Modifiers, chemically modified electrode

Chemically modified electrodes (CMEs) represent a modem approach to electrode systems. These rely on the placement of a reagent onto the surface, to impart the behavior of that reagent to the modified surface. Such deliberate alteration of electrode surfaces can thus meet the needs of many electroanalytical problems, and may form the basis for new analytical applications and different sensing devices. 

Explain clearly how chemically modified electrodes can benefit electrochemical measurements ... 

Chemically modified electrodes, 39, 118 Chemometrics, 197 Chemoreceptor, 187 Chip, 194, 195 Chloramphenicol, 70 Chloride electrode, 159 Chlorpromazine, 34 Cholesterol, 182 Cholinesterase, 182 Chromium, 85, 86 Chronoahsorptometry, 42 Chronoamperometry, 21, 60, 130, 135, 132, 177... 

The electrochemistry of conducting polymers has been the subject of several reviews2-8 and has been included in articles on chemically modified electrodes.9-14 The primary purpose of this chapter is to review fundamental aspects of the electrochemistry of conducting polymer films. Applications, the diversity of materials available, and synthetic methods are not covered in any detail. No attempt has been made at a comprehensive coverage of the relevant literature and the materials that have been studied. Specific examples have been selected to illustrate general principles, and so it can often be assumed that other materials will behave similarly. 

It was also observed that, with the exception of polyacetylene, all important conducting polymers can be electrochemically produced by anodic oxidation moreover, in contrast to chemical methoconducting films are formed directly on the electrode. This stimulated research teams in the field of electrochemistry to study the electrosynthesis of these materials. Most recently, new fields of application, ranging from anti-corrosives through modified electrodes to microelectronic devices, have aroused electrochemists interest in this class of compounds... 

The historical development of chemically electrodes is briefly outlined. Following recent trends, the manufacturing of modified electrodes is reviewed with emphasis on the more recent methods of electrochemical polymerization and on new ion exchanging materials. Surface derivatized electrodes are not treated in detail. The catalysis of electrochemical reactions is treated from the view of theory and of practical application. Promising experimental results are given in detail. Finally, recent advances of chemically modified electrodes in sensor techniques and in the construction of molecular electronics are given. 

In 1975, the fabrication of a chiral electrode by permanent attachment of amino acid residues to pendant groups on a graphite surface was reported At the same time, stimulated by the development of bonded phases on silica and aluminia surfaces the first example of derivatized metal surfaces for use as chemically modified electrodes was presented. A silanization technique was used for covalently binding redox species to hydroxy groups of SnOj or Pt surfaces. Before that time, some successful attemps to create electrode surfaces with deliberate chemical properties made use of specific adsorption techniques... 

Some porous ceramic structures of oxides on titanium (CT2O3, RuOj, MnOj, VOJ obtained by baking films of metal complexes like acetylacetonates on titanium surfaces can also be regarded as chemically modified electrodes Applications... 

Certainly, the same arguments apply for chemical redox catalysis , but as discussed above, thinner films may be effective in this case. Hence, it will be reasonable to work with modified electrodes having a large effective area instead of thick films, i.e. three-dimensional, porous or fibrous electrodes. The notorious problem with current/potential distribution in such electrodes may be overcome by the potential bias given by selective redox catalysts. Some approaches in this direction are described in the next section. 

The reductive cleavage of the alkylcobalamine is facilitated by light irradiation and can then proceed at a much more positive potential. A demonstration photoelec-trochemical reactor for the Bij-catalyzed photoelectrochemical synthesis of Michael adduct 17, the alarm pheromone of the ant atta texana (Scheme 9) has been constructed where the complete device is driven solely by solar energy . Hopefully, mediated photoelectrochemical reactions of this type will also be realized at chemically modified electrodes. 

Chemical and electrochemical techniques have been applied for the dimensionally controlled fabrication of a wide variety of materials, such as metals, semiconductors, and conductive polymers, within glass, oxide, and polymer matrices (e.g., [135-137]). Topologically complex structures like zeolites have been used also as 3D matrices [138, 139]. Quantum dots/wires of metals and semiconductors can be grown electrochemically in matrices bound on an electrode surface or being modified electrodes themselves. In these processes, the chemical stability of the template in the working environment, its electronic properties, the uniformity and minimal diameter of the pores, and the pore density are critical factors. Typical templates used in electrochemical synthesis are as follows ... 

The oxidation of N ADH has been mediated with chemically modified electrodes whose surface contains synthetic electron transfer mediators. The reduced form of the mediator is detected as it is recycled electrochemically. Systems based on quinones 173-175) dopamine chloranil 3-P-napthoyl-Nile Blue phenazine metho-sulphatemeldola blue and similar phenoxazineshave been described. Conducting salt electrodes consisting of the radical salt of 7,7,8,8-trtra-cyanoquinodimethane and the N-methylphenazium ion have been reported to show catalytic effects The main drawback to this approach is the limited stability... 

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