Sonochemical Deposition of Air-Stable Iron Nanoparticles on Monodispersed Carbon Spherules V. G. Pol, † M. Motiei, † A. Gedanken,* ,† J. Calderon-Moreno, ‡ and Y. Mastai § Department of Chemistry, Bar-Ilan University, Ramat-Gan, 52900 Israel, Materials and Structures Laboratory, Tokyo Institute of Technology, 4259, Nagatsuta, Midori-ku, 226-8503 Yakohama, Japan, and Max-Planck-Institute of Colloids and Interfaces, Colloid Chemistry, Forschungs Campus Golm, Am Mu ¨ hlenberg, Haus 2, D-14424 Potsdam, Germany Received September 6, 2002. Revised Manuscript Received December 12, 2002 A novel route was used to prepare “perfect spherical” monodispersed carbon with a smooth surface, which has a surface area of 8 m 2 /g. Air-stable iron nanoparticles with an average size of ∼10 nm were deposited on the surface of preformed carbon spherules with the aid of power ultrasound. This coating was achieved by ultrasonic irradiation of a slurry of carbon spherules and Fe(CO) 5 in diphenylmethane for 90 min under an argon atmosphere. The as-prepared amorphous material was annealed in argon at 700 °C, forming air-stable iron deposited on carbon spherules. The product was characterized by XRD, TEM, EDAX, BET surface area, HR-SEM, TGA, DSC, magnetic measurements, electron paramagnetic reso- nance, and Raman spectroscopy. Introduction The discovery of “new forms of carbon”, for example, fullerenes and carbene-like one-dimensional struc- tures, 1,2 has greatly promoted the investigation of carbonaceous materials. A classification of these spheri- cal carbon structures has been recently proposed by Inagaki, 3 according to their nanometric texture, that is, concentric, radial, or random arrangement of carbon layers. Carbon spheres, 4-6 beads, 7 onions, 8 and hollow carbons 9 have been synthesized by very different pro- cesses. Accordingly, various applications have been intensively developed, of which we highlight nano- devices, 10a energy storage, 10b separation technology, 10c and so forth, which are attracting much interest from carbon scientists worldwide. Enormous research was carried out on the deposition of a variety of metal particles onto ceramic substrates and magnetic colloids immobilized in a polymer matrix. In most of the experi- ments silica and alumina were used as a substrate. Alumina, as well as silica, are dissolved 10d at high pHs and the alumina is also attacked at very low pHs. In contrast, activated carbons are stable in both acid and basic media. The sonochemical method is simple and it is operated at ambient conditions. It is also easy to control the particle size of the product by varying the concentration of the precursors in the solution. 11a Power ultrasound effects chemical changes due to cavitation phenomena involving the formation, growth, and implosive collapse of bubbles in liquid. 11b These phenomena have been exploited to prepare a variety of metals, oxides, and composite nanoparticles 11c and have recently been ex- tended to produce core-shell-type materials. 11d In re- cent publications, we discussed how we uniformly deposited metallic silver 11e nanoparticles on silica spheres and europium oxide nanolayer 11f on titania by control- ling experimental conditions with the aid of power ultrasound. Ultrasound-induced cavitations have also been used to coat nanosized nickel on alumina micro- spheres, 11g and iron/iron oxide on silica, 11h imparting a magnetic function to the particles. 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