Application of boron-doped diamond modified cobalt oxide nanoparticles (BDD/CoONPs) as an electrochemical sensor for hydrocortisone detection

In this study, a boron-doped diamond (BDD) electrode modified with cobalt oxide nanoparticles (CoONPs) is proposed as a working electrode for hydrocortisone (HC) detection in 0.1 M NaOH. CoONPs were synthesized via a green synthesis approach using Nigella sativa seed extract and cobalt nitrate as precursors. The synthesized CoONPs were characterized in terms of functional groups, elemental composition, and surface morphology. The electrochemical redox behavior of HC was investigated using differential pulse voltammetry (DPV) within a potential range of +0.5 to +1.6 V (vs. Ag/AgCl), with variations in pH and analyte concentration to evaluate the sensing performance and determine the limit of detection (LoD). A detection limit of 8.19 × 10⁻³ μM was achieved, accompanied by good measurement stability, with repeatability and reproducibility values of 1.43% and 1.03% RSD, respectively. These results demonstrate the strong potential of the BDD/CoONPs electrode for sensitive and reliable HC detection.