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 as-prepared 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.