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Silica coated iron nanoparticles: synthesis, interface control, magnetic and hyperthermia properties

机译：二氧化硅涂层的铁纳米粒子：合成，界面控制，磁和高温性质

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This work provides a detailed study on the synthesis and characterization of silica coated iron nanoparticles (NPs) by coupling Transmission Electronic Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS) and magnetic measurements. Remarkably, iron NPs (of 9 nm of mean diameter) have been embedded in silica without any alteration of the magnetization of the iron cores, thanks to an original protocol of silica coating in non alcoholic medium. Tuning the synthesis parameters (concentration of reactants and choice of solvent), different sizes of Fe@SiO _(2) composites can be obtained with different thicknesses of silica. The magnetization of these objects is fully preserved after 24 h of water exposure thanks to a thick (14 nm) silica layer, opening thus new perspectives for biomedical applications. Hyperthermia measurements have been compared between Fe and Fe@SiO _(2) NPs, evidencing the self-organization of the free Fe NPs when a large amplitude magnetic field is applied. This phenomenon induces an increase of heating power which is precluded when the Fe cores are immobilised in silica. High-frequency hysteresis loop measurements allowed us to observe for the first time the increase of the ferrofluid susceptibility and remanence which are the signature of the formation of Fe NPs chains.
机译：这项工作通过耦合透射电子显微镜（TEM），X射线光电子能谱（XPS）和磁测量，对二氧化硅包覆的铁纳米颗粒（NPs）的合成和表征进行了详细研究。值得注意的是，由于非酒精介质中二氧化硅涂层的原始方案，铁纳米颗粒（平均直径为9 nm）已嵌入二氧化硅中，铁芯的磁化强度没有任何改变。调整合成参数（反应物的浓度和溶剂的选择），可以使用不同厚度的二氧化硅获得不同尺寸的Fe @ SiO_（2）复合材料。暴露在水中24小时后，由于厚的（14 nm）二氧化硅层，这些物体的磁化得以完全保留，从而为生物医学应用开辟了新的前景。已对Fe和Fe @ SiO _（2）NP之间的高温测量进行了比较，证明了在施加大振幅磁场时自由Fe NP的自组织。这种现象引起加热功率的增加，而当铁芯固定在二氧化硅中时，这是无法避免的。高频磁滞回线测量使我们能够首次观察到铁磁化率和剩磁的增加，这是铁纳米颗粒链形成的标志。

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