1. Reversible Kirkwood-Alder transition observed in Pt3Cu2 nanoctahedron assemblies under controlled solvent annealing/drying conditions.
- Author
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Zhang J, Luo Z, Martens B, Quan Z, Kumbhar A, Porter N, Wang Y, Smilgies DM, and Fang J
- Subjects
- Crystallization, Nanostructures ultrastructure, Scattering, Small Angle, Solvents chemistry, X-Ray Diffraction, Amines chemistry, Copper chemistry, Nanostructures chemistry, Oleic Acid chemistry, Platinum Compounds chemistry
- Abstract
We report a Kirkwood-Alder transition in a system of nonspherical Pt(3)Cu(2) nanoctahedra coated with oleic acid and oleylamine ligands. Using both transmission electron microscopy tomography with 3D reconstruction analysis and synchrotron-based in-situ grazing-incidence small-angle X-ray scattering (GISAXS) techniques, we specifically determined that these nanoctahedra can assemble into an open structure in which the nanoctahedra are arranged tip-to-tip to form a bcc superlattice with a low packing efficiency. Using in-situ and real-time GISAXS, we further observed a "nanoctahedron crystallization" as a soft Kirkwood-Alder transition, that is, the soft nanoactahedra crystallize at a critical concentration and possess continuous crystalline states during a period of solvent evaporation. Finally, we found a reversible change of the superlattice constant during the solvent annealing and evaporation/drying processes.
- Published
- 2012
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