Cerium oxide (CeO₂) nanoparticles (NPs) were synthesized using a hydrothermal method. The structural, morphological, optical, and surface properties of the synthesized nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–Visible spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and Brunauer–Emmett–Teller (BET) surface area analysis. XRD analysis confirmed the formation of a cubic fluorite crystal structure with a space group of Fm-3m. The optical band gap energy of the CeO₂ nanoparticles, determined from UV–visible analysis, was found to be 2.85 eV. The photocatalytic activity of the synthesized nanoparticles was evaluated through the degradation of congo red (CR) dye under visible light irradiation. Complete degradation of congo red was achieved within 60 minutes of visible light exposure at room temperature under alkaline conditions (pH 10), demonstrating superior photocatalytic efficiency. The antimicrobial activity of the CeO₂ nanoparticles was investigated against Escherichia coli, Candida albicans, Aspergillus niger, and Fusarium spp. The results revealed significant antimicrobial activity against the tested microorganisms. Overall, the findings indicate that CeO₂ nanoparticles synthesized via the hydrothermal method exhibit excellent photocatalytic and antimicrobial properties, highlighting their potential as multifunctional materials for various environmental and biomedical applications.

Keywords: CeO₂; Hydrothermal; Dye Degradation; Antimicrobial Activity;