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Galvanic Exchange in Colloidal Metal/Metal-Oxide Core/Shell Nanocrystals

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journal contribution
posted on 15.08.2016, 00:00 by Dominik Kriegner, Mykhailo Sytnyk, Heiko Groiss, Maksym Yarema, Wolfgang Grafeneder, Peter Walter, Ann-Christin Dippel, Matthias Meffert, Dagmar Gerthsen, Julian Stangl, Wolfgang Heiss
While galvanic exchange is commonly applied to metallic nanoparticles, recently its applicability was expanded to metal-oxides. Here the galvanic exchange is studied in metal/metal-oxide core/shell nanocrystals. In particular Sn/SnO2 is treated by Ag+, Pt2+, Pt4+, and Pd2+. The conversion dynamics is monitored by in situ synchrotron X-ray diffraction. The Ag+ treatment converts the Sn cores to the intermetallic AgxSn (x ∼ 4) phase, by changing the core’s crystal structure. For the analogous treatment by Pt2+, Pt4+, and Pd2+, such a galvanic exchange is not observed. This different behavior is caused by the semipermeability of the naturally formed SnO2 shell, which allows diffusion of Ag+ but protects the nanocrystal cores from oxidation by Pt and Pd ions.