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Millimeter-sized electrodes

Figure 9 shows a cyclic voltammogram (CV) of hexacyanoferrate(III) (Fe(III)) in water observed at a gold microelectrode (8 fim wide x 33 fim long x 0.2 fim thick). A cathodic current at 200 mV corresponds to reduction of Fe(III) to Fe(II). At a micrometer-sized electrode, mass transfer of a solute in water to the electrode proceeds very efficiently owing to hemispherical diffusion of the solute. This is proved by a characteristic sigmoidal current-potential curve in the CV, different from a peak current observed at a millimeter-size electrode (linear diffusion) [32,64]. Using... [Pg.182]

The origins of SECM homogeneous kinetic measurements can be found in the earliest applications of ultramicroelectrodes (UMEs) to profile concentration gradients at macroscopic (millimeter-sized) electrodes (1,2). The held has since developed considerably, such that short-lived intermediates in electrode reactions can now readily be identified by SECM under steady-state conditions, which would be difficult to characterize by alternative transient UME methods, such as fast scan cyclic voltammetry (8). [Pg.241]

The second type of sample is composed of single crystals [19]. The crystals are plate-like (flakes) and have sub-millimeter size. They were glued by silver epoxy to the sample holder by one of their side faces. The opposite face of the flakes was used as a needle to gently touch the noble metal counter electrode in liquid helium. In this way we tried to make, preferentially, a contact along the ab plane. On average in... [Pg.275]

Taylor et al. conducted LEIS in a mapping mode to characterize the spatial variation in the admittance associated with various types of intentionally formed defects on organically coated metal surfaces (135). The LEIS probe used in these experiments consisted of chloridized silver wires to form Ag AgCl reference electrodes. Excitation frequencies between 100 and 1000 Hz were used for mapping admittance. The precise frequency used was selected to maximize the admittances differences observed. Admittance mapping resolved differences due to millimeter-sized defects associated with adsorbed machine oil, underfilm NaCl... [Pg.343]

Solid-state electrochemistry — is traditionally seen as that branch of electrochemistry which concerns (a) the -> charge transport processes in -> solid electrolytes, and (b) the electrode processes in - insertion electrodes (see also -> insertion electrochemistry). More recently, also any other electrochemical reactions of solid compounds and materials are considered as part of solid state electrochemistry. Solid-state electrochemical systems are of great importance in many fields of science and technology including -> batteries, - fuel cells, - electrocatalysis, -> photoelectrochemistry, - sensors, and - corrosion. There are many different experimental approaches and types of applicable compounds. In general, solid-state electrochemical studies can be performed on thin solid films (- surface-modified electrodes), microparticles (-> voltammetry of immobilized microparticles), and even with millimeter-size bulk materials immobilized on electrode surfaces or investigated with use of ultramicroelectrodes. The actual measurements can be performed with liquid or solid electrolytes. [Pg.620]

Most of the recent DNA hybridization detection methods employ the use of assay format and sandwich format assays as well. (Fig. 7.4a, b) [125-127]. In the largest part of publications, Ru(bpy)3 or its derivatives are widely used as ECL labels and TPA has been employed as a co-reactant. While some papers have also used several dsDNA intercalators and oxalate as reductants of electrogenerated Ru(bpy)3 [128] and co-reactant for DNA detection [129]. Different strategies have been employed for the sake of improving sensitivity such as loading or immobilization of multiple ECL labels in microsized polystyrene microspheres [130] and CNTs [127] or Au NPs [131]. As for immobilization substrates of DNA, besides millimeter-sized Au electrodes, micrometer-sized Au chips [132] and anodically oxidized GC electrodes [133] have also been employed. [Pg.134]

In cyclic voltammetry a redox-active molecule is placed in an electroanalytical cell and the electrode potential is raised from a starting value at which there is no electroactivity. When electron transfer occurs a current is measured, and the shape of the trace depends upon, among other factors, the size and shape of the electrode. Thus, at a disk or wire of millimeter-sized dimensions (millielectrode) under conditions of linear diffusion, an initial current increase imder the control of electron-transfer kinetics meets a current decrease under diffusion control towards an effectively planar surface, and a characteristic peak shape is observed [Fig. 4(a)]. If the electron-transfer reaction produces a relatively stable species, then on reversing the scan direction a current is observed in the opposite direction. [Pg.271]

This chapter is concerned with methods in which a constant potential or a potential varied with time is applied to either millimeter sized (called conventional electrodes) or MEs and the ensuing current response as a function of time or potential is measured. [Pg.374]

The conditions for planar diffusion are theoretically fulfilled only if the electrode surface is very large. In case of finite disk electrodes, edge effects arise and linear diffusion is no longer linear overall the electrode surface (Fig. 15.3). Diffusion also develops parallel to the electrode surface in the radial direction. However, if the radius of the disk electrode is large enough with respect to the diffusion layer thickness (as is the case of common employed disk electrode of millimeter size), edge effects can be neglected and Cottrell equation accurately accounts for the current profile at the electrode surface. These electrodes are nowadays called either conventional or macroelectrodes. ... [Pg.379]

Ultramicroelectrode (UME) — an - electrode having a characteristic dimension less than 25 pm. This characteristic dimension refers to a diameter for a disk, a sphere, a hemisphere, and a cylinder, and a width for a band UME, for example. Conceptually, the lower limit of the characteristic dimension of a UME is about 10 nm, which corresponds to the thickness of the - double layer or the size of molecules. Electrodes of such dimensions are sometimes referred to as - nanoelectrodes or nan-odes. Electrodes with a characteristic dimension ranging from 25 pm up to approximately 1 mm are referred to as -> microelectrodes. Electrodes with dimensions of millimeters, centimeters, or meters have been referred to... [Pg.687]


See other pages where Millimeter-sized electrodes is mentioned: [Pg.311]    [Pg.165]    [Pg.1180]    [Pg.223]    [Pg.1253]    [Pg.157]    [Pg.398]    [Pg.441]    [Pg.443]    [Pg.382]    [Pg.311]    [Pg.165]    [Pg.1180]    [Pg.223]    [Pg.1253]    [Pg.157]    [Pg.398]    [Pg.441]    [Pg.443]    [Pg.382]    [Pg.130]    [Pg.85]    [Pg.281]    [Pg.202]    [Pg.71]    [Pg.6]    [Pg.256]    [Pg.130]    [Pg.155]    [Pg.442]    [Pg.195]    [Pg.374]    [Pg.39]    [Pg.48]    [Pg.650]    [Pg.379]    [Pg.153]    [Pg.880]    [Pg.97]    [Pg.189]    [Pg.120]    [Pg.93]    [Pg.164]    [Pg.227]    [Pg.356]    [Pg.356]    [Pg.8]   
See also in sourсe #XX -- [ Pg.398 ]




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