Self-assembled honeycomb networks of gold nanocrystals

Size-monodisperse 35 Angstrom diameter, sterically stabilized gold nanocrystals self-assemble into hexagonal networks, or two-dimensional honeycombs, during drop casting of a dispersion onto a substrate under the appropriate conditions. By changing the nanocrystal concentration prior to deposition, the microscopic morphology of self-assembled nanocrystal structures can be tuned from rings at high concentrations to honeycombs at low concentrations. The temperature dependence of the surface tension of the gold nanocrystal dispersions was measured using a ring tensiometer and found to depend on the particle concentration, particle size, and distribution. The morphological transition from rings to honeycombs appears to occur due to a transition from diffusive to convective fluid flow during solvent evaporation, which results directly from the surface tension and thermal conductivity differences between the dispersions.