Sulfur and copper dual doped zinc oxide nanoparticles for enhanced photocatalytic efficiency and prolonged orange shelf life

Zinc oxide nanoparticles (ZnO-NPs) are used in industries, environmental cleanup, catalysis, and fruit preservation. Their performance is limited by a large bandgap and fast electron-hole recombination. These factors reduce their ability to absorb visible light effectively. To improve their efficiency, surface modifications like doping have been studied. In this study, we investigated the effects of copper (Cu) and sulfur (S) doping on the photocatalytic activity of ZnO-NPs and their ability to prolong the shelf life of orange fruits. The results showed that pure ZnO-NPs possess an optical bandgap of 2.98 eV. Doping with 3 % Cu, 2 % S, and a combination of Cu and S (codoping) reduced the bandgap to 2.92 eV, 2.75 eV, and 2.57 eV, respectively. The decrease in bandgap energy is attributed to alterations in the electronic structure caused by doping. X-ray diffraction (XRD) analysis revealed that the crystal sizes, calculated from the full width at half maximum (FWHM), were 25.06 nm for pure ZnO, 23.05 nm for 3 % Cu-ZnO, 27.02 nm for 2 % S-ZnO, and 21.06 nm for the dual-doped ZnO-NPs. The reduction in both particle size and bandgap following doping contributed to an extended shelf life of oranges treated with the dual-doped ZnO-NPs compared to those treated with pure ZnO-NPs. Additionally, dual doping significantly improved photocatalytic efficiency, increasing degradation performance from 89 % to 99 % at optimal dopant concentrations. Overall, incorporating Cu and S as dual dopants effectively enhances the functional properties and performance of ZnO-NPs, broadening their potential across various applications. • Copper and sulfur dual doping lowers the ZnO bandgap from 3.07 eV to 2.56 eV, improving visible light absorption. • Doping reduces particle size from 25.06 nm (pure) to 21.06 nm, enhancing photocatalytic activity. • Dual-doped ZnO-NPs achieve up to 99 % photocatalytic efficiency, higher than 89 % for pure ZnO. • Doped ZnO-NPs extend orange shelf life more effectively, supporting applications in food preservation and environment.