## 5 Graphene-Based Electrode for Non-Enzymatic Glucose Biosensor
However, the up to 80 mM linear range of the 3D graphene/Co\({}_{3}\)O\({}_{4}\) nanowire electrode is much smaller than those of both [PERSON]'s and [PERSON]'s biosensors. The biosensor showed a capability for glucose detection in micro-droplets within the linear concentration range of 50-300 mM. [PERSON] et al. [140] used an Ni nanoparticle-decorated reduced graphene oxide (Ni-NPs/rGO) to detect the glucose. The electrode has shown excellent electrochemical properties for GOx with a linear range of 0.25-1200 \(\upmu\)M and a detection limit of 0.01 \(\upmu\)M. [PERSON] et al. [141] demonstrated a green strategy for producing a graphene foam-like 3D porous carbon/NiNPs nanocomposites-based glucose detection electrode. The team used a 3D porous carbon derived from the waste biomass to produce a highly sensitive biosensor. The sensor shows a linear range of 15.84-6.48 mM, and a detection limit of 4.8 \(\upmu\)M. [PERSON] et al. [142] prepared a DNA-dispersed graphene/NiO hybrid material deposited in a glassy carbon electrode using a self-assembly process to prepare the GNS/NiO powder while ssDNA was employed to produce the GNS/NiO/DNA hybrids. The experimental work shows low detection limits and good sensitivity. [PERSON] et al. [143] fabricated a graphene oxide/nickel oxide modified glassy carbon electrode (NiONPs)/GO/glassy carbon (GC)-based non-enzymatic sensor. The work was characterized by the scanning electron microscope (SEM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). NiONPs were synthesized on the surface of GO electrochemically. The NiONPs/GO/GC electrode shows a good electrocatalytic behavior towards GOx with a linear range of 3.13-3.05 mM and a limit of detection of 1 \(\upmu\)M. [PERSON] et al. [144] designed graphene oxide-Ni \((OH)_{2}\) composites-based electrodes for non-enzymatic glucose sensing. The rGO/Ni \((OH)_{2}\) shows the linear range of 15-30 mM with a good sensitivity. The electrophoretic deposition has been used for sensing matrix fabrication, while the matrix characterization was through X-ray photoelectron spectroscopy, Raman spectroscopy, and cyclic voltammetry. [PERSON] et al. [96] demonstrated a successful use of a silver nanowire/graphene hybrid three-dimensional (Ag NW/RGO hybrid 3D) nanostructure for an ultra-sensitive non-enzymatic glucose sensor. While the microwave method followed by oxidation and exfoliation of an expanded graphite was used to prepare the GO, the hydrothermal reduction of silver salt was used for the Ag-NWs preparation. The hydrothermal sol-gel method was used for the Ag NW/RGO hybrid 3D preparation. The material characterization was obtained using X-ray diffraction (XRD) measurement, ultraviolet-visible (UV-Vis) spectroscopy, and scanning electron microscopy (SEM). The electrochemical properties were obtained using the CV method to check the electrocatalytic activity of the electrode towards the GO\(x\). The sensor investigated a very high sensitivity of about 1249.1 \(\upmu\)A mM\({}^{-1}\) cm\({}^{-2}\), and a low LOD of about 0.38 \(\upmu\)M. Figure 10 describes the electrocatalytic activity of this sensor. [PERSON] et al. [145] employed an Ni \((OH)_{2}\)/3D graphene foam for nonenzymatic glucose detection. The hydrothermal process has been used to deposit the hexagonal Ni \((OH)_{2}\) nanosheets on the surface of 3 DGF while the 3 DGF used a chemical vapor deposition-growth process. The Ni \((OH)_{2}\)/3D graphene foam was characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), Raman spectroscopy, and X-ray diffraction (XRD). The work has been demonstrated by a linear range of 1-1.17 mM and a detection limit of 0.34 uM. [PERSON] et al. [146] successfully made a non-enzymatic sensor based on a NiCo\({}_{2}\)S/tGO nanocomposite, this kind of sensor shows a good redox tenability and good charge transport property. While the applied potential was +0.35 V, a wide linear range was recorded as 1-4.0 mM, sensitivity of 18.89 mA mM\({}^{-1}\) cm\({}^{-2}\), and detection limit of 0.65 uM.