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Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P273
Structure of silver nanoparticles in glasses and of nanoparticles-glass interfaces
characterized by EXAFS
Manfred Dubiel 1 , Reinhard Schneider 1 , Jörg Haug 1 , Herbert Hofmeister 2 ,
Klaus-Dieter Schicke 2
1 Martin Luther University of Halle-Wittenberg, Department of Physics, Friedemann-
Bach-Platz 6, D-06108 Halle, Germany – 2 Max Planck Institute of Microstructure
Physics, Weinberg 2, D-06120 Halle, Germany
Silver nanoparticles of 1.5 - 7 nm mean size formed in soda-lime glass by a combination
of ion exchange and thermal processing have been studied using extended X-ray absorption
spectroscopy (EXAFS) and high-resolution transmission electron microscopy
to explore the structural characteristica of these nanoparticles and their interface to
the glass matrix. The lattice parameters of particles show a slight lattice dilatation
as well as a distinct size-dependent contraction that depends on the amount of iron
oxide in the glasses. Temperature-dependent EXAFS spectra (10 K to 300 K) at the
Ag K-edge evaluated on the basis of an anharmonic Einstein model indicate an increasing
thermal expansion coefficient for Ag nanoparticles with decreasing size. By
combination of dilatometric data of the matrix and EXAFS parameters of embedded
nanoparticles their state of stress can be qualitatively explained.
Averaged Ag-Ag coordination numbers derived from the respective particle sizes are
used, together with the known Ag-O coordination number of matrix silver ions, to
model the EXAFS-based coordination numbers of Ag species in the glass samples.
With that a structural model of the particle-glass interface has been developed under
the assumption of Ag-Ag interactions across the interface.