Voltabsorptometry

CP = current-potential curves CV = cyclic voltammetry EXI VA = derivative cyclic voltabsorptometry IP = impedance method. See also list of symbols. 

Bowden, E. F., Hawkridge, F. M., Chlebowski, J. F., Bancroft, E. E., Thorpe, C., Blount, H. N., Cyclic Voltammetry and Derivative Cyclic Voltabsorptometry of Purified Horse Heart Cytochrome C at Tin-Doped Indium Oxide Optically Transparent Electrodes , J. Am. Chem. Soc. 104 (1982) 7641-7644. 

Park et al. [51] concluded from their spectroelec-trochemical experiments that the nitrene cation must be the intermediate species. They showed from derivative cyclic voltabsorptometry (DCVA) experiments that the 420 ran band, which happens to be located at the same wavelength as that of oxidized benzidine, does not actually originate from the oxidized benzidine. The... 

The anodic peak observed during the electrochemical doping is always followed by a large capacitive current as was the case for PAn and PPy [162,178]. This large residual current observed beyond the anodic peak has been clearly shown to arise from capacitance currents in the case of PAn oxidation by the derivative cyclic voltabsorptometry experiment (see below) [179]. This residual current, however, was also interpreted as a continuous distribution of redox states with different oxidation potentials [180]. The cathodic currents usually have more than one peak, neither of which is as sharp as their anodic counterparts. This was attributed to differences in redox potentials due to the different interactions with charged states as in the case of hydroxide or other anion-doped PPy [172] and differences in structural relaxation and conformational changes [181]. 

Fig. 16. Cyclic voltabsorptometry A-E curves for 2 mg/ml Hb at a MG CME. Scan rate, 1.0 mV/sec monitor wavelength, 405 nm solution, 0.1 M phosphate buffer (pH 7.0) plus 0.2 M KNO3. (A) First cycle, (B) sixth cycle, (C) after 48 hr. ...

Figure 18. (A) Cyclic voltammetry of purified cytochrome c at doped indium oxide optically transparent electrodes. Solution contained 73 /uiM cytochrome c, 0.21 M Tris, 0.24 M cacodylic acid, pH 7.0, 0.20 M ionic strength. Electrode area = 0.71 cm. Potential scan rates in mV/s are (a) 100 (b) 50 (c) 20 (d) 10 (e) 5.0 (f) 2.0. (B) Derivative cyclic voltabsorptometry of purified cytochrome c at a tin-doped indium oxide optically transparent electrode. Same conditions as described above. Circles are calculated derivative cyclic voltabsorptometric responses for 73 /iM cytochrome c, formal potential = 0.260 V, n = 1.0, diffusion coefficient of oxidized and reduced cytochrome c = 1.2 x 10 cm /s, difference molar absorptivity at 416 nm = 57,000 cm" formal heterogeneous electron transfer rate constant = 1.0 x 10 cm/s, and electrochemical transfer coefficient = 0.5. Adapted from Reference (126) with permission.

Derivative cyclic voltabsorptometry (DCVA) is the optical analog of CV. Usually a fixed wavelength is... 

In the case of voltabsorptometry, it is possible to modulate the potential and measure reflectance variations. Indeed, reflectance is related to absorbance by... 

Ding, Z. F., P. F. Brevet, and H. H. Girault, Heterogeneous electron transfer at the polarised water/l,2-dichloroethane interface studied by in situ UV-VIS spectroscopy and differential cyclic voltabsorptometry, Chem Commun, (1997) p. 2059. 

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