电化学研究方法课件-北京大学邵元华教授 第三部分 2.ppt

1、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.Girault and D.J.Schiffrin, in Electroanalytical Chemistry, A.J.Bard., Ed.; Vol:15, p.1, Marcel D

2、ekker, New York ,1989 3. 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.1 4. J.Koryta, Electrochemical polarization phenomena at the interface of two immiscible electrolyte solutions. Electrochimica Acta, 24(1979)

3、293-300 5. J.Koryta, Electrochemical polarization phenomena at the interface of two immiscible electrolyte solutions. II. Progress since 1978. Electrochimica Acta, 29(1984)445-452 6. Volkov A G, Deamer D W. Liquid-liquid interfaces. Theory and Methods. California: CRC Press, 1996. 7. Volkov A G, Dea

4、mer 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/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 (electron and ion) transfer across Liquid/ Liquid (L/L) interfaces, o

5、r Oil/Water interfaces, or the interface between two immiscible electrolyte Solutions (ITIES) is one of the most fundamental physicochemical processes.,Brief history: 1902, Nernst and Riesenfeld 1906, Cremer pointed out that the analogy between the water/oil/water concentration cells and biological

6、membrane 1939, Verwey and Niessen, first theoretical paper on the electrical double layer and potential distribution at ITIES 1970s, Gavach et al. in France 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Modified Verwey-Niessen (MVN)对实验 结果进行了分析。随后

7、 Koryta et al. 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。Samec et al. in 1979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group 1986, Girault et al. 第一个将微-L/L界面支持在 Micropipettes 上 1991, Corn et al. 应用SHG研究L/L界面 1995，Mirkin and Bard et al. 应用SECM 研究L/L界

8、面 1997, Y.Shao et al. 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,NB 1,2-DCE,The difference between L/L interface and Electrode/Electrolyte interface,Electrochemistry of L/L interfaces,O + e = R,Redox Reactions,O + e = R,Redox Reactions,MZ (w) = MZ(o),Ion Transf

9、er,the conventional Electrochemistry,The difference between Electrochemistry at L/L interface and the conventional Electrochemistry,Electrochemistry at L/L Interfaces is the bridge between the conventional electrochemistry and Chemical sensors,Electrochemistry at Liquid/Liquid Interfaces is a fast w

10、ay to select receptors for making chemical sensors,Electrode,O,Biological Membrane Model,L/L Interface,Electrode/electrolyte,Membrane /solution,Artificial ,supported membrane and BLM,Electrochemistry at L/L Interfaces,New Branch of Electrochemistry,Mechanism of Chemical sensors,Phase Transfer cataly

11、tic reactions,Mimicking biological membranes,Research Significance and applications of Electrochemistry at L/L Interfaces,Extraction Mechanism,2.液/液界面电化学的基本原理,2.1.Equilibrium conditions and Nernst potential In general at Liquid/Liquid interfaces, there are two types of charge partition: (A) the tran

12、sfer of an ion M with the charge number z from the phase w to the phase o and the 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),Ner

13、nst Equations,Liquid/Liquid interfaces have been classified into the ideal-polarized interface and no-polarized interface.,2.2. Single ion Gibbs energy of transfer TATB assumption,2.3.Solvation of Ion Born equation,2.4.Interfacial structure and the ion transfer mechanism (A) MVN MODEL (B) GS MODEL,2

14、.5. Solvents and base electrolytes There 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 organic solvent: (1). The solubility of solvent in water and water in the

15、solvent must be very small. (2). The solvent must be sufficiently polar to promote sufficient dissociation of the supporting electrolyte and thus keeping enough conductivity of the solution. (3). The density of the solvent should differ significantly from that of aqueous phase in order to get a phys

16、ically stable l/l interface.,At present, the most commonly used organic solvents are nitrobenzene(NB) and 1,2-dichloroethane (1,2-DCE). Some other solvents have been tried in the past two decades, for example, propiophenone, 4-isopropyl-1-methyl-2-nitrobenzene, dichloro- methane,nitrotulene, chlorof

17、orm, 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 tetraphenylborate), TBATPBCl, CVTPB, BTPPATPB (Bistriphenylphosphoran

18、ylideneammonium tetraphenylborate),3.液/液界面电化学的主要研究方法 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-electrode potentiostat - Big iR drop aqueous solution dropping (ascending) electrode

19、two-electrode system - microelectrodes Recently, we developed a novel technique to study ITIES with three -electrode setup with the help of the phase ratio. Thus, all electrochemical labs can do research on this subjects.,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,Aqueou

20、s phase,新的技术，例如: SHG(Second harmonic generation) microelectrodes, micropipettes and nano-pipettes SECM Femto-laser Simulations Thin films 现已用在L/L Interfaces 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: MVN Model and GS Model Mechanism: Facilitated ion transfer mechanism Kinetics: Butler-Volmer equation

