Bioelectrochemistry: An Examination of Some Examples

McCreery, Richard L.; Wilson, George S.

doi:10.1080/10408347808542699

Cited by 7 publications

(10 citation statements)

References 137 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Consideration of eq. [6] also explains the large (194 mV, rising to 227 mV at 194 MPa) SE values found for LiCl solutions, since kc' for F~(CN):-/~-in such solutions is only one-tenth that in aqueous KC1 (20).…”

Section: Discussionmentioning

confidence: 91%

“…As with the anomalous behavior of ~e (~h e n ) ,~+ / ' + noted above, it is likely that a medium effect such as ion association is responsible (but in a different manner) for these discrepancies between calculation and experiment for reactions [4] and [5] -certainly, both the electrochemistry (20)(21)(22)(23) and the high-pressure solution chemistry (6) of the highly charged cyanoferrates are well known to be sensitive to counterion effects, while Fe(H20)63+ and ~o ( s e p )~+ can be expected to be more prone to association with anions than is the larger ~e (~h e n ) ,~+ .…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Pressure dependences of the electrode potentials of some iron(III/II) and cobalt(III/II) couples in aqueous solution

Doine¹,

Whitcombe²,

Swaddle³

1992

Can. J. Chem.

View full text Add to dashboard Cite

The dependences of the electrode potentials E of aqueous Fe(H20);+/'+, ~e(~hen),)+/'+, F~(cN)~)-/"-, and ~o ( s e~) ' + / ' + upon pressure P (up to ca. 200 MPa) have been measured at 25.0°C relative to an AgCl/Ag(satd. KCI) electrode by cyclic voltammetry. For ~o ( s e~)~+ / ' + at ionic strength I = 0.28 and 1.00 rnol kg-', (dE/dP), is independent of P as well as I, giving a volume of reaction AV = + 13.7 ? 0.4 cm3 mol-' relative to AgCl/Ag; similarly, for F~( H~o ) ; + /~+ at I = 0.28 rnol kg-' (CF3S03H), AV = +5.0 * 0.3 cm3 mol-'. For F~(cN);-/~-in KC1 media, (dE/dP), is independent of P and I at I = 0.28 and 0.51 rnol kg-', giving AV = -36.1 ? 1.0 cm3 mol-', but shows some slight dependence on P at I = 1.00 rnol kg-' (low-pressure limit AVO = -38 * 1 cm3 mol-'; (dAV/dP), = +0.030 cm3 mol-' MP~-I).For ~e (~h e n )~~+ / ' + , (dE/dP), is markedly pressure and medium dependent, with AVO = +14.2 ? 0.5 and +6.2 ? 0.5 cm3 mol-' in KNO, media at I = 0.25 and 1 . OO rnol kg-', respectively. The peak-to-peak separation of the cyclic voltammograms increases with increasing P for Fe(cN)$-I4-, but decreases slightly for the cationic couples; these trends can be accounted for in terms of the volumes of activation for the corresponding self-exchange reactions.

show abstract

Section: Discussionmentioning

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Pressure dependences of the electrode potentials of some iron(III/II) and cobalt(III/II) couples in aqueous solution

Doine¹,

Whitcombe²,

Swaddle³

1992

Can. J. Chem.

View full text Add to dashboard Cite

show abstract

“…Electrochemical measurements were made on freshly prepared solutions containing 2 mmol L -1 K 3 [Fe(CN) 6 ], using a Pt wire working electrode and a gold counter electrode and excluding light. Contamination of the working electrode surface, probably by deposition of Prussian blue-like films through decomposition of the hexacyanoferrates, led to erratic results in experiments lasting half a day or more, but the contaminants were adequately removed in situ by potential cycling. Cyclic voltammetry gave Δ V AgCl/Ag = −34.2 ± 1.2 cm 3 mol -1 , in satisfactory agreement with earlier work regarded as definitive (Table ). , Electrochemical rate constants reported for this much-studied couple range from <0.01 to 0.24 cm s -1 , being markedly influenced by both the supporting electrolyte and the nature, dimensions, and mode of cleaning of the working electrode. − The k el values of Table , however, are in good agreement with careful measurements , using conventional Pt electrodes at the same or interpolated K + concentrations, and the high-pressure techniques described here were therefore developed by using this conveniently available couple.…”

Section: Resultsmentioning

confidence: 99%

Relationship between Heterogeneous and Homogeneous Kinetics of Electron Transfer between Transition Metal Complexes in Aqueous Solution: Volumes of Activation

and

Swaddle

1997

J. Am. Chem. Soc.

View full text Add to dashboard Cite

Electrochemical rate constants k el and volumes of activation ΔV el ⧧ for self-exchange at an electrode of the aqueous couples Co(phen)3 3+/2+, Co(en)3 3+/2+, Fe(H2O)6 3+/2+, Co(diamsar)3+/2+, Co(diamsarH2)3+/2+, Co(sep)3+/2+, Co(ttcn)2 3+/2+, Fe(phen)3 3+/2+, Mo(CN)8 3-/4-, and Fe(CN)6 3-/4- have been measured by high-pressure AC voltammetry over the range 0.1−200 MPa at 25 °C; the respective values of ΔV el ⧧ are −9.1, −8.3, −5.5, −3.5, −3.8, −3.0, −2.8, −1.6, +7.3, and +11 cm3 mol-1. Although the theory of Marcus (Electrochim. Acta 1968, 13, 1005) suggests that ln k el should be linearly related to 1/2 ln k ex, where k ex is the rate constant of the corresponding homogeneous (bimolecular) self-exchange reaction, ln k el is often sensitive to the nature of the working electrode and the supporting electrolyte and is only weakly correlated with ln k ex, with slope ≈0.1. In contrast, ΔV el ⧧ = (0.50 ± 0.02)ΔV ex ⧧, in precise agreement with an extension of Marcus' theory, regardless of the nature of the electrode and the supporting electrolyte. This result implies that electron transfer in these couples occurs adiabatically on direct ion−ion and ion−electrode contact (i.e., within the outer Helmholtz plane), and also that ΔV el ⧧ values are predictable in the manner described elsewhere (Can. J. Chem. 1996, 74, 631) for ΔV ex ⧧. Conversely, where ΔV ex ⧧ cannot be measured for technical reasons (e.g., where paramagnetism of both reactants precludes NMR measurements of k ex), it can be reliably estimated as 2ΔV el ⧧.

