Facet control of ceria nanocrystals synthesized by an oleate-modified hydrothermal method

• Ceria nanoparticles with controlled crystal orientations are fabricated.
• This is done via an oleate-modified hydrothermal method.
• The molar ratio of oleate ions to cerium ions ([Ole/Ce]) is varied from 0 to 1.
• For [Ole/Ce] > 1/2, we get quasicubic nanoparticles with primary {1 0 0} facets.
• For [Ole/Ce] < 1/4, we get polyhedral nanoparticles with primary {1 1 1} facets.

Ceria nanoparticles with controlled crystal orientations were fabricated via an oleate-modified hydrothermal method, which involved varying the molar ratio of oleate ions to cerium ions in the reaction solution ([Ole/Ce]) from 0 to 1. Quasicubic nanoparticles having primary {1 0 0} facets in addition to {1 1 0} edges were obtained for [Ole/Ce] values greater than 1/2. On the other hand, polyhedral nanoparticles surrounded by primary {1 1 1} facets appeared on nanoparticle surface at [Ole/Ce] smaller than 1/4. It was found that the bonding of the carboxyl terminals of the oleate ions with the cerium(IV) ions on the {1 0 0} surfaces balanced the electric charge of the stacked layers and that this is what resulted in the formation of cubic nanoparticles surrounded by {1 0 0} facets for [Ole/Ce] values larger than 1/2.

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