A Novel Aqueous Route To Fabricate Ultrasmall Monodisperse Lipophilic Cerium Oxide Nanoparticles

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