Carbon Microelectrodes Research Articles

Experimental strategies for continuous measurements of I-t transients of a silver single nucleus on carbon microelectrodes

Potential step and in situ atomic force microscopy measurements were employed to study the nucleation and subsequent behaviour of a silver single nucleus on carbon microelectrodes. It was shown that the preceding electrodeposition process on the carbon microelectrode strongly affects the subsequent nucleation and growth behaviour. A method of destroying or avoiding this historic effect of the substrate was developed. It provides a new way of performing a large number of electrochemical measurements without mechanical polishing and manual interference, and therefore facilitates further more detailed studies of a system which requires continuous and automatic I-t transient measurements of statistical meaning. It was demonstrated that secure and automatic statistical measurements of I-t transients could be fulfilled utilising the method.

Interdigitated microelectrode arrays based on sputtered carbon thin-films

Thin-film carbon microelectrodes deposited by RF sputtering onto a Si/Si 3N 4 substrate are presented. By optimizing the deposition parameters, films showing low resistivity (10 −3 Ω cm) and good adhesion are achieved. Physical, spectroscopic and electrochemical characterizations are carried out. The electrocatalytical properties of the carbon thin-films are assessed with and without surface activation. Successful patterning in O 2 plasma is demonstrated by the fabrication of interdigitated microelectrode arrays featuring a resolution of 2 μm. The analytical performance of the interdigitated microelectrodes is illustrated by the detection of dopamine over a concentration range of 50 nM to 100 μM.

Fabrication and Characterization of Sputtered-Carbon Microelectrode Arrays

This paper describes a robust and reliable process for fabricating a novel sputter-deposited, thin-film carbon microelectrode array using standard integrated circuit technologies and silicon micromachining. Sputter-deposited carbon films were investigated as potential candidates for microelectrode materials. The surface properties and cross section of the microelectrode arrays were studied by atomic force microscopy and scanning electron microscopy, respectively. Electrical site impedance, crosstalk, and lifetime (dielectric integrity) of microelectrodes in the array were characterized. Electrochemical response of the microelectrodes to hexaammineruthenium(III) chloride and dopamine were investigated by fast-scan cyclic voltammetry and high-speed, computer-based chronoamperometry; results show that thin-film carbon microelectrodes are well-behaved electrochemically. The thin carbon films offer extremely good electrical, mechanical, and chemical properties and thus qualify as viable candidates for various electroanalytical applications, particularly acute neurophysiological studies.

Cyclic voltammetry with harmonic lock‐in detection: Applications to flow streams

AbstractThe second harmonic frequency is monitored using a conventional lock‐in amplifier in a continuous scan cyclic voltammetric experiment. The background charging current is predominantly composed of odd harmonic frequencies, while the analyte Faradaic signal is composed of both odd and even harmonic frequencies. By ‘locking‐in’ on the second harmonic frequency one can isolate the Faradaic current from the charging current in the frequency domain. Model compounds (hexaammineruthenium(III) chloride, ferrocene) at carbon and gold microelectrodes as well as carbohydrates at copper microelectrodes were examined in flow injection analysis experiments. Limits of detection an order of magnitude lower than DC amperometry were observed.

Electrodeposition study on ultramicroelectrodes. Part 2. Different growth modes in Ag crystallization

The influence of the electrochemical treatment of the electrode, the supporting electrolyte concentration and the applied potential, on the formation of current steps as well as on the growth patterns was studied for silver electrodeposition on carbon microelectrodes. The results are compared with those obtained previously on platinum. The most interesting result is the “two-dimensional” dense branching structure with radial symmetry which was obtained for the first time in silver electrodeposits in a conventional cell.

Modeling Lithium Intercalation of Single‐Fiber Carbon Microelectrodes

To clarify the electrochemical processes governing the performance of lithiated carbon electrodes and obtain appropriate physicochemical properties, experiments conducted with a single‐fiber carbon microelectrode (3.5 μm radius, 1 cm length) are mathematically simulated. Equilibrium‐potential data are used to determine the activity coefficient of the lithium intercalate and associated host sites. Transport within the carbon fiber is influenced significantly by activity‐coefficient variations; the use of the guest chemical‐potential gradient as the driving force for transport phenomena is shown to yield constant physicochemical properties that are independent of the degree of intercalation. The theoretical calculations display good agreement with several different experimental data sets. The diffusion coefficient of lithium in partially graphitic carbon is obtained along with rate constants (i.e., the exchange current density) associated with the electrochemical reaction that takes place on the fiber surface.

