The Dynamics of Noble Metal Atom Penetration through Methoxy-Terminated Alkanethiolate Monolayers

Amy V. Walker, Timothy B. Tighe, Orlando M. Cabarcos, Michael D. Reinard, Brendan C. Haynie, Sundararajan Uppili, Nicholas Winograd, David L. Allara

Research output: Contribution to journalArticle

157 Scopus citations

Abstract

We have studied the interaction of vapor-deposited Al, Cu, Ag, and Au atoms on a methoxy-terminated self-assembled monolayer (SAM) of HS(CH 2)16OCH3 on polycrystalline Au{111}. Time-of-flight secondary ion mass spectrometry, infrared reflection spectroscopy, and X-ray photoelectron spectroscopy measurements at increasing coverages of metal show that for Cu and Ag deposition at all coverages the metal atoms continuously partition into competitive pathways: penetration through the SAM to the S/substrate interface and solvation-like interaction with the -OCH3 terminal groups. Deposited Au atoms, however, undergo only continuous penetration, even at high coverages, leaving the SAM "floating" on the Au surface. These results contrast with earlier investigations of Al deposition on a methyl-terminated SAM where metal atom penetration to the Au/S interface ceases abruptly after a ∼1:1 Al/Au layer has been attained. These observations are interpreted in terms of a thermally activated penetration mechanism involving dynamic formation of diffusion channels in the SAM via hopping of alkanethiolate-metal (RSM-) moieties across the surface. Using supporting quantum chemical calculations, we rationalized the results in terms of the relative heights of the hopping barriers, RSAl > RSAg, RSCu > RSAu, and the magnitudes of the metal-OCH3 solvation energies.

Original languageEnglish (US)
Pages (from-to)3954-3963
Number of pages10
JournalJournal of the American Chemical Society
Volume126
Issue number12
DOIs
StatePublished - Mar 31 2004

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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