Mixed self-assembled monolayers of azobenzene photoswitches with trifluoromethyl and cyano end groups |
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Authors: | Daniel Brete Daniel Przyrembel Christian Eickhoff Robert Carley Wolfgang Freyer Karsten Reuter Cornelius Gahl Martin Weinelt |
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Institution: | Freie Universit?t Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin, Germany. Max-Born-Institut, Max-Born-Stra?e 2A, 12489 Berlin, Germany. |
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Abstract: | Mixed self-assembled monolayers (SAMs) of alkanethiolates carrying azobenzene chromophores with either a trifluoromethyl or a cyano substituent have been studied. High-resolution x-ray photoelectron spectroscopy proves that the ratio of adsorbed molecules can be arbitrarily adjusted via the molar fractions in solution. As a function of these molar fractions core level shifts are observed which are attributed to local work-function changes. By simulating the electric dipole field distribution, the continuous core level shifts are ascribed to a homogeneous mixture of molecules with different end groups adsorbed on adjacent lattice sites. Near-edge x-ray absorption fine structure measurements reveal formation of well-ordered SAMs. Despite the difference in dipole moment of the end groups, the molecular tilt and twist angles are identical for both single-component SAMs and a 1:1 mixed SAM. |
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