Hamburg 2001 – wissenschaftliches Programm
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M: Metallphysik
M 33: Postersitzung
M 33.31: Poster
Donnerstag, 29. März 2001, 15:15–19:00, Foyer S4, CCH
Preparation and characterization of metal nanoparticle coatings on oxide nanospheres — •P. -T. Miclea1,2, K. Lehrack3, H. Drevs3, W. Mörke2, and H. Hofmeister1 — 1MPI Halle — 2Fachber. Chemie, Universität Halle — 3Fachhochschule Merseburg
The optical properties of metal nanoparticles depend, besides on size and shape, rather sensitively on their surrounding, e.g., a dielectric medium, as well as on their arrangement. Novel optical effects are expected by appropriately combining matrix material and specific ways of particle arrangement, such as core-shell structures. For a low temperature route to core-shell structures we explored prenucleation by direct reduction of organometallic complexes of the type [Li(THF)2]2·[MR4] on oxide surfaces of well defined hydroxyl concentration. The metal particle precursors achieved this way enable further nanoparticle coating via complementary processes to form continuous metal nanoshells. This procedure has been applied to achieve Pt and Pd nanoparticle coatings on SiO2 and TiO2 nanospheres of various sizes and distributions. Transmission electron microscopy, magnetic resonance spectroscopy and optical absorbance measurements in the visible range were used for structural characterisation of these materials. >From electron micrographs the size distribution and coverage of metal nanoparticle coatings on oxide nanospheres as well as the corresponding dispersion of metal on oxide surface was evaluated. Upon annealing at 100 ∘C we obtain 9.1 % coverage of SiO2 nanospheres (∼40 nm mean size) by Pt particles of 2.2 nm. Magnetic resonance measurements of the Pt samples exhibit conduction electron spin resonance signals characteristic of rather small particles.