Study of the potentiometric response towards sodium ions of Na0.44−xMnO2 for the development of selective sodium ion sensors

Single phase Na0.44MnO2 powder was synthetized by a classical solid-state reaction. Using a plastic technology, we studied the potentiometric response versus Na+ ions in aqueous medium. A Nernstian-like response (55 mV/dec) was obtained for concentrations ranging from 1 M to 2 × 10−4 M with a quite good selectivity towards Li+, K+, Mg2+ and Ca2+. Through an ageing study of this material in aqueous solution, we clearly identified the sensing material as being the Na0.33MnO2 phase. Furthermore, we proved that the sensing activity of this compound is routed in its ability to reversibly insert/de-insert Na+ ions.