This study involved the synthesis of cobalt oxide (Co3O4) nanoparticles (NPs). Using a sustainable green utilization of Cinnamon (Cinnamomum zeylanicum) and Nigella sativa extracts, alongside a conventional chemical synthesis method for comparison. Comprehensive structural, morphological, and optical characterizations confirmed the successful synthesis of Co3O4 NPs with distinct properties. XRD analysis revealed smaller crystalline sizes for green-synthesized NPs (5.49 nm for Cinnamon and 7.22 nm for Nigella sativa) compared to chemically synthesized ones (10.6 nm), while FTIR identified functional groups contributing to enhanced chemical and biological activity. FESEM and AFM analyses showed improved surface topography, reduced roughness, and higher effective surface areas in biogenically NPs. UV-visible spectroscopy demonstrated enhanced electronic properties, with band gaps of 1.61 eV and 1.59 eV for Cinnamon and Nigella sativa-derived NPs, respectively, as compared to 1.43 eV for chemically synthesized NPs. Biological assays revealed superior antimicrobial activity of green-synthesized NPs, particularly Cinnamon-derived NPs against Staphylococcus aureus (34 mm), Escherichia coli (30 mm), and Nigella sativa-derived NPs against Candida albicans (41 mm). The synergistic action between plant-derived compounds such as Cinnamaldehyde and Thymoquinone and cobalt oxide nanoparticles enhanced their antimicrobial efficacy. In conclusion, the use of plant extracts for synthesizing Co3O4 NPs offers a sustainable, economical substitute for the chemical approach, producing nanoparticles.

This study involved the synthesis of cobalt oxide (Co3O4) nanoparticles (NPs). Using a sustainable green utilization of Cinnamon (Cinnamomum zeylanicum) and Nigella sativa extracts, alongside a conventional chemical synthesis method for comparison. Comprehensive structural, morphological, and optical characterizations confirmed the successful synthesis of Co3O4 NPs with distinct properties. XRD analysis revealed smaller crystalline sizes for green-synthesized NPs (5.49 nm for Cinnamon and 7.22 nm for Nigella sativa) compared to chemically synthesized ones (10.6 nm), while FTIR identified functional groups contributing to enhanced chemical and biological activity. FESEM and AFM analyses showed improved surface topography, reduced roughness, and higher effective surface areas in biogenically NPs. UV-visible spectroscopy demonstrated enhanced electronic properties, with band gaps of 1.61 eV and 1.59 eV for Cinnamon and Nigella sativa-derived NPs, respectively, as compared to 1.43 eV for chemically synthesized NPs. Biological assays revealed superior antimicrobial activity of green-synthesized NPs, particularly Cinnamon-derived NPs against Staphylococcus aureus (34 mm), Escherichia coli (30 mm), and Nigella sativa-derived NPs against Candida albicans (41 mm). The synergistic action between plant-derived compounds such as Cinnamaldehyde and Thymoquinone and cobalt oxide nanoparticles enhanced their antimicrobial efficacy. In conclusion, the use of plant extracts for synthesizing Co3O4 NPs offers a sustainable, economical substitute for the chemical approach, producing nanoparticles.