Effect of acetate ions and pH on the morphology of cerium oxide nanoparticles

Cerium oxide nanoparticles (CeNPs) are recognized as functional materials with suitability in diverse applications. Conventional synthesis of CeNPs involves direct addition of alkaline solutions and/or precipitating agents to cerium solutions. Rapid changes in solution concentrations and ligand introduction result in less control over particle size and dispersity. Here, we report a simple hydrothermal synthesis of cubic shaped CeNPs through homogenous precipitation, achieved by introduction of acetate molecules. A distinct trend in CeNPs transitioning from octahedral to cubic morphologies was observed through a series of experiments. Results from experimental and computational studies have demonstrated that acetate plays an important role in directing the morphological transition of CeNPs and providing a pH-buffered environment. The formation of Ce(IV)-acetate complexes not only stabilizes aqueous Ce(IV) but also inhibits its hydrolysis in conditions of lower pH. The stabilization of Ce(IV) ions is also favorably weakened during the hydrothermal treatment, leading to successful homogeneous precipitation and the formation of mono-dispersed cubic-shaped CeNPs.