Modeling the orientational and positional behavior of polyhedral nanoparticles at fluid-fluid interfaces

Abstract

Using molecular dynamics simulations to explicitly model fluid molecules, we study the effect of solvent wetting on the behavior of polyhedral nanoparticles at a fluid-fluid interface. First, we quantify the positional and orientational free-energy characteristics of an isolated nanoparticle. Our results suggest that the structure of the interface can introduce nontrivial effects on the preferential particle orientations. A continuum model is proposed to account for the finite-interfacial mixing region, and a qualitative comparison with the molecular simulation results is presented. We examine the effect on the free energy of the system of changes in the particle's solvation preference towards one fluid, and the degree of miscibility between the two fluids. By tuning these interaction parameters, we can potentially access and favor different orientations for the particle shapes examined. Further, we extend the insights gained from single-particle behavior to the attachment of two particles. Our results reveal conditions that could drive the assembly of cuboctahedra into either two-dimensional puckered honeycomb lattices or linear rodlike structures.