Green‐Synthesis of Zinc Oxide‐Cobalt Oxide Nanocomposites Using <i>Aporosa cardiosperma</i> : Characterization and Studies on Environmental and Biological Remediation

ABSTRACT A sustainable synthesis of a hybrid zinc oxide‐cobalt oxide nanocomposite (ZnO‐Co 3 O 4 NCs) has been achieved using extracts from A. cardiosperma in a one‐pot green chemistry method. The multifarious biological and environmental applications of the green‐synthesized ZnO‐Co 3 O 4 NCs were evaluated based on their antioxidant, antibacterial, and dye‐degradation activities, as well as their plant‐growth‐promoting properties. The morphological features of the surface functionalized hybrid ZnO‐Co 3 O 4 NCs have been determined by UV–vis, fourier transform‐infrared (FT‐IR), X‐ray diffraction (XRD), dynamic light scattering‐ zeta potential (DLS‐Zeta), field emission‐scanning electron microscopy (FE‐SEM), and high‐resolution transmission electron microscopy (HR‐TEM) techniques. The characteristic surface plasmon resonance peaks (λ max ) appeared at 270 and 510 nm. XRD and X‐ray photoelectron spectroscopy (XPS) techniques validated the crystalline structure and electron binding affinity of NCs, respectively. The ZnO‐Co 3 O 4 NCs demonstrated excellent inhibitory activity against Bacillus subtlis (25 mm) at 100 µg/mL. Furthermore, ZnO‐Co 3 O 4 NCs exhibited potent radical scavenging, ferrous ion reducing, and metal chelation capabilities. In environmental applications, the ZnO‐Co 3 O 4 NCs exhibited efficient photocatalytic activity for the degradation of methylene blue, achieving 98.19% under sunlight irradiation. The study examined their efficacy in combating infectious diseases, facilitating environmental remediation, and enhancing plant development, thereby advancing sustainable technological development.