Green synthesis, characterization, antibacterial, and antifungal activity investigation of zinc oxide nanoparticles using Verbascum Sinaiticum leaf extract

Abstract

• Eco-friendly synthesis of ZnO nanoparticles using Verbascum sinaiticum leaf extract • Green-synthesized ZnO NPs exhibit strong antibacterial and antifungal properties • Plant-mediated synthesis offers a safe and non-toxic alternative to chemical methods • FTIR, XRD, SEM, and UV-Vis analyses validate nanoparticle purity and stability • Verbascum sinaiticum acts as both reducing and capping agent • Potential for future development of plant-based antimicrobial nanomaterials In this study, zinc oxide nanoparticles (ZnO NPs) were eco-friendly synthesized using Verbascum sinaiticum leaf extract (VSPLE). The amount effects such as pH adjusted at (4, 6, 7, 8, 10 and 12), zinc acetate concentration (0.1, 0.2, 0.3, 0.05, and 0.025 M), reaction temperature (20, 40, 60, 80 and 100°C), reaction time (20,40, 60, 80, 100, 120, and 140 min), and plant extract volume(1, 2, 3, 4, and 5 mL). The synthesized nanoparticles were characterized by using SEM, TGA/DTA, XRD, UV-Vis, and FT-IR spectroscopic techniques. The SEM analysis revealed that the synthesized ZnO NPs exhibited a rod-shaped morphology, and a total weight loss of 15.29% observed at 24-544°C in the TGA/DTA analysis, with no further weight loss above 544°C, confirmed the high thermal stability of ZnO NPs. The XRD analysis confirmed the formation of small sized ZnO NPs with an average crystal size of 52.9 nm. The UV-Vis analysis revealed the absorption of ZnO NPs at 400 nm, and the characteristic band observed in FT-IR analysis at 635 cm⁻¹ for Zn-O stretching confirmed the formation of ZnO NPs. The biosynthesized ZnO NPs demonstrated a significant in vitro antimicrobial activity as evidenced by the inhibition zone sizes against one Gram-positive S. aureus (17.10 ± 0.17) and two Gram-negative bacteria K. pneumoniae (14.17 ± 0.29), and E. coli(12.83 ± 0.29 ) at 10 mg/mL using the disc diffusion method. It also showed good antifungal activity against Candida ethanolica ( 6.90±0.10) and Saccharomyces cerevisiae ( 6.00±0.10), support the potential of plant-mediated nanoparticle synthesis as a promising route for developing biocompatible antimicrobial agents.