A spectroscopic study of self-assembled monolayer of porphyrin-functionalized oligo(phenyleneethynylene)s on gold: the influence of the anchor moiety
Artikel i vetenskaplig tidskrift, 2008

Porphyrin-functionalized oligo(phenyleneethynylene)s (OPE) are promising molecules for molecular electronics applications. Three such molecules (1-3) with the common structure P-OPE-AG (P and AG are a porphyrin and anchor group, respectively) and different anchor groups, viz. an acetyl protected thiol, -S-COCH 3 (1), an acetyl protected thiol with methylene linker, -CH 2 -S-COCH 3 (2), and a trimethylsilylethynyl group, -C≡C-Si(CH 3 ) 3 (3) have been synthesized and the corresponding self-assembled monolayers (SAMs) on Au(111) substrates have been prepared. The integrity and structural properties of these films were studied by X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy. The results suggest that the films formed from 1 have a high orientational order with an almost upright orientation and dense packing of the molecular constituents, i.e. represent a high quality SAM. In contrast, molecule 2 formed disordered molecular layers on Au, even though the molecule-surface bonding (thiolate) is the same as in the case of molecule 1. This suggests that the methylene linker in molecule 2 has a strong impact on the quality of the resulting film, so that a well-ordered SAM cannot be formed. The silane system, 3, is also able to bind to the gold surface but the resulting SAM has a poor quality, being significantly disordered and/or comprised of strongly inclined molecules. The above results suggest that the nature of the anchor group along with a possible linker is an important parameter which, to a high extent, predetermines the entire quality of OPE-based molecular layers.


S. Watcharinyanon

Karlstads universitet

Daniel Nilsson

Chalmers University of Technology

E. Moons

Karlstads universitet

A. Shaporenko

Universitat Heidelberg

M. Zharnikov

Universitat Heidelberg

Bo Albinsson

Chalmers, Kemi- och bioteknik, Fysikalisk kemi

Jerker Mårtensson

Chalmers, Kemi- och bioteknik, Organisk kemi

L. S. O. Johansson

Karlstads universitet

Physical Chemistry Chemical Physics

1463-9076 (ISSN) 1463-9084 (eISSN)

Vol. 10 5264-5275