Controlled synthesis of cobalt flowerlike architectures by a facile hydrothermal route

Cobalt flowerlike architectures composed of hexagonal nanoplatelets have been synthesized by a simple hydrothermal reduction method. The architectures are fabricated by the reaction of CoCl₂ with NaOH at 140-180 °C in the presence of sodium dodecyl benzenesulfonate (SDBS), with NaH ₂PO₂·H₂O as reducing agent. The diameters of the flowers range from 8 to 10 μ m, and the average thickness of the hexagonal sheets is about 100 nm. Higher reaction temperatures and the proper concentration of sodium hydroxide (NaOH) are key requirements for the fabrication of the flowerlike architectures. A growth mechanism for these architectures is proposed on the basis of the characterization by X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The magnetic hysteresis loops at 5 K and 295 K of the cobalt flowerlike architectures show ferromagnetic characteristics with coercivities of 371 Oe and 197 Oe, respectively. Our work may shed light on the designed fabrication of complex 3D architectures of other materials.