Interfacial materials controlling electrode

The schemes in Figs. 44 and 45 may serve to summarize the main results on photoinduced microwave conductivity in a semiconductor electrode (an n-type material is used as an example). Before a limiting photocurrent at positive potentials is reached, minority carriers tend to accumulate in the space charge layer [Fig. 44(a)], producing a PMC peak [Fig. 45(a)], the shape and height of which are controlled by interfacial rate constants. Near the flatband potential, where surface recombination... 

Electrodes represent an unrivaled platform onto which interfacial supramolecular structures can be assembled. They can be fully characterized before assembly and offer a convenient means to both probe and control the properties of the film. The interest in this area has increased dramatically in recent years because adsorbed monolayers enable both the nature of the chemical functional groups and their topology to be controlled. This molecular-level control allows the effects of both chemical and geometric properties on electron transfer rates to be explored. Moreover, these assemblies underpin technologies ranging from electrocatalysis to redox-switchable non-linear optical materials. 

The modification of electrode surfaces with electroactive polymer films provides a means to control interfacial characteristics. With such a capability, one can envisage numerous possible applications, in areas as diverse as electronic devices, sensors, electrocatalysis, energy conversion and storage, electronic displays, and reference electrode systems [1, 2]. With these applications in view, a wide variety of electroactive polymeric materials have been investigated. These include both redox polymers (by which we imply polymers with discrete redox entities distributed along the polymer spine) and conducting polymers (by which we imply polymers with delocalised charge centres on the polymer spine). 

This fact has a large implication for material science, because as material science deals predominantly with interfacial phenomena [i.e., the stability and material properties are controlled by interfaces (external or internal)], there is an electrical character about these happenings and thus they are subject to electrochemical science and electrochemical arguments. The main difference in an electrochemical (compared with a chemical) reaction, of course, is that an electronic charge transfer occurs in the electrochemical one. However, there are other differences which do not meet the eye. Electrochemical reactions always occur in two different locations. One cannot have an electrode operating in isolation in a solution. It always must be adjoined to another electrode, by an external circuit, in which electrons pass through a wire, and at this other electrode another electrochemical reaction takes place (Figure 2). 

SAMs are already established as providing a range of functions. They control surface properties such as interfacial free energy [76], wettability [58, 77, 78] and adhesion strength [79-81] they influence corrosion [82] and adhesion [83-85] they can act as resists [59, 60, 86, 87] they serve as electroactive layers on electrodes [88-94]. Many more functions will undoubted be developed for this class of materials. Hydrogen-bonded aggregates have, as yet, no functions. 

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