Cyclic voltammetry measurement

Cyclic Voltammetry measurement of the current or current density as a function of the electrode potential by application of one or more potential sweep cycles. 

Hyun et al. [345] prepared PbS Q-dots in a suspension and tethered them to Ti02 nanoparticles with a bifunctional thiol-carboxyl linker molecule. Strong size dependence due to quantum confinement was inferred from cyclic voltammetry measurements, for the electron affinity and ionization potential of the attached Q-dots. On the basis of the measured energy levels, the authors claimed that pho-toexcited electrons should transfer efficiently from PbS into T1O2 only for dot diameters below 4.3 nm. Continuous-wave fluorescence spectra and fluorescence transients of the PbS/Ti02 assembly were consistent with electron transfer from small Q-dots. The measured charge transfer time was surprisingly slow ( 100 ns). Implications of this fact for future photovoltaics were discussed, while initial results from as-fabricated sensitized solar cells were presented. 

Electroactive 3-(N-phenylpyrazolyl)fullereno[l,2-r/]isoxazolines have been synthesized by using 1,3-dipolar cycloaddition of pyrazole nitrile oxides, generated in situ, to Cgo at elevated temperature or microwave irradiation. The cyclic voltammetry measurements show a strong donor pyrazole ring, and a better acceptor ability of the fullerene moiety than the parent C60 (538). Treating fullerene Cgo with mesitonitrile oxide in toluene gives fullerene-nitrile oxide adduct, which is supposed to be useful for electrical and optical components (539). 

Surprisingly, the partial reduction of quinone 137 is best achieved by refluxing in acetic or propionic acids (yield 67%). Thereby the acids suffer oxidative decarboxylation (82CL701 85BCJ515). Two further unexpected routes are based on the redox reaction with cycloheptatriene (85BCJ2072) and electrolysis under the conditions of the cyclic voltammetry measurements (87BCJ2497), respectively. 

Scheme 3 accounts for the various products formed, and it is consistent with known transformations in organometallic chemistry. In the first step, CO2 is reduced in a proton-coupled two-electron process to form adsorbed CO. That CO is an intermediate in the reduction of CO2 to hydrocarbons is supported by the following observations. (1) Reduction of CO at copper electrodes under the same conditions gives a similar distribution of hydrocarbon products. Reduction of formate, on the other hand, gave no hydrocarbon products [98, 102]. (2) CO on the electrode surface could be detected by cyclic voltammetry measurements. Fourier transform... 

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. 

On heating K4[Mo2C1s] with ethylenediamine, and then adding hydrochloric acid to an aqueous solution of the crude product, orange crystals of [Mo2(en)4]Cl4 are obtained.17 These give an absorbance (5— 6 ) band at 475 nm. It is unlikely that the ethylenediamine ligand is bridging. Cyclic voltammetry measurements have shown that the complex exhibits an irreversible oxidation at +0.78 V (SCE). 

The redox properties of dinuclear copper(II) complexes have received extensive attention using cyclic voltammetry measurements, and it was recognized in the early literature that the two copper(II) ions could be reduced to copper(I) at the same potential or at different potentials (Section 53.3.7).30,934,1021,1022 In either case the reduction requires a two electron process and if the E° values are well separated may result in the observation, under favourable circumstances, of a two-peaked cyclic voltammogram (Figure 61b), as in... 

Equally, the trends found in cyclic voltammetry measurements are perfectly reproduced by this computational study. For instance, the HOMO/LUMO energies are in perfect agreement with the oxidation and reduction potentials obtained from electrochemistry. It is noteworthy that electrochemical measurements suggest that... 

Figure 3.10 Current-potential curves obtained from cyclic voltammetry measurements for the reduction and oxidation of an adsorbed interfacial supramolecular assembly under finite diffusion conditions...

In multiscan cyclic voltammetry measurements, e.g., of a redox film-coated electrode, the isopotential point is the potential of the same current value for voltam-mograms of different cycles. That is, by analogy to, e.g., the isosbestic point in absorption spectroscopy of two species remaining in equilibrium, this is the potential at which voltammograms of two redox species being in equilibrium in the film cross each other. A pair of such redox species can have several isopotential points in their multicyclic voltammograms. 

Peak potentials from cyclic voltammetry measurements at mercury-plated platinum, in MeCN-TEAB at 10 V s sweep rate. Values in parentheses relate to peak potentials obtained when the potential was cycled in the positive direction after observation of the reduction. 

In cyclic voltammetry measurements of DMF solutions of nitroso-, azoxy-, and azobenzene using the hanging mercury drop electrode, it was found that besides the usual peaks of redox processes an additional, new system of peaks was observed. Its properties were nearly identical for all three substrates. The most probable interpretation seems to be to attribute this additional system of peaks to a reaction between adsorbed azobenzene dianion and mercury at graphite such additional peaks were not observed [173] ... 

Cyclic-voltammetry measurements of quasireversible systems yield more easily to interpretation. Both the cathodic and anodic peak potentials shift as a function of scan rate, resulting in an increasing AE as v increases. This dependence of AEp on electron-transfer rate is used to measure the k value of the system, but AE also increases monotonically with v from the effects of uncompensated resistance, and the two effects are difficult to separate. The absence of appreciable resistance effects must be insured when making these measurements. Many reported rate constants are erroneous because of improper attention to this problem ... 

Cyclic voltammetry measurements revealed that in the ease of DCNDBQT, different CV eurves were obtained depending on the solvent used. In dichlo-romethane the CV exhibited two reversible oxidation and one irreversible reduction processes (not shown). The irreversibility of the reduction process can be explained by the conditions of recording the electrochemical measurements (scan rate, electrolyte, electrode material), which play an important role on the reversibility of the processes [24]. 

Kovacic using cyclic voltammetry measurement at either Pt or dropping mercury working electrodes52. Unfortunately, because of the low solubility of 43 in 0.1 M KH2PO4/O.I M NaOH solution (pH 7.0), no reduction wave was observed. 

Cyclic voltammetry measurements revealed that the 1,3-isomer [Rh (ri -CsPhs)) 1,3-cod)] (Ei/2 = -0.01 V vs. Fc/Fc ) is easier to oxidize than the 1,5-isomer [Rh ri -CsPhs)) 1,5-cod)] ( 1/2 = 0.09 V vs. Fc/Fc+), presumably because the Rh(l) complex of 1,3-isomer is less stable than the 1,5-isomer and the oxidized Rh(ll) complex profits from an additional agostic interaction between Rh(II) and an allylic hydrogen atom (a geometry not accesible for the 1,5-isomer). 

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