Monodisperse magnetic single-crystal ferrite microspheres
Monodisperse magnetic single-crystal ferrite microspheres
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DOI：
10.1002/anie.200462551
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发表时间：
2005-01-01
影响因子：
16.6
通讯作者：
Li, YD
中科院分区：
文献类型：
--
作者：
Deng, H;Li, XL;Li, YD
人们一直认为，许多新的性能和潜在的应用将出现从单分散材料与小尺寸。因此，单分散纳米颗粒的合成由于其技术和基础科学重要性而被广泛追求。[1-7]纳米结构磁性材料的合成已经成为一个特别重要的研究领域，并且由于这种材料在铁磁流体、先进磁性材料、催化剂、有色颜料、高密度磁记录介质和医学诊断中的潜在应用而引起越来越大的兴趣。[8-13]尖晶石型铁氧体（MFe 2 O 4; M= Fe、Mn、Zn或Co）是最重要的磁性材料之一，广泛应用于电子设备、信息存储、磁共振成像（MRI）和药物输送技术。[8，9，14]磁铁矿（Fe 3 O 4）最近被认为是生物应用的理想候选物，既可以作为传感和成像的标签，也可以作为抗肿瘤治疗的活性剂。[15-17]为了在功能特定的生物应用中获得高性能，磁性颗粒必须是球形的，并且具有光滑的表面，窄的尺寸分布，大的表面积（用于最大的蛋白质或酶结合），高磁饱和度（σs）以提供最大的信号，以及在液体介质中的良好分散。[6，18，19]在Sugimoto和Matijevic在20世纪80年代早期报道了具有窄尺寸分布的磁铁矿颗粒的制备之后，[20]单分散铁氧体已经通过各种基于化学的合成方法制备，包括共沉淀，反胶束法，微波等离子体合成，溶胶凝胶技术，冷冻干燥，超声辐照，水热法，激光热解技术，以及有机金属和配位化合物的热分解。[1，9，14，18，20-27]然而，这些方法中的大多数集中于限于直径小于30 nm的铁氧体颗粒的合成。目前还没有关于合成结晶良好、大小与蛋白质分子相似的铁氧体纳米颗粒的报道。开发一种简便、经济的合成亲水性、生物相容性磁铁矿纳米颗粒的方法将有利于其在生物医学领域的技术应用，特别是在体内的应用。本文报道了一种通过溶剂热还原法制备单分散、亲水性、单晶铁氧体微球的一般方法。据我们所知，这是第一个单晶磁性微球的合成报告。铁氧体球具有在200-800 nm范围内可调的单分散直径。这项工作为获得各种单分散、磁性和单晶微球提供了一种重要方法，并为进一步应用这些有前途的材料提供了机会。在溶剂热体系中，通过改进的FeCl 3和乙二醇之间的还原反应，进行了典型的Fe 3 O 4和铁氧体微球的合成。我们通过控制氧化反应确认了Fe 3 O 4的生成，在氧化反应中生成了α-和g-Fe 2 O3（支持信息）。[1b通过XRD表征MFe 2 O 4的晶体结构。如图1所示，图案可以很容易地索引为Fe 3 O 4（JCPDS 75-1609）、MnFe 2 O 4（JCPDS 74-2403）、ZnFe 2 O 4（JCPDS 22-1012）和CoFe 2 O 4（JCPDS 22-1068）。采用X射线光电子能谱仪（支持信息）对样品进行了分析，并通过透射电镜（TEM）和扫描电子显微镜（SEM）对产物的尺寸和形貌进行了表征。
It has been thought that many novel properties and potential applications would emerge from monodisperse materials with small dimensions. Therefore, the synthesis of monodisperse nanoparticles has been intensively pursued for their technological and fundamental scientific importance.[1–7] The synthesis of nanostructured magnetic materials has become a particularly important area of research and is attracting a growing interest because of the potential applications such materials have in ferrofluids, advanced magnetic materials, catalysts, colored pigments, high-density magnetic recording media, and medical diagnostics.[8–13] Spinel ferrites (MFe2O4; M= Fe, Mn, Zn, or Co) are among the most important magnetic materials and have been widely used in electronic devices, information storage, magnetic resonance imaging (MRI), and drug-delivery technology.[8, 9, 14] Magnetite (Fe3O4) has recently been considered an ideal candidate for biological applications, both as a tag for sensing and imaging, and as an activity agent for antitumor therapy.[15–17] For high performance in function-specific biological applications, magnetic particles must be spherical and have smooth surfaces, narrow size distributions, large surface areas (for maximal protein or enzyme binding), high magnetic saturation (σs) to provide maximum signal, and good dispersion in liquid media.[6, 18, 19] After Sugimoto and Matijevic reported the preparation of magnetite particles with a narrow size distribution in the early 1980s,[20] monodisperse ferrite has been fabricated by various chemistry-based synthetic methods, including coprecipitation, the reverse micelle method, microwave plasma synthesis, solgel techniques, freeze drying, ultrasound irradiation, hydrothermal methods, laser pyrolysis techniques, and thermal decomposition of organometallic and coordination compounds.[1, 9, 14, 18, 20–27] However, most of these approaches were focused on the synthesis of ferrite particles limited to diameters below 30 nm. There are no reports on the synthesis of well-crystallized ferrite nanoparticles with sizes similar to protein molecules. The development of a facile and economic synthetic strategy for the synthesis of hydrophilic, biocompatible magnetite nanoparticles would benefit their technical use in biomedical fields, especially for applications in vivo. Herein we report a general approach for the fabrication of monodisperse, hydrophilic, and single-crystalline ferrite microspheres by a solvothermal reduction method. To the best of our knowledge, this is the first report on the synthesis of single-crystalline magnetic microspheres. The ferrite spheres had monodisperse diameters that were tunable in the range of 200–800 nm. This work resulted in an important method for obtaining various monodisperse, magnetic, and single-crystalline microspheres, and provided an opportunity to further apply these promising materials. Typical syntheses of Fe3O4 and ferrite microspheres were carried out in a solvothermal system by modified reduction reactions between FeCl3 and ethylene glycol. We confirmed the production of Fe3O4 by conducting controlled oxidation reactions in which a-and g-Fe2O3 were produced (Supporting Information).[1b, 28–29] The crystalline structures of MFe2O4 were characterized by XRD. As shown in Figure1, the patterns can be easily indexed to Fe3O4 (JCPDS 75-1609), MnFe2O4 (JCPDS 74-2403), ZnFe2O4 (JCPDS 22-1012), and CoFe2O4 (JCPDS 22-1068). The Fe3O4 sample was determined by X-ray photoelectron spectroscopy (Supporting Information).The size and shape of the products were examined by TEM and scanning electron microscopy (SEM …