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Chargé de recherche ENS – Département de chimie Email: oleksandr.oliynyk@ens.psl.eu |
Research interests
- electrochemistry
- physical chemistry underlying biological processes
- mathematical modelling
- simulations
Publications
2019 |
A few key theoretical issues of importance in modern molecular electrochemistry Article de journal A Oleinick; I Svir; C Amatore Current Opinion in Electrochemistry, 13 , p. 33–39, 2019. @article{Oleinick:2019, title = {A few key theoretical issues of importance in modern molecular electrochemistry}, author = {A Oleinick and I Svir and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85055740357&doi=10.1016%2fj.coelec.2018.10.008&partnerID=40&md5=66d914e114859b27e787b505b26c824d}, doi = {10.1016/j.coelec.2018.10.008}, year = {2019}, date = {2019-01-01}, journal = {Current Opinion in Electrochemistry}, volume = {13}, pages = {33--39}, keywords = {}, pubstate = {published}, tppubtype = {article} } |
Theory and Simulations for the Electron Transfer/Ion Transfer Mode of SECM with Electroactive Species Present in Both Liquid Phases Article de journal A Oleinick; Y Yu; M V Mirkin; I Svir; C Amatore ChemElectroChem, 6 (1), p. 189–194, 2019. @article{Oleinick:2019a, title = {Theory and Simulations for the Electron Transfer/Ion Transfer Mode of SECM with Electroactive Species Present in Both Liquid Phases}, author = {A Oleinick and Y Yu and M V Mirkin and I Svir and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059301854&doi=10.1002%2fcelc.201800793&partnerID=40&md5=4be2ca0a68611e905a025b50b20e54bd}, doi = {10.1002/celc.201800793}, year = {2019}, date = {2019-01-01}, journal = {ChemElectroChem}, volume = {6}, number = {1}, pages = {189--194}, abstract = {The electron transfer/ion transfer mode of scanning electrochemical microscopy (SECM), in which a nanopipette containing a solvent immiscible with the outer solution is used as a tip to approach a microelectrode substrate, is investigated by simulations in order to analyze the effect of the electroactive species being simultaneously present inside the nanopipette and in the external liquid phase. The simulations consider conventional transport modes of the species inside the nanopipette as well as in the bulk solution coupled with their transfer across the liquid-liquid nanointerface supported at the nanopipette tip. The shapes of the simulated approach curves (tip current vs. tip-substrate distance) are highly sensitive to the ratio of initial concentrations in the nanopipette and in the outer solution for a given partition coefficient value providing a direct method to determine its value. The effect of the 1st and 2nd order homogeneous reaction consuming the product electrogenerated at the microelectrode surface onto its collection by the nanopipette is also presented. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim}, keywords = {}, pubstate = {published}, tppubtype = {article} } The electron transfer/ion transfer mode of scanning electrochemical microscopy (SECM), in which a nanopipette containing a solvent immiscible with the outer solution is used as a tip to approach a microelectrode substrate, is investigated by simulations in order to analyze the effect of the electroactive species being simultaneously present inside the nanopipette and in the external liquid phase. The simulations consider conventional transport modes of the species inside the nanopipette as well as in the bulk solution coupled with their transfer across the liquid-liquid nanointerface supported at the nanopipette tip. The shapes of the simulated approach curves (tip current vs. tip-substrate distance) are highly sensitive to the ratio of initial concentrations in the nanopipette and in the outer solution for a given partition coefficient value providing a direct method to determine its value. The effect of the 1st and 2nd order homogeneous reaction consuming the product electrogenerated at the microelectrode surface onto its collection by the nanopipette is also presented. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim |
2018 |
A Oleinick; I Álvarez-Martos; I Svir; E E Ferapontova; C Amatore Journal of the Electrochemical Society, 165 (12), p. G3057–G3065, 2018. @article{Oleinick:2018, title = {Surface heterogeneities matter in fast scan cyclic voltammetry investigations of catecholamines in brain with carbon microelectrodes of high-aspect ratio: Dopamine oxidation at conical carbon microelectrodes}, author = {A Oleinick and I \'{A}lvarez-Martos and I Svir and E E Ferapontova and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85059173298&doi=10.1149%2f2.0071812jes&partnerID=40&md5=4751c86ba06b3c5f0fa6fcd52c813ff6}, doi = {10.1149/2.0071812jes}, year = {2018}, date = {2018-01-01}, journal = {Journal of the Electrochemical Society}, volume = {165}, number = {12}, pages = {G3057--G3065}, abstract = {Fast Scan Cyclic Voltammetry (FSCV) at high aspect ratio carbon microelectrodes shows adequate high temporal and spatial resolution for in vivo analysis of catecholamines. Though the presence of their surface heterogeneities has been recognized since their earliest introduction for in vivo measurements in the brain, the kinetic consequences on the measurements have not been investigated and FSCV measurements are treated based on pre- and post-calibrations. We establish here that surface heterogeneities play a consequent dynamic role on the oxidation of dopamine taken as an example of catecholamines. Hence, the FSCV current peak intensities do not scale with the scan rate v or its square root. This is rationalized with a simple model involving a co-existence of at least two types of surface nanodomains with different electrochemical reactivities and different time responses. At low scan rates (textless100 V s-1) dopamine molecules that initially adsorbed onto non-electroactive nanodomains have enough time to migrate toward highly electroactive ones so all molecules initially adsorbed on the whole electrode surface may be oxidized during one FSCV cycle. Current peak intensities then increase proportionally to the scan rate. However, above 100 V s-1, dopamine migration between sites starts to be kinetically limited so that FSCV current peak intensities do not increase any more proportionally to the scan rate. Ultimately, i.e., above 1000 V s-1, the dopamine exchange between sites is almost totally blocked so only dopamine molecules initially adsorbed on the electroactive surface nanodomains may be oxidized; the current peak intensities then increase again proportionally with the scan rate though with a smaller slope than that observed at small scan rates. Since carbon fibers with large aspect ratios are frequently used in brain investigations, this effect should be a concern when extracting quantitative results even when each carbon fiber response is properly pre- or post-calibrated using the exact CV waveform and scan rate used during the in vivo measurements. © The Author(s) 2018.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Fast Scan Cyclic Voltammetry (FSCV) at high aspect ratio carbon microelectrodes shows adequate high temporal and spatial resolution for in vivo analysis of catecholamines. Though the presence of their surface heterogeneities has been recognized since their earliest introduction for in vivo measurements in the brain, the kinetic consequences on the measurements have not been investigated and FSCV measurements are treated based on pre- and post-calibrations. We establish here that surface heterogeneities play a consequent dynamic role on the oxidation of dopamine taken as an example of catecholamines. Hence, the FSCV current peak intensities do not scale with the scan rate v or its square root. This is rationalized with a simple model involving a co-existence of at least two types of surface nanodomains with different electrochemical reactivities and different time responses. At low scan rates (textless100 V s-1) dopamine molecules that initially adsorbed onto non-electroactive nanodomains have enough time to migrate toward highly electroactive ones so all molecules initially adsorbed on the whole electrode surface may be oxidized during one FSCV cycle. Current peak intensities then increase proportionally to the scan rate. However, above 100 V s-1, dopamine migration between sites starts to be kinetically limited so that FSCV current peak intensities do not increase any more proportionally to the scan rate. Ultimately, i.e., above 1000 V s-1, the dopamine exchange between sites is almost totally blocked so only dopamine molecules initially adsorbed on the electroactive surface nanodomains may be oxidized; the current peak intensities then increase again proportionally with the scan rate though with a smaller slope than that observed at small scan rates. Since carbon fibers with large aspect ratios are frequently used in brain investigations, this effect should be a concern when extracting quantitative results even when each carbon fiber response is properly pre- or post-calibrated using the exact CV waveform and scan rate used during the in vivo measurements. © The Author(s) 2018. |
Self-Inhibitory Electron Transfer of the Co(III)/Co(II)-Complex Redox Couple at Pristine Carbon Electrode Article de journal R Chen; A M Najarian; N Kurapati; R J Balla; A Oleinick; I Svir; C Amatore; R L McCreery; S Amemiya Analytical Chemistry, 90 (18), p. 11115–11123, 2018. @article{Chen:2018a, title = {Self-Inhibitory Electron Transfer of the Co(III)/Co(II)-Complex Redox Couple at Pristine Carbon Electrode}, author = {R Chen and A M Najarian and N Kurapati and R J Balla and A Oleinick and I Svir and C Amatore and R L McCreery and S Amemiya}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85052875574&doi=10.1021%2facs.analchem.8b03023&partnerID=40&md5=3a1da59f40e9ffd3e5b85cb76a95fc51}, doi = {10.1021/acs.analchem.8b03023}, year = {2018}, date = {2018-01-01}, journal = {Analytical Chemistry}, volume = {90}, number = {18}, pages = {11115--11123}, abstract = {Applications of conducting carbon materials for highly efficient electrochemical energy devices require a greater fundamental understanding of heterogeneous electron-transfer (ET) mechanisms. This task, however, is highly challenging experimentally, because an adsorbing carbon surface may easily conceal its intrinsic reactivity through adventitious contamination. Herein, we employ nanoscale scanning electrochemical microscopy (SECM) and cyclic voltammetry to gain new insights into the interplay between heterogeneous ET and adsorption of a Co(III)/Co(II)-complex redox couple at the contamination-free surface of electron-beam-deposited carbon (eC). Specifically, we investigate the redox couple of tris(1,10-phenanthroline)cobalt(II), Co(phen)3 2+, as a promising mediator for dye-sensitized solar cells and redox flow batteries. A pristine eC surface overlaid with KCl is prepared in vacuum, protected from contamination in air, and exposed to an ultrapure aqueous solution of Co(phen)3 2+ by the dissolution of the protective KCl layer. We employ SECM-based nanogap voltammetry to quantitatively demonstrate that Co(phen)3 2+ is adsorbed on the pristine eC surface to electrostatically self-inhibit outer-sphere ET of nonadsorbed Co(phen)3 3+ and Co(phen)3 2+. Strong electrostatic repulsion among Co(phen)3 2+ adsorbates is also demonstrated by SECM-based nanogap voltammetry and cyclic voltammetry. Quantitatively, self-inhibitory ET is characterized by a linear decrease in the standard rate constant of Co(phen)3 2+ oxidation with a higher surface concentration of Co(phen)3 2+ at the formal potential. This unique relationship is consistent not with the Frumkin model of double layer effects, but with the Amatore model of partially blocked electrodes as extended for self-inhibitory ET. Significantly, the complicated coupling of electron transfer and surface adsorption is resolved by combining nanoscale and macroscale voltammetric methods. © 2018 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Applications of conducting carbon materials for highly efficient electrochemical energy devices require a greater fundamental understanding of heterogeneous electron-transfer (ET) mechanisms. This task, however, is highly challenging experimentally, because an adsorbing carbon surface may easily conceal its intrinsic reactivity through adventitious contamination. Herein, we employ nanoscale scanning electrochemical microscopy (SECM) and cyclic voltammetry to gain new insights into the interplay between heterogeneous ET and adsorption of a Co(III)/Co(II)-complex redox couple at the contamination-free surface of electron-beam-deposited carbon (eC). Specifically, we investigate the redox couple of tris(1,10-phenanthroline)cobalt(II), Co(phen)3 2+, as a promising mediator for dye-sensitized solar cells and redox flow batteries. A pristine eC surface overlaid with KCl is prepared in vacuum, protected from contamination in air, and exposed to an ultrapure aqueous solution of Co(phen)3 2+ by the dissolution of the protective KCl layer. We employ SECM-based nanogap voltammetry to quantitatively demonstrate that Co(phen)3 2+ is adsorbed on the pristine eC surface to electrostatically self-inhibit outer-sphere ET of nonadsorbed Co(phen)3 3+ and Co(phen)3 2+. Strong electrostatic repulsion among Co(phen)3 2+ adsorbates is also demonstrated by SECM-based nanogap voltammetry and cyclic voltammetry. Quantitatively, self-inhibitory ET is characterized by a linear decrease in the standard rate constant of Co(phen)3 2+ oxidation with a higher surface concentration of Co(phen)3 2+ at the formal potential. This unique relationship is consistent not with the Frumkin model of double layer effects, but with the Amatore model of partially blocked electrodes as extended for self-inhibitory ET. Significantly, the complicated coupling of electron transfer and surface adsorption is resolved by combining nanoscale and macroscale voltammetric methods. © 2018 American Chemical Society. |
2017 |
Theory and Simulations for the Electron-Transfer/Ion-Transfer Mode of Scanning Electrochemical Microscopy in the Presence or Absence of Homogenous Kinetics Article de journal A Oleinick; Y Yu; I Svir; M V Mirkin; C Amatore ChemElectroChem, 4 (2), p. 240, 2017. @article{Oleinick:2017a, title = {Theory and Simulations for the Electron-Transfer/Ion-Transfer Mode of Scanning Electrochemical Microscopy in the Presence or Absence of Homogenous Kinetics}, author = {A Oleinick and Y Yu and I Svir and M V Mirkin and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85012033983&doi=10.1002%2fcelc.201700007&partnerID=40&md5=e7cc4a3b4e9158de2c39a7157c55f923}, doi = {10.1002/celc.201700007}, year = {2017}, date = {2017-01-01}, journal = {ChemElectroChem}, volume = {4}, number = {2}, pages = {240}, abstract = {The front cover artwork is provided by the groups of Amatore (Paris, France) and Mirkin (New York, USA). The image illustrates the delivered and captured flux gradients inside the nanopipette as well as those generated inside the nanocleft delimited by the nanopipette tip and the electrode surface. It is a single-barrel nanopipette, so the two gradients are artificially separated for graphical purposes by their individual projection on each face of the crosscut volume. Read the full text of the Article at 10.1002/celc.201600583. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim}, keywords = {}, pubstate = {published}, tppubtype = {article} } The front cover artwork is provided by the groups of Amatore (Paris, France) and Mirkin (New York, USA). The image illustrates the delivered and captured flux gradients inside the nanopipette as well as those generated inside the nanocleft delimited by the nanopipette tip and the electrode surface. It is a single-barrel nanopipette, so the two gradients are artificially separated for graphical purposes by their individual projection on each face of the crosscut volume. Read the full text of the Article at 10.1002/celc.201600583. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim |
'Full fusion' is not ineluctable during vesicular exocytosis of neurotransmitters by endocrine cells Article de journal A Oleinick; I Svir; C Amatore Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 473 (2197), 2017. @article{Oleinick:2017, title = {'Full fusion' is not ineluctable during vesicular exocytosis of neurotransmitters by endocrine cells}, author = {A Oleinick and I Svir and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85012267482&doi=10.1098%2frspa.2016.0684&partnerID=40&md5=3c81df82a97660c3dfd84fff3fb41bf0}, doi = {10.1098/rspa.2016.0684}, year = {2017}, date = {2017-01-01}, journal = {Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences}, volume = {473}, number = {2197}, abstract = {Vesicular exocytosis is an essential and ubiquitous process in neurons and endocrine cells by which neurotransmitters are released in synaptic clefts or extracellular fluids. It involves the fusion of a vesicle loaded with chemical messengers with the cell membrane through a nanometric fusion pore. In endocrine cells, unless it closes after some flickering ('Kiss-And-Run' events), this initial pore is supposed to expand exponentially, leading to a full integration of the vesicle membrane into the cell membrane-A stage called 'full fusion'.We report here a compact analytical formulation that allows precise measurements of the fusion pore expansion extent and rate to be extracted from individual amperometric spike time courses. These data definitively establish that, during release of catecholamines, fusion pores enlarge at most to approximately one-fifth of the radius of their parent vesicle, hence ruling out the ineluctability of 'full fusion'. © 2017 The Author(s) Published by the Royal Society. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Vesicular exocytosis is an essential and ubiquitous process in neurons and endocrine cells by which neurotransmitters are released in synaptic clefts or extracellular fluids. It involves the fusion of a vesicle loaded with chemical messengers with the cell membrane through a nanometric fusion pore. In endocrine cells, unless it closes after some flickering ('Kiss-And-Run' events), this initial pore is supposed to expand exponentially, leading to a full integration of the vesicle membrane into the cell membrane-A stage called 'full fusion'.We report here a compact analytical formulation that allows precise measurements of the fusion pore expansion extent and rate to be extracted from individual amperometric spike time courses. These data definitively establish that, during release of catecholamines, fusion pores enlarge at most to approximately one-fifth of the radius of their parent vesicle, hence ruling out the ineluctability of 'full fusion'. © 2017 The Author(s) Published by the Royal Society. All rights reserved. |
Theory and Simulation for Optimising Electrogenerated Chemiluminescence from Tris(2,2′-bipyridine)-ruthenium(II)-Doped Silica Nanoparticles and Tripropylamine Article de journal E Daviddi; A Oleinick; I Svir; G Valenti; F Paolucci; C Amatore ChemElectroChem, 4 (7), p. 1719–1730, 2017. @article{Daviddi:2017, title = {Theory and Simulation for Optimising Electrogenerated Chemiluminescence from Tris(2,2′-bipyridine)-ruthenium(II)-Doped Silica Nanoparticles and Tripropylamine}, author = {E Daviddi and A Oleinick and I Svir and G Valenti and F Paolucci and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85013389437&doi=10.1002%2fcelc.201600892&partnerID=40&md5=58248a4f00465b64263aafc5607447e1}, doi = {10.1002/celc.201600892}, year = {2017}, date = {2017-01-01}, journal = {ChemElectroChem}, volume = {4}, number = {7}, pages = {1719--1730}, abstract = {Electrochemiluminescence (ECL), that is, light emission from an electronically excited species generated by electrochemical means, sustains powerful (bio)analytical methods for the ultrasensitive detection of biological targets. Co-reactant systems involving an inexpensive organic molecule, most generally a tertiary amine, and a metal complex luminophore are commonly used for such purposes. Owing to the high cost of the luminophore moiety, several groups have considered minimising its quantity by sequestrating it at high concentration inside nanoparticles. However, to be efficient and to optimise ECL responses, this strategy requires that the nanoparticle carrier is suitably placed inside the diffusion layer of the oxidised organic co-reactant. In this work, we firstly investigated this optimisation problem by introducing a rather simple analytical model to delineate qualitatively the main mechanistic features controlling the ECL intensity. This was then analysed in more detail by using 2D simulations. Analysis of these 2D-heavy simulations in terms of memory occupation and CPU time, evidenced that similar results (i. e. with a relative precision best than a few percent) could be achieved with much faster 1D simulations. These 1D simulations allowed specifying quantitatively the main features of the analytical model qualitative predictions and to propose simple rules for the optimisation of the luminophore-doped nanoparticles placement inside the diffusion layer of the organic co-reactant. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim}, keywords = {}, pubstate = {published}, tppubtype = {article} } Electrochemiluminescence (ECL), that is, light emission from an electronically excited species generated by electrochemical means, sustains powerful (bio)analytical methods for the ultrasensitive detection of biological targets. Co-reactant systems involving an inexpensive organic molecule, most generally a tertiary amine, and a metal complex luminophore are commonly used for such purposes. Owing to the high cost of the luminophore moiety, several groups have considered minimising its quantity by sequestrating it at high concentration inside nanoparticles. However, to be efficient and to optimise ECL responses, this strategy requires that the nanoparticle carrier is suitably placed inside the diffusion layer of the oxidised organic co-reactant. In this work, we firstly investigated this optimisation problem by introducing a rather simple analytical model to delineate qualitatively the main mechanistic features controlling the ECL intensity. This was then analysed in more detail by using 2D simulations. Analysis of these 2D-heavy simulations in terms of memory occupation and CPU time, evidenced that similar results (i. e. with a relative precision best than a few percent) could be achieved with much faster 1D simulations. These 1D simulations allowed specifying quantitatively the main features of the analytical model qualitative predictions and to propose simple rules for the optimisation of the luminophore-doped nanoparticles placement inside the diffusion layer of the organic co-reactant. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim |
