

Fluorescent probes are effective analytical tools for studying physiological processes in living systems,and traditional aggregation-induced quenching（ACQ）fluorophores have low luminescence efficiency and poor labeling sensitivity,while aggregation-induced fluorescence（AIE）probes solve such problems.With the understanding of the AIE process and the in-depth study of the luminescence mechanism,the advantages of the enhanced fluorescence emission of the AIE mechanism can be used to avoid the defects of the probe molecule.In this paper,we designed a series of novel fluorescent probes based on the excited state intra-molecular proton transfer（ESIPT）or AIE mechanism,which exhibit excellent photochemical properties,good biocompatibility,responds quickly,high sensitivity,and are further successfully applied to the detection of sulfur-containing small molecules and reactive oxygen species in living systems.The specific research are as follows:1.A fluorescent probe 1 with AIE properties was synthesized in one step base on 4-acetylaminobenzaldehyde and hydrazine carbonate.The AIE properties of probe 1 were discussed by fluorescence emission spectroscopy,UV spectroscopy,particle size particle size analysis,scanning electron microscopy and DFT theoretical calculations,and the luminescence mechanism of the probe was proved to be the ESIPT effect.Probe 1 can quantitatively detect H₂S in the range of 0-25μM in the DMSO/H₂O（1/9,V/V）,p H=7.4（PBS,0.2 M）system with a detection limit of 0.27μM.In addition,Probe 1 has been successfully used not only for the detection of H₂S in wine samples,but also for the exogenous H₂S in live Hela cells.Most importantly,a simple,portable and economical detection test paper was prepared using Probe1,which is capable of real-time and effective semi-quantitative detection of H₂S.This study is expected to provide new ideas and methods for the reliable and effective detection of H₂S in various physiological processes and food samples.2.A D-π-A type near-infrared aggregation-induced fluorescent probe DPA-CN was constructed base on diphenylamino-4-benzaldehyde and malononitrile,which rapidly recognizes SO₂ molecules based on the Michael addition mechanism,enables sensitive colourimetric detection of SO₂ molecules with a fluorescence change from red(λ_em=650 nm)to yellow(λ_em=560 nm).The identification mechanism was verified by nuclear magnetic resonance（¹H NMR）,electrospray mass spectrometry（ESI-MS）,scanning electron microscopy（SEM）,and dynamic light scattering（DLS）.The sensing performance of the probe for SO₂ was tested by spectral analysis under the optimized experimental conditions.The results showed that the probe DPA-CN can rapidly and specifically identify SO₂ within 10 s at concentrations ranging from 0-100μM,with a detection limit as low as 0.31μM.Based on the high sensitivity and low toxicity of the probe,the detection of HSO₃^-in real environmental samples and the monitoring and identification of SO₂ in living cells were successfully achieved.Based on the high sensitivity and low toxicity of the probe,the detection of HSO₃^-in in food and environmental samples and the monitoring and identification of SO₂in living cells were successfully achieved.In addition,the probe was used to prepare an inexpensive,easy-to-use,bare-eye visible,ultra-fast,semi-quantitative paper-based sensor for SO₂ gas.3.A novel fluorescent probe HBT-B with high efficiency was synthesized based on the one-step method of 2-（2-hydroxyphenyl）benzothiazole,and the luminescence mechanism of the probe was investigated by fluorescence emission spectroscopy,UV spectroscopy,particle size analysis,nuclear magnetic resonance（¹H NMR）and electrospray ionization mass spectrometry（ESI-MS）,etc.The luminescence mechanism of the probe was investigated by excited state intra-molecular proton transfer（ESIPT）effect.Probe HBT-B quantifies H₂O₂ in the range of 0-80μM in the DMSO/H₂O（1/99,V/V）,p H=7.4（PBS,0.2 M）system with a detection limit of 0.27μM.In addition,paper-based sensors were prepared using the probe HBT-B.This study is expected to provide a reliable and effective new idea for the sensitive monitoring of H₂O₂ in living systems.