Microband microdisk

Miniaturization of electrodes and of electrochemical cells has had considerable Impact on electrochemical sensor design as well as on fundamental electrochemical studies (9,29). Microelectrodes In particular have opened up new avenues for designing electrochemical sensors. Microelectrodes are physically small electrodes (microdisks have radii of 1-3 microns, microbands have widths down to ca 5 nm). Such... 

One of the characteristics of microelectrodes is an enhanced rate of mass transport of reactants and products to and from the electrode surface. Nonlinear diffusion prevails at microelectrodes two-dimensional diffusion at microcylinder or microband electrodes and three-dimensional diffusion at microspherical and microdisk electrodes. The enhanced mass transport at microelectrodes, which is often called the edge effect, causes increased current density and results in steady-state current responses at sufficiently slow potential sweep rates in potential sweep voltammetry, as will be illustrated in section 3. 

Craston, D.H., Jones, C.P., Williams, D.E. and Ehnurr, N. (1991) Microband electrodes fabricated by screen printing processes - applications in electroanalysis. Talanta, 38, 17-26. Farrington, A.M., Jagota, N. and Slater, J.M. (1994) Simple solid wire microdisk electrodes for the determination of vitamin-C in fruit juices. Analyst, 119, 233-238. 

Fig. 2.18 The most important geometries of microelectrodes and microelectrode arrays a microdisk b microring c microdisk array (a composite electrode) d lithographically produced microband array e microband f single fibre (microcylinder) g microsphere h microhemisphere i fibre array j interdigitated array. Image reproduced with permission from Ref. [7], copyright 2000 International Union of Pure and Applied Chemistry...

Amatore et al. developed a theoretical framework to describe the electrochanical responses of ultramicroelectrode ensemble and NEEs by considering mass transport for assemblies of microdisk and microband electrodes. Lee et al. used finite element simulation to solve 3D diffusion equations and found that a collection of 10 pm diameter microdisk electrodes required a separation distance of more than 40R to exhibit a sigmoidal simulated CV response typical for radial diffusion. " CV response typical of reversible linear diffusion at macroelectrodes was observed when the separation distance was less than 6R . Assemblies of microelectrodes for which the separation distances were between 6R and 4QR exhibited peak-shaped simulated CVs indicative of a mixture of radial and linear diffusion behavior. Thus, 12/ seems to be too small a separation distance for the design of ideal microelectrode arrays. 

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