  Rare earth cerium oxide (ceria) nanoparticles are stabilized using
end-functional phosphonated-PEG oligomers. The complexation process and
structure of the resulting hybrid core-shell singlet nanocolloids are
described, characterized and modeled using light and neutron scattering data.
The adsorption mechanism is non-stoichiometric, yielding the number of adsorbed
chains per particle Nads = 270 at saturation. Adsorption isotherms show a high
affinity of the phosphonate head for the ceria surface (adsorption energy ~ -16
kT) suggesting an electrostatic driving force for the complexation. The ease,
efficiency and integrity of the complexation is highlighted by the formation of
nanometric sized cerium oxide particles covered with a well anchored PEG layer,
maintaining the characteristics of the original sol. This solvating brush-like
layer is sufficient to solubilize the particles and greatly expand the
stability range of the original sol up to pH = 9. We underscore two key
attributes of the tailored sol: i) strong UV absorption capability after
functionalization and ii) ability to re-disperse after freeze-drying as powder
in aqueous or organic solvents in varying concentrations as singlet
nanocolloids. This robust platform enables translation of intrinsic properties
of mineral oxide nanoparticles to critical end use.
