The Role of Ligand Packing Frustration in Body-Centered Cubic (bcc) Superlattices of Colloidal Nanocrystals.
This paper addresses the assembly of body centered-cubic (bcc) superlattices of organic ligand-coated nanocrystals. First, examples of bcc superlattices of dodecanethiol-capped Au nanocrystals and oleic acid-capped PbS and PbSe nanocrystals are presented and examined by transmission electron microscopy (TEM) and grazing incidence small-angle X-ray scattering (GISAXS). These superlattices tend to orient on their densest (110) superlattice planes and exhibit a significant amount of {112} twinning. The same nanocrystals deposit as monolayers with hexagonal packing, and these thin films can coexist with thicker bcc superlattice layers, even though there is no hexagonal plane in a bcc lattice. Both the preference of bcc in bulk films over the denser face-centered cubic (fcc) superlattice structure and the transition to hexagonal monolayers can be rationalized in terms of packing frustration of the ligands. A model is presented to calculate the difference in entropy associated with capping ligand packing frustration in bcc and fcc superlattices.
†McKetta Department of Chemical Engineering, Texas Materials Institute, Center for Nano and Molecular Science and Technology, The University of Texas at Austin, Austin, Texas 78712-1062, United States.
Brian W
BW
Goodfellow
†McKetta Department of Chemical Engineering, Texas Materials Institute, Center for Nano and Molecular Science and Technology, The University of Texas at Austin, Austin, Texas 78712-1062, United States.
Yixuan
Y
Yu
†McKetta Department of Chemical Engineering, Texas Materials Institute, Center for Nano and Molecular Science and Technology, The University of Texas at Austin, Austin, Texas 78712-1062, United States.
Christian A
CA
Bosoy
‡Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, New York 14853, United States.
Detlef-M
DM
Smilgies
†McKetta Department of Chemical Engineering, Texas Materials Institute, Center for Nano and Molecular Science and Technology, The University of Texas at Austin, Austin, Texas 78712-1062, United States.
Brian A
BA
Korgel
body-centered cubic; ligand-coated nanocrystals; nanocrystal self-assembly; nanoparticles; small angle X-ray scattering; superlattices; twinning