Synthesis, assembly, and functionalization of polymer-coated ferromagnetic nanoparticles

A novel, robust synthetic methodology has been developed to prepare and functionalize well-defined ferromagnetic cobalt nanoparticles. Polystyrene (PS) surfactants of precise molar mass were prepared using controlled radical polymerization and used in the synthesis of metallic cobalt nanoparticles by the thermolysis of dicobaltoctacarbonyl (Co₂(CO)₈). Transmission electron microscopy (TEM), scanning probe microscopy (AFM, MFM), x-ray diffraction (XRD) and vibrating sample magnometry (VSM) confirmed that uniform (D = 15 nm ± 1.5 nm, PS shell = 2 nm), face centered cubic (fcc) cobalt nanocrystals that were prepared and ferromagnetic at room temperature (M_s = 38 emu/g, H_c = 100 Oe). A ligand exchange strategy to functionalize ferromagnetic nanoparticles was developed with functional polymeric surfactants.