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O: Fachverband Oberflächenphysik

O 59: Poster Session III (Nanotribology; Polymeric biomolecular films; Organic electronics and photovoltaics, Covalent networks on surfaces; Phase transitions; Particles and clusters; Transparent conductive oxides)

O 59.11: Poster

Mittwoch, 16. März 2011, 17:30–21:00, P3

Adsorption Calorimetry of Conjugated Organic Molecules on Metal Surfaces — •Ole Lytken, Hans-Jörg Drescher, Fabian Bebensee, Hans-Peter Steinrück, and J. Michael Gottfried — Universität Erlangen-Nürnberg, Lehrstuhl für Physikalische Chemie II

Traditional experimental methods for determining adsorption energies, such as temperature programmed desorption (TPD) and equilibrium adsorption isotherms, rely on desorption. However, on many metal surfaces large conjugated organic molecules, such as PTCDA and pentacene, decompose at elevated temperatures before or simultaneously with desorption. Discussions about relative bond strengths are, therefore, typically based on indirect arguments, such as the height of the adsorbed species above the surface as measured with normal incidence X-ray standing waves (NIXSW) or chemical shifts in spectroscopic techniques such as X-ray photoelectron spectroscopy (XPS). Unlike the more traditional methods, nanojoule adsorption calorimetry does not require desorption of the molecules; instead, the heat of adsorption is measured directly as an adsorption-induced temperature change of the sample. We will describe the construction of such a calorimeter at the Universität Erlangen-Nürnberg. Support from the Alexander von Humboldt Foundation is gratefully acknowledged.