(372h) Molecular Dynamics Simulations of Alkanethiol-Coated Gold Nanoparticles

Bolintineanu, D. S., University of Minnesota
Grest, G. S., Sandia National Laboratories

We summarize the results of a series of fully atomistic molecular dynamics simulations of alkanethiol- coated gold nanoparticles solvated in water. First, we discuss simulations of individual nanoparticles, and analyze the structure of the coatings as a function of various functional end groups and the lengths of the alkanethiol chains. For the longer alkanes we find significant local phase segregation of chains on the nanoparticle surface, which results in highly asymmetric coating structures. In general, charged end groups attenuate this effect by enhancing the water solubility of the nanoparticles. We next report the behavior of these nanoparticles at a water-air interface, and infer solubility based on their tendencies to penetrate into the water phase. Finally, we discuss results of recent simulations of assemblies of nanoparticles at an air-water interface. Experiments have shown that evaporation of solvent will cause such particles to self-assemble into a close-packed hexagonal lattice and form membranes with unusual mechanical and optical properties. Quantitative comparisons between simulations and the experimental systems are favorable. The simulations provide detailed insights into the structure and properties of the resulting membranes, and suggest several explanations for their unique properties.