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

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• 作者：Tobias Weidner ; Nirmalya Ballav ; Ulrich Siemeling ; Dennis Troegel ; Tim Walter ; Reinhold Tacke ; David G. Castner ; Michael Zharnikov
• 刊名：Journal of Physical Chemistry C
• 出版年：2009
• 出版时间：November 12, 2009
• 年：2009
• 卷：113
• 期：45
• 页码：19609-19617
• 全文大小：215K
• 年卷期：v.113,no.45(November 12, 2009)
• ISSN：1932-7455

文摘

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(CH₂SH)₃ (PTT) and p-Ph−C₆H₄Si(CH₂SH)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 to the analogous systems comprised of the 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 are 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.