Hefei National Laboratory for Physical Sciences at Microscale and Department of Materials Science & Engineering, University of Science and Technology of China, Hefei, 230026, China.
Dalton Trans. 2011 Sep 14;40(34):8622-9. doi: 10.1039/c1dt10733j. Epub 2011 Jul 29.
Stable bracelet-like magnetic nanorings, formed by Ag-Fe(3)O(4) nanoparticles with an average size around 40 nm, have been successfully prepared in large scale by means of reducing Ag(+) and Fe(3+) simultaneously under mild conditions. In the reaction, tiny grains of silver are used as seeds to prompt small Fe(3)O(4) nanoparticles to grow larger, which is essential to enhance the magnetic dipole-dipole interactions, while only superparamagnetic Fe(3)O(4) nanoparticles (about 10 nm in size) can be obtained in the absence of Ag seeds. The XRD, TEM, SAED and the EDS line scan data reveal that these nanoparticles are in the core-shell structure. These magnetic Ag-Fe(3)O(4) nanoparticles assembled into nanorings by magnetic dipole-dipole interactions with a diameter of 100-200 nm. The saturation magnetization of the nanorings is 39.5 emu g(-1) at room temperature. The MRI images indicate that these kind of nanorings have the potential application in diagnostics as a T(2) MRI contrast agent.
稳定的手链状磁性纳米环，由平均尺寸约为 40nm 的 Ag-Fe(3)O(4)纳米粒子组成，已经通过在温和条件下同时还原 Ag(+)和 Fe(3+)成功地大规模制备。在反应中，微小的银晶粒被用作种子来促使较小的 Fe(3)O(4)纳米粒子生长得更大，这对于增强磁偶极子相互作用是至关重要的，而在没有 Ag 种子的情况下，只能得到超顺磁 Fe(3)O(4)纳米粒子（约 10nm 大小）。XRD、TEM、SAED 和 EDS 线扫描数据表明这些纳米粒子具有核壳结构。这些磁性 Ag-Fe(3)O(4)纳米粒子通过磁偶极子相互作用自组装成直径为 100-200nm 的纳米环。纳米环在室温下的饱和磁化强度为 39.5emu/g。MRI 图像表明，这些纳米环有可能作为 T(2)MRI 造影剂应用于诊断。
