Fast development of colloidal chemistry has enabled the synthesis of monodisperse nanocrystals with controlled sizes, shapes, and structures. The well-defined nanocrystals can be used as building blocks to create ordered superstructures with emergent functionalities through bottom-up approaches. These approaches often rely on carefully controlled assembly of pre-synthesized nanocrystals at low temperatures. In contrast to conventional approaches, this talk discusses the rapid growth (within seconds) of face-centred-cubic three dimensional nanocrystal superlattices during colloidal synthesis at high temperatures (more than 230 <sup>o</sup>C). Using <i>in situ</i> small-angle X-ray scattering, we observe continuous growth of individual nanocrystals within the lattices, which results in simultaneous lattice expansion. Thermodynamic models demonstrate that balanced attractive and repulsive interparticle interactions dictated by the ligand coverage on nanocrystal surfaces and nanocrystal core size are responsible for the crystallization process. The interparticle interactions can also be controlled to form different superlattice structures, such as hexagonal close-packed lattices. These results demonstrate a new type of nanocrystal interactions during colloidal synthesis and provide new insights into assembly of nanocrystals into superstructures for different applications.

High-temperature crystallization of nanocrystals into three-dimensional superlattices

2019 Spring National Meeting

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