Adsorption geometry of carboxylic acid functionalized porphyrin molecules on TiO2(110)

Fernández CC, Wechsler D, Rocha TC, Steinrück HP, Lytken O, Williams FJ (2019)

Publication Type: Journal article

Publication year: 2019

Journal

Surface Science Elsevier

Book Volume: 689

Article Number: 121462

DOI: 10.1016/j.susc.2019.121462

Abstract

Controlling the adsorption geometry of porphyrin molecules on titania surfaces is an important step in the rational design of molecular devices such as dye-sensitized solar cells. We employed X-ray Photoelectron Spectroscopy (XPS) and Near-Edge X-Ray-Absorption Fine Structure (NEXAFS) spectroscopy to determine the binding mode, the electronic structure and the adsorption geometry of carboxylic acid functionalized tetraphenylporphyrin molecules. Molecules with one (mono), two (cis and trans) and four (tetra) carboxylic acid anchoring groups were adsorbed on rutile TiO2(110). XPS shows that the iminic nitrogen atoms at the macrocycle center are partially protonated after adsorption, and that the degree of protonation increases with the number of –COOH functional groups in the molecule. NEXAFS measurements show that molecules with either one or two groups in cis configuration adsorb with the macrocycle tilted away from the surface. In contrast, molecules with two carboxylic-acid groups in trans configuration adsorb with what is probably a flat-lying, but distorted macrocycle. Finally, molecules with four carboxylic-acid groups show no linear dichroism, indicating an intermediate adsorption angle. Our results show how the number and position of the –COOH functional groups determine the molecular adsorption geometry.

Authors with CRIS profile

Daniel Wechsler Lehrstuhl für Physikalische Chemie II Hans-Peter Steinrück Lehrstuhl für Physikalische Chemie II Ole Lytken Lehrstuhl für Physikalische Chemie II

Involved external institutions

Universidad de Buenos Aires (UBA) / University of Buenos Aires AR Argentina (AR) Centro Nacional de Pesquisa em Energia e Materiais (CNPEM) BR Brazil (BR)

How to cite

APA:

Fernández, C.C., Wechsler, D., Rocha, T.C., Steinrück, H.-P., Lytken, O., & Williams, F.J. (2019). Adsorption geometry of carboxylic acid functionalized porphyrin molecules on TiO2(110). Surface Science, 689. https://doi.org/10.1016/j.susc.2019.121462

MLA:

Fernández, Cynthia C., et al. "Adsorption geometry of carboxylic acid functionalized porphyrin molecules on TiO2(110)." Surface Science 689 (2019).

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