Design,Synthesis And Properties Of Fluorescent Probes For Hydrogen Peroxide And Mercury Ion

The concern on human health makes us pay more attention to environmental pollution.Hydrogen peroxide（H₂O₂）and mercury ion(Hg²⁺)are two kinds of toxic and harmful substances in the environment.Excessive H₂O₂ and Hg²⁺can not only destroy ecological environment,but also disrupt the redox balance in human beings,resulting in cellular oxidative damage,the disorder of central nervous system,digestive system and multiple organ failure,even leading to Alzheimer’s disease,tumor,cardiovascular disease,Huntington’s disease,Parkinson’s disease and other diseases.Therefore,it is urgent to accurately monitor H₂O₂ and Hg²⁺in the environment.Herein,two novel fluorescent probes HBTH and MTRH were designed and synthesized with simple procedures for specific recognition of H₂O₂ and Hg²⁺respectively,to overcome the shortcomings of existing instrumental analysis techniques including the necessity of expensive instruments,complicated pretreatment procedures,long detection time,and the inability in bioimaging.The fluorescent probes had been successfully applied in the detection and bioimaging of H₂O₂ and Hg²⁺in the environment and human microenvironment due to the excellent properties such as high sensitivity,rapid response,and good biocompatibility.Firstly,a ratiometric NIR fluorescent probe HBTH with large Stokes shift was synthesized based on ESIPT mechanism for the detection of H₂O₂.In the solution of PBS/CH₃CN（7:3,v/v,10 m M,p H=7.4）,HBTH exhibited excellent sensitivity and selectivity for H₂O₂ in fluorescence detection,with the detection limitation(2.9×10^-8M).Common coexisting species,including ions,biological thiols and reactive oxygen species（ROS）,did not interfere with fluorescence recognition.Meanwhile,HBTH also owned the perfect properties such as relatively rapid response（15 min）,good biocompatibility and large emission shift（143 nm）,which could effectively reduce the influence of fluorescence self-quenching and improve the detection accuracy.The mechanism of HBTH towards H₂O₂ was investigated by electrospray ionization mass and DFT/TDDFT theoretical calculation.The capability for HBTH as a promising chemosensor for H₂O₂ had been proven by the successful application of HBTH in the detection of H₂O₂ in real water samples with satisfying recovery（93.3%～110.5%）and low relative standard deviation（RSD）（0.55%～7.50%）and fluorescence imaging of exogenous and endogenous H₂O₂ in cells,zebrafish and mice.Secondly,a novel“turn-on”fluorescent probe MTRH for Hg²⁺was designed and synthesized by a simple two-step reaction.MTRH showed good fluorescence selectivity and sensitivity to Hg²⁺in pure aqueous media with ultra-low detection limit(1.3×10^-9M).Moreover,the probe owned the ability of visualizing Hg²⁺by the distinct color change of the solution（colorless to pink）.The corresponding recognition mechanism was investigated by Job’s plots,mass spectrometry and DFT calculation analysis.Importantly,the characteristics such as high sensitivity,low cytotoxicity and good biocompatibility of MTRH exhibited in the application of detecting Hg²⁺in real water sample and bioimaging of intracellular Hg²⁺prove that MTRH is a promising tool to evaluate the levels of Hg²⁺in complex biological systems.