Theory and Simulations for the Electron-Transfer/Ion-Transfer Mode of Scanning Electrochemical Microscopy in the Presence or Absence of Homogenous Kinetics Article de journal A Oleinick; Y Yu; I Svir; M V Mirkin; C Amatore ChemElectroChem, 4 (2), p. 287–295, 2017. @article{Oleinick:2017b, title = {Theory and Simulations for the Electron-Transfer/Ion-Transfer Mode of Scanning Electrochemical Microscopy in the Presence or Absence of Homogenous Kinetics}, author = {A Oleinick and Y Yu and I Svir and M V Mirkin and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85003977008&doi=10.1002%2fcelc.201600583&partnerID=40&md5=c6b701d106630916aa1371290c7514b5}, doi = {10.1002/celc.201600583}, year = {2017}, date = {2017-01-01}, journal = {ChemElectroChem}, volume = {4}, number = {2}, pages = {287--295}, abstract = {The electron-transfer/ion-transfer (ET/IT) mode of scanning electrochemical microscopy (SECM) was developed recently and applied to studies of heterogeneous reactions at the substrate surface. The charged products or intermediates are detected by measuring the ion-transfer current of the species across the liquid/liquid interface supported at the tip of a nanopipette. In this article, we develop the theory for this technique and explore its potential advantages and limitations. By using the COMSOL Multiphysics package, the approach curves were simulated for three commonly encountered experimental situations, that is, the surface-generated ionic species is either chemically stable or participates in a first- or second-order homogeneous reaction. The simulation results are generalized in the form of analytical approximations derived under limiting conditions. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim}, keywords = {}, pubstate = {published}, tppubtype = {article} } The electron-transfer/ion-transfer (ET/IT) mode of scanning electrochemical microscopy (SECM) was developed recently and applied to studies of heterogeneous reactions at the substrate surface. The charged products or intermediates are detected by measuring the ion-transfer current of the species across the liquid/liquid interface supported at the tip of a nanopipette. In this article, we develop the theory for this technique and explore its potential advantages and limitations. By using the COMSOL Multiphysics package, the approach curves were simulated for three commonly encountered experimental situations, that is, the surface-generated ionic species is either chemically stable or participates in a first- or second-order homogeneous reaction. The simulation results are generalized in the form of analytical approximations derived under limiting conditions. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim |
Importance of stochastic limitations in electrochemistry at arrays of nanoelectrodes functionalized by redox self-assembled monolayers Article de journal O Y Sliusarenko; A I Oleinick; I B Svir; C A Amatore Russian Journal of Electrochemistry, 53 (9), p. 1019–1028, 2017. @article{Sliusarenko:2017, title = {Importance of stochastic limitations in electrochemistry at arrays of nanoelectrodes functionalized by redox self-assembled monolayers}, author = {O Y Sliusarenko and A I Oleinick and I B Svir and C A Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85029793437&doi=10.1134%2fS1023193517090129&partnerID=40&md5=2d0298e4a9aae98df767c3607b5547fa}, doi = {10.1134/S1023193517090129}, year = {2017}, date = {2017-01-01}, journal = {Russian Journal of Electrochemistry}, volume = {53}, number = {9}, pages = {1019--1028}, abstract = {In order to increase signal-to-noise (S/N) performances, the current trend in electro(bio)analytical chemistry consists in developing arrays whose electroactive components are considerably reduced in size and already approach the very nanoscale. A comparable situation involving nanoscale electroactive or electrocatalytic nanoparticles randomly dispersed on a flat non-electroactive surface is already extremely common. Similarly, insulating self-assembled monolayers (SAMs) are often modified by dispersed ‘molecular nanoelectrodes’ consisting of nanopatches of insulating tethers bearing redox-head groups exposed to the analyzed solution with the purpose of mediating/catalyzing electron transfer kinetics between a substrate and the electrode. Finally, most SAMs present randomly distributed nano-sized pinholes through which direct electron transfer from the underlying electrode and a dissolved substrate may occur. It is therefore clear that these continuous developments as well as the increasingly facile and low-cost access to nanofabrication techniques will soon let (bio)electroanalytical chemists to resort more and more often to arrays of functionalized nanoelectrodes or nanoparticles. However, the theoretical analyses and stochastic simulations reported in this work demonstrate that reaching the nanoscale implies a complete change of theoretical electrochemical paradigms. This is of extreme importance as soon as one wishes to rationalize quantitatively measurements involving nano-scaled electroactive components. Indeed, based on Brownian simulations, we established that beyond a dimension of a few tens of nanometers, stochastic effects strongly alter the meaning of the kinetic and thermodynamic measurements vs. those based on classical electrochemical models. © 2017, Pleiades Publishing, Ltd.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In order to increase signal-to-noise (S/N) performances, the current trend in electro(bio)analytical chemistry consists in developing arrays whose electroactive components are considerably reduced in size and already approach the very nanoscale. A comparable situation involving nanoscale electroactive or electrocatalytic nanoparticles randomly dispersed on a flat non-electroactive surface is already extremely common. Similarly, insulating self-assembled monolayers (SAMs) are often modified by dispersed ‘molecular nanoelectrodes’ consisting of nanopatches of insulating tethers bearing redox-head groups exposed to the analyzed solution with the purpose of mediating/catalyzing electron transfer kinetics between a substrate and the electrode. Finally, most SAMs present randomly distributed nano-sized pinholes through which direct electron transfer from the underlying electrode and a dissolved substrate may occur. It is therefore clear that these continuous developments as well as the increasingly facile and low-cost access to nanofabrication techniques will soon let (bio)electroanalytical chemists to resort more and more often to arrays of functionalized nanoelectrodes or nanoparticles. However, the theoretical analyses and stochastic simulations reported in this work demonstrate that reaching the nanoscale implies a complete change of theoretical electrochemical paradigms. This is of extreme importance as soon as one wishes to rationalize quantitatively measurements involving nano-scaled electroactive components. Indeed, based on Brownian simulations, we established that beyond a dimension of a few tens of nanometers, stochastic effects strongly alter the meaning of the kinetic and thermodynamic measurements vs. those based on classical electrochemical models. © 2017, Pleiades Publishing, Ltd. |
2016 |
Theoretical Model of Neurotransmitter Release during in Vivo Vesicular Exocytosis Based on a Grainy Biphasic Nano-Structuration of Chromogranins within Dense Core Matrixes Article de journal A Oleinick; R Hu; B Ren; Z -Q Tian; I Svir; C Amatore Journal of the Electrochemical Society, 163 (4), p. H3014–H3024, 2016. @article{Oleinick:2016a, title = {Theoretical Model of Neurotransmitter Release during in Vivo Vesicular Exocytosis Based on a Grainy Biphasic Nano-Structuration of Chromogranins within Dense Core Matrixes}, author = {A Oleinick and R Hu and B Ren and Z -Q Tian and I Svir and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84957596919&doi=10.1149%2f2.0031604jes&partnerID=40&md5=78cb83b2141e6bfbf153d977cb6ef06b}, doi = {10.1149/2.0031604jes}, year = {2016}, date = {2016-01-01}, journal = {Journal of the Electrochemical Society}, volume = {163}, number = {4}, pages = {H3014--H3024}, abstract = {Exocytosis from dense core vesicles is an important ubiquitous process by which neurotransmitters are released frommany cells. This has stimulated strong efforts to monitor and understand vesicular release events in order to infer their biological and physicochemical mechanisms. Though much has been achieved so far, many experimental observations remain unexplained, even puzzling, essentially because they envision that the vesicle matrixes consist of a homogeneous polyelectrolytic condensed phase encapsulated by the vesicles membranes. This work discloses a new model of dense core matrixes based on the physics of polyelectrolytes involving long chains of anionic moieties (here, chromogranins) condensed by a mixture of bulky monocations and small dications (here, catecholamines and calcium ions). It follows that matrixes cannot be homogeneous but necessarily consist of a dispersion of tightly compacted nano-grains immersed in a less condensed phase involving loosely folded chromogranin strands in which catecholamine cations may diffuse at significant rates. Even if such pomegranate-like description has to remain essentially theoretical up to when direct experimental means of testing is available, it leads to a whole set of predictions that are fully coherent with all experimental observations based on amperometric monitoring of vesicular exocytosis including some recent extremely puzzling ones. © The Author(s) 2015.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Exocytosis from dense core vesicles is an important ubiquitous process by which neurotransmitters are released frommany cells. This has stimulated strong efforts to monitor and understand vesicular release events in order to infer their biological and physicochemical mechanisms. Though much has been achieved so far, many experimental observations remain unexplained, even puzzling, essentially because they envision that the vesicle matrixes consist of a homogeneous polyelectrolytic condensed phase encapsulated by the vesicles membranes. This work discloses a new model of dense core matrixes based on the physics of polyelectrolytes involving long chains of anionic moieties (here, chromogranins) condensed by a mixture of bulky monocations and small dications (here, catecholamines and calcium ions). It follows that matrixes cannot be homogeneous but necessarily consist of a dispersion of tightly compacted nano-grains immersed in a less condensed phase involving loosely folded chromogranin strands in which catecholamine cations may diffuse at significant rates. Even if such pomegranate-like description has to remain essentially theoretical up to when direct experimental means of testing is available, it leads to a whole set of predictions that are fully coherent with all experimental observations based on amperometric monitoring of vesicular exocytosis including some recent extremely puzzling ones. © The Author(s) 2015. |
