電化學(xué)研究方法-北京大學(xué)邵元華教授第三部分2課件

液/液界面電化學(xué)及電 分析化學(xué)簡介1.液/液界面電化學(xué)的發(fā)展歷史2.液/液界面電化學(xué)的基本原理3.液/液界面電化學(xué)的主要研究方法及儀器設(shè)備4.液/液界面電化學(xué)的現(xiàn)狀5.液/液界面電化學(xué)的未來展望主要內(nèi)容參考書和文獻(xiàn)：1.液/液界面電化學(xué)，P.Vanysek著，羅穎華譯，汪爾康審校，吉林大學(xué)出版社，1987年2.H.H.GiraultandD.J.Schiffrin,inElectroanalyticalChemistry,A.J.Bard.,Ed.;Vol:15,p.1,MarcelDekker,NewYork,19893.H.H.Girault,inModernAspectsofElectrochemistry,J.O.Bockris,B.E.Conway,R.E.White,Eds.;PlenumPress,NewYork,1993,Vol:25,p.14.J.Koryta,Electrochemicalpolarizationphenomenaattheinterfaceoftwoimmiscibleelectrolytesolutions.ElectrochimicaActa,24(1979)293-3005.J.Koryta,Electrochemicalpolarizationphenomenaattheinterfaceoftwoimmiscibleelectrolytesolutions.II.Progresssince1978.ElectrochimicaActa,29(1984)445-4526.VolkovAG,DeamerDW.Liquid-liquidinterfaces.TheoryandMethods.California:CRCPress,1996.7.VolkovAG,DeamerDW.LiquidinterfacesinChemistryandBiologyJohnWiley,NewYork,1998.Briefhistory: 1902,NernstandRiesenfeld1906,Cremerpointedoutthattheanalogybetweenthewater/oil/waterconcentrationcellsandbiologicalmembrane1939,VerweyandNiessen,firsttheoreticalpaperontheelectricaldoublelayerandpotentialdistributionatITIES1970s,Gavachetal.inFrance首先認(rèn)識到L/L界面在一定的實(shí)驗(yàn)條件下可以被極化，并用Chronopotentiometry對一些簡單離子在Water/Nitrobenzene(W/NB)的轉(zhuǎn)移行為進(jìn)行了研究。同時(shí)用ModifiedVerwey-Niessen(MVN)對實(shí)驗(yàn)結(jié)果進(jìn)行了分析。隨后Korytaetal.發(fā)展了滴水電極及相應(yīng)的實(shí)驗(yàn)裝置，并首先研究了中性載體加速離子轉(zhuǎn)移反應(yīng)。Samecetal.in1979設(shè)計(jì)了具有iR降補(bǔ)償性質(zhì)的四電極恒電勢儀，用來記錄離子轉(zhuǎn)移反應(yīng)的伏安圖。這樣L/L界面電化學(xué)才在世界各地得到普及和蓬勃發(fā)展。1980s,汪爾康先生等是中國第一個(gè)從事L/L界面電化學(xué)研究的group1986,Giraultetal.第一個(gè)將微-L/L界面支持在Micropipettes上 1991,Cornetal.應(yīng)用SHG研究L/L界面 1995，MirkinandBardetal.應(yīng)用SECM研究L/L界面1997,Y.Shaoetal.第一個(gè)將納米級-L/L界面支持在Nanopipettes上并采用玻璃雙管進(jìn)行離子型產(chǎn)生/收集研究最近幾年各種光譜技術(shù)也應(yīng)用于此領(lǐng)域的研究WWElectrodeOilGold，Pt，CNB1,2-DCEThedifferencebetweenL/Linterfaceand Electrode/ElectrolyteinterfaceChemicalsensorsElectrochemistryH+，pHK+,Na+,NH4+Cl-,Ac+O+e=RElectroactivespeciesNonelectroactivespeciesL/LInterfaceElectrochemistryatL/LInterfacesisthebridgebetweentheconventionalelectrochemistryandChemicalsensors

ElectrochemistryatLiquid/LiquidInterfacesisafastwaytoselectreceptorsformakingchemicalsensorsElectrodeOBiologicalMembraneModelL/LInterfaceElectrode/electrolyte

