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O: Fachverband Oberflächenphysik

O 12: Organic Molecules at Surfaces 2: Characterization of Organic Monolayers

O 12.12: Vortrag

Montag, 5. September 2022, 17:45–18:00, S051

Accurate determination of adsorption-energy differences of metalloporphyrins on TiO2(110) 1x1 — •Maximilian Muth, Alexander Wolfram, Elmar Kataev, Julia Köbl, Hans-Peter Steinrück, and Ole Lytken — Univ. Erlangen-Nürnberg

A deeper knowledge of the behavior between porphyrin molecules and the rutile TiO2(110) surface and is of crucial importance for the development of new applications. Especially the usage of such systems in photocatalysis or solar cells are promising possibilities. Therefore, we investigated the adsorption energy of three different metallo-tetraphenylporphyrins (MTPP M = Mg, Co, Zn). Unfortunately, temperature programmed desorption, a typical method for the determination of adsorption energies is not applicable for this particular system because of the irreversible adsorption of the monolayer in direct contact to the TiO2-surface. For this reason, instead, we compared the adsorption-energy of the three MTPPs relatively to each other by using a layer exchange experiment. We adsorb mixtures of always two different MTPPs on top of each other and allow the molecules to diffuse during a heating ramp. Eventually, an equilibrium state forms in which the MTPP with the higher adsorption-energy will enrich in the monolayer in direct contact with surface while the weaker adsorbing MTPP will be enriched in the multilayer. After further heating for multilayer desorption we determine the concentrations of the MTPPs found in the remaining monolayer by using XPS and use them to calculate the difference in adsorption-energy of MTPPs via the equilibrium constant.