Advective and transient effects in combined AFM/SECM operation

Kottke, Peter A.; Fedorov, Andrei G.

doi:10.1016/j.jelechem.2005.06.017

Cited by 10 publications

(13 citation statements)

References 41 publications

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“…[38] Diffusivity for each species is uniform in the electrolyte (D i ) and in the polymer (=α i D i ). Species transport across the polymer/electrolyte interface is rapid, so that local equilibrium prevails and at the interface a partitioning coefficient, θ i , relates the concentration inside the polymer to that in the solution.…”

Section: Table IIImentioning

confidence: 99%

“…This is because most available models such as those of Savéant and co-authors [14,[26][27][28][29] and others [30][31][32][33][34][35][36][37] are based on 1-D planar diffusion, usually with the enzyme reaction confined to a monolayer. But 3-D steady-state diffusion dominates in amperometric UME operation [38], and to date analytical models to describe these conditions are limited to extremely large [39] or infinite [40] entrapment domains, which electrodeposition is intended to avoid. Hence, a first principles theoretical model describing the electrodeposited polymer-entrapped enzyme microelectrode experiment is missing, and both interpretation of results and design of the microprobes are at present entirely empirical.…”

Section: Introductionmentioning

confidence: 99%

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Theory of polymer entrapped enzyme ultramicroelectrodes: Fundamentals

Kottke

Kranz

Kwon

et al. 2008

Journal of Electroanalytical Chemistry

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We have developed a theoretical description of the amperometric response of ultramicroelectrode (UME) biosensors formed via enzyme entrapment. Our model allows for multiple enzymes and cosubstrates, and results in a closed-form analytical expression for the steady-state current response of the disk ultramicroelectrode. It captures the effects of enzyme-entrapment domain size, species transport properties (which can be different in the polymer and surrounding electrolyte), enzyme kinetics, and axisymmetric diffusion. Assumptions inherent in the derivation are carefully explained, as are the resulting limits on the applicability of the results. The ability to theoretically predict the response of enzyme entrapped UMEs should enable improved design, operation, and data interpretation for this important class of biosensors.

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Section: Table IIImentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Theory of polymer entrapped enzyme ultramicroelectrodes: Fundamentals

Kottke

Kranz

Kwon

et al. 2008

Journal of Electroanalytical Chemistry

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“…For the third component both forced and natural convection have to be taken into account [6]. Kottke et al [8] described that the hydrodynamic effects arising from the horizontal probe movement can be neglected for a combined AFM/SECM frame electrode geometry when the Peclet number is less than 0.1. Only a small number of SECM experiments with forced convection are described in literature: Combellas et al.…”

Section: Introductionmentioning

confidence: 99%

Impacts of Forced Convection Generated via High Precision Stirring on Scanning Electrochemical Microscopy Experiments in Feedback Mode

et al. 2018

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In this study, the effects of forced convection on scanning electrochemical microscopy (SECM) experiments in feedback mode using ferrocenemethanol as redox mediator are presented. Forced convection, which enhances the mass transfer inside the system, was generated via an electrical high precision stirrer integrated into the SECM setup. A thin‐film interdigitated array electrode serving as model substrate was investigated with probe scan curves in z‐direction and SECM imaging in constant height mode utilizing ultramicroelectrodes (UME) with diameters (dprobe) of 25 μm and 12.5 μm. It was found that forced convection increased the overall current during SECM imaging without distorting distinctive features of the imaged structure when working with a 25 μm UME at substrate‐to‐tip distances of 14 μm and 11 μm. Furthermore, the electrochemical contrast was improved under hydrodynamic conditions for a substrate‐to‐tip distance of 11 μm and scan rates of 5 μm s−1, 10 μm s−1, 20 μm s−1 and 40 μm s−1. When further decreasing the gap between the UME and the substrate to 9 μm almost no effects of the forced convection were observed. Consequently, for a 25 μm UME, forced convection led to higher currents and improved performance during SECM experiments in feedback mode at substrate‐to‐tip distances of 14 μm and 11 μm, whereas no effects were observed for a 12.5 μm UME at a distance of 8 μm.

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mentioning

confidence: 99%

“…Forced convection occurs as a result of the displacement of the microelectrode or substrate. It has been studied for the displacement of the microelectrode in a plane parallel to that of the substrate, , in a direction normal to the plane of the substrate and for a vertically oscillating microelectrode . Modeling efforts, which were corroborated with experiments, were performed in SECM studies in deep eutectic solvents or in ionic liquids. , In fact, despite the well-established importance of convective effects when performing SECM approach curves in aqueous solvent, to the best of our knowledge, no general and quantitative discussion is available on the subject.…”

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confidence: 99%

Forced Convection during Feedback Approach Curve Measurements in Scanning Electrochemical Microscopy: Maximal Displacement Velocity with a Microdisk

2012

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In scanning electrochemical microscopy (SECM), an approach curve performed in feedback mode involves the downward displacement of a microelectrode toward a substrate while applying a bias to detect dissolved electroactive species at a diffusion-limited rate. The resulting measured current is said to be at steady state. In order to reduce the required measurement time, the approach velocity can be increased. In this paper, we investigate experimentally and theoretically the combination of diffusion and convection processes related to a moving microdisk electrode during feedback approaches. Transient modeling and numerical simulations with moving boundaries are performed, and the results are compared to the experimental approach curves obtained in aqueous solution. The geometry and misalignment of the microelectrode influence the experimental approach curves recorded at high approach velocities. The effects are discussed through the decomposition of the current into transient diffusional, radial convectional, and axial convectional contributions. Finally a ready-to-use expression is provided to rapidly evaluate the maximal approach velocity for steady state measurements as a function of the microelectrode geometry and the physical properties of the media. This expression holds for the more restrictive case of negative feedback as well as other modes, such as SECM approach curves performed at substrates displaying first order kinetics.

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Advective and transient effects in combined AFM/SECM operation

Cited by 10 publications

References 41 publications

Theory of polymer entrapped enzyme ultramicroelectrodes: Fundamentals

Theory of polymer entrapped enzyme ultramicroelectrodes: Fundamentals

Impacts of Forced Convection Generated via High Precision Stirring on Scanning Electrochemical Microscopy Experiments in Feedback Mode

Forced Convection during Feedback Approach Curve Measurements in Scanning Electrochemical Microscopy: Maximal Displacement Velocity with a Microdisk

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