Large-Scale Synthesis of Single-Crystalline Iron Oxide Magnetic Nanorings
Large-Scale Synthesis of Single-Crystalline Iron Oxide Magnetic Nanorings
复制标题
单晶氧化铁磁性纳米环的大规模合成
DOI：
10.1021/ja805152t
复制
发表时间：
2008-12-17
影响因子：
15
通讯作者：
Raabe, Joerg
中科院分区：
文献类型：
--
作者：
Jia, Chun-Jiang;Sun, Ling-Dong;Raabe, Joerg
我们提出了一种创新的方法来生产单晶氧化铁纳米环采用基于溶液的路线。采用双阴离子辅助水热法（包括磷酸根和硫酸根离子）合成了单晶赤铁矿（α-Fe 2 O3）纳米环，该方法可分为两个阶段：（1）形成胶囊状的α-Fe 2 O3纳米颗粒;（2）沿纳米颗粒的长尺寸（α-Fe 2 O3的c轴）沿着优先溶解形成纳米环。纳米环的形状主要是由磷酸根离子在α-Fe 2 O3的平行于c轴的表面上的吸附来调节的，而中空结构是由于硫酸根离子的强配位作用使α-Fe 2 O3沿c轴沿着方向优先溶解而形成的。通过改变磷酸盐和硫酸盐离子与铁离子的比例，我们能够控制尺寸，形态和表面结构，以产生各种三维中空纳米结构。然后通过还原或还原-氧化过程将其转化为磁铁矿（Fe 3 O 4）和磁赤铁矿（γ-Fe 2 O3），同时保持相同的形态。这些单晶α-Fe_2O_3，Fe_3O_4和γ-Fe_2O_3纳米环的结构和磁性的特点是通过各种分析技术。采用离轴电子全息技术，我们观察到了经典的单涡旋磁性状态在薄的磁铁矿纳米环，而较厚的环显示出有趣的三维磁性配置。这项工作提供了一种容易放大的方法来制备定制的氧化铁纳米环，可以满足从医学到磁电子学等各种应用的需求。
We present an innovative approach to the production of single-crystal iron oxide nanorings employing a solution-based route. Single-crystal hematite (alpha-Fe2O3) nanorings were synthesized using a double anion-assisted hydrothermal method (involving phosphate and sulfate ions), which can be divided into two stages: (1) formation of capsule-shaped alpha-Fe2O3 nanoparticles and (2) preferential dissolution along the long dimension of the elongated nanoparticles (the c axis of alpha-Fe2O3) to form nanorings. The shape of the nanorings is mainly regulated by the adsorption of phosphate ions on faces parallel to c axis of alpha-Fe2O3 during the nanocrystal growth, and the hollow structure is given by the preferential dissolution of the alpha-Fe2O3 along the c axis due to the strong coordination of the sulfate ions. By varying the ratios of phosphate and sulfate ions to ferric ions, we were able to control the size, morphology, and surface architecture to produce a variety of three-dimensional hollow nanostructures. These can then be converted to magnetite (Fe3O4) and maghemite (gamma-Fe2O3) by a reduction or reduction-oxidation process while preserving the same morphology. The structures and magnetic properties of these single-crystal alpha-Fe2O3, Fe3O4, and gamma-Fe2O3 nanorings were characterized by various analytical techniques. Employing off-axis electron holography, we observed the classical single-vortex magnetic state in the thin magnetite nanorings, while the thicker rings displayed an intriguing three-dimensional magnetic configuration. This work provides an easily scaled-up method for preparing tailor-made iron oxide nanorings that could meet the demands of a variety of applications ranging from medicine to magnetoelectronics.