K+ SENSITIVE BILAYER SUPPORTING ELECTRODES

A K+ sensor based on the admittance change of synthetic bilayer membranes supported on Si/SiO2 electrodes is reported. The membrane is formed on thermally oxidized silicon derivatized with (3,3'-dimethylbutyl)dimethyl(dimethylamino)silane by the self-assembly of distearoylphosphatidylcholine and tetradecyl-18-crown-6 from ethanol+H2O solutions or by the transfer of a compressed mixed monolayer film from a Langmuir trough. The electrode impedance is measured, which is almost completely capacitive, and a simple equivalent circuit is presented to describe the frequency dependence of the data. The admittance of this electrode-supported membrane was found to be modulated by the concentration of K+. Monitoring these admittance changes allows a simple and specific technique for the measurement of potassium ions in solutions. The sensor has a detection limit of ca. 1 × 10-6 M, a useful range between 10-6 M to 10-2 M, and a fast response time. © 1990.