Supercrystal structures of polyhedral PbS nanocrystals.

The construction of supercrystals with non-spherical building blocks has attracted increasing attention due to their potential applications in the fabrication of novel devices. In this study, we report the large-scale preparation of dimension-controllable supercrystals of polyhedral PbS nanocrystals through a solvent evaporation approach. Because of the capillary flow of the drying droplet on the substrate, nanocrystals self-assemble into three distinct types of supercrystals on specific regions of the substrate during the solvent evaporation: two-dimensional supercrystals appear in the central region; three-dimensional faceted supercrystals and three-dimensional bulk supercrystals are found near the edge of the substrate. Moreover, the formation of superlattice structure of each type of supercrystals can be tuned by changing the shape of building blocks. The influences of experimental factors on self-assembly are investigated as well. We anticipate that our research can provide some new insights into the construction of supercrystals with novel structures and large sizes.