Yunusa Bakari, Usman Abubakar Adamu, Muhammad Muhammad Muzakir and Mohammed Gidado
Nigerian Research Journal of Chemical Sciences (ISSN: 2682-6054)
Volume 14, Issue 1, 2026
http://www.unn.edu.ng/nigerian-research-journal-of-chemical-sciences/ 204
Synthesis and Characterization of Cobalt Nanoparticles Using Neem (Azadirachta indica)
Leaf Extract and Evaluation of Its Antibacterial Efficacy
1Yunusa Bakari, *1Usman Abubakar Adamu, 1Muhammad Muhammad Muzakir and
2Mohammed Gidado
1Department of Chemical Sciences, Gombe State University (GSU), Gombe, Nigeria.
2Department of Medical Microbiology and Immunology, Federal Teaching Hospital (FTH),
Gombe, Nigeria.
*Corresponding Author: aausman@gsu.edu.ng
Accepted: February 26, 2026. Published Online: March 10, 2026
ABSTRACT
The study presented the green synthesis of cobalt nanoparticles (Co-NPs) using aqueous leaf
extract of Azadirachta indica (neem) and the evaluation of their antibacterial efficacy against
Staphylococcus aureus and Escherichia coli. Ten grams of dried neem leaf powder were boiled in
100 mL of distilled water to obtain the extract, which was used as both a reducing and stabilizing
agent. A 0.032 mol/dm3 cobalt chloride solution was prepared and reacted with the extract in a 3:1
ratio under continuous stirring at room temperature for one hour, resulting in a visible colour
change from wine red to dark brown, confirming nanoparticle formation. Characterization was
performed using UV–visible (UV–Vis) spectroscopy, Fourier Transform Infrared Spectroscopy
(FTIR), and X-ray Diffraction (XRD). The UV–vis analysis showed a characteristic surface
Plasmon resonance (SPR) peak at 318 nm, indicating successful nanoparticle formation. FTIR
revealed active functional groups (–OH, –NH, C=O) involved in reduction and stabilization, while
XRD confirmed crystalline face-centered cubic (FCC) cobalt with an average crystalline size of
13 nm. Antibacterial activity assessed via agar well diffusion revealed concentration-dependent
inhibition zones, with maximum activity against S. aureus (22 ± 0.6 mm) and moderate activity
against E. coli (17 ± 0.6 mm) at 100 μg/mL. The findings validate neem as an effective biogenic
medium for eco-friendly synthesis of cobalt nanoparticles with promising antibacterial potential.
Keywords: Antibacterial activity, Cobalt nanoparticles, FTIR, green synthesis, neem extract,
XRD.
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