title: Size-dependent multiple twinning in nanocrystal superlattices.
abstract: We report a size-dependent change in the morphology of superlattices self-assembled from monodisperse colloidal PbS nanocrystals. Superlattices of large (>7 nm) PbS nanocrystals showed a strong tendency to form multiply twinned face-centered cubic superlattices with decahedral and icosahedral symmetry, exhibiting crystallographically forbidden five-fold symmetry elements. On the other hand, superlattices of small (<4 nm) PbS nanocrystals exhibited no twinning. To explain such a dramatic difference in the twinning probability, we showed that twinning energy in a nanocrystal superlattice is strongly size-dependent. In addition, the interparticle potentials acting during the self-assembly process are "softer" in the case of larger PbS nanocrystals, thus favoring the formation of multiply twinned superlattices. Our work introduces a new class of materials exhibiting multiple twinning, while offering flexibility in designing interparticle potentials.
authors.affiliation: Department of Chemistry, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Sara M
authors.initials: SM
authors.lastname: Rupich
authors.forename: Elena V
authors.initials: EV
authors.lastname: Shevchenko
authors.forename: Maryna I
authors.initials: MI
authors.lastname: Bodnarchuk
authors.forename: Byeongdu
authors.initials: B
authors.lastname: Lee
authors.forename: Dmitri V
authors.initials: DV
authors.lastname: Talapin