| The food security problem has been focused on for a long time.With thedevelopment of industrial and agricultural manufacture,food contamination isincreasing serious,especially for heavy metals contamination.The residence time ofmost heavy metals in soils and plants is very long.Taken by plants,heavy metals mayenter the food chain in significant amounts.Hence,people could be at risk of adversehealth effects from consuming food grown in soils containing elevated metalconcentrations.Considerable interest and extensive study have developed in thedetermination of heavy metals in food all over the world.Therefore,it is practicallyimportant for the detection of toxic heavy metals in different kinds of food and waterin evaluating food quality,protecting human health and promoting sustainabledevelopment of economy and society.Nanomaterials are defined as the materials with domain ranges between 1 and100 nm at least in one dimension,or materials that be composed of nanoscale units.Nanocomposite materials have recently been shown to represent a novel anddeveloped rapidly nanomaterials,which are formed by no less than two solid phaseswith nanoscale size at least in one dimension.The nanoscale dispersed phase ofcomposite materials not only remarkably increased interface areas of two phases,butalso significantly enhanced interactions between two interfaces caused by nanosizeeffects.Difference from singular nanomaterials and nanophase,nanocompositematerials not only have the nanoscale units' basic properties:quantum size effect,surface effect,small size effect,quantum tunneling effect,dielectric confinementeffect and so on,also exist new effects caused by combination of nano-structuredmaterials such as quantum coupling effect and synergistic effect,making their generalperformances are better than the original single materials and be able to meetrequirements for a variety of practical application.Nanocomposites are known as themost promoting materials in the 21st century.With the development ofnano-technology,nanocomposites as a new type of electrode materials are applied inelectrochemical detection and analysis by people's growing concern. Microwave radiation as a fast,simple and efficient heating technique has beenwidely applied for chemical reactions and a variety of nanomaterials synthesis.Theadvantages of this method over the conventional heating methods are speediness anduniformity,which result in improving kinetics of the reaction and obtaining narrowerdistribution of particle size.Microwave-electrochemistry is a new technique thatcombining the principle of microwave technology with electrochemical theory.Microwave technology into electrochemical detection is still a relatively new conceptand area,especially for heavy metals detection in the microwave-electrochemicalsynergistic system.Although microwave-electrochemistry has been a preliminaryapplication,research in this area is still in its infancy.The rapid microwave synthesisof nanocomposite materials which were applied to detect heavy metals undermicrowave-electrochemical system has not been reported.In this thesis,nanocomposite materials were synthesized via electrochemicalmethods and microwave irradiation,and applied for the determination of trace heavymetals (mainly including Pb,Cd,Hg,As,Cr) in food and water by electrochemicalstripping analysis.The morphology and composition of synthesized nanomaterialswere characterized by the means of scanning electron microscopy (SEM),transmission electron microscopy (TEM),atomic force microscopy (AFM) andenergy dispersive X-ray spectra (EDX).The determination and analysis of traceheavy metals were carried out by anodic stripping voltammetry (ASV),linearscanning voltammetry (LSV),amperometric detection and microwave-electrocheicalsynergistic system.Based on this,manufacture of heavy metals rapid analysisinstrument was constructed and developed.Totally,there are nine chapters in thispaper.Chapter 1 PrefaceThis chapter has four parts,that is,heavy metals pollution and hazards,technicaldevelopment for heavy metals determination,research and development fornanocomposite materials and its application to heavy metals determination,manufacture of heavy metals rapid analysis instrument.The sort,actuality of heavymetals contamination in food and the development of spectral analysis for heavy metals detection have been brief introduced,and electrochemical analysis for heavymetals determination has also been reviewed in detail.Then nanocompositematerials'classification,properties and preparation methods has been reviewed.Thenanocomposite materials