Supercrystals from crystallization of octahedral MnO nanocrystals

Guided by the concept of regarding nanoparticles as superatoms or supermolecules in colloidal solution, we design a facile crystallization approach for preparation of 3D supercrystals (SCs). Dispersive states of asprepared MnO nanocrystals (NCs) in solvents of cyclohexane and ethanol were studied to illuminate the effects of solvents. Ethanol was demonstrated to be the most appropriate solvent, and a large amount of microscale cubic SCs built by octahedral MnO NCs was created via direct crystallization. Although two types of packing structures are well-defined, the MnO SCs prefer the one with the higher packing efficiency of 88.89% for minimizing system energy. The crystallization process undergoes a dynamic attachment and exchange mechanism.