Synthesis of cobalt oxide thin films in the presence of various anions and their application for the detection of acetaminophen

Cobalt oxide (Co₃O₄) modified electrode was prepared by growing layered cobalt carbonate hydroxide (LCCH) on a conducting glass using chemical bath deposition (CBD) and then by transforming the LCCH into Co ₃O₄ through pyrolysis. Cobalt sources with four different anions, i.e., cobalt chloride, cobalt nitrate, cobalt acetate, and cobalt sulfate, were used in CBD to obtain the films of LCCH. The composition and grain size of these films were verified by X-ray diffraction; their morphologies were examined by scanning and transmission electron microscopic images. Four distinctly different nanostructures of Co₃O₄ films, including straight acicular nanorods, bending acicular nanorods, nanosheets, and net-shaped nanosheets, were obtained only by changing the anions of the cobalt sources used in CBD. The electrodes with these films were used as sensors to detect acetaminophen (AP). Electrochemical impedance spectra were used to discuss the effect of morphology of the film on its electrocatalytic activity. The amperometric sensor toward AP, using the film of Co₃O₄ straight acicular nanorods, achieved a remarkable linear range of 10-6000 μM, a high sensitivity of 223.6 μA cm^-2 mM^-1, and a detection limit of 1.18 μM. The Co₃O₄ sensor was also used to detect AP in commercial tablets and cold powders.