Membrane/solutionArtificial,supportedmembraneandBLM2.液/液界面電化學(xué)的基本原理2.1.EquilibriumconditionsandNernstpotentialIngeneralatLiquid/Liquidinterfaces,therearetwotypesofchargepartition: (A)thetransferofanionMwiththechargenumberzfromthephasewtothephaseoandthereverse: MZ(w) =MZ(o)M+(w) +L(o) =ML+(o)(B)theelectrontransferbetweenaredoxcoupleO1/R1inthephasewandaredoxcoupleO2/R2inthephaseo,whichcanberepresentedas:O1(w)+R2(o)=R1(w)+O2(o)

NernstEquations2.3.SolvationofIonBornequation2.4.Interfacialstructureandtheiontransfermechanism(A)MVNMODEL(B)GSMODEL2.5.SolventsandbaseelectrolytesThereareover20organicsolventswhichhavebeentestedintheITIESstudiessofar.AspointedoutbyKorytaet.al.,thefollowingthreerequirementshavebeencommonlyusedtochoosetheorganicsolvent:(1).Thesolubilityofsolventinwaterandwaterinthesolventmustbeverysmall.(2).Thesolventmustbesufficientlypolartopromotesufficientdissociationofthesupportingelectrolyteandthuskeepingenoughconductivityofthesolution.(3).Thedensityofthesolventshoulddiffersignificantlyfromthatofaqueousphaseinordertogetaphysicallystablel/linterface.Atpresent,themostcommonlyusedorganicsolventsarenitrobenzene(NB)and1,2-dichloroethane(1,2-DCE).Someothersolventshavebeentriedinthepasttwodecades,forexample,propiophenone,4-isopropyl-1-methyl-2-nitrobenzene,dichloro-methane,nitrotulene,chloroform,anilineetc.Inordertogetmoreflexiblechoice,organicsolventmixtureshavebeenalsoemployed,forexample,nitrobenzene+chlorobenzene,NB+benzonitrileandNB+benzene.Baseelectrolytes:TBATPB(tetrabutylammoniumtetraphenylborate),TBATPBCl,CVTPB,BTPPATPB(Bis[triphenylphosphoranylidene]ammoniumtetraphenylborate)3.液/液界面電化學(xué)的主要研究方法 及儀器設(shè)備Almostalltheinstrumentshavebeenusedtostudyclassicalelectrochemistrycanbeusedtoinvestigatethechargetransferatliquid/Liquidinterfaces.4-electrodepotentiostat--------BigiRdropaqueoussolutiondropping(ascending)electrodetwo-electrodesystem--------microelectrodesRecently,wedevelopedanoveltechniquetostudyITIESwiththree-electrodesetupwiththehelpofthephaseratio.Thus,allelectrochemicallabscandoresearchonthissubjects.應(yīng)用常規(guī)三電極裝置(恒電勢儀)研究電荷在液/液界 面上的轉(zhuǎn)移反應(yīng)實(shí)驗(yàn)裝置圖Aqueousphase新的技術(shù)，例如:SHG(Secondharmonicgeneration)microelectrodes,micropipettesandnano-pipettesSECMFemto-laserSimulationsThinfilms現(xiàn)已用在L/LInterfaces的研究。各種電化學(xué)方法和技術(shù)4.液/液界面電化學(xué)的現(xiàn)狀Structure: MVNModelandGSModelMechanism: FacilitatediontransfermechanismKinetics: Butler-Volmerequation,Marcustheory Nanometeropipettes SECMApplications:

