Dispersion of fatty acid surface modified ceria nanocrystals in various organic solvents

Ceria (CeO₂) nanocyrstals which could be transparently dispersed in several organic solvents were synthesized by organic-ligand-assisted hydrothermal synthesis. We have studied the dispersity of the nanocrystals into typical organic solvents using dynamic light scattering (DLS) measurement. The mean diameter of the dispersant (the nanocrystals' cluster) varied with changing the solvent species. When the solubility parameter (SP) values of the solvent and the modifier were comparable to each other, the nanocrystals tended to disperse in the solvent with the initial particle size. One of the three-dimensional SPs, i.e., the Hansen solubility parameters, brought more detailed understanding of the mechanism of the dispersion of the surface modified nanocrystals. Because of the dense modifier layer on the surface of the ceria nanocrystals, the hydrogen bonding ability of the solvent was not the dominant factor to determine dispersion of the surface modified nanocrystals. The dispersion and polar factors of the Hansen SPs could describe the ideal condition of perfect dispersion of the surface modified CeO₂ nanocrystals.