Self-organization of Te nanorods into V-shaped assemblies: a Brownian dynamics study and experimental insights.

Computer modeling of nanoscale processes provides critical quantitative insights into nanoscale self-organization, which is hard to achieve by other means. Starting from a suspension of Te nanorods, it was recently found that short nanorods (50 nm) self-organized into checkmark-like V-shaped assemblies over a period of a few days, whereas long nanorods (2200 nm) did not. This experimental fact was difficult to explain, and so here we use Brownian dynamics simulations of a dilute suspension of hard spherocylinders to better understand the process of self-organization. With the assumption that close encounters between nanorod tips result in their merger into V-particles, it was found that the ratio of the initial rate of nanorod formation for the short and long rods was 3760. By systematically varying the length and the concentration, we found that the concentration of the nanorods, rather their length, was primarily instrumental in setting the initial rate of checkmark formation. Using a simple kinetic model in conjunction with experimental data, we find that approximately 30,000 close encounters are required on average for a single successful merger. This study gives an important reference point for understanding the mechanism of the formation of complex nanostructured system by oriented attachment; it also can be extended to and provides conceptual leads for other self-organized systems.