Ultrasmall monodisperse 2.3 nm CeO2 nanoparticles have been synthesized by simple ammonia precipitation of cerium nitrate in a mixed glycol–water solvent and phase transferred into apolar solvents. Cerium oxide crystal surfaces were passivated with oleic acid (OA) by reflux under ambient pressure conditions. OA molecules were chemisorbed on the ceria nanoparticle surfaces. Preferential growth of the {100} planes has been observed, ascribed to restricted growth of {111} faces due to adsorbed OA. The surfacted CeO2 nanoparticles were dispersed into a stable, colloidal suspension of fine particles in hydrocarbon solvents. The CeO2 nanocrystals were characterized by X-ray diffraction, Fourier transform infrared spectra, and Raman spectral methods. Transmission electron microscopic images and photon scattering studies proved that the colloidal particles in hydrocarbon solvent were indeed monocrystalline with one crystallite per particle, monodispersed with a narrow size distribution.

The catalytic performance of a range of nanocrystalline CeO2 samples, prepared to have different morphologies, was measured using two accepted indicators; oxygen storage and diesel soot combustion. The same powders were characterized in detail by HR-TEM, XRD, XPS, and Raman methods. The study demonstrates that activity is determined by the relative fraction of the active crystallographic planes, not by the specific surface area of the powders. The physical study is a step toward quantitative evaluation of the relative contribution to activity of the different facets. The synthetic protocol permits fabrication of CeO2 nanostructures with preferentially grown active planes, and therefore has potential in developing catalytic applications and in nanocompositing.

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