Ce3+ and oxygen vacancy mediated tuning of structural and optical properties of CeO2 nanoparticles

Highlights: ► Ce3+ and oxygen vacancy regulate different properties of CeO2 nanoparticles. ► Structural distortion leads to generation of strain and expansion of lattice. ► Red shift in band gap is due to Ce3+ and oxygen vacancy. ► These oxygen vacancies and ceria related defects are responsible for visible luminescence. - Abstract: Ceria nanoparticles were synthesized by hydrolysis of cerium nitrate in basic medium. The cubic fluorite structure of ceria was confirmed by XRD. From TEM studies ceria nanoparticles were found to be spherical in shape with an average diameter of 5 nm. The prepared nanoparticles have a predominant orientation along (2 2 2) crystallographic plane. Oxygen vacancies and Ce3+ lead to the lattice expansion and strain in CeO2. Peak asymmetry and broadening of Raman active mode peak further confirms the presence of these defects. Total concentration of oxygen vacancies that are present in the ceria nanocrystallites is calculated to be 1.234 × 1020 cm−3. These oxygen vacancies and ceria related defects result in an effective red shifting of the band gap by changing its structural regularity. The visible luminescence peaks are also caused by these Ce3+ and oxygen vacancy centers.