Block Copolymer Directed One-Pot Simple Synthesis of L10-Phase FePt Nanoparticles inside Ordered Mesoporous Aluminosilicate/Carbon Composites

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• 作者：Eunae Kang ; Hyunok Jung ; Je-Geun Park ; Seungchul Kwon ; Jongmin Shim ; Hiroaki Sai ; Ulich Wiesner ; Jin Kon Kim ; Jinwoo Lee
• 刊名：ACS Nano
• 出版年：2011
• 出版时间：February 22, 2011
• 年：2011
• 卷：5
• 期：2
• 页码：1018-1025
• 全文大小：946K
• 年卷期：0
• ISSN：1936-086X

文摘

A “one-pot” synthetic method was developed to produce L1₀-phase FePt nanoparticles in ordered mesostructured aluminosilicate/carbon composites using polyisoprene-block-poly(ethylene oxide) (PI-b-PEO) as a structure-directing agent. PI-b-PEO block copolymers with aluminosilicate sols are self-assembled with a hydrophobic iron precursor (dimethylaminomethyl-ferrocene) and a hydrophobic platinum precursor (dimethyl(1,5-cyclooctadiene)platinum(II)) to obtain mesostructured composites. The as-synthesized material was heat-treated to 800 °C under an Ar/H₂ mixture (5% v/v), resulting in the formation of fct FePt nanocrystals encapsulated in ordered mesopores. By changing the quantities of the Fe and Pt precursors in the composite materials, the average particle size of the resulting fct FePt, estimated using the Debye−Scherer equation with X-ray diffraction patterns, can be easily controlled to be 2.6−10.4 nm. Using this simple synthetic method, we can extend the size of directly synthesized fct FePt up to ∼10 nm, which cannot be achieved directly in the colloidal synthetic method. All fct FePt nanoparticles show hysteresis behavior at room temperature, which indicates that ferromagnetic particles are obtained inside mesostructued channels. Well-isolated, ∼10 nm fct FePt have a coercivity of 1100 Oe at 300 K. This coercivity value is higher than values of fct FePt nanoparticles synthesized through the tedious hard template method by employing SBA-15 as a host material. The coercivity value for FePt-1 (2.6 nm) at 5 K is as high as 11 900 Oe, which is one of the largest values reported for FePt nanoparticles, or any other magnetic nanoparticles. The fct FePt nanoparticles also showed exchange-bias behavior.