| Abstract
| - Cyclic voltammetry and chronoamperometry have beenused to characterize the translational mobility of eightdifferent redox probes trapped in hydrated silica gelmonoliths and evaluate the extent of surface interactions.The redox probes, selected for their size and charge, wereintroduced into a silica sol prepared by the acid-catalyzedhydrolysis of tetramethoxysilane along with an ultramicroelectrode (r = 13 μm) and a Ag/AgCl reference/counter electrode. Relative changes in the magnitude ofthe Faradaic current, the half-wave potential, E1/2, andthe apparent diffusion coefficient (D) were evaluated foreach redox probe as the sol gelled, aged, and dried.Significant variations were observed in the diffusion ratesbetween molecules of similar size and structure butvarying ionic charge. Large shifts in the redox potentialwere also observed, with the direction of shift dependenton the entrapped reagent. These results demonstrate theimportance of internal surface interactions versus surfaceconfinement in wet and partially dried sol−gel glasses.
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