Organosilasesquioxane-laponite clay sols: A versatile approach for electrode surface modification

Electrode surface modification by organo-inorganic layered coatings can be readily achieved by drying a completely delaminated laponite clay sol mixed with neutral octa(3-aminopropylsilasesquioxane) (GAPS) cubane-like octameric pillar precursors. Films of excellent quality with exceptional adhesion and mechanical properties could be obtained. Under mild acidic conditions, protonation of the octamer amino groups occurs. 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 probes. For octamer loadings higher than the cation exchange capacity (cec) of laponite, the octamer-laponite coating behaves as an anion exchanger which allows the efficient incorporation of a wide range of redox anions, e.g. Ru)(4)(2-), PtCl42-, PdCl42-, Fe(CN)(6)(3-), SiW12O404- polyoxometallate, 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) disodium salt (ABTS) or anthraquinone sulfonate (AQS). The apparent 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 original use of such a modified electrode to operate in organic medium has been examined with RuO42-, ABTS and AQS as electroactive immobilized species.