Bifunctional FePt Core−Shell and Hollow Spheres:  Sonochemical Preparation and Self-Assembly

Abstract

The sonochemical preparation of FePt/SiO2 and FePt/ZnS/SiO2 core−shell and hollow microspheres, as well as their self-assembly into a quasi-monolayer, was demonstrated. Uniform FePt nanoparticles can be deposited on silica microspheres modified with polyelectrolytes by a sonochemical process, using iron and platinum acetylacetonates as metal precursors. The amine and carboxylic functional groups in the polyelectrolyte layer provided nucleation sites for FePt nanoparticles. Alternatively, if the silica was precoated with ZnS, the nucleation of FePt nanoparticles on the ZnS shell can occur. A high coercivity of 12 kOe for these microspheres was obtained after annealing. A bifunctional microsphere with both luminescence and magnetic properties could be generated after the FePt/ZnS/SiO2 microsphere was annealed in a vacuum.