Solvothermal synthesis of magnetic chains self-assembled by flowerlike cobalt submicrospheres

Cobalt chains with lengths of up to 4-20 μm, self-assembled by flowerlike cobalt submicrospheres, have been synthesized at 200 °C for 4 h by a solvothermal method with the surfactant poly(vinyl pyrrolidone) (PVP). The average diameter of individual flowerlike submicrospheres is 700-900 nm, which are composed of compact nanosheets with an average thickness of about 50 nm. The products were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). The effects of synthetic conditions, such as reaction temperature and the amount of reducing agent, on the morphology and size of the chains were investigated. The growth mechanism of the chains was proposed, based on the evolution of the structure and the morphology with increasing the reaction time. The magnetic hysteresis loops at 5 and 295 K of the chains show ferromagnetic characteristics with coercivities of 347 and 90 Oe, respectively. Our work may shed light on the design fabrication of one-dimensional chainlike structures self-assembled by complex three-dimensional architectures of materials.