Lecture Frank de Groot
|10 november 2006||FWN-Building 5113.0201, Nijenborgh 4, 9747 AG, Groningen|
|Speaker:||Dr. Frank de Groot|
|Title:||Three new experimental tools to study nanoparticles|
|Date:||Fri Nov 10, 2006|
|Telephone:||+31 50 363 4736 / 4974|
AbstractNanoparticles play an increasingly important role in both fundamental studies in physics and chemistry, as well as in a series of applications. Ultimately one would like to know the detailed many-body electronic structure of a (supported) nanoparticle-adsorbate complex, participating in a chemical reaction or creating a specific optical or electronic response, where these properties are modified by the increased electronic correlation effects in nanoparticles. In my talk, I discuss three new experimental routes to derive electronic and geometric information on nanoparticles: ? Scanning Transmission X-ray Microscopy (STXM) is rapidly improving in its spatial resolution, which is ~20 nm at present. With this resolution, one measures soft X-ray absorption spectra (XAS) under in-situ conditions, up to 1 bar and 500C at present. Potential applications include the in-situ study of sintering of metal nanoparticles embedded in porous oxides, for example Co/TiO2. ? Multiple Photon Dissociation (MPD) InfraRed (IR) spectroscopy is being developed at Free Electron Laser (FEL) sources, in particular at FELIX in Rijnhuizen. MPD-IR is able to study the IR spectra of metal nanoparticles, interacting with small molecules. We studied Co nanoparticles with CO, with H2 and under the co-adsorption of both molecules. In combination with DFT calculations, we have determined the structure of a series of Sc, V, Fe and Co nanoparticles with CO and H adsorbates. This includes the V6H8CO+ cluster-complex, where CO is adsorbed as a molecule (see image). ? Selective X-ray absorption is a technique that enables the measurement of X-ray absorption spectra that are selected for a certain valence, spin-state or neighbour atom. The central ingredient in these experiments is a high-resolution X-ray fluorescence detector that allows the selection of a specific decay channel. With this technique one can measure only those atoms in a nanoparticle that are bonded to the support or that are bonded to the substrate. The consequences of these three techniques for the study of nanoparticles are discussed, including potential future experiments that make use of X-FEL sources.
|Laatst gewijzigd:||22 oktober 2012 14:31|