电化学研究方法课件-北京大学邵元华教授第三部分

液/液界面电化学及电分析化学简介,邵元华,北京大学化学与分子工程学院分析化学研究所,1.液/液界面电化学的发展历史2.液/液界面电化学的基本原理3.液/液界面电化学的主要研究方法及仪器设备4.液/液界面电化学的现状5.液/液界面电化学的未来展望,主要内容,参考书和文献：1.液/液界面电化学，P.Vanysek著，罗颖华译，汪尔康审校，吉林大学出版社，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.,1.BriefIntroductionofElectrochemistryatLiquid/LiquidInterfaces,应用电化学方法研究电荷在液/液界面上的转移反应-液/液界面电化学.它是电化学及电分析化学的一个重要分支，也是生物电化学的一个重要组成部分。,Charge(electronandion)transferacrossLiquid/Liquid(L/L)interfaces,orOil/Waterinterfaces,ortheinterfacebetweentwoimmiscibleelectrolyteSolutions(ITIES)isoneofthemostfundamentalphysicochemicalprocesses.,Briefhistory:1902,NernstandRiesenfeld1906,Cremerpointedoutthattheanalogybetweenthewater/oil/waterconcentrationcellsandbiologicalmembrane1939,VerweyandNiessen,firsttheoreticalpaperontheelectricaldoublelayerandpotentialdistributionatITIES1970s,Gavachetal.inFrance首先认识到L/L界面在一定的实验条件下可以被极化，并用Chronopotentiometry对一些简单离子在Water/Nitrobenzene(W/NB)的转移行为进行了研究。同时用ModifiedVerwey-Niessen(MVN)对实验结果进行了分析。随后Korytaetal.发展了滴水电极及相应的实验装置，并首先研究了中性载体加速离子转移反应。Samecetal.in1979设计了具有iR降补偿性质的四电极恒电势仪，用来记录离子转移反应的伏安图。这样L/L界面电化学才在世界各地得到普及和蓬勃发展。,1980s,汪尔康先生等是中国第一个从事L/L界面电化学研究的group1986,Giraultetal.第一个将微-L/L界面支持在Micropipettes上1991,Cornetal.应用SHG研究L/L界面1995，MirkinandBardetal.应用SECM研究L/L界面1997,Y.Shaoetal.第一个将纳米级-L/L界面支持在Nanopipettes上并采用玻璃双管进行离子型产生/收集研究最近几年各种光谱技术也应用于此领域的研究,Gold，Pt，C,NB1,2-DCE,ThedifferencebetweenL/LinterfaceandElectrode/Electrolyteinterface,ElectrochemistryofL/Linterfaces,O+e=R,RedoxReactions,O+e=R,RedoxReactions,MZ(w)=MZ(o),IonTransfer,theconventionalElectrochemistry,ThedifferencebetweenElectrochemistryatL/LinterfaceandtheconventionalElectrochemistry,ElectrochemistryatL/LInterfacesisthebridgebetweentheconventionalelectrochemistryandChemicalsensors,ElectrochemistryatLiquid/LiquidInterfacesisafastwaytoselectreceptorsformakingchemicalsensors,Electrode,O,BiologicalMembraneModel,L/LInterface,Electrode/electrolyte,Membrane/solution,Artificial,supportedmembraneandBLM,ElectrochemistryatL/LInterfaces,NewBranchofElectrochemistry,MechanismofChemicalsensors,PhaseTransfercatalyticreactions,Mimickingbiologicalmembranes,ResearchSignificanceandapplicationsofElectrochemistryatL/LInterfaces,ExtractionMechanism,2.液/液界面电化学的基本原理,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),NernstEquations,Liquid/Liquidinterfaceshavebeenclassifiedintotheideal-polarizedinterfaceandno-polarizedinterface.,2.2.SingleionGibbsenergyoftransferTATBassumption,2.3.SolvationofIonBornequation,2.4.Interfacialstructureandtheiontransfermechanism(A)MVNMODEL(B)GSMODEL,2.5.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(Bistriphenylphosphoranylideneammoniumtetraphenylborate),3.液/液界面电化学的主要研究方法及仪器设备,Almostalltheinstrumentshavebeenusedtostudyclassicalelectrochemistrycanbeusedtoinvestigatethechargetransferatliquid/Liquidinterfaces.4-electrodepotentiostat-BigiRdropaqueoussolutiondropping(ascending)electrodetwo-electrodesystem-microelectrodesRecently,wedevelopedanoveltechniquetostudyITIESwiththree-electrodesetupwiththehelpofthephaseratio.Thus,allelectrochemicallabscandoresearchonthissubjects.,2-电极系统,应用于液/液界面电化学研究的升水电极-四电极系统,应用常规三电极装置(恒电势仪)研究电荷在液/液界面上的转移反应实验装置图,Aqueousphase,新的技术，例如:SHG(Secondharmonicgeneration)microelectrodes,micropipettesandnano-pipettesSECMFemto-laserSimulationsThinfilms现已用在L/LInterfaces的研究。,各种电化学方法和技术,4.液/液界面电化学的现状Structure:MVNModelandGSModelMechanism:FacilitatediontransfermechanismKinetics:Butler-Volmerequation,MarcustheoryNanometeropipettesSECMApplications:Thinfilms(solarcell,drugdelivery),98年国际上液/液界面电化学研究存在的主要问题,1.界面结构未知!MVN模型和混合溶剂层模型(GS)2.可供选择作为有机相的有机溶剂数目有限3.没有很好的获取转移反应动力学的实验手段4.iR(i-电流，R-电阻，iR降是由于溶液中电阻所引起的干扰)降及充电电流较常规电化学更加严重,目前国际上液/液界面电分析化学研究存在的主要问题,1.界面结构未知!MVN模型和混合溶剂层模型(GS)2.