北京大学-电分析-课件-电分析化学新技术-elec6.ppt

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1、 Novel Techniques in Electroanalytical Chemistry 电分析化学新技术电分析化学新技术 Yuanhua Shao（邵元华，教授（邵元华，教授 Ph.D.） College of Chemistry and Molecular Engineering Peking UniversityOutline:1. Ultramicroelectrode (microelectrode)(超微电极或微电极）超微电极或微电极）2. Electroanalytical chemistry at liquid/liquid interfaces(液液/液界面电分析化学

2、液界面电分析化学)3. Scanning probe microscopy(扫描探针显微术）扫描探针显微术）4. Spectroscopic techniques(光谱或波谱技术）光谱或波谱技术）5. Nano-electrochemistry(纳米电化学）纳米电化学）General Books:1* A.J.Bard and L.R.Faulkner, Electrochemical methods, fundamentals and applications, Wiley, New York, 1980(2nd Edition, 2001)2 * C.M.A.Brett and A.M.O

3、.Brett, Electrochemistry, Principles, Methods, and Applications, Oxford, 19933 * Southampton Electrochemistry Group, New Instrumental Methods in Electrochemistry, Ellis Horwood, Chichester, 19854 A.M.Bond, Modern polarographic methods in Analytical Chemistry, Dekker, New York, 19805 J.Koryta, Princi

4、ples of Electrochemistry, Wiley, 19876 P. Delahay, New Instrumental methods in Electrochemistry, 19547 R.N.Adams, Electrochemistry at solid electrodes, 19698 *J.OM.Bockris and A.N.Reddy, Modern Electrochemistry, Plenum, New York, 19709 电化学基础，张祖训，汪尔康， 200010生命科学中的电分析化学， 彭图治，杨丽菊 编著, 199911 *电极过程动力学导论，

5、 查全性， 1976(1987 2nd Edition)12电化学研究方法， 田昭武， 198413*电化学测定方法， 腾岛 昭 等著， 陈震等译， 199514电分析化学， 蒲国刚，袁倬斌，吴守国编著， 199315超微电极电化学， 张祖训，1998Series1. Electroanalytical Chemistry, ed. A.J.Bard2. Modern Aspects of Electrochemistry, eds. J.OM.Bockris, B.E.Conway, et al., JournalsNature, Science, JACS, Angew.Chem.Int

6、EditAnal.Chem.,(May 1, 2000) J.Phys.Chem.B.,J.Electroanal.Chem., Electrochimica Acta, J.Electrochem.Society.,Electroanalysis, Electrochemical and Solid State Letters, J.Applied Electrochemistry, Electrochemistry Communications, J.Solid State ElectrochemistryReviews:Accounts of Chemical ResearchAnaly

7、tical ChemistryAnnual Reviews of Physical ChemistryChemical ReviewsWebsites:http:/electrochem.cwru.edu/estir/Part One ( 第一部分第一部分)1. Ultramicroelectrodes (UMEs)(microelectrodes)(超微电极或微电极）超微电极或微电极） 1.1Introduction1.2Definition1.3Brief History1.4Theory and applications1.1 Introduction (导言导言)电分析化学在电分析化学

8、在60年代末期基本上停止年代末期基本上停止不前，极谱学的研究已经达到其最高峰。不前，极谱学的研究已经达到其最高峰。随着其它分析化学技术的发展，极谱学越随着其它分析化学技术的发展，极谱学越来越不重要。光谱电化学及微电极的出现来越不重要。光谱电化学及微电极的出现重新使电化学及电分析化学获得新生！重新使电化学及电分析化学获得新生！M.Fleischmann, A.Bewick et al: 1970s to 1980s, in situ 光谱、波谱电化学M.Fleischmann, M.Wightman et al: ultramicroelectrodes 1970s - 1980s1.2 Def

9、initionMicroelectrodes or ultramicroelectrodes are defined as Electrodes which have at least one dimension that is a function of its size, which in practice means between 0.1 and 50m. We define a UME operationally as an electrode having at least one dimension (such as the radius of a disk or the Wid

