title: Controlling nanocrystal superlattice symmetry and shape-anisotropic interactions through variable ligand surface coverage.
abstract: The assembly of colloidal nanocrystals (NCs) into superstructures with long-range translational and orientational order is sensitive to the molecular interactions between ligands bound to the NC surface. We illustrate how ligand coverage on colloidal PbS NCs can be exploited as a tunable parameter to direct the self-assembly of superlattices with predefined symmetry. We show that PbS NCs with dense ligand coverage assemble into face-centered cubic (fcc) superlattices whereas NCs with sparse ligand coverage assemble into body-centered cubic (bcc) superlattices which also exhibit orientational ordering of NCs in their lattice sites. Surface chemistry characterization combined with density functional theory calculations suggest that the loss of ligands occurs preferentially on {100} than on reconstructed {111} NC facets. The resulting anisotropic ligand distribution amplifies the role of NC shape in the assembly and leads to the formation of superlattices with translational and orientational order.
authors.affiliation: School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Choi
authors.forename: Clive R
authors.initials: CR
authors.lastname: Bealing
authors.forename: Kaifu
authors.initials: K
authors.lastname: Bian
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Hughes
authors.forename: Wenyu
authors.initials: W
authors.lastname: Zhang
authors.forename: Detlef-M
authors.initials: DM
authors.lastname: Smilgies
authors.forename: Richard G
authors.initials: RG
authors.lastname: Hennig
authors.forename: James R
authors.initials: JR
authors.lastname: Engstrom
authors.forename: Tobias
authors.initials: T
authors.lastname: Hanrath
mesh_terms: D016880:Anisotropy; D003102:Colloids / Q000737:chemistry; D007854:Lead / Q000737:chemistry*; D008024:Ligands; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D013440:Sulfides / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D003102:Colloids; D008024:Ligands; D013440:Sulfides; C018391:lead sulfide; D007854:Lead