Novel One-Phase Synthesis of Thiol-Functionalized Gold, Palladium, and Iridium Nanoparticles Using Superhydride Chanel K. Yee, †,‡ Rainer Jordan, †,‡ Abraham Ulman,* ,‡,| Henry White, †,§ Alexander King, § Miriam Rafailovich, § and Jonathan Sokolov †,§ Department of Chemical Engineering, Chemistry and Materials Science, Polytechnic University, Six Metrotech Center, Brooklyn, New York 11201, Department of Materials Sciences and Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794-2275 Received January 7, 1999. In Final Form: February 25, 1999 A new, facile, general one-phase synthesis for thiol-functionalized gold, palladium, and iridium nanoparticles, using tetrahydrofuran (THF) as the solvent and lithium triethylborohydride (Superhydride) as the reducing agent, is presented. For octadecanethiol-functionalized gold (Au/ODT) nanoparticles, HRTEM of drop-cast particle-films revealed the formation of spherical particles of d ) 4 ( 0.3 nm average size. Electron diffraction shows fcc packing arrangement, similar to that of bulk gold. The crystalline gold cores are surrounded with closely packed n-alkyl chains mainly in an all-trans conformation, adopting orthorhombic packing as confirmed by FTIR spectroscopy. Particles are arranged in a discrete solidlike assembly with a correlation length of ∼5 nm, as the interparticle distance (center-to-center) and a constant edge-to-edge distance of 1 nm as shown by FFT analysis. Using the same synthetic procedure gold nanoparticles functionalized with 11-hydroxyundecane-1-thiol and with 4′-bromo-4-mercaptobiphenyl were prepared. TEM images of drop-cast Pd/ODT and Ir/ODT nanoparticles show an average size of 2.25 nm for the former, while for the latter the distribution is broader with the majority of particles between 2.25 and 4.25 nm. Both nanoparticles are crystalline with fcc packing. FTIR spectroscopy reveals that octadecyl chains are close-packed in all-trans conformation, and that there is presumably one chain in unit cell. Introduction Submicrometer size materials have attracted a remarkable academic and industrial effort of research due to their potential applications ranging from funda- mental studies in quantum physics, fabricating of com- posite materials, information storage/optoelectronics, and immunoassays to catalysts. A precise control of size and chemical behavior (stability and reactivity) by means of the synthesis itself is one of the main targets due to the direct correlation of intriguing new properties with the particle size, bridging the gap between molecules and bulk materials. 1 In the past few years, there has been significant research in the area of nanoparticles. Semiconductors, 2 including silicon 3 and germanium, 3b magnetic, 4 and different metal- lic nanoparticles such as iron, 5 cobalt, 5,6 nickel, 5,7 copper, 8 zinc, 9 rhodium, 10 ruthenium, 11 gold, 1b,f,12 and silver 12b,13 were prepared and studied. A considerable effort was focused on systems of colloidal gold, for which a broad variety of synthetic procedures was reported. 1b,f While native colloidal gold solutions are only stable for a restricted time, Brust et al. 14 were able to overcome this problem by developing a facile method for the in situ preparation of alkanethiol-stabilized gold † NSF MRSEC for Polymers at Engineered Interfaces. ‡ Polytechnic University. § State University of New York at Stony Brook. | Telephone: 718-260-3119. Fax: 718-260-3125. E-mail: aulman@duke.poly.edu. (1) The exponentially increasing number of publications demonstrates by itself the potential applications suitable for these new materials. 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