Berlin 2001 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 18: Poster: Polymer Blends, Heterogeneous Systems, Colloids and Nanoparticles, Interfaces, Polyelectrolytes
CPP 18.18: Poster
Mittwoch, 4. April 2001, 12:30–15:00, AT1
Conduction electron spin resonance study of Rh and Ir nanoparticles on hydride modified silica — •P.-T. Miclea1,2, K. Lehrak3, H. Drevs3, H. Hofmeister2, and W. Mörke1 — 1Fachbereich Chemie, Universität Halle — 2Max-Planck-Institut Halle — 3Fachhochschule Merseburg
The preparation of highly dispersed metal nanoparticles by low temperature reduction of metal complexes on hydride modified silica is investigated. Magnetic resonance measurement are used to follow the initial stage of particle formation and anchoring as well as oxide surface modification by this process. Size, shape and structure of metal particles are characterized using conventional and high resolution electron microscopy. By varying the preparation conditions like metal complex concentration and thermal treatment temperature we aimed at high metal dispersion and anchoring strength. Immediately after reduction Rh samples exhibited MII and M0 species besides some defects (E’ centers) induced by LiAlH4 treatment of the silica. Additional signals in the magnetic resonance spectra indicate the presence of organic residues, even upon 100 ∘C thermal treatment. These signals, together with those of MII, disappeared after several months storage of the samples. The Ir sample exhibit MI species and did not show paramagnetic behaviour as long as no thermal treatment at 400 ∘C resulted in M0 species. The calculation of particle mean size from conduction electron spin resonance signals yields 1.5-2.5 nm in agreement with size evaluation by electron microscopy.