R. Zarei Moghadam, Amir Hossein Farahani, Davood Nasrabadi, Abbas Ziari
Cerium oxide nanoparticles (CeO 2 NPs) were successfully synthesized via an environmentally friendly route using combined strawberry ( Fragaria × ananassa ) and mulberry ( Morus nigra ) extracts, followed by calcination at 400, 500, and 600 °C. This study systematically investigates the influence of calcination temperature on the structural, morphological, optical, photocatalytic, and biological properties of green-synthesized CeO 2 nanoparticles. Structural characterization by XRD, FTIR, FESEM, UV–Vis spectroscopy, and zeta potential analysis confirmed the successful formation of crystalline CeO 2 nanoparticles and revealed that calcination temperature markedly affected crystallinity, particle size, surface characteristics, and optical behavior. The sample calcined at 500 °C exhibited a quasi-spherical morphology with an average particle size of 44.74 nm and a high positive zeta potential (+ 63.82 mV), indicating good colloidal stability. Among the investigated samples, the 500 °C nanoparticles demonstrated the highest photocatalytic performance, achieving 71.8% degradation of methylene blue within 40 min under UV irradiation with a pseudo-first-order rate constant of 0.1151 min −1 . Furthermore, MTT assays using 3T3 fibroblast cells showed more than 90% cell viability at concentrations below 16 µg mL −1 , indicating favorable cytocompatibility at low doses. The enhanced performance of the 500 °C sample is attributed to the optimized balance between crystallinity, particle growth, and surface characteristics achieved through controlled calcination. Overall, this work demonstrates that calcination temperature plays a critical role in tailoring the physicochemical properties and multifunctional performance of green-synthesized CeO 2 nanoparticles, providing valuable insights into the design of sustainable nanomaterials for environmental remediation and potential biomedical applications.