Solid-state reference electrodes conducting polymers

In recent years, the so-called solid-state reference electrodes have been developed for application in solution electrochemistry. In these electrodes, an electron conducting element (e.g. a silver wire or a silver layer) is first covered with a solid salt layer (e.g. silver chloride) and then with a second solid salt/polymer layer (e.g. a mixture of silver chloride and potassium chloride in PVC) Finally, the electrode is covered with a polymer, for instance cellulose acetate is deposited (cf. Fig. III.2.5) [21]. The influence of the polymer on the properties of such electrode was investigated by Lee et al. [22]. Because these electrodes can be fabricated in a very small size and because only small amounts of the electrolyte are dissolved, these electrode systems are often used in microelectrode arrangements for medicinal measurements. 

Although all solid state reference electrodes based on conducting polymers have been tested, they are still in the testing phase. The most promising systems appear to be bilayers with different ion-exchanger properties such as glassy carbon/polypyrrole in conjunction with a polypyrrole(polystyrene sulfonate) layer 64,65). 

Solid-state electrodes include devices in which the inner solution has been completely eliminated. The solution can be replaced with an all-polymer membrane formed directly on a metal reference electrode (CWE) a system of plasticized PVC (BMSA) or a substance with ionic-electron conductivity, a conductive polymer (SC ISE). 

Again we select a few references which are closely related to reactions or complexes studied in solution. A study of spinel systems of the type M cFe3 x04, with M = Cu(II), Cd(II), Ti(IV) shows that with x < 0.5, these have the characteristics of Fc304, but with x > 0.6 they are semiconductors, implying localization of the Fe(II) oxidation state. An important method of measuring conductivity in solids is to deposit the solid as a film on an electrode in solution. In a recent paper. Pickup and Murray review earlier studies of this type, and report new data on Os and Fe polypyridine polymers coated on platinum. As the potential is varied, conductivity sets in near the value for the M(III/II) couple, and reaches a maximum when the overall composition is 50% M(III) and 50% M(II). ... 

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