Facile green synthesis of Co3O4 nanoparticles using turmeric extract: In vitro biomedical activities

• Achievement of green biosynthesized cobalt oxide nanoparticles (CO-NPs) via the curcumin ethanolic extract. • XRD analysis showed an average crystallite size of 31.2 nm, confirming the nanoparticles' structure. • The CO-NPs demonstrated potent antioxidant activity, with an IC 50 value of 1.171 mg/mL, outperforming curcumin. • The biosynthesized CO-NPs exhibited potent antibacterial activity against B. subtilis and E. coli . • CO-NPs demonstrated impressive IC 50 values of 26.4 µg/mL and 43.6 µg/mL for Caco-2 and MCF-7 cell lines, respectively, indicating their potential as a cancer treatment. This research investigates the eco-friendly synthesis and comprehensive characterization of cobalt oxide nanoparticles (CoO-NPs) using turmeric ethanolic extract. Fourier transform infrared spectroscopy confirmed the presence of functional groups in the extract and their involvement in nanoparticle stabilization. Ultraviolet-visible spectroscopy revealed an absorption peak at 417 nm, with bandgap energies of 3.45 eV and 3.21 eV for direct and indirect transitions, respectively, as determined by Tauc's plot. X-ray diffraction analysis yielded an average crystallite size of 31.2 nm, while energy-dispersive X-ray spectroscopy verified the elemental composition. The nanoparticles displayed a zeta potential of -21.66 mV, and dynamic light scattering indicated a hydrodynamic diameter of 86.29 nm with a polydispersity index of 0.38. Transmission and scanning electron microscopy demonstrated an average particle size of 26.3 nm, featuring cubic structures and diverse surface morphologies. Antioxidant activity was evaluated using the DPPH assay, resulting in IC 50 values of 3.82 mg/mL for the turmeric extract and 1.171 mg/mL for the CoO-NPs, compared to 0.42 mg/mL for BHT. The antibacterial efficacy of the CoO-NPs was assessed against Gram-positive Bacillus subtilis and Gram-negative Escherichia coli , with minimum inhibitory concentrations of 25.3 mg/L and 22.8 mg/L, respectively. Furthermore, the nanoparticles exhibited substantial anti-cancer effects, with IC 50 values of 26.4 µg/mL against Caco-2 cells and 43.6 µg/mL against MCF-7 cells. This work advances green nanotechnology by integrating scientific innovation with environmental sustainability, thereby opening avenues for further research in materials science and biomedical applications.