Pressure-dependent structure and mechanics of grafted gold nanoparticle superlattices

Recent experiments have demonstrated synthesis of various gold nanostructures—e.g. nanowires, nanorods and nanosheets—through compression of self-assembled superlattices of polymer-grafted gold nanoparticles. The magnitude and direction of compression required to synthesize a certain nanostructure critically depend upon the mechanical properties of the superlattice. Using MD simulations, we examine the microstructure and mechanics of self-assembled fcc superlattices of alkanethiol-coated gold nanoparticles. We characterize the elastic moduli of these superlattices at various hydrostratic pressures up to 10GPa, as a function of ligand length, ligand grafting density, size of the gold core, and gold-sulfur bond strength. We establish that ligand microstructure and ligand migration on the gold surface crucially governs the emergent mechanical properties of the superlattice. These observations provide key inputs for optimizing compression driven synthesis of gold nanostructures.
Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.