title: Shape alloys of nanorods and nanospheres from self-assembly.
abstract: Mixtures of anisotropic nanocrystals promise a great diversity of superlattices and phase behaviors beyond those of single-component systems. However, obtaining a colloidal shape alloy in which two different shapes are thermodynamically coassembled into a crystalline superlattice has remained a challenge. Here we present a joint experimental-computational investigation of two geometrically ubiquitous nanocrystalline building blocks-nanorods and nanospheres-that overcome their natural entropic tendency toward macroscopic phase separation and coassemble into three intriguing phases over centimeter scales, including an AB2-type binary superlattice. Monte Carlo simulations reveal that, although this shape alloy is entropically stable at high packing fraction, demixing is favored at experimental densities. Simulations with short-ranged attractive interactions demonstrate that the alloy is stabilized by interactions induced by ligand stabilizers and/or depletion effects. An asymmetry in the relative interaction strength between rods and spheres improves the robustness of the self-assembly process.
authors.affiliation: Department of Chemistry and ‡Department of Materials Science and Engineering, University of Pennsylvania , Philadelphia, Pennsylvania 19104, United States.
authors.forename: Xingchen
authors.initials: X
authors.lastname: Ye
authors.forename: Jaime A
authors.initials: JA
authors.lastname: Millan
authors.forename: Michael
authors.initials: M
authors.lastname: Engel
authors.forename: Jun
authors.initials: J
authors.lastname: Chen
authors.forename: Benjamin T
authors.initials: BT
authors.lastname: Diroll
authors.forename: Sharon C
authors.initials: SC
authors.lastname: Glotzer
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Murray
mesh_terms: D000497:Alloys / Q000737:chemistry*; D016880:Anisotropy; D008024:Ligands; D053758:Nanoparticles / Q000737:chemistry; D054118:Nanospheres / Q000737:chemistry*; D043942:Nanotubes / Q000737:chemistry*
chemical_list: D000497:Alloys; D008024:Ligands