Electrochemical spectroscopy

Metal and semiconductor materials (borides, carbides, nitrides, and silicides). Tin oxide-coated glass has been used as an electrode material in electrochemical spectroscopy. By doping of the tin oxide with antimony, an n-type semiconductor is formed. The surface is chemically inert and is transparent in the visible region of the spectrum. However, it is more useful for its optical transparency than as an electrode material. 

The intensive electrochemical studies of polycyclic systems, especially cyclic volta-metry (CV) are now at a stage which justifies naming cyclic voltametry an electrochemical spectroscopy as was suggested by Heinze 65). Early electrochemical studies referred only to the thermodynamic parameters while CV studies provide direct insight into the kinetics of electrode reactions. These include both heterogeneous and homogeneous electron-transfer steps, as well as chemical reactions which are coupled with the electrochemical process. The kinetic analysis enables the determination of reactive intermediates in the same sense as spectroscopic methods do. As already mentioned, electron transfer processes occur in both the electrochemical and metal reduction reactions. 

The fact that metal ions in complexes often have the ability to undergo oxidation and/or reduction, with the resultant complexes having distinctly different properties as a result of the change in the metal d-electron set, means that techniques able to probe these processes have developed (Table 7.4). In coordination chemistry, the technique of cyclic voltammetry (sometimes called electrochemical spectroscopy because of its capacity to rapidly probe behaviour in different oxidation states in simple solution experiments) is now commonly employed. Thermodynamic properties, such as reaction enthalpy and complex stability... 

Ruan Q et al (2009) Investigation of layer-by-layer assembled heparin and chitosan multilayer films via electrochemical spectroscopy. J Colloid Interface Sci 333 725-733 Fu J et al (2006) Construction of antibacterial multilayer films containing nanosilver via layer-by-layer assembly of heparin and chitosan-silver ions complex. J Biomed Mater Res A 79A 665-674... 

In order to understand the aging or failure mechanisms of the IL electrolyte-based EDLCs, the electrochanical decomposition of the ILs in EDLCs beyond the ESPW has been investigated [35,102,103]. Using in situ infrared and electrochemical spectroscopy methods, Romaim et al. [102] reported that for [EMIM][BF4] IL electrolyte, imidazolium cation dimerized and led to the formation of l,5-diethyl-4,8-dimethyl-l,4,5,8-tetraazaf-ulvalene at the electrode potential below -2 V (vs. Ag/AgCl wire in the same IL), while the formation of BF3 complexes with BF4 anion and fluorination of the cations occurred... 

Heath, G. A. Spectroelectrochemistry and Electrochemical Spectroscopy. In Molecular Electrochemistry of Inorganic, Bioinorganic and Organometallic Compounds Pombeiro, A. J. L. McCleverty, J. A., Eds. NATO ASI Series, Series C Kluwer Academic, Dordrecht 1993, pp 533-547. 

Electrochemical spectroscopy is the larger ambition to me it means is the elucidation of electronic structure by marshalling all the electrochemical and spectro-electrochemical evidence. I have borrowed this graphic term from Heinze who focussed on the power of voltammetry and invested with my own meaning. He is free to make a disclaimer. 

More importantly, in the context of orbital mapping or "electrochemical spectroscopy" the same redox-active orbital (dxy) figures in the primary CT process and in interconfigurational d-d excitations and in the d5/d6 reduction.. Do we find a faithful and illuminating correlation We have tested this on an archetypal system OSX4L2. This system starkly illustrates how the incremental electronic response to progressive substitution can be linear or non-linear depending on the nature of L (and X). 

Linear potential sweep and cyclic voltammetry have been used extensively to examine the redox behavior of surface-deposited electroactive polymer films qualitatively. In this respect the technique can be classified as a form of electrochemical spectroscopy, since it delineates regons of redox activity, and provides an initial survey of overall electrochemical behavior of an electroactive polymer film as a function... 

Cyclic Voltammetry-Electrochemical Spectroscopy by J. Heinze, Angew. Chem. Int. Ed. (1984) 23, 831. 

Heinze, J. Cyclic voltammetry - Electrochemical spectroscopy. Angew. Chem. 96 (1984) 823. 

In potential-sweep techniques, the current flowing at the WE/solution interface is monitored as a function of the potential applied to it. We consider three such volta-mmetric techniques linear sweep voltammetry (LSV), cyclic voltammetry (CV), and hydrodynamic voltammetry (Fig. 20.4). The voltammogram obtained in each case may be regarded as the electrochemical equivalent of a spectrum obtained in a spectrophotometric technique. Indeed, the term electrochemical spectroscopy has been applied to CV [56], and it is worth noting that the independent variable in both cases is related to energy—wavelength in the case of spectroscopy and potential in the case of CV. The potential is swept linearly at I V/s so that the potential at any time is (/) = E vt. 

