Novel sol-gel synthesis of CeO₂ nanoparticles using Morinda citrifolia L. fruit extracts: Structural and optical analysis

An efficient and eco-friendly sol-gel method using Morinda citrifolia L. fruit extracts as a weak base source, oxidizing, and capping agents were reported to synthesize cerium oxide nanoparticles (CeO₂ NPs). CeO₂ NPs exhibited the FCC crystal phase and the nanospherical shape with an average size of 51.6 nm. FT-IR characterization presented the absorption band of Ce–O at 705 cm⁻¹ and the stretching vibration of N-H amine, which plays a crucial role in CeO₂ NPs synthesis. The optical analysis revealed a strong optical absorption of CeO₂ NPs at 351 nm with a bandgap value of 3.48 eV. Furthermore, the optical analysis of CeO₂ NPs was further tested for the UV light absorption ability via methylene blue degradation. As a result, CeO₂ NPs pointed out a low photocatalytic property with an efficiency of 10.25 and 9.46 % under UV_A and UV_B light irradiation for 15 h, respectively. Meanwhile, CeO₂ NPs had good optical properties on their photoabsorption ability toward UV_A and UV_B light with an efficiency of 89.27 and 67.55 %, respectively.