Organobase assisted synthesis of Co(OH)2 nanosheets enriched with oxygen vacancies for nonenzymatic glucose sensing at physiological pH

Herein, a two-dimensional (2D) Co(OH)2 nanosheet (NS) was prepared by reacting Co(II) acetate with 2-ethylimidazole and trimethylamine at room temperature. The as-prepared Co(OH)2 NS-modified screen-printed electrode enabled glucose sensing in human blood plasma samples (HBP) diluted with phosphate buffer saline (PBS, pH 7.4) and NaOH (0.1 M, pH 13.0) solutions. The electrocatalytic activity of Co(OH)2 NS for glucose oxidation in a wide pH range can be ascribed to the enriched oxygen vacancies with a high surface area of the porous NS, which enabled the facile formation of CoII/CoIII redox pair. The oxidation current response as a function of glucose concentration displayed two straight lines in the ranges 55.12–117.50 μM and 180–12055 μM in PBS diluted HBP, and 62.80–180 μM and 305–12055 μM in NaOH diluted HBP with the sensitivity of 430 and 98.18 μA/cm2/mM and the limit of detection of 0.082 and 2.2 μM, in PBS and NaOH diluted HBP solutions, respectively. The sensor also exhibited good long-term stability, repeatability, and interference-free signals. The good analytical performance of the proposed sensor demonstrates the suitability of Co(OH)2 NS as a material to fabricate disposable systems for the direct detection of glucose in human body fluids at physiological pH.