Reversible Kirkwood鈥揂lder Transition Observed in Pt3Cu2 Nanoctahedron Assemblies under Controlled Solvent Annealing/Drying Conditions

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• 作者：Jun Zhang ; Zhiping Luo ; Benjamin Martens ; Zewei Quan ; Amar Kumbhar ; Nathan Porter ; Yuxuan Wang ; Detlef-M. Smilgies ; Jiye Fang
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：August 29, 2012
• 年：2012
• 卷：134
• 期：34
• 页码：14043-14049
• 全文大小：482K
• 年卷期：v.134,no.34(August 29, 2012)
• ISSN：1520-5126

文摘

We report a Kirkwood鈥揂lder transition in a system of nonspherical Pt₃Cu₂ 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 鈥渘anoctahedron crystallization鈥?as a soft Kirkwood鈥揂lder 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.