Laser-Induced Graphene Decorated with MOF-Derived NiCo-LDH for Highly Sensitive Non-Enzymatic Glucose Sensor

Abstract

Designing and fabricating a highly sensitive non-enzymatic glucose sensor is crucial for the early detection and management of diabetes. Meanwhile, the development of innovative electrode substrates has become a key focus for addressing the growing demand for constructing flexible sensors. Here, a simple one-step laser engraving method is applied for preparing laser-induced graphene (LIG) on polyimide (PI) film, which serves as the sensor substrate. NiCo-layered double hydroxides (NiCo-LDH) are synthesized on LIG as a precursor, utilizing the zeolitic imidazolate framework (ZIF-67), and then reacted with Ni(NO₃)₂ via solvent-thermal methods. The sensitivity of the non-enzymatic electrochemical glucose sensor is significantly improved by employing NiCo-LDH/LIG as the sensing material. The porous and interconnected structure of NiCo-LDH, derived from ZIF-67, enhances the accessibility of electrochemically active sites, while the incorporation of LIG ensures exceptional conductivity. The combination of NiCo-LDH with LIG enables efficient electron transport, leading to an increased electrochemically active surface area and enhanced catalytic efficiency. The fabricated electrode achieves a low glucose detection limit of 0.437 μM and demonstrates a high sensitivity of 1141.2 and 631.1 μA mM^-2 cm^-2 within the linear ranges of 0-770 μM and 770-1970 μM, respectively. Furthermore, the NiCo-LDH/LIG glucose sensor demonstrates superior reliability and little impact from other substances. A flexible integrated LIG-based non-enzymatic glucose sensor has been developed, demonstrating high sensitivity and suggesting a promising application for LIG-based chemical sensors.

Keywords: NiCo-LDH; ZIF-67; flexible; glucose sensor; laser-induced graphene.

Figure 1

Three-dimensional view of the conductivity of LIG under different laser parameters.

Figure 2

(a) NiCo-LDH/LIG preparation process diagram. Low- and high-resolution SEM images of the (b,f) LIG, (c,g) Co-MOF/LIG, (d,h) and NiCo-LDH/LIG. (e,i) Low- and high-resolution TEM images of the NiCo-LDH.

Figure 3

(a) LIG’s adsorption/desorption isotherm and pore size distribution. (b) NiCo-LDH/LIG’s adsorption/desorption isotherm and pore size distribution.

Figure 4

(a) XRD patterns of the LIG, Co-MOF/LIG, and NiCo-LDH/LIG. XPS spectra of the NiCo-LDH in the (b) survey spectrum, (c) Ni 2p, and (d) Co 2p.

Figure 5

(a) CV curves for LIG and NiCo−LDH/LIG in 0.1 M NaOH, with and without 1 mM glucose, were recorded at a scan rate of 10 mV/s. (b) CV curves of NiCo−LDH/LIG were obtained in solutions with 0, 1, 2, and 3 mM glucose at a scan rate of 10 mV/s. (c) Current responses of five successive injections of 500 μM glucose at different applied voltages. (d) The linear fitting results with error bars.

Figure 6

(a) Comparative glucose titration experiments of NiCo-LDH/LIG, NiCo-LDH/Ag, Co-MOF/LIG, and Co-MOF/Ag at 0.5 V in 0.1 M NaOH solution. (b) Fitting curves with error bars for the comparative experiments.

Figure 7

(a) A series of amperometric I–t curves were recorded by sequentially adding different glucose concentrations (5, 10, 20, 50, 100, 200, and 400 μM, with each concentration tested twice) to a solution at an applied potential of 0.5 V using Ag/AgCl as the RE. (b) Linear fitting curve of the response current with glucose concentration, including error bars. (c) Low concentration enlargement of (a). (d) Low concentration fitting curve in (b). (e) Current responses of NiCo-LDH/LIG upon the addition of various different interferences. (f) Reliability test of NiCo-LDH/LIG over 7 days.

Figure 8

(a) Photograph of LIG patterns on PI and the integrated three-electrode glucose sensor device. (b) Amperometric I–t curves of successive additions of the same concentrations of glucose (400 μM) at an applied potential of 0.5 V. (c) Linear fitting curve of response current with glucose concentration.

Figure 9

(a) NiCo-LDH/LIG sensor was tested with synthetic blood and glucose solution in 0.1 M NaOH solution. (b) Comparison test of glucose with other sugars in 0.1 M NaOH solution.