Restoration of bulk magnetism in Fe oxide NPs by surfactant molecules

Surfactant Organic Molecules Restore Magnetism in Metal-Oxide Nanoparticle Surfaces.
Juan Salafranca, Jaume Gazquez, Nicolás Pérez, Amílcar Labarta, Sokrates T. Pantelides, Stephen J. Pennycook, Xavier Batlle, and Maria Varela
Nano Lett., 12, 2499 (2012)

Left: Density of states (DOS) projected over the majority spin d orbitals in the octahedral iron sites within different crystal environments. Organic acid bonded to magnetite surface. DOS projected over octahedral iron bonded to the organic acid. Because of the influence of the oxygen ions in the carboxylic group, occupancies are very similar to the bulk case, and the reduction of magnetization at the surface is partially lifted. Middle:  High-resolution Z-contrast STEM images of a Fe3O4 NP showing high crystal quality. Right: Top: L2,3 profile along the direction of the blue arrow in panel d (in red and in black for I+ and I− L23 ratio maps respectively). Bottom: difference between I+ and I− L2,3 ratios along the NP. The scale bar represents 5 nm in all panels.