This work reports
a highly sensitive and selective nonenzymatic
detection of glucose that has been achieved by hybridization of 1D
α-MnO2 nanorods modified with surface decoration
of Co3O4 nanoparticles. The rational design
and controlled synthesis of the hybrid nanostructures are of great
importance in enabling the fine tuning of their properties and functions.
First-principles-based periodic hybrid unrestricted HSE06 DFT with
Grimme’s long-range dispersion corrections are employed to
compute the equilibrium crystal structures and electronic properties
(i.e., band structure, Fermi energy level, and density of states)
of both materials. These calculations reveal that both the α-MnO2 and the Co3O4 materials are indirect
band gap semiconductor, and the band gap is about 2.89 and 3.18 eV,
respectively. The α-MnO2/Co3O4 hybrid nanostructure has been synthesized by a simple and economical
hydrothermal method. Compared with the performances of pure components
MnO2 nanorods and Co3O4 nanoparticles,
these hybrid nanostructures demonstrated a maximum electrooxidation
toward glucose. The glucose-sensing performances of fabricated hybrid
structures were measured by cyclic voltammetry (CV) and chronoamperometry.
The synthesized α-MnO2/Co3O4 electrode exhibited a high sensitivity of 127 μA mM–1 cm–2 (S/N = 3) with a detection limit of 0.03
μM, wide linear range from 60 μM to 7 mM of glucose, with
a short response time of less than 5 s. The favorable properties of
the nanostructure fortify its potential utilization in the clinical
detection of diabetes.
The thermally stable and crystalline 2D layered mesoporous hexagonal platelets of cobalt oxide (CoO) with (111) facets were prepared by using the template-free wet chemical synthesis approach. The high surface energy (111) facets known for a highly electroactive surface are expected to enhance the electrochemical properties, especially the rate capability. The highly crystalline CoO with an average particle size of 25 nm formed a 2D mesoporous layered structure, with an average thickness of ∼40 nm, a pore size of 8-10 nm, and a specific surface area of 45.68 m g promoting large surface confined electrochemical reaction. The 2D layered mesoporous CoO exhibits a maximum specific capacity of 305 mA h g at a scan rate of 5 mV s and 137.6 mA h g at a current density of 434.8 mA g. The maximum energy and power densities of 32.03 W h kg and 9.36 kW kg, respectively, are achieved from the 2D hexagonal platelets of mesoporous CoO nanoparticles with (111) facets. An excellent ultra-high rate capability of ∼62% capacity retention was observed after increasing the discharge current density from ∼434.8 mA g to 43 480 mA g. Furthermore, a cycling stability of 81.25% was achieved even after 2020 charge-discharge cycles at a current density of 12 170 mA g. This high performance and ultra-high rate capability could be attributed to the (111) facets 'crystal plane' effect of CoO. Our results presented here confirm that the 2D mesoporous layered hexagonal platelets of CoO exhibit "battery-mimic" behaviour in an aqueous electrolyte of KOH.
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