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Microelectrode

SECM Scanning electrochemical microscopy [40] An STM serves as microelectrode to reduce electroactive species Electrochemical reactions on surfaces... [Pg.313]

The scan rate, u = EIAt, plays a very important role in sweep voltannnetry as it defines the time scale of the experiment and is typically in the range 5 mV s to 100 V s for nonnal macroelectrodes, although sweep rates of 10 V s are possible with microelectrodes (see later). The short time scales in which the experiments are carried out are the cause for the prevalence of non-steady-state diflfiision and the peak-shaped response. Wlien the scan rate is slow enough to maintain steady-state diflfiision, the concentration profiles with time are linear within the Nemst diflfiision layer which is fixed by natural convection, and the current-potential response reaches a plateau steady-state current. On reducing the time scale, the diflfiision layer caimot relax to its equilibrium state, the diffusion layer is thiimer and hence the currents in the non-steady-state will be higher. [Pg.1927]

A microelectrode is an electrode with at least one dimension small enough that its properties are a fimction of size, typically with at least one dimension smaller than 50 pm [28, 29, 30, 31, 32 and 33]. If compared with electrodes employed in industrial-scale electrosynthesis or in laboratory-scale synthesis, where the characteristic dimensions can be of the order of metres and centimetres, respectively, or electrodes for voltannnetry with millimetre dimension, it is clear that the size of the electrodes can vary dramatically. This enonnous difference in size gives microelectrodes their unique properties of increased rate of mass transport, faster response and decreased reliance on the presence of a conducting medium. Over the past 15 years, microelectrodes have made a tremendous impact in electrochemistry. They have, for example, been used to improve the sensitivity of ASV in enviroiunental analysis, to investigate rapid... [Pg.1938]

Microelectrodes with several geometries are reported in the literature, from spherical to disc to line electrodes each geometry has its own critical characteristic dimension and diffusion field in the steady state. The difhisional flux to a spherical microelectrode surface may be regarded as planar at short times, therefore displaying a transient behaviour, but spherical at long times, displaying a steady-state behaviour [28, 34] - If a... [Pg.1939]

This expression is the sum of a transient tenu and a steady-state tenu, where r is the radius of the sphere. At short times after the application of the potential step, the transient tenu dominates over the steady-state tenu, and the electrode is analogous to a plane, as the depletion layer is thin compared with the disc radius, and the current varies widi time according to the Cottrell equation. At long times, the transient cunent will decrease to a negligible value, the depletion layer is comparable to the electrode radius, spherical difhision controls the transport of reactant, and the cunent density reaches a steady-state value. At times intenuediate to the limiting conditions of Cottrell behaviour or diffusion control, both transient and steady-state tenus need to be considered and thus the fiill expression must be used. Flowever, many experiments involving microelectrodes are designed such that one of the simpler cunent expressions is valid. [Pg.1939]

Of course, in order to vary the mass transport of the reactant to the electrode surface, the radius of the electrode must be varied, and this unplies the need for microelectrodes of different sizes. Spherical electrodes are difficult to constnict, and therefore other geometries are ohen employed. Microdiscs are conunonly used in the laboratory, as diey are easily constnicted by sealing very fine wires into glass epoxy resins, cutting... [Pg.1939]

SECM is a scaiming-probe teclmiqiie introduced by Bard et aJ in 1989 [49, and M ] based on previous studies by the same group on in situ STM [ ] and simultaneous work by Engstrom et aJ [53 and M], who were the first to show that an amperometric microelectrode could be used as a local probe to map the concentration profile of a larger active electrode. SECM may be envisaged as a chemical microscope based on faradic current changes as a microelectrode is moved across a surface of a sample. It has proved iisefiil for... [Pg.1940]

The apparatus consists of a tip-position controller, an electrochemical cell with tip, substrate, counter and reference electrodes, a bipotentiostat and a data-acquisition system. The microelectrode tip is held on a piezoelectric pusher, which is mounted on an inchwomi-translator-driven x-y-z tliree-axis stage. This assembly enables the positioning of the tip electrode above the substrate by movement of the inchwomi translator or by application of a high voltage to the pusher via an amplifier. The substrate is attached to the bottom of the electrochemical cell, which is mounted on a vibration-free table [, and ]. A number... [Pg.1941]

