Composite magnetite–gold mesoscopic particles were prepared by deposition of Au onto
magnetite nanoparticles. The surface morphology of the mesoparticles could be tuned by
controlling the factors that affect the kinetics of the reactions and by adding surfactants that
direct the growth of gold crystals. The internal structure of composite mesoparticles was
analyzed by focused ion beam and scanning electron microscopy. A particle-mediated
growth mechanism of formation was proposed.