Hexagonal cobalt oxide nanosheet-based enzymeless electrochemical uric acid sensor with improved sensitivity

Abstract

Enzymeless sensors have been known as highly stable, fast, and reliable devices for the detection of several biomolecules and for use in early disease diagnosis. Hence, it is crucial to fabricate enzymeless sensors with high sensitivity. Herein, we describe the synthesis of hexagonal cobalt oxide nanosheets using a hydrothermal method. The crystalline phase of the as-synthesised cobalt oxide nanosheets was examined using X-ray diffraction (XRD), and the morphology was observed using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The cobalt oxide nanomaterials were synthesised in a large quantity and showed a uniform and hexagonal nanosheet like morphology. To investigate their application, the nanosheet nanomaterial was utilised to fabricate an ultra-sensitive enzymeless electrochemical-based uric acid (UA) sensor on a screen-printed carbon electrode (SPCE). A paste of hexagonal cobalt oxide nanosheets in a conductive binder was drop-casted onto the working electrode of the SPCE. The cobalt oxide nanosheet-based UA sensor showed a good response for UA detection. Under optimal conditions, the cobalt oxide/SPCE UA sensor showed linearity up to 200 μM of UA with ultra-sensitivity (1560 μA mM⁻¹ cm⁻²) and a limit of detection of ∼5 μM. Furthermore, the fabricated UA sensor was subjected to reproducibility, storage stability, and selectivity tests, which confirmed good stability, reproducibility, and specificity for UA. The developed ultra-sensitive enzymeless UA sensor is expected to be useful for the sensing of UA in real samples.