北京大学 电分析 课件 电分析化学新技术 elec.ppt

Novel Techniques in Electroanalytical Chemistry 电分析化学新技术 Yuanhua Shao（邵元华，教授 Ph.D.） College of Chemistry and Molecular Engineering Peking University,Outline: 1. Ultramicroelectrode (microelectrode) (超微电极或微电极） 2. Electroanalytical chemistry at liquid/liquid interfaces (液/液界面电分析化学) 3. Scanning probe microscopy (扫描探针显微术） 4. Spectroscopic techniques (光谱或波谱技术） 5. Nano-electrochemistry (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.Brett, Electrochemistry, Principles, Methods, and Applications, Oxford, 1993 3 * Southampton Electrochemistry Group, New Instrumental Methods in Electrochemistry, Ellis Horwood, Chichester, 1985 4 A.M.Bond, Modern polarographic methods in Analytical Chemistry, Dekker, New York, 1980 5 J.Koryta, Principles of Electrochemistry, Wiley, 1987 6 P. Delahay, New Instrumental methods in Electrochemistry, 1954 7 R.N.Adams, Electrochemistry at solid electrodes, 1969 8 *J.OM.Bockris and A.N.Reddy, Modern Electrochemistry, Plenum, New York, 1970 9 电化学基础，张祖训，汪尔康， 2000 10生命科学中的电分析化学， 彭图治，杨丽菊 编著, 1999 11 *电极过程动力学导论， 查全性， 1976(1987 2nd Edition) 12电化学研究方法， 田昭武， 1984 13*电化学测定方法， 腾岛 昭 等著， 陈震等译， 1995 14电分析化学， 蒲国刚，袁倬斌，吴守国编著， 1993 15超微电极电化学， 张祖训，1998,Series 1. Electroanalytical Chemistry, ed. A.J.Bard 2. Modern Aspects of Electrochemistry, eds. J.OM.Bockris, B.E.Conway, et al., Journals Nature, Science, JACS, Angew.Chem.Int Edit Anal.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 Electrochemistry,Reviews: Accounts of Chemical Research Analytical Chemistry Annual Reviews of Physical Chemistry Chemical Reviews Websites: /estir/,Part One ( 第一部分) 1. Ultramicroelectrodes (UMEs)(microelectrodes) (超微电极或微电极） 1.1 Introduction 1.2 Definition 1.3 Brief History 1.4 Theory and applications,1.1 Introduction (导言),电分析化学在60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。 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 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 - 1980s,1.2 Definition,Microelectrodes 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 Width of a band) smaller than 25m. This aspect is called the critical dimension.,Nano-electrodes: 1-1000 nm,m mm m nm,100 10-3 10-6 10-9,1.2 Definition,Common geometries include spherical, hemispherical, disc, ring, and line.,1.2 Definition,Common geometries include spherical, hemispherical, disk, ring, and line.,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 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 history,In the late 1970s, M.Fleischmann et 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 applications,Responses to a large-Amplitude Potential Step,Disk UME,The diffusion equation for species O is written as follows for this geometry,Where 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 condition and two semi- infinite conditions,Aoki and Osteryoung addressed it in terms of a dimensionless Parameter, representing the squared ratio of the diffusion length to the radius of the disk.,电流时间曲线是,当较短时间时 1,当较长时间时 1,从上述几个公式可知，当很大时，微园盘电极的稳态电流为,Summary of Behavior at Ultramicroelectrodes,Although there are some important differences in the behavior of UMEs with different shapes, it is useful here 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 long 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:,对于最简单的情况，球形电极的情况，其电流时间的 关系是：,Early transient regime or the regime of semi- infinite linear diffusion,Long-time limit Steady-state regime,UMEs have extended electrochemical methodology into broad new domains of space, time, chemical medium, and methodology,Applications,Kinetic measurements,Steady-state voltammograms at a 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,Method of Mirkin and Bard 2. Curve fitting,size,Biological System,ORGANISM,TISSUES CELLS,AMINO ACIDS H2O, CO2,PROTEINS POLYPEPIDE,MEMBRANE ENZYME,半径 (A) 91； (B)27； (C)1.8 nm,Anal.chem.,2001, 73, 5346-5351,The SEM diagrams of Nano- and Micropipettes,Micropipettes,Nanopipettes,我们group可以