Combined TPD and XPS Study of Ligation and Decomposition of 1,6-Hexanedithiol on Size-Selected Copper Clusters Supported on HOPG

Abstract

Ligation and decomposition of 1,6-hexanedithiol on copper clusters have been studied by means of temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). Copper cluster anions were first made via magnetron sputtering, then size selected and soft landed into a frozen matrix of 1,6-hexandithiol on highly ordered pyrolytic graphite (HOPG) maintained at 100 K. After warming up to 298 K, a combination of TPD and XPS were performed to characterize the newly deposited sample. TPD data shed light upon the adsorption and decomposition pathways of 1,6-hexanedithiol molecules on copper clusters. Based on the TPD data, two different binding motifs are proposed: the dangling motif is with one sulfur atom binding to a copper cluster, and the bidentate motif is with both sulfur atoms binding to a copper cluster. Different decomposition products were observed for each binding motif. A series of hydrogen atom titration experiments were designed to provide further evidence for the proposed decomp...