Electrodes specially modified

In the first part of the present review, new techniques of preparation of modified electrodes and their electrochemical properties are presented. The second part is devoted to applications based on electrochemical reactions of solute species at modified electrodes. Special focus is given to the general requirements for the use of modified electrodes in synthetic and analytical organic electrochemistry. The subject has been reviewed several times Besides the latest general review by Murray a number of more recent overview articles have specialized on certain aspects macro-molecular electronics theoretical aspects of electrocatalysis organic applicationssensor electrodes and applications in biological and medicinal chemistry. 

Arguably, the first commercial analytical chemical instrument" was the glass electrode poten-tiometric pH meter, invented and marketed by Arnold Beckman in the 1930s. In 2004, a group at Oxford University published a means of measuring pH with special modified carbon nanotube... 

PC is used as a constituent of plasticizer to enhance ionic conductivity, and in order to realize this, specially modified graphite which is compatible with PC is developed as an active material for a negative electrode. 

Special electrochemical sensors that operate on the principle of the voltammetric cell have been developed. The area of chemically modified solid electrodes (CMSEs) is a rapidly growing field, giving rise to the development of new electroanalytical methods with increased selectivity and sensitivity for the determination of a wide variety of analytes [490]. CMSEs are typically used to preconcentrate the electroactive target analyte(s) from the solution. The use of polymer coatings showing electrocatalytic activity to modify electrode surfaces constitutes an interesting approach to fabricate sensing surfaces useful for analytical purposes [491]. 

The air gas-diffusion electrode developed in this laboratory [2] is a double-layer tablet comprising a porous hydrophobic gas layer and a catalytic layer in which the catalyst is placed. The gas layer of the electrode is prepared from hydrophobic material carbon black modified with PTFE by a special technology [3], The catalytic layer contains a porous catalyst. 

Chemically modified electrode (CME) An electrode covered with a special coating (of a conductor or semiconductor unless very thin), thereby altering its electrochemical properties. 

It was pointed ouF that while ionomer-modified electrodes have greater selectivity than naked electrodes, ionomers provide only a general form of selectivity (charge type and mass or hydrophobicity selectivity), and special methods were suggested to improve specific selectivity. For example, it was thought that applying an additional cellulose acetate layer over the Nafion film would make the electrode selective with respect to dopamine specifically (in contrast to other neurotransmitters). To make the electrode system specifically selective to o-nitrophenol (in contrast to /(-isomer), a complexation with cyclodextrin was performed, which increased the selectivity ratio one order of magnitude with respect to the o-isomer. ... 

PossibiKties of electrocatalysis of reactions at electrodes are among the powerful incentives for the electrochemical study of POMs. Interesting results were obtained both in electrocatalytic reductions and oxidations, provided the appropriate form of the POM is used. Two recent reviews devoted to the electrochemical properties of polyoxometalates as electrocatalysts are available [8, 9]. The second one focuses more specifically on electrocatalysis on modified electrodes. In the present text, attention will be drawn specially to the basic principles that could be considered to govern most of solution processes. The principles will be illustrated by several recent experimental results, even though earlier achievements will also be described briefly. 

A special way to use a mediator in redox reactions is to bind it chemically to the electrode such chemically modified electrodes may have many future... 

A few special technical problems arise when attempting to mount film electrodes into conventional electrochemical cells due to difficulties in defining the electrode area and in making electrical connection to the active surface. These constraints usually result in cells that have been somewhat modified, although the same principles that were discussed in Chapter 9 still apply. In this final section we address some of these practical difficulties. 

In the last 20 years, a big effort has been made to characterize different reaction schemes taking place at modified electrodes, with special focus on the case of biomolecules in what has been called Protein Film Voltammetry [79-83]. Among the different situations analyzed with multipulse techniques (including Cyclic Voltammetry), it can be cited the surface ECE process [89, 90] and surface reactions preceded by homogeneous chemical reactions [91]. For a more detailed revision of the different mechanisms analyzed in the case of SWV, see [19]. 

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