Positioning techniques, scanning electrochemical microscopy

The scanning electrochemical microscopy (SECM) technique introduced in recent years by Allen Bard is another area where the smallness of the electrode is essential [38]. The principle in SECM is a mobile UME inserted in an electrolyte solution. The UME is normally operated in a potentiostatic manner in an unstirred solution so that the current recorded is controlled solely by the spherical diffusion of the probed substance to the UME. The current can be quantified from Eqs. 48, 49, or 89 as long as the electrode is positioned far from other interfaces. However, if a solid body is present in the electrolyte solution, the diffusion of the substance to the UME is altered. For instance, when the position of the UME is lowered in the z direction, that is, towards the surface of the object, the diffusion will be partially blocked and the current decreases. By monitoring of the current while the electrode is moved in the x-y plane, the topology of the object can be graphed. The spatial resolution is about 0.25 pm. In one investigation carried out by Bard et al, the... 

A few years ago Bard and his group developed the technique called scanning electrochemical microscopy (SECM) which makes possible a spatial analysi,s of charge transfer processes [9]. In this method an additional tip electrode of a diameter of about 2 pm is used as well as the three other electrodes (semiconductor, counter and reference electrode). Assuming that a redox system is reduced at the semiconductor, then the reduced species can be re-oxidized at the tip electrode, the latter being polarized positively with respect to the redox potential. The corresponding tip current / [ is proportional to the local concentration of the product formed at the semiconductor surface and therefore also to the corresponding local semiconductor current, provided... 

Scanning electrochemical microscopy (SECM, see Chapter 12) is another microelectrode technique that has been used at the cellular surface. Briefly, with SECM a microelectrode (UME, see Chapter 6) functions as a scanning probe that detects local electrochanical activity. When the UME is rastered over a sample, electrochemical data is recorded at multiple positions and an image is constructed based on the local electrochemical properties of the area of interest SECM has been thoroughly reviewed (19,20,52, Chapter 12 of this... 

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