Edge states metallic

In the case of palladium particles supported on magnesium oxide, Heiz and his colleagues have shown,29 in an elegant study, a correlation between the number of palladium atoms in a cluster and the selectivity for the conversion of acetylene to benzene, butadiene and butane, whereas in the industrially significant area of catalytic hydrodesulfurisation, the Aarhus group,33 with support from theory, have pinpointed by STM metallic edge states as the active sites in the MoS2 catalysts. 

Fig. 9 STM image (48 x 53 A Ft = 5.3 mV 1-28 nA) showing a M0S2 nanocluster synthesized on a reconstructed Au(l 11) surface. The bright brim extending all the way around the edge is due to localized metallic edge states. Reprinted figure with permission from Bollinger et ai, Physical Review Letters, 2001, 87, 196803. " American Physical Society.

In 2006, Lobinski et al.1 reported on the imaging and speciation analysis of trace elements to study the element distribution, oxidation state, metal site and metal structure in biological environments using mass spectrometric techniques (LA-ICP-MS, SIMS, MALDI-MS) and non-mass-spectrometric techniques such as micro-PIXE (proton induced X-ray emission), XANES (X-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure) -the latter two techniques are very sensitive due the use of a more intense synchrotron beam.1... 

III. The corresponding Kohn-Sham wave functions (Fig. 16b) show that the metallic edge states I and II are localized entirely on the molybdenum edge with sulfur dimers, whereas edge state III is associated with the fully covered sulfur edge (not shown). 

D.4. Energetics and Reaction Pathways Metallic Edge States as Active Sites... 

In the conduction process the termination has a completely different origin. Instead of a continuum of nuclear modes, an electron on the edge levels 0 and N -I- 1 sees the continuum of quasi-free electronic states of the metal electrodes. An electron reaching one of these edge states can proceed into the electrodes and is lost as far as the transport process is concerned. The process is thus irreversible in the sense that the reverse process again takes place completely independently. In expression (17.49) for the conduction this termination expresses itself via the factor X that depends on the inverse lifetimes, and for electrons on the edge states to decay into the metals. 

Because of the strong dependence of the intensity of the white line at the Lj edge of metals like platinum or rhenium upon the chemical situation of this element, it is worth comparing the electronic state of the metal (edge region) with its structural situation (EXAFS) during a reaction process. This has to be done under... 

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