Regensburg 2016 – scientific programme

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O: Fachverband Oberflächenphysik

O 85: Organic-Inorganic Systems IV: Electronic Structure

O 85.11: Talk

Thursday, March 10, 2016, 17:45–18:00, S051

Reversible photo-switching of spiropyran molecules in direct contact with a single crystal — •Fabian Nickel, Matthias Bernien, Kai Kraffert, Dennis Krüger, Lucas M. Arruda, Lalminthang Kipgen, and Wolfgang Kuch — Institut für Experimentalphysik, Freie Universität Berlin, 14195 Berlin, Germany

The photochromic isomerization of molecules in direct contact with solid surfaces plays an important role for the further miniaturization of electronic devices. A good candidate for this purpose is spiropyran (SP). SP can be switched from a closed form to an open form (merocyanine, MC) by UV light and reversibly back by visible light. In nitro-spiropyran, however, the backreaction was found to be quenched on surfaces [1]. The modification of the end group from nitro- to naphtho-spiropyran leads to a lower electric dipole moment in the open form, which might favor switching back to the open form on a surface. In-situ x-ray absorption fine structure (NEXAFS) measurements at the nitrogen and oxygen edges prove and quantify the photoisomerization of these molecules on a Bi(111) surface. Illumination by UV light leads to an efficient switching to the open MC form of the molecule and, furthermore, a determination of the energy barriers of the photo-excited and metastable states becomes possible by temperature-dependent measurements. Visible light triggers the relaxation back to the closed SP form, thus offering full reversible control of the isomerization in direct contact with a single crystal surface.

This work is supported by the DFG through Sfb 658.

[1] Piantek et al. J. Am. Chem. Soc. 131, 12729 (2009).