Bio-capped ZnO nanoparticles for enhanced electrochemical detection of paracetamol

This study describes the green synthesis of zinc oxide nanoparticles (ZnONPs) using fruit peel extracts (passion fruit, guava, and kumquat), denoted as Pa-ZnONPs, Gu-ZnONPs, and Ku-ZnONPs. The bioactive compounds in the fruit peels (proteins, minerals, phenolic compounds, and flavonoids) successfully facilitated ZnONP formation and stabilization. SEM and DLS analyses revealed polydispersed nanoparticles with average sizes of 80, 60, and 90 nm for the Pa-ZnONPs, Gu-ZnONPs, and Ku-ZnONPs, respectively. All samples exhibited a hexagonal wurtzite crystal structure with band gap energies of 3.1–3.2 eV, as confirmed by XRD and UV-Vis spectroscopy (maximum absorption at 375 nm). When coated on screen-printed carbon electrodes (SPCEs), ZnONPs significantly enhanced the electrochemical detection of paracetamol. The Gu-ZnONPs/SPCE demonstrated optimal performance, achieving a linear detection range of 0.78–5.12 μmol L⁻¹ and a detection limit of 0.24 μmol L⁻¹ . The calibration plot exhibited excellent linearity ( R² = 0.9992) and high reproducibility (RSD = 3.8%), indicating highly reliable quantitative performance. Ultimately, this waste-to-value approach highlights the significant potential of utilizing specific fruit-peel-mediated ZnONPs for sensitive, eco-friendly pharmaceutical monitoring, demonstrating robust fundamental electrocatalytic properties for future sensor development.