Dresden 2009 – scientific programme

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O: Fachverband Oberflächenphysik

O 37: Metal substrates: Adsorption of organic / bio molecules V

O 37.9: Talk

Wednesday, March 25, 2009, 17:00–17:15, SCH A118

Influence of water on the structure of SAMs formed by mercaptopyridine and aminothiophenol on Au(111): a DFT study — •Jan Kučera and Axel Groß — Institut für Theoretische Chemie, Universität Ulm, D-89069 Ulm, Germany

Self-assembled monolayers (SAMs) of nitrogen containing aromatic thiolates on gold have been proposed as a fundamental element for nano-electronic devices. The formation of aromatic SAMs as well as the preparation of metal-SAM-metal contacts [1] usually occur in an aequous environment. However, theoretical studies addressing the structure and stability of SAMs typically neglect the influence of the solvent. Hence the detailed influence of the aequous environment on the geometric and electronic structure of SAMs remains unclear.

We have studied the effects of water on the structural and electronic properties of Au(111)/mercaptopyridine (MPy) and Au(111)/aminothiophenol (ATP) complexes by means of density functional theory calculations. The interaction of water with both the nitrogen- as well as with the sulfur-tail of MPy and ATP on Au(111) were examined. Water binds to the N-tails of SAM/Au complexes via the formation of hydrogen bonds [2], but its interaction with the S-tail is rather weak. The overall effect of water on the binding of the SAMs to the Au substrate is negligible, however, this is significantly changed when ions bound to the SAMs are considered.

[1] Mila Manolova et al., Adv. Mater., doi:10.1002/adma.200801634, in press.

[2] J. Kučera, A. Groß, Langmuir, doi:10.1021/la802368j, in press.