Shape-Controlled Self-Assembly of Truncated Octahedral Nanocrystals into Supracrystals

Herein, we show that water molecules in apolar solvents would drive the assembly of inorganic nanocrystals into superstructures with increasing complexities that cannot be achieved in the absence of water. We show experimentally that trace amounts of water molecules in a nonpolar solvent can mediate the assembly of truncated octahedral nanocrystals with two different curvatures at the truncated vertex and the flat surface. In the presence of water molecules, these nanocrystals are able to assemble into uniform rhombic dodecahedra with a state of the art well-defined shape. Additionally, tuning the amount of water can direct the assembly of nanocrystals into superstructures with increasing complexities, exemplified as the elongation of rhombic dodecahedra into rods and clustering of four rhombic dodecahedra into supratetramers. Our results highlight the opportunities to engineer a nanocrystal assembling pathway enabled by a selective water permeation strategy.