Novel one-phase synthesis of thiol-fuctionalized gold, palladium, and iridium nanoparticles using superhydride

A new, facile, general one-phase synthesis for thiol-functionalized gold, p alladium, and iridium nanoparticles, using tetrahydrofuran (THF) as the sol vent and lithium triethylborohydride (Superhydride) as the reducing agent, is presented. For octadecanethiol-functionalized gold (Au/ODT) nanoparticle s, HRTEM of drop-cast particle-films revealed the formation of spherical pa rticles of d = 4 +/- 0.3 nm average size. Electron diffraction shows fee pa cking arrangement, similar to that of bulk gold. The crystalline gold cores are surrounded with closely packed n-alkyl chains mainly in an all-trans c onformation, adopting orthorhombic packing as confirmed by FTIR spectroscop y. Particles are arranged in a discrete solidlike assembly with a correlati on length of similar to 5 nm, as the interparticle distance (center-to-cent er) and a constant edge-to-edge distance of 1 nm as shown by FFT analysis. Using the same synthetic procedure gold nanoparticles functionalized with 1 1-hydroxyundecane-1-thiol and with 4'-bromo-4-mercaptobiphenyl were prepare d. 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 br oader with the majority of particles between 2.25 and 4.25 nm. Both nanopar ticles are crystalline with fee packing. FTIR spectroscopy reveals that oct adecyl chains are close-packed in all-trans conformation, and that there is presumably one chain in unit cell.