Sustainable and Efficacy Approach of Green Synthesized Cobalt Oxide (Co₃O₄) Nanoparticles and Evaluation of Their Cytotoxicity Activity on Cancerous Cells

In this study, rosemary leaf extract was effectively used to synthesize cobalt oxide nanoparticles (Co₃O₄ NPs) using a rapid, low-cost, and environmentally friendly approach. The prepared Co₃O₄ NPs were examined using various analytical techniques. However, UV spectrum analysis displayed two sharp absorption peaks at ~350 and 745 nm. The dynamic light scattering and zeta potential measurements were used to evaluate the particle size and the effective stabilization of the synthetic nanoparticles in the suspensions. A semi-triangular pyramidal shape of the Co₃O₄ NPs with a wide particle-size distribution could be observed in the scanning electron microscopy images. The energy-dispersive X-ray spectrum confirmed their successful synthesis, as the experimental atomic percentages agreed with the theoretical values. Moreover, X-ray diffraction analysis revealed that the synthesized Co₃O₄ NPs had a cubic crystalline structure corroborating that of theoretical Co₃O₄. Additionally, the Co₃O₄ NPs were not toxic at ≤62.5 µg/mL for Hep G2 and at ≤31.25 µg/mL for Mcf7. Therefore, these unique environmentally friendly Co₃O₄ NPs at this safe concentration could be studied in the future for their therapeutic activity.