Synthesis and characterization of magnetic Co nanoparticles: A comparison study of three different capping surfactants

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• 作者：Yu Lu ; Xianmao Lu ; Brian T. Mayers ; Thurston Herricks ; Younan Xia
• 关键词：Cobalt nanoparticle ; Capping agent ; Olefinic acid ; Aliphatic acid ; Isomeric transformation
• 刊名：Journal of Solid State Chemistry
• 出版年：2008
• 出版时间：July 2008
• 年：2008
• 卷：181
• 期：7
• 页码：1530-1538
• 全文大小：1461 K

文摘

This paper compares the performance of three long-chain acids—oleic and elaidic (both olefinic) and stearic (aliphatic)—as a capping agent in the synthesis of magnetic Co nanoparticles. The particles were formed through thermal decomposition of dicobalt octacarbonyl in toluene in the presence of the long-chain acid, and characterized by TEM, high-resolution TEM, and SQUID measurements. Infrared spectra revealed that some of the added olefinic acid was transformed from cis- to trans-configuration (for oleic acid) or from trans- to cis- (for elaidic acid) to facilitate the formation of a densely packed monolayer on the surface of Co nanoparticles. As compared to aliphatic acids, olefinic acids are advantageous for dense packing on small particles with high surface curvatures due to a bent shape of the cis-isomer. The presence of an olefinic acid is able to control particle growth, stabilize the colloidal suspension, and prevent the final product from oxidation by air. Our results indicate that oleic acid, elaidic acid, and a mixture of oleic/stearic acids or elaidic/stearic acids have roughly the same performance in serving as a capping agent for the synthesis of Co nanoparticles with a spherical shape and narrow size distribution.