ABSTRACT

This research investigated the synthesis and characterization of cobalt oxide nanoparticles (CoONPs) using an aqueous extract of Saccharum officinarum (sugarcane) leaves. The leaves were collected from the Faculty of Agriculture at the University of Benin, air-dried, and ground into a fine powder. Phytochemical extraction was performed by boiling the powdered leaves in distilled water, which acted as both a reducing and stabilizing agent in the nanoparticle synthesis process. Cobalt nitrate was mixed with the leaf extract under controlled conditions, leading to the reduction of cobalt ions into CoONPs. The synthesized nanoparticles were separated by centrifugation, washed with distilled water and ethanol, and dried. Various characterization techniques were employed to analyze the nanoparticles. The X-ray diffraction (XRD) analysis confirmed the presence of a high degree of crystallinity, with a prominent peak at 2θ = 20.86°, corresponding to the Co₃O₄ phase, and small crystallite sizes of approximately 3.51 nm. Scanning Electron Microscopy (SEM) combined with Energy Dispersive X-ray Spectroscopy (EDX) revealed that cobalt was the dominant element (82.79% atomic concentration), along with trace amounts of potassium, aluminum, and other elements. SEM images showed irregularly shaped nanoparticles, indicating a monodispersed nature. Fourier Transform Infrared Spectroscopy (FTIR) identified key functional groups such as hydroxyl (O-H), at peak 3659.3 cm⁻¹ and 3809.3 cm⁻¹, alkyl (C-H) at peak 2922.2 cm⁻¹ and 2378.0 cm⁻¹, and metal-oxygen (Co-O) bonds at peaks 997.9 cm⁻¹, 887.7 cm⁻¹, and 864.7 cm⁻¹, suggesting interactions between the plant extract and the metal oxide, which may influence nanoparticle stability and properties. Dynamic Light Scattering (DLS) analysis indicated a Z-average particle size of 45.46 nm and a polydispersity index (PDI) of 0.271, confirming the monodispersed nature of the nanoparticles. Despite these promising characteristics, antimicrobial testing using the agar well diffusion method at a concentration of 25 mg/ml revealed no inhibition zones against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, or Klebsiella pneumoniae, indicating a lack of antimicrobial activity at this concentration. Further research is suggested to optimize nanoparticle synthesis, increase concentrations, or explore combination treatments to enhance antimicrobial efficacy.

Keywords: Cobalt oxide nanoparticles, sugarcane leaf extract, phytochemical extraction, XRD, SEM-EDX, FTIR, DLS, antimicrobial activity.