电化学研究方法课件北京大学邵元华教授第三部分2

1、液液/液界面电化学及电液界面电化学及电 分析化学简介分析化学简介邵元华邵元华北京大学化学与分子工程学院分析化学研究所北京大学化学与分子工程学院分析化学研究所1.液液/液界面电化学的发展历史液界面电化学的发展历史2.液液/液界面电化学的基本原理液界面电化学的基本原理3.液液/液界面电化学的主要研究方法液界面电化学的主要研究方法及仪器设备及仪器设备4.液液/液界面电化学的现状液界面电化学的现状5.液液/液界面电化学的未来展望液界面电化学的未来展望主要内容主要内容参考书和文献：参考书和文献：1. 液液/液界面电化学，液界面电化学， p.vanysek 著，著， 罗颖华罗颖华 译，汪尔康译，汪尔康 审

2、校，审校， 吉林大学出版社，吉林大学出版社， 1987年年2. h.h.girault and d.j.schiffrin, in electroanalytical chemistry, a.j.bard., ed.; vol:15, p.1, marcel dekker, new york ,19893. h.h.girault, in modern aspects of electrochemistry, j.o.bockris, b.e.conway, r.e.white, eds.; plenum press, new york, 1993, vol:25, p.14. j.kory

3、ta, electrochemical polarization phenomena at the interface of two immiscible electrolyte solutions. electrochimica acta, 24(1979)293-3005. j.koryta, electrochemical polarization phenomena at the interface of two immiscible electrolyte solutions. ii. progress since 1978. electrochimica acta, 29(1984

4、)445-4526. volkov a g, deamer d w. liquid-liquid interfaces. theory and methods. california: crc press, 1996.7. volkov a g, deamer d w. liquidinterfaces in chemistry and biology john wiley, new york, 1998.1. brief introduction of electrochemistry at liquid/liquid interfaces应用电化学方法研究电荷在液应用电化学方法研究电荷在液

5、/液界面上的转移液界面上的转移反应反应 - 液液/液界面电化学液界面电化学.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。是生物电化学的一个重要组成部分。charge (electron and ion) transfer across liquid/liquid (l/l) interfaces, or oil/water interfaces, or the interface between two immiscible electrolytesolutions (ities) is one of the most fun

6、damentalphysicochemical processes. brief history:1902, nernst and riesenfeld1906, cremer pointed out that the analogy between the water/oil/water concentration cells and biological membrane1939, verwey and niessen, first theoretical paper on the electrical double layer and potential distribution at

7、ities1970s, gavach et al. in france 首先认识到首先认识到 l/l 界面在一定界面在一定的实验条件下可以被极化，的实验条件下可以被极化， 并用并用chronopotentiometry 对对一些简单离子在一些简单离子在water/nitrobenzene (w/nb)的转移行为进的转移行为进行了研究。同时用行了研究。同时用modified verwey-niessen (mvn)对实验对实验结果进行了分析。随后结果进行了分析。随后 koryta et al. 发展了滴水电极及相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的实验装置，并首

8、先研究了中性载体加速离子转移反应。应。samec et al. in 1979设计了具有设计了具有ir降补偿性质的四电极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。这样恒电势仪，用来记录离子转移反应的伏安图。这样l/l界界面电化学才在世界各地得到普及和蓬勃发展。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汪尔康先生等是中国第一个从事l/l界面电化学界面电化学研究的研究的group1986, girault et al. 第一个将微第一个将微-l/l界面支持在界面支持在micropipettes 上上1991, corn et al. 应用应用

9、shg研究研究l/l界面界面1995，mirkin and bard et al. 应用应用secm 研究研究l/l界面界面1997, y.shao et al. 第一个将纳米级第一个将纳米级-l/l界面支持在界面支持在 nanopipettes 上并采用玻璃双管进行离子型产生上并采用玻璃双管进行离子型产生/收集研究收集研究最近几年各种光谱技术也应用于此领域的研究最近几年各种光谱技术也应用于此领域的研究wwelectrodeoilgold，pt，c nb 1,2-dcethe difference between l/l interface andelectrode/electrolyte i

10、nterfaceelectrochemistry of l/l interfaceso + e = rredox reactionso + e = rredox reactionsmz (w) = mz(o)ion transferthe conventional electrochemistrythe difference between electrochemistry at l/l interface and the conventional electrochemistrychemical sensorselectrochemistryh+，phk+,na+,nh4+cl-, ac+o

