Characterization of organosilasesquioxane-intercalated-laponite-clay modified electrodes and (bio)electrochemical applications

Electrode surface modification by organo-inorganic layered coatings can be achieved readily by drying a completely delaminated laponite clay sol mixed with polycationic silasesquioxane oligomers. Oligosilsesquioxanes were syn thesized by hydrolytic polycondensation of trialkoxysilanes bearing an alky lamino or alkyltrimethylammonium function. Films of excellent quality with exceptional adhesion and mechanical properties can be obtained. The interca lation of organosiloxane oligomers is accompanied by the expansion of the h im and by the existence of a mesoporosity as shown by XRD measurements and N-2 adsorption experiments. The ion-exchange properties of the resulting co atings as well as permeation of neutral molecules were studied in aqueous a nd non-aqueous electrolytes as a function of the oligomer loading. For olig omer loadings higher than the cation-exchange capacity (cec) of laponite, t he coatings behave as anion-exchangers which allows the binding a wide rang e of redox anions. Incorporated anions remain electroactive not only in aqu eous but also in non aqueous electrolytes as a consequence of a fixed pore size and permanent interlayer spacing of oligomer-expanded laponite. On the other hand intercalation of oligomers allows us to modulate the permeabili ty of the coating as shown by permeation experiments using neutral electroa ctive probes in non aqueous electrolytes. In the held of electroanalysis, a mperometric biosensors made by the entrapment of glucose oxidase inside the hybrid material have been investigated successfully. Such enzymatic films exhibit enhanced analytical performances as compared with those obtained us ing native sodic laponite. The potential applications of this new hybrid ma terial in the field of electrocatalysis have been exemplified by the electr oprecipitation of catalytic nanoparticles such as Pt(0) obtained from the i ncorporation of the anionic precursor PtCl42-. (C) 1998 Elsevier Science S. A. All rights reserved.