A Study On Construction And Application Of Three Kinds Of Nanoporous Carbon Based Electrochemical Sensors

Heavy metal ions are environmental pollutants,which have great threat to human health and living environment.Dopamine(DA)and uric acid(UA)are closely related to many physiological diseases of human body.Therefore,it is necessary to construct sensitive,economical,convenient,accurate and fast-response sensors for qualitative and quantitative detection of heavy metal ions,dopamine and uric acid.At present,the methods for qualitative and quantitative detection of heavy metal ions and small molecules such as dopamine and uric acid include inductively coupled plasma mass spectrometry,ultraviolet visible spectroscopy,surface enhanced raman spectroscopy,etc.However,these methods have many disadvantages,including expensive equipments,inconvenient carrying,time-consuming sample preparation,and so on.Electrochemical detection can overcome the above problems.In the electrochemical method,the electrode modification materials play important roles.Therefore,preparation of materials with good sensing performance for dopamine,uric acid and heavy metal ions has become the focus of this field.Porous carbon materials have been widely used in lithium ion batteries,supercapacitors,gas adsorption and separation,catalysis and analysis because of their high specific surface areas and tunable porosity.In the past ten years,the development of carbon based electrochemical sensor has become a hot research topic in the field of analytical chemistry.In this thesis,microwave exfoliation of graphite oxide carbon,nitrogen and sulfur doped porous carbon and graphdiyne materials were prepared and used as electrode modification materials for the detection of lead ions and cadmium ions,dopamine and uric acid,respectively.Two sets of modified electrode materials were designed to construct heavy metal ion electrochemical sensors.First,the nitrogen and sulfur co-doped graphitic porous carbon(N,S-GPC)was successfully synthesized via a facile one-pot approach with incorporation of p-phenylenediamine and sulphuric acid as heteroatom sources and silica nanosphere as template.A novel electrochemical sensor based on the N,S-GPC was then fabricated and applied in detection of cadmium ion.Due to the rich nitrogen and sulfur elements,the high specific surface area and the porous structure of the prepared N,S-GPC,the developed Cd(II)sensor shows good analytical performance using a differential pulse anodic stripping voltammetry(DPASV).Compared to the bare glassy carbon electrode,the electrode modified with N,S-GPC has higher peak current and better sensitivity in the detection of Cd(II).By optimizing the experimental conditions,the N,S-GPC based sensor showed superior sensitivity and selectivity for Cd(II),with a detection limit of 0.1 ?g L-1 over a concentration range of 4-80 ?g L-1.Applications of the N,S-GPC based sensor for Cd(II)assay in tap water samples achieved results with good recoveries,indicating the N,S-GPC based electrode is promising in real sample analysis.Second,a new kind o f graphdiyne based sensor was prepared.By optimizing the experimental conditions,the screen printed electrode(SPE)modified with graphdiyne sensor was used to detect cadmium and lead ions via DPASV approach.Compared with the bare SPE,the graphdiyne modified one showed superior peak current and sensitivity,with the detection limits of 0.6 ?g/L for Cd(II)and 0.5 ?g/L for Pb(II)(at a signal-to-noise ratio of 3,S/N=3),respectively.Applications of the graphdiyne based sensor for lead and cadmium assay in the real water sample achieved results with suboptimal recoveries..Therefore,further studies are needed in this work although the graphdiyne based sensor is valuable in potential application.To achieve selective determination of DA and UA at the presence of concentrated ascorbic acid(AA),an activated porous graphite oxide(PG)was prepared by combining a simple KOH activation and an efficient microwave assisted exfoliation.The as-prepared PG was used for GCE modification to prepare electrochemical sensor(PG/GCE)in a voltammetric determination of DA and UA in the presence of high concentrations of AA.The prepared PG has a superior surface area.Compared to bare glassy carbon electrode,the cyclic voltammogram at the PG/GCE exhibit remarkably enhanced peak currents towards DA,UA and AA.Under optimum conditions,the oxidation peak currents for DA and UA increased linearly over concentration ranges of 0.5 –60 ?M and of 0.5–100 ?M,respectively,with the estimated detection limits of 0.04 ?M and 0.02 ?M.Applications of the PG/GCE for urine analyses was investigated and the results with good recoveries indicate the feasibility of the developed electrode in clinic sensing application.