Paper NS+NC-ThM1
Confinement of Electrochemical Metal Deposition on the Nanometer Scale by a Hydrogen-Bonded Network/SAM Hybrid Structure

Thursday, October 23, 2008, 8:00 am, Room 311

The combination of supramolecular networks with thiol-based self-assembled monolayers (SAMs) offers interesting opportunities as the flexibility in surface functionalisation afforded by SAMs can be carried to an unprecedented level of precision. The scope for nanotechnological applications broadens even further by processing these hybrid systems in an electrochemical environment. Recently we have shown that an extended bimolecular network on Au(111) with a periodicity of 3.5 nm can be prepared from a solution of perylene-3,4,9,10-tetracarboxylic di-imide (PTCDI) and 1,3,5-triazine-2,4,6-triamine (melamine) and that this open hexagonal structure is sufficiently robust to act as template for thiol adsorption.¹ Proper control of the preparation parameters allows filling of the network pores without altering the framework. This leads to patterned self-assembled monolayers that reflect the periodicity and symmetry of the network with islands of thiol molecules kept apart by the PTCDI-melamine backbone. This hybrid structure can then be used as nanoscaled template for the electrodeposition of metal. Using scanning tunneling microscopy the underpotential deposition (UPD) of Cu was investigated where a monolayer of Cu is intercalated at the molecule-substrate interface. In contrast to continuous thiol SAMs where Cu UPD originates at major defects in the SAM and spreads by interfacial diffusion,² the hybrid structure acts as a barrier against interfacial diffusion and, thus, confines metal electrodeposition to the thiol-filled cells.¹ As a result a regular pattern forms where metal UPD islands are separated by the PTCDI-melamine framework.

¹ Madueño, R.; Räisänen, M.; Silien, C.; Buck, M. Nature 2008 (in print).
² Silien, C.; Buck, M. J. Phys. Chem. C 2008, 112, 3881-3890.