Nanocomposite materials based on organopolysiloxane/macrocyle systems for electrochemical sensors

Hybrid inorganic–organic nanocomposite materials are prepared via sol–gel from γ-metacryloxypropyltrimetoxysilane (MAPTMS) and tetramethoxysilane (TMOS) precursors of a organopolysiloxane matrix in which ionophore ligands (crown-ethers: 12-crown-4, 15-crown-5 and 18-crown-6) are incorporated under controlled experimental conditions. Chemical analysis, FTIR and solid-state NMR (13C and 29Si) spectroscopies, TG and DTA thermal analyses and specific surface area determinations indicate that the ionophore remains homogeneously distributed in the organopolysiloxane network. Ion-selective electrodes are prepared by coating metal substrates with gels to form homogeneous and continuous thin xerogel films. Impedance and potentiometric techniques are applied for electrochemical characterisation of the sensors. The resulting electrodes are very sensitive towards alkaline metal ions giving linear potentiometric responses with near-Nernstian slopes in wide cation concentration ranges. Additional advantages of this new type of sensors are better adhesion, sensibility, reproducibility, and detection limit compared to “conventional” (i.e., with internal solutions or PVC) electrodes.