Dresden 2006 – wissenschaftliches Programm

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O: Oberflächenphysik

O 29: Poster session II (Nanostructures, Magnetism, Particles and clusters, Scanning probe techniques, Time-resolved spectroscopy, Structure and dynamics, Semiconductor surfaces and interfaces, Oxides and insulators, Solid-liquid interfaces)

O 29.81: Poster

Mittwoch, 29. März 2006, 14:30–17:30, P2

Immobilization of cationic porphyrins (H2TMPyP) on sulfate modified Cu(111): An ECSTM study — •Minh Hai Nguyen Thi, Klaus Wandelt, and Peter Broekmann — Institut für Physikalische und Theoretische Chemie, Universität Bonn, Wegelerst. 12, D-53115 Bonn, Germany

The immobilization of cationic porphyrins (Meso-Tetra (N-methyl-4-pyridyl) Porphyrine Tetratosylat (H2TMPyP)) on sulfate modified Cu(111) surface has been studied by means of Cyclic Voltammetry (CV) and in-situ Scanning Tunnelling Microscopy (STM). Therefore a Cu(111) electrode surface was exposed to dilute sulfuric acid (5 mM H2SO4). Sweeping the electrode potential into the anodic direction starting from the regime of hydrogen evolution initiates the adsorption and subsequent ordering of a hydrophilic sulfate/water coadsorption layer. This adlayer formation follows a nucleation and growth mechanism so that even submonolayer coverages of this sulfate/water can be obtained depending on the applied electrode potential. Adsorption and immobilization of the cationic porphyrins takes place exclusively on the negatively charged sulfate/water coadsorption layer but not on the bare sulfate-free copper surface. This preferential adsorption is explained in terms of enhanced electrostatic interactions between the anion/water layer on the one hand and the cationic porphyrins layer on the other hand.