Facile preparation of a CoNiS/CF electrode by SILAR for a high sensitivity non-enzymatic glucose sensor

Abstract

The nanomaterials for non-enzymatic electrochemical sensors are usually pre-synthesized and coated onto electrodes by ex situ methods. In this work, amorphous cobalt-nickel sulfide (CoNiS) nanoparticles were facilely prepared on copper foam (CF) by the in situ successive ionic layer adsorption and reaction (SILAR) method, and as-prepared CoNiS/CF was studied as an electrode for non-enzymatic glucose sensing. It was analyzed by field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDAX) and X-ray photoelectron spectroscopy (XPS). The electrochemical performance was investigated by cyclic voltammetry (CV) and chronoamperometry (CA). This binary sulfide electrode showed better performance toward glucose oxidation compared to the corresponding single sulfide and showed a wide linear range of 0.005 to 3.47 mM, a high sensitivity of 2298.7 μA mM^-1 cm^-2 and a low detection limit of 2.0 μM. The sensor exhibited high sensitivity and good repeatability and stability and was able to detect glucose in an actual sample. This work provides a simple and fast in situ electrode preparation method for a high-sensitivity glucose sensor.

Fig. 1. Schematic of the fabrication of a CoNiS/CF electrode by the SILAR method.

Fig. 2. TEM and SEM images and EDS of the CoNiS/CF electrode at (a) 600 nm scale, (b) 200 nm scale, (c) 5 μm scale, (d) 500 nm scale. (e) EDS spectrum, and (f) EDS mapping images of Ni, Co, S in scanned area.

Fig. 3. XPS spectra of the CoNiS/CF electrode: (a) survey spectrum, (b) Ni 2p, (c) Co 2p and (d) S 2p.

Fig. 4. (a) CVs of bare CF, NiS/CF, CoS/CF, and CoNiS/CF with and without 0.5 mM glucose in 0.1 M NaOH at a scan rate of 20 mV s⁻¹. (b) Oxidation peak currents of CoS/CF and CoNiS/CF with different Co/Ni feeding ratios. (c) Amperometric responses of the CoNiS/CF electrode with successive injections of 0.5 mM glucose at different potentials. (d) CVs of CoNiS/CF with different concentrations of glucose in 0.1 M NaOH at a scan rate of 20 mV s⁻¹.

Fig. 5. (a) CVs of the CoNiS/CF electrode in 0.1 M KOH containing 0.3 mM glucose at different scan rates (20–120 mV s⁻¹). (b) Linear relationship between the oxidation/reduction peak current and square root of scan rate.

Fig. 6. Amperometric response of CoS/CF, NiS/CF and CoNiS/CF electrodes to glucose in 0.1 M NaOH under 0.6 V (a), and the corresponding linear relationship between the glucose concentration and current response of CoNiS/CF (b), CoS/CF (c), NiS/CF (d).

Fig. 7. (a) Amperometric curves of the CoNiS/CF electrode with the successive addition of 0.1 mM of glucose, 0.01 mM of UA, AA, DA and cysteine in 0.1 M NaOH. (b) Amperometric currents of five pieces of independent CoNiS/CF electrodes towards 0.5 mM glucose. (c) Stability of CoNiS/CF electrodes to 0.6 mM glucose tested every 5 days for 25 days.