NiCo₂O₄ nanoparticles for enhancing voltammetric determination of sodium diclofenac in aqueous solutions

The presence of the pharmaceuticals in water as emergent pollutants necessitates a continuous improving of their sensing, e.g., through voltammetric detection with the performance given by electrode composition. In this study, nickel cobaltite (NiCo₂O₄) synthesized by the thermolysis was deeply investigated by X-ray diffraction, high-resolution scanning electron microscopy (HR-SEM), and high-resolution transmission electron microscopy coupled with selected area electron diffraction. Also, X-ray photoelectron spectroscopy was used to determine the oxidation state of Ni and Co cations. NiCo₂O₄ was tested as modifier for commercial glassy carbon (GC) electrode by drop-casting as NiCo₂O₄/GC electrode for the voltammetric detection of sodium diclofenac salt (DCF) in water. In our study, the lowest limit of detection of 3 nM, better than ones reported in the literature, was achieved for DCF determination using differential pulse voltammetry with the scan rate of 0.05 V s^-1, step potential of 50 mV, modulation amplitude of 200 mV. The optimized voltammetric detection method was validated by DCF determination in real tap water.