Sensitive and selective detection of 4-nitrophenol using a zirconium metal–organic framework loaded reduced graphene oxide modified glassy carbon electrode

Phenolic compounds in water bodies pose significant threats to humans, animals and aquatic life. A new electrochemical sensor has been developed for the sensitive and selective detection of 4-nitrophenol (4-NP), utilizing the incorporation of zirconium metal–organic framework (UiO-66-NH₂) and reduced graphene oxide (rGO). The UiO-66-NH₂/rGO electrocatalyst was synthesized by the solvothermal method using zirconium oxychloride octahydrate, 2-amino terephthalic acid and rGO. Various characterization techniques including — X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Field-emission scanning electron microscopy (FESEM), UV–visible diffuse reflectance spectroscopy (UV-DRS), Raman spectroscopy and cyclic voltammetry (CV) were employed to analyze the physical properties, morphology, and electrochemical performance of the prepared materials. The resulting UiO-66-NH₂/rGO/GCE electrode demonstrates effective electrocatalytic activity for the cathodic reduction of 4-NP due to its high porosity, favourable electron transfer kinetics and enhanced sensitivity. Differential pulse voltammetry reveals a linear response for 4-NP concentrations ranging from 0.5 to 100 μM, with a high sensitivity of 0.1 μA/μM and a low detection limit of 15 nM. Additionally, the sensor showcases several advantages, including anti-interference ability, selectivity for 4-NP in the presence of other interfering species, strong repeatability and stability. The developed sensor was successfully tested for practical applications in river water samples. 

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