Winnischofer Herbert, Rocha Tulio C R, Nunes Wallace C, Socolovsky Leandro M, Knobel Marcelo, Zanchet Daniela
LNLS-Brazilian Synchrotron Light Laboratory, C.P. 6192, Campinas, SP, 13083-970, Brazil.
ACS Nano. 2008 Jun;2(6):1313-9. doi: 10.1021/nn700152w.
This work focuses on synthetic methods to produce monodisperse Ni colloidal nanoparticles (NPs), in the 4-16 nm size range, and their structural characterization. Narrow size distribution nanoparticles were obtained by high-temperature reduction of a nickel salt and the production of tunable sizes of the Ni NPs was improved compared to other methods previously described. The as-synthesized nanoparticles exhibited spherical shape and highly disordered structure, as it could be assigned by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). Annealing at high temperature in organic solvent resulted in an increase of nanoparticle atomic ordering; in this case, the XRD pattern showed an fcc-like structure. Complementary data obtained by X-ray absorption spectroscopy confirmed the complex structure of these nanoparticles. Temperature dependence of the magnetic susceptibility of these highly disordered Ni NPs showed the magnetic behavior cannot be described by the conventional superparamagnetic theory, claiming the importance of the internal structure in the magnetic behavior of such nanomaterials.
这项工作聚焦于合成方法，以制备尺寸范围在4 - 16纳米的单分散镍胶体纳米颗粒（NPs）及其结构表征。通过镍盐的高温还原获得了窄尺寸分布的纳米颗粒，并且与先前描述的其他方法相比，镍纳米颗粒可调尺寸的制备得到了改进。所合成的纳米颗粒呈现出球形和高度无序的结构，这可以通过X射线衍射（XRD）和高分辨率透射电子显微镜（HRTEM）来确定。在有机溶剂中进行高温退火导致纳米颗粒原子有序度增加；在这种情况下，XRD图谱显示出类似面心立方（fcc）的结构。通过X射线吸收光谱获得的补充数据证实了这些纳米颗粒的复杂结构。这些高度无序的镍纳米颗粒的磁化率与温度的关系表明，其磁行为不能用传统的超顺磁理论来描述，这表明内部结构在这类纳米材料的磁行为中具有重要性。
