Inorganic Sensing Using Organofunctional Sol–Gel Materials

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Abstract
This Account describes recent work in the development and applications of sol–gel sensors for concentrated strong acids and bases and metal ions. The use of sol–gel films doped with organic indicators for the optical sensing of concentrated strong acids (HCl, 1–10 M) and bases (NaOH, 1–10 M) has been explored, and the development of dual optical sensor approaches for ternary systems (HCl–salt–H2O and NaOH–alcohol–H2O) to give acid and salt, as well as base and alcohol, concentrations is discussed. The preparation of transparent, ligand-grafted sol–gel monoliths is also described, and their use in the analysis of both metal cations (Cu2+) and metal anions [Cr(VI)] is presented. A new model using both metal ion diffusion and immobilization by the ligands in such monoliths has been developed to give metal concentrations using the optical monolith sensors. In addition to optical sensing, a method utilizing ligand-grafted sol–gel films for analyte preconcentration in the electrochemical determination of Cr(VI) has been explored and is discussed.