Monte Carlo Simulation on the Assembly of Nanorods with Anisotropic Interactions

The assembly of nanorods with anisotropic interactions in dilute solution is studied using lattice dynamic Monte Carlo simulation. Each nanorod consists of two different beads with one lattice length apart. The anisotropic interactions are of orientational dependence, and two kinds of nearest-neighbor interactions are considered: (a) side-to-side attraction epsilon(xy) when two nanorods are parallel with head-head and tail-tail being nearest-neighbors and (b) end-to-end attraction epsilon(z) when they are in end-to-head alignment. Three structures, wire, sheet, and pillar, are assembled by slowly cooling the system. Nanowires are assembled at large ratio r = epsilon(z)/epsilon(xy), while sheets are assembled at small r. At intermediate values of r, three-dimensional (3D) pillars are formed. The aspect ratio A of the 3D pillar increases with r, which can be expressed as A = 0.238r(2.13 +/- 0.05). The exponent is different from that of theoretical calculation, which is probably caused by a kinetic effect.