Ambient Synthesis of Au144(SR)60 Nanoclusters in Methanol

Abstract

We report a facile, one-pot method for synthesizing atomically monodisperse Au 144 (SR) 60 nanoclusters under ambient conditions. In this method, gold salt precursor is first mixed with excess thiol and tetraoctylammonium bromide (TOABr) in methanol to form Au(I)-SR polymers. Then, Au(I)-SR is reduced by excess NaBH 4 (aqueous solution) to form nanoclusters. Interestingly, the initially formed, polydisperse Au nanoparticles are size-focused into two monodisperse gold nanoclusters: Au 144 (SR) 60 (major product) and Au 25 (SR) 18 (side product) over a ∼5 h period. The side product (Au 25 (SR) 18 ) can be easily removed by washing the product with acetone, giving rise to pure Au 144 (SR) 60 . This method is applicable to a number of thiol ligands, including PhC 2 H 4 SH and various C n H 2 n +1 SH (where n = 4−8). Some critical parameters to obtain pure Au 144 (SR) 60 have been identified, including the methanol solvent (as opposed to toluene traditionally used), large thiol-to-Au ratios (≥4), the presence of O 2 and tetraoctylammonium halide (TOAX, where X = Br, Cl). The facile synthetic method and the product made by this method should largely contribute to the practical application of this new type of nanomaterial.