Thinfilms(solarcell,drugdelivery)98年國際上液/液界面電化學(xué)研究存在的主要問題1.界面結(jié)構(gòu)未知!MVN模型和混合溶劑層模型(GS)2.可供選擇作為有機(jī)相的有機(jī)溶劑數(shù)目有限3.沒有很好的獲取轉(zhuǎn)移反應(yīng)動力學(xué)的實(shí)驗(yàn)手段4.iR(i-電流，R-電阻，iR降是由于溶液中電阻所引起的干擾)降及充電電流較常規(guī)電化學(xué)更加嚴(yán)重目前國際上液/液界面電分析化學(xué)研究存在的主要問題1.界面結(jié)構(gòu)未知!MVN模型和混合溶劑層模型(GS)2.可供選擇作為有機(jī)相的有機(jī)溶劑數(shù)目有限3.實(shí)際應(yīng)用問題HowtosolvetheseProblemsMicroelectrodes:SolidandNano-andMicropipettes+ScanningElectrochemicalMicroscopy,SECMElectrochemistryatL/LInterfacesArtificialMembrane/ElectrolyteInterfacesBLMArtificialMembraneandBiosensorsModifiedL/LInterfacesMicroelectrodesNano-andMicropipettesSECMTheSEMdiagramsofNano-andMicropipettesMicropipettesNanopipettesMicropipettesTheta()MicropipetteTheSEMdiagramsofNano-andMicropipettesMicropipettesNanopipettes我們group可以制備內(nèi)徑從幾個(gè)nm到十幾個(gè)m的玻璃納、微米管AqueousPhaseOrganicPhaseAqueousPhaseOrganicPhaseAsymmetricDiffusionFieldTBATPBassupportingelectrolyteinDCETBATPBClassupportingelectrolyteinDCEBTPPATPBassupportingelectrolyteinDCEMicropipetteasatooltodeterminetheionicspecieslimitingthepotentialwindowatL/LInterfacesTBATPB(Tetrabutyalammoniumtetraphenylborate)TBATPBCl(tetrabutyl-ammoniumtetrakis[4-chlorophenyl]borate)BTPPATPB(Bis[triphosphor-anylidene]ammoniumtetraphenyl-borate)1,2-dichloroethane(DCE)Ag/AgCl/0.01MTBACl/0.25mMDB18C6+0.01MTBATPBCl//0.01MKCl/AgCl/AgIdentifythedifferentmechanismsACTTOCTICTIDwowowowoIdentifyofdifferentmechanismsoffacilitatediontransfersIdisk=4nFaDCIpip=3.35nFaDCWhyIpipisabout2.63timesbiggerthanIdisk?Silanizationplaysveryimportantrolehere!Anal.Chem.,1998,70,p3155-31613.4E-9Nanometer-sizedL/LInterface納米管NanopipetAqueousPhaseNano-ITIESkofrom0.1cm/sto10cm/sA54nmradiusB5nmradiusJ.Am.Chem.Soc.,1997,119,8103K+(w)+DB18C6(DCE)=[K+DB18C6](DCE)

J.Am.Chem.Soc.,1998,120,12700科學(xué)意義和創(chuàng)新點(diǎn)：第一次在實(shí)驗(yàn)上實(shí)現(xiàn)了非氧化還原物質(zhì)的Generation/CollectionMode。對于測量反應(yīng)中間產(chǎn)物和快速電荷轉(zhuǎn)移反應(yīng)動力學(xué)有重要意義。Thephotoof-micropipetteundermicroscopeAnal.Chem.,Y.Shaoetal.,2003，75，6593“Non-solution”L/LInterfaceElectrochemistryGenerator(1)andcollector(2)voltammogramsofthetransferofK+betweenwaterandDCEcontainingDB18C6igvs.Egandicvs.Egcurvesobtainedwithanaqueousfilmlinkingtwobarrelsofthe-pipetDetectionofammoniaintheair.Cyclicvoltammogamsobtainedwitha-pipetexposedtoair(1)andammoniavaporaboveits2MsolutionThepotentialwindowsdependupontheamountofAgar.Scanrateis30mV/s.Theradiusofthemicropipetteis4m，curves1、2、3and4correspondingto25%、10%、1%and0.5%ofAgar,respectivelyAgar-waterMicroelectrodeCyclicVoltammogramsofK+transferfacilitatedbyDB18C6.KClis0.1M，Scanrate=30mV/s。Theradiusofthemicropipetteis3μm。Curves1,2and3correspondingtotheconcentrationsofDB18C60.25,0.5and1.0mM.123(a)r=12μm(b)r=3μm.Planarstructure(a)and3Dstructure(b)ofanewtypeofcrownetherCyclicvoltammogramwithscanrateof10mV/sfora14m-radiusmicropipetteelectrodewith100mMNaClinaqueousphaseand10mMTBATPBinorganicphaseAlkalimetalionstransferacrossthewater/DCEinterfaceFacilitatedbyDB18C6Ionradius(r),formaltransferpotentialofrelevantalkalimetalionsandtheassociationconstantsofcomplex(M-DB18C6)+inDCEphase冰/有機(jī)相溶液界面研究示意圖應(yīng)用常規(guī)三電極裝置(恒電勢儀)研究電荷在液/液界 面上的轉(zhuǎn)移反應(yīng)實(shí)驗(yàn)裝置圖AqueousphaseEffectoftheconcentrationRatiooftheredoxcouple