synthesized by microwave irradiation and its application toheavy metals determination has been discussed particularly.Lastly,we introduce theresearch status quo of manufacture of heavy metals rapid analysis instrument andreview its application and prospect.Chapter 2 A Nafion-coated bismuth film electrode for the determination of heavymetals in vegetable by anodic stripping voltammetryIn this chapter,Nafion-coated bismuth film electrode (NCBFE) as a workingelectrode was applied to determine trace Pb(Ⅱ),Cd(Ⅱ) and Zn(Ⅱ) by differential pulseanodic stripping voltammetry.The effects on experimental results of bismuthconcentration,Nafion thickness,preconcentration time and surface active compoundswere examized in detail.The results showed that NCBFE has excellentelectrochemical performance for the determination of Pb(Ⅱ),Cd(Ⅱ) and Zn(Ⅱ).Bismuth has ability to form alloys with some metals such as cadmium,lead and zinc,improving the efficiency of deposition,and the sensitivity and tolerance to surfaceactive compounds were greatly enhanced by Nafion membrane,resulting inimproving remarkably the stability and reproducibility of the methods.The NCBFEwas successfully applied to determine trace heavy metals in vegetable samples,andthe results were in agreement with those of graphite furnace atomic absorptionspectrometry with the actual application value.Chapter 3 MWCNTs/Bi/Nafion composite materials electrodes for the detectionof trace Pb(Ⅱ) and Cd(Ⅱ) in drinking waterIn this chapter,multi-wall carbon nanotubes/bismuth film/Nafion membrane(MWCNTs/Bi/Nafion) composite materials were prepared by electrochemicaldeposition,and its application to detect trace Pb(Ⅱ) and Cd(Ⅱ) in drinking water.Thesynergistic effects on the electrochemical response for Pb(Ⅱ) and Cd(Ⅱ) determinationat the MWCNTs/Bi/Nafion composite electrodes were evaluated.The study resultsshowed the MWCNTs/Bi/Nafion composite electrodes have excellent signals for trace Pb(Ⅱ) and Cd(Ⅱ) determination,and both the sensitivity and stability were better thanthose of MWCNTs/Nafion and MWCNTs/Bi electrodes.The MWCNTs/Bi/Nafioncomposite electrodes were successfully applied to determine Pb(Ⅱ) and Cd(Ⅱ) in realsample,and the results of the present method agreed well with those of atomicabsorption spectroscopy.The recovery is 95-107%,proving that the proposed methodhas good accuracy and reliability with the practical application of significance.Chapter 4 The preparation and characterization of Au-NPs/CNTs compositematerials by microwave radiation and its application to detect trace Hg(Ⅱ)Gold nanoparticles/carbon nanotubes (Au-NPs/CNTs) composites were rapidlysynthesized by microwave radiation,and firstly applied for the determination of tracemercury(Ⅱ) by anodic stripping voltammetry (ASV).The structure and compositionof the synthesized Au-NPs/CNTs nanocomposites were characterized by transmissionelectron microscopy (TEM),energy dispersive X-ray spectroscopy (EDX),UV-visabsorption spectroscopy and cyclic voltammetry.Au-NPs/CNTs nanocompositesmodified glassy carbon electrode (Au-NPs/CNTs/GCE) exhibited excellentperformance for Hg(Ⅱ) analysis with wide linear range,high sensitivity,good stability,and repetitive useness.The Au-NPs/CNTs composite electrode was successfullyapplied to determine trace Hg(Ⅱ) analysis in water samples,suggesting the proposedmethod may have practical utility.Chapter 5 Microwave-irradiated synthesized platinum nanoparticles/carbonnanotubes for oxidative determination of trace arsenic(Ⅲ) in waterPlatinum nanoparticles/carbon nanotubes (Ptnano/CNTs) were rapidlysynthesized by microwave radiation,and applied for the oxidative determination ofAs(Ⅲ).The transmission electron microscopy (TEM) revealed the size of synthesizedPt nanoparticles with nominal diameter of 15±3 nm.The electrochemical propertiesof Ptnano/CNTs composite electrode was investigated by cyclic voltammetry and linearscan voltammetry.The Ptnano/CNTs modified glassy carbon electrode(Ptnano/CNTs/GCE) exhibited better performance for As(Ⅲ) analysis than that of Ptnanoparticles modified GCE (Ptnano/GCE) by electrochemical deposition or Pt foilelectrode with excellent reproducibility and stability.The limit of determination (LOD) of the Ptnano/CNTs/GCE was 1-2 orders of magnitude lower than that of Ptnano/GCE orPt foil electrode,and the proposed method avoided interferences from Cu(Ⅱ) andchloride ions existing commonly in water system,proving that the method wassuitable for routine determination of As(Ⅲ) with speediness and accuracy.Chapter 6 Highly ordered platinum-nanotube arrays for oxidative