Thiolate-protected Au(20) clusters with a large energy gap of 2.1 eV

Manzhou Zhu; Huifeng Qian; Rongchao Jin

doi:10.1021/ja902208h

Thiolate-protected Au(20) clusters with a large energy gap of 2.1 eV

J Am Chem Soc. 2009 Jun 3;131(21):7220-1. doi: 10.1021/ja902208h.

Authors

Manzhou Zhu¹, Huifeng Qian, Rongchao Jin

Affiliation

¹ Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, USA.

PMID: 19432453
DOI: 10.1021/ja902208h

Abstract

We report a kinetically controlled approach to synthesizing thiolate-capped 20-atom gold clusters. ESI mass spectrometry analysis in combination with other methods, including elemental analysis, XPS, NMR, and thermogravimetric analysis, determines the cluster composition to be Au(20)(SCH(2)CH(2)Ph)(16). The Au(20)(SCH(2)CH(2)Ph)(16) clusters exhibit a stepwise, multiple-band optical absorption spectrum, reminiscent of quantum confinement behavior. The optical energy gap is determined to be E(g) approximately 2.15 eV; this HOMO-LUMO gap is remarkably larger than that of Au(25)(SR)(18) (1.3 eV). The Au(20)(SCH(2)CH(2)Ph)(16) clusters were also found to be particularly robust again excess thiol etching, in contrast to the previous report on the thiol etching stability of a series of glutathione-capped Au(n)(SG)(m) (n < 25) clusters. This stability difference might indicate some structural differences between Au(20)(SCH(2)CH(2)Ph)(16) and Au(n)(SG)(m) (n < 25). The crystal structure of the Au(20)(SCH(2)CH(2)Ph)(16) cluster remains to be unraveled in future work.