Zhang Hai-Tao, Chen Xian-Hui
Hefei National Laboratory for Physical Sciences at the Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
Nanotechnology. 2005 Oct;16(10):2288-94. doi: 10.1088/0957-4484/16/10/051. Epub 2005 Aug 26.
Monodisperse cobalt monoxide (CoO) nanocrystals ranging in size from 4.5 to 23 nm were prepared via the thermal decomposition of cobalt acetylacetonate (Co(acac)(2)) in oleylamine under vigorous stirring. The size control of the nanocrystals was achieved by tailoring the reaction temperature or by seed-mediated growth. The nanocrystals have been characterized by x-ray diffraction, transmission electron microscopy, and Fourier transform infrared and x-ray photoelectron spectroscopy. The as-prepared nanocrystals are stable because of the organic coating (oleylamine) that occurred in situ. Magnetic measurement reveals that all of the nanocrystals are superparamagnetic at high temperatures and show ferromagnetic interactions at low temperatures due to the existence of uncompensated moments on the surface of the nanoparticles. The weak ferromagnetic interactions increase with decreasing particle size.
通过在剧烈搅拌下乙酰丙酮钴（Co(acac)₂）在油胺中的热分解制备了尺寸范围为4.5至23纳米的单分散一氧化钴（CoO）纳米晶体。通过调整反应温度或种子介导生长实现了纳米晶体的尺寸控制。通过X射线衍射、透射电子显微镜、傅里叶变换红外光谱和X射线光电子能谱对纳米晶体进行了表征。由于原位形成的有机涂层（油胺），所制备的纳米晶体是稳定的。磁性测量表明，所有纳米晶体在高温下都是超顺磁性的，并且由于纳米颗粒表面存在未补偿的磁矩，在低温下表现出铁磁相互作用。弱铁磁相互作用随着粒径的减小而增加。
