Probing the shape-specific electrochemical properties of cobalt oxide nanostructures for their application as selective and sensitive non-enzymatic glucose sensors

Abstract

In this work, a selective and sensitive non-enzymatic electrochemical glucose sensor was developed using cobalt oxide nanoflowers (NF). Herein, for the first time, shape-specific electrochemical properties of cobalt oxide nanostructures were studied by synthesizing the spherical nanoparticle (NP), porous nanorod (NR) and nanoflower (NF) shapes of cobalt oxide by easy and facile wet-chemical processes. Cobalt oxide nanoflowers showed high surface-to-volume ratio with superior electrocatalytic behavior, and therefore, are more suited for designing a selective and sensitive non-enzymatic glucose sensor. All the as-synthesized samples are characterized using different spectroscopic and microscopic techniques. Prior to sensor fabrication, the nanostructures are further analyzed using voltammetric techniques for the determination of electroactive/real surface area and electrode parameters. The cobalt oxide nanoflowers exhibit maximum electrocatalytic activity owing to the larger exposure area resulting from its unique 3-D hierarchical architecture with interconnected nanosized petals. The influence of supporting electrolyte, electrolyte concentration and applied potential on the electrooxidation of glucose on cobalt oxide nanoflower-modified pencil graphite electrode (NF-PGE) sensor is examined, and the mechanism is explained. The developed amperometric glucose sensor exhibits excellent anti-interfering property and two wide linear ranges of 5 to 60 μM and 0.2 to 3.0 mM, with high sensitivities of 693.02 μA mM⁻¹ cm⁻² and 228.03 μA mM⁻¹ cm⁻² and detection limits (LOD) as low as 0.04 μM and 0.14 μM, respectively. Furthermore, the practical feasibility of the developed sensor was tested for the quantification of glucose in various commercially available soft drinks, fresh fruit extracts, and human blood samples via standard addition (SA) method.