| Summary: | This study presents an electrochemical sensor for detecting epicatechin (EC) in food samples (dark chocolate and apple) using cobalt oxide (Co3O4) synthesized from Carica papaya peel extract combined with multiwalled carbon nanotubes (GCE/MWCNTs/Co3O4), doped onto glassy carbon electrode. Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were used to examine the structural, morphological, and electrochemical properties of the electrode materials. The GCE/MWCNTs/Co3O4 electrode demonstrated excellent electron transport properties as well as excellent electrocatalytic activity towards EC, with a Rct value of 4.74 kΩ lower than that of the bare electrode. A detection limit of 0.12 µM and a sensitivity of 0.0837 µA/µM were obtained using square wave voltammetry (SWV) for EC concentrations between 47.6 - 310.3 µM. The designed sensor demonstrated good repeatability, stability, reproducibility, selectivity, and excellent recoveries (90-108%) with RSDs ranging from 0.46 to -2.52 for the detection of EC in food samples. Further, the EC's energy band gap (- 5.15 eV) and absolute hardness (- 2.57 eV) calculated at the density functional theory (DFT) level, indicate its strong chemical reactivity. Finally, the computed Monte Carlo adsorption energy confirms the strong electrostatic interaction between the surface of the GCE/MWCNTs and the Co3O4 NPs, thus contributing to the selectivity of EC detection, demonstrating the potential applications for the designed sensor in the food industry.
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