Evolution of Structural and Magnetic Properties of Magnetite Nanoparticles for Biomedical Applications

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• 作者：Stefan Gustafsson ; Andrea Fornara ; Karolina Petersson ; Christer Johansson ; Mamoun Muhammed ; Eva Olsson
• 刊名：Crystal Growth & Design
• 出版年：2010
• 出版时间：May 5, 2010
• 年：2010
• 卷：10
• 期：5
• 页码：2278-2284
• 全文大小：929K
• 年卷期：v.10,no.5(May 5, 2010)
• ISSN：1528-7505

文摘

We have investigated the evolution of microstructure and magnetic properties of thermally blocked magnetite nanoparticles, aimed for immunoassay applications, during their synthesis. High-resolution transmission electron microscopy (HRTEM) investigations of the size, size distribution, morphology, and crystal structure of particles reveal that particles at an early stage of the reaction process are either single crystals or polycrystals containing planar faults and they grow via a combination of reactant (monomer) consumption and oriented attachment at specific crystallographic surfaces because of the strong dipolar character of the 111 surfaces of magnetite. At a later stage of the synthesis reaction, the magnetic attraction strives to align contacting particles with their 111 axis of easy magnetization in parallel and this may also be an active driving force for crystal growth. At latter stages, the crystal growth is dominated by Ostwald ripening leading to smoother crystalline particles with a mean diameter of 16.7 ± 3.5 nm and a narrow size distribution. The magnetic properties of the particles measured using static and dynamic magnetic fields are consistent with the evolution of particle size and structure and show the transition from superparamagnetic to thermally blocked behavior needed for magnetic relaxation-based immunoassay applications.