Synthesis of Au130(SR)50 and Au130−xAgx(SR)50 nanomolecules through core size conversion of larger metal clusters

Abstract

Gold nanomolecules with a precise number of metal atoms and thiolate ligands are being used for catalysis, biosensing, drug delivery and as alternative energy sources. Highly monodisperse products, with reproducible synthesis and complete characterization, are essential for these purposes. Post synthetic etching is used to synthesize highly stable gold nanomolecules. We report a synthetic protocol for the scalable synthesis of Au₁₃₀(SR)₅₀ for the first time, by etching of larger clusters via a core conversion process. Au₁₃₀(SR)₅₀ is not present in the crude product, but, is exclusively formed by etching larger clusters (>40 kDa). This is the first evidence that larger nanocluster cores convert to Au₁₃₀(SR)₅₀. The special stability of Au₁₃₀(SR)₅₀ is confirmed by the formation of Au_130−x(metal)_x(SR)₅₀, where R = CH₂CH₂Ph, C₆H₁₃, C₁₂H₂₅ and metal = Ag, Pd. Au_xAg_130−x(SR)₅₀ is isolated and characterized with two different Au : Ag precursor ratios. Upon alloying there is a change in the optical features of this 130-metal atom nanomolecule. To understand the process of etching and core conversion, a possible mechanism is being proposed. Highly stable nanomolecules like this can find potential applications in high temperature catalysis and sensing.