determinationof trace arsenic(Ⅲ)A novel method for the oxidative determination of trace arsenic(Ⅲ) wasinvestigated on highly ordered platinum-nanotube (PtNTs) array electrodes.ThePtNTs with a highly organized structure were fabricated by electrochemicaldeposition of platinum in a 3-aminopropyltrimethoxysilane-modified porous anodicalumina template (PAA) in solution containing AuCl4-.The morphologies andstructures of PtNTs arrays electrode were characterized by scanning electronmicroscopy (SEM) and X-ray diffraction (XRD).Electrochemical experiments provedthat the PtNTs array electrode exhibited larger effective area and high catalyticproperties,which have better performance for As(Ⅲ) analysis in comparison withplatinum nanoparticles-coated GCE (Ptnano/GCE) or Pt foil electrode.The PtNTs arrayelectrode showed to provide better reproducibility and higher sensitivity.The limit ofdetection (LOD) was typically 1-2 orders of magnitude lower than that of Ptnano/GCEor Pt foil electrode,suggesting that the proposed method has potential applicationvalues for trace As(Ⅲ) analysis.Chapter 7 Microwave-voltammetry synergistic system for the determination ofCu(Ⅱ) and Pb(Ⅱ) in river waterIn this chapter,in situ microwave activation of electrochemical detection ofCu(Ⅱ) and Pb(Ⅱ) at a gold nanoparticles-modified Pt (Au-NPs/Pt) and bare Ptmicroelectrodes was investigated.Self-focusing of the microwave radiation creates anextreme localized heating at the electrode/solution (electrolyte) interface within thediffusion layer of the electrode with an inverted thermal gradient and convective flow.The temperature at the electrode/solution interface is calibrated with reversible oneelectron redox system Fe(CN)63-/4- in aqueous K2SO4 solution (pH 3).The resultsshowed that significantly increased currents of electron couple of Fe(CN)63-/4- were observed at the Au-NPs/Pt and bare Pt microelectrodes under the low microwavepower.The Cu(Ⅱ) detection at the Au-NPs/Pt microelectrode by cyclic voltammetryand Pb(Ⅱ) detection by differential pulse stripping voltammetry were also shown to bestrongly enhanced by microwave radiation,which triggers Cu(Ⅱ) and Pb(Ⅱ) currentsresponse orders of magnitude higher than those expected values in conventionalconditions.The effect of surfactant,which blocks the electrochemical signals of Cu(Ⅱ)and Pb(Ⅱ) under conventional conditions,is remarkably decreased under the in situmicrowave radiation of electrochemical process.Results implied thatmicrowave-electrochemistry synergistic system is a promising approach to developinstruments for heavy metals or other pollutants determination.Chapter 8 The preparation and characterization of Au nanoparticles-coated Ptnanoporous film electrode and its application to detect Cr(Ⅵ) in waste waterThis chapter describes the preparation of Au-nanoparticles-coated Pt-nanoporousfilm (AuNPs/PtNF) on a platinum substrate via a simple,rapid and"green"approach.The platinum electrode that had been anodized under a high potential of 6 V isreduced by freshly prepared ascorbic acid (AA) solution to obtain platinumnanoporous film electrode.Then the Au nanoparticles were grown on the electrode bycyclic voltammetry (CV).The morphology and composition of AuNPs/PtNFcomposite electrode were characterized by scanning electron microscopy (SEM) andenergy dispersive X-ray spectra (EDX),and the electrochemical properties ofAuNPs/PtNF composites were examized by CV and amperometric analysis.Theresulting AuNPs/PtNF composite electrode has highly electroactive area and moreoutstanding properties.Furthermore,the as-prepared AuNPs/PtNF compositeelectrode exhibited high electrocatalytic activity toward Cr(Ⅵ) reductiondetermination compared to Pt foil electrode and PtNF electrode.The present novelstrategy for the preparation of AuNPs/PtNF composite electrode showed simpleness,short reaction time and low cost,suggesting that it is a promising approach forpreparation of nanocomposites materials.Chapter 9 Manfacture of heavy metals rapid analysis instrumentA rapid heavy metals analysis instrument was developed by means of electrochemical theory combined with the special properties of nanocompositematerials.This instrument has such advantages as speediness,sensitivity,accuracyand no contamination,even simultaneous determination of various metal elementswith satisfactory agreement with spectra analysis.The developed instrument hasminiaturized design,easy to take,stable performance and reliable quality,suggestingthat it is a very promising analytical instrument for application.
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