10、th of a band) smaller than 25m. This aspect is called the critical dimension.Nano-electrodes: 1-1000 nmm mm m nm100 10-3 10-6 10-91.2 DefinitionCommon geometries include spherical, hemispherical, disc, ring, and line.1.2 DefinitionCommon geometries include spherical, hemispherical, disk, ring, and l

11、ine.Most common is the disk UME, which can be fabricated by sealing a fine wire in an insulator, such as glass or a plastic resin, and then exposing and Polishing a cross-section of the wire.Spherical UMEs can be made for gold, but are difficult to realize for other materials. Hemispherical UMEs can

12、 be achieved by plating mercury onto a microelectrode disk.Quite different is the band UME, which has as its critical dimension a width, w, in the range below 25 m. The length, L, can be much larger, even in the centimeter range.Cylindrical UME etc.1.3 Brief historyIn the late 1970s, M.Fleischmann e

13、t al. at Southampton University of U.K, and M.Wightman et al. at Indiana University of USA started to work with very small electrodes. 1.4 Theory and applicationsResponses to a large-Amplitude Potential StepDisk UME2222( , , )( , , )( , , )( , , )1OOOOCr z tCr z tCr z tCr z tDtrrrzThe diffusion equa

14、tion for species O is written as follows for this geometryWhere r describes radial position normal to the axis of symmetry at r = 0, and z describes linear displacement normal to the plane of the electrode at z =0.Five boundary conditions are needed for a solution. Three come from the initial condit

15、ion and two semi-infinite conditions*OO( , ,0)Cr zC*Olim( , , )OrCr z tC*Olim( , , )OzCr z tC0( , , )0OzCr z tz*OO0( , ,0)(,0)Cr zCrr tAoki and Osteryoung addressed it in terms of a dimensionlessParameter, representing the squared ratio of the diffusion length to the radius of the disk.2OO4/D t r电流时

16、间曲线是*OOO4( )rnFAD Cif当较短时间时 11/23/25/2( )1 0.718350.056260.00646.f 从上述几个公式可知，当从上述几个公式可知，当 很大时，微园盘电极的稳态电流为很大时，微园盘电极的稳态电流为*OOOO OO44rSSnFAD CinFD C rSummary of Behavior at UltramicroelectrodesAlthough there are some important differences in the behavior of UMEs with different shapes, it is useful here

17、 to recollect some common features in the responses to a large-amplitude potential Step:First, at short time, where the diffusion-layer thickness is small compared to the critical dimension, the current at any UME follows the Cottrell equation, and semi-infinite linear diffusion applies.Second, at l

18、ong times, where the diffusion-layer thickness is large compared to the critical dimension, the current at any UME approaches a steady state or a quasi-steady state. One can write the current in this limit as following:*OOSSinFAm C对于最简单的情况，球形电极的情况，其电流时间的对于最简单的情况，球形电极的情况，其电流时间的关系是：关系是：1/2*OOOO1/2 1/2

19、OrnFAD CnFAD CitEarly transient regimeor the regime of semi-infinite linear diffusionLong-time limitSteady-state regimeUMEs have extended electrochemical methodology into broad new domains of space, time, chemical medium, and methodologyApplicationsKinetic measurementsSteady-state voltammograms at a

20、 spherical or hemispherical electrode for a various kinetic regimes.最常用的采用稳态伏安法获取动力学数据的方法最常用的采用稳态伏安法获取动力学数据的方法1. Method of Mirkin and Bard2. Curve fittingsizeBiological SystemORGANISMTISSUES CELLSAMINO ACIDSH2O, CO2 PROTEINSPOLYPEPIDE MEMBRANE ENZYME半径半径 (A) 91； (B)27； (C)1.8 nmAnal.chem.,2001, 73,

21、5346-5351The SEM diagrams ofNano- and MicropipettesMicropipettesNanopipettes我们我们group可以制备内径从几个可以制备内径从几个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 FieldAg/AgCl/0.01MTBACl/0.25mMDB18C6+0.01MTBATPBCl/0.01MKCl/AgCl/AgIdentify the different mechanismsACTTOCTICTIDwowowowoIdentify of different mechanisms of facilitated ion transfers