[en] The possibility of using single molecules as active elements of electronic devices offers a variety of scientific and technological opportunities. In this article, we discuss transistors, where electrons flow through discrete quantum states of a single molecule. First, we will describe molecules, where current flows through one cobalt atom surrounded by two insulating terpyridyl ligands. Depending on the length of the insulating part of the molecules, two different behaviors are observed: Coulomb blockade for a longer molecule and the Kondo effect for a shorter molecule. We will also discuss measurements of the C₇₀ fullerene and its dimer (C₁₄₀). In C₁₄₀ devices, the transport measurements are affected by an intercage vibrational mode that has an energy of 11 meV. We observe a large current increase when this mode is excited, indicating a strong coupling between the electronic and mechanical degrees of freedom in C₁₄₀ molecules

[en] A new technique of 3D local structure refinement using full-potential X-ray absorption near edge structure (XANES) analysis is proposed and demonstrated in application to metalloorganic complexes of Ni. It can be applied to determine local structure in those cases where the muffin-tin approximation used in most full multiple scattering schemes fails. The method is based on the fitting of experimental XANES data using multidimensional interpolation of spectra as a function of structural parameters, recently proposed by us, and ab-initio full potential calculations of XANES using finite difference method. The small number of required ab-initio calculations is the main advantage of the approach, which allows one to use computationally time-expensive non-muffin-tin finite-difference method. The possibility to extract information on bond angles in addition to bond-lengths accessible to standard EXAFS is demonstrated and it opens new perspectives of quantitative XANES analysis as a 3D local structure probe

[en] The local 3D structures of electrochemically deposited Cu nanoclusters on p-GaAs(100) with various coverages have been investigated by in-situ surface-sensitive x-ray absorption fine structure (XAFS) analysis. The experimental Cu K-edge XANES of Cu nanoclusters deposited on GaAs surface have been analyzed on the basis of full potential calculations of XANES in the combination with DFT geometry optimization. It has been shown that small partially oxidized Cu nanoclusters are formed when the surface coverage of the Cu overlayer is less than 0.25 monolayer. At higher coverage the Cu microclusters have a fcc structure and are almost not oxidized.

[en] The fine structure of X-ray emission satellite lines just below the Fermi level (Kβ satellite lines), which arise from transitions from valence bands to the core 1s level in 3d transition metals, is a developing technique and the full potential is not well known or understood. On the basis of DFT calculations for some theoretical model complexes that are relevant in bioinorganic chemistry we show that the method can be used to distinguish bonds of the metal atom with different light atoms O/N/C even if the coordination geometries are exactly the same, which is not possible using EXAFS or XANES spectroscopy. Moreover the method is sensitive to the bonding of H to the ligands, which allows to discriminate, for example, between OH- and water near the metal. Both these aspects clearly demonstrate that the Kβ satellite lines yield information that is complementary to traditional X-ray absorption spectroscopy. Good agreement between theoretical and experimental spectra for a complex Mn system was also achieved

[en] The local atomic structure around Ti in Ti-bearing hibonite (CaAl₁₂O₁₉) was studied using X-ray absorption near-edge structure (XANES) spectroscopy and computer modelling. Structural models of the direct substitution of Al by Ti³⁺, Al by Ti⁴⁺ charge balanced by the coupled substitution of Mg²+ for Al, and small Ti clusters were considered. The Ti K -XANES spectra of natural hibonite with different Ti concentration were recorded. Theoretical Ti K - XANES spectra for structural models of hibonite were calculated. It was shown that the theoretical Ti K -XANES spectra for a model with Ti at the five-coordinated M2 site are in agreement with the experimental XANES spectra of hibonite with low concentrations of Ti, while the theoretical spectra for a structural model of clustered Ti are in agreement with the experimental spectra of hibonite with higher Ti contents. (paper)

[en] Cu-SSZ-13 is a highly active catalyst for the NH₃-assisted selective catalytic reduction (SCR) of the harmful nitrogen oxides (NO_x, x=1, 2). Since the catalytically active sites for this reaction are mainly represented by isolated Cu ions incorporated into the zeolitic framework, element-selective studies of Cu local environment are crucial to fully understand the enhanced catalytic properties of this material. Herein, we highlight the recent advances in the characterization of the most abundant Cu-sites in Cu-SSZ-13 upon different reaction-relevant conditions made employing XAS and XES spectroscopies, complemented by computational analysis. A concise review of the most relevant literature is also presented. (paper)

[en] A new technique for the analysis of transient X-ray absorption (also known as pump-and-probe XAS) and extraction of 3D structural information for photoexcited molecules is proposed. It is applied to metal-to-ligand-charge-transfer state of [Cu(dmp)₂]⁺ (dmp=2,9-dimethyl-1,10-phenanthroline) in acetonitrile solution. Theoretical approach combines fitting of XANES spectra with a multidimensional interpolation approximation and calculating theoretical XANES with molecular potentials beyond the muffin-tin approximation. The results of the study show that the best fit of the experimental XANES data includes a solvent molecule binding to the Cu with Cu-N distance of 2.00 A, average distance Cu-N of dmp groups is 2.04 A and that photoexcited state is characterized by significant rocking distortions of the dmp ligands.

[en] Three alternative approaches have been applied to calculate As K-edge XANES of InAs: multiple scattering (MS) theory, non-muffin-tin finite difference method (FDM) and full potential linearized augmented plane wave (FLAPW) method. Such combination allows to make the distinction between two types of non-muffin-tin effects. First, in the interstitial region the potential is not constant. Second, the covalent bonds increase the charge density between nearest atoms and lead to additional loss of spherical symmetry of the potential within MT spheres

[en] Lanthanide silicates have been hydrothermally synthesized using Cu and Ni containers. Chemical formulae of the synthesized compounds correspond to K₃Eu[Si₆O₁₅] 2H₂O, HK₆Eu[Si₁₀O₂₅], K₇Sm₃[Si₁₂O₃₂], K₂Sm[AlSi₄O₁₂] 0.375H₂O, K₄Yb₂[Si₈O₂₁], K₄Ce₂[Al₂Si₈O₂₄]. The oxidation state of lanthanides (Eu, Ce, Tb, Sm, Yb) in these silicates has been determined using XANES spectroscopy at the Eu, Ce, Tb, Sm, Yb, L ₃- edges. The experimental XANES spectra were recorded using the synchrotron radiation source ANKA (Karlsruhe Institute of Technology) and the X-ray laboratory spectrometer Rigaku R- XAS. By comparing the absorption edge energies and white line intensities of the silicates with the ones of reference spectra the oxidation state of lanthanides Eu, Ce, Tb, Sm, Yb has been found to be equal to +3 in all investigated silicates except of the Ce-containing silicate from the run in Cu container where the cerium oxidation state ranges from +3 (Ce in silicate apatite and in a KCe silicate with Si₁₂O₃₂ layers) to +4 (starting CeO₂ or oxidized Ce₂O₃). (paper)

[en] Metallothioneins are the proteins containing seven Cd atoms in tetrahedral arrangement of S atoms. For this compound full multiple scattering XAFS calculations have been used as a tool for verification of structural models generated using molecular dynamic. To determine the sensitivity of the spectrum to different structural parameters and to check does the best-fit XANES spectrum correspond to the correct structure of the complex we have tested method for Cd(SPh)₄ model compound