Synthesis of Coinage-Metal Nanoparticles from Mesityl Precursors

Abstract

An anhydrous route for the synthesis of amine-capped coinage-metal nanoparticles (NP) has been developed using coinage-metal mesityl (mesityl = 2,4,6-Me3C6H2) derivatives. Under an argon atmosphere, crystalline [Cu(μ-mesityl)]5, [Ag(μ-mesityl)]4, and [Au(μ-mesityl)]5 were readily dissolved in octylamine (0.3 M solution) and subsequently injected into a heated hexadecylamine solution (300 °C), generating the corresponding metal nanoparticles. After washing with methanol and extracting with toluene, oxide-free coinage NPs were isolated and characterized by UV−vis spectroscopy and transmission electron microscopy. Under these conditions, the spherical NPs were found to be 8−9 nm in size for Cu° (no surface oxide present), 9 nm for Ag°, and 8−80 nm for Au°. Reducing the concentration of the precursor solution, the temperature of the solution, and the time of reaction led to the synthesis of Au° NPs that were 12 ± 1 nm in size.