Figure 3.

SEM images of DMSA-coated γ-Fe₂O₃ nanoparticles after solvent drying. In the presence of alternating magnetic field with different frequency (1 kHz (a), 5 kHz (b), 10 kHz (c), 50 kHz (d), and 100 kHz (e)). The concentration of sample was 12.5 μg/ml. There seemed no obvious difference between samples. In fact, the DMSA-coated nanoparticles cannot be induced to form one-dimensional assemblies by alternating magnetic field with any frequency in our experiments. Thus, the assembly of DMSA-coated nanoparticles seemed little dependent upon the frequency.