Urea and surfactant assisted hydrothermal growth of ceria nanoparticles

Cerium oxide nanoparticles were prepared via a modified hydrothermal approach to reduce the reaction durations in the conventional hydrothermal route. Urea and NaOH were used together for the fast growth of ceria nanocubes within a short reaction period. The formation of Ce-O-Ce bonds to grow CeO2 nuclei with the help of urea, and the anisotropic growth in the base medium led to the formation of nanocube morphology. Cetyltrimethylammonium bromide (CTAB) was added further in the precursor solution as a capping and structure directing agent that directed the growth of ceria nanostructures from spherical to irregular polygonal morphology. Ceria nanocubes of 18-20 nm sizes with highly reactive (1 0 0) faces were formed after hydrothermal reaction. On the other hand, CTA(+) group reduced the particle sizes to 8-10 nm with the (1 1 1) exposed stable faces. In addition, ceria nanostructures obtained with the assistance of surfactants show intrinsic oxygen vacancies and enhanced concentrations of Ce3+ in cubic fluorite structure. Furthermore, band gap and Urbach energy calculations show that the increase in structural disorder and contribution of the defects in ceria morphologies of the order: nanocubes < nanoplates < polygonal nanostructures < nanospheres. The present research indicated a novel approach to synthesize ceria nanoparticles within short reaction durations.