Self-Assembly of Organic Monolayers onto Hydrogen-Terminated Silicon: 1-Alkynes Are Better Than 1-Alkenes

L.M.W. Scheres, M. Giesbers, H. Zuilhof

Research output: Contribution to journalArticleAcademicpeer-review

65 Citations (Scopus)

Abstract

Recently, a new method for the preparation of high-quality organic monolayers with 1-alkynes at room temperature in the dark (i.e., without any external activation) was reported. To pinpoint the precise origin of this self-assembly process and to compare the reactivity of 1-alkenes and 1-alkynes toward hydrogen-terminated Si(111) [H-Si(111)], we followed the gradual formation of both monolayers at room temperature by static water contact angle measurements. Subsequently, attenuated total reflection infrared spectroscopy (ATR-IR) and X-ray photoelectron spectroscopy (XPS) were used to obtain detailed information about the structure and quality of the resulting monolayers. Our data clearly demonstrate that 1-alkynes are considerably more reactive toward H-Si(111) than 1-alkenes. 1-Alkynes are able to self-assemble into densely packed hydrophobic monolayers without any external activation (i.e., at room temperature under ambient light and even in the dark) whereas for 1-alkenes under the same conditions hardly any reactivity toward H-Si(111) was observed. The self-assembly of 1-alkynes on H-Si(111) at room temperature is explained by three factors: the higher nucleophilicity of 1-alkynes, which results in a facile attack at the electron-hole pairs at the H-Si surface and easy Si-C bond formation, the stabilization of the ß radical by delocalization over the double bond, and the lower-energy barrier encountered for H abstractions
Original languageEnglish
Pages (from-to)10924-10929
JournalLangmuir
Volume26
Issue number13
DOIs
Publication statusPublished - 2010

Keywords

  • covalently attached monolayers
  • metal-semiconductor diodes
  • extremely mild attachment
  • alkyl monolayers
  • si(111) surface
  • visible-light
  • molecular electronics
  • thermal-reactions
  • si
  • alkenes

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