Response of nanosized cobalt oxide electrodes as pH sensors Original Research Article

Nanosized cobalt oxide which was synthesized by thermal decomposition of the product yielded from the solid-state reaction of Co acetate with citric acid or oxalic acid was found to be a promising pH-sensitive material. Co oxide electrodes fabricated with the screen-printing technique could exhibit fast (less than 1 min) and stable pH response in aqueous solution. A Nernstian response and no hysteresis effect were observed in the pH range of 1–12 if the content of oxide in the printed ink was controlled properly (5–10%). In addition, this kind of electrode showed high selectivity to hydrogen ions in the presence of alkali ions. The effect of synthetic conditions for cobalt oxides and fabrication parameters of the electrodes on their pH response behaviors were discussed.