Theory of Microwell Arrays Performing as Generators-Collectors Based on a Single Bipolar Plane Electrode Article de journal A Oleinick; J Yan; B Mao; I Svir; C Amatore ChemElectroChem, 3 (3), p. 487–494, 2016. @article{Oleinick:2016, title = {Theory of Microwell Arrays Performing as Generators-Collectors Based on a Single Bipolar Plane Electrode}, author = {A Oleinick and J Yan and B Mao and I Svir and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84959870555&doi=10.1002%2fcelc.201500321&partnerID=40&md5=37dcfbe311275ab6649781e9f5920d07}, doi = {10.1002/celc.201500321}, year = {2016}, date = {2016-01-01}, journal = {ChemElectroChem}, volume = {3}, number = {3}, pages = {487--494}, abstract = {Electroanalytical arrays of microwells with increased sensitivity and virtual immunity to interferents have been previously reported by us. Such arrays were designed to be operated in a classical generator-collector mode but exhibited also similar properties when their common planar collector was left floating. This evidenced that the unbiased collector acted as a bipolar electrode. In this work, a theory is elaborated to investigate in great detail the generality of this phenomenon and its limits. This establishes that if the analyte pertains to a redox couple with relatively fast electron rate constants, the bipolar collector results to be almost as efficient as when biased, thus suppressing the need for a bi-potentiostat with obvious gain for analytical applications. Conversely, if the analyte rate constant of electron transfer is small, efficient operation in a bipolar mode remains feasible but requires a drastic decrease of the microwell density in the array. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Electroanalytical arrays of microwells with increased sensitivity and virtual immunity to interferents have been previously reported by us. Such arrays were designed to be operated in a classical generator-collector mode but exhibited also similar properties when their common planar collector was left floating. This evidenced that the unbiased collector acted as a bipolar electrode. In this work, a theory is elaborated to investigate in great detail the generality of this phenomenon and its limits. This establishes that if the analyte pertains to a redox couple with relatively fast electron rate constants, the bipolar collector results to be almost as efficient as when biased, thus suppressing the need for a bi-potentiostat with obvious gain for analytical applications. Conversely, if the analyte rate constant of electron transfer is small, efficient operation in a bipolar mode remains feasible but requires a drastic decrease of the microwell density in the array. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
The evidence for open and closed exocytosis as the primary release mechanism Article de journal L Ren; L J Mellander; J Keighron; A -S Cans; M E Kurczy; I Svir; A Oleinick; C Amatore; A G Ewing Quarterly Reviews of Biophysics, 49 , 2016. @article{Ren:2016, title = {The evidence for open and closed exocytosis as the primary release mechanism}, author = {L Ren and L J Mellander and J Keighron and A -S Cans and M E Kurczy and I Svir and A Oleinick and C Amatore and A G Ewing}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85026676293&doi=10.1017%2fS0033583516000081&partnerID=40&md5=e1d8889a8a2d8f7eff664daaa9068e15}, doi = {10.1017/S0033583516000081}, year = {2016}, date = {2016-01-01}, journal = {Quarterly Reviews of Biophysics}, volume = {49}, abstract = {Exocytosis is the fundamental process by which cells communicate with each other. The events that lead up to the fusion of a vesicle loaded with chemical messenger with the cell membrane were the subject of a Nobel Prize in 2013. However, the processes occurring after the initial formation of a fusion pore are very much still in debate. The release of chemical messenger has traditionally been thought to occur through full distention of the vesicle membrane, hence assuming exocytosis to be all or none. In contrast to the all or none hypothesis, here we discuss the evidence that during exocytosis the vesicle-membrane pore opens to release only a portion of the transmitter content during exocytosis and then close again. This open and closed exocytosis is distinct from kiss-and-run exocytosis, in that it appears to be the main content released during regular exocytosis. The evidence for this partial release via open and closed exocytosis is presented considering primarily the quantitative evidence obtained with amperometry. © Cambridge University Press 2016.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Exocytosis is the fundamental process by which cells communicate with each other. The events that lead up to the fusion of a vesicle loaded with chemical messenger with the cell membrane were the subject of a Nobel Prize in 2013. However, the processes occurring after the initial formation of a fusion pore are very much still in debate. The release of chemical messenger has traditionally been thought to occur through full distention of the vesicle membrane, hence assuming exocytosis to be all or none. In contrast to the all or none hypothesis, here we discuss the evidence that during exocytosis the vesicle-membrane pore opens to release only a portion of the transmitter content during exocytosis and then close again. This open and closed exocytosis is distinct from kiss-and-run exocytosis, in that it appears to be the main content released during regular exocytosis. The evidence for this partial release via open and closed exocytosis is presented considering primarily the quantitative evidence obtained with amperometry. © Cambridge University Press 2016. |
On the mechanism of electrochemical vesicle cytometry: chromaffin cell vesicles and liposomes Article de journal J Lovrić; N Najafinobar; J Dunevall; S Majdi; I Svir; A Oleinick; C Amatore; A G Ewing Faraday Discussions, 193 , p. 65–79, 2016. @article{Lovric:2016, title = {On the mechanism of electrochemical vesicle cytometry: chromaffin cell vesicles and liposomes}, author = {J Lovri\'{c} and N Najafinobar and J Dunevall and S Majdi and I Svir and A Oleinick and C Amatore and A G Ewing}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84991801725&doi=10.1039%2fc6fd00102e&partnerID=40&md5=cd72c2b9e8101a2f201b4334900214ba}, doi = {10.1039/c6fd00102e}, year = {2016}, date = {2016-01-01}, journal = {Faraday Discussions}, volume = {193}, pages = {65--79}, abstract = {The mechanism of mammalian vesicle rupture onto the surface of a polarized carbon fiber microelectrode during electrochemical vesicle cytometry is investigated. It appears that following adsorption to the surface of the polarized electrode, electroporation leads to the formation of a pore at the interface between a vesicle and the electrode and this is shown to be potential dependent. The chemical cargo is then released through this pore to be oxidized at the electrode surface. This makes it possible to quantify the contents as it restricts diffusion away from the electrode and coulometric oxidation takes place. Using a bottom up approach, lipid-only transmitter-loaded liposomes were used to mimic native vesicles and the rupture events occurred much faster in comparison with native vesicles. Liposomes with added peptide in the membrane result in rupture events with a lower duration than that of liposomes and faster in comparison to native vesicles. Diffusional models have been developed and suggest that the trend in pore size is dependent on soft nanoparticle size and diffusion of the content in the nanometer vesicle. In addition, it appears that proteins form a barrier for the membrane to reach the electrode and need to move out of the way to allow close contact and electroporation. The protein dense core in vesicles matrixes is also important in the dynamics of the events in that it significantly slows diffusion through the vesicle. © The Royal Society of Chemistry.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The mechanism of mammalian vesicle rupture onto the surface of a polarized carbon fiber microelectrode during electrochemical vesicle cytometry is investigated. It appears that following adsorption to the surface of the polarized electrode, electroporation leads to the formation of a pore at the interface between a vesicle and the electrode and this is shown to be potential dependent. The chemical cargo is then released through this pore to be oxidized at the electrode surface. This makes it possible to quantify the contents as it restricts diffusion away from the electrode and coulometric oxidation takes place. Using a bottom up approach, lipid-only transmitter-loaded liposomes were used to mimic native vesicles and the rupture events occurred much faster in comparison with native vesicles. Liposomes with added peptide in the membrane result in rupture events with a lower duration than that of liposomes and faster in comparison to native vesicles. Diffusional models have been developed and suggest that the trend in pore size is dependent on soft nanoparticle size and diffusion of the content in the nanometer vesicle. In addition, it appears that proteins form a barrier for the membrane to reach the electrode and need to move out of the way to allow close contact and electroporation. The protein dense core in vesicles matrixes is also important in the dynamics of the events in that it significantly slows diffusion through the vesicle. © The Royal Society of Chemistry. |
How "full" is "full fusion" during exocytosis from dense core vesicles? Effect of SDS on "quantal" release and final fusion pore size Article de journal R Hu; B Ren; C -J Lin; A Oleinick; I Svir; Z -Q Tian; C Amatore Journal of the Electrochemical Society, 163 (9), p. H853–H865, 2016. @article{Hu:2016, title = {How "full" is "full fusion" during exocytosis from dense core vesicles? Effect of SDS on "quantal" release and final fusion pore size}, author = {R Hu and B Ren and C -J Lin and A Oleinick and I Svir and Z -Q Tian and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84982705801&doi=10.1149%2f2.1071609jes&partnerID=40&md5=b03dfb259941d8362a121f86ebf9d38d}, doi = {10.1149/2.1071609jes}, year = {2016}, date = {2016-01-01}, journal = {Journal of the Electrochemical Society}, volume = {163}, number = {9}, pages = {H853--H865}, abstract = {In this work, release was elicited from PC12 using sufficiently small concentrations of sodium dodecyl sulfate (SDS) to perturb normal release mechanism in an attempt to reveal concealed information while keeping physiologically compatible conditions. Amperometry was used to monitor and quantify the released fluxes and kinetics in individual vesicular events. This showed that stimulating release with SDS 350 μM leads to a doubling of the quantity of catecholamine cations released per event and much larger release fluxes as compared to controls (release elicited with K+ 105 mM under same conditions) or SDS 250 μM. These quantitative measurements confirm our previous theoretical model and reports based on ex situ cytometric experiments on isolated PC12 vesicles, which established that release is far from being total under normal exocytotic conditions. Secondly, this establishes that the maximal size of fusion pores at the end of the "full fusion" phase is limited by some contraption unrelated to the membrane. Indeed, the present results are entirely consistent with the fact that SDS 350 μM allows the fusion pore to expand to a double size (ca. 28 nm radius) compared to controls and SDS 250 μM (ca. 14 nm radius). © The Author(s) 2016. Published by ECS. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this work, release was elicited from PC12 using sufficiently small concentrations of sodium dodecyl sulfate (SDS) to perturb normal release mechanism in an attempt to reveal concealed information while keeping physiologically compatible conditions. Amperometry was used to monitor and quantify the released fluxes and kinetics in individual vesicular events. This showed that stimulating release with SDS 350 μM leads to a doubling of the quantity of catecholamine cations released per event and much larger release fluxes as compared to controls (release elicited with K+ 105 mM under same conditions) or SDS 250 μM. These quantitative measurements confirm our previous theoretical model and reports based on ex situ cytometric experiments on isolated PC12 vesicles, which established that release is far from being total under normal exocytotic conditions. Secondly, this establishes that the maximal size of fusion pores at the end of the "full fusion" phase is limited by some contraption unrelated to the membrane. Indeed, the present results are entirely consistent with the fact that SDS 350 μM allows the fusion pore to expand to a double size (ca. 28 nm radius) compared to controls and SDS 250 μM (ca. 14 nm radius). © The Author(s) 2016. Published by ECS. All rights reserved. |
