Effect of oxygen content in CuO x nanofilms on chloride ion detection for ion sensor applications

Abstract

Sensors for detecting chloride ions have been required for routine monitoring of industry and human health. This study proposes a concept of an ion sensor based on CuOx nanofilms with different oxygen contents. The CuOx-based sensors exhibited an increase in DC current for those with low oxygen content and a decrease for those with high oxygen content following exposure to a chloride ion solution. AC impedance analysis suggested differential reactions of chloride ions in the bulk and surface regions of CuOx, dependent on the oxygen content. For the CuOx-based sensors with a ratio of 0.78 oxygen to copper atoms at chloride ion concentrations of 10−1000 ppm, the sensitivity in the bulk region calculated from AC impedance was 61−2926, which was higher than the sensitivity of 1.3−2.6 calculated from DC impedance. Finally, CuOx-based sensors demonstrated identifiability for chloride ions compared to sodium and calcium ions.