Sustainable synthesis of ZnO nanoparticles using fruit peel, VOC sensing and DFT insights

This study demonstrates the gas-sensing potential of zinc oxide (ZnO) nanoparticles (NPs) synthesized through a sustainable, green approach using mosambi (Citrus sinensis) fruit peel extract, with NaOH volume varied to tune their properties. Structural and optical characteristics were examined using XRD, FESEM, UV–Vis, and photoluminescence spectroscopy. The average crystallite sizes of the three samples ranged from 43.0 nm to 59.4 nm, as obtained by XRD. FESEM analysis revealed NaOH dependent morphological variations, with mean grain sizes between 43.33 – 107.68 nm. The ZnO NPs exhibited high selectivity and sensitivity toward key volatile organic compounds (ethanol, methanol, propanol, acetone, and toluene). Complementary Density Functional Theory (DFT) and Monte Carlo (MC) simulations indicated stronger ethanol adsorption on the ZnO (002) facet compared to (100) and (101), highlighting the role of surface orientation in sensing behavior. The combined experimental–computational approach provides valuable insights into VOC detection mechanisms and offers a pathway for designing efficient ZnO-based gas sensors.