ACS Nano 2013, 7, 921-931.
Kathryn L. Krycka, Julie A. Borchers, German Salazar-Alvarez, Alberto López-Ortega , Marta Estrader, Sonia Estradé, Elin Winkler, Roberto Daniel Zysler, Jordi Sort, Francesca Peiró, Maria Dolors Baró, Chi-Chang Kao and Josep Nogués
DOI: 10.1021/nn303600e
Abstract:
The material specific structure of monodispersed Fe3O4|γ-Mn2O3 core|shell nanoparticles is determined using multiple energy, anomalous, small-angle x-ray scattering (ASAXS). The contribution of each component to the total scattering profile is identified with unprecedented clarity. We show that Fe3O4|γ-Mn2O3 core|shell nanoparticles with a diameter of 8.2 nm ± 0.2 nm consist of a core with a composition near Fe3O4 surrounded by a (MnXFe1−X)3O4 shell with a graded composition, i.e., ranging from X ≈ 0.40 at the inner shell toward X ≈ 0.46 at the surface. Evaluation of the scattering contribution arising from the interference between material-specific layers additionally reveals the presence of Fe3O4cores without a coating shell. Importantly, the present analysis enhances the sensitivity of the method with regard to the chemical boundaries and internal nanoparticle morphology compared with traditional approaches. Finally, it is found that the material-specific scattering profile shapes and chemical compositions extracted by this method are independent of the original input chemical compositions used in the analysis, revealing multi-energy ASAXS as a powerful tool for determining internal nanostructured morphology even if the exact composition of the individual layers is not known a priori.
