ELECTROCHEMICAL MICROSENSOR FOR THE DETECTION OF NA+ IONS

Thin vitreous films were elaborated by microelectronic techniques (vacuum evaporation, r.f. sputtering) and structural and electrical properties were characterized respectively by X-ray diffractometry and complex impedance spectroscopy measurements. Morphology and composition of thin films were examined by scanning electron microscopy with energy dispersive spectroscopic microprobe. Based on these thin films, Na+-selective microsensors were built up with a sodium aluminosilicate glass as the sensitive membrane and thin film of borophosphate as the ionic bridge acting as an interfacial layer providing an ionic and electronic exchange between the collector and the sensitive membrane. Electrochemical behaviour and sensitivity results regarding the microsensor were investigated. Microsensors exhibit near-Nernstian response in the Na+-concentration range of 10(-1)-10(-4) mol/l with a detection limit close to 5X10(-4) M and good reproducibility.