11、 + e = relectroactivespeciesnonelectroactivespeciesl/l interfaceelectrochemistry at l/l interfaces is the bridge between the conventional electrochemistry and chemical sensors electrochemistry at liquid/liquid interfaces is a fast way to select receptors for making chemical sensorselectrodeobiologic

12、al membrane modell/l interfaceelectrode/electrolyte membrane/solutionartificial ,supported membrane and blmelectrochemistryat l/l interfacesnew branch ofelectrochemistrymechanism of chemical sensorsphase transfercatalytic reactionsmimickingbiologicalmembranesresearch significance and applicationsof

13、electrochemistry at l/l interfacesextraction mechanism2.液液/液界面电化学的基本原理液界面电化学的基本原理2.1.equilibrium conditions and nernst potentialin general at liquid/liquid interfaces, there are two types of charge partition:(a) the transfer of an ion m with the charge number z from the phase w to the phase o and th

14、e reverse:mz(w) = mz(o)m+(w) + l(o) = ml+(o)(b) the electron transfer between a redox couple o1/r1 in the phase w and a redox couple o2/r2 in the phase o, which can be represented as:o1(w) + r2(o) = r1(w) + o2(o)wwoo0,o0,wommmwmow0momwmlnlnrtzfzfrtzf nernst equations+1/2ww0wlo1/2o1mmmllnln()rtdrtczf

15、df +owwo,0w,0w0o2r1o21oowhr2o1lna arteenfa aliquid/liquid interfaces have been classified into the ideal-polarized interface and no-polarized interface.2.2. single ion gibbs energy of transfertatb assumption2.3.solvation of ionborn equation2.4.interfacial structure and the ion transfer mechanism(a)

16、mvn model(b) gs model2a00vac0(bron)1 1/8azegr 000sneggg 000trshggg 0nmr+cg2.5. solvents and base electrolytesthere are over 20 organic solvents which have been tested in the ities studies so far. as pointed out by koryta et.al., the following three requirements have been commonly used to choose the

17、organic solvent:(1). the solubility of solvent in water and water in the solvent must be very small.(2). the solvent must be sufficiently polar to promote sufficientdissociation of the supporting electrolyte and thus keeping enough conductivity of the solution.(3). the density of the solvent should

18、differ significantly from that of aqueous phase in order to get a physically stable l/l interface.at present, the most commonly used organic solvents are nitrobenzene(nb) and 1,2-dichloroethane (1,2-dce). some othersolvents have been tried in the past two decades, for example, propiophenone, 4-isopr

19、opyl-1-methyl-2-nitrobenzene, dichloro-methane,nitrotulene, chloroform, aniline etc. in order to get more flexible choice, organic solvent mixtures have been also employed, for example, nitrobenzene + chlorobenzene, nb + benzonitrile and nb + benzene.base electrolytes: tbatpb (tetrabutylammonium tet

20、raphenylborate), tbatpbcl, cvtpb, btppatpb (bistriphenylphosphoranylideneammonium tetraphenylborate)3.液液/液界面电化学的主要研究方法液界面电化学的主要研究方法及仪器设备及仪器设备almost all the instruments have been used to study classical electrochemistry can be used to investigate the charge transfer at liquid/liquid interfaces.4-elec

21、trode potentiostat - big ir dropaqueous solution dropping (ascending) electrodetwo-electrode system - microelectrodesrecently, we developed a novel technique to study ities withthree -electrode setup with the help of the phase ratio. thus, allelectrochemical labs can do research on this subjects.2-电

22、极系统电极系统应用于液应用于液/液界面电化学研究的液界面电化学研究的升水电极升水电极- 四电极系统四电极系统aqueous phaseag/agtpb l/l interfaceorganic phasept counterelectrodept应用常规三电极装置应用常规三电极装置(恒电势仪恒电势仪)研究电荷在液研究电荷在液/液界液界面上的转移反应实验装置图面上的转移反应实验装置图aqueous phase新的技术，例如新的技术，例如: shg(second harmonic generation) microelectrodes, micropipettes and nano-pipette

23、s secm femto-lasersimulationsthin films 现已用在现已用在l/l interfaces 的研究。的研究。各种电化学方法和技术各种电化学方法和技术4. 液液/液界面电化学的现状液界面电化学的现状structure: mvn model and gs model mechanism: facilitated ion transfer mechanismkinetics: butler-volmer equation, marcus theorynanometeropipettessecmapplications: thin films (solar cell,

