Synthesis and Characterization of Calcium Oxide Nanoparticles for Biological Antioxidant Activity

The present work demonstrates the efficient, cost-effective, and environmentally friendly synthesis of calcium oxide nanoparticles (CaO NPs) using an aqueous extract of Moringa oleifera (MO) stem powder. Phytochemicals in the plant extract served as reducing and capping agents, enabling the conversion of a calcium nitrate precursor into stable nanosized particles. The resulting CaO NPs were thoroughly characterized using multiple instrumental analyses to confirm their physical, structural, and chemical properties. FTIR analysis confirmed the functionality of the MO extract and also showed the presence of residual phytochemicals on the surface of the NPs. The XRD pattern revealed that it is a well-crystallized material with a cubic phase consistent with a reference CaO phase (JCPDS No. 00-004-0777). The average size of the crystallites was 30 nm, indicating the successful synthesis. SEM also revealed the morphology of the NPs and their tendency to form agglomerates, a characteristic inherent to nanomaterials. Simultaneously, the elemental composition was observed from the EDX analysis, where prominent peaks of Ca and O, along with the characteristic carbon peak of the capping agents, were detected. UV-Vis absorption spectra showed a characteristic absorption peak in the UV region, and the band gap values indicated quantum confinement effects in the nanosized materials. The as-synthesized CaO NPs also showed significant antioxidant activity based on the DPPH assay, which is linked to dose-dependent free radical scavenging. This bioactivity may result from surface-adsorbed phytochemicals from the MO extract. This study offers a green, simple, and cost-effective method for synthesizing crystalline and bioactive CaO NPs, which could be used in catalysis, biomedicine, and environmental cleanup.