ISSRNS 2012: Abstracts / Synchrotron Radiation in Natural Science Vol. 11, No 1 – 2 (2012) P 61
COMBINED SMALL ANGLE X-RAY SCATTERING AND X-RAY ABSORPTION SPECTROSCOPY STUDIES OF ELECTROCHROME
METALLOPOLYELECTROLYTES
W. Szczerba∗, H. Riesemeier, U. Reinholz, M. Radtke, and A.F. Th¨unemann
BAM Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205 Berlin, Germany Keywords: SAXS, XAFS, metallopolymers
∗e-mail : wojciech.szczerba@bam.de
We present the results of an ongoing study by means of synchrotron radiation based small angle x-ray scattering (SAXS) and x-ray absorp- tion fine structure (XAFS) spectroscopy of the structure and oxidation state of self-assembled metallo-supramolecular coordination polyelectro- lytes (MEPEs) [1]-[3] with Fe(II), Co(II), Ni(II) ions used as a functional material in electrochrome win- dows. The MEPEs change from opaque to transpar- ent when placed between two electrodes to which a low DC voltage is applied. Moreover, these materi- als show remarkable self-healing abilities.
For the sake of the study a modification to the small angle scattering set-up, Saxsess by Anton Paar, has been done out by mounting an energy dis- persive detector perpendicular to the beam path on top of the SAXS apparatus. This allows for simul- taneous measurements of SAXS, XRF and XAFS.
Insofar it has been found that the MEPEs have a structure of solid rods of approx 0.5 nm radius and a length of > 50 nm when in water solution. When
solved in ethanol the rods are significantly shorter.
The oxidation state of 2+ is being maintained in all samples regardless their history, i.e. thermal treat- ment, switching cycles etc. However, in NEXAFS and EXAFS, small changes occur between the tem- pered and non-tempered samples of the same series.
Acknowledgments: This work is supported by the German Federal Ministry of Education and Research (BMBF), grant No. 13N11285, Samples have been pro- vided by the SmartWin Project partners ISC Fraunhofer and Uni W¨urzburg.
References
[1] F.S. Ha et al., Thin Solid Films 516 (2008) 2469 – 2473.
[2] Y. Bodenthin et al., J. Am. Chem. Soc. 131 (2009) 2934 – 2941.
[3] F.S. Han, M. Higuchi, D.G. Kurth, J. Am. Chem.
Soc. 130 (2008) 2073 – 2081.
Figure 1 : Schematic view of the MEPEs, blue balls represent the metallic divalent ions.
Figure 2 : XANES K-edges of the MEPEs with Fe(II), Co(II) and Ni(II) ions.
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