Interface-Induced Nucleation, Orientational Alignment and Symmetry Transformations in Nanocube Superlattices

Joshua J. Choi, Kaifu Bian, William J. Baumgardner, Detlef-M. Smilgies, Tobias Hanrath

Research output: Contribution to journalArticlepeer-review

74 Scopus citations


The self-assembly of colloidal nanocrystals into ordered superstructures depends critically on the shape of the nanocrystal building blocks. We investigated the self-assembly of cubic PbSe nanocrystals from colloidal suspensions in real-time using in situ synchrotron-based X-ray scattering. We combined small-angle and wide-angle scattering to investigate the translational ordering of nanocrystals and their orientational ordering in the lattice sites, respectively. We found that cubic PbSe nanocrystals assembled into a face-up (i.e., 〈100〉 normal to the interface) configuration at the liquid/substrate interface whereas nanocubes at the liquid/air interface assume a corner-up (i.e., 〈111〉 normal to the interface) configuration. The latter nanocrystal superlattice displays polymorphism as a function inter-NC separation distance. We explain the observed superlattice structure polymorphs in terms of the interactions directing the self-assembly. Insights into the directed self-assembly of superlattices gained from this study have important implication on the future development of nanocrystals as building blocks in artificial solids. © 2012 American Chemical Society.
Original languageEnglish (US)
Pages (from-to)4791-4798
Number of pages8
JournalNano Letters
Issue number9
StatePublished - Aug 17 2012
Externally publishedYes


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