Cyclic voltammogram, modified

Flavin adenine dinucleotide (FAD) has been electropolymerized using cyclic voltammetry. Cyclic voltammograms of poly (FAD) modified electrode were demonstrated dramatic anodic current increasing when the electrolyte solution contained NADH compare with the absence of pyridine nucleotide. 

If the film is nonconductive, the ion must diffuse to the electrode surface before it can be oxidized or reduced, or electrons must diffuse (hop) through the film by self-exchange, as in regular ionomer-modified electrodes.9 Cyclic voltammograms have the characteristic shape for diffusion control, and peak currents are proportional to the square root of the scan speed, as seen for species in solution. This is illustrated in Fig. 21 (A) for [Fe(CN)6]3 /4 in polypyrrole with a pyridinium substituent at the 1-position.243 This N-substituted polypyrrole does not become conductive until potentials significantly above the formal potential of the [Fe(CN)6]3"/4 couple. In contrast, a similar polymer with a pyridinium substituent at the 3-position is conductive at this potential. The polymer can therefore mediate electron transport to and from the immobilized ions, and their voltammetry becomes characteristic of thin-layer electrochemistry [Fig. 21(B)], with sharp symmetrical peaks that increase linearly with increasing scan speed. 

For the in situ characterization of modified electrodes, the method of choice is electrochemical analysis by cyclic voltammetry, ac voltammetry, chronoamperometry or chronocoulometry, or rotating disk voltametry. Cyclic voltammograms are easy to interpret from a qualitative point of view (Fig, 1). The other methods are less direct but they can yield quantitative data more readily. 

Fig. 17. Cyclic voltammogram of the water-soluble Rieske fragment from the bci complex of Paracoccus denitrificans (ISFpd) at the nitric acid modified glassy carbon electrode. Protein concentration, 1 mg/ml in 50 mM NaCl, 10 mM MOPS, 5 mM EPPS, pH 7.3 T, 25°C scan rate, 10 mV/s. The cathodic (reducing branch, 7 < 0) and anodic (oxidizing branch, 7 > 0) peak potentisds Emd the resulting midpoint potential are indicated. SHE, standEU d hydrogen electrode.

Figure 17.12 Direct electrocatal3ftic oxidation of D-fnictose at a glassy carbon electrode painted with a paste of Ketjen black particles modified with D-fructose dehydrogenase from a Gluconobacter species. The enzyme incorporates an additional heme center allowing direct electron transfer from the electrode to the flavin active site. Cyclic voltammograms were recorded at a scan rate of 20 mV s and at 25 + 2 °C and pH 5.0. Reproduced by permission of the PCCP Owner Societies, from Kamitaka et al., 2007.

Figure 17.14 Cyclic voltammograms recorded at 1 V s at a PGE RDE rotating at 2500 rev min ) modified by adsorption of a submonolayer film of [NiEe]-hydrogenase from the purple photosynthetic sulfur bacterium Allochromatium vinosum in buffered aqueous solution at pH 7.0 under an atmosphere of H2 (1 bar). Reprinted with permission from Leger et al., 2002. Copyright (2002) American Chemical Society.

Cyclic voltammograms of the [Fe(CN)6] /Fe[(CN)g] redox couple with the bare and the DNA-modified electrodes are shown in Fig. 5 [14a]. The peak currents due to the reversible electrode reaction of the redox system on the bare Au electrode were significantly suppressed by the treatment with DNA. In contrast, the treatment with unmodified, native DNA made no suppression, and that with HEDS caused only a slight one, as seen in Fig. 

FIG. 5 Cyclic voltammograms of [Fe(CN)6] redox couple on bare (solid line), DNA-modified (heavy line), and HEDS-modified Au electrodes (dotted line). Electrol5de solution, aqueous each 5 mM of K4[Fe(CN)g] and K3[Fe(CN)g] containing 10 mM KCl scan rate 25 mV s temperature, 25°C electrode area, 0.02 cm (geometrical). 

Fig. 5.31 Cyclic voltammogram of a chemically modified electrode with a monolayer of a reversible mediator. The shaded area corresponds to the charge Q...

Figure 1. Cyclic voltammogram on a tin oxide electrode modified with a thin film of poly-1. A sweep rate of 50mV/s was emp 1 oved in CH3CN containing 0.1 M TBAPFS. E vs. Ag+(0.1 M AgN03 in DMSO)/Ag.

