Magnetic Mesoflowers: Synthesis, Assembly, and Magnetic Properties†

An efficient method to introduce magnetic attributes to highly complex Au mesostructures by overlayer growth is demonstrated. The overlayer is nanostructured in all the cases investigated. A possible mechanism for the reduction of ions on the surface of Au mesoflowers and the consequent formation of hybrid mesoflowers is discussed. We studied the magnetic hysteresis behavior of Au/Ni, Au/Co, and Au/Pt/Ni mesoflowers at room temperature. Compared to the bulk metals, a decrease in saturation magnetization was observed in all the three hybrid magnetic mesoflowers, which may be due to the nanoscale structure. Assemblies of various magnetic mesoflowers extending over hundreds of micrometers on indium tin oxide (ITO) substrates have been made by magnetic field-induced self-assembly. Particles are assembled to form elongated chains, oriented parallel to the direction of the applied magnetic field.