Enhancing the Bipolar Redox Cycling Efficiency of Plane-Recessed Microelectrode Arrays by Adding a Chemically Irreversible Interferent Article de journal D He; J Yan; F Zhu; Y Zhou; B Mao; A Oleinick; I Svir; C Amatore Analytical Chemistry, 88 (17), p. 8535–8541, 2016. @article{He:2016a, title = {Enhancing the Bipolar Redox Cycling Efficiency of Plane-Recessed Microelectrode Arrays by Adding a Chemically Irreversible Interferent}, author = {D He and J Yan and F Zhu and Y Zhou and B Mao and A Oleinick and I Svir and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84985993179&doi=10.1021%2facs.analchem.6b01454&partnerID=40&md5=c82be3566cca0a32bc9a47c3dd050059}, doi = {10.1021/acs.analchem.6b01454}, year = {2016}, date = {2016-01-01}, journal = {Analytical Chemistry}, volume = {88}, number = {17}, pages = {8535--8541}, abstract = {The individual electrochemical anodic responses of dopamine (DA), epinephrine (EP), and pyrocatechol (CT) were investigated at arrays of recessed gold disk-microelectrodes arrays (MEAs) covered by a gold plane electrode and compared to those of their binary mixture (CT and EP) when the top-plane electrode was operated as a bipolar electrode or as a collector. The interferent species (EP) displays a chemically irreversible wave over the same potential range as the chemically reversible ones of DA or CT. As expected, in the generator-collector (GC) mode, EP did not contribute to the redox cycling amplification that occurred only for DA or CT. Conversely, in the bipolar mode, the presence of EP drastically increased the bipolar redox cycling efficiency of DA and CT. This evidenced that the chemically irreversible oxidation of EP at the anodic poles of the top plane floating electrode provided additional electron fluxes that were used to more efficiently reduce the oxidized DA or CT species at the cathodic poles. This suggests an easy experimental strategy for enhancing the bipolar efficiency of MEAs up to reach a performance identical to that achieved when the same MEAs are operated in a GC mode. © 2016 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The individual electrochemical anodic responses of dopamine (DA), epinephrine (EP), and pyrocatechol (CT) were investigated at arrays of recessed gold disk-microelectrodes arrays (MEAs) covered by a gold plane electrode and compared to those of their binary mixture (CT and EP) when the top-plane electrode was operated as a bipolar electrode or as a collector. The interferent species (EP) displays a chemically irreversible wave over the same potential range as the chemically reversible ones of DA or CT. As expected, in the generator-collector (GC) mode, EP did not contribute to the redox cycling amplification that occurred only for DA or CT. Conversely, in the bipolar mode, the presence of EP drastically increased the bipolar redox cycling efficiency of DA and CT. This evidenced that the chemically irreversible oxidation of EP at the anodic poles of the top plane floating electrode provided additional electron fluxes that were used to more efficiently reduce the oxidized DA or CT species at the cathodic poles. This suggests an easy experimental strategy for enhancing the bipolar efficiency of MEAs up to reach a performance identical to that achieved when the same MEAs are operated in a GC mode. © 2016 American Chemical Society. |
2015 |
Development and Validation of an Analytical Model for Predicting Chronoamperometric Responses of Random Arrays of Micro- and Nanodisk Electrodes Article de journal O Sliusarenko; A Oleinick; I Svir; C Amatore ChemElectroChem, 2 (9), p. 1279–1291, 2015. @article{Sliusarenko:2015, title = {Development and Validation of an Analytical Model for Predicting Chronoamperometric Responses of Random Arrays of Micro- and Nanodisk Electrodes}, author = {O Sliusarenko and A Oleinick and I Svir and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84941552517&doi=10.1002%2fcelc.201500222&partnerID=40&md5=d8360b7129625ca10fd8b8fa40313e33}, doi = {10.1002/celc.201500222}, year = {2015}, date = {2015-01-01}, journal = {ChemElectroChem}, volume = {2}, number = {9}, pages = {1279--1291}, abstract = {Quantitative theoretical investigations based on a 3D Brownian motion approach established that our previous "cylindrical" approximation remains valid even for drastically irregular arrays. This result led us to propose a simple analytical equation that can be used to predict the chronoamperometric behavior of such commonly used irregular arrays, taking into account the statistical distributions of the Voronoi cells built around the disk electrodes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Quantitative theoretical investigations based on a 3D Brownian motion approach established that our previous "cylindrical" approximation remains valid even for drastically irregular arrays. This result led us to propose a simple analytical equation that can be used to predict the chronoamperometric behavior of such commonly used irregular arrays, taking into account the statistical distributions of the Voronoi cells built around the disk electrodes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
Validating a Central Approximation in Theories of Regular Electrode Electrochemical Arrays of Various Common Geometries Article de journal O Sliusarenko; A Oleinick; I Svir; C Amatore Electroanalysis, 27 (4), p. 980–991, 2015. @article{Sliusarenko:2015a, title = {Validating a Central Approximation in Theories of Regular Electrode Electrochemical Arrays of Various Common Geometries}, author = {O Sliusarenko and A Oleinick and I Svir and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84927797127&doi=10.1002%2felan.201400593&partnerID=40&md5=ae7d9406bcb4f24d2005d4b1cb0cb822}, doi = {10.1002/elan.201400593}, year = {2015}, date = {2015-01-01}, journal = {Electroanalysis}, volume = {27}, number = {4}, pages = {980--991}, abstract = {Thirty years ago one of us introduced a central approximation according to which the regular arrays behaviors could be estimated based on those of arrays of cylindrical unit cells with the same relative surface area of their central disks for the insulating section. This work examines and validates this approximation on the basis of 3D-simulations of Brownian particles motion for inlaid or recessed electroactive disks as well as for protruding cylindrical electrodes. The approximation is perfectly adequate for predicting the behavior of realistic experimental arrays and is valid within a few percent even in extreme situations when adjacent electroactive sections are almost touching. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Thirty years ago one of us introduced a central approximation according to which the regular arrays behaviors could be estimated based on those of arrays of cylindrical unit cells with the same relative surface area of their central disks for the insulating section. This work examines and validates this approximation on the basis of 3D-simulations of Brownian particles motion for inlaid or recessed electroactive disks as well as for protruding cylindrical electrodes. The approximation is perfectly adequate for predicting the behavior of realistic experimental arrays and is valid within a few percent even in extreme situations when adjacent electroactive sections are almost touching. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
Strong and Unexpected Effects of Diffusion Rates on the Generation of Electrochemiluminescence by Amine/Transition-Metal(II) Systems Article de journal I Svir; A Oleinick; O V Klymenko; C Amatore ChemElectroChem, 2 (6), p. 811–818, 2015. @article{Svir:2015, title = {Strong and Unexpected Effects of Diffusion Rates on the Generation of Electrochemiluminescence by Amine/Transition-Metal(II) Systems}, author = {I Svir and A Oleinick and O V Klymenko and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938578499&doi=10.1002%2fcelc.201402460&partnerID=40&md5=4e9da5aa6563d84da4d184dcc3eb9027}, doi = {10.1002/celc.201402460}, year = {2015}, date = {2015-01-01}, journal = {ChemElectroChem}, volume = {2}, number = {6}, pages = {811--818}, abstract = {This theoretical work examines some basic and overlooked concepts that sustain the efficiency of electrochemiluminescence (ECL) generated by co-reactant systems such as the, nowadays classical, alkyl amine/transition metal(II) complex systems. Changes in the ECL intensities emitted by these systems are much more dependent on the relative diffusivities of the two co-reactants than on the range of thermodynamic and kinetic rate constants that are possible to explore and vary. In particular, decreasing the diffusion coefficients of the metal complexes species (e.g. by adequate redox or photochemically inert large substituents) relative to that of the amine co-reactant leads to a great enhancement in the ECL intensity of the first ECL wave, namely, that observed at the level of the amine oxidation peak. Though investigated by using simulations based on the thermodynamic and kinetic constants of the most common tri-n-propylamine/Ru(bpy)textlessinftextgreater3textless/inftextgreater2+ system (bpy=2,2'-bipyridine), the conclusions of this work are more general. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This theoretical work examines some basic and overlooked concepts that sustain the efficiency of electrochemiluminescence (ECL) generated by co-reactant systems such as the, nowadays classical, alkyl amine/transition metal(II) complex systems. Changes in the ECL intensities emitted by these systems are much more dependent on the relative diffusivities of the two co-reactants than on the range of thermodynamic and kinetic rate constants that are possible to explore and vary. In particular, decreasing the diffusion coefficients of the metal complexes species (e.g. by adequate redox or photochemically inert large substituents) relative to that of the amine co-reactant leads to a great enhancement in the ECL intensity of the first ECL wave, namely, that observed at the level of the amine oxidation peak. Though investigated by using simulations based on the thermodynamic and kinetic constants of the most common tri-n-propylamine/Ru(bpy)textlessinftextgreater3textless/inftextgreater2+ system (bpy=2,2'-bipyridine), the conclusions of this work are more general. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
