Electrode surfaces electropolymerization technique

The enzyme can be immobilized on the electrode by several techniques (53). The simplest method, first used in 1962, is to trap an enzyme solution between the electrode surface and a semipermeable membrane. Another technique is to immobilize the enzyme in a polymer gel such as polyacrylamide which is coated on the electrode surface. Very thin-membrane films can be obtained by electropolymerization techniques (49,54,55) using polypyrrole, polyindole, or polyphenylenediamine films, among others. These thin films (qv) offer the advantage of improved diffusion of substrate and product that... 

Even with access to both a viable chemical system and a routine procedure for monitoring interfacial events based on electrochemistry, it is necessary to develop appropriate strategies for attachment of the chemical sites to electrode surfaces. We have investigated three different approaches based on a) chemical links using covalent bond formation, b) physical adsorption of premade polymers, c) electropolymerization at the electrode surface. All three techniques have their own particular nuances and will be discussed in more or less the chronological order in which they were applied to the attachment of Ru-bpy complexes. 

Electropolymerization Based on 4-Vinylpyrldlne and Related Ligands. The third technique for preparing electrode/film interfaces is in many ways the most interesting both in terms of the chemistry involved and the results so far obtained. The strategy is to induce polymerization directly at the electrode surface by oxidation or reduction and our emphasis has been on the reduction of coordinated 4-vinylpyridine and related compounds. It is known that 4-vinylpyridine is susceptible to anionic polymerization (38). 

Reductive Chloride Ion Loss and Electropolymerization Techniques in Preparing Metallopolymer Films on Electrode Surfaces... 

The electropolymerized films are usually characterized by cyclic voltammetry and UV-visible spectrophotometry on optically transparent electrodes . These techniques reveal the formation of supported N4-complexes on the electrode surface as well as provide evidence for the similarity of the electrochemical and spectrophotometric behaviour of the polymer and the starting monomers. Indeed, as it is shown in Figure 8.5, the absorption spectrum of a pyrrole-substituted Zn(II)-8 monomer complex in dichloromethane solution (Figure 8.5a) is compared with that of the electropolymerized film on ITO transparent electrode prepared by cyclic voltammetry (Figure 8.5b) and by controlled-potential electrolysis at 1.7 V (Figure 8.5c) . On film formation, all the bands (Soret band and Q band of the nln transitions) are red shifted by about 10-15 nm. For the Soret band, a... 

Anodic Electrochemical Oxidation. The anodic electropolymerization of thiophene presents several distinct advantages such as the absence of catalyst, direct grafting of the doped conducting polymer onto the electrode surface (which is of particular interest for electrochemical applications), easy control of the film thickness by deposition charge, and possibility to perform a first in situ characterization of the growing process or of the polymer by electrochemical and/or spectroscopic techniques. 

Amperometric batch injection analysis also presents high potential for many applications. In this technique, a motorized pipette dispenses small volume of sample in a controlled way on the working electrode surface assuring the reproducibility of the signal. A study utilizing BIA and electrodes modified with the electropolymerized Mn-TSPP/silver nanocomposite was utilized for quantification of hydrazine in a very favorable potential (h-0.010 V vs. Ag/AgCl), in a wide concentration window (2.5 x 10 to 2.5 x 10 " mol L ). The repeatability (RSD = 0.84 %, for 30 repetitions), detection limit (3.1 x 10 mol L ), and... 

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