Interfacial activity of phosphonated-polyethylene glycol functionalized cerium oxide nanoparticles

TL;DR

This study demonstrates how phosphonated-PEG functionalized cerium oxide nanoparticles can modify interfaces and surfaces, enabling control over nanoparticle adsorption, assembly, and surface modification for various applications.

Contribution

It reveals the interfacial activity of functional ceria nanoparticles and their ability to form stable monolayers and multilayers, advancing surface modification techniques.

Findings

Nanoparticles can be tuned to adsorb at various interfaces.

Dense monolayers of nanoceria form spontaneously or via compression.

Reversible, hexagonally organized nanoceria monolayers are characterized by GISAXS.

Abstract

In a recent publication, we have highlighted the potential of phosphonic acid terminated PEG oligomers to functionalize strong UV absorption cerium oxide nanoparticles[1], which yield suspensions that are stable in aqueous or organic solvents and are redispersible in different solvent after freeze-drying. In the present work, we highlight the interfacial activity of the functional ceria nanoparticles and their potential to modify hydrophobic surfaces. We first investigated Phosphonated-PEG amphiphilic oligomers behavior as strong surface active species forming irreversibly adsorbed layers. We then show that the oligomers interfacial properties translate to the functional nanoparticles. In particular, the addition of a small fraction of phosphonated-PEG oligomers with an extra C16 aliphatic chain (stickers) into the formulation enabled the tuning of i) the nanoparticles adsorption at the air/water, polystyrene/water, oil/water interfaces and ii) the particle/particle interaction in aqueous solutions. We also found that dense and closely packed two dimensional monolayers of nanoceria can be formed by spontaneous adsorption or surface compression using a Langmuir trough. A hexagonal organization controlled by reversible and repulsive repulsion has been characterized by GISAXS. Mono- or multilayers can also be stably formed or transferred on solid surfaces. Our results are key features in the field of polymer surface modification, solid stabilized emulsions (Pickering) or supracolloidal assemblies.