Electrochemically selective patterns

These types of switchable electrode surfaces have been used to selectively pattern two different cell populations onto a surface [151] and additionally these surfaces can selectively release different cells at different applied potentials [152]. However, it is important to recognize that electrochemically switching a surface from inactive to conjugation and active to conjugation has been well explored with nitro-terminated aryl diazonium salts. In such studies, the application where very anodic potential resulted in a six-electron reduction to an amine [139], to which proteins could be attached [153-155]. The key difference is that the interaction of the biological medium with the surface is controlled by the presence of the antifouling layer. In many ways these electrode surfaces developed by Mrksich and coworkers [150-152, 156] are very similar to the antifouling surfaces with molecular wires discussed in Section 1.4.2 [131, 132, 138, 142]. In both cases the electrode is... 

Therefore, to prepare a selective anion sensor for less lipophilic anions in the series, the selective interactions between the ionophores and the targeted anion should be considered. Truly selective nitrate electrodes were developed by the electrochemical deposition of PPy onto glassy carbon electrodes in the presence of NaNOa [131]. As seen in Figure 8.79, the selectivity pattern of PPy(N03 ) electrodes exhibited a significant deviation firom the Hofineister series. The electrodes showed selectivity especially for nitrate and thiocyanate, while the commercially available nitrate-selective electrodes were affected by the more lipophilic anions including iodide and perchlorate. 

The electrochemical machining (ECM) of metals rests on the selective local anodic dissolution of metal. It is used to give metal parts the required shape and size, to drill holes, create hollows, cut shaped slots, and fashion parts of a complex pattern (e.g., the blades of gas turbines). It is an advantage of this method that it can also be used for hard metals (high-alloy steels and other alloys, metals in the quenched state, etc.). 

In [53], oscillatory wave patterns observed during electrochemical dissolution of a nickel wire in acidic media was reported. It was shown that space-averaged potential or current oscillations are associated with the creation of an inhomogeneous current distribution, and that the selection of a specific spatial current pattern depends on the current control mode of the electrochemical cell. In the almost potentiostatic (fixed potential) mode of operation, a train of traveling pulses prevails, whereas antiphase oscillations occur in the galvanostatic (constant average current) mode. 

An electrochemical flow detector, based on four working electrodes coated with different permselective film types, for use in flow-injection measurements of multiple nitroaromatic explosives was recently developed [18]. The resulting array response (Fig. 4) offers unique fingerprints of such explosive compounds. Electrochemical devices are extremely attractive for designing such e-nose-type multi-electrode arrays that combine several partially selective electrodes and lead to a distinct response pattern (signature) for mixtures of organic vapors without prior separation [2],... 

This section describes the formation of metals and metal alloys from metal enolate precursor sources (/3-diketonates, /3-ketoiminates) where chemical vapor deposition, spin coating and electrochemical deposition processes are used to generate blanket, surface selective or patterned surface structures. 

Figure 16 Schematic representation of the reaction pattern for the oxidation of organic compounds with simultaneous oxygen evolution at metal-oxide anodes reactions (a), (b), (c), d) as in Figure 11 (e) combustion of the organic compound R via electrochemical oxidation mediated by physisorbed hydroxyl radicals (/) selective chemical oxidation of the organic compound at the higher metal oxide surface sites. (From Ref. 15. Copyright 1994, Pergamon Press Ltd. Reprinted with permission.)...

A. Speigel, L. E. Erickson, and P. Schmuki, Selective growth of porous silicon on focused ion beam patterns, J. Electrochem. Soc. 147, 2993, 2000. 

J. L. Valdes, J. W. Mitchel, J. A. Mucha, L. Seibles, and H. Huggins, Selected-area nucleation and patterning of diamond thin films by electrophoretic seeding, J. Electrochem. Soc., 138 (2) 635-636 (1991)... 

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