Substrate directed self-assembly of anisotropic nanoparticles

We present a molecular dynamics study on the self-assembly of anisotropic nanoparticles-triangles and tetrahedrons on a flat surface. We observe ordered and disordered aggregates of nanoparticles depending on the particle-particle and surface-particle interactions. Anisotropic particles induce directionality in the assembly process. In particular, a cross over from the isotropic (spherical) assembly to the anisotropic (non-spherical) assembly of nanoparticles is identified as their size increases for weak nanoparticle-surface interactions. However, at strong nanoparticle-surface interactions, clusters of nanoparticles grow uniformly on the surface. We present phase diagrams that depict all possible structures of triangles and tetrahedrons depending on their size (L) and the nanoparticle-surface interaction strength (εns). We show a disorder to order transition in the L−εns plane, as L and εns increase.