ABSTRACT:Studies on the self-assembly of core-shell magnetic nanospheres under or without an external magnetic field are the subject of intense research. It is believed that after being coated by organic molecules, the magnetic nanoparticles can still have chance to form chain-like structure driven by the dipole-dipole interactions while the coated shell minimizes the effect of Van der Waals attractions. However, still there are no direct experimental observations for polymer-modified magnetic colloids sized hundreds of nanometers. In this article, PEG-and PSt-coated Fe 2 O 3 nanospheres were synthesized and their self-assembly behaviors were studied. MFM and TEM measurements reveal that the prepared spheres owning a core-shell structure. Under zero magnetic field, a direct observation of chain-like structure was achieved for the PEG-coated magnetic colloids. For the PSt-modified magnetic spheres, there formed a 2D aligned stripes pattern at the surface of mica when the suspending of sample was dried under an external magnetic field.

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