A new silver-ion selective sensor based on a polythiacrown-ether entrapped by sol-gel

We report a new electrode based on a selective complexing agent for Ag+ ions, the 6-oxa-3,9-dithiabicicle[9.3.1]pentadeca-1(15).11,13-triene (MAO), incorporate into an organopolysiloxane matrix prepared via sol-gel from a mixture of gamma-methacryloxypropyltrimetoxysilane (MAPTMS) and tetramethoxysilane (TMOS). The modified electrode is prepared by coating the surface of graphite electrodes with a thin film of the nanocomposite material. SEM and EDX were used to determine the continuous coverage and composition of the films constituting the active phase of the electrodes. The application of electrochemical impedance spectroscopy (EIS) and potentiometric techniques, allows establishing the selective response of the electrode towards the Ag+ ions. The selectivity over other cations as Cd2+, Pb2+, NH4+, Na+, etc. is explained by the molecular recognition character of the electrode introduced by the presence of the MAO ionophere into the xerogel film. These new hybrid organic-inorganic systems constitute an alternative to classical PVC-matrices for preparation ion-selective electrodes showing also additional advantages such as higher reproducibility, lifetime, detection limits and adhesion with the electrode. (C) 2002 Elsevier Science Ltd. All rights reserved.