Indirect Detection of Alkaline Earth Ions by the Voltammetric Response of Ferricyanide Anion at a Glassy Carbon Electrode Anodized in 1-Octanol.

The suppressed voltammetric respones of Fe(CN)3-6 at a glassy carbon (GC) electrode anodized in 1-octanol is restored by addition of alkaline earth ions and this can be applied to the detection of such cations. A good dependence of the cathodic currents of Fe(CN)3-6 at a 1-octanol-modified GC electrode on the concentration of each cation (Ca2+, Mg2+, Sr2+. Ba2+) is obtained over the range 10 μM-1 mM. The slight increase in enhanced voltammetric response of Fe(CN)3-6 in the presence of Ca2+ following added MeOH ruled out an ion-extraction mechanism for the observed phenomena. The effects of Ca2+ upon the voltammetric behavoir of Fe(CN)4-6 and IrCl2-6 as well as Fe/(CN)3-6 at a 1-octanol-modified GC electrode were compared with those previously reported at a carbon microelectrode, suggesting that the suppression of the cathodic reaction of Fe(CN)3-6 and its elimination by the addition of alkaline earth ions are brought about through transformation of a macroelectrode into a pseudo-microelectrode by anodization in 1-octanol. This is strongly supported by the fact that similar phenomena occur at other chemically modified electrodes, providing that modification is controlled to give an effective surface area corresponding to that of a pseudo-microelectrode.

A potential-pulse interference method for studies of the nucleation of a single silver centre on carbon microelectrodes

A potential-pulse interference method has been developed for detailed studies of the nucleation at a single nucleus. Following a potential step from a positive overpotential to a sufficiently negative overpotential at which nucleation takes place, a single reverse pulse or repetitive potential-pulse train is then applied at certain stage before a critical nucleus is formed to interfere with the nucleation process. Nucleation is then allowed to continue at a stable overpotential until a critical nucleus is formed. By comparing the arrival-time distributions of the critical nuclei with and without the pulse interference, information about the mechanism of the nucleation can be obtained. In particular, it is found that a termination process is involved in the formation of a single silver nucleus at medium and low potentials, and that the structures of the critical nuclei may be different at different overpotentials.

Determination of copper(II) by anodic stripping voltammetry using a flow-through system

Copper(II) has been determined using anodic stripping voltammetry in a flow-through system. The working electrodes consisted of thin mercury films plated on a glassy carbon macrolectrode or microelectrode. Two flow-through cells, based on the wall-jet configuration and the thin-layer configuration, respectively, accommodated the working electrodes. Depending on the type of analysis, the flow system could operate on the flow injection mode or continuous flow mode during the preconcentration period. The sequence of operations (mercury plating, metal preconcentration, stripping and electrode cleaning) were remotely controlled. The procedures developed were applied to the quantification of CuII in different matrices (tap water, acidified sea-water and pharmaceutical tablets).

Determination of organonitriles using enzyme-based selectivity mechanisms. 2. A nitrilase-modified glassy carbon microelectrode sensor for benzonitrile

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDetermination of organonitriles using enzyme-based selectivity mechanisms. 2. A nitrilase-modified glassy carbon microelectrode sensor for benzonitrileTimothy Z. Liu, Yi. Wang, Samuel P. Kounaves, and Edward J. BrushCite this: Anal. Chem. 1995, 67, 10, 1679–1683Publication Date (Print):May 15, 1995Publication History Published online1 May 2002Published inissue 15 May 1995https://doi.org/10.1021/ac00106a005RIGHTS & PERMISSIONSArticle Views107Altmetric-Citations13LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (651 KB) Get e-Alerts Get e-Alerts

Preparation and amperometric response of carbon and platinum dual-cylinder microelectrodes

The design and function of an amperometric dual-microelectrode is communicated which can operate as a collection sensor. The device consists of two individually addressable microelectrodes of parallel cylindrical geometry. Dual-cylinder microelectrodes have been prepared from micrometre platinum wire and carbon fibre to extremely good precision using a microscope fabrication technique. The shielding and feedback properties of the new microelectrode assembly have been evaluated with respect to electrode separation for the case of the hexacyanoferrate (iii)/(ii) couple. Carbon fibre (CF) devices with cylinder length of 585 μm are suitable for the cycling of organic redox couples between narrow gap electrodes. A discussion follows reporting the selective sensing of 1,4-dihydroxybenzene at a narrow gap CF device where the chemical and electrochemical effects of ascorbate interferences are largely filtered out to concentrations of 200μM.

