Rabias Ioannis, Fardis Michael, Devlin Eamonn, Boukos Nikos, Tsitrouli Danai, Papavassiliou George
Institute of Materials Science, NCSR Demokritos, 15310 Aghia Paraskeui, Athens, Greece.
ACS Nano. 2008 May;2(5):977-83. doi: 10.1021/nn700414w.
The influence of coating on interparticle interactions in ferrofluids has been investigated using various techniques such as Mossbauer spectroscopy, magnetometry, transmission electron microscopy, photon correlation spectroscopy, X-ray diffraction, X-ray photoelectron, and resonance micro-Raman spectroscopy. Aging and spin-glass-like behavior was investigated in frozen ferrofluids of various concentrations from dense, initial value of 40 mg of coated nanoparticles per 1 mL of water, to dilute 1:10 (4 mg/mL). The as-prepared nanoparticles, core size 7-8 nm, were subsequently coated with a gummic acid corona of 20 nm thickness, which was observed to prevent agglomeration and to delay aggregation even in dense ferrofluids. The resulting separation of magnetic cores due to the coating eliminated all magnetic interparticle interaction mechanisms, such as exchange and dipoledipole, thus ensuring no aging effects of the magnetic particle system, as manifested in particle agglomeration and precipitation.
利用多种技术，如穆斯堡尔光谱、磁力测量、透射电子显微镜、光子相关光谱、X射线衍射、X射线光电子能谱和共振显微拉曼光谱，研究了涂层对铁磁流体中颗粒间相互作用的影响。对不同浓度的冷冻铁磁流体进行了老化和类自旋玻璃行为的研究，浓度范围从初始的每1 mL水含40 mg包覆纳米颗粒的高密度，到稀释1:10（4 mg/mL）。制备的纳米颗粒，核心尺寸为7 - 8 nm，随后包覆了厚度为20 nm的阿拉伯胶冠层，观察到该冠层即使在高密度铁磁流体中也能防止团聚并延缓聚集。由于涂层导致的磁芯分离消除了所有颗粒间的磁相互作用机制，如交换作用和偶极 - 偶极作用，从而确保了磁颗粒系统不存在老化效应，如颗粒团聚和沉淀所示。
