Size‐Dependent Self‐Assembly of Anisotropic Silica‐Coated Hybrid Nanoparticles

The self-organization of colloids into defined structures offers the possibility to develop novel materials with exciting properties. However, this requires the understanding and application of the forces governing interparticle association. A novel approach for a size-dependent anisotropic assembly between nanoparticles is achieved. Janus-like iron oxide/polystyrene hybrid nanocolloids are prepared by heterophase polymerization and selectively coated with silica on the iron oxide face to gradually form a cavity. Hence, a shallow surface around the hydrophobic polymer face is created, enabling smaller particles of the same nature to be locked by shape complementarity and colloidal steric stabilization. Further coating with silica fixes these assemblies and allows quantitative analysis of the interaction on a nanoscale.