Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Zaragoza, Spain.
Nanotechnology. 2013 Apr 19;24(15):155705. doi: 10.1088/0957-4484/24/15/155705. Epub 2013 Mar 22.
We present radio frequency transverse susceptibility (TS) measurements on oleic acid-coated and SiO2-coated Fe3-xO4 magnetite nanoparticles. The effects of the type of coating on the interparticle interactions and magnetic anisotropy are evaluated for two different particle sizes in powder samples. On the one hand, SiO2 coating reduces the interparticle interactions as compared to oleic acid coating, the reduction being more effective for 5 nm than for 14 nm diameter particles. On the other hand, the magnetic anisotropy field at low temperature is lower than 1 kOe in all cases and independent of the coating used. Our results are relevant concerning applications in biomedicine, since the SiO2 coating renders 5 and 14 nm hydrophilic particles with very limited agglomeration, low anisotropy, and superparamagnetic behavior at room temperature. The TS technique also allows us to discriminate the influence on the anisotropy field of interparticle interactions from that of the thermal fluctuations.
我们展示了油酸包覆和 SiO2 包覆的 Fe3-xO4 磁铁矿纳米颗粒的射频横向磁化率 (TS) 测量结果。在粉末样品中，对于两种不同的粒径，评估了涂层类型对颗粒间相互作用和磁各向异性的影响。一方面，SiO2 涂层比油酸涂层减少了颗粒间的相互作用，对于 5nm 直径的颗粒比 14nm 直径的颗粒更为有效。另一方面，在所有情况下，低温下的磁各向异性场都低于 1kOe，且不依赖于所使用的涂层。我们的结果与生物医学应用相关，因为 SiO2 涂层使 5nm 和 14nm 的亲水颗粒具有非常有限的团聚、低各向异性和室温下的超顺磁性行为。TS 技术还允许我们区分颗粒间相互作用对各向异性场的影响和热波动的影响。
