ORGANOSILASESQUIOXANE-LAPONITE CLAY SOLS - A VERSATILE APPROACH FOR ELECTRODE SURFACE MODIFICATION

Electrode surface modification by organo-inorganic layered coatings ca n be readily achieved by drying a completely delaminated laponite clay sol mixed with neutral octa(3-aminopropylsilasesquioxane) (GAPS) cuba ne-like octameric pillar precursors. Films of excellent quality with e xceptional adhesion and mechanical properties could be obtained. Under mild acidic conditions, protonation of the octamer amino groups occur s. The ion-exchange properties of the resulting coatings were studied in aqueous electrolyte as a function of the octamer loading using the cationic Ru(NH3)(6)(3+) and the anionic Mo(CN)(8)(4-) electroactive pr obes. For octamer loadings higher than the cation exchange capacity (c ec) of laponite, the octamer-laponite coating behaves as an anion exch anger which allows the efficient incorporation of a wide range of redo x anions, e.g. Ru)(4)(2-), PtCl42-, PdCl42-, Fe(CN)(6)(3-), SiW12O404- polyoxometallate, 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic ac id) disodium salt (ABTS) or anthraquinone sulfonate (AQS). The apparen t diffusion coefficient of Mo(CN)(8)(4-) varies from 4 x 10(-10) to 8 x 10(-10) depending on the amount of intercalated octamer. The origina l use of such a modified electrode to operate in organic medium has be en examined with RuO42-, ABTS and AQS as electroactive immobilized spe cies.