Anodes switchable

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... 

Electrically switchable rear-view mirrors for cars and trucks have been in commercial production since the early 1990s, the leading company being the Gentex Corporation. The Gentex mirror consists of an ITO-glass surface, with the conductive side inwards, and a reflective metallic surface, spaced less than a millimetre apart. In the gap between these two electrodes is the solution electrolyte that is coloured at the anode by formation of the stable radical cation, similar to Wurster s... 

The photoisomerizable enzyme monolayer electrode also revealed photo-switchable bioelectrocatalytic activity (Figure 7.10). In the presence of ferrocene carboxylic acid (5) as a diffusional electron transfer mediatoi the nitrospiropyran-tethered GOx (4a) revealed a high bioelectrocatalytic activity, refleaed by a high electrocatalytic anodic current. The protonated nitromerocyanine-GOx (4b) exhibited a two-fold lower activity, as reflected by the decreased bioelectrocatalytic current. By the reversible photoisomerization of the enzyme electrode between the 4a- and 4b-states, the current responses are cycled between high and low values (Figure 7.10, inset). 

Cheng and co-workers recently reported Fc-cyclopeptides 12-15 (Scheme 5.4) and showed that they acted as redox-switchable cation receptors [26]. These Fc-cyclopeptides exhibited strong anodic shifts of their electrode potentials in the presence of alkaline earth metals and lanthanides. The extent of the anodic shift can be correlated with the charge density of the metal ion with a bias toward binding of lanthanides, alkaline earth metals, and the least sensitivity to alkaline metals [26]. Chowdhury et al, reported the syntheis and interaction of cychc Fc-Histidine conjagates 16 with metal ions (Scheme 5.5). Electrochemical measurements showed that the compound exhibited cathodic shifts in the order Na Li K+>Cs which in the order of their ionic sizes and suggest that the observed shift relates to the cavity of the compound [27]. 

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