Amperometric determination of NADH with Co3O4 nanosheet modifiedelectrode

In this work, we have developed a simple and reliable cobalt oxide (Co3O4) based amperometric sensor for the determination of NADH. A sheet shape Co3O4 nanooxide was synthesized by the CTAB assisted hydrothermal technique and was characterized by SEM and XPS. Owing to the redox property of Co3O4, the operating potential of NADH can be significantly reduced from 0.7down to 0.1 V. Compared to a commercial Co3O4 nanoparticle modified electrode, this nanosheet form cobalt oxide possesses a rapid background subsiding characteristic and a low residual current. This scheme was conducted on a flow injection system with a constant operating potential of 0.1 V (vs. Ag/AgCl, 3 M) in a 0.2 M phosphate buffer at pH 6.0. A suitable linear range from 10 to 100 μM (R=0.999) with a detection limit of 4.25 μM (S/N=3) was obtained. The RSD for 20 successive measurements of 75 μM NADH is only 1.4%, which indicates a high stability and no contamination during NADH oxidation. This scheme did not suffer from conventional antioxidants, including dopamine, uric acid, epinephrine, serotonin, histamine, and 4-acetaminophen, except ascorbic acid. Thus, an ascorbate oxidase was introduced to remove the ascorbic acid before the sample was injected into the flow injection analysis system. After this simple pretreatment, the influence of ascorbic acid was eliminated, successfully.

► A Co3O4 nanosheet based amperometric sensor was developed for sensing the NADH.
► The detailed mechanism between Co3O4 NADH and O2 was elucidated.
► Operating potential of NADH could be reduced from 0.7to 0.1 V.
► Suitable linear ranges from 10 to 100 μM at 0.1 V were achieved.