Green synthesis of TiO₂, Fe₂O₃, CuO, and ZnO nanoparticles using Lepidagathis ushae leaf extract for photocatalytic dye degradation

Abstract

Green synthesis of metal oxide nanoparticles has gained significant attention as a sustainable alternative to conventional chemical methods for environmental remediation. In the present work CuO, TiO₂, Fe₂O₃ and ZnO nanoparticles (NPs) were successfully synthesized using Lepidagathis ushae leaf extract, reported for the first time as an effective green reducing and stabilizing agent. The synthesized nanoparticles were thoroughly characterized by UV–Diffuse Reflectance Spectroscopy (UV-DRS), X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), High resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET) analysis, Photoluminescence (PL) and X-ray Photoelectron Spectroscopy (XPS). The XRD confirming their phases and crystalline size. The SEM and EDX images indicated a quasi-spherical, irregular, spherical shape and Nano rod like structure for CuO, Fe 2 O 3 , TiO 2 and ZnO NPs respectively. The UV–Diffuse Reflectance Spectroscopy revealed a band gap energy 3.16, 2.05, 3.20 and 3.18 eV for CuO, Fe₂O 3 , TiO₂ and ZnO NPs. In the present study photocatalytic performance of the synthesized NPs were evaluated through the degradation of methylene blue (MB) and rhodamine B (RB) under irradiation. Among the catalysts, TiO₂ (P8) exhibited superior activity toward MB degradation, achieving 77.8% removal within 90 min under sunlight and CuO (C3) degraded 79.24% RB dye. It was observed that spherical shaped CuO and TiO2 nanoparticles show a better degradation efficiency as compared to densely packed and rod like structure of Fe 2 O 3 and ZnO NPs. The comparative results indicate that photocatalytic efficiency is strongly dye-dependent not only band gap and surface area. The study further elucidates the influence of key parameters such as catalyst composition (CuO, Fe 2 O 3 , TiO 2 and ZnO), dosage (0.05–0.25 mg) and pH (2−12) on dye degradation efficiency. Overall, the findings demonstrate that Lepidagathis ushae -mediated metal oxide nanoparticles are sustainable, eco-friendly and effective for breaking down harmful environmental contaminants within 90 min.