Green Synthesis and Characterization of Cobalt Oxide Nanoparticles using Eucalyptus Globulus Leaf Extract: In Vitro Antibacterial and Antifungal Activity
DOI:
https://doi.org/10.33003/fjs-2026-1022-5298Keywords:
cobalt nanoparticle, green synthesis, Eucalyptus globulus, Antimicrobial activityAbstract
The rise of antibiotic resistance has intensified the search for novel antimicrobial agents. Green synthesis of metal oxide nanoparticles using plant extracts offers an eco-friendly alternative to conventional methods. This study reports the green synthesis and characterization of cobalt oxide nanoparticles (CoNPs) using an aqueous leaf extract of Eucalyptus globulus and cobalt (II) chloride, and evaluates their in vitro antibacterial and antifungal activity. Nanoparticle formation was confirmed by UV-Vis, FTIR, XRD, and SEM. UV-Vis spectra showed an absorption band at 220 nm, consistent with the O²⁻→Co²⁺ charge-transfer transition for Co₃O₄. FTIR bands at 660–690 and 570–660 cm⁻¹ confirmed Co–O lattice vibrations. XRD revealed a crystalline structure with an average particle size of 72 nm, while SEM showed an irregular, clustered morphology. Antimicrobial activity was evaluated by agar well diffusion against Staphylococcus aureus, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, Candida albicans, Aspergillus niger, and Aspergillus flavus. The CoNPs produced the largest inhibition zones against C. albicans (19.9±0.34 mm) and S. aureus (18.5±0.13 mm), and were active against all organisms except S. typhi (9.7±0.22 mm). Notably, the crude n-hexane extract (15 mg/mL) outperformed the CoNPs against S. aureus (23.7 mm). These findings indicate that E. globulus-mediated cobalt oxide nanoparticles are promising antimicrobial candidates, pending in vivo evaluation.
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Copyright (c) 2026 Rashida Mahmud Kachalla; Mohammed Shagal Hassan, Dass Peter Micheal, Jamila Atiku
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