Department of Chemical and Geological Sciences, Università di Cagliari , S.S. 554 bivio per Sestu, 09042, Monserrato, Italy.
INSTM , Cagliari Unit, Via Giuseppe Giusti, 9, 50121 Firenze, Italy.
ACS Nano. 2017 Aug 22;11(8):7889-7900. doi: 10.1021/acsnano.7b02349. Epub 2017 Jul 26.
An easy, low-cost, repeatable seed-mediated growth approach in solvothermal condition has been proposed to synthesize bimagnetic spinel ferrite core-shell heterostructures in the 10-20 nm particle size range. Cobalt ferrite and manganese ferrite nanoparticles (CoFeO and MnFeO) have been coated with isostructural spinel ferrites like maghemite/magnetite, MnFeO, and CoFeO with similar cell parameters to create different heterostructures. The conventional study of the structure, morphology, and composition has been combined with advanced techniques in order to achieve details on the interface at the nanoscale level. Clear evidence of the heterostructure formation have been obtained (i) indirectly by comparing the Fe Mössbauer spectra of the core-shell samples and an ad hoc mechanical mixture and (ii) directly by mapping the nanoparticles' chemical composition by electron energy loss spectroscopy (EELS) and energy-dispersive X-ray spectroscopy (EDX) in the scanning transmission electron microscopy mode (STEM). In addition, chemical-sensitive electron tomography in STEM-EDX mode has been applied in order to obtain detailed 3D images with a sub-nanometer spatial resolution.
已经提出了一种简单、低成本、可重复的溶剂热条件下的种子介导生长方法，用于在 10-20nm 粒径范围内合成双磁自旋体铁氧体核壳异质结构。钴铁氧体和锰铁氧体纳米粒子（CoFeO 和 MnFeO）已经被等结构的尖晶石铁氧体如磁赤铁矿/磁铁矿、MnFeO 和 CoFeO 包覆，这些铁氧体具有相似的晶格参数，以形成不同的异质结构。已经结合了先进的技术，对结构、形态和组成进行了常规研究，以便在纳米尺度上获得界面的详细信息。已经获得了异质结构形成的明确证据：（i）通过比较核壳样品和专门的机械混合物的 Fe Mössbauer 光谱间接获得，（ii）通过电子能量损失光谱（EELS）和能量色散 X 射线光谱（EDX）在扫描透射电子显微镜模式（STEM）中直接映射纳米颗粒的化学成分直接获得。此外，已经应用了化学敏感的 STEM-EDX 电子层析成像，以获得具有亚纳米空间分辨率的详细 3D 图像。
