Singular behaviour of atomic ordering in Pt-Co nanocubes starting from core-shell configurations
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Updated: Sep 6, 2025

Facile Preparation of Internally Self-assembled Lipid Particles Stabilized by Carbon Nanotubes
Published on: February 19, 2016
Kohei Aso1, Hirokazu Kobayashi2, Shotaro Yoshimaru3
1School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan. aso@jaist.ac.jp.
Abstract:
The ordered structure of platinum-cobalt (Pt-Co) alloy nanoparticles has been studied actively because the structure influences their magnetic and catalytic properties. On the Pt-Co alloy's surface, Pt atoms preferentially segregate during annealing to reduce the surface energy. Such surface segregation has been shown to promote the formation of an ordered structure near the surface of Pt-Co thin films. Although this phenomenon seems also useful to control the nanoparticle structure, this has not been observed. Here, we have studied the ordered structure in annealed Pt@Co core-shell nanoparticles using a scanning transmission electron microscope. The nanoparticles were chemically synthesized, and their structural changes after annealing at 600 °C, 700 °C, and 800 °C for 3 h were observed. After being annealed at 600 °C and 800 °C, the particles contained the L12-Pt3Co ordered structure. The structure seems reasonable considering an initial Pt : Co ratio of ∼4 : 1. However, we found that the L10-PtCo structure was formed near the nanoparticle surface after annealing at 700 °C. The L10-PtCo structure was thought to be formed from the surface segregation of Pt atoms and insufficient diffusion of Pt and Co atoms to mix them in the particle overall.
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