Cyclic voltammetry supporting electrolyte

Figure 16.9 Comparison of cyclic voltammetry in a CO-saturated electrolyte (0.5 M HCIO4) of Au supported on carbon (solid curves) and titania (dashed curves) for four different particle sizes (indicated). The measurements were made at a temperature of 298K and a scan rate of 50mV s ...

The facilitated ion transfers of some alkaline earth metals have been also studied in the DCE systems by the cyclic voltammetry. These systems perhaps have not been studied by any solvent extraction methods yet. Typical voltammograms in the N15C5 diffusion-control systems are shown in Fig. 6. The aqueous supporting electrolyte was MgCl2 instead of MgS04 in these measurements because BaS04 precipitated. 

The reversibility of the carrier was tested by cyclic voltammetry. The scan of the solvent and supporting electrolyte is shown in Fig. 13, with and without dissolved oxygen. The oxygen reduction occurs at about — 0.43 V. (vs. SCE). The scan with the complex added, but the solution free of dissolved oxygen is shown as Fig. 14. The carrier is seen to be reduced at about 0.04 V, well within the window of the solvent and electrolyte, and well before reduction of molecular oxygen. 

The electrochemical behavior of niclosamide was described on the basis of d.c. polarography, cyclic voltammetry, a.c. polarography, and differential pulse polar-ography, in the supported electrolytes of pH ranging from 2.0 to 12.0 [32], A tentative mechanism for the reduction of niclosamide is proposed that involves the transfer of 4 e . Parameters such as diffusion coefficients and heterogeneous forward rate constant values were evaluated. 

Chemical reactivity of unfunctionalized organosilicon compounds, the tetraalkylsilanes, are generally very low. There has been virtually no method for the selective transformation of unfunctionalized tetraalkylsilanes into other compounds under mild conditions. The electrochemical reactivity of tetraalkylsilanes is also very low. Kochi et al. have reported the oxidation potentials of tetraalkyl group-14-metal compounds determined by cyclic voltammetry [2]. The oxidation potential (Ep) increases in the order of Pb < Sn < Ge < Si as shown in Table 1. The order of the oxidation potential is the same as that of the ionization potentials and the steric effect of the alkyl group is very small. Therefore, the electron transfer is suggested as proceeding by an outer-sphere process. However, it seems to be difficult to oxidize tetraalkylsilanes electro-chemically in a practical sense because the oxidation potentials are outside the electrochemical windows of the usual supporting electrolyte/solvent systems (>2.5 V). 

Obtained by both cyclic (100 mV s-1) and square-wave (10 Hz, Osteryoung-type) voltammetry in acetonitrile solution containing 0.1 mol dm-3 BuJNBF4 as supporting electrolyte. Solutions were 1 x 10-3 mol dm-3 in compound with reference to an Ag/Ag+ electrode (330 10 mV vs SCE) at 21 1°G b Anodic shift of the reduction waves of [57] in the presence of 1.0 equiv of the respective cationic species added as their perchlorate or hexafluorophosphate salts. "Anodic shift in the presence of 2.0 equiv of the respective cations. The second reduction wave of [57] became obscure or disappeared in the presence of more than 1 equiv of the respective cations. 

Cyclic voltammetry was conducted using a Powerlab ADI Potentiostat interfaced to a computer. A typical three electrode system was used for the analysis Ag/AgCl electrode (2.0 mm) as reference electrode Pt disc (2.0 mm) as working electrode and Pt rod (2.0 mm) as auxiliary electrode. The supporting electrolyte used was a TBAHP/acetonitrile electrolyte-solvent system. The instrument was preset using a Metrohm 693 VA Processor. Potential sweep rate was 200 mV/s using a scan range of-1,800 to 1,800 mV. 

For further contributions on the dia-stereoselectivity in electropinacolizations, see Ref. [286-295]. Reduction in DMF at a Fig cathode can lead to improved yield and selectivity upon addition of catalytic amounts of tetraalkylammonium salts to the electrolyte. On the basis of preparative scale electrolyses and cyclic voltammetry for that behavior, a mechanism is proposed that involves an initial reduction of the tetraalkylammonium cation with the participation of the electrode material to form a catalyst that favors le reduction routes [296, 297]. Stoichiometric amounts of ytterbium(II), generated by reduction of Yb(III), support the stereospecific coupling of 1,3-dibenzoylpropane to cis-cyclopentane-l,2-diol. However, Yb(III) remains bounded to the pinacol and cannot be released to act as a catalyst. This leads to a loss of stereoselectivity in the course of the reaction [298]. Also, with the addition of a Ce( IV)-complex the stereochemical course of the reduction can be altered [299]. In a weakly acidic solution, the meso/rac ratio in the EHD (electrohy-drodimerization) of acetophenone could be influenced by ultrasonication [300]. Besides phenyl ketone compounds, examples with other aromatic groups have also been published [294, 295, 301, 302]. 

