Superior non-enzymatic glucose sensing properties of Ag-/Au-NiCo2O4 nanosheets with insight from electronic structure simulations

Abstract

Ag-/Au-NiCo₂O₄ nanosheets were synthesized by a facile electrodeposition approach on conducting Ni foam, and their non-enzymatic glucose sensing performance was investigated. The hybrid nanosheets of NiCo₂O₄ and noble-metal nanoparticles supported on conductive Ni foam possessed high active surface area along with intrinsic electrocatalytic and biocatalytic properties and promoted electronic/ionic transport in the electrodes, leading to improved glucose sensing properties. The sensitivity of the bare NiCo₂O₄ nanosheets for electrochemical non-enzymatic glucose sensing was 20.8 μA μM⁻¹ cm⁻², whereas the NiCo₂O₄-Ag and NiCo₂O₄-Au nanosheet electrodes exhibited enhanced sensitivities of 29.86 and 44.86 μA μM⁻¹ cm⁻², respectively, with lower response times in the same linear range of 5–45 μM. We also performed density functional theory simulations to corroborate our experimental observations by investigating the interactions and charge-transfer mechanism of glucose on Ag- and Au-doped NiCo₂O₄. As Au is bound more strongly to the NiCo₂O₄ surface compared to Ag, the binding energy of glucose is greater on the Au-doped NiCo₂O₄ surface than on the Ag-doped NiCo₂O₄ surface, and Au doping makes NiCo₂O₄ more conductive compared to Ag doping. Thus, it can be theoretically inferred that Au-doped NiCo₂O₄ has better glucose sensing performance, which supports our experimental data.