Electroactive films electron transport properties

To assess the electron transport properties of our electroactive films, we applied a potential step from 0 to —0.65 V versus Ag/AgCl to an electrode coated with... 

When conferred with a hydrophilic head (in this case a substituted trityl unit), and a hydrophobic (benzylic alcohol) tail, rotaxanes - branched [55] or otherwise - can be formed into Langmuir films in a manner similar to catenanes. Rotaxane 224+ - synthesized from its corresponding thread via the slipping approach - when incorporated into a device in a manner similar to the catenane 214+ also exhibited interesting electron-transport properties [56], Unlike the catenane-based device, there is no switching element built into the molecule. However, like the switchable catenane, the rotaxane 224+ has electroactive bipyridinium sites, whose presence can mediate the tunneling of... 

In all cases, the films were obtained by oxidative electropolymerization of the cited substituted complexes from organic or aqueous solutions. The mechanism of metalloporphyrin Him formation was suggested to be a radical-cation induced polymerization of the substituents on the periphery of the macrocycle. As it was reported for the case of polypyrrole-based materials ", cyclic voltammetry and UV-visible spectroscopy with optically transparent electrodes were extensively used to provide information on the polymeric films (electroactivity, photometric properties, chemical stability, conductivity, etc.). Based on the available data, it appears that the electrochemical polymerization of the substituted complexes leads to well-structured multilayer films. It also appears that the low conductivity of the formed films, combined with the cross-linking effects due to the steric hindrance induced by the macrocyclic Ugand, confers to these materials a certain number of limitations such as the limited continuous growth of the polymers due to the absence of electronic conductivity of the films. Indeed, the charge transport in many of these films acts only by electron-hopping process between porphyrin sites. 

A powerful and elegant way to overcome the limitations encountered in redox polymers makes use of ion-exchange polymers (5). This class of modified electrode can be constructed using any polymer with ion-exchange properties by exchanging the native counter-ion for an appropriately charged electroactive ion. This ion will serve as the electron transfer site within and on the surface of the film. The result is a layer with the ability to transport electrons as illustrated in Figure 8.17B. 

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