Ligand control in thiol stabilized Au38 clusters

Abstract

Alkyl thiols (C_nH_2n + 1SH) with chain lengths (n = 4, 6, 8, 12, 16) were investigated for etching the polydisperse Au_n(SG)_m mixture in order to obtain nearly monodisperse Au₃₈(SR)₂₄ clusters. FT-IR studies demonstrate that all thiol ligands bound to Au₃₈ clusters are highly ordered and in an all-trans state. X-ray absorption studies at the S K-edge as well as at the Au L₃ edge show similarities between Au(I)S species and Au₃₈(SR)₂₄ clusters, in good agreement with the ‘S-Au-S’ capping motifs in the Au₃₈(SR)₂₄ structure and confirming charge transfer from gold to sulfur atoms. We report for the first time the use of Wide-angle X-ray scattering (WAXS) analysis as a more reliable tool than TEM to evaluate particle size and size distributions Au₃₈(SR)₂₄ clusters.