Electrochemical time-of-flight responses at double-band generator-collector devices under pulsed conditions

Amatore, Christian; Sella, C.; Thouin, Laurent

doi:10.1016/j.jelechem.2006.04.002

Cited by 45 publications

(53 citation statements)

References 22 publications

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“…These two issues were resolved by applying a pulsed potential at the generating electrode, and pulse experiments then became the norm. 28 Pulsing the potential at the generator produces a transientpeak seen in the amperometric display at the collector, Figure 2. Using this peak-shape, it is much easier to determine the time of flight, and the brief duration of the pulse does not generate enough material to allow feedback.…”

Section: Resultsmentioning

confidence: 99%

“…Using this peak-shape, it is much easier to determine the time of flight, and the brief duration of the pulse does not generate enough material to allow feedback. Pulse widths for the generator were selected after consulting a paper by Amatore,28 so that the potential pulse applied to the generator would be less than the shortest time, t min , (Equation 5) for the molecule to diffuse between the two electrodes (otherwise redox cycling could occur).…”

Section: Resultsmentioning

confidence: 99%

“…27 The two electrodes are within micrometers of each other and are often members of a microelectrode array. 25,[28][29][30][31][32][33] The time it takes the product from the generator to diffuse to the nearest edge of the collector is the time of flight. If a potential pulse is applied to the generator, a burst of product diffuses to the collector (Figure 2), and the time of maximum collection, t mc , is measured.…”

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Rapid and Direct Determination of Diffusion Coefficients Using Microelectrode Arrays

Moldenhauer

Meier

Paul

2016

J. Electrochem. Soc.

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The sensitivity of amperometric sensors is typically set by the rate diffusion of the analyte to the electrode surface, so determining diffusion coefficients in various electrolyte solutions is of fundamental interest. It has been theoretically shown and verified that diffusion coefficients of electrochemically generated analytes can be determined using electrochemical time of flight (ETOF), a method that uses an electrochemical array in which one electrode generates a Red/Ox species, and measures the analyte diffusion times to collecting electrodes of differing distances from a stationary generator. ETOF has the potential to greatly simplify the determination of diffusion coefficients as the analyte concentration, the electroactive area, the solution viscosity, and the electron transfer kinetics can remain unknown. Here we demonstrate an alternative data treatment for ETOF in which the electrochemical flight time is measured for a series of different Red/Ox species of known diffusion coefficients at a single distance. We show this a valid application of a method that has existed for almost 30 years, by determining diffusion coefficients for ruthenium (II) hexamine, and diffusion coefficients in solutions of increased viscosity. Diffusion coefficients are important because they set the sensitivity of amperometric sensors and they are a fundamental property both in membrane permeability and in electrochemical measurements. The most common method of determining diffusion coefficients for analytes in bulk solutions or through gels and membranes relies on the rotating disk electrode (RDEs) 1-7 or the rotating ring disk electrode (RRDE).8 This method determines the diffusion coefficients, D, from the slope of a Levich plot constructed by measuring limiting currents, I L , as a function of square root of the rotation rate, w, according to the Levich equation (Equation 1).Accurate values for the area of the electrode, A, the number of electrons transferred, n, the concentration of the molecule, C, and the viscosity of the solution, v, must also be known in order to effectively determine the diffusion coefficient from the slope of a Levich Plot. The diffusion coefficients of molecules through bulk solution can also be determined quantitatively by wall-jet chronoamperometry, 9 or qualitatively by comparing the CV's of different compounds because the shape of the CV is related to the diffusion coefficient of the molecule. [10][11][12] The other primary option for determining diffusion coefficients of a molecule through a membrane coated over an electrode is impedance spectroscopy, [13][14][15][16][17][18] where the diffusion of the molecule through a membrane or polymer is related to the impedance of the polymer or membrane to current flow. As such, the diffusion through the polymer is related directly to the resistance of charge transfer (mobility) through the membrane, which is related to its conductivity and directly correlated to the diffusion coefficient by the Nernst-Einstein equation (Equation 2).Conductance, σ, ca...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Rapid and Direct Determination of Diffusion Coefficients Using Microelectrode Arrays

Moldenhauer

Meier

Paul

2016

J. Electrochem. Soc.

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“…al. 33 have theoretically investigated applying potential pulses to the generator electrode, and using the response at the collector electrode to obtain a time of flight for the electrogenerated species, and hence a measure of its diffusion coefficient.…”

Section: Introductionmentioning

confidence: 99%

Dual band electrodes in generator–collector mode: Simultaneous measurement of two species

Barnes

Lewis

Dale

et al. 2013

Journal of Electroanalytical Chemistry

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A computational model for the simulation of a double band collector-generator experiment is applied to the situation where two electrochemical reactions occur concurrently. It is shown that chronoamperometric measurements can be used to take advantage of differences in diffusion coefficients to measure the concentrations of both electroactive species simultaneously, by measuring the time at which the collection efficiency reaches a specific value. The separation of the electrodes is shown to not affect the sensitivity of the method (in terms of percentage changes in the measured time to reach the specified collection efficiency), but wider gaps can provide a greater range of (larger) absolute values of this characteristic time. It is also shown that measuring the time taken to reach smaller collection efficiencies can allow for the detection of smaller amounts of whichever species diffuses faster. The case of a system containing both ascorbic acid and dopamine in water is used to exemplify the method, and it is shown that mole fractions of ascorbic acid between 0.055 and 0.96 can, in principle, be accurately measured.

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“…In addition to these advantages, microband electrodes have emerged as being experimentally useful, and have found steadily increasing use in hydrodynamic voltammetry in a flow cell, [22][23][24][25][26][27][28][29] in dual electrode generator-collector mode, [30][31][32][33][34][35] and in impedance spectroscopy. 36,37 One of the key differences in electrochemistry carried out at microbands, as opposed to microdiscs, is the absence of a true steady state in chornoamperometry at microbands.…”

Section: Introductionmentioning

confidence: 99%

Double potential step chronoamperometry at a microband electrode: Theory and experiment

Barnes¹,

Xiong²,

Ward³

et al. 2013

Journal of Electroanalytical Chemistry

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Numerical simulation is used to characterise double potential step chronoamperometry at a microband electrode for a simple redox process, A + e − ⇋ B, under conditions of full support such that diffusion is the only active form of mass transport. The method is shown to be highly sensitive for the measurement of the diffusion coefficients of both A and B, and is applied to the one electron oxidation of decamethylferrocene (DMFc), DMFc − e − ⇋ DMFc + , in the room temperature ionic liquid 1-propyl-3-methylimidazolium bistrifluoromethylsulfonylimide.Theory and experiment are seen to be in excellent agreement and the following values of the diffusion coefficients were measured at 298 K: D DMFc = 2.50 × 10 −7 cm 2 s −1 and D DMFc + = 9.50 × 10 −8 cm 2 s −1 .

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Electrochemical time-of-flight responses at double-band generator-collector devices under pulsed conditions

Cited by 45 publications

References 22 publications

Rapid and Direct Determination of Diffusion Coefficients Using Microelectrode Arrays

Rapid and Direct Determination of Diffusion Coefficients Using Microelectrode Arrays

Dual band electrodes in generator–collector mode: Simultaneous measurement of two species

Double potential step chronoamperometry at a microband electrode: Theory and experiment

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