24、 drug delivery)98年国际上液年国际上液/液界面电化学研究存在的主要问题液界面电化学研究存在的主要问题1. 界面结构未知界面结构未知! mvn模型和混合溶剂层模模型和混合溶剂层模 型型(gs)2. 可供选择作为有机相的有机溶剂数目有限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没有很好的获取转移反应动力学的实验手段4. ir(i-电流，电流，r-电阻，电阻，ir降是由于溶液中电阻降是由于溶液中电阻 所引起的干扰所引起的干扰)降及充电电流较常规电化学更降及充电电流较常规电化学更 加严重加严重目前国际上液目前国际上液/液界面电分析化学液界面电分析化

25、学研究存在的主要问题研究存在的主要问题1.界面结构未知界面结构未知! mvn模型和混合溶剂层模模型和混合溶剂层模 型型(gs)2. 可供选择作为有机相的有机溶剂数目有限可供选择作为有机相的有机溶剂数目有限3. 实际应用问题实际应用问题how to solve these problemsmicroelectrodes:solid and nano- andmicropipettes+scanningelectrochemical microscopy, secmelectrochemistry at l/l interfacesartificial membrane/electrolyte i

26、nterfacesblmartificial membrane andbiosensorsmodified l/l interfacesmicroelectrodesnano- and micropipettessecmthe sem diagrams ofnano- and micropipettesmicropipettesnanopipettesmicropipettestheta ( )micropipettethe sem diagrams ofnano- and micropipettesmicropipettesnanopipettes我们我们group可以制备内径从几个可以制备

27、内径从几个nm到到十几个十几个 m的玻璃纳、微米管的玻璃纳、微米管aqueous phaseorganic phaseaqueous phaseorganic phaseasymmetric diffusion fieldtbatpb as supporting electrolyte in dcetbatpbcl as supportingelectrolyte in dcebtppatpb as supportingelectrolyte in dcemicropipette as a toolto determine the ionic species limiting thepoten

28、tial window at l/linterfacestbatpb (tetrabutyalammoniumtetraphenylborate)tbatpbcl(tetrabutyl-ammonium tetrakis4-chlorophenylborate)btppatpb (bistriphosphor-anylideneammonium tetraphenyl-borate)1,2-dichloroethane (dce)ag/agcl/0.01mtbacl/0.25mmdb18c6+0.01mtbatpbcl/0.01mkcl/agcl/agidentify the differen

29、t mechanismsacttoctictidwowowowoidentify of different mechanisms of facilitated ion transfersidisk =4nfadcipip =3.35nfadcwhy ipip is about 2.63 times bigger than idisk ?silanization plays very important rolehere!anal.chem., 1998, 70,p3155-31613.4e-9nanometer-sized l/l interface 纳米管纳米管nanopipetaqueou

30、s phasenano-itiesko from 0.1cm/s to 10cm/s a 54nm radiusb 5nm radiusj.am.chem.soc., 1997, 119, 8103k+(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物质的generation/collection mode。 对于测量反应中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间产物和快速电荷转移反应动力学有重

31、要意义。the photo of -micropipette under microscope在光学显微镜下在光学显微镜下 -微米管的微米管的侧面和正面图侧面和正面图anal.chem., y. shao et al., 2003， 75，6593“ non-solution” l/l interface electrochemistrygenerator (1) and collector(2)voltammograms of the transfer of k+ between waterand dce containing db18c6ig vs. eg and ic vs. eg cu

32、rvesobtained with an aqueous film linking two barrels of the -pipetdetection of ammonia in the air. cyclic voltammogams obtained witha -pipet exposed to air (1) and ammonia vapor above its 2m solution-0.5-0.4-0.3-0.2-0.6-1000100200300400500potential e/mvcurrent i/nathe potential w

33、indows depend upon the amount of agar. scan rate is 30mv/s. the radius of the micropipette is 4m，curves1、2、3 and 4 corresponding to 25%、10%、1% and0.5% of agar, respectivelyagar-water microelectrode-2-10123456-1000100200300400potential e/mvcurrent i/nacyclic voltammograms of k+ transfer facilitated b

34、y db18c6.kcl is 0.1m，scan rate = 30mv/s。the radius of the micropipette is 3m。curves 1,2 and 3 corresponding to the concentrations of db18c6 0.25, 0.5 and 1.0mm.123(a) r= 12 m (b) r= 3 m.planar structure (a) and 3d structure (b) of a new type of crown ethercyclic voltammogram with scan rate of 10mv/s

