Redispersible Hybrid Nanopowders: Cerium Oxide Nanoparticle Complexes with Phosphonated-PEG Oligomers

TL;DR

This paper presents a method to stabilize cerium oxide nanoparticles with phosphonated-PEG oligomers, creating hybrid nanocolloids with enhanced stability, UV absorption, and re-dispersibility, suitable for various applications.

Contribution

The study introduces a novel hybrid core-shell nanocolloid with non-stoichiometric adsorption and high stability, expanding the functional utility of cerium oxide nanoparticles.

Findings

High affinity of phosphonate for ceria surface (~ -16 kT)

Stable nanocolloids with PEG layer up to pH 9

Re-dispersible powders retaining nanoparticle properties

Abstract

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.