Silica coating of Co–Pt alloy nanoparticles prepared in the presence of poly(vinylpyrrolidone)

  • Yoshio Kobayashi
  • Hidekazu Kakinuma
  • Daisuke Nagao
  • Yasuo Ando
  • Terunobu Miyazaki
  • Mikio Konno
Research Paper

Abstract

This article describes a method for silica coating of Co–Pt alloy nanoparticles prepared in the presence of poly(vinylpyrrolidone) (PVP) as a stabilizer. The Co–Pt nanoparticles were prepared in an aqueous solution at 25–80 °C from CoCl2 (3.0 × 10−4 M), H2PtCl6 (3.0 × 10−4 M), PVP (0–10 g/L), and NaBH4 (4.8 × 10−3–2.4 × 10−2 M). The silica coating was performed for the Co–Pt nanoparticle colloid containing the PVP ([Co] = [Pt] = 3.0 × 10−5 M) at 25 °C in (1/4) (v/v) water/ethanol solution with tetraethoxyorthosilicate (TEOS) (7.2 × 10−5–7.2 × 10−3 M) and ammonia (0.1–1.0 M). Silica particles, which had an average size of 43 nm and contained multiple cores of Co–Pt nanoparticles with a size of ca. 8 nm, were produced at 1.4 × 10−3 M TEOS and 0.5 M ammonia after the preparation of Co–Pt nanoparticles at 80 °C, 5 g/L PVP, and 2.4 × 10−2 M NaBH4. Their core particles were fcc Co–Pt alloy crystallites. Their saturation magnetization was 2.0-emu/g sample, and their coercive field was 12 Oe.

Keywords

Particle Alloy Co–Pt Poly(vinylpyrrolidone) Silica Core-shell Sol–gel Magnetic media Storage 

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Copyright information

© Springer Science+Business Media B.V. 2009

Authors and Affiliations

  • Yoshio Kobayashi
    • 1
    • 3
  • Hidekazu Kakinuma
    • 1
  • Daisuke Nagao
    • 1
  • Yasuo Ando
    • 2
  • Terunobu Miyazaki
    • 2
  • Mikio Konno
    • 1
  1. 1.Department of Chemical Engineering, Graduate School of EngineeringTohoku UniversitySendaiJapan
  2. 2.Department of Applied Physics, Graduate School of EngineeringTohoku UniversitySendaiJapan
  3. 3.Department of Biomolecular Functional Engineering, College of EngineeringIbaraki UniversityHitachiJapan

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