Paper NS+BI-MoA10
Relative Stability of Aromatic Self-Assembled Monolayers Formed by Thiols and Selenols

Monday, November 9, 2009, 5:00 pm, Room L

Aromatic self-assembled monolayers (SAMs) are considered a model system for molecular electronics applications.¹ However, potential use of these monolayers in real devices is limited by significant concentration of structural defects,² which disturb functions of the metal-molecule-metal junction. One of strategies we propose to optimize structure of aromatic SAM’s is selection of proper headgroup atom binding SAMs to the substrate.^3,4

In this presentation we report on stability of two analogous aromatic SAMs bound to the Au(111) substrate by S or Se atom. To compare stability of both systems we analyze exchange of molecules constituting complete SAM monolayer during incubation in solution containing other aliphatic thiol or aliphatic selenol molecules.⁵ The exchange experiments have been performed by comparing not just a single SAM but two entire homologue series of BPnS (CH₃-(C₆H₄)₂-(CH₂)_n-S-, n = 2-6) and BPnSe (CH₃-(C₆H₄)₂-(CH₂)_n-Se-, n =2-6) molecules on Au(111) surface. Quantitative control of the exchange process was obtained using Infrared Reflection Adsorption Spectroscopy. These data will be discussed together with our recent microscopic study which found that binding by selenium atoms improve significantly the ordering of these SAMs and influences molecule-substrate interaction.⁴ Obtained results clearly indicate higher stability of SAMs based on selenols in comparison to their thiol analogs.

References

[1] C. Love , G. et al. 2005, Chem. Rev., 105, 1103.

[2] D. Käfer et al.. 2006 J. Am.Chem. Soc. 128, 1723.

[3] A. Shaporenko, et al. 2005 J. Phys. Chem. B 109, 13630.

[4] P. Cyganik et al. 2008 J. Phys. Chem. C 112, 15466.

[5] K. Szelagowska-Kunstman, P. Cyganik, B Schüpbach, A. Terfort 2009 in preparation