Coating electropolymerization

A similar approach has been used to prepare PAn/PVA composites.73 In this case, the PVA is dip-coated using a DMSO solution, and the electropolymerization is initiated before the DMSO is completely removed. PAn has been electropolymer-ized74 onto a platinum electrode wrapped in an aromatic copolyamide. PAn-nafion composites can be prepared using the coating-electropolymerization method.75... 

To prepare polymer film electrodes there are different techniques like dip coating, spin coating, electropolymerization from monomers, and molecularly imprinted polymers (MIPs) developed very recently. They are often used for both potentiometric and amperometric ion sensors. Some feature of different types of ion sensors based on polymer CMEs are shown in Table 1. Conducting polymer-based CMEs... 

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... 

Polymeric films of [(//5-C s Me5)M(L)Cl]+complexes (M = Ir, Rh L = pyrrole-substituted bpy or phen) have been coated on an electrode by oxidative electropolymerization. The buildup of hydrido complexes in films is well known 27,28,30 the high electrocatalytic activity of these molecular electrode materials towards dihydrogen evolution in organic and aqueous electrolytes is also well known.25,31 For example, H2 is evolved at —0.55 V vs. SCE at a poly [(j75-C5Me5)-Rh(bpy)Cl]+ film in pH 1 aqueous solution.31... 

Asymmetric ECH with [Rh(L)2(Cl)2]+ complexes containing chiral polypyridyl ligands has been attempted, in homogeneous media (L = (7)-(12)) and at carbon electrodes coated with polymer films prepared by electropolymerization of [Rh(13)2(Cl)2]+ -61 62 The latter catalytic system gave the best results in terms of turnover number (up to 4,750) and enantiomeric excess, (ee) when applied to the hydrogenation of acetophenone (ee 18%) and 2-butanone (ee 10%).62 Polymeric materials derived from the complexes [RhI(bpy)(COD)]+ 36 and [Pd(bpy)2]2+33have also been applied to the ECH reaction. 

Most suitable for electrically conducting materials such as carbon fibers, the electrochemical processes involve deposition of polymer coatings on the fiber surface through electrodeposition or electropolymerization techniques. The major advantage of these processes is that a uniform layer of controlled thickness and variable polymer structure and properties can be obtained by controlling the current and the solution concentration. 

As described in Section 3 of Chapter 4, the stabilization of n-Si electrode by coating with poly(pyrrole) has attracted much attention. The stabilization of a small bandgap n-semiconductor electrode against oxidation is of great value not only to convert visible light into chemical energy, but also to construct liquid-junction solar cells operated under visible irradiation. The poly(pyrrole) film is usually electropolymerized on the semiconductor electrode dipped in the aqueous solution of pyrrole. The remarkable stabilizing effect of poly(pyrrole) film on polycrystalline n-Si is shown in Fig. 22 67). The photocurrent obtained under irradiation in the aqueous solution of... 

Cooke and coworkers have reported preparation of flavin-modified electrodes using a similar electropolymerization procedure.34 They have also studied electrodes coated with self-assembled monolayers (SAMs) formed from both flavin39 and phenanthrenequinone disulfides.59 The monolayers are stable in CH2C12 solution, and, as with the electrodes formed from 30, show redox-dependent binding behavior similar to that seen in solution. Interestingly, the phenanthrenequinone SAM... 

Figure 9 An illustration depicting the two methods of interface passivation used here, (a) Reaction (5) alone is inhibited by electropolymerizing a film of insulating PPO, polytp-henyleneoxide-co-2-allylphenyleneoxide), on the Sn02 substrate, (b) Both reactions (4) and (5) are inhibited by coating exposed oxide surfaces with poly(methylsiloxane).

Polymer films can also be electropolymerized directly onto the electrode surface. For example, Abruna et al. have shown that vinylpyridine and vinyl-bipyridine complexes of various metal ions can be electropolymerized to yield polymer films on the electrode surface that contain the electroactive metal complex (see Table 13.2) [27]. The electronically conductive polymers (Table 13.2) can also be electrosynthesized from the corresponding monomer. Again, a polymer film that coats the electrode surface is obtained [25]. Electropolymerized films have also been obtained from styrenic, phenolic, and vinyl monomers. 

For consistent and reproducible operation it is important to control chemosensor features like thickness of the MIP coatings. Generally, MIPs were prepared and immobilized on PZ resonators by using two distinct procedures, namely in situ assembling on the resonator surface [103] or physical entrapment of the preprepared MIP particles in an inert polymer matrix attached to this surface [21]. Typically, thickness of the polymer is 20 nm to 5 pm. In situ immobilization of MIPs (see below in Sects. 3.2.1-3.2.4) can be accomplished by surface grafting, sandwich casting, electropolymerization, physical entrapment or chemical coupling [102],... 

A molecularly imprinted polypyrrole film coating a quartz resonator of a QCM transducer was used for determination of sodium dodecyl sulphate (SDS) [147], Preparation of this film involved galvanostatic polymerization of pyrrole, in the presence of SDS, on the platinum-film-sputtered electrode of a quartz resonator. Typically, a 1-mA current was passed for 1 min through the solution, which was 0.1 mM in pyrrole, 1 mM in SDS and 0.1 M in the TRIS buffer (pH = 9.0). A carbon rod and the Pt-film electrode was used as the cathode and anode, respectively. The SDS template was then removed by rinsing the MlP-film coated Pt electrode with water. The chemosensor response was measured in a differential flow mode, at a flow rate of 1.2 mL min-1, with the TRIS buffer (pH = 9.0) as the reference solution. This response was affected by electropolymerization parameters, such as solution pH, electropolymerization time and monomer concentration. Apparently, electropolymerization of pyrrole at pH = 9.0 resulted in an MIP film featuring high sensitivity of 283.78 Hz per log(conc.) and a very wide linear concentration range of 10 pM to 0.1 mM SDS. 

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