High Bulk Modulus of Nanocrystal γ-Fe₂O₃ with Chemical Dodecyl Benzene Sulfonic Decoration Under High Pressure

Structural transformation in γ-Fe₂O₃ nanocrystals (about 10 nm) with dodecyl benzene sulfonic (DBS) coated is studied by using high-pressure energy dispersive x-ray diffraction of synchrotron radiation and high-resolution transmission electron microscopy (HRTEM). Relative to the bulk crystal, the transition pressure showed a decrease while the compressibility increases significantly up to 375 (±9 GPa). HRTEM picture confirmed that there is surface cladding surrounding nanocrystals due to DBS, which formed new special boundaries between nanocrystals and should be different from the ordinary grain boundaries. The experimental results imply that the surface layers of γ-Fe₂O₃ nanocrystals have strong effect on the compressibility.