Sweeprate：100mV/s.a,b,c,d,ecorrespondto(Ferri/ferrocynaide)10,5,1,0.2,0.1異相電子轉(zhuǎn)移反應(yīng)創(chuàng)新點(diǎn)：用四(二)電極系統(tǒng)所能研究的體系，如離子、加速離子和電子轉(zhuǎn)移反應(yīng)，均能用常規(guī)三電極系統(tǒng)進(jìn)行研究，這對于普及和發(fā)展此領(lǐng)域有重要意義。CyclicvoltammogramsforpotassiumiontransferunderdifferentconcentrationsofDB18C6usingthefollowingcell:Ag|AgTPB|0.005MBTPPATPB+ymMDB18C6||1mMK4Fe(CN)6/1mMK3Fe(CN)6+0.1MKCl|Pt.a.y=0.005;b.y=0.05;c.y=0.1;d.y=0.5.Scanrate:100mV/s.中國科學(xué)B,2002,32,271-277，Y.Shaoetal.

Ag/AgClPhasevolumeratior=VO/VWBigrSmallrABSchematicpresentationsoftheelectrochemicalcellsforthecasesrarelarge(A)orsmall(B)Anal.Chem.,2003,75,4341,Y.Shaoetal.可質(zhì)子化藥物的研究Theoreticalionicpartitiondiagramforalipophilicbase(equiconcentrationconvention)).Chemicalstructuresandabbreviationsofthedrugcompoundsinvestigated.((AMTL)(THPE)(DPAN)Typicalcyclicvoltammogramsobtainedforthetransferofamitriptyline(AMTL)acrossthewater/1,2-dichloroethaneinterfaceatdifferentpHs.PeakAcorrespondtothetransferofAMTLH+andpeakBcorrespondtothatofTMA+.

Ionicpartitiondiagramsforamitriptyline(AMTL),Diphenhydramine(DPAN)andTrihexyphenedyl(THPE)atthewater/1,2-dichloroethaneinterface

Anal.Chem.,2003,75,4341,Y.Shaoetal.科學(xué)通報(bào)，2003，48，787,Y.Shaoetal.(a)TheTafelplotsforthesystemofZnPor/Fe(CN)64-atdifferentconcentrationsoforganicelectrolyteandtheMarcustheoreticalcurve(1),theconcentrationsare(▲)10mM,(□)50mM,()100mM,respectively.(b)TheTafelplotforthesystemofTCNQ/Fe(CN)63-.J.Am.Chem.Soc.,2003,125,9600,Y.Shaoetal.SchematicdiagramoftheapplicationofSECMtoprobefacilitatediontransferatanexternallypolarizedLiquid/LiquidinterfaceProbingfacilitatediontransferatanexternallypolarizedL/LinterfaceExperimentalapproachcurvesofa238-nm-radiuspipetfittedwiththetheoreticalvalues.Thetippotentialis0.45V,thesubstratepotentialis(■)0.20V(╳)0.225V(□)0.25V(▲)0.275V(*)0.30V(О)0.325V(●)0.35V(△)0.375V(

)0.40V(◆)0.425v(––)curve1theoreticalcurvefordiffusioncontrolledprocess,curves2-6theoreticalcurvesforkineticscontrolledprocess.TheinsetshowsdependenceoftheheterogeneousrateconstantsondifferentEs-Eso’.Angew.Chem.Int.Ed,2002,41(18),3445-3448,Y.Shaoetal.由于液/液界面本質(zhì)上是一個(gè)分子軟界面，本身處于動態(tài)變化中，其特點(diǎn)是較難定義界面的結(jié)構(gòu)和厚度。界面到底是一個(gè)分明的界面或者是一個(gè)逐漸擴(kuò)散兩相相互滲透的界面？答案是與所考慮的時(shí)間區(qū)間有關(guān)。由X-射線或中子散射所測量的毛細(xì)波行為還無法給出界面結(jié)構(gòu)的詳盡描述，有關(guān)界面的描