Stabilization of Oil-Dispersible Nanoparticles in Different Organic Solvents: A Computational Study

Oleyl-capped nanoparticles have been used in nonpolar dispersions and can form ordered assemblies, for which an understanding of their interactions from a theoretical perspective is relevant. Long-range comprehensive molecular dynamics runs (1000 ns) are performed on oleyl-capped gold nanoclusters in different environments: hexane as a nonpolar solvent, and ethanol and pentanol as polar solvents. The molecular dynamics results in ethanol medium demonstrate that oleyl-capped nanoclusters tend to form attractive interactions with themselves via hydrocarbon interdigitation of their oleyl ligands, which leads to their aggregation. On the contrary, the attractive interactions between these nanoclusters are compensated by the interactions with hexane molecules, so that the nanoclusters keep separated from each other, leading to stable dispersions. The behavior of pentanol with the oleyl-capped nanoclusters indicates presumably more similarities to hexane, despite of being a polar solvent. These three simulation cases provide an insightful overview about the stabilization effects of oleyl-capped nanoparticles in organic solvents.