Solvent-mediated interactions between nanoparticles at fluid interfaces

We investigate the solvent-mediated interactions between nanoparticles adsorbed at a liquid-vapor interface in comparison to the solvent-mediated interactions in the bulk liquid and vapor phases of a Lennard-Jones solvent. Molecular dynamics simulation data for the latter are in good agreement with results from integral equations in the reference functional approximation and a simple geometric approximation. Simulation results for the solvent-mediated interactions at the interface differ markedly from the interactions of the particles in the corresponding bulk phases. We find that at short interparticle distances, the interactions are considerably more repulsive than those in either bulk phase. At long interparticle distances we find evidence for a long-ranged attraction. We discuss these observations in terms of interfacial interactions, namely, the three-phase line tension that would operate at short distances and capillary wave interactions for longer interparticle distances.