Che Shenglei

Tuning crystal structure and magnetic property of dispersible FePt intermetallic nanoparticles

Dispersible FePt intermetallic nanoparticles (NPs) with tunable composition were synthesized by thermal annealing of MgO coated Al-FePt (or Al-FePt-Fe3O4) NPs followed by an acid treatment to remove MgO. High-temperature annealing facilitates the conversion of FePt from disordered alloy to ordered intermetallics. Under the protection of MgO, the diffusion of Fe and Pt atoms was limited, making it possible for the atom reconstruction in the lattice to give discrete FePt intermetallic NPs after a facile acid etching process. FePt intermetallic NPs formed face-centered cubic and face-centered tetragonal structures with their magnetic properties tuned by composition. The saturation magnetization was adjusted from 8 to 52 emu g−1 by increasing the Fe concentration, while the coercivity reached a maximum of 33 kOe when Fe concentration was 44%. After surface modifications by hydrophilic or hydrophobic molecules containing thiol groups, FePt intermetallic NPs could be dissolved into water or hydrocarbon solvents. The hydrophilic L10-FePt intermetallic NPs were applied as contrast agents for magnetic resonance imaging, showing a high transverse relaxivity of 328.6 mmol−1 L s−1, which indicated the great potential of FePt intermetallic NPs as molecular probes for cancer diagnosis.摘要具有可调组分的单分散FePt金属间化合物纳米颗粒由MgO包覆的Al-FePt(或者Al-FePt-Fe3O4)经过热退火, 再通过酸处理除去MgO制备得到. 高温退火有助于FePt从无序合金转变为有序金属间化合物. 在MgO的保护下, Fe和Pt的扩散受到限制, 因而晶格中的Fe、 Pt原子能够重构形成FePt金属间化合物, 再通过简单的酸腐蚀可得到分散的纳米颗粒. FePt金属间化合物纳米颗粒形成面心立方和面心四方结构, 通过组分调节可以改变其磁性能. 随着铁含量的增加, 其饱和磁化强度从8 emu g−1提高到52 emu g−1, 在铁含量为44%时, 矫顽力达到最大值33 kOe. 利用含巯基分子对纳米颗粒表面进行亲水或疏水性改性, FePt金属间化合物纳米颗粒可以溶于水和烃类溶剂. 亲水的L10-FePt金属间化合物纳米颗粒可作为磁共振成像造影剂, 表现出高的横向弛豫率(328.6 mmol−1 L s−1), 这表明FePt金属间化合物纳米颗粒有望用于肿瘤诊断的分子探针.