Fine-tuning the assembly of highly stable oppositely charged ceriumoxide nanoparticles in solution and at interfacesSribharani

tIn this work we have shown how to fine-tune the electrostatic assembly of oppositely charged ceriumoxide nanoparticles (NPs) in a solution and at a solid/liquid interface. In a first stage, we have developedanionic and cationic CeO2NPs stable in a highly saline environment and a wide pH range via efficientelectro-steric interactions. Anionic NPs were obtained by coating bare NPs with short polyacrylic acid(PAA) chains through a Precipitation-Redispersion method. Whereas cationic NPs were formulated bytethering branched polyethyleneimine (bPEI) chains onto PAA-coated ceria NPs through the formation ofamide bonds with the help of imide cross-linkers. The covalent attachment of bPEI chains was evidenced through NMR characterizations while thermogravimetric (TGA), dynamic light scattering (DLS) and zetapotential measurements confirmed the successful encapsulation by both types of weak polyelectrolytes.In a second stage, the high stability of both NP dispersions toward high ionic strength (up to 4 M NH4Cl)enabled to generate hybrid clusters in a controlled way by fine tuning their co-assembly following adesalting transition route monitored by DLS. In a last part, we have extended our approach to surfaces andgenerated all-nanoparticle layer grown directly from a liquid/solid interface monitored by Quartz CrystalMicrobalance (QCM)...