北京大學電分析電分析化學新技術

1、Novel Techniques in,Electroanalytical Chemistry,電分析化學新技術,Yuanhua Shao,邵元華，教授,Ph.D,College of Chemistry and Molecular Engineering,Peking University,Outline,1. Ultramicroelectrode (microelectrode,超微電極或微電極,2. Electroanalytical chemistry at,liquid/liquid interfaces,液,液界面電分析化學,3. Scanning probe microscop

2、y,掃描探針顯微術,4. Spectroscopic techniques,光譜或波譜技術,5. Nano-electrochemistry,納米電化學,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

3、, 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 Instru

4、mental 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,電化學基礎，張祖訓，汪爾康,2000,10,生命科學中的電分析化學,彭圖治，楊麗菊,編著,1999,11,電極過程動力學導論,查全性,1976(1987 2,nd,Edition,12,電化學研究方法,田昭武,1984,13,電化學測定方法,騰島

5、,昭,等著,陳震等譯,1995,14,電分析化學,蒲國剛，袁倬斌，吳守國編著,1993,15,超微電極電化學,張祖訓,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.

6、, 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

7、Reviews,Websites,/estir,Part One,第一部分,1. Ultramicroelectrodes (UMEs)(microelectrodes,超微電極或微電極,1.1,Introduction,1.2,Definition,1.3,Brief History,1.4,Theory and applications,1.1,Introduction,導言,電分析化學在,60,年代末期基本上停止,不前，極譜學的研究已經(jīng)達到其最高峰,隨著其它分析化學技術的發(fā)展，極譜學越,來越不重要。光譜電化學及微電極的出現(xiàn),重新使電化學

8、及電分析化學獲得新生,M.Fleischmann, A.Bewick et al: 1970s to 1980s, in situ,光譜,波譜電化學,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 pra

9、ctice means between 0.1,and 50,m,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 25,m. This aspect is called,the critical dimension,Nano-electrodes: 1-1000 nm,m,mm,m,nm,10,0,10,3,10,6,10,9,1.2,Definition,C

10、ommon 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 exposin

11、g 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

12、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 an

13、d applications,Responses to a large-Amplitude Potential Step,Disk UME,2,2,2,2,1,O,O,O,O,C,r,z,t,C,r,z,t,C,r,z,t,C,r,z,t,D,t,r,r,r,z,g,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 describe

14、s 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,O,O,0,C,r,z,C,O,lim,O,r,C,r,z,t,C,O,lim,O,z,C,r,z,t,C,0,0,O,z,C,r,z,t,z,O,O,0,0,0,C,r,z,C,r,r,t,Aoki and Ostery

15、oung addressed it in terms of a dimensionless,Parameter, representing the squared ratio of the,diffusion length to the radius of the disk,2,O,O,4,D,t,r,電流時間曲線是,O,O,O,4,r,nFAD,C,i,f,當較短時間時, 1,1,2,1,2,0.88623,0.78540,0.094,f,當較長時間時,1,1,2,3,2,5,2,1,0.71835,0.05626,0.00646,f,從上述幾個公式可知，當,很大時，微園盤電極的穩(wěn)態(tài)電流為,

16、O,O,O,O,O,O,4,4,r,SS,nFAD,C,i,nFD,C,r,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

17、, 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 a

18、ny UME,approaches a steady state or a quasi-steady state. One can write the,current in this limit as following,O,O,SS,i,nFAm,C,對于最簡單的情況，球形電極的情況，其電流時間的,關系是,1/2,O,O,O,O,1,2,1,2,O,r,nFAD,C,nFAD,C,i,t,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