Orientational Ordering of Passivating Ligands on CdS Nanorods in Solution Generates Strong Rod-Rod Interactions

We present the first nearly atomistic molecular dynamics study of nanorod-nanorod association in explicit solvent, showing that inter-rod forces can be dominated by microscopic factors absent in common continuum descriptions. Specifically, we find that alkane ligands on faceted CdS nanorods in n-hexane undergo a temperature-dependent order-disorder transition akin to that of self-assembled monolayers on macroscopic substrates. This collective ligand alignment organizes nearby solvent molecules, strongly influencing the statistics of rod-rod separation. The strong temperature-dependence of this mechanism could be exploited in the laboratory to manipulate and optimize the assembly of ordered structures.