Nanostructured Assembly of Magnetic and Plasmonic Nanoparticles Transferred from AOT Winsor Phases to Oil-in-Water Functional Dispersions

Abstract

Nanoparticle interactions can mediate assemblies and self-organization into colloidal superstructures, if then control of the size and stabilization is highly required towards the fabrication of functional nanomaterials. In the proposed approach, different types of water-dispersible and oil-dispersible nanoparticles were incorporated in water-in oil (w/o) microemulsions stabilized by Aerosol-OT (AOT) as surfactant. Phase separation at higher surfactant and water contents resulted in the formation of a heterocoagulate, which can be separated with an external magnet. This magnetic heterocoagulate, which can contain 3 different types of nanoparticles, can be dispersed in longer-chain carboxylic acids. An additional phase-transfer into oil-in water (o/w) dispersions was mediated by an auxiliary surfactant in water-ethanol. The resulting nanostructures from heterocoagulates formed at higher temperatures consisted on inner domains of water-dispersible nanoparticles embedded in a matrix-shell of oleyl-capped nanoparticles. Thus, a new encapsulation strategy is achieved under relative mild conditions, combining three types of nanoparticles and providing compartmentalization and magnetic-responsiveness.