Left: (A–F) TEM images of low and high magnification of iron oxide NPCs using CTAB as an emulsifier. The initial size of nanoparticles in the organic phase were: (A, B) 3 nm, (C, D) 6 nm, and (E, F) 12 nm respectively. Scale bars: A, C, 150 nm; B, D 20 nm; E, 300 nm; F, 40 nm. Also See Figure S1 for larger view. Right: top: AFM image of NPCs made from 6 nm iron oxide NPs; bottom: extracted height information from two isolated clusters (line 1) and four contacting clusters in a row (line 2). The TEM images along with AFM characterization indicate that the NPCs were spheres composed of densely packed individual nanoparticles.