Subfemtomole Detection of Catecholamine with Interdigitated Array Carbon Microelectrodes in HPLC

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSubfemtomole Detection of Catecholamine with Interdigitated Array Carbon Microelectrodes in HPLCHisao. Tabei, Masaya. Takahashi, Satoshi. Hoshino, Osamu. Niwa, and Tsutomu. HoriuchiCite this: Anal. Chem. 1994, 66, 20, 3500–3502Publication Date (Print):October 15, 1994Publication History Published online1 May 2002Published inissue 15 October 1994https://doi.org/10.1021/ac00092a031RIGHTS & PERMISSIONSArticle Views209Altmetric-Citations55LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (320 KB) Get e-Alerts Get e-Alerts

A potentiostatic study of silver centres and their catalytic effect on hydrogen peroxide using carbon microelectrodes

Potentiostatic measurements are reported for the growth of silver centres in the absence and in the presence of mixed reduction/oxidation of hydrogen peroxide on carbon microdisc electrodes. The application of growth laws and polarization effects are discussed and it is shown that the silver growth process is kinetically controlled at very short times, becoming diffusion controlled as time increases. From the polarization curves, the rate constants of silver deposition were determined. For the system silver/hydrogen peroxide the results show that the reduction/oxidation of H 2O 2 at silver substrates is controlled by the occurrence of a non-electrochemical reaction.

Oxidation of iodide to iodate concurrently with evolution of oxygen at Kelgraf composite electrodes

The oxidation of I− to IO 3 − in acidic media occurs at numerous electrode materials at potential values corresponding to the anodic discharge of H2O with simultaneous evolution of oxygen. In the study reported here the anodic current density for IO 3 − production was measured by difference voltammetry at rotated disc electrodes (r.d.e.'s) constucted from pure glassy carbon (GC) and Kelgraf (graphite plus Kel-F) composite materials. These signal values (S) were normalized relative to the background current (B) for oxygen evolution measured at 1.75 V vs SCE, a potential corresponding to the transport-limited production of IO 3 − at GC. Despite a small positive shift in E 1/2 with decreasing fractional active area, the signal-to-background ratio (S/B) at the Kelgraf electrodes was enhanced relative to that for the GC electrode. For example, SIB at a 2% Kelgraf r.d.e. was nine times larger than at a GC r.d.e. This corresponds to an increase in current efficiency (S/(S + B)) for IO 3 − production from about 50% at the GC r.d.e. to about 90% at 2% Kelgraf r.d.e. This is explained on the basis of (i) a significant decrease in total background current as a result of the decreased fraction of the Kelgraf surface that corresponds to carbon, and (ii) a larger flux density of I− at the carbon microelectrodes in the Kelgraf r.d.e., as compared to the GC r.d.e., as a result of radial diffusion, i.e. the so-called ‘edge effect’.

Studies of silver electronucleation onto carbon microelectrodes

It is shown that it is possible to use microelectrodes to develop a number of strategies for the measurement of silver electronucleation kinetics at the molecular level. The direct measurement of individual events and therefore stochastic deterministic growth of the centres allows determination of an accurate value of the arrival time of the first nucleus. The distribution of these arrival times follows the simplest model of a pure birth process with identical rate constants for all the aggregation steps.

