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