Luminescence has been used in conjunction with flow cells to detect electro-generated intennediates downstream of the electrode. The teclmique lends itself especially to the investigation of photoelectrochemical processes, since it can yield mfonnation about excited states of reactive species and their lifetimes. It has become an attractive detection method for various organic and inorganic compounds, and highly sensitive assays for several clinically important analytes such as oxalate, NADH, amino acids and various aliphatic and cyclic amines have been developed. It has also found use in microelectrode fundamental studies in low-dielectric-constant organic solvents. [Pg.1948]

Evans D FI 1991 Review of voltammetric methods for the study of electrode reactions Microelectrodes Theory and Applications (Nate ASI Series E vol 197) ed M I Montenegro, M A Queiros and J L Daschbach (Dordrecht Kluwer)... [Pg.1949]

Pons S and Flelschmann M 1987 The behavior of microelectrodes Anal. Chem. 59 1391A... [Pg.1950]

Cassidy J F and Foley M B 1993 Microelectrodes—potential Invaders Chem. Br. 29 764... [Pg.1950]

Oldham K B 1991 Steady-state microelectrode voltammetry as a route to homogeneous kinetics J. Electroanal. Chem. 313 3... [Pg.1950]

Koudelka-Flep M and Van der Wal P D 2000 Microelectrode sensors for biomedical and environmental applications Electrochim. Acta 45 2437... [Pg.1950]

Tanaka K and Tokuda K 1996 In vivo electrochemistry with microelectrodes Experimental Techniques in Bioelectrochemistry ed V Brabec, D Walz and G Milazzo (Basel Birkhauser)... [Pg.1950]

Birkin P R and SilvaMartinez S 1995 The effect of ultrasound on mass-transport to a microelectrode J. Chem. See., Chem. Commun. 17 1807... [Pg.1952]

Henglein A 1988 Mechanism of reactions on colloidal microelectrodes and size quantization effects Top. Curr. Chem. 143 115... [Pg.2914]

Scale of Operation Voltammetry is routinely used to analyze samples at the parts-per-million level and, in some cases, can be used to detect analytes at the parts-per-billion or parts-per-trillion level. Most analyses are carried out in conventional electrochemical cells using macro samples however, microcells are available that require as little as 50 pL of sample. Microelectrodes, with diameters as small as 2 pm, allow voltammetric measurements to be made on even smaller samples. For example, the concentration of glucose in 200-pm pond snail neurons has been successfully monitored using a 2-pm amperometric glucose electrode. ... [Pg.531]

Immersion electrodes are the most common glass electrodes. These are roughly cylindrical and consist of a barrel or stem of inert glass that is sealed at the lower end to a tip, which is often hemispherical, of special pH-responsive glass. The tip is completely immersed in the solution during measurements. Miniature and microelectrodes are also used widely, particularly in physiological studies. Capillary electrodes permit the use of small samples and provide protection from exposure to air during the measurements, eg, for the determination of blood pH. This type of electrode may be provided with a water jacket for temperature control. [Pg.466]

Ion-selective electrodes and amperometric ceUs have had a long history of success in a wide variety of appHcations (8,9). A microelectronics-inspired revolution is also occurring in these devices, brought about by the advent of photoHthographicaHy defined arrays of microelectrodes on planar substrates... [Pg.392]

Aqueous diffusion coefficients are usually on the order of 5 x 10 cm /s. A second is typically a long time to an electrochemist, so 6 = 30 fim. The definition of far is then 30 ]lni. Short is less than a second, perhaps a few milliseconds. Microseconds are not uncommon. Small, referring to the diameter of the electrode, is about a millimeter for microelectrodes, or perhaps only a few micrometers for ultramicroelectrodes (13). [Pg.53]

Lead materials lead-antimony-silver, lead with platinum alloy microelectrodes, lead/magnetite, lead dioxide/titanium, lead dioxide/ graphite. [Pg.163]

The formation of a PbO coating on Pb when it is anodically polarised in Cl is achieved more readily by alloying lead with silver or other metals, or by incorporating inert conducting microelectrodes in the Pb surface. [Pg.180]

The insertion of platinum microelectrodes into the surface of lead and some lead alloys has been found to promote the formation of lead dioxide in chloride solutions" " . Experiments with silver and titanium microelectrodes have shown that these do not result in this improvement". Similar results to those when using platinum have been found with graphite and iridium, and although only a very small total surface area of microelectrodes is required to achieve benefit, the larger the ratio of platinum to lead surface, the faster the passivation". Platinised titanium microelectrodes have also been utilised. [Pg.182]

