Porphyrins at solid-liquid interfaces: EC-STM and CV investigations

Title : Porphyrins at solid-liquid interfaces: EC-STM and CV investigations

Abstract:

In situ and in operando electrochemical scanning tunnelling microscopy (EC-STM) and cyclic voltammetry (CV) [1,2,3,4] were used to investigate the self-assembly of TTMAPP (5,10,15,20-Tetrakis(4-trimethylammoniophenyl) porphyrin tetra(p-toluenesulfonate)) molecules on bare and iodine precovered Au (100) [5,6]. The potentiostatic, potentiodynamic, and quasi-spectroscopic modes of EC-STM operation were applied. A number of the electrode potential dependent porphyrin structures was found, which were characterized by the transformation matrixes. In all identified structures porphyrins exhibit the planar orientation. TTMAPP molecules adsorbed on the bare Au (100) - (1×1) surface hinder the adsorption of iodine, while adsorbed on the iodine precovered Au (100) surface hinder the desorption of iodine from the substrate. The readsorption of iodine on the TTMAPP precovered Au (100) surface depends on the scan rate of the electrode potential. This indicates the noncovalent interactions between the adsorbed molecules and the Au (100) electrode surface, which govern the self-assembly process of TTMAPP and resulting structural phases. Different adsorption sites are responsible for the variation of the adsorption energy, chemical state, and electron transfer for porphyrin molecules on Au (100), which lead to the desorption of the respective molecules at different potentials upon the first reduction of TTMAPP. The comparison of the obtained results is discussed in the context of the coadsorption of TMPyP (tetra(N-methyl-4-pyridyl)-porphyrin), sulfate anions, and copper on Au (111) [7].

Biography:

Prof. Dr. Marek Nowicki studied Physics at the University of Wroclaw, Poland and graduated as MS in 1992. He joined the group of Prof. S. Mroz at the Institute of Experimental Physics of the University of Wroclaw. He received his PhD in 1996 at the same institution. From 1998 till 2002 he worked as an Alexander von Humboldt Fellow and postdoc at Forschungszentrum Julich GmbH, Germany (Prof. H.P. Bonzel). Then he joined the Department of Chemical Physics of the FHI-MPG in Berlin, Germany (prof. H.J. Freund). In 2006 he received habilitation and in 2016 professorship at the University of Wroclaw.