Voltammetry scanning electrochemical microscopy

The time range of the electrochemical measurements has been decreased considerably by using more powerful -> potentiostats, circuitry, -> microelectrodes, etc. by pulse techniques, fast -> cyclic voltammetry, -> scanning electrochemical microscopy the 10-6-10-1° s range has become available [iv,v]. The electrochemical techniques have been combined with spectroscopic ones (see -> spectroelectrochemistry) which have successfully been applied for relaxation studies [vi]. For the study of the rate of heterogeneous -> electron transfer processes the ILIT (Indirect Laser Induced Temperature) method has been developed [vi]. It applies a small temperature perturbation, e.g., of 5 K, and the change of the open-circuit potential is followed during the relaxation period. By this method a response function of the order of 1-10 ns has been achieved. 

Alpuche-Aviles, M.A., Baur, J.E. and Wipf, D.O. (2008) Imaging of metal ion dissolution and electrodeposition by anodic stripping voltammetry-scanning electrochemical microscopy. Analytical Chemistry, 80, 3612—3621. 

The time range of the electrochemical measurements has been decreased considerably by using more powerful -> potentiostats, circuitry, -> microelectrodes, etc. by pulse techniques, fast -> cyclic voltammetry, -> scanning electrochemical microscopy the s range... 

Schrock, D. S., Wipf, D. O., Baur, J. E. Feedback effects in combined fast-scan cyclic voltammetry-scanning electrochemical microscopy. Ana/. Chem. 2007, 79, 4931-4941. 

L. Diaz-Ballote, M. Alpuche-Aviles, D.O. Wipf. East-scan cyclic voltammetry-scanning electrochemical microscopy. J Electroanal Chem. 604 17 (2007). 

FAST SCAN CYCLIC VOLTAMMETRY-SCANNING ELECTROCHEMICAL MICROSCOPY... 

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... 

Topics discussed above are some basic principles and techniques in voltammetry. Voltammetry in the frequency domain where i-E response is obtained at different frequencies from a single experiment known as AC voltammetry or impedance spectroscopy is well established. The use of ultramicroelectrodes in scanning electrochemical microscopy to scan surface redox sites is becoming useful in nanoresearch. There have been extensive efforts made to modify electrodes with enzymes for biosensor development. Wherever an analyte undergoes a redox reaction, voltammetry can be used as the primary sensing technique. Microsensor design and development has recently received... 

UMEs decrease the effects of non-Earadaic currents and of the iR drop. At usual timescales, diffusional transport becomes stationary after short settling times, and the enhanced mass transport leads to a decrease of reaction effects. On the other hand, in voltammetry very high scan rates (i up to 10 Vs ) become accessible, which is important for the study of very fast chemical steps. For organic reactions, minimization of the iR drop is of practical value and highly nonpolar solvents (e.g. benzene or hexane [8]) have been used with low or vanishing concentrations of supporting electrolyte. In scanning electrochemical microscopy (SECM [70]), the small size of UMEs is exploited to locahze electrode processes in the gm scale. 

ET reactions at the polarizable - interface between two immiscible electrolyte solutions (ITIES) have been studied by cyclic voltammetry [ii], AC impedance [iii], and scanning electrochemical microscopy (SECM) [iv]. A simple method was introduced that allows evaluation of the ET rates at the interface between the thin film of an organic solvent and the aqueous electrolyte solution [v]. 

Refs. [i] Bard AJ, FaulknerLR (2001) Electrochemical methods, 2nd edn. Wiley, New York, chaps. 5, 6, 9, 11, 12 [ii] Bard AJ, Mirkin MV (eds) (2001) Scanning electrochemical microscopy. Marcel Dekker, New York [Hi] Oldham KB, Myland JC (1994) Fundamentals of electrochemistry. Academic Press, New York, chap. 8 [iv] Zoski CG (1996) Steady-state voltammetry at microelectrodes. In Vanysek P (ed) Modern techniques in electro analysis. Wiley, New York... 

A recent introduction of scanning electrochemical microscopy (SECM) to this field [16-23] has revitalized the study of ET at the OAV interface. In contrast to the conventional, four-electrode cyclic voltammetry at externally polarized OAV interfaces, the SECM measurements not necessarily require supporting electrolytes, and thus can be carried out over a wide range of driving forces without the limitation of the potential window. This advantage of SECM allowed for an experimental verification of the Marcus theory in the driving-force dependence of the ET rate constant [18,21]. 

Speiser, B., From cyclic voltammetry to scanning electrochemical microscopy Modem electroanalytical methods to study organic compounds, materials, and reactions, Curr Org. Chem. 1999, 3, 171-191... 

Recently new methods, based on petturbations on the linear sweep voltammetry response of the mediator in the presence of the protein," a mediated thin-layer voltammetry technique, cyclic voltammetric simulation apphed to an electrochemically mediated enzyme reaction" have been setded to gain information on the protein-mediator interactions. More recendy the Scanning Electrochemical Microscopy (SECM) was used to probe the red-ox activity of individual cells of purple bacteria, by using two groups of mediators (hydrophilic and hydrophobic species) in order to gain information on the dependence of measured rate constant on the formal potential of the mediator in solution. By this technique an evaluation of the intracellular potential was also performed. ... 

The research of Mallouk and Smotkin [45] considered combinatorial catalyst development methods. In the combinatorial research, the tools of electrochemical analysis (steady-state and dynamic voltammetry, chronoamperometry, scanning electrochemical microscopy, spectroelec-trochemistry, complex impedance analysis) are used to test electrochemical cell. These tools allow the kinetic and mechanistic studies not readily available in nanoelectrochemistry. The research concentrated on improving the metallic catalyst, and also optimizing the interfacial contact and utilization. 

The quartz crystal nanobalance (QCN) can be combined with practically any electrochemical methods, such as cyclic voltammetry, chronoamperometry, chronocoulometry, potentiostatic, galvanostatic, rotating disc electrode [11], or potentiometric measurements. The EQCN can be further combined with other techniques, e.g., with UV-Vis spectroscopy [12], probe beam deflection (PBD) [13], radiotracer [14], atomic force microscopy (AEM) [15], and scanning electrochemical microscopy (SECM) [16]. The concept and the instrumentation of... 

Lovelock KRJ, Cowling FN, Taylor AW, Licence P, Walsh DA (2010) Effect of viscosity on steady-state voltammetry and scanning electrochemical microscopy in room temperature ionic liquids. J Phys Chem B 114 4442-4450... 

Cyclic voltammetry is probably the electrochemical technique that is simulated most often, aiming at the analysis of electrode processes with respect to mechanism, kinetics, and thermodynamics of the reaction steps as well as transport properties of the molecules involved. The simulation of processes at (ultra)microelectrodes is also popular and highly important for the analysis of scanning electrochemical microscopy experiments [10]. 

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