Dresden 2006 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 6: Solids At Low Temperature: Amorphous and Tunnel Systems, Glasses, ...
TT 6.7: Vortrag
Montag, 27. März 2006, 12:15–12:30, HSZ 105
Properties of transition-metal nanoclusters on biological substrates — •T. Herrmannsdörfer1, A. D. Bianchi1, T. P. Papageorgiou1, F. Pobell1, J. Wosnitza1, S. Selenska-Pobell2, K. Pollmann2, M. Merroun2, and J. Raff2 — 1Institut Hochfeld-Magnetlabor Dresden (HLD) and — 2Institut für Radiochemie, Forschungszentrum Rossendorf, P.O.-Box 51 01 19, D-01314 Dresden, Germany
Micro- and nanogranular materials can reveal strongly altered properties compared to their bulk counterparts. In particular, their magnetic and superconducting behaviour can be drastically changed. We have investigated transition-metal clusters with a well defined size of 1 to 1.5nm which are isolated and separated from each other. These metal nanoclusters have been deposited on a regular square lattice of a biological template. In more detail, this template is a purified self-assembling paracrystalline surface layer (S-layer) of Bacillus sphaericus JG-A12 which exhibits square symmetry and is composed of identical protein monomers. These S-layer proteins are capable of selective and reversible binding of high amounts of metals, making the metallic nanocluster covered S-layer also interesting for technological applications. The transition-metal nanoclusters were investigated using EXAFS spectroscopy and SQUID magnetometry. The magnetization of Pd and Pt nanoclusters at 0 ≤ B ≤ 7 T and 1.8 K ≤ T ≤ 350 K reveal interesting magnetic properties. The Stoner enhancement factor of the d conduction-electron susceptibility of the nanoclusters is clearly reduced compared to the one of the bulk transition metals.