Green synthesis of metal oxide nanoparticles under ambient conditions provides an environmentally sustainable route for advanced functional materials. In this study, calcium oxide (CaO) nanoparticles were synthesized at room temperature using Polyalthia longifolia leaf extract as a bio-derived reducing and stabilizing agent, eliminating the need for hazardous reagents and high-temperature processing. Structural and physicochemical characterization using X-ray diffraction (XRD), scanning electron microscopy (SEM–EDX), FT-IR, and UV–Visible spectroscopy confirmed the formation of phase-pure cubic nanocrystalline CaO with uniform morphology and good crystallinity. The photocatalytic performance of the biosynthesized CaO was evaluated through degradation of a textile dye under light irradiation. The material exhibited efficient catalytic activity, with degradation kinetics following a pseudo-first-order model, indicating favourable charge-transfer dynamics and enhanced reaction rates. To establish a theoretical–experimental correlation, density functional theory (DFT) calculations were performed to analyse optimized structure, electronic properties, and thermodynamic parameters. The calculated HOMO–LUMO energy gap (∼3.07 eV) supports the observed photocatalytic behaviour. Furthermore, simulated FT-IR and UV–Visible spectra showed strong agreement with experimental findings, validating the computational approach and confirming the electronic structure–activity relationship.
Agheda et al. (Thu,) studied this question.