Berlin 2012 – wissenschaftliches Programm

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MI: Fachverband Mikrosonden

MI 4: 100 years since the Laue experiment: Topical aspects of diffraction and scattering (Joint Session KR, BP, DF, GP, MA, MI, MM; related to SYXD)

MI 4.5: Vortrag

Dienstag, 27. März 2012, 10:45–11:00, EMH 225

Analysis of the size and shape of colloidally prepared nanocrystals by Rietveld refinement — •Holger Borchert, Xiaodong Wang, Marta Kruszynska, Joanna Kolny-Olesiak, and Jürgen Parisi — University of Oldenburg, Department of Physics, Energy and Semiconductor Research Laboratory, Carl-von-Ossietzky Str. 9-11, 26129 Oldenburg, Germany

Many properties of colloidal nanocrystals can be tuned by controlling the crystal size and shape. Examples are the quantum size effect in the case of semiconductors or size-dependent catalytic properties in the case of metals. Establishing correlations between the structure and other properties relevant for applications requires suitable methods to characterize the size and shape of nanocrystals. Most evident are imaging techniques like transmission electron microscopy (TEM). However, as a disadvantage only a limited number of particles can be evaluated. Powder X-ray diffraction (XRD), in contrast, probes a large ensemble of nanocrystals, but it remains a challenge to reliably extract information on the crystallite size and shape from XRD data. In this work, colloidal chemistry was used to prepare mono- and bimetallic Pt and Pt/Sn nanocrystals as well as semiconductor nanocrystals of ZnO, CuInS2 and composite particles consisting of CuInS2 and Cu2S. The samples were analyzed by TEM and XRD. Rietveld refinement of XRD data was done with a program enabling to simulate also anisotropic crystallite shapes. This approach turned out to be suitable for the determination of the average size and shape, in particular also in the case of nanorods and composite nanomaterials.