show abstract

“…3) at low C to infinite dilution yields an Id Of 0.94 ~A sec 1/2 mM -1 mg -2/3, which corresponds to a diffusion coefficient, D, of 0.18 • 10 -5 cm 2 sec-L Use of the Matsuda equation (9), which considers shielding effects and best describes the id-t behavior at controlled drop-times (10), gives a D of 0.17 • 10 -5 cm 2 sec-L These values for D may be compared with D for NAD + in water on the basis of the relation TIDMSO • DDMso ~ TIH20 • DH20 [5] which is applicable if solvation effects are small to moderate (or generally similar) and if the added 3.33 • 10 -6 g cm sec -2 and ~H20 X DH20 NAD+ ~ 3.04 X 10 -6 g cm sec -2. The DH20 NAD+ Of 0.34 • 10 -5 cm 2 sec -1 used was determined in 0.4M TEAP and 0.1M pH 9.6 carbonate buffer (2).…”

Section: Methodsmentioning

confidence: 99%

Electrochemical Reduction of Nicotinamide Adenine Dinucleotide in Dimethylsulfoxide: Ion‐Pair, Protonation, and Adsorption Effects

Maliński

Elving

1982

J. Electrochem. Soc.

View full text Add to dashboard Cite

The effects were examined of variations in background electrolyte tetraalkylammonium cation (R4N § and in proton availability upon the electrochemical reduction in DMSO of the coenzyme fl-nicotinamide adenine dinucleotide (NAD*), which has one available proton on the pyrophosphate group, and of its sodium salt [NAD+(Na)] in which the pyrophosphate proton has been replaced by Na(I). The proton reduction in solutions of NAD § HC104, H3PO4, and mixture of NAD+(Na) with HC104 and with H3PO4 was also investigated with reference to various possible equilibria involving Brhnsted acid in DMSO solutions, e.g., the relation of polarographic half-wave potential to pKa.In general, the size of R in R4N § (and its consequent adsorbability at the electrode/solution interface) does not appreciably affect the ease of reduction of the nicotinamide moiety but can exert a marked influence on proton reduction.Various aspects of the electrochemical behavior of the biologically important coenzyme, p-nicotinamide adenine dinucleotide (NAD+ ; Fig 1), have been investigated (1-5). In aqueous solution, NAD + is reduced enzymatically in a one-step process (Eq. [1]) and electrochemically in a two-step process (Eq. [2])There is one reported electrochemical study of NAD + in nonaqueous media (6); the reduction pattern involves an initial one-electron (le) uptake followed by rapid dimerization of the free radical product; no reduction of dimer or free radical occurs within the available potential rangeThe present study involves a detailed examination of the electrochemical reduction of NAD + in DMSO solution with particular attention to the effects of different supporting electrolytes involving tetraalkylammonium ions (R~N + ) and of varying proton availability. The reduction of protonated species was also examined from the viewpoint of Brhnsted acid equilibria in DMSO. ExperimentalChemicals.--Nicotinamide adenine dinucleotide (Chemalog) an,d nicotinamide adenine dinuc~eotide sodium salt (Sigma) (Fig. i) were the best grades available. Reagent-grade tetramethylammonium perchlorate (TMAP), tetraethylammonium perchlorate (TEA.P), tetra-n-butylammonium perchlorate (TBAP), and potassium perchlorate (PP) (G. Frederick Smith) were recrystallized four times from water and then dried in a vacuum at 60 ~ for 48 hr. Other chemicals used were analytical reagent grade or the equivalent. Aqueous 25% tetraethylammonium hydroxide (TEAH) solution was obtained from Eastman; 0.19M HC104 solution in DMSO was prepared from aqueous diluted 1:1 perchloric acid. DMSO (Fisher certified ACS), dried over Linde 5A molecular sieves, was purified by fractional crystallization, using a method identical to that described for purification of pyridine (7); the cooling bath was H20 at 12~176 Apparatus.--A Princeton Applied Research Model170 polarograph was used with a jacketed three-compartment cell thermostated at 25~ Rapid .cyclic voltammetric data were acquired on a Tektronix 5103N oscilloscope with 5A15N and 5A18N plug-ins using a C-5A camera. The hanging mercury drop elect...

show abstract

Bioelectrochemistry: An Examination of Some Examples

Cited by 7 publications

References 137 publications

Pressure dependences of the electrode potentials of some iron(III/II) and cobalt(III/II) couples in aqueous solution

Pressure dependences of the electrode potentials of some iron(III/II) and cobalt(III/II) couples in aqueous solution

Relationship between Heterogeneous and Homogeneous Kinetics of Electron Transfer between Transition Metal Complexes in Aqueous Solution: Volumes of Activation

Electrochemical Reduction of Nicotinamide Adenine Dinucleotide in Dimethylsulfoxide: Ion‐Pair, Protonation, and Adsorption Effects

Contact Info

Product

Resources

About