Molecular orientation of thiol-derivatized tetraphenylporphyrin on gold studied by XPS and NEXAFS
2009 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 603, no 7, 1026-1033 p.Article in journal (Refereed) Published
Tetraphenylporphyrins bearing four linkers consisting of thioacetyl-functionalized carbon chains were immobilized on a gold surface via thiolate-gold bonds using two different preparation routes. The structure of these molecular layers was characterized in detail with synchrotron radiation based core-level spectroscopy, X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The results show that the geometry of the molecular layers and the number of linkers that bind to the gold surface depends on the preparation schemes. The deprotection of the linkers through removal of the terminal acetyl group before the molecular adsorption (deprotected systems) resulted in porphyrins bound to the gold surface with on the average three linkers, their normal axis being tilted similar to 38 degrees with respect to the surface normal. On the other hand, porphyrin layers prepared directly with the acetyl group still in place on the linkers (protected systems) are made of molecules bound to the gold surface via two linkers on the average. The resulting orientation is more upright, with the normal axis of the porphyrin plane tilted similar to 50 degrees with respect to the surface normal. Moreover, NEXAFS measurements revealed that the acetyl deprotected porphyrin layers have a higher degree of ordering than the protected systems. (C) 2009 Elsevier B.V. All rights reserved.
Place, publisher, year, edition, pages
2009. Vol. 603, no 7, 1026-1033 p.
Porphyrin, Thiol, Monolayer, X-ray photoelectron spectroscopy, Near-edge X-ray absorption fine structure spectroscopy (NEXAFS), Gold surface, Molecular orientation
IdentifiersURN: urn:nbn:se:uu:diva-129099DOI: 10.1016/j.susc.2009.02.022ISI: 000265310000011OAI: oai:DiVA.org:uu-129099DiVA: diva2:337578