Toward understanding the growth mechanism of Aun(SR)m nanoclusters: effect of solvent on cluster size

Abstract

Despite the recent advances in size-controlled synthesis of thiolate-protected Au_n(SR)_m nanoclusters, understanding the growth mechanism of nanoclusters still significantly lags behind. In this work, we report an important finding that the reaction medium plays a major role in influencing the final cluster size. Specifically, we focus on the one-phase synthetic process that leads to predominant formation of Au₂₅(SR)₁₈ or Au₁₄₄(SR)₆₀—two ubiquitous nanoclusters in nanocluster synthesis. When THF, acetone or ethyl acetate was used as the reaction solvent, we found that Au₂₅ was formed as the major product, while in methanol or acetonitrile, predominant Au₁₄₄ and some larger nanoparticles were formed. We mapped out some details of the underlying growth mechanism of nanoclusters, in which the reaction medium was found to affect the Au(I) intermediate (i.e. size and aggregation state), which subsequently affects the final size of gold nanoclusters. The obtained insight into the growth of nanoclusters is expected to contribute to the development of new synthetic strategies.