Spontaneous asymmetry of coated spherical nanoparticles in solution and at liquid-vapor interfaces.

Spherical nanoparticles (NPs), uniformly coated with a simple polymer used to passivate NPs in solution, are shown to produce highly asymmetric coating arrangements. We show that a class of spherical particles is not symmetrically coated even when extremely uniform grafting arrangements and full coverages are employed. We demonstrate, using explicit-atom molecular dynamics simulations of model NPs, that geometric properties dictate when a coating's spherical symmetry will be unstable and show that the chain end group and the solvent play a secondary role in determining the properties of surface patterns. At the water-vapor interface the coatings are significantly distorted and oriented by the surface. These asymmetric and oriented coatings are expected to have a dramatic effect on the interactions between NPs and will likely influence the structures of aggregated NPs which self-assemble in the bulk and at surfaces.