An Obtuse Rhombohedral Superlattice Assembled by Pt
Nanocubes
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Abstract
We
grew large single three-dimensional supercrystals from colloidal
Pt nanocubes (NCs) suspended in hexane. A synchrotron-based two circle
diffractometer was used to obtain an unprecedented level of detail
from full sets of small/wide-angle X-ray scattering (SAXS/WAXS) patterns.
Automatic indexing and simulations of X-ray patterns enabled detailed
reconstruction of NC translation and shape orientation within the
supercrystals from atomic to mesometric levels. The supercrystal has
an obtuse rhombohedral (Rh) superlattice with space group <i>R</i>3<i>m</i> and a trigonal cell angle of 106.2°.
Individual NCs orient themselves in a manner of atomic Pt[111] parallel
to superlattice Rh[111]. We analyzed the superlattice structure in
context of three spatial relationships of proximate NCs including
face-to-face, edge-to-edge, and corner-to-corner configurations. Detailed
analysis of supercrystal structure reveals nearly direct corner-to-corner
contacts and a tight interlocking NC structure. We employed the correlations
between strain and lattice distortion and established the first structural
correlating mechanism between
five superlattice polymorphs to elucidate the superlattice transformations
and associated developing pathways. Together, the experimental and
modeling results provide comprehensive structural information toward
controlling design and efficient materials-processing for large fabrication
of nanobased functional materials with tailored structures and desired
properties