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SYSA: Symposium Tayloring Organic Interfaces: Molecular Structures and Applications

SYSA 5: Poster Session SYSA

SYSA 5.60: Poster

Dienstag, 26. Februar 2008, 14:30–20:00, Poster A

A new tool for gradual tuning the composition of binary self-assembled monolayers and chemical lithography: UV-promoted exchange reaction — •Nirmalya Ballav, Tobias Weidner, and Michael Zharnikov — Angewandte Physikalische Chemie, Universität Heidelberg, 69120 Heidelberg, Germany

We demonstrate that exchange reaction between a primary self-assembled monolayer (SAM) and a potential molecular substituent, capable to form SAM on the same substrate can be promoted in a controlled way by preliminary exposure of the SAM to UV light with a suitable wavelength. Using a model system of a non-substituted alkanethiolate (AT) SAM as the primary film and COOH-substituted AT as the substituent, we showed that the composition of the binary mixed film formed by the UV promoted exchange reaction (UVPER) can be precisely varied and tuned over the entire concentration range by the selection of a proper UV exposure time. The reason for the promotion effect of the UV light treatment is the appearance of chemical and structural defects in the primary film, viz. photooxidation of the thiolate tailgroups and the structural and chemical defects in the aliphatic matrix. Since both these defects are stochastically distributed over the target film, no phase separation occurs, and the resulting mixed SAM represents a true molecular mixture of both components. Apart from its usefulness for the preparation of mixed SAMs, the UVPER approach can be combined with lithography and applied for the fabrication of chemical patterns and molecular templates.