Electrochemical Measurements of Optogenetically Stimulated Quantal Amine Release from Single Nerve Cell Varicosities in Drosophila Larvae Article de journal S Majdi; E C Berglund; J Dunevall; A I Oleinick; C Amatore; D E Krantz; A G Ewing Angewandte Chemie - International Edition, 54 (46), p. 13609–13612, 2015. @article{Majdi:2015, title = {Electrochemical Measurements of Optogenetically Stimulated Quantal Amine Release from Single Nerve Cell Varicosities in Drosophila Larvae}, author = {S Majdi and E C Berglund and J Dunevall and A I Oleinick and C Amatore and D E Krantz and A G Ewing}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946127651&doi=10.1002%2fanie.201506743&partnerID=40&md5=cb715585c6bace09f941f57789c1dd6c}, doi = {10.1002/anie.201506743}, year = {2015}, date = {2015-01-01}, journal = {Angewandte Chemie - International Edition}, volume = {54}, number = {46}, pages = {13609--13612}, abstract = {The nerve terminals found in the body wall of Drosophila melanogaster larvae are readily accessible to experimental manipulation. We used the light-activated ion channel, channelrhodopsin-2, which is expressed by genetic manipulation in Type II varicosities to study octopamine release in Drosophila. We report the development of a method to measure neurotransmitter release from exocytosis events at individual varicosities in the Drosophila larval system by amperometry. A microelectrode was placed in a region of the muscle containing a varicosity and held at a potential sufficient to oxidize octopamine and the terminal stimulated by blue light. Optical stimulation of Type II boutons evokes exocytosis of octopamine, which is detected through oxidization at the electrode surface. We observe 22700±4200 molecules of octopamine released per vesicle. This system provides a genetically accessible platform to study the regulation of amine release at an intact synapse. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The nerve terminals found in the body wall of Drosophila melanogaster larvae are readily accessible to experimental manipulation. We used the light-activated ion channel, channelrhodopsin-2, which is expressed by genetic manipulation in Type II varicosities to study octopamine release in Drosophila. We report the development of a method to measure neurotransmitter release from exocytosis events at individual varicosities in the Drosophila larval system by amperometry. A microelectrode was placed in a region of the muscle containing a varicosity and held at a potential sufficient to oxidize octopamine and the terminal stimulated by blue light. Optical stimulation of Type II boutons evokes exocytosis of octopamine, which is detected through oxidization at the electrode surface. We observe 22700±4200 molecules of octopamine released per vesicle. This system provides a genetically accessible platform to study the regulation of amine release at an intact synapse. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
Real-time Monitoring of Discrete Synaptic Release Events and Excitatory Potentials within Self-reconstructed Neuromuscular Junctions Article de journal Y -T Li; S -H Zhang; X -Y Wang; X -W Zhang; A I Oleinick; I Svir; C Amatore; W -H Huang Angewandte Chemie - International Edition, 54 (32), p. 9313–9318, 2015. @article{Li:2015, title = {Real-time Monitoring of Discrete Synaptic Release Events and Excitatory Potentials within Self-reconstructed Neuromuscular Junctions}, author = {Y -T Li and S -H Zhang and X -Y Wang and X -W Zhang and A I Oleinick and I Svir and C Amatore and W -H Huang}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84938216019&doi=10.1002%2fanie.201503801&partnerID=40&md5=348fbe3d4634221601838edbb4358c46}, doi = {10.1002/anie.201503801}, year = {2015}, date = {2015-01-01}, journal = {Angewandte Chemie - International Edition}, volume = {54}, number = {32}, pages = {9313--9318}, abstract = {Chemical synaptic transmission is central to the brain functions. In this regard, real-time monitoring of chemical synaptic transmission during neuronal communication remains a great challenge. In this work, in vivo-like oriented neural networks between superior cervical ganglion (SCG) neurons and their effector smooth muscle cells (SMC) were assembled in a microfluidic device. This allowed amperometric detection of individual neurotransmitter release events inside functional SCG-SMC synapse with carbon fiber nanoelectrodes as well as recording of postsynaptic potential using glass nanopipette electrodes. The high vesicular release activities essentially involved complex events arising from flickering fusion pores as quantitatively established based on simulations. This work allowed for the first time monitoring in situ chemical synaptic transmission under conditions close to those found in vivo, which may yield important and new insights into the nature of neuronal communications. A microfluidic chip was developed taking advantage of a carbon fiber nanoelectrode (CFNE) and a robust platform for real-time monitoring of single intra-synaptic vesicular release events and of the subsequent generation of postsynaptic membrane excitatory potential (EJP) signals. By using this chip, the first in situ measurements of synaptic transmission in neuromuscular mimics are reported. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Chemical synaptic transmission is central to the brain functions. In this regard, real-time monitoring of chemical synaptic transmission during neuronal communication remains a great challenge. In this work, in vivo-like oriented neural networks between superior cervical ganglion (SCG) neurons and their effector smooth muscle cells (SMC) were assembled in a microfluidic device. This allowed amperometric detection of individual neurotransmitter release events inside functional SCG-SMC synapse with carbon fiber nanoelectrodes as well as recording of postsynaptic potential using glass nanopipette electrodes. The high vesicular release activities essentially involved complex events arising from flickering fusion pores as quantitatively established based on simulations. This work allowed for the first time monitoring in situ chemical synaptic transmission under conditions close to those found in vivo, which may yield important and new insights into the nature of neuronal communications. A microfluidic chip was developed taking advantage of a carbon fiber nanoelectrode (CFNE) and a robust platform for real-time monitoring of single intra-synaptic vesicular release events and of the subsequent generation of postsynaptic membrane excitatory potential (EJP) signals. By using this chip, the first in situ measurements of synaptic transmission in neuromuscular mimics are reported. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
2014 |
A new strategy for eliminating interference from EC′ mechanism during analytical measurements based on plane-band-recessed microdisk array electrodes Article de journal S Pang; J Yan; F Zhu; D He; B Mao; A Oleinick; I Svir; C Amatore Electrochemistry Communications, 38 , p. 61–64, 2014. @article{Pang:2014, title = {A new strategy for eliminating interference from EC′ mechanism during analytical measurements based on plane-band-recessed microdisk array electrodes}, author = {S Pang and J Yan and F Zhu and D He and B Mao and A Oleinick and I Svir and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888124955&doi=10.1016%2fj.elecom.2013.10.029&partnerID=40&md5=c22f1b5febcf14d50345ccb032df5ea6}, doi = {10.1016/j.elecom.2013.10.029}, year = {2014}, date = {2014-01-01}, journal = {Electrochemistry Communications}, volume = {38}, pages = {61--64}, abstract = {A new type of three-electrode generator-collector sensor is described for the selective detection of any target analyte whose CV is chemically reversible in the presence of any interferent whose CV is chemically irreversible. The device consists of a layer of metallic material (Au in this work) poked by an array of cylindrical pores containing a ring-band electrode (Au in this work) placed in their middle and a disk electrode at their bottom (Au in this work). Operating the array of recessed disk electrodes to monitor the product of the stable analyte electronation while the top plane and the ring-band electrodes are poised at a potential located on the analyte and on the interferent waves allows suppressing entirely any contamination of the analyte concentration measurement by direct or indirect (EC′) involvement of the interferent. The efficiency of such devices was successfully demonstrated based on the detection of dopamine in the presence of ascorbic acid in PBS electrolyte. © 2013 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A new type of three-electrode generator-collector sensor is described for the selective detection of any target analyte whose CV is chemically reversible in the presence of any interferent whose CV is chemically irreversible. The device consists of a layer of metallic material (Au in this work) poked by an array of cylindrical pores containing a ring-band electrode (Au in this work) placed in their middle and a disk electrode at their bottom (Au in this work). Operating the array of recessed disk electrodes to monitor the product of the stable analyte electronation while the top plane and the ring-band electrodes are poised at a potential located on the analyte and on the interferent waves allows suppressing entirely any contamination of the analyte concentration measurement by direct or indirect (EC′) involvement of the interferent. The efficiency of such devices was successfully demonstrated based on the detection of dopamine in the presence of ascorbic acid in PBS electrolyte. © 2013 Elsevier Ltd. All rights reserved. |
Strategy for increasing the electrode density of microelectrode arrays by utilizing bipolar behavior of a metallic film Article de journal F Zhu; J Yan; S Pang; Y Zhou; B Mao; A Oleinick; I Svir; C Amatore Analytical Chemistry, 86 (6), p. 3138–3145, 2014. @article{Zhu:2014, title = {Strategy for increasing the electrode density of microelectrode arrays by utilizing bipolar behavior of a metallic film}, author = {F Zhu and J Yan and S Pang and Y Zhou and B Mao and A Oleinick and I Svir and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896510508&doi=10.1021%2fac404202p&partnerID=40&md5=d9a159777a8699adbfe40cf130becd88}, doi = {10.1021/ac404202p}, year = {2014}, date = {2014-01-01}, journal = {Analytical Chemistry}, volume = {86}, number = {6}, pages = {3138--3145}, abstract = {Recessed microelectrode arrays and plane-recessed microelectrode arrays (MEAs) with different center-to-center distances are designed and fabricated using lithographic technology. By comparing electrochemical behavior of plane-recessed MEAs with that of recessed MEAs, bipolar phenomenon of the metallic plane film is revealed. Redox cycling can occur when the top plane electrode was floating; that is, the bipolar behavior of the unbiased top plane electrode may perform locally as a collector and enlarge the concentration gradient of Ru(NH3)6Cl3 and thus promote an apparent generator/collector electrochemical response of the microdisk electrode in the MEAs configuration. By utilizing the bipolar behavior, the center-to-center distance of MEAs required for achieving steady-state current could decrease without favoring at the same time the overlapping of diffusion layers of microelectrodes, and thus, the electrode density of MEAs can be increased. Therefore, the bipolar behavior of the metallic film can increase both the current response of an individual microdisk and the electrode density of microdisks without losing the characteristics of a microelectrode. By just fabricating a thin layer of metallic film on the plane and leaving it floating without potential control, recessed MEAs used in this work can achieve the increase of detection sensitivity by more than 1 order of magnitude. © 2014 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Recessed microelectrode arrays and plane-recessed microelectrode arrays (MEAs) with different center-to-center distances are designed and fabricated using lithographic technology. By comparing electrochemical behavior of plane-recessed MEAs with that of recessed MEAs, bipolar phenomenon of the metallic plane film is revealed. Redox cycling can occur when the top plane electrode was floating; that is, the bipolar behavior of the unbiased top plane electrode may perform locally as a collector and enlarge the concentration gradient of Ru(NH3)6Cl3 and thus promote an apparent generator/collector electrochemical response of the microdisk electrode in the MEAs configuration. By utilizing the bipolar behavior, the center-to-center distance of MEAs required for achieving steady-state current could decrease without favoring at the same time the overlapping of diffusion layers of microelectrodes, and thus, the electrode density of MEAs can be increased. Therefore, the bipolar behavior of the metallic film can increase both the current response of an individual microdisk and the electrode density of microdisks without losing the characteristics of a microelectrode. By just fabricating a thin layer of metallic film on the plane and leaving it floating without potential control, recessed MEAs used in this work can achieve the increase of detection sensitivity by more than 1 order of magnitude. © 2014 American Chemical Society. |
