Electrochemically generated species

Rapid polymerization of electrochemically generated species such as organic radicals can cover an electrode with a polymeric film. Such films are sometimes impenetrable and difficult to remove, which results in passivation of the electrode surface. A typical case is the oxidation of 1,2-diaminobenzene [9]. The modification of electrode properties by coating with thin polymer films is currently an area of active investigation [10— 12]. 

Chronoamperometric transduction can be applied to electroinactive analytes as well as electroactive, which are sorbed by the MIP film and then undergo an electrochemical reaction [25]. In the latter case, the analyte should be able to diffuse freely both towards and away from the electrode surface for the current to flow. The primary requirement of chronoamperometric sensing is a linear relationship between the current measured at the constant potential and the concentration of the analyte. Moreover, the electrochemically generated species should readily diffuse away from the electrode surface coated by the sensing film. By way of example, a few representative chronoamperometric sensors based on MIPs are presented below. 

Investigation of One-Dimensional Species and of Electrochemically Generated Species... 

Resonance Raman spectroscopy, well known to be a sensitive probe of the nature of charge-transfer excited states, is now established to be a sensitive probe of intervalence states. In particular, onedimensional systems prove to be very amenable to study, and the results on a variety of linear-chain platinum complexes of both the Wolffram s red sort as well as the pop sort (pop = H2P2O52 ) are outlined. Brief mention is made of the application of resonance Raman spectroscopy to the study of electrochemically generated species. 

Thin layer electrochemistry thus offers a very convenient way of controlling the oxidation state of a very thin (< 1 mm) layer of an electrochemically generated species. 

The electrochemistry of cluster compounds is still an underdeveloped area (75,76). A recent study has shown interesting differences in the redox behaviors of the isostructural compounds Fe4(CO),2Au2(PPh3)2BH and Fe4(CO),2Au2(AsPh3)2BH. Each undergoes a one-electron reduction and oxidation, but only the phosphine derivative can be oxidized further to the dication. All electrochemically generated species are short lived (71). 

Finally, mention should be made of a new generation of channel flow cells, in which the electrochemically generated species are transported by a laminar flow from the working electrode to an optically transparent part of the cell [316-318]. 

High localization of the positive charge on the Se atom in electrochemically generated species often results in many interesting processes, both possibly involving a cleavage of bonds formed by Se. 

One should not see the potentiometric mode as an alternative but as a complement to the amperometric mode. The potentiometric mode offers the possibility of performing measurements on non-redox active species, e.g., not detectable amperometrically in aqueous solutions. Another advantage is the increased selectivity of the potentiometric response compared to the Faradaic response. The logarithmic response is also useful when the species of interest is in low concentrations. Since the tip is passive, only substrate generation-tip detection experiments are possible. However, the tip does not alter the concentration profile of the chemically or electrochemically generated species. The potentiometric micropipette tips have very small dimensions, typically 1 /xm or less, and the shielding is minimal. 

Hercules DM (1964) Chemiluminescence resulting fiom electrochemically generated species. Science (New York, NY) 145 (3634) 808-809. doi 10.1126/science.145.3634.808... 

Classical ECL involves the formation of an excited state as a result of an energetic electron transfer between electrochemically generated species, often radical ions, at the surface of... 

Menshykau D, Cortina-Puig M, del Ctimpo FJ, Munoz FX, Compton RG (2010) Plane-recessed disk electrodes and their arrays in transient generator-collector mode the measurement of the rate of the chemical reaction of electrochemically generated species. J Electroanal Chem 648 28-35... 

---