Regensburg 2007 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 3: Colloids and Nanoparticles I: Structure

CPP 3.5: Talk

Monday, March 26, 2007, 11:15–11:30, H47

Precise structure determination of ZnO and CdSe/ZnS core-shell nanoparticles — •Franziska Niederdraenk¹, Knud Seufert¹, Pawel Luczak¹, Christian Kumpf¹, Reinhard Neder², and Eberhard Umbach¹ — ¹Universität Würzburg, Experimentelle Physik II, Am Hubland, 97074 Würzburg — ²Universität Würzburg, Mineralogisches Institut, Am Hubland, 97074 Würzburg

In order to obtain an appropriate picture of very small nanoparticles (< 5 nm) and their properties a precise geometric structure determination is essential. X-ray diffraction, in principle, is well suited for this purpose. However, well established methods like powder diffraction including Rietveld refinement are not sufficiently reliable for very small particles, since they are based on solid state approaches. One alternative way is to model the entire nanoparticle and use the Debye formula for calculating its diffraction pattern. As this technique imposes no restrictions on the particle, intrinsic parameters like the particle shape, stacking faults or surface strain can easily be considered. Furthermore, modeling of core-shell particles and consideration of parameter distributions is enabled. Modeling of the nanoparticles, calculation of the diffraction pattern and ensemble averaging are embedded in an evolutionary algorithm for an automated fit procedure.

We present data obtained from ZnO particles and CdSe/ZnS core-shell particles. In order to test the sensitivity of individual parameters many different parameter combinations were considered for the ZnO system. For the core-shell particles we will demonstrate that the consideration of a shell is essential for obtaining proper fit results.