2013 |
A Oleinick; F Zhu; J Yan; B Mao; I Svir; C Amatore ChemPhysChem, 14 (9), p. 1887–1898, 2013. @article{Oleinick:2013, title = {Theoretical investigation of generator-collector microwell arrays for improving electroanalytical selectivity: Application to selective dopamine detection in the presence of ascorbic acid}, author = {A Oleinick and F Zhu and J Yan and B Mao and I Svir and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84879173085&doi=10.1002%2fcphc.201300134&partnerID=40&md5=a68c928b861bd749f59450f45d78d109}, doi = {10.1002/cphc.201300134}, year = {2013}, date = {2013-01-01}, journal = {ChemPhysChem}, volume = {14}, number = {9}, pages = {1887--1898}, abstract = {Recessed generator-collector assemblies consisting of an array of recessed disks (generator electrodes) with a gold layer (collector electrode) deposited over the top-plane insulator reportedly allow increased selectivity and sensitivity during electrochemical detection of dopamine (DA) in the presence of ascorbic acid (AA), a situation which is frequently encountered. In sensor design, the potential of the disk electrodes is set to the wave plateau of DA, whereas the plane electrode is biased at the irreversible wave plateau of AA before the onset of the DA oxidation wave. Thus, AA is scavenged but DA is allowed to enter the nanocavities to be oxidized at the disk electrodes, and its signal is further amplified by redox cycling between disk and plane electrodes. Several different theoretical approaches are elaborated herein to analyze the behavior of the system, and their conclusions are successfully tested by experiments. This reveals the crucial role of the plane-electrode area which screens access to the recessed disks (i.e. acts as a diffusional Faraday cage) and simultaneously contributes to amplification of the analyte signal through positive feedback, as occurs in interdigitated arrays and scanning electrochemical microscopy. Simulations also allow for the evaluation of the benefits of different geometries inspired by the above design and different operating modes for increasing the sensor performance. Well separated: A microwell array integrating collector-generator amplification into a diffusional faradaic cage virtually eliminates irreversible redox interferences, for example, in dopamine (DA) detection in the presence of ascorbic acid (AA). Thus, AA is scavenged but DA enters the nanocavities for oxidation at the disk electrodes, and its signal is further amplified by redox cycling (see picture). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Recessed generator-collector assemblies consisting of an array of recessed disks (generator electrodes) with a gold layer (collector electrode) deposited over the top-plane insulator reportedly allow increased selectivity and sensitivity during electrochemical detection of dopamine (DA) in the presence of ascorbic acid (AA), a situation which is frequently encountered. In sensor design, the potential of the disk electrodes is set to the wave plateau of DA, whereas the plane electrode is biased at the irreversible wave plateau of AA before the onset of the DA oxidation wave. Thus, AA is scavenged but DA is allowed to enter the nanocavities to be oxidized at the disk electrodes, and its signal is further amplified by redox cycling between disk and plane electrodes. Several different theoretical approaches are elaborated herein to analyze the behavior of the system, and their conclusions are successfully tested by experiments. This reveals the crucial role of the plane-electrode area which screens access to the recessed disks (i.e. acts as a diffusional Faraday cage) and simultaneously contributes to amplification of the analyte signal through positive feedback, as occurs in interdigitated arrays and scanning electrochemical microscopy. Simulations also allow for the evaluation of the benefits of different geometries inspired by the above design and different operating modes for increasing the sensor performance. Well separated: A microwell array integrating collector-generator amplification into a diffusional faradaic cage virtually eliminates irreversible redox interferences, for example, in dopamine (DA) detection in the presence of ascorbic acid (AA). Thus, AA is scavenged but DA enters the nanocavities for oxidation at the disk electrodes, and its signal is further amplified by redox cycling (see picture). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
2012 |
A novel approach to the simulation of electrochemical mechanisms involving acute reaction fronts at disk and band microelectrodes Article de journal O V Klymenko; I Svir; A Oleinick; C Amatore ChemPhysChem, 13 (3), p. 845–859, 2012. @article{Klymenko:2012, title = {A novel approach to the simulation of electrochemical mechanisms involving acute reaction fronts at disk and band microelectrodes}, author = {O V Klymenko and I Svir and A Oleinick and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84857318997&doi=10.1002%2fcphc.201100825&partnerID=40&md5=0b61e5230fe9d4e5f5c5b86c2107a419}, doi = {10.1002/cphc.201100825}, year = {2012}, date = {2012-01-01}, journal = {ChemPhysChem}, volume = {13}, number = {3}, pages = {845--859}, abstract = {A new simulation algorithm is presented for describing the dynamics of diffusion reactions at the most common microelectrode 1D (planar, cylindrical, spherical) and 2D geometries (band, disk) for electrochemical mechanisms of any complexity and involving fast homogeneous reactions of any kind. A series of typical electrochemical mechanisms that create the most severe simulation difficulties is used to establish the exceptional performance and accuracy of this algorithm, which stem from the combination of (quasi)conformal transformation of space and a new method for auto-adaptive grid compression. Complex electrochemical mechanisms involving any sequence of fast homogeneous kinetics at common microelectrodes can now be simulated in a completely automatic and transparent manner using a combination of (quasi)conformal mappings and auto-adaptive computational grids. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A new simulation algorithm is presented for describing the dynamics of diffusion reactions at the most common microelectrode 1D (planar, cylindrical, spherical) and 2D geometries (band, disk) for electrochemical mechanisms of any complexity and involving fast homogeneous reactions of any kind. A series of typical electrochemical mechanisms that create the most severe simulation difficulties is used to establish the exceptional performance and accuracy of this algorithm, which stem from the combination of (quasi)conformal transformation of space and a new method for auto-adaptive grid compression. Complex electrochemical mechanisms involving any sequence of fast homogeneous kinetics at common microelectrodes can now be simulated in a completely automatic and transparent manner using a combination of (quasi)conformal mappings and auto-adaptive computational grids. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
A new strategy for simulation of electrochemical mechanisms involving acute reaction fronts in solution under spherical or cylindrical diffusion Article de journal O V Klymenko; A I Oleinick; I Svir; C Amatore Russian Journal of Electrochemistry, 48 (6), p. 593–599, 2012. @article{Klymenko:2012a, title = {A new strategy for simulation of electrochemical mechanisms involving acute reaction fronts in solution under spherical or cylindrical diffusion}, author = {O V Klymenko and A I Oleinick and I Svir and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84864628559&doi=10.1134%2fS1023193512060055&partnerID=40&md5=5fe12c64a025043ca66f57cefa3dcaf0}, doi = {10.1134/S1023193512060055}, year = {2012}, date = {2012-01-01}, journal = {Russian Journal of Electrochemistry}, volume = {48}, number = {6}, pages = {593--599}, abstract = {In this paper we present a combined simulation approach for solving complex electrochemical kinetic problems at (hemi)spherical and (hemi)cylindrical electrodes based on the simultaneous application of analytical conformal coordinate transformations to accurately treat the diffusional transport and adaptive grid compression to locally increase the accuracy of the approximation of acute reaction fronts. This strategy is shown to be very efficient and leads to extremely accurate results both for steady state and transient situations and is equally powerful for both pure diffusion and that complicated by severe kinetic distortions. © Pleiades Publishing, Ltd., 2012.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this paper we present a combined simulation approach for solving complex electrochemical kinetic problems at (hemi)spherical and (hemi)cylindrical electrodes based on the simultaneous application of analytical conformal coordinate transformations to accurately treat the diffusional transport and adaptive grid compression to locally increase the accuracy of the approximation of acute reaction fronts. This strategy is shown to be very efficient and leads to extremely accurate results both for steady state and transient situations and is equally powerful for both pure diffusion and that complicated by severe kinetic distortions. © Pleiades Publishing, Ltd., 2012. |
2011 |
