Diffraction anomalous fine structure study of iron/iron oxide nanoparticles,

Diffraction anomalous fine structure is a recently developed technique which can provide a measurement of the local structure of a given element in a particular phase or crystallographic site. Most previous investigations have applied the technique to bulk solids, thin films, and nano-dots or wires on crystalline substrates. In this paper, the technique is applied to highly disordered nanometre-sized Fe/Fe oxide core-shell nanocrystalline powders, the diffraction patterns of which exhibit weak and greatly broadened diffraction peaks. Focusing on the oxide shell diffraction peaks, a qualitative analysis of the near-edge spectral region and a quantitative analysis of the extended energy region are provided; in particular, good quality fittings of the extended range spectra are obtained. The local structure is selectively probed around the tetrahedral and octahedral sites of the oxide shell, finding the presence of a high degree of structural disorder. This study demonstrates that diffraction anomalous fine structure can now be fruitfully applied to nanocrystalline powders