Re(bpy)(CO)3Cl-modified electrodes has not yet been explained. However, from the cyclic voltammograms of fac-Re(bpy)(CO)3Cl (Fig. 14) and from the intermediate complexes formed by electrolysis in acetonitrile in the presence and absence of C02, two different electrocatalytic pathways (Fig. 15) were suggested144 initial one-electron reduction of the catalyst at ca. -1.5 V versus SCE followed by the reduction of C02 to give CO and C03, and initial two-electron reduction of the catalyst at ca. -1.8 V to give CO with no C03. The electrochemistry of [Re(CO)3(dmbpy)Cl] (dmbpy = 4,4 -dimethyl-2,2 -bipyridine) was investigated145 to obtain mechanistic information on C02 reduction, and the catalytic reac-... 

Figure 3.89 Cyclic voltammograms of 500 pm cytochrome c at a gold electrode modified by (a) 2-mercaptopyridine, (b> 2-mercaptosuccinic acid, 4,4 -dithiobis(butanoic acid), (d) 4-mercaploaniline. pH 7.0 phosphate buffer +0.1 M NaC104. Scan rale 50mVs . From Allen...

E0 was estimated as ( pa+Epc)/2 in the cyclic voltammograms obtained with the SAM-modified Au electrodes in phosphate buffer at 100mVs-1. and Ep° are anodic and cathodic peak potentials of the Cu, Zn-SOD, respectively. (Reprinted from Y. 

A cyclic voltammogram of a Prussian blue-modified electrode is shown in Fig. 13.2. In between the observed two sets of peaks the oxidation state, which is correspondent to the Prussian blue itself, occurs. Its reduction is accompanied with loss of... 

FIGURE 13.2 Typical cyclic voltammogram of Prussian blue-modified smooth (mirrored glassy carbon) electrode 0.1 M KC1, 40mV s 1. 

The cyclic voltammograms of the GOx/CNT-modified GC electrodes in phosphate buffer solution (pH 7.4) show two pairs of redox peak currents. The first pair of peaks (Ei/2 = 0.09 V vs Ag AgCl) is attributed to the carboxylic acid groups in CNTs, while... 

Figure 6. Cyclic voltammograms of PS I/PBV LB film modified electrode.

Fig. 14 Cyclic voltammograms of ferrocene-modified glucose oxidase with (—) and without (—) glucose...

Within the promoter there can be subtle structural differences that influence the polar interaction with the protein. For example, Figure 5 illustrates the cyclic voltammograms of cytochrome c obtained at a gold electrode modified with isomers of pyridine-carboxylaldehyde-thiosemi-carbazone (PATS). 

Figure 5 Cyclic voltammograms of cytochrome c recorded at gold electrodes modified with different isomers of PATS...

Figure 10 Cyclic voltammograms at a modified gold electrode (see text) of (a) cytochrome c (b) cytochrome f. Aqueous solution buffered at pH 7.3...

Cyclic voltammograms recorded in an aqueous solution of cytochrome c (pH 7.1) at gold electrodes modified by (a) 3-hydroxo-l-propanthiol (b) 11-hydroxo-l-undecanthiol. Scan rate 0.5 V s . T = 0°C... 

Figure 2.11 Cyclic voltammograms of (PAH-Os)4(PVS)4PAH-Os multilayer modified Au electrode self-assembled from PVS and PAH-Os solutions of pH 8.3 and measured in pH 7.3 solutions of different KNO3 concentration 8, 40, 137, 481, 932 and 1500 mM. Sweep rate 0.025 mVs Taken from Ref [107].

Figure 3.19 Cyclic voltammogram obtained with an arc-CNT-modified electrode in the presence of 5 mM ascorbic acid, (a) before and (b) after electrochemical activation at 1.5 V for 3 min in PBS solution, scan rate lOOmV/s. Adapted with permission from Ref [133]. Copyright, 2005, Elesevier.

Figure 5.16 Cyclic voltammograms for the Cu deposition on alkane thiol-modified (CH3 (CH2)m-i SH, MC ) Au(l 1 1) electrodes in 0.1 M H2SO4/I mM CUSO4. Scan rate lOmV/s. Inset shows CV for a bare Au(l 1 1) electrode for comparison. Reproduced with permission from Ref [183].

The isocyanide monolayer was formed by immersing the Cr slide in a 1 mM isocyanide solution under argon for 30 min. The redox wave, which is observed in cyclic voltammograms of the modified Cr electrode, proves that the 4-ferrocenyl-phenyl isocyanide is adsorbed on the metal surface. When a Cr electrode is exposed for 2 h to a solution of ferrocene, no redox wave was observed in the CV, which demonstrates that the isocyanide group is necessary for adsorption. No spectroscopic studies were performed on the adsorbed isocyanide. 

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