可供选择作为有机相的有机溶剂数目有限3.实际应用问题,HowtosolvetheseProblems,Microelectrodes:SolidandNano-andMicropipettes,+,ScanningElectrochemicalMicroscopy,SECM,ElectrochemistryatL/LInterfaces,ArtificialMembrane/ElectrolyteInterfaces,BLM,ArtificialMembraneandBiosensors,ModifiedL/LInterfaces,MicroelectrodesNano-andMicropipettes,SECM,TheSEMdiagramsofNano-andMicropipettes,Micropipettes,Nanopipettes,Micropipettes,Theta()Micropipette,TheSEMdiagramsofNano-andMicropipettes,Micropipettes,Nanopipettes,我们group可以制备内径从几个nm到十几个m的玻璃纳、微米管,AqueousPhase,OrganicPhase,AqueousPhase,OrganicPhase,AsymmetricDiffusionField,TBATPBassupportingelectrolyteinDCE,TBATPBClassupportingelectrolyteinDCE,BTPPATPBassupportingelectrolyteinDCE,MicropipetteasatooltodeterminetheionicspecieslimitingthepotentialwindowatL/LInterfaces,TBATPB(Tetrabutyalammoniumtetraphenylborate),TBATPBCl(tetrabutyl-ammoniumtetrakis4-chlorophenylborate),BTPPATPB(Bistriphosphor-anylideneammoniumtetraphenyl-borate),1,2-dichloroethane(DCE),Ag/AgCl/0.01MTBACl/0.25mMDB18C6+0.01MTBATPBCl/0.01MKCl/AgCl/Ag,Identifythedifferentmechanisms,ACT,TOC,TIC,TID,w,o,w,o,w,o,w,o,Identifyofdifferentmechanismsoffacilitatediontransfers,Idisk=4nFaDC,Ipip=3.35nFaDC,WhyIpipisabout2.63timesbiggerthanIdisk?,Silanizationplaysveryimportantrolehere!,Anal.Chem.,1998,70,p3155-3161,3.4E-9,Nanometer-sizedL/LInterface,纳米管Nanopipet,AqueousPhase,Nano-ITIESkofrom0.1cm/sto10cm/sA54nmradiusB5nmradius,J.Am.Chem.Soc.,1997,119,8103,K+(w)+DB18C6(DCE)=K+DB18C6(DCE),J.Am.Chem.Soc.,1998,120,12700,科学意义和创新点：第一次在实验上实现了非氧化还原物质的Generation/CollectionMode。对于测量反应中间产物和快速电荷转移反应动力学有重要意义。,Thephotoof-micropipetteundermicroscope,Anal.Chem.,Y.Shaoetal.,2003，75，6593,“Non-solution”L/LInterfaceElectrochemistry,Generator(1)andcollector(2)voltammogramsofthetransferofK+betweenwaterandDCEcontainingDB18C6,igvs.Egandicvs.Egcurvesobtainedwithanaqueousfilmlinkingtwobarrelsofthe-pipet,Detectionofammoniaintheair.Cyclicvoltammogamsobtainedwitha-pipetexposedtoair(1)andammoniavaporaboveits2Msolution,ThepotentialwindowsdependupontheamountofAgar.Scanrateis30mV/s.Theradiusofthemicropipetteis4m，curves1、2、3and4correspondingto25%、10%、1%and0.5%ofAgar,respectively,Agar-waterMicroelectrode,CyclicVoltammogramsofK+transferfacilitatedbyDB18C6.KClis0.1M，Scanrate=30mV/s。Theradiusofthemicropipetteis3m。Curves1,2and3correspondingtotheconcentrationsofDB18C60.25,0.5and1.0mM.,1,2,3,(a)r=12m,(b)r=3m.,Planarstructure(a)and3Dstructure(b)ofanewtypeofcrownether,Cyclicvoltammogramwithscanrateof10mV/sfora14m-radiusmicropipetteelectrodewith100mMNaClinaqueousphaseand10mMTBATPBinorganicphase,Alkalimetalionstransferacrossthewater/DCEinterfaceFacilitatedbyDB18C6,Ionradius(r),formaltransferpotentialofrelevantalkalimetalionsandtheassociationconstantsofcomplex(M-DB18C6)+inDCEphase,冰/有机相溶液界面研究示意图,应用常规三电极装置(恒电势仪)研究电荷在液/液界面上的转移反应实验装置图,Aqueousphase,EffectoftheconcentrationRatiooftheredoxcouple,Sweeprate：100mV/s.a,b,c,d,ecorrespondto(Ferri/ferrocynaide)10,5,1,0.2,0.1,异相电子转移反应,创新点：用四(二)电极系统所能研究的体系，如离子、加速离子和电子转移反应，均能用常规三电极系统进行研究，这对于普及和发展此领域有重要意义。,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.,中国科学B,2002,32,271-277，Y.Shaoetal.,Ag/AgCl,Phasevolumeratior=VO/VW,Bigr,Smallr,A,B,Schematicpresentationsoftheelectrochemicalcellsforthecasesrarelarge(A)orsmall(B),Anal.Chem.,2003,75,4341,Y.Shaoetal.,可质子化药物的研究,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.科学通报，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/Liquidinterface,ProbingfacilitatediontransferatanexternallypolarizedL/Linterface,Experimentalapproachcurvesofa238-nm-radiuspipetfittedwiththetheoreticalvalues.Thetippotentialis0.45V,thesubstratepotentialis()0.20V()0.225V()0.25V()0.275V(*)0.30V()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/液界面本质上是一个分子软界面，