Size-Focusing synthesis, optical and electrochemical properties of monodisperse Au_(38)(SC_2H_4Ph)_(24) nanoclusters

摘要

We report a facile, high yielding synthetic method for preparing truly monodisperse Au_(38)(SC_2H_4Ph)_(24) nanoclusters. The synthetic approach involves two main steps: first, glutathionate (-SG) protected polydisperse Au_n clusters (n ranging from 38 to ～102) are synthesized by reducing Au(I) - SG in acetone; subsequently, the size-mixed Au_n clusters react with excess phenylethylthiol (PhC_2H_4SH) for ～40 h at 80 °C, which leads to Au_(38)(SC_2H_4Ph)_(24) clusters of molecular purity. Detailed studies by mass spectrometry and UV - vis spectroscopy explicitly show a gradual size-focusing process occurred in the thermal etching-induced growth process. The formula and molecular purity of Au_(38)(SC_2H_4Ph)_(24) clusters are confirmed by electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) mass spectrometry, and size-exclusion chromatography. The optical and electrochemical properties of Au_(38)(SC_2H _4Ph)_(24) clusters show molecule-like behavior and the HOMO - LUMO gap of the cluster was determined to be ～0.9 eV. The size focusing growth process is particularly interesting and may be exploited to synthesize other robust gold thiolate clusters.