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

Abstract

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) (OAPS) 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(NH 3) 3+ 6 and the anionic Mo(CN) 4− 8 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. RuO 2− 4, PtCl 2− 4, PdCl 2− 4, Fe(CN) 3− 6, SiW 12O 4− 40 polyoxometallate, 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) disodium salt (ABTS) or anthraquinone sulfonate (AQS). The apparent diffusion coefficient of Mo(CN) 4− 8 varies from 4 × 10 −10 to 8 × 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 RuO 2− 4, ABTS and AQS as electroactive immobilized species.