21、, Marcus theory Nanometeropipettes SECM Applications:Thin films (solar cell, drug delivery),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

22、. 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,How to solve these Problems,Microelectrodes: Solid and Nano- and Micropipettes,+,Scanning Electrochemical Microscopy, SECM,Electrochemistry at L/L Interfaces,Artificial Membrane/ Electrolyte Interfaces,BLM,Artificial Membrane and Biosensors,Modified L/L Interfaces,Micr

23、oelectrodes Nano- and Micropipettes,SECM,The SEM diagrams of Nano- and Micropipettes,Micropipettes,Nanopipettes,Micropipettes,Theta ()Micropipette,The SEM diagrams of Nano- and Micropipettes,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,Aqueous Phase,Organic Phase,Aqueous Phase,Organic

24、 Phase,Asymmetric Diffusion Field,TBATPB as supporting electrolyte in DCE,TBATPBCl as supporting electrolyte in DCE,BTPPATPB as supporting electrolyte in DCE,Micropipette as a tool to determine the ionic species limiting the potential window at L/L Interfaces,TBATPB (Tetrabutyalammonium tetraphenylb

25、orate),TBATPBCl(tetrabutyl- ammonium tetrakis4-chloro phenylborate),BTPPATPB (Bistriphosphor- anylideneammonium tetraphenyl- borate),1,2-dichloroethane (DCE),Ag/AgCl/0.01MTBACl/0.25mMDB18C6+0.01MTBATPBCl/0.01MKCl/AgCl/Ag,Identify the different mechanisms,ACT,TOC,TIC,TID,w,o,w,o,w,o,w,o,Identify of d

26、ifferent mechanisms of facilitated ion transfers,Idisk =4nFaDC,Ipip =3.35nFaDC,Why Ipip is about 2.63 times bigger than Idisk ?,Silanization plays very important role here!,Anal.Chem., 1998, 70,p3155-3161,3.4E-9,Nanometer-sized L/L Interface,纳米管 Nanopipet,Aqueous Phase,Nano-ITIES ko from 0.1cm/s to

27、10cm/s A 54nm radius B 5nm radius,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/Collection Mode。 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。,The photo of -micropipette under microscope,Anal.Chem., Y. Shao et al., 2003， 7

28、5，6593,“ Non-solution” L/L Interface Electrochemistry,Generator (1) and collector (2)voltammograms of the transfer of K+ between water and DCE containing DB18C6,ig vs. Eg and ic vs. Eg curves obtained with an aqueous film linking two barrels of the -pipet,Detection of ammonia in the air. Cyclic volt

29、ammogams obtained with a -pipet exposed to air (1) and ammonia vapor above its 2M solution,The potential windows 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% and 0.5% of Agar, respectively,Agar-water Microele

30、ctrode,Cyclic Voltammograms of K+ transfer facilitated by 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.,1,2,3,(a) r= 12 m,(b) r= 3 m.,Planar structure (a) and 3D structure (b) of a new t

31、ype of crown ether,Cyclic voltammogram with scan rate of 10mV/s for a 14m-radius micropipette electrode with 100 mM NaCl in aqueous phase and 10mM TBATPB in organic phase,Alkali metal ions transfer across the water/DCE interface Facilitated by DB18C6,Ion radius (r), formal transfer potential of rele

32、vant alkali metal ions and the association constants of complex (M-DB18C6)+ in DCE phase,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,Aqueous phase,Effect of the concentration Ratio of the redox couple,Sweep rate：100 mV/s. a, b, c, d, e correspond to (Ferri/ferrocynaide) 10, 5, 1, 0.2, 0.1,异

33、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。,Cyclic voltammograms 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

34、= 0.005; b. y = 0.05; c. y = 0.1; d. y = 0.5. Scan rate: 100 mV/s.,中国科学B, 2002, 32, 271-277，Y.Shao et al.,Ag/AgCl,Phase volume ratio r = VO/VW,Big r,Small r,A,B,Schematic 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

35、质子化药物的研究,Theoretical ionic partition diagram for a lipophilic base (equiconcentration convention).,Chemical structures 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-di

36、chloroethane interface at different pHs. Peak A correspond to the transfer of AMTLH+ and peak B correspond to that of TMA+.,Ionic partition diagrams for amitriptyline (AMTL), Diphenhydramine (DPAN) and Trihexyphenedyl (THPE) at the water / 1,2-dichloroethane interface,Anal.Chem., 2003, 75, 4341, Y.S

37、hao et al. 科学通报，2003， 48， 787, Y.Shao et al.,(a)The Tafel 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-

38、.,J. Am.Chem.Soc., 2003, 125, 9600, Y. Shao et al.,Schematic diagram of the application of SECM to probe facilitated ion transfer at an externally polarized Liquid/Liquid interface,Probing facilitated ion transfer at an externally polarized L/L interface,Experimental approach curves of a 238-nm-radi

39、us pipet fitted with the theoretical values. The tip potential 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.Sha