Dispersion of Oleate-modified CeO2 Nanocrystals in Non-Polar Solvent and Aqueous Solution

Abstract

Oleate-modified CeO2 nanocrystals with the size of 2-7 nm were synthesized by a hydrothermal treatment. Characterization of the nanocrystal was performed by XRD, TEM, and IR analyses. Dispersion states of the hydrophobic CeO2 nanocrystals were investigated in toluene and several types of alkaline aqueous solution such as KOH, TMAH, and ammonia solution, and different dispersion modes were observed. Toluene and strongly basic aqueous solution gave excellent transparent dispersion liquids, while the weakly basic solution resulted in the turbid dispersion indicating the formation of large micelles. The particle-size distribution measurement by the DLS method and the surface-potential measurement suggested the dispersion mechanism of CeO2 nanocrystals and clarified the micelle formation process in aqueous solution.