Novel Sensing Interfaces For Persistent Organic Pollutants With Structure Of Brominated Aromatic Ring And Their Applications In Sensitive Determination

Persistent organic pollutants?POPs?are a series of compounds which possess typical characteristics such as long half-life due that they resist photolytic,chemical and biological degradation,high toxicity,long-range transport and tendency to accumulate in organism.POPs mainly contain halogenated aromatic hydrocarbons,polychlorinated dibenzo-p-dioxins?PCDDs?and polychlorinated dibenzofurans?PCDFs?etc.Recently,polycyclic aromatic hydrocarbons have also been classified as persistent organic pollutants.Upon emerging into environment,they can exist for a long period due to high physical and chemical stability,and possess some disturbing effects on the ecological system.POPs often cause significant adverse effects on animal and human health,leading to endocrine disruption,reproductive and immune dysfunction,neurobehavioral and disorder,cancer,obesity and diabetes etc.Brominated aromatics are extensively used as flame retardant in industries,and are also belong to persistent organic pollutants due to their properties are similar to each other.The distributions of brominated aromatic hydrocarbons were almost over worldwide.They can be detected in atmosphere,dust,water,soil,glacier,and sediment etc.They have tendency to accumulate in food chains,and can be easily transferred into animal and human body,causing serious toxic effects such as hepatotoxicity,embryotoxicity,thyroidogenic and estrogenic effects,and behavioral effects etc.Therefore,to protect environmental safety and human health,it will be very important to develop novel analytical methods for determining brominated aromatics with high sensitivity,selectivity and fast speed.In this dissertation,three types of brominated aromatics including 4,4'-dibromobiphenyl,tetrabromobisphenol A,tribromophenol were selected as target POPs for fabricating novel electrochemical and photoelectrochemical sensing platforms based on the enhanced effects of nanomaterials and molecularly imprinted technique to improve electrochemical and photoelectrochemical sensing performances.The mechanisms for the selective recognition and the signal enhancing were investigated thoroughly.Novel electrochemical and photoelectrochemical methods were developed successfully,and were applied for the accurate determination of these compounds in real samples.All investigations were presented in the following five sections:?1?Impedance sensing platform for 4,4'-dibromobiphenyl based on molecular imprinting1-Vinyl-3-butyl-imidazolium hexafluorophosphate?VBimPF6?ionic liquid was successfully synthesized and characterized with 1H-NMR and FTIR.VBimPF6was used as a functional monomer for fabricating an imprinted film on a gold nanoparticles modified glassy carbon electrode by using 4,4'-dibromobiphenyl?DiBB?as template,ethylene glycol dimethacrylate?EGDMA?as crossing-linker,ammonium persulfate and tetramethylethylenediamine as initiator.After removing the DiBB template,an imprinted electrochemical sensor was obtained for DiBB with high specific recognition sites.Electrochemical impedance spectroscopy was used to characterize the sensing performances of the developed imprinted film electrode.It was found that the imprinted film possesses high selectivity and sensitivity towards DiBB,and can be used for DiBB determination.Under optimized experimental conditions,the variation of the charge transfer resistance of the imprinted film electrode before and after being interacted with DiBB was found linearly related to the logarithm of DiBB concentration in the range from 0.005 to 10.0 ?mol L-1.The detection limit was calculated to be 0.001 ?mol L-1?S/N = 3?.The developed imprinted film electrode was demonstrated possessing a potential application in determining DiBB in soil sample.?2?Self-assembled gold nanorods on a poly-cysteine film electrode to enhance the electrochemical sensing of tetrabromobisphenol ACysteine?Cys?was electrochemically deposited on a glassy carbon electrode?GCE?surface by cyclic voltammetry.The poly-Cys modified electrode was incubated in a solution of gold nanorods?AuNRs?to induce self-assembly of the AuNRs.The AuNRs/poly-Cys/GCEs were characterized by scanning electron microscopy and electrochemical impedance spectroscopy.A voltammetric study on tetrabromobisphenol A?TBBPA?with AuNRs/poly-Cys/GCEs showed the current response has been enhanced by a factor of 11 compared to a non-modified GCE.Based on these findings,a square wave voltammetric assay was developed.Under optimized conditions,a linear relationship can be found between the oxidation peak current and TBBPA in the concentration range of 0.01?1.0 and 1.0?10.0 ?mol L-1.The detection limit is 3.2 nmol L"1?at an S/N ratio of 3?.The electrode was successfully applied to determine TBBPA in spiked tap water and lake water samples.?3?Electrochemical sensing of tetrabromobisphenol A based on the enhanced