AVS 49th International Symposium
    Surface Science Friday Sessions
       Session SS-FrM

Paper SS-FrM1
Structure of Nitrile-functionalized Alkanethiolate Monolayers on Gold and Silver

Friday, November 8, 2002, 8:20 am, Room C-110

Session: Self-Assembly at Surfaces
Presenter: A. Shaporenko, Universität Heidelberg, Germany
Authors: A. Shaporenko, Universität Heidelberg, Germany
S. Frey, Universität Heidelberg, Germany
Ph. Harder, Pennsylvania State University
D.L. Allara, Pennsylvania State University
M. Zharnikov, Universität Heidelberg, Germany
M. Grunze, Universität Heidelberg, Germany
Correspondent: Click to Email
Self-assembled monolayers (SAMs) formed from nitrile-functionalized alkanethiols (AT) are perspective candidates for SAM-based lithography and the fabrication of surfaces with low protein affinity. In addition, the polar nitrile group with a relatively large dipole moment is well-suitable to explore to what extent the structure of a non-substituted AT SAM can be affected by strongly interacting tail groups. We used several complementary experimental techniques, such as X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy at the C1s and N1s absorption edges to get an information on the chemical identity, packing density, and orientational order in SAMs formed from CN(CH@sub 2@)@sub 16@SH (CN-C16) on (111) gold and silver substrates. The results imply that the substitution of the weakly interacting methyl groups by the nitrile entities has a strong influence on the molecular orientation, packing, and the structure of AT SAMs on both gold and silver. A strong dipole-dipole interaction between the polar nitrile groups is assumed to disturb a balance between the headgroup-substrate and interchain interactions, which is responsible for the SAM structure and packing density. In contrast to the methyl-functionalized AT SAMs, only a slight difference in the orientation of the alkyl chains in CN-C16/Au and CN-C16/Ag is observed. The nitrile groups in both CN-C16/Au and CN-C16/Ag are oriented almost parallel to the film surface, which is beneficial to minimize the dipole-dipole interaction between these moieties, but different from the "standard" orientation of the functional groups in @omega@-functionalized AT SAMs of the same chain length.