Materials prepared by sol-gel chemistry as platforms for analytical chemistry: Solid-state electrolytes and encapsulation hosts

The overall goal of our research is to investigate advances in sol-gel chemistry using electroanalytical methodology. Here, sol-gel materials have been used as solid-state electrolytes and encapsulation hosts for electrocatalysts. The voltammetry of phosphotungstic acid (PTA) immobilized in solids prepared by the sol-gel process was investigated. The general voltammetric behavior of PTA in sol-gels is the same as that for PTA in solution. When Triton X-114 is included above its critical micelle concentration, cmc, in the sol, the resulting gel structure is changed as reflected by apparent diffusion coefficients for PTA. Atomic force microscopy of these solids indicate that high concentrations of surfactant change the resulting gel structure. These observations are consistent with recent reports on the templating of the internal structure of silica by micelles.; A templated base-catalyzed sol-gel process was used to prepare solid electrolytes for gaseous H₂O₂. A determination with a 60-min preconcentration time and differential pulse voltammetry provided a detection limit of 10.2 ppbv H₂O₂. Including Triton X-114 well above its cmc and MgCl₂ in the sol increased the sensitivity.; Mesoporous silica prepared by a templated sot-gel process was used as the electrolyte for amperometric determination of gaseous monomethyl hydrazine. Three detection strategies were tested, namely cyclic voltammetry with the oxidation mediated by FeII,III, pulsed electrochemical detection, and potentiostatic oxidation at a mixed-valence ruthenium oxide (mvRuOx) film on a Pt electrode. A three-phase boundary cell design and measurement at a mvRuOx-modified electrode yielded a detection limit of 5 ppb and provided a range of humidity-independent responses.; A metallodendrimer with RuIIterpyridine units was synthesized and demonstrated to be a mediator for the electrochemical oxidation of methionine, cystine, and insulin. A reversible oxidation of RuII centers in the metallodendrimer was observed both as a solute in mixed acetonitrile-water solvents and as a component of carbon-based conducting composite electrodes where sol-gels served as encapsulation hosts.; The voltammetry of ruthenium coordination complexes that were covalently attached to sol-gel precursors was investigated. Complexes prepared to contain a terpyridinyl ligand and pyridine ligands mediated the oxidation of As III and methionine.