Dresden 2011 – scientific programme
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O: Fachverband Oberflächenphysik
O 53: Solid / liquid interfaces III
O 53.2: Talk
Wednesday, March 16, 2011, 15:15–15:30, WIL C107
Adsorption of TMPy-porphyrin on iodine-modified Pt(100) electrodes — •Klaus Stallberg1,2 and Winfried Daum1,2 — 1Institute of Energy Research and Physical Technologies, TU Clausthal, Leibnizstr. 4, 38678 Clausthal-Zellerfeld — 2NTH School for Contacts in Nanosystems
The adsorption of free-base meso-tetra(N-methyl-4-pyridyl)porphyrin (TMPyP) cations on Pt(100)(√2×5√2)I electrode surfaces in 0.1 M HClO4 was studied in situ with STM and cyclic voltammetry (CV). To facilitate ordered porphyrin adsorption under electrochemical conditions, the Pt(100) surface was precovered with a monolayer of iodine. With a porphyrin surface coverage of 0.7 ML, ordered (5√2×5√2) superstructures were observed only on parts of the surface indicating a high mobility of the adsorbed molecules. Ordered porphyrin structures were preferentially detected on defect-free terraces but not at the line defects of specifically structured iodine adlayers [1]. The characterization of TMPyP adsorption by means of their pronounced redox current peaks in CV turned out to be complicated: CV experiments performed with porphyrin adlayers adsorbed under different experimental conditions suggest that initially adsorbed molecules may have a low ’redox activity’ which increases in time. A possible relation of the increase of this activity with a protonation of TMPyP in acidic electrolytes will be discussed.
[1] B. Braunschweig et al., Surf. Sci. 603 (2009) 3361