Synthesis And Performance Studies Of Near-Infrared Fluorescent Probes For Bisulfite

The rapid development of industry has led to a sharp increase in the content of sulfur dioxide（SO₂）in the atmosphere.And,a considerable part of SO₂will translate into the form of salts such as sulfate or bisulfite(SO₃^2–/HSO₃^–)with the help of solid/liquid water.Subsequently,they migrate and transform in the environment and will cause certain harm.In addition,special industrial wastewater such as coking wastewater contains more SO₃^2–/HSO₃^–.If these wastewaters are discharged into natural world without effective treatment,they will cause great damage to the local ecological environment.When SO₃^2–/HSO₃^–were ingested by humans along the food chain,they can change the thiol level,hinder the redox balance and damage the nervous system to cause a variety of respiratory and circulatory diseases.Therefore,it is particularly important to investigate specific detection methods for SO₃^2–/HSO₃^–used in environmental and biological fields.Based on the advantages of high selectivity and sensitivity,real-time monitoring and higher tissue penetration of near infrared（NIR）fluorescent probe,three NIR fluorescent probes（ZTX-1,ZTX-2 and ZTX-3）for HSO₃^–were designed and synthesized.Due to the high nucleophilicity of HSO₃^–,it attacks to the carbon-carbon double bond（C=C）of three probes by the Michael addition reaction,which destroys theπ-conjugation in the probes and blocks the intramolecular charge transfer（ICT）process,resulting in the observable spectroscopic responses.After spectroscopic testing,it was found that all three probes have specific recognition ability for HSO₃^–,and their recognition effect was not disturbed in the presence of thiols,reactive oxygen species and other anions.The three probes show high kinetic stability and are appropriate for the detection of HSO₃^–within a broad p H range.Through colorimetric analysis under natural light,the"naked eye"recognition ability of all three probes was verified.The detection limits of probe ZTX-1 and ZTX-3 were calculated to be 5.52μM and 0.049μM,respectively,indicating that they can be applied to the detection of trace HSO₃^–in complex environments and biological systems.Subsequently,through the front orbit theory,the distribution change of the electron cloud,the value of the change of the energy level and the phenomenon in the spectroscopic responses were analyzed.The three NIR fluorescent probes have been used for the detection of HSO₃^–by fluorescence imaging.Furthermore,the three probes have been prepared into test paper,which successfully used for the level of HSO₃^–in actual water samples by“naked eye”.