Synthesis And Properties Of Fluorescence Probes For Mercury Ion

Relative to other metal ions,mercury is well known as one of the most toxic metals because of their durability,easy transference and high biological accumulation.Because of human activities such as coal-fired power plants and gold mines,mercury and mercury species are continuously discharged into the environment,which poses an indispensable threat to human health and the environment.For this reason,the development of selective and sensitive detection methods for mercury is still highly necessary.Traditionally,inductively coupled plasma mass spectrometry,atomic absorption spectroscopy and capillary electrophoresis have been used to analyze Hg2+levels in environmental samples.However,these instrumentally intensive methods not only require expensive intricate instrumentation,but also require complex sample preparation.Different from the traditional analyses,as one of the promising detection methods,fluorescent probes have been developed to be a powerful tool in numerous applications,such as chemical sensing,environmental science,biological imaging and medical diagnosis because of their high specificity and sensitivity monitoring with fast response.Therefore,the development of fluorescent probes that can selectively and sensitively detect mercury ions is of great importance.In this thesis,we designed and synthesized three kinds of fluorescent probes that can be used to identify and visualize mercury ion in real water samples,and studied the properties of probes.The main content of this paper can be summarized the following three points:(1)Seven kinds of dibenzamide derivatives modified sulfide were synthesized.The specificity of fluorescent probes for Hg2+ and Fe3+ was studied.The experiment data displayed the o-hydroxyl-attached probe lb exhibited selective 'turn-off"fluorescence response to Fe3+,and the o-amino-attached probe 1c selectively recognized Hg2+ by fluorescence quenching quickly.According to the Job plot and ESI mass spectrometry,combined chemometrics was ensured,1b and Fe3+ form 1:1 lb-Fe3+ complexes,1c and Hg2+ are coordinated to 1:2(1c-Hg2+)complex.The minimum detection value of lb for Fe3+ and 1c for Hg2+ were worked out to be 0.3?M and 0.5?M by fluorescence titration,respectively.In addition,density functional theory(DFT)and natural bond orbital(NBO)analysis are used to study geometric structure and its working principles,showed that the fluorescence quenching was created by ICT.Both probes 1b and 1c could detect Fe3+ or Hg2+ in drinking water.(2)A long-wavelength fluorescent probe OTA-DCM was designed and synthesized,which contained a conjugated dicyanomethylene-4H-benzopyran structure as the long-wavelength fluorophore and dithia-dioxa-monoaza crown ether moiety as the recognition unit Through UV absorption and fluorescence spectroscopy,the probe exhibited superior analytical performance,such as a remarkable large Stokes shift(120nm),fast response for ions.The studies showed that OTA-DCM probe had excellent selectivity and the recognition for Hg2+ wasn't interfered even in the presence of other ions.It could detect quantitatively Hgig by the absorption and fluorescence spectrometry methods with excellent sensitivity over various other metal ions,and the minimum detection value for Hgig was 0.14 ?M.The sensing mechanism was investigated by optical spectrum and NMR spectra.The data indicated that the probe has good binding constant(1.05×104 M-1)for Hg2+ ion with the formation of 1:1 complexes.Probalely,S,N,O in crown was as electron donor to be coordinate to Hg2+,especially S and N.The probe also showed good reversible response to Hg2+ in a board pH range.Importantly,the color of the solution changed from rose red to yellow upon addition of Hg2+,which meant the probe could serve as a "naked-eye" visual indictor.Moreover,the probe could detect Hg2+ in real samples.Finally,through cytotoxicity tests,it was further shown that the probe had good biocompatibility and no toxical effect,which meant it had potential development prospects in the detection of Hg2+ in living cells.(3)A novel hemicyanine-based near-infrared fluorescent probe for Hg2+ was designed.By coupling phenyl thioxochloroformate as the recognition unit with a stable hemicyanine skeleton through an ester bond,the probe was readily prepared.The selectivity,interference,pH,temperature and other properties of the probe were studied through UV absorption and fluorescence spectroscopy.In the DMSO(20%,pH=7.4)buffer,in the absence of Hg2+,the free Cy-PT had almost no fluorescence because of the intermolecular charge transfer(ICT)possess.Upon reaction with Hg2+,the protected hydroxyl group on the Cy-PT was liberated,leaded to the significant enhancement of fluorescence.In addition,the probe can be used to detect Hg2+ over other various metal ions with high selectivity and sensitivity in aqueous solution under physiological pH and mild conditions.After adding mercury ions,the color of solution transformed from indigo into lake blue,which could serve as a "naked-eye"visual indicator.Finally,through cytotoxicity tests,it was shown that the probe had good biocompatibility and no toxical effect,which meant it also had potential development prospects in the detection of Hg2+ in living cells.