Invited Paper SS2-MoA6
Redox Activity and Structural Transitions at Electrochemical Interfaces

Monday, October 31, 2011, 3:40 pm, Room 110

Ordered layers of organic molecules play an increasing role in modern material science. Their electrochemical deposition from solution has several important advantages: i) Thermally unstable organic molecules which are not intact volatile may be deposited under mild conditions, ii) unlike vacuum deposition electrochemical adsorption may be performed near equlibrium, and iii) the electrochemical potential is an extra parameter which enables a controlled switching of the redox-state of the adsorbed molecules and, thereby, structural transitions of the layers. This lecture concentrates on the correlation between redox-activity and structural properties of viologen and porphyrin layers at metal – electrolyte interfaces. The selfassembly of the molecules is studied as a function of i) the nature and symmetry of the substrate (Cu(111), Cu(100), Au(111) and Cu/Au(111)), ii) the nature of the accompanying counter ions (Cl, Br, I, SO₄), iii) the concentration of the solution, and, most importantly, iv) the potential dependent redox state of the adsorbed molecules, by using in-situ ElectroChemical Scanning Tunneling Microscopy (EC-STM), in-situ Infrared Reflection Absorption Spectroscopy (IRRAS) as well as ex-situ Synchrotron X- ray Photoelectron Spectroscopy (SXPS) after air- and contamination-free transfer from the solution into the UHV analysis chamber. The lecture not only provides a deep insight into the properties of the investigated model systems but also demonstrates the status of modern electrochemical surface science.