NON-ELECTROCHEMICAL PROBES OF ELECTRODES AND ELECTRODE PROCESSES

Spectroscopic techniques can be carried out in situ (low-energy photon, etc.) and ex situ or in vacuo (high-energy photon and electron techniques). Ex situ microscopic techniques have been employed for many years to examine surfaces, and are now widely used tools. However, in situ microscopic techniques with resolution approaching the atomic scale 

Electromagnetic radiation, besides being a probe of surface structure, can excite electrons in the species in solution (especially in organic compounds) or in the electrode itself (especially in semiconductor electrodes). This photon excitation can lead to electron transfer between electrode and solution. The study of these phenomena is photoelectrochemistry and can be very important in conversion of solar energy into electricity in order to convert substances (photoelectrolysis). 

A slightly different application is where species produced electrochem-ically lead to photon emission in the visible spectrum, via the formation of organic radicals by homogeneous reaction from electrochemically generated precursors. The electrode controls the quantity of precursor, enabling quantitative parameters of the homogeneous reaction to be elucidated. This is known as electrogenerated chemiluminescence or electrochemiluminescence (ECL). 

---

Non-electrochemical probes of electrodes and electrode processes Scanning electrochemical microscopy (SECM)54... 

Although on the basis of current-potential relationships important conclusions can be drawn regarding the mechanism of the electrode processes - especially if the experimental parameters are varied over a wide range - the use of combined electrochemical and non-electrochemical methods is inevitable to elucidate the mechanism of the complex electrode processes. As we will see later in this volume, a great variety of advanced electrochemical and in situ probes are available which give different types of information and therefore provide a better insight into the nature of the chemical events that occur during electrochemical reactions. The solid theoretical foundations and the relative simplicity of the final formulae and techniques make electroanalysis an attractive and powerful tool to obtain fast and reliable information on chemical systems. 

Many of these approaches rely on the differential hybridization of target DNAs that are perfectly matched with probe sequences to achieve highly specific and accurate target selection. Other assays use the sensitivity of DNA-mediated charge transport to duplex structure in order to signal the presence of a sequence of interest. Efforts also have been directed toward exploiting non-faradaic processes unique to DNA-modified surfaces as the basis for electrochemical readout. This chapter discusses each of these methods, and is intended to highlight how the DNA/electrode interface can... 

---