The action of platinum microelectrodes has been extensively studied Trials carried out by Peplow have shown that lead/ platinum bi-electrodes can be used in high velocity seawater at current densities up to 2 000 Am and that blister formation with corrosion under the blisters is decreased by the presence of platinum microelectrodes. The current density range in which the anode is normally operated is 200-750 Am with the maximum working current density quoted as 1 000 Am The consumption rate of theje anodes ranged from 0-0014 kg A y at 500Am , but increased to 0-003 kg... [Pg.182]


See other pages where Microelectrode is mentioned: [Pg.112]    [Pg.1933]    [Pg.1938]    [Pg.1939]    [Pg.1939]    [Pg.1940]    [Pg.1940]    [Pg.1940]    [Pg.1941]    [Pg.1942]    [Pg.1950]    [Pg.1950]    [Pg.1950]    [Pg.493]    [Pg.494]    [Pg.633]    [Pg.209]    [Pg.110]    [Pg.310]    [Pg.145]    [Pg.1154]   
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Advanced microelectrode systems for pH determination

Advantages of Microelectrodes in Electroanalysis

Ag/AgCl reference microelectrodes

All-solid-state pH microelectrodes

Alternating-Current Electrode Polarization in Microelectrode Systems

Amperometric biosensor based carbon fiber microelectrodes

Amperometry at microelectrodes

Antimony microelectrode

Application of microelectrodes

Applications of Photoresist Microelectrodes

Arrays of microelectrodes

Band microelectrode

Band microelectrode current

Band microelectrodes

Calibration curve and linear response slope of pH microelectrodes

Carbon fiber microelectrodes

Carbon microelectrodes

Carbon-fiber microelectrode

Characteristics of Microelectrode

Characterization of pH microelectrodes

Chemically modified microelectrodes

Clarke Oxygen Microelectrode

Configurations of Microelectrodes

Cyclic voltammetry microelectrodes

Cyclic voltammogram microelectrode

Diamond microelectrodes

Diffusion at Microelectrodes

Disc microelectrode

Disc microelectrodes

Disk-in-glass microelectrodes

Electrical Connections to Microelectrodes

Electrical Properties of Microelectrodes

Electrochemical methods microelectrodes

Electrochemical microelectrode

Electrochemical microelectrode ultramicroelectrodes

Electrochemical scanning microscope microelectrode

Electrode Microelectrode)

Electrode boron-doped diamond microelectrode

Electrode microelectrode arrays

Electrode polarization microelectrodes

Electrodes fabrication, for NO determination integrated microelectrodes

Electrodes microelectrodes

Electrodes oxygen microelectrode

Electrolyte-Filled Glass Microelectrodes

Em, measurement microelectrodes

Enhancement of Diffusion at a Microelectrode

Ensembles of microelectrodes

Examples of Microelectrode Measurements in Solid State Ionics

Experimental Realization of Microelectrode Measurements

Fabrication of Microelectrode Arrays

Fabrication of microelectrodes for pH determination

From Microelectrodes to Scanning Electrochemical Microscopy

Glass microelectrode

Glass microelectrodes

Glass-based pH microelectrodes

Gold spherical microelectrodes

Hydrodynamic/microelectrode methods

Impedimetric Immunosensors Using Interdigitated Array Microelectrodes

Implantable pH microelectrodes

In vivo applications, of pH microelectrodes

In vivo applications, of pH microelectrodes under skin

Instruments microelectrode probes

Integrated NO microelectrodes

Interdigital microelectrodes coated

Interdigitated Microelectrode

Interdigitated array microelectrodes

Interdigitated microelectrode electrode arrays

Interdigitated microelectrode electrode arrays IDAs)

Ion-selective microelectrodes

Liquid ion-exchanger microelectrodes

Macroelectrode Partially Covered With Hemispherical Active Microelectrodes

Macroelectrodes and Microelectrodes

Mercury microelectrodes

Metal microelectrodes

Metal microelectrodes wires

Microelectrode Applications

Microelectrode Configurations

Microelectrode advantages

Microelectrode array behavior

Microelectrode array interdigitated microbands

Microelectrode array microband

Microelectrode array microdisc

Microelectrode array structures

Microelectrode arrays

Microelectrode arrays for pH mapping

Microelectrode current-time dependence

Microelectrode designs

Microelectrode designs diffusion layer

Microelectrode designs techniques)