effect of polymerized ionic liquidPyrrole moiety functionalized ionic liquid,1-[3-?N-pyrrole?propyl]-3-butyl-imidazolium tetrafluoroborate[PPBimBF4],was synthesized and fully characterized with NMR,FTIR and HPLC-MS.Then,it was used as a functional monomer to fabricate an electrochemical sensing platform by in-site polymerizing on a glassy carbon electrode surface with voltammetric technique.Subsequently,an anion exchange process was performed in a sodium dodecyl sulfonate solution to fabricate a polymerized ionic liquid film based electrode.The interface was characterized with electrochemical impedance spectroscopy and SEM.Electrochemical behaviors of tetrabromobisphenol A were investigated.The effects of anion on the oxidation peak current of tetrabromobisphenol A were also studied,and demonstrated that the polymerized ionic liquid film that has been treated with sodium dodecyl sulfonate can give a significant enhanced effect on the sensing performances.Experimental conditions including the film thickness,pH values,accumulation potential and time were optimized.Under optimal conditions,the oxidation peak currents were found linearly related to tetrabromobisphenol A concetrations in the range from 0.05 to 10.0 ?mol L-1.The detection limit was calculated to be 0.02 pmol L-1?S/N =3?.The practical applications of the polymerized ionic liquid film electrode were demonstrated by determining spiked tetrabromobisphenol A in South-Lake water.The good recoveries indicated that the developed sensor possesses excellent accuracy in real sample assay.?4?Photoelectrochemical immunosensor for tetrabromophenol A based on MoS₂ nanosheets integrated with dodecahedral gold nanocrystalsDodecahedral gold nanocrystals?AuNCs?were synthesized by using a 1-?10-bromodecyl?-3-methylimidazolium bromide ionic liquid as functional monomer and protectant.AuNCs were self-assembled onto molybdenum disulfite?MoS₂?nanosheets to fabricate AuNCs/MoS₂ nanocomposite,which was drop-coated onto a glassy carbon electrode surface to generate an interface for transthyretin?TTR?immobilizing.With a similar chemical structure to thyroxine,tetrabromobisphenol A?TBBPA?was specifically recognized by transthyretin and the TTR/AuNCs/MoS₂/GCE provides a sensing platform for TBBPA.Its sensing performance towards TBBPA was found significantly improved by the integration of AuNCs onto MoS₂ nanosheets.Three conditions for assay development,such as incubation time,incubation temperature and pH value,were investigated and found the optimum conditions were 200 s,35 ?,and pH 7.0 respectively.Under these conditions,the ratio Ri[Ri = ?i/i0]between the photocurrent variation??i?and the original photocurrent?i0?is linearly related to the logarithm of TBBPA concentration?1gcTBBPA?from 0.1 nmol L-1 to 1.0 }?mol L-1.The linear relationship can be described by the following equation:Ri= 0.09092 log?cTBBPA,mol L-1?+ 0.8976?R= 0.993?The detection limit is calculated to be 0.045 nmol L-1?S/N=3?.The photoelectrochemical immunosensor was used to accurately determine TBBPA concentration in spiked South-Lake water samples.?5?Gold nanoballs/WS2 nanosheets enhanced photoelectrochemical immunosensing of tribromophenolGold nanoballs?AuNBs?were controllably synthesized by using a 1,3-di?3-bromopropyl?-imidazolium bromide ionic liquid as functional monomer.Tungsten disulfite?WS2?nanosheets were exfoliated from bulk crystals with ultrasonication by using 1-vinyl-3-?3-aminopropyl?-imidazolium bromide ionic liquid and N-methyl pyrrolidinone as solvent.AuNBs were self-assembled onto tungsten disulfite WS2 nanosheets to obtain AuNBs/WS2 nanocomposite which was drop-coated onto a glassy carbon electrode surface to fabricate an interface to immobilize transthyretin?TTR?through a self-assembled process between the cysteine residues existed in TTR and AuNBs.The developed TTR-AuNBs/WS2/GCE provides a high performance platform for photoelectrochemical sensing of tribromophenol due to the affinity reaction between tribromophenol and TTR.All materials and interfaces were fully characterized.The photoelectrochemical sensing performance towards tribromophenol was found significantly enhanced by the integration of AuNBs onto WS2 nanosheets.Experimental conditions including pH value,the incubation time,and the incubation temperature were optimized.Under the optimal conditions,the ratio Ri[Ri = ?i/i0]between the photocurrent variation??i?and the original photocurrent?i0?shows a linear relationship to the logarithm of tribromophenol concentration?c?in the range from 0.05 nmol L-1 to 500 nmol L-1.The linear relationship can be described by the following equation:Ri=0.08900 log?c,mol L-1?+ 1.134?R =0.997?.The limit of detection is calculated to be 0.023 nmol L-1?S/N=3?.The photoelectrochemical immunosensor was employed to determine tribromophenol which was spiked in South-Lake water samples with excellent recoveries of 95.7%and 98.6%,demonstrating it is a practical tool for determining tribromophenol in real samples.