Electrocatalysis, molecular devices

Tliis work demonstrates the potential for application of potentiometric enzyme electrodes based on mediatorless enzyme electrocatalysis for fast and sensitive assay of organophosphorus pesticides. The sensing element based on screen-printed carbon material pomits mass fabrication of the electrodes at a low cost which is essential for the disposable sensor concept. The biosensor does not require any low-molecular weight mediator and can be arranged as an all-solid-state device. Such electrodes. 

Clay modified electrodes are used in fundamental studies of electron transfer, and in the construction of sensor devices. The ionic aqueous environment in the interlayer region is highly amenable to electrochemical processes. Furthermore, this enviromnent is controllable and fairly innocuous, allowing many different species to retain their activity. Molecular recognition, chemical catalysis, electrocatalysis, and preconcentration of analyte molecules are all applications of this class of modified electrodes. A condensed list of clay modified electrodes is given in Table 8.4. Reference (96), Table 6.1 on pages 280-281 contains a more comprehensive list. 

Modified electrodes have many applications. A primary interest has been in the area of electrocatalysis. In this application, electrodes capable of reducing oxygen to water have been sought for use in fuel cells and batteries. Another application is in the production of electrochromic devices that change color on oxidation and reduction. Such devices are used in displays or smart nindmvs and mirrors. Electrochemical devices that could serve as molecular electronic devices, such as diodes and transistors, arc also under intense study. Finally, the most important analytical use for such electrodes is as analytical sensors selective for a particular species or functional group (sec Figure 1-7). 

We note that electrocatalysis and photocatalysis are often closely related phenomena. Figure 11.1 illustrates the working principles of a photocatalytic device for water splitting based on a semiconductor, which can absorb sunlight, and two electrocatalysts (one or both of which could in principle be the same material as the semiconductor). One of the catalysts uses the excited electrons in the conduction band to form molecular hydrogen ... 

---