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1、进入夏天，少不了一个热字当头，电扇空调陆续登场，每逢此时，总会想起进入夏天，少不了一个热字当头，电扇空调陆续登场，每逢此时，总会想起那一把蒲扇。蒲扇，是记忆中的农村，夏季经常用的一件物品。记忆中的故那一把蒲扇。蒲扇，是记忆中的农村，夏季经常用的一件物品。记忆中的故乡，每逢进入夏天，集市上最常见的便是蒲扇、凉席，不论男女老少，个个手持乡，每逢进入夏天，集市上最常见的便是蒲扇、凉席，不论男女老少，个个手持一把，忽闪忽闪个不停，嘴里叨叨着一把，忽闪忽闪个不停，嘴里叨叨着“怎么这么热怎么这么热”，于是三五成群，聚在大树，于是三五成群，聚在大树下，或站着，或随即坐在石头上，手持那把扇子，边唠嗑边乘凉。孩
2、子们却在周下，或站着，或随即坐在石头上，手持那把扇子，边唠嗑边乘凉。孩子们却在周围跑跑跳跳，热得满头大汗，不时听到围跑跑跳跳，热得满头大汗，不时听到“强子，别跑了，快来我给你扇扇强子，别跑了，快来我给你扇扇”。孩。孩子们才不听这一套，跑个没完，直到累气喘吁吁，这才一跑一踮地围过了，这时子们才不听这一套，跑个没完，直到累气喘吁吁，这才一跑一踮地围过了，这时母亲总是，好似生气的样子，边扇边训，母亲总是，好似生气的样子，边扇边训，“你看热的，跑什么？你看热的，跑什么？”此时这把蒲扇，此时这把蒲扇，是那么凉快，那么的温馨幸福，有母亲的味道！蒲扇是中国传统工艺品，在是那么凉快，那么的温馨幸福，有母亲的味
3、道！蒲扇是中国传统工艺品，在我国已有三千年多年的历史。取材于棕榈树，制作简单，方便携带，且蒲扇的表我国已有三千年多年的历史。取材于棕榈树，制作简单，方便携带，且蒲扇的表面光滑，因而，古人常会在上面作画。古有棕扇、葵扇、蒲扇、蕉扇诸名，实即面光滑，因而，古人常会在上面作画。古有棕扇、葵扇、蒲扇、蕉扇诸名，实即今日的蒲扇，江浙称之为芭蕉扇。六七十年代，人们最常用的就是这种，似圆非今日的蒲扇，江浙称之为芭蕉扇。六七十年代，人们最常用的就是这种，似圆非圆，轻巧又便宜的蒲扇。蒲扇流传至今，我的记忆中，它跨越了半个世纪，圆，轻巧又便宜的蒲扇。蒲扇流传至今，我的记忆中，它跨越了半个世纪，也走过了我们的半个人
4、生的轨迹，携带着特有的念想，一年年，一天天，流向长也走过了我们的半个人生的轨迹，携带着特有的念想，一年年，一天天，流向长长的时间隧道，袅长的时间隧道，袅北京大学电分析课件电分析化学新技术elec6Outline: 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. Spectros
5、copic 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）1.2 DefinitionCommon geometries include spherical, hemispherical, disc, ring, and line.1.2 DefinitionCommon geometries include spherical, hemispherical, disk, ring, and line.Most common is the disk UME, which can be fabricated by
6、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.Q
7、uite 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 et al. at Southampton University of U.K, and M.Wightman et al
8、. at Indiana University of USA started to work with very small electrodes. 1.4 Theory and applicationsResponses to a large-Amplitude Potential StepDisk UMEThe diffusion equation for species O is written as follows for this geometryWhere r describes radial position normal to the axis of symmetry at r
9、 = 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 conditionsAoki and Osteryoung addressed it in terms of a dimensionlessParameter, representing the squ
10、ared 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Summary of Behavior at UltramicroelectrodesAlthough there are some important differences in the behavior of UMEs with different shapes, it is useful here to recollect some
11、 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 t
12、he 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：Early transient regimeor the regime of semi-i
13、nfinite 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 spherical or hemispherical electrode for a various kinetic r
14、egimes.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, 5346-5351The SEM diagrams ofNano- and MicropipettesMicropipett
15、esNanopipettes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结束语结束语谢谢大家聆听！谢谢大家聆听！33
