Effect of pH on the structural, morphological, and optical properties of cerium oxide nano-thin films prepared by the hydrothermal method

Cerium oxide (CeO 2 ) Nano-thin films on a seed layer were synthesized via the hydrothermal method at pH 3 and 9. The structural, morphological, and optical characteristics of the produced films were investigated. X-ray diffraction (XRD) tests showed that the prepared films are polycrystalline and have a cubic structure. Additionally, they have a crystallite size of approximately 14.5 nm and a pH of 3. Increasing the pH to 9 reduced the crystallite size to 12.9 nm. Field-emission scanning electron microscopy (FESEM) images revealed that changing the pH resulted in a reduction in the size of the nanoparticles, while maintaining their spherical shape. Energy-dispersive X-ray Spectroscopy (EDS) analysis confirmed the absence of impurity elements in the prepared samples, verifying the formation of pure cerium oxide. UV-vis examinations showed that increasing the pH value of the prepared films enhanced the optical transmittance and increased the values of the optical energy gap.