Silver effect electrodes

The electrochemical photovoltaic effect was discovered in 1839 by A. E. Becquerelt when a silver/silver halide electrode was irradiated in a solution of diluted HN03. Becquerel also first described the photogalvanic effect in a cell consisting of two Pt electrodes, one immersed in aqueous and the other in ethanolic solution of Fe(C104)3. This discovery was made about the same time as the observation of the photovoltaic effect at the Ag/AgX electrodes. The term Becquerel effect often appears in the old literature, even for denoting the vacuum photoelectric effect which was discovered almost 50 years later. The electrochemical photovoltaic effect was elucidated in 1955 by W. H. Brattain and G. G. B. Garrett the theory was further developed... 

An ideal ISE would exhibit a specific response to a certain ion J and the effect of interferents would be excluded. Except for the silver sulphide electrode, which is specific for sulphide or silver ions, no ion-selective electrode has this property. The others exhibit selectivity only for a particular ion with respect to the others. The selective behaviour of an ISE follows from (3.1.7). If the activity of the interferent is sufficiently low, i.e. if... 

The potential of the silver-silver chloride electrode is sensitive to traces of bromide in the solution used to deposit AgCl. The presence of 0.01 mole percent (mol %) of bromide in a KC1 electrolyte is sufficient to alter the potential of electrodes immersed in the solution by 0.1-0.2 mV.28 The potentials are not greatly affected by traces of iodide or cyanide. Light of ordinary intensities does not have a marked effect on the potential of the electrodes, but exposure to direct sunlight should be avoided. 

Figure 12.9 shows the output and transfer characteristics of a state-of-the-art, polymer FET fabricated using the Plastic Logic direct-write manufacturing process (L = 10 pm). No encapsulation of the TFT is present other than what is naturally provided by the presence of the PET substrate on the bottom and an inkjet printed silver gate electrode on the top. The device exhibits a field-effect mobility of 0.04 cm2 V 1 s 1 and ON-OFF current ratio of 5 x 10s. The threshold potential is Vt = 5-6 V. These basic TFT performance values can be achieved consistently in a manufacturing environment, and are sufficient to drive a 100 dpi electronic paper display with A5 size. 

Example 4. The transport number during electrodialysis (dynamic state transport number) may be measured using a similar two-compartment cell with reversible electrodes such as silver-silver chloride electrodes (Figure 4.6). The transport number is calculated from the transported ions and the amount of electricity passed through the membrane, which is measured with a coulometer. To eliminate the effect on the transport number of electrolytes diffusing through the membrane, it is desirable that a solution of the same concentration be used on both sides of the membrane. When there is a concentration difference between the two sides, the transport number is affected by diffusion of electrolytes through the membrane. 

Little work has been done on acid-base equilibria in other disubstituted amides. Madic and Tremillon investigated the behaviour of various acids in hexamethylphosphorotriamide using a voltammetric technique with hydrogen and silver-silver perchlorate electrodes. Solvation effects in this solvent are very specific. Acid-base titrations in tetramethylurea have been reported by Culp and Caruso. ... 

The silver-silver chloride electrode has characteristics similar to a perfectly nonpolarizable electrode and is practical for use in many biomedical applications. The electrode (Figure 4.1a) consists of a silver base structure that is coated with a layer of the ionic compound silver chloride. Some of the silver chloride when exposed to light is reduced to metallic silver hence, a typical silver-silver chloride electrode has finely divided metallic silver within a matrix of silver chloride on its surface. Because silver chloride is relatively insoluble in aqueous solutions, this surface remains stable. Moreover, because there is minimal polarization associated with this electrode, motion artifact is reduced compared to polarizable electrodes such as the platinum electrode. Furthermore, owing to the reduction in polarization, there is also a smaller effect of frequency on electrode impedance, especially at low frequencies. 

Deleterious Effect of Quaternary Amines. Anion exchange membranes are all amine based and amines, even quaternary, may not be compatible with silver halide electrodes because they accelerate silver deposition on the cathode. 

Meanwhile, the photoelectric effect was a focus of scientific interest, with a history synchronized with that of photography. The concept of dye enhancement of the photoeffect was carried over from photography to the sensitization of an electrode already in 1887 by Moser [5] (Fig. 2) using the dye ery-throsin on silver halide electrodes and confirmed by Rigollot in 1893 [6]. In the retrospectively quaint report, written substantially before the Einstein theory of the photoelectric effect, Moser records his observations on dye-induced enhancement as an increased photopotential [V] rather than the more fundamental current (A), despite the title - Strengthened Photoelectric Current Through Optical Sensitization. ... 

Other matters which have to be considered in electrode selection are surface effects. Silver and silver-silver chloride electrodes tend to react with... 

A similar mechanism is active in cation-sensitive electrodes on the basis of silver sulphide, like the electrodes sensitive to Cd, Cu and Pb, mentioned in Table 7.2. These ions form sparingly soluble sulphides, which go in equilibrium with the silver sulphide base. It can be explained by assuming a mechanism where the salts generate a certain sulphide-ion concentration which gives rise to a response by the silver sulphide electrode. There exists a well-defined relationship between the measured potential E and the cation concentrations. The effect of the mentioned cations on the potential is only half that of single charged ions. The concentration dependence of such mixed membrane bodies is sometimes described as a response mechanism of higher... 

If the electrode under test be large as for example the macroelectrode used in deep brain stimulation applications, a three electrode cell arrangement must be used in order to eliminate the effect of counter electrode impedance on the measurement. A reference electrode, usually a silver-silver chloride electrode, must be purchased and connected to the potentiostat. The three electrode setup was explained in Chap. 1. 

Addition of iodide and the pseudohalide azide (NJ) had a similar effect as addition of chloride, whereas addition of nitrate, sulfate or perchlorate ions had no effect. The oscillation period after the initial state was found to be identical with that of the unperturbed system. When the amount of chloride added is less than the amount of cerium(IV) present initially, no observable inhibition is expected. This system is more sensitive to addition of chloride after the oscillating reaction has started than to initial addition of chloride ions smaller amounts of chloride ions are required to induce inhibition or to suppress the oscillations completely. Because of this inhibitory effect, the glass vessels used to prepare the solutions for a Belousov-Zhabotinsky experiment should be clean and free of chloride ions. Moreover, in the preparation of the ferroin indicator solution 1,10-phenanthroline must be used in its free base form and not in the form of the hydrochloride salt. If one wants to monitor the periodic changes in the chemical potential of the solution, one must use a reference electrode that does not leak chloride ions. Conventional calomel electrodes or silver/silver chloride electrodes are not suitable, but double-junction version of these electrodes are adequate. 

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