Shape-Anisotropy Driven Symmetry Transformations in Nanocrystal Superlattice Polymorphs
Choi, Joshua J.
KAUST Grant NumberKUS-C1-018-02
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AbstractDespite intense research efforts by research groups worldwide, the potential of self-assembled nanocrystal superlattices (NCSLs) has not been realized due to an incomplete understanding of the fundamental molecular interactions governing the self-assembly process. Because NCSLs reside naturally at length-scales between atomic crystals and colloidal assemblies, synthetic control over the properties of constituent nanocrystal (NC) building blocks and their coupling in ordered assemblies is expected to yield a new class of materials with remarkable optical, electronic, and vibrational characteristics. Progress toward the formation of suitable test structures and subsequent development of NCSL-based technologies has been held back by the limited control over superlattice spacing and symmetry. Here we show that NCSL symmetry can be controlled by manipulating molecular interactions between ligands bound to the NC surface and the surrounding solvent. Specifically, we demonstrate solvent vapor-mediated NCSL symmetry transformations that are driven by the orientational ordering of NCs within the lattice. The assembly of various superlattice polymorphs, including face-centered cubic (fcc), body-centered cubic (bcc), and body-centered tetragonal (bct) structures, is studied in real time using in situ grazing incidence small-angle X-ray scattering (GISAXS) under controlled solvent vapor exposure. This approach provides quantitative insights into the molecular level physics that controls solvent-ligand interactions and assembly of NCSLs. Computer simulations based on all-atom molecular dynamics techniques confirm several key insights gained from experiment. © 2011 American Chemical Society.
CitationBian K, Choi JJ, Kaushik A, Clancy P, Smilgies D-M, et al. (2011) Shape-Anisotropy Driven Symmetry Transformations in Nanocrystal Superlattice Polymorphs. ACS Nano 5: 2815–2823. Available: http://dx.doi.org/10.1021/nn103303q.
SponsorsWe thank Lynden Archer, Ital Cohen, Sol Gruner, Richard Hennig, Don Koch, and Jim Sethna for stimulating discussions. We thank Brandon Aldinger and Melissa Hines for assistance with the infrared spectroscopy measurements. K.B. was supported by NSF-CBET 0828703. J.J.C. was supported by the NSF IGERT Fellowship Program on "Nanoscale Control of Surfaces and Interfaces," administered by Cornell's MRSEC. A.K. was supported by the KAUST-CU Center for Energy and Sustainability. GISAXS measurements were conducted at the Cornell High Energy Synchrotron Source (CHESS), which is supported by the National Science Foundation and the National Institutes of Health/National Institute of General Medical Sciences under NSF award DMR-0225180. This work was supported in part by Award No. KUS-C1-018-02, made by King Abdullah University of Science and Technology (KAUST).
PublisherAmerican Chemical Society (ACS)
CollectionsPublications Acknowledging KAUST Support
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