Singular behaviour of atomic ordering in Pt-Co nanocubes starting from core-shell configurations

Kohei Aso; Hirokazu Kobayashi; Shotaro Yoshimaru; Xuan Quy Tran; Miho Yamauchi; Syo Matsumura; Yoshifumi Oshima

doi:10.1039/d2nr01982e

Singular behaviour of atomic ordering in Pt-Co nanocubes starting from core-shell configurations

Kohei Aso, Hirokazu Kobayashi, Shotaro Yoshimaru, Xuan Quy Tran, Miho Yamauchi, Syo Matsumura, Yoshifumi Oshima

Research output: Contribution to journal › Article › peer-review

2 Citations (Scopus)

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.

Original language	English
Pages (from-to)	9842-9848
Number of pages	7
Journal	Nanoscale
Volume	14
Issue number	27
DOIs	https://doi.org/10.1039/d2nr01982e
Publication status	Published - Jun 3 2022

All Science Journal Classification (ASJC) codes

Materials Science(all)

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10.1039/d2nr01982e

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@article{a1120cfe500c476cb76189e31dfcc096,

title = "Singular behaviour of atomic ordering in Pt-Co nanocubes starting from core-shell configurations",

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.",

author = "Kohei Aso and Hirokazu Kobayashi and Shotaro Yoshimaru and Tran, {Xuan Quy} and Miho Yamauchi and Syo Matsumura and Yoshifumi Oshima",

note = "Funding Information: The authors are indebted to Dr Masaru Kato at STEM Co., Ltd, Japan for his contribution to the experimental setups. The authors are grateful to Mr Koichi Higashimine at the Center for Nano Materials and Technology in Japan Advanced Institute of Science and Technology for technical support. The authors also appreciate Dr Masaki Kudo and Mr Takaaki Toriyama at the Ultramicroscopy Research Center at Kyushu University for technical support. Publisher Copyright: {\textcopyright} 2022 The Royal Society of Chemistry.",

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doi = "10.1039/d2nr01982e",

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T1 - Singular behaviour of atomic ordering in Pt-Co nanocubes starting from core-shell configurations

AU - Aso, Kohei

AU - Kobayashi, Hirokazu

AU - Yoshimaru, Shotaro

AU - Tran, Xuan Quy

AU - Yamauchi, Miho

AU - Matsumura, Syo

AU - Oshima, Yoshifumi

N1 - Funding Information: The authors are indebted to Dr Masaru Kato at STEM Co., Ltd, Japan for his contribution to the experimental setups. The authors are grateful to Mr Koichi Higashimine at the Center for Nano Materials and Technology in Japan Advanced Institute of Science and Technology for technical support. The authors also appreciate Dr Masaki Kudo and Mr Takaaki Toriyama at the Ultramicroscopy Research Center at Kyushu University for technical support. Publisher Copyright: © 2022 The Royal Society of Chemistry.

PY - 2022/6/3

Y1 - 2022/6/3

N2 - 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.

AB - 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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JO - Nanoscale

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Singular behaviour of atomic ordering in Pt-Co nanocubes starting from core-shell configurations

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