Resolving material-specific structures within Fe <inf>3</inf> O <inf>4</inf> |γ-Mn <inf>2</inf> O <inf>3</inf> core|shell nanoparticles using anomalous small-angle X-ray scattering

Here it is demonstrated that multiple-energy, anomalous small-angle X-ray scattering (ASAXS) provides significant enhancement in sensitivity to internal material boundaries of layered nanoparticles compared with the traditional modeling of a single scattering energy, even for cases in which high scattering contrast naturally exists. Specifically, the material-specific structure of monodispersed Fe 3 O 4 |γ-Mn 2 O 3 core|shell nanoparticles is determined, and the contribution of each component to the total scattering profile is identified with unprecedented clarity. We show that Fe 3 O 4 |γ-Mn 2 O 3 core|shell nanoparticles with a diameter of 8.2 ± 0.2 nm consist of a core with a composition near Fe 3 O 4 surrounded by a (Mn x Fe 1-x ) 3 O 4 shell with a graded composition, 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 Fe 3 O 4 cores without a coating shell. 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 multiple-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. © 2013 American Chemical Society.