Preparation of three-dimensional leaflike cobalt microcrystals and decoration of their surface with silver nanoparticles

Three-dimensional leaflike metallic cobalt microcrystals with radiating arrangement from each individual centers were successfully synthesized via a hydrothermal reduction approach. Time-dependent experiments were carried out to verify the rational growth mechanism of the obtained leaflike products, in which a morphology transformation from cobalt hydroxide hexagonal nanoplates to dendritic cobalt crystals and end with leaflike cobalt products was observed. Structure characterizations suggest that this transformation is associated with diffraction-limited aggregation, oriented attachment, and Ostwald ripening. XRD measurement indicates that the cobalt products exhibit a combination of hexagonal-close-packed (hcp) and face-centered-cubic (fcc) crystalline character. The products exhibit a remarkable enhanced coercivity of 193.8 Oe compared against bulk cobalt due to the shape anisotropy and hcp crystalline structure. The effect of different solvents on morphological and magnetic properties of the product was also validated. These leaflike cobalt crystals were further used as substrates to decorate their surface with Ag nanoparticles by transmetallation reaction. These Ag-modified cobalt leaves could have the potential application value in fields of magnetically recyclable catalysts and antibacterial materials.