Size-controlled synthesis of thiol-derivatized gold clusters

Abstract

Thiol-derivatized gold clusters (i.e. nano-sized gold crystals coated with a thiolate monolayer, Au_n(SR)_m, with m ≪ n) based on n-alkanethiols have been obtained by treatment of gold clusters embedded in poly(N-vinylpyrrolidone) (PVP) with thiols. Dodecanethiol (DDT), hexadecanethiol (HDT), and octadecanethiol (ODT) have been used. The polymer-embedded clusters were obtained by reduction of AuCl₄⁻ with ethylene glycol at temperatures ranging from 60 to 110 °C, in the presence of PVP as a stabilizer. This new synthesis route provides complete control over the cluster compound structure, since a variety of alkanethiol molecules can be used and the metal core size can be accurately varied by changing the reactive mixture composition (the PVP/HAuCl₄ weight ratio). The obtained Au–DDT, Au–HDT, and Au–ODT compounds show a hydrophobic nature, are crystalline, and are thermally stable up to ca. 300 °C.