Magnetic field-directed self-assembly of FePt-based nanoparticles at the liquid-air interface

The self-assembly of nanoparticles is a prominent strategy for fabricating nanomaterials and nanodevices. Herein, FePt-based nanoparticles are self-assembled at a diethylene glycol-air interface, under an applied in-plane static magnetic field. The effect of the field on the self-assembly is apparent at a field strength of 60 mT, whereby nanoparticles arranged into randomly oriented nanoparticle chains. Increasing the field strength to 90-120 mT resulted in the nanoparticle chains becoming increasingly disintegrated, and large islands form at the expense of the uniform nanoparticle monolayer. The pattern arising from self-assembly is described based on the drag force and ligand-ligand interactions, which compete with van der Waals forces and magnetic dipole interactions induced by the applied magnetic field. (author)