Intergradation of UiO-66 Nanoparticles with Expanded Graphite for Electrocatalytic Determination of Nitrite and L-Cysteine

In this study, metal–organic framework (MOF) nanoparticles of UiO-66 are integrated with expanded graphite (EG) (UiO-66/EG) by a facile solvothermal approach. The advantages of this nanocomposite UiO-66/EG overcome the poor electronic conductivity and slow diffusion of MOFs for their electrochemical applications. Through electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical techniques, the morphology, surface area, and physicochemical properties of this UiO-66/EG nanocomposite are characterized. The UiO-66/EG nanocomposite exhibits superior sensing performance over the UiO-66 and EG when used for nitrite and L-cysteine determination. This includes less positive oxidation potentials and enhanced oxidation currents. Using the UiO-66/EG nanocomposite, the nitrite oxidation peak current is linear with a concentration range of 0.20 μ m to 13.15 m m with the lowest limit of detection (LOD) of 0.06 μ m ( S / N = 3). Meanwhile, superior performance is demonstrated for L-cysteine monitoring, where the oxidation peak current is linear over the L-cysteine concentration in the range of 0.5–250 μ m and of 0.25–3.50 m m and a LOD of 0.28 μ m ( S / N = 3). This UiO-66/EG/GCE nanocomposite is successfully exploited to detect nitrite in food samples and to measure L-cysteine in juice samples. Therefore, the proposed sensing platform enables the fabrication of high-performance electrochemical sensors to accurately quantify nitrite and L-cysteine in complex matrixes.