ER voltammogram

The spectrum of an ER signal, i.e. the plot of (AR/R)er as a function of k, is called the electroreflectance (ER) spectrum. Electroreflectance measurement can also be carried out during linear potential scan or potential step of Ejc- Under linear potential scan, one obtains the voltammogram of the ER signal, the so-called ER voltammogram. 

Fig. 2.2S ER voltammogram of cytochrome C3 adsorbed on an Au(111) electrode in 10 mM phosphate buffer solution, pH 7.0. Solid lines experimental curves (AEac=84.9 mV,...

The high sensitivity of the ER method benefits bioelectrochemists in the detection of the redox reaction of the electron transfer proteins. Even for an adsorption monolayer of proteins, the superficial density of the electroactive center is much smaller than that of small molecules, especially when the molecular weight of the protein is several kilo-Daltons. The redox reaction of adsorbed protein buried in the double-layer charging current in the voltammogram can be detected by the ER method. Ikeda and coworkers succeeded in the clear observation of the ER spectrum and ER voltammogram of a heme c in an adsorbed protein (alcohol dehydrogenase) of ca. 140 kD containing hemes and PQQ, while direct redox reaction could not be detected by cyclic voltammetry [90]. 

When the electrode potential is scanned at the maximum of the ER spectrum (X - 420 nm), an ER voltammogram is obtained with the peak at its formal potential. The ET rates of the adsorbed species can be calculated from the modulation frequency dependence of the peak heights (real and imaginary parts) [28]. 

SERRS spectroscopic and ER voltammetric techniques were used to investigate the effect of surface modifiers, 11-mercaptoundecanoic acid (11-MUDA) and 4,4 -bipy, on the structure and redox properties of cyt. C3 from D. desulfuricans, Norway strain, at a silver electrode [47]. The ER voltammograms of cyt. C3 immobilized on... 

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