Molecular-Dynamics Simulation of Colloidal Nanoparticle Forces

Molecular-dynamics simulations are utilized to simulate solvation forces between two nanoparticles immersed in a Lennard-Jones liquid. Four different sizes and shapes of solvophilic nanoparticles are investigated. For nanoparticles at a fixed orientation, we find that the solvation forces oscillate between attraction and repulsion as the particle separation is increased. Small nanoparticles can rotate rapidly under the influence of solvation forces and achieve relative orientations that minimize the free energy. Our results indicate that surface roughness can control nanoparticle alignment in a solvophilic colloidal suspension and that selective colloidal assemblies can be achieved by choosing nanoparticles with certain textures and/or shapes.