The ferrocenyl dendrimers were electrodeposited in their oxidized forms onto the electrode surfaces (platinum, glassy-caibon, and gold) either by controlled potential electrolysis or by repeated cycling between the appropriate anodic and cathodic potential limits therefore the amount of electroactive material electrode-posited can be controlled with the electrolysis time or the number of scans. The electrochemical behavior of films of the polyfeirocenyl dendrimers was studied by cyclic voltammetry in fresh CH2CI2 and CHjCN solutions containing only supporting electrolyte. 

Fig. 1 Cyclic voltammetry pattern at a glassy carbon electrode (GC Tokai, Japan) with 10 M a-K6P2Wig062 in 1 M HCl supporting electrolyte. Sweep rate 100 mV s electrode surface area ...

The step 1 product and 2,2, 5,2"-terthiophene were reacted to form the copolymer using cyclic voltammetry and electro-copolymerizalion. Cyclic voltammetry in CH2CI2 containing 0.1 M tetrabutylammonium perchlorate supporting electrolyte indicated that the co-monomer oxidation began at approximately 0.70 V vs. Ag/Ag+. 

Figure 14.8 Cyclic voltammetry curves recorded using a Pt working electrode at a 100 mV/s sweep rate (CH3CN/CH2CI2 (4 1), supporting electrolyte NBu4BF4, 0.1 M, Ag wire pseudoreference). (a) Compound 4(4) + (b) chemically prepared 4(5)2 +. Curve (ii) refers to a second potential sweep following immediatly the first one (i).

For the electrochemical measurements reported herein, all cyclic voltammetry measurements are performed in CH2C12 with 0.1 M tetra-n-butylammonium tetrafluoroborate (Bu4NBF4) as supporting electrolyte, while measurements in CH3CN use 0.1 M tetra-ethylammonium perchlorate. Cyclic voltammetry measurements are performed in a three-electrode, one-compartment cell equipped with a Pt working electrode, a Pt auxiliary electrode, and a saturated sodium chloride calomel (SSCE) reference electrode. E1 2 = (Ep.a + Ep.c)/2 AEP = Ep,e - Ep,a-Ei/2 and AEP values are measured at 100 mV/sec. Ferrocene is used as a reference in the measurement of the electrochemical potentials. 

Methyl indole (52) does not show any reduction peak in cyclic voltammetry in diglyme-H20 solutions with (C4H9)4NBF4 as the supporting electrolyte. 

Electrochemical properties were examined to gain more quantitative insight into the redox properties of this system. Cyclic voltammetry on bis(dithiazole) 23 in acetonitrile (with Pt electrodes and 0.1 M -Bu4NPF6 as supporting electrolyte) reveals a reversible oxidation wave with i/2(°x) = 0.93 V and a second, irreversible oxidation process... 

Polypyrrole thin film doped with glucose oxidase (PPy-GOD) has been prepared on a glassy carbon electrode by the electrochemical polymerization of the pyrrole monomer in the solution of glucose oxidase enzyme in the absence of other supporting electrolytes. The cyclic voltammetry of the PPy-GOD film electrode shows electrochemical activity which is mainly due to the redox reaction of the PPy in the film. Both in situ Raman and in situ UV-visible spectroscopic results also show the formation of the PPy film, which can be oxidized and reduced by the application of the redox potential. A good catalytic response to the glucose and an electrochemical selectivity to some hydrophilic pharmaceutical drugs are seen at the PPy-GOD film electrode. 

The electrochemical properties of compounds (90)—(97) were investigated in acetonitrile using cyclic voltammetry with [Bu"4N]BF4 as the supporting electrolyte. Each compound exhibited a reversible redox... 

Figure 4.11 Effect of SAM formation on the cyclic voltammetry of ferrocenylmethyltrimethylam-monium on a polycrystalline gold electrode the supporting electrolyte is 0.5 M H2SO4, with a scan rate of 0.1 V s-1. Curve (a) is the reversible cyclic voltammogram obtained on bare gold, while curves (b)-(d) are obtained on the same electrode with different monolayers (for details see text). The symbols represent theoretical fits to a microarray electrode model. Reprinted with permission from H.O. Finklea, D.A. Snider, J. Fedyk, E. Sabatani, Y. Gafni and I. Rubinstein, Langmuir, 9,3660 (1993). Copyright (1993) American Chemical Society...

Figure 5.22 Cyclic voltammetry data obtained for a 5 pm radius platinum microelectrode modified with a [Ru(bpy)2Qbpy]2+ monolayer following laser excitation at 355 nm, with a scan rate of 3 x 105 V s 1. The surface coverage is 1.1 x 10-10 mol cm 2, the supporting electrolyte is 0.1 M TBABF4 in acetonitrile, and the initial potential is —1.2 V. Reprinted with permission from R. J. Forster and T. E. Keyes, /. Phys. Chem., B, 102,10004 (1998). Copyright (1998) American Chemical Society...

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