Low-frequency Raman scattering from CeO2 nanoparticles

Raman scattering measurements were performed on CeO2 nanoparticles at room temperature. Low-frequency modes are assigned to confined acoustic vibrations of spherical CeO2 nanoparticles. Frequencies of these vibrational modes have been calculated in the elastic continuum approximation, which considers a nanoparticle as a homogeneous elastic sphere. We assumed stress-free boundary conditions. The specific dependence of the vibrational frequency on the particle diameter enables the determination of the particle size from the experimental Raman frequency. The particle size value calculated in this way agrees well with the value acquired from the phonon confinement model.