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

Authors :
Hicham Hamoudi
Ping Kao
Alexei Nefedov
David L. Allara
Michael Zharnikov
Source :
Beilstein Journal of Nanotechnology, Vol 3, Iss 1, Pp 12-24 (2012)
Publication Year :
2012
Publisher :
Beilstein-Institut, 2012.

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.

Details

Language :
English
ISSN :
21904286
Volume :
3
Issue :
1
Database :
Directory of Open Access Journals
Journal :
Beilstein Journal of Nanotechnology
Publication Type :
Academic Journal
Accession number :
edsdoj.b6f1723aec842879a3e6f93fd41af3e
Document Type :
article
Full Text :
https://doi.org/10.3762/bjnano.3.2