Abstract

The current investigation successfully synthesised Co3O4 nanoparticles through a combustion method that employs a sustainable and economical approach, utilising the leaf, stem, and root extracts of the Eichhornia crassipes plant along with urea. The phytochemicals found in the plant extract functioned as natural capping and stabilising agents, facilitating the formation of Co3O4 nanoparticles under meticulously controlled conditions. The Rietveld refinement of XRD patterns substantiated the synthesis of cobalt oxide nanoparticles exhibiting a cubic crystal structure. The elastic behaviour of Co3O4 nanoparticles, influenced by various components of Eichhornia crassipes, exhibits notable variation. The elastic moduli of Co3O4 nanoparticles enhanced with stem are measured at 176.58, 65.91, and 183.40 GPa, representing the highest values when compared to those of Co3O4 nanoparticles enhanced with leaf and root. Among the samples examined, the one enhanced by leaf assistance exhibited the most diminutive crystallite size, measuring at 12.5 nm. The FT-IR analysis substantiated that the metal-oxygen vibrations beneath 1000 cm-1, evidenced by peaks at 650 cm-1 and 537 cm-1, affirmed the successful synthesis of Co3O4 NPs featuring both tetrahedral and octahedral Co–O bonding. The analysis of Co3O4 nanoparticles was conducted through UV-Visible diffuse reflectance spectroscopy (DRS), revealing direct band gap energies of 3.29 eV, 3.37 eV, and 3.28 eV. A relationship was identified between particle size and band gap energy, indicating that larger particles (18.90 nm) displayed a reduced band gap (3.28 eV). The analysis of photoluminescence substantiated the energy band gap and optical characteristics of Co3O4 nanoparticles. The FE-SEM analysis indicated a spherical morphology characterised by agglomeration for the Co3O4 nanoparticles assisted by leaves and stems, while those facilitated by roots displayed porous, dispersed spherical structures. The EDX analysis substantiated the synthesis of Co3O4 nanoparticles through the identification of significant peaks associated with cobalt (Co) and oxygen (O). The zeta potential measurements for cobalt oxide nanoparticles revealed negative values of -41.9 mV for leaves and -40.1 mV for roots, thereby affirming their commendable colloidal stability.

Keywords

Green Synthesis, Cobalt Oxide Nanoparticles (Co3O4), Eichhornia Crassipes, Rietveld Refinement, Optical Band Gap, Zeta Potential,

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