Structural characteristics of quantum-size ceria nano particles synthesized via simple ammonia precipitation

Nanoscale, high surface area spherical cerium oxide was prepared from aqueous cerium nitrate by homogeneous precipitation using ammonia. This synthesis route offers a versatile, low cost and environmental friendly method to produce nano ceria. The specimen powder was characterized with XRD, SEM, HRTEM, and UV–vis spectrophotometry. Cubic cerianite crystallites (CeO2) were detected by powder XRD pattern, while Ce3+ was also evident from XPS spectra and DR UV spectroscopy study. XPS spectra indicated that cerium in the nano crystals was predominantly tetravalent. Both Ce2O3 as well as oxygen vacancy contributed towards the presence of Ce3+ in the sample. The particle size of the system was calculated from TEM analysis, XRD study and BET surface area analysis. The characterization revealed the particles to be spherical in shape with typical size 4–5 nm, which is a favourable characteristic feature for many applications. The direct optical band gap estimated from DR UV absorption spectrum was blue-shifted evidently with respect to the bulk material and indicated quantum-size confinement effect in nano crystallites.