Fe Nanoparticles: Synthesis, Structural Characterization And Properties

Iron is the fourth most plentiful element on the Earth and has been important as a material to mankind for more than 2000 years. In recent decades nanosized iron particles have been extensively investigated and have found use in a wide range of applications including in magnetic recording media, biomedical applications, and catalysis. Traditional synthetic routes only yield spherical nanoparticles with body-centered cubic (BCC) structure. As the chemical and physical properties depend essentially on the size and shape of particles, the fabrication and characterization of Fe nanoparticles with well-defined shapes is an important challenge.We successfully synthesized icosahedral face-centered cubic (FCC) Fe nanoparticles by a specifically designed thermodynamic governed synthetic route, which is facile but highly efficient and reproducible. With the aberration-corrected transmission electron microscopy (TEM), the unique icosahedral structure's pseudo-twofold, threefold and pseudo-fivefold axes were directly observed for the first time and verified by computer simulation.Moreover, FCC-Fe nanoparticles with decahedral, fivefold-twinned, triangular plate and cubic morphology have also been synthesized and characterizted with electron microscopy. A size-dependent crystal shape transformation between the different morphologies has been observed and explained on the basis of thermodynamic calculations. Small sizes favor icosahedral nanoparticles; decahedral and fivefold-twinned nanorods are favored at intermediate sizes, and triangular plate and cubic at large sizes.In addition, twinned FCC-Fe nanoparticle with size of about 10 nm have been successfully synthesized on carbon nanotubes (CNTs) based on polyethylene glycol (PEG) reduction combined with heating method. These twinned FCC-Fe nanoparticles are superparamagnetic at room temperature with the blocking temperature TB =34 K, specific saturation magnetizationσs = 80 Am 2/kg and magnetic anisotropy density K eff= 2.24×10 4 Jm-3 at a low temperature. Moreover, using M13 virus as a biological template, spherical FCC-Fe nanoparticles with diameter about 10 nm were fabricated around the surface of M13 virus during the specific adsorption of virus towards Fe ions under reduced environment. Furthermore, this virus-mediated FCC Fe nanoparticle system successfully reduced contaminable U(VI) into UO2 crystals with diameters of 2-5 nm in a green and convenient route.