RGO decorated N-doped NiCo2O4 hollow microspheres onto activated carbon cloth for high-performance non-enzymatic electrochemical glucose detection

Abstract

This paper reports the first effective fabrication of a high-performance non-enzymatic glucose sensor based on activated carbon cloth (ACC) coated with reduced graphene oxide (RGO) decorated N-doped urchin-like nickel cobaltite (NiCo₂O₄) hollow microspheres. Hierarchically mesoporous N-doped NiCo₂O₄ hollow microspheres were synthesized using a facile solvothermal method, followed by thermal treatment in a nitrogen (N₂) atmosphere. Subsequently, they were hydrothermally decorated with RGO nanoflakes. The resulting composite was dip-coated onto ACC, and its electrochemical and glucose sensing performances were investigated using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and chronoamperometric measurements in a three-electrode system. The composite electrode sensor demonstrates admirable sensitivity (6122 μM mM^-1 cm^-2) with an ultralow detection limit (5 nM, S/N = 3), and it performs well within a substantial linear range (0.5-1.450 mM). Additionally, it exhibits good long-term response stability and outstanding anti-interference performance. These outstanding results can be attributed to the synergistic effects of the highly electrically conductive ACC with multiple channels, the enhanced catalytic activity of highly porous N-doped NiCo₂O₄ hollow microspheres, and the large electroactive sites provided by its well-developed hierarchical nanostructure and RGO nanoflakes. The findings highlight the enormous potential of the ACC/N-doped NiCo₂O₄@RGO electrode for non-enzymatic glucose sensing.

Keywords: Composite; Glucose detection; N-doping; NiCo2O4; Non-enzymatic; RGO.

Fig. 1

XRD patterns of HN@R and N₁₀₀–HN@R urchin-like microspheres.

Fig. 2

FESEM images of (a–c) HN@R and (d–f) N₁₀₀–HN@R urchin-like microspheres at various magnifications.

Fig. 3

(a) EDS spectrum (b) FE-SEM image, (c) EDS layer image, and the EDS mapping of (d) O (e) Co, (f) Ni, (g) C elements and (h) N N₁₀₀–HN@R urchin-like microspheres.

Fig. 4

Pore size distribution curves of (a) HN@R and (b) N₁₀₀–HN@R urchin-like microspheres.

Fig. 5

(a) Survey XPS spectra, and High-resolution XPS spectra corresponding to (b) Co 2p, (c) Ni 2p, (d) O 1s, (e) N 1s, and (f) C 1s C 1s core levels of N₁₀₀–HN@R microspheres.

Fig. 6

(a) Electrochemical impedance spectroscopy (EIS) study (Nyquist plot) of ACC/HN, ACC/HN@R, and ACC/N₁₀₀–HN@R electrodes at 100 kHz–1 Hz under 0.01 V; (b) The fitted EIS plot for the ACC/N₁₀₀–HN@R electrode with corresponding impedance equivalent circuit. The inset table provides the values for each component of the equivalent circuit.

Fig. 7

Cyclic voltammetry curves of (a) ACC/HN@R, and (b) ACC/N₁₀₀–HN@R electrodes at various scan rates under 0 to +0.6 V potential window; Cyclic voltammetry results of glucose oxidation on (c) ACC/HN@R, and (d) ACC/N₁₀₀–HN@R electrodes with a glucose concentration range of 0–3 mM in 2 M KOH at 49 mV/s; the anode peak current and the glucose concentration relationship for (e) ACC/HN@R, (f) ACC/N₁₀₀–HN@R electrodes as obtained from cyclic voltammetry curves shown in Fig. (c) and (d), respectively.

Fig. 8

The amperometric response of the electrodes (a–d) ACC/HN@R and (e–h) ACC/N₁₀₀–HN@R to the successive injections of 28 μM glucose into 0.1 M KOH solution at various potentials in the range of 0.40–0.60 V. (Rotation speed = 200 rpm).

Fig. 9

Linear fit curve of glucose concentration (mM) vs. steady-state current response (μA) for (a) ACC/HN@R and ACC/N₁₀₀–HN@R electrodes; E_app = 0.40–0.60 V; Rotation speed = 200 rpm. Both plots indicate that 0.55 V is the optimum starting potential with which the electrode sensors have maximum sensitivity.

Fig. 10

(a, b) The amperometric response and respective (c, d) linear fit curves of concentration of glucose (mM) vs. steady-state current response (μA) of ACC/N₁₀₀–HN@R electrode sensor at E_app = 0.55 V for (a) low and (b) high concentration glucose injections into 0.1 M KOH solution (Rotation speed = 200 rpm).

Fig. 11

Interference test of the ACC/N₁₀₀–HN@R electrode sensor in 0.1 M KOH with different concentrations of glucose and other interfering species as indicated.

Fig. 12

Glucose sensing response stability of ACC/N₁₀₀–HN@R electrode sensor at E_app = 0.55 V for 18 days. Inset images show the first day and final day response against the 28 μM glucose injection into 0.1 M KOH solution.