Electrochemical investigations of poplar, spinach, cucumber, and parsley plastocyanins at conventional and microsized carbon electrodes

Thermodynamic and kinetic aspects of the electrochemistry of the “blue” copper protein plastocyanin from poplar, spinach, cucumber, and parsley have been studied at both macro- and microsized carbon-disk electrodes. Reversible formal potentials EFO at 3 OC have been determined by cyclic voltammetry in the range 3.6 I pH I 7.6. Above pH 6.6 the reversible potentials of all four plastocyanins are independent of pH and have limiting values of 389 f 7 mVvs NHE. Below pH 6.6 the reversible potentials are functions of pH. Poplar, spinach, and cucumber plastocyanins have similar pH dependences, but the curve for parsley plastocyanin is shifted by -0.7 pH unit toward higher pH. While the reasons for this difference and for some other details of the pH dependences are not completely understood, the fact that parsley plastocyanin behaves differently from the others is consistent with antecedent observations of redox kinetics. The electrochemical kinetic behavior of the plastocyanin/graphite interface is complex and is influenced by a competing protein adsorption process. Under the experimental conditions employed, only a small fraction (< 10%) of the electrode surface is active so that the conventional linear diffusion model (in which the entire surface participates) is untenable. Instead, the apparent kinetic parameters (peak separations) of the voltammetric data recorded with normal macrosized electrodes are strongly influenced by nonlinear mass transport to micron- to submicron-sized active sites. When nonlinear diffusion is taken into account, the experiments are consistent with very fast electron transfer between plastocyanin and the active sites of the carbon electrodes. The detection of nonlinear diffusion, combined with the detection of a voltammetric response for free Cuz+, provides a sensitive probe of the integrity of the protein; the voltammogram of the intact protein is modified in the presence of apoprotein or denatured protein. The data obtained from measurements at conventionally sized electrodes are confirmed by results obtained at carbon microelectrodes. Not only is radial diffusion found to be the predominant mechanism of mass transport (as expected from the small size of the electrodes) but also partial blocking of even these electrodes can be clearly demonstrated.

Cyclic voltammetry at gold, platinum and carbon microelectrodes in ice without added supporting electrolyte: Evidence for liquid microphases at temperatures well below the freezing point of water

The voltammetry of the Fe 3+/2+ redox couple has been investigated in water without added electrolyte at temperatures considerably below the freezing point of the solvent. In order to minimize problems with (ohmic) IR drop, and to investigate the possible role of the electrode material, gold, platinum and glassy carbon microdisc rather than conventionally sized working electrodes were employed. Reduction of ferric sulphate, nitrate and chloride solutions was examined to ascertain the role of the anion, and data were compared with results of studies in perchloric acid to examine the role of added electrolyte. Irrespective of the electrode material, the anion, or the presence or absence of perchloric acid, the nature of the mass transport changes, from steady-state diffusion (sigmoidal shaped curves) in the liquid phase to a surface-confined process (peak shaped curves) in the ice phase. Under these surface-confined conditions, reduction of iron(III) and oxidation of iron(II) exhibits surface-confined or thin-layer type electrochemistry. Additionally, an increase in the peak current of the surface-confined process occurs over the temperature range −10°C to −40°C. Data suggest that the change in mass transport mechanism is a function of the solvent properties rather than the electrode material, anion or added electrolyte and that a liquid microphase which concentrates solutes in the microphase exists in the aqueous solvents at temperatures well below the freezing point of water. Presumably, at sufficiently low temperatures, precipitation of insoluble material also occurs onto the electrode surface. The observations in frozen water are also consistent with the previously published idea of a liquid microphase contributing to the voltammetry in frozen dimethylsulphoxide.

Determination of stability constants using a mercury microelectrode and steady-state voltammetry

A mercury microelectrode obtained by the deposition of mercury onto a carbon microelectrode operating in steady-state conditions was used for determining stability constants using a classical polarography method—DeFord Hume's method. As a model system the complexation of cadmium by glycine was chosen and a good agreement was found with literature values and with the results obtained using a conventional dropping mercury electrode.

Electrochemical Behavior of Carbon Microelectrodes Prepared by Using Graphite/Carbon Composite

Electrochemical Behavior of Carbon Microelectrodes Prepared by Using Graphite/Carbon Composite

The adsorption of single molecules of DNA on carbon microelectrodes

A direct electrochemical method for the investigation of single molecular events is described. The high signal to noise advantage of microelectrodes is sufficient to monitor such events under certain circumstances. In this work, we monitor the adsorption of single DNA molecules from solution at carbon microdisk electrodes.