Interface-induced nucleation, orientational alignment and symmetry transformations in nanocube superlattices.
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.
School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, United States.
Joshua J
JJ
Choi
Kaifu
K
Bian
William J
WJ
Baumgardner
Detlef-M
DM
Smilgies
Tobias
T
Hanrath
D003460:Crystallization / Q000379:methods*; D007854:Lead / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D008968:Molecular Conformation; D010316:Particle Size; D018036:Selenium Compounds / Q000737:chemistry*; D013499:Surface Properties
D046911:Macromolecular Substances; D018036:Selenium Compounds; C088065:lead selenide; D007854:Lead