Biosynthesis of ZnO nanoparticles using aqueous extracts of Eclipta prostrata and Piper longum: characterization and assessment of their antioxidant, antibacterial, and photocatalytic properties

Abstract

Chemical syntheses of nanoparticles that release toxic substances into the environment rarely meet the strict requirements of green chemistry principles. Instead, green synthesis of nanoparticles using plant extracts brings a safe, rapid, and effective process, contributing to solving environmental pollution problems. Here, we report the green synthesis of multifunctional ZnO nanoparticles (ZnONPs) using aqueous extracts of E. prostrata leaves and P. longum fruits. The XRD results affirmed the existence of hexagonal crystalline ZnONPs with particle sizes of 17-30 nm. The optical analysis revealed bandgap energies of 3.10 eV and 3.16 eV for ZnONPs biosynthesized using E. prostrata and P. longum extracts, respectively. The synthesized ZnONPs showed potential antioxidant activity through DPPH and ABTS methods. Among the antibacterial outcomes against pathogenic bacterial strains (S. aureus, B. cereus, E. coli, and S. typhimurium), ZnONPs exhibited the highest zone of inhibition (18.5 mm) for S. aureus. Moreover, both ZnONPs biosynthesized using E. prostrata and P. longum extracts served as strong photocatalysts in the degradation of crystal violet with degradation efficiencies of 95.64% and 99.90%, respectively. Therefore, biosynthesized ZnONPs hold significant promise as antioxidants, antibacterial agents, and photocatalysts.