Cobalt chains composed of hexagonal intercrossed microplatelets: shape-controlled synthesis, growth mechanism, and magnetic properties.

Self-assembled Co chains made up of hexagonal intercrossed microplatelets have been fabricated via a facile solvothermal approach in a mixed solution of ethylene glycol (EG) and ethylenediamine (EDA) with poly(vinylpyrrolidone) (PVP) and dodecanethiol (DDT) as surfactants. The morphology and size of the products can be easily controlled through properly monitoring the synthetic conditions, such as the volume ratio of EG/EDA, reaction temperature, reaction time, concentrations of NaOH, and the amount of both PVP and dodecanethiol. Based on a series of contrast experiments, a stepwise growth mechanism of Co chains was rationally conjectured. During the shape evolution process, layered β-Co(OH)2 platelets were first formed and then reduced to Co platelets, which finally developed to one-dimensional Co chains composed of hexagonal close-packed microplatelets. It is noteworthy that hexagonal Co microplatelets were inherited from their layered precursor Co(OH)2 microplatelets obtained in the initial stage. Compared to bulk cobalt, the as-obtained platelet-like Co microchains manifested an enhanced coercivity (Hc) and a decreased saturation magnetization (Ms), which could be ascribed to the highly anisotropic shape of platelet-like subunits. Such platelet-like 1D cobalt microchains are expected to afford new opportunities for applications in the field of magnetic storage and catalysis.