35、 for a 14m-radiusmicropipette electrode with 100mm nacl in aqueous phase and 10mm tbatpb in organic phasealkali metal ions transfer across the water/dce interfacefacilitated by db18c6ion radius (r), formal transfer potential of relevant alkali metal ions and the association constants of complex (m-d

36、b18c6)+ in dce phase冰冰/有机相溶液界面研究示意图有机相溶液界面研究示意图aqueous phaseag/agtpb l/l interfaceorganic phasept counterelectrodept应用常规三电极装置应用常规三电极装置(恒电势仪恒电势仪)研究电荷在液研究电荷在液/液界液界面上的转移反应实验装置图面上的转移反应实验装置图aqueous phase-404ee (v )-303d -202i(a )c -303b -404a effect of the concentration ratio of the red

37、ox couple sweep rate：100 mv/s. a, b, c, d, e correspond to (ferri/ferrocynaide) 10, 5, 1, 0.2,0.1异相电子转移反应异相电子转移反应创新点：用四创新点：用四(二二)电极系统所能研究电极系统所能研究的体系，如离子、的体系，如离子、加速离子和电子转加速离子和电子转移反应，均能用常移反应，均能用常规三电极系统进行规三电极系统进行研究，这对于普及研究，这对于普及和发展此领域有重和发展此领域有重要意义。要意义。0.00.8-6-3036 a b c di (a)e (v)cyclic volt

38、ammograms for potassium ion transfer under different concentrations of db18c6 using the following cell: ag | agtpb | 0.005 m btppatpb + y mm db18c6 | 1 mm k4fe(cn)6/1 mm k3fe(cn)6 + 0.1 m kcl | pt. a. y = 0.005; b. y = 0.05; c. y = 0.1; d. y = 0.5. scan rate: 100 mv/s.中国科学中国科学b, 2002, 32, 271-277，y.

39、shao y.shao et al.et al. ag|agtpbclptorganic phaseaqueous phasel|l interfaceptag/agclphase volume ratio r = vo/vwbig rsmall rabschematic presentations of the electrochemical cells for the cases r are large (a) or small (b)anal.chem., 2003, 75, 4341, y.shao et al. 可质子化药物的研究可质子化药物的研究w+bhph+w0obhwoo+bh

40、wbapk123theoretical ionic partition diagram for a lipophilic base (equiconcentration convention). 01234567891011121314-600-400-2000200400600800(cpyo/cpyw = 5) pypyh+(w)pyh+(o)ph ow / mv r=100001234567891011121314-600-400-2000200400600800r=0.01(cpyo/cpyw=5) ow /mvph321pypyh+(w)pyh+(o)chemical structu

41、res and abbreviations of the drug compounds investigated. (amtl)(thpe)(dpan)typical cyclic voltammograms obtained for the transfer of amitriptyline (amtl) across the water / 1,2-dichloroethane interface at different phs. peak a correspond to the transfer of amtlh+ and peak b correspond to that of tm

42、a+. 02468101214-400-300-200-1000100200thpeamtldpan321bbh+(w)bh+(o)e /mvphionic partition diagrams for amitriptyline (amtl), diphenhydramine (dpan) and trihexyphenedyl (thpe) at the water / 1,2-dichloroethane interface anal.chem., 2003, 75, 4341, y.shao et al.科学通报，2003， 48， 787, y.shao et al.(a)the t

43、afel plots for the system of znpor/fe(cn)64- at different concentrations of organic electrolyte and the marcus theoretical curve (1), the concentrations are ()10mm, ()50mm, ()100mm, respectively. (b) the tafel plot for the system of tcnq/fe(cn)63-.j. am.chem.soc., 2003, 125, 9600, y. shao et al.sche

44、matic diagram of the application of secm to probe facilitated ion transfer at an externally polarized liquid/liquid interfaceprobing facilitated ion transfer at an externally polarized l/l interfaceexperimental approach curves of a 238-nm-radius pipet fitted with the theoretical values. the tip pote

45、ntial is 0.45v, the substrate potential is() 0.20v ()0.225v ()0.25v() 0.275v (*)0.30v ()0.325v ()0.35v()0.375v()0.40v () 0.425v ()curve 1 theoretical curve for diffusion controlled process, curves 2-6 theoretical curves for kinetics controlled process. the inset shows dependence of the heterogeneous rate constants on different es- eso.angew. chem.int. ed, 2002, 41(18), 3445-3448, y.shao et al. 由于液由于液/液界面本质上是一个分子软界面，本身处于动态液界面本质上是一个分子软界面，本身处于动态变化中，其特点是较难定义界面的结