Beam studies using radiotracer techniques

Crossed Beam Studies of Chemical Kinetics Using Radiotracer Techniques... 

Nonsteady behavior of electrochemical systems was observed by Fechner as early as 1828 [ii]. Periodic or chaotic changes of electrode potential under gal-vanostatic or open-circuit conditions and similar variation of current under potentiostatic conditions have been the subject of numerous studies [iii,iv]. The electrochemical systems, for which interesting dynamic behavior has been reported include anodic or open-circuit dissolution of metals [v-vii], electrooxidation of small organic molecules [viii-xiv] or hydrogen, reduction of anions [xv, xvi] etc. [ii]. Much effort regarding the theoretical description and mathematical modeling of these complex phenomena has been made [xvii-xix]. Especially studies that used combined techniques, such as radiotracer (-> tracer methods) ig. 1) [x], electrochemical quartz crystal microbalance (Fig. 2) [vii,xi], probe beam deflection [xiii], surface plasmon resonance [xvi] surface stress [xiv] etc. have contributed considerably to the elucidation of the role of chemisorbed species ( chemisorption), surface reconstruction as well as transport phenomena in the mechanism of oscillations. 

A variety of other techniques have been used to investigate ion transport in conducting polymers. The concentrations of ions in the polymer or the solution phase have been monitored by a variety of in situ and ex situ techniques,8 such as radiotracer studies,188 X-ray photoelectron spectroscopy (XPS),189 potentiometry,154 and Rutherford backscatter-ing.190 The probe-beam deflection method, in which changes in the density of the solution close to the polymer surface are monitored, provides valuable data on transient ion transport.191 Rotating-disk voltammetry, using an electroactive probe ion, provides very direct and reliable data, but its utility is very limited.156,19 193 Scanning electrochemical microscopy has also been used.194... 

Other techniques than those described above, i.e., EQCM and probe beam methods, have been employed to study the ion transport phenomena. Horanyi and Inzelt [249] used a radiotracer method to study the anion involvement in the electrochemical reactions of PAn. The oxidation of leucoemeraldine to the radical... 

PBD involves the measurement of the deflection of a light beam, aligned parallel to the electrode surface [88-90, 194]. This in situ method is also a very convenient tool for the study of ion transport and reaction mechanism. The deflection is not significantly perturbed by solvent transfer between the polymer film and the solution. The combination of radiotracer and EQCM or EQCM and PBD techniques is especially useful because it allows access to individual ion and solvent flux contributions to mass transport dynamics [90]. 

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