Supercritical CO₂ directional-assisted green synthesis of ZnO nanoparticles obtained from Euphorbia stricta L. for functional applications

The green synthesis method is increasingly favored due to its economic and environmental benefits. Metal oxides, such as zinc oxide (ZnO) nanoparticles produced via green synthesis, exhibit biocompatible and stable properties. In this study, the Euphorbia stricta plant was extracted using the supercritical CO2 extraction method. Subsequently, ZnO nanoparticles were synthesized using the Euphorbia stricta extract through a microwaveassisted hydrothermal method. The synthesized ZnO was characterized using X-ray diffraction (XRD), Ultraviolet-visible spectroscopy (UV-Vis), and Fourier-transform infrared spectroscopy (FT-IR). Euphorbia stricta L. extract was also characterized by FT-IR. To evaluate the photocatalytic activities against methylene blue, ZnO/ polyacrylonitrile (PAN) membranes were fabricated via electrospinning for comparative analysis. The degradation efficiencies of ZnO and ZnO/PAN nanofibers were 76.37 % and 66.14 % over 180 min, respectively. Furthermore, the green synthesized ZnO nanoparticles demonstrated significant antibacterial properties against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. These bacteria are of critical importance in medical and environmental contexts: cause of skin infections, pneumonia and bloodstream infections; foodborne illnesses and urinary tract infection and hospital-acquired infections. The findings suggest that ZnO nanoparticles synthesized from Euphorbia stricta extract have substantial potential for application in antibacterial treatments and photocatalysis, offering a promising approach to addressing challenges posed by these pathogenic bacteria.