Microelectrode geometry

Microelectrode microband

Microelectrode microdisc

Microelectrode polarography

Microelectrode potential

Microelectrode structure

Microelectrode techniques

Microelectrode voltammetric

Microelectrode voltammetry

Microelectrodes

Microelectrodes

Microelectrodes and Fast Scan Voltammetry

Microelectrodes applications

Microelectrodes arrays

Microelectrodes characterization

Microelectrodes chemical sensors

Microelectrodes coated with phthalocyanines

Microelectrodes diffusion field, development

Microelectrodes diffusion, enhancement

Microelectrodes diffusion-limited current

Microelectrodes edge effect

Microelectrodes electrical connections

Microelectrodes electrical noise

Microelectrodes electrical properties

Microelectrodes electrochemical properties

Microelectrodes electronic equipment

Microelectrodes ensembles

Microelectrodes equivalent circuit

Microelectrodes etching

Microelectrodes features

Microelectrodes food analysis

Microelectrodes frequency response

Microelectrodes history

Microelectrodes homogeneous kinetics study

Microelectrodes insulating

Microelectrodes interdigital

Microelectrodes lithium deposition

Microelectrodes mass transport regime

Microelectrodes materials

Microelectrodes metal-filled glass

Microelectrodes metal-through-glass

Microelectrodes multiple

Microelectrodes nanoparticle detection

Microelectrodes noise

Microelectrodes normal pulse voltammetry

Microelectrodes ohmic drop

Microelectrodes pipette filling

Microelectrodes polarization

Microelectrodes profiles

Microelectrodes pulling

Microelectrodes random array

Microelectrodes resistance

Microelectrodes resistive media

Microelectrodes shapes

Microelectrodes signal distortion

Microelectrodes single cell measurements

Microelectrodes steady state current

Microelectrodes stripping analysis

Microelectrodes trace analysis

Microelectrodes transient studies

Microelectrodes viscosity

Microelectrodes voltammetry

Microelectrodes zirconia

Microelectrodes, advantages

Microelectrodes, calibration

Microelectrodes, electrochemistry

Microelectrodes, electrophoresis

Microelectrodes, for in vivo pH measurement advantages

Microelectrodes, for in vivo pH measurement applications

Microelectrodes, for in vivo pH measurement biocompatibility

Microelectrodes, for in vivo pH measurement calibration curve

Microelectrodes, for in vivo pH measurement characterization

Microelectrodes, for in vivo pH measurement fabrication

Microelectrodes, for in vivo pH measurement lab-on-a-chip sensing system

Microelectrodes, for in vivo pH measurement linear response slope

Microelectrodes, for in vivo pH measurement reliability

Microelectrodes, for in vivo pH measurement reproducibility/accuracy

Microelectrodes, for in vivo pH measurement response time

Microelectrodes, for in vivo pH measurement selectivity

Microelectrodes, for in vivo pH measurement sensitivity

Microelectrodes, for in vivo pH measurement significance

Microelectrodes, for in vivo pH measurement stability

Microelectrodes, for in vivo pH measurement techniques

Microelectrodes, for in vivo pH measurement under skin

Microelectrodes, glutamate

Microelectrodes, neural

Microelectrodes, oxygen

Microelectrodes, photoresist

Microelectrodes, voltammetric

Microfabricated microelectrodes

Microfabricated thin-film microelectrode

Microfabricated thin-film microelectrode technologies

Micropipette ion-selective microelectrodes

Modified microelectrode arrays

Nafion coated microelectrode

Nanoparticles compared to microelectrodes

Nanoparticles detection using microelectrodes

New Applications of Microelectrodes in Electroanalysis

Nitric oxide electrochemical sensors integrated NO microelectrodes

Noise in Glass Microelectrodes

Other Microelectrodes

Oxygen microelectrode

Platinum wire microelectrode

Polyimide-based microelectrode

Polymer membrane-based pH microelectrodes

Polymer-based microelectrodes

Potassium selective microelectrode

Preparation of Ion-Selective Microelectrodes

Pyrolytic carbon microelectrodes

Random array of microelectrodes (

Random assemblies of microelectrodes

Random microelectrode arrays

Reactions of Dissolved Species on Spherical Electrodes and Microelectrodes

Recessed microelectrode

Redox microelectrodes

Reference Microelectrodes

Resistance of Microelectrodes

Resistance, microelectrode

Response time pH microelectrodes

Rotating platinum microelectrode

Self-assembled spherical gold microelectrodes

Silicon-based pH microelectrodes

Silver disk microelectrode

Simple Reactions on Stationary Spherical Electrodes and Microelectrodes

Special Considerations for Microelectrodes

Specific Microelectrodes

Spherical microelectrodes

Twin-polarized microelectrodes

Ultra-microelectrodes

Voltammetry at Microelectrodes

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