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Tripodal Binding Units for Self-Assembled Monolayers on Gold: A Comparison of Thiol and Thioether Headgroups

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  • Tobias Weidner
  • Nirmalya Ballav, Heidelberg University 
  • ,
  • Ulrich Siemeling, University of Kassel
  • ,
  • Dennis Troegel, University of Würzburg
  • ,
  • Tim Walter, University of Würzburg
  • ,
  • Reinhold Tacke, University of Würzburg
  • ,
  • David G. Castner, National ESCA and Surface Analysis Center for Biomedical Problems (NESAC/BIO), Departments of Bioengineering and Chemical Engineering, University of Washington, Seattle, WA 98195, USA.
  • ,
  • Michael Zharnikov, University of Würzburg

Whereas thiols and thioethers are frequently used as binding units of oligodentate precursor molecules to fabricate self-assembled monolayers (SAMs) on coinage metal and semiconductor surfaces, their use for tridentate bonding configuration is still questionable. Against this background, novel tridentate thiol ligands, PhSi(CH(2)SH)(3) (PTT) and p-Ph-C(6)H(4)Si(CH(2)SH)(3) (BPTT), were synthesized and used as tripodal adsorbate molecules for the fabrication of SAMs on Au(111). These SAMs were characterized by X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The PTT and BPTT films were compared with the analogous systems comprised of same tripodal ligands with thioether instead of thiol binding units (anchors). XPS and NEXAFS data suggest that the binding uniformity, packing density, and molecular alignment of the thiol-based ligands in the respective SAMs is superior to their thioether counterparts. In addition, the thiol-based films showed significantly lower levels of contamination. Significantly, the quality of the PTT SAMs on Au(111) was found to be even higher than that of the films formed from the respective monodentate counterpart, benzenethiol. The results obtained allow for making some general conclusions on the specific character of molecular self-assembly in the case of tridentate ligands.

Original languageEnglish
JournalThe Journal of Physical Chemistry Part C
Pages (from-to)19609-19617
Number of pages9
Publication statusPublished - 2009
Externally publishedYes

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