Synthesis and characterization of composite nanoparticles comprised of gold shell and magnetic core/cores

Nanoparticles comprised of gold shell and magnetite/maghemite inclusion were synthesized by overgrowing the gold shell onto magnetic seeds. Results from transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) indicate that there are two populations of well-dispersed nanoparticles: one is the small-diameter iron oxide particles with metallic gold shell, while the other is the moderately large gold particles containing magnetic core/cores. A close relation between the maximum optical absorbance of characteristic gold colloid and the magnetic field applied during performance of high-gradient magnetic filtration confirms further that nearly all the particles of Au character contain magnetic inclusion.