By mixing uniform large and small nanocrystals (NCs), three-dimensional (3D) crystalline structures referred to as supracrystals (SCs) are produced. The small NCs fill in the interstices of large NCS self-assembled in well-defined patterns. Various binary structures are produced, in specific conditions, as predicted by a hard-sphere model. It is demonstrated that the ligands used to stabilize NCs play the role of a key parameter in the final structure, as well as the crystalline structure of the NCs, called nanocrystallinity, with production of one-component SCs characterized by vicinal surfaces. Quasi-binary SCs are produced either by a ligand exchange process during the SC growth or through magnetic forces. Using magnetic NCs having two different diameters shows unexpected destructive magnetic property.
Source : 3D superlattices of uniform metal nanocrystals differing by their sizes called binary supracrystals J.Wei, Z. Yang, and MP.Pileni, EPL, 2017, 119, 38005