Figure 3

Structural/compositional characterizations of hollow iron oxide nanoparticles (HIONs). Transmission electron microscopy (TEM) images of HIONs at (a) low and (b) high magnifications. (c) Scanning electron microscope image of HIONs. Element mapping of (d) Fe and (e) O of HIONs. (f) The distribution of Fe and O elements by linear scanning of the inset dark-field TEM image.