In most SECM experiments, the tip is held at a constant potential in an amperometric mode or scanned in the cyclic voltammetry (CV) mode. The substrate can also be subjected to various potential treatments. Studies involving transients or time-dependent signals are especially useful in obtaining information about adsorbed intermediates or products, as discussed in Chapter 16. Another time-dependent technique involves an AC signal applied to the tip, a form of electrochemical spectroscopy impedance (EIS). Examples of this approach have been discussed in Chapter 14 as applied to studies of the mechanism of corrosion processes. For example, in the... 

F. Y. Olivia, L. B. Avalle, V. A. Macagno, C. P. De Paulli, Study of human serum albumin-TiOl nanocrystalline electrodes interaction by impedance electrochemical spectroscopy, Bio-phys. Chem., 2001,91,2, pp. 141-155. 

Iwasita T and Mart F C 1997 In situ infrared spectroscopy at electrochemical interfaces Prog. Surf. Sc/. 55 271... 

In addition to the many applications of SERS, Raman spectroscopy is, in general, a usefiil analytical tool having many applications in surface science. One interesting example is that of carbon surfaces which do not support SERS. Raman spectroscopy of carbon surfaces provides insight into two important aspects. First, Raman spectral features correlate with the electrochemical reactivity of carbon surfaces this allows one to study surface oxidation [155]. Second, Raman spectroscopy can probe species at carbon surfaces which may account for the highly variable behaviour of carbon materials [155]. Another application to surfaces is the use... 

Amongst other spectroscopic teclmiques which have successfiilly been employed in situ in electrochemical investigations are ESR, which is used to investigate electrochemical processes involving paramagnetic molecules, Raman spectroscopy and ellipsometry. 

Other techniques to detennine the corrosion rate use instead of DC biasing, an AC approach (electrochemical impedance spectroscopy). From the impedance spectra, the polarization resistance (R ) of the system can be detennined. The polarization resistance is indirectly proportional to j. An advantage of an AC method is given by the fact that a small AC amplitude applied to a sample at the corrosion potential essentially does not remove the system from equilibrium. 

Quantitative determination is also possible by ultraviolet spectroscopy with the intense absorption at 320 nm (94). They may also be characterized electrochemically with a mercury electrode (95),... 

In voltammetry a time-dependent potential is applied to an electrochemical cell, and the current flowing through the cell is measured as a function of that potential. A plot of current as a function of applied potential is called a voltammogram and is the electrochemical equivalent of a spectrum in spectroscopy, providing quantitative and qualitative information about the species involved in the oxidation or reduction reaction.The earliest voltammetric technique to be introduced was polarography, which was developed by Jaroslav Heyrovsky... 

Earlier we described a voltammogram as the electrochemical equivalent of a spectrum in spectroscopy. In this section we consider how quantitative and qualitative information may be extracted from a voltammogram. Quantitative information is obtained by relating current to the concentration of analyte in the bulk solution. Qualitative information is obtained from the voltammogram by extracting the standard-state potential for the redox reaction. For simplicity we only consider voltammograms similar to that shown in Figure 11.33a. 

Detector Detection in FIA may be accomplished using many of the electrochemical and optical detectors used in ITPLC. These detectors were discussed in Chapter 12 and are not considered further in this section. In addition, FIA detectors also have been designed around the use of ion-selective electrodes and atomic absorption spectroscopy. 

The mechanisms of lead corrosion in sulfuric acid have been studied and good reviews of the Hterature are available (27—30). The main techniques used in lead corrosion studies have been electrochemical measurements, x-ray diffraction, and electron microscopy. More recendy, laser Raman spectroscopy and photoelectrochemistry have been used to gain new insight into the corrosion process (30,31). 

Benzofurazan, 7-chloro-4-nitro-, 6, 394 as fluorigenic agents, 6, 410, 426 Benzofurazan, 4-chloro-7-sulfo-ammonium salt properties, 6, 426 Benzofurazan, 4-nitro-synthesis, 6, 408 Benzofurazans, 6, 393-426 Beckmann fragmentation, 6, 412 biological activity, 6, 425 bond angles, 6, 396 bond lengths, 6, 396 diazo coupling, 6, 409 dipole moments, 6, 400 electrochemical reduction, 5, 73 electrophilic reactions, 6, 409-410 ESR spectroscopy, 6, 400... 

Electrochemical Impedance Spectroscopy (EIS) and AC Impedance Many direct-current test techniques assess the overall corrosion process occurring at a metal surface, but treat the metal/ solution interface as if it were a pure resistor. Problems of accuracy and reproducibility frequently encountered in the application of direct-current methods have led to increasing use of electrochemical impedance spectroscopy (EIS). 

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