Modeling the Orientational and Positional Behavior of Polyhedral Nanoparticles at Fluid-Fluid Interfaces
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 thickness of the interface can introduce non-trivial effects on the preferential particle orientations. A continuum model is proposed to account for the finite interfacial mixing region, and a qualitative comparison between the two approaches 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 analyses to the attachment of two particles. Our results reveal conditions that can drive the assembly of Cuboctahedra into either 2D Puckered Honeycomb lattices or linear rod-like structures.
Free energy; Interface; Umbrella sampling; Molecular Dynamics; Self Assembly; nanoparticle; Chemical engineering
Steen, Paul Herman; Hanrath, Tobias
M.S., Chemical Engineering
Master of Science
dissertation or thesis