Simple and clear evidence for positive feedback limitation by bipolar behavior during scanning electrochemical microscopy of unbiased conductors Article de journal A I Oleinick; D Battistel; S Daniele; I Svir; C Amatore Analytical Chemistry, 83 (12), p. 4887–4893, 2011. @article{Oleinick:2011, title = {Simple and clear evidence for positive feedback limitation by bipolar behavior during scanning electrochemical microscopy of unbiased conductors}, author = {A I Oleinick and D Battistel and S Daniele and I Svir and C Amatore}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-79959187642&doi=10.1021%2fac2006075&partnerID=40&md5=0d12946b4ca22acd69bcd2c6ebd46df6}, doi = {10.1021/ac2006075}, year = {2011}, date = {2011-01-01}, journal = {Analytical Chemistry}, volume = {83}, number = {12}, pages = {4887--4893}, abstract = {On the basis of an experimentally validated simple theoretical model, it is demonstrated unambiguously that when an unbiased conductor is probed by a scanning electrochemical tip (scanning electrochemical microscopy, SECM), it performs as a bipolar electrode. Though already envisioned in most recent SECM theories, this phenomenon is generally overlooked in SECM experimental investigations. However, as is shown here, this may alter significantly positive feedback measurements when the probed conductor is not much larger than the tip. © 2011 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } On the basis of an experimentally validated simple theoretical model, it is demonstrated unambiguously that when an unbiased conductor is probed by a scanning electrochemical tip (scanning electrochemical microscopy, SECM), it performs as a bipolar electrode. Though already envisioned in most recent SECM theories, this phenomenon is generally overlooked in SECM experimental investigations. However, as is shown here, this may alter significantly positive feedback measurements when the probed conductor is not much larger than the tip. © 2011 American Chemical Society. |
2010 |
Reconstruction of aperture functions during full fusion in vesicular exocytosis of neurotransmitters Article de journal C Amatore; A I Oleinick; I Svir ChemPhysChem, 11 (1), p. 159–174, 2010. @article{Amatore:2010d, title = {Reconstruction of aperture functions during full fusion in vesicular exocytosis of neurotransmitters}, author = {C Amatore and A I Oleinick and I Svir}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-77949537137&doi=10.1002%2fcphc.200900647&partnerID=40&md5=94b64fc6ae41e0ef2488cc156e47f473}, doi = {10.1002/cphc.200900647}, year = {2010}, date = {2010-01-01}, journal = {ChemPhysChem}, volume = {11}, number = {1}, pages = {159--174}, abstract = {Individual vesicular exocytosis of adrenaline by dense core vesicles in chromaffin cells is considered here as a paradigm of many situations encountered in biology, nanosciences and drug delivery in which a spherical container releases in the external environment through gradual uncovering of its surface. A procedure for extracting the aperture (opening) function of a biological vesicle fusing with a cell membrane from the released molecular flux of neurotransmitter as monitored by amperometry has been devised based on semi-analytical expressions derived in a former work [C. Amatore, A. I. Oleinick, I. Svir, ChemPhysChem 2009, 10, DOI: 10.1002/cphc.200900646]. This precise analysis shows that in the absence of direct information about the radius of the vesicle or about the concentration of the adrenaline cation stored by the vesicle matrix, current spikes do not contain enough information to determine the maximum aperture angle. Yet, a statistical analysis establishes that this maximum aperture angle is most probably less than a few tens of degrees, which suggests that full fusion is a very improbable event. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Individual vesicular exocytosis of adrenaline by dense core vesicles in chromaffin cells is considered here as a paradigm of many situations encountered in biology, nanosciences and drug delivery in which a spherical container releases in the external environment through gradual uncovering of its surface. A procedure for extracting the aperture (opening) function of a biological vesicle fusing with a cell membrane from the released molecular flux of neurotransmitter as monitored by amperometry has been devised based on semi-analytical expressions derived in a former work [C. Amatore, A. I. Oleinick, I. Svir, ChemPhysChem 2009, 10, DOI: 10.1002/cphc.200900646]. This precise analysis shows that in the absence of direct information about the radius of the vesicle or about the concentration of the adrenaline cation stored by the vesicle matrix, current spikes do not contain enough information to determine the maximum aperture angle. Yet, a statistical analysis establishes that this maximum aperture angle is most probably less than a few tens of degrees, which suggests that full fusion is a very improbable event. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. |
Diffusion from within a spherical body with partially blocked surface: Diffusion through a constant surface area Article de journal C Amatore; A I Oleinick; I Svir ChemPhysChem, 11 (1), p. 149–158, 2010. @article{Amatore:2010a, title = {Diffusion from within a spherical body with partially blocked surface: Diffusion through a constant surface area}, author = {C Amatore and A I Oleinick and I Svir}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-78349270477&doi=10.1002%2fcphc.200900646&partnerID=40&md5=704b6231b809b58be2396392425709c4}, doi = {10.1002/cphc.200900646}, year = {2010}, date = {2010-01-01}, journal = {ChemPhysChem}, volume = {11}, number = {1}, pages = {149--158}, abstract = {Diffusion from spherical bodies has been a subject of interest since the earliest times of modern sciences and a few equivalent analytical formulations of the problem are taught in engineering textbooks dealing with cooling rates of hot spheres. However, all these former studies assume that the diffusing material is transferable to/from the surrounding space through the whole surface of the spherical body. Conversely, the development of nanoscience and the improved knowledge of microscopic biological events have evidenced that diffusion from spherical bodies is a ubiquitous problem. It often occurs in situations where the nanosphere surfaces are not isotropic and partly impermeable to diffusing materials. This work elaborates on this issue and theoretically establishes that-with some specific allowance-the basic analytical equation of diffusion from/to fully accessible spherical bodies may be used. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Diffusion from spherical bodies has been a subject of interest since the earliest times of modern sciences and a few equivalent analytical formulations of the problem are taught in engineering textbooks dealing with cooling rates of hot spheres. However, all these former studies assume that the diffusing material is transferable to/from the surrounding space through the whole surface of the spherical body. Conversely, the development of nanoscience and the improved knowledge of microscopic biological events have evidenced that diffusion from spherical bodies is a ubiquitous problem. It often occurs in situations where the nanosphere surfaces are not isotropic and partly impermeable to diffusing materials. This work elaborates on this issue and theoretically establishes that-with some specific allowance-the basic analytical equation of diffusion from/to fully accessible spherical bodies may be used. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. |
2009 |
Diffusion with moving boundary on spherical surfaces Article de journal C Amatore; O V Klymenko; A I Oleinick; I Svir ChemPhysChem, 10 (9-10), p. 1593–1602, 2009. @article{Amatore:2009, title = {Diffusion with moving boundary on spherical surfaces}, author = {C Amatore and O V Klymenko and A I Oleinick and I Svir}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-67650045792&doi=10.1002%2fcphc.200900169&partnerID=40&md5=916b9e3fb2ae872caa831691c303ac46}, doi = {10.1002/cphc.200900169}, year = {2009}, date = {2009-01-01}, journal = {ChemPhysChem}, volume = {10}, number = {9-10}, pages = {1593--1602}, abstract = {In this work, we illustrate two approaches to the simulation of surface diffusion over a sphere coupled with the formation of a cluster by reactive particles as a paradigm of a wide variety of problems occurring in many areas of nanosciences and biology. The problem is treated using a Brownian motion approach and a numerical solution of the corresponding continuous Fick's laws of diffusion. While being computationally more expensive, the Brownian motion approach allows one to consider a wider range of situations, particularly those corresponding to relatively high concentrations of diffusing particles and the ensuing problem of particle overlap when they are ascribed finite sizes. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this work, we illustrate two approaches to the simulation of surface diffusion over a sphere coupled with the formation of a cluster by reactive particles as a paradigm of a wide variety of problems occurring in many areas of nanosciences and biology. The problem is treated using a Brownian motion approach and a numerical solution of the corresponding continuous Fick's laws of diffusion. While being computationally more expensive, the Brownian motion approach allows one to consider a wider range of situations, particularly those corresponding to relatively high concentrations of diffusing particles and the ensuing problem of particle overlap when they are ascribed finite sizes. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. |
Numerical simulation of diffusion processes at recessed disk microelectrode arrays using the quasi-conformal mapping approach Article de journal C Amatore; A I Oleinick; I Svir Analytical Chemistry, 81 (11), p. 4397–4405, 2009. @article{Amatore:2009f, title = {Numerical simulation of diffusion processes at recessed disk microelectrode arrays using the quasi-conformal mapping approach}, author = {C Amatore and A I Oleinick and I Svir}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-66349103067&doi=10.1021%2fac9003419&partnerID=40&md5=5aa91bf9afc00d89fb8933d2bd6efb74}, doi = {10.1021/ac9003419}, year = {2009}, date = {2009-01-01}, journal = {Analytical Chemistry}, volume = {81}, number = {11}, pages = {4397--4405}, abstract = {In this work, we present a theoretical analysis of diffusion processes at arrays of recessed microelectrodes and evaluate the dependence of these processes on the main geometrical parameters (distance between electrodes in the array and slope of side walls of conical recesses) of this complex system. To allow for faster computation time and excellent accuracy, numerical simulations were performed upon transforming the real space allowed for diffusion using a quasi-conformal mapping introduced for this array geometry in our previous work (Amatore, C.; Oleinick, A. I.; Svir, I. J. Electroanal. Chem. 2006, 597, 77-85). The applied quasi-conformal mapping is perfectly suited to the considered microelectrode array geometry and ensures that the abrupt change of boundary conditions reflecting the contorted geometries of the considered microelectrode array are treated efficiently and precisely in the simulations. © 2009 American Chemical Society.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this work, we present a theoretical analysis of diffusion processes at arrays of recessed microelectrodes and evaluate the dependence of these processes on the main geometrical parameters (distance between electrodes in the array and slope of side walls of conical recesses) of this complex system. To allow for faster computation time and excellent accuracy, numerical simulations were performed upon transforming the real space allowed for diffusion using a quasi-conformal mapping introduced for this array geometry in our previous work (Amatore, C.; Oleinick, A. I.; Svir, I. J. Electroanal. Chem. 2006, 597, 77-85). The applied quasi-conformal mapping is perfectly suited to the considered microelectrode array geometry and ensures that the abrupt change of boundary conditions reflecting the contorted geometries of the considered microelectrode array are treated efficiently and precisely in the simulations. © 2009 American Chemical Society. |