X-ray spectroscopy characterization of self-assembled monolayers of nitrile-substituted oligo(phenylene ethynylene)s with variable chain length

Hicham Hamoudi, Ping Kao, Alexei Nefedov, David L. Allara, Michael Zharnikov

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Self-assembled monolayers (SAMs) of nitrile-substituted oligo(phenylene ethynylene) thiols (NC-OPEn) with a variable chain length n (n ranging from one to three structural units) on Au(111) were studied by synchrotron-based high-resolution X-ray photoelectron spectroscopy and near-edge absorption fine-structure spectroscopy. The experimental data suggest that the NC-OPEn molecules form well-defined SAMs on Au(111), with all the molecules bound to the substrate through the gold-thiolate anchor and the nitrile tail groups located at the SAM-ambient interface. The packing density in these SAMs was found to be close to that of alkanethiolate monolayers on Au(111), independent of the chain length. Similar behavior was found for the molecular inclination, with an average tilt angle of ~33-36° for all the target systems. In contrast, the average twist of the OPEn backbone (planar conformation) was found to depend on the molecular length, being close to 45° for the films comprising the short OPE chains and ~53.5° for the long chains. Analysis of the data suggests that the attachment of the nitrile moiety, which served as a spectroscopic marker group, to the OPEn backbone did not significantly affect the molecular orientation in the SAMs.

Original languageEnglish
Pages (from-to)12-24
Number of pages13
JournalBeilstein Journal of Nanotechnology
Volume3
Issue number1
DOIs
Publication statusPublished - 2012
Externally publishedYes

    Fingerprint

Keywords

  • Nitrile substitution
  • Oligo(phenylene ethynylene)
  • Self-assembled monolayers
  • Twist angle
  • X-ray absorption spectroscopy

ASJC Scopus subject areas

  • Materials Science(all)
  • Electrical and Electronic Engineering
  • Physics and Astronomy(all)

Cite this