Molecule-Oxide Bond Formation

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The knowledge-based design of organic/oxide interfaces requires detailed insights into molecule-oxide bond formation. In close collaboration with its funCOS partner projects, funCOS 3 aims at providing this information, by combining two complementary surface spectroscopies, namely vibrational spectroscopy (infrared reflection absorption spectroscopy) and photoelectron spectroscopy (X-ray photoelectron spectroscopy using also synchrotron radiation, near edge X-ray absorption fine structure), in combination with other methods. Starting from studies in ultrahigh vacuum (UHV), we will bridge the gap between ideal and real conditions by exploring anchoring reactions at ambient pressure and in liquid environments (diffuse reflectance infrared Fourier transform spectroscopy, polarization-modulation IRAS, near ambient pressure XPS, electrochemical infrared reflection absorption spectroscopy). In addition, we will directly couple UHV experiments to reactivity studies and spectroscopy performed in liquid environments. The key information provided by funCOS 3 comprises reaction mechanisms, bonding geometries, the energetics, the kinetics, and the reversibility of bond formation. In the first funding period, we explored the fundamental aspects of molecular anchoring, using simple model surfaces, small test molecules, and simple porphyrin derivatives. Building on this foundation, the project will now take the next step and explore complex molecules, nanostructures surfaces, and realistic environments. We will shift our attention from MgO(100) towards the more complex cases of cobalt oxide (Co3O4, CoO) and titanium dioxide (TiO2), ideal test cases to explore molecular anchoring from UHV to liquid environments. Specifically, we will target five key challenges: (1) We will transfer knowledge and methods from small test molecules to functionalized porphyrin derivatives. Using our expertise with carboxylate anchors, we will tune substitution patterns, use multiple anchoring or employ chelating anchors to control the molecular orientation, the formation kinetics, and the stability. (2) We will explore the role of water in molecular anchoring. Starting from UHV studies to identify protons and OH groups in the anchored film, we will investigate the influence of H2O on bond formation and, finally, link these studies to spectroscopy at ambient pressure and in liquid environments. (3) Based on our comprehensive work on carboxylate anchors, we will explore alternative anchors to tune molecule-surface interactions (phosphonic acid, hydroxamic acid, hydroxyl, catechol). (4) We will explore concepts to tune intermolecular and molecule-surface interactions independently by substitution and metalation (by aromatic and steric interactions, polar groups, H bonds, metal coordination). (5) Finally, we will use this knowledge to explore selective anchoring to nanostructured oxides, e.g. by employing selective interactions of anchors with specific surface structures.