The Au L 3 XAFS spectra of gold nanoparticles in cavities of cucurbit[6,7]uril are measured. Gold clusters are found to be characterized by smaller (by 0.03 Å) interatomic distances and a considerable reduction in the Au–Au coordination numbers ( N Au–Au ≤ 6) as compared with bulk gold. For all samples, the size distribution of Au nanoparticles is established to have two maxima corresponding to Au in the cavities of cucurbituril molecules with sizes of D (Au) ≤ 1 nm and to macroaggregates of gold. A threefold increase in the Debye–Waller factor at 12 K for nanoparticles in comparison with the bulk metal and a corresponding increase in structural disorder are found. Special physical and chemical properties of small gold particles are dictated by structural disorder, deformations, and stresses increasing with a decrease in size. No visible differences in the Au electronic states upon the transition from bulk to nanoparticles are detected.

The Au L 3 X-ray absorption fine structure (XAFS) spectra have been measured for gold nanoparticles with the calibrated size d Au ∼ 1 nm in the cavities of cucurbit[7]uril molecules. The features of their electronic structure and microstructure have been characterized. It has been found that gold clusters in cavities of cucurbit[7]uril are characterized by smaller (by 0.01–0.02 Å) interatomic distances and a noticeably larger (by a factor of 3 at 12 K) Debye-Waller factor as compared to bulk gold. Analysis of the experimental results and their comparison with the model calculations show that the special properties of atoms on the surface of small metal (gold) particles are not determined by their position at the vertices and edges of small clusters; they are likely attributed to the structural disorder, deformations, and stresses, which increase with a decrease in the size of the particles.

The microstructure of samples containing Ge/Si, GaN/AlN, and InAs/AlAs (Ge, GaN, and InAs quantum dots (QDs) in the Si, AlN, and AlAs matrices, respectively) multilayer heterostructures has been investigated by EXAFS spectroscopy. The effect of the effective thicknesses of Si (or AlN) barrier layers, number of Ge (or GaN) layers in a sandwich, and annealing temperature on the size and shape of Ge (or GaN) clusters, interfacial diffusion in these systems, and formation of three-dimensional ordered ensembles of QDs has been established.

This work is devoted to a structural study of a highly dispersed Pd nanosystem, which is stabilized in the TiO2 matrix, by XAFS spectroscopy. Nanocomposite was prepared from bimetallic PdCo(μ-OOCMe)4(NCMe) precursor followed by processing in several ways: calcination in air and in argon and microwave irradiation. The local structure of Pd catalysts formed by different methods was studied. Possible structural models were considered in detail.

We investigate the microstructure of Ge/Si and GaN/AlN sandwiches containing vertically aligned QDs. The study establishes an influence of blocking layers (Si, AlN) thickness, number of QDs layers (Ge, GaN) in heterostructure and annealing temperature on the microstructure characteristics of systems with quantum dots.

Recently, great efforts are devoted to develop new methods of preparation of high-disperse Pd-containing nanosystems (composed of metal and/or oxide substance) stabilized on oxide matrix. New approach of synthesis is usage of PdCo(μ-OOCMe)4(NCMe) complex and Ti(OBu)4 as precursors to anchor Pd on the surface of oxide matrix surface in a highly dispersed form. The present work is devoted to the structural study of this high-disperse Pd-containing nanosystem by the XAFS spectroscopy. The strong interaction between Pd and Co cations takes place in the studied system. Seemingly, Co cations incorporate into TiO2 oxide matrix, forming mixed oxides. This allows to anchor Pd cations, with the formation of the palladium oxide structures, modified by interaction with Co and Ti cations. These compounds are non-stochiometric and have typical structural features of mixed oxides. All possible structural models are discussed in detail.

By means of analysis of fluorescence spectra close to and far off the K-edge of nickel (XANES and EXAFS methods) during the synthesis of nickel molybdate by the reaction NiO+a-MoO3 ®b-NiOMoO4, an unknown phase was observed which can be related to a product with low atomic nickel content. Nickel coordination with oxygen atoms is in this phase substantially different from octahedral. This signifies that there are several stage of the synthesis. At the initial stage of this synthesis , the traditional formation of the layer of final product, b-NiOMoO4, and its smooth growing for the next time do not take place but an intermidiate phase is formed. The possible phase are offered and analysed. 1 Institute of Solid State Chemistry, 630090 Novosibirsk, Russian Federation 2Boreskov Institute of Catalysis, 630090 Novosibirsk, Russian Federation e-mail: chernov@inp.nsk.su tolochko@inp.nsk.su nix@sunsr.inp.nsk.su Ó Budker Institute of Nuclear Physics

Alternative methods for directed syntheses of clathrochelates and polyclathrochelates with two non-equivalent capping fragments using semiclathrochelate precursors and capping group reactions are described. The lability of antimony-capped iron(II) clathrochelates in remetallation (a capping group exchange) reactions allowed to obtain of mono- and bis-clathrochelates of a general formula FeNx3X1X2 and (FeNx3X1)2X2 (where Nx2− is cyclohexanedione-1,2-dioxime dianion; X1, X2 are different capping groups). The first and unique dioximate [Fe(HNx)3(Sb(C6H5)3)](ClO4) semiclathrochelate was isolated and characterized. The reaction of this complex with differing mono- and bifunctional cross-linking agents (Lewis acids) led to the formation of clathrochelates molecules with non-equivalent capping groups. The clathrochelates with a labile triethylantimony capping group underwent remetallation in the presence of silicon dioxide as a catalyst. The first stage led to the formation of a surface-immobilized mixed SbSi-capped clathrochelate, which under the action of another capping agent desorbed from the surface gives a mono- or bis-clathrochelate depending on the nature of this agent. An alternative pathway using the bis-capping agents has been implemented for synthesis of bis-clathrochelates when reactive fragments of an initial azomethine ligand demonstrate essentially different chemical properties. The oximehydrazonate germanium-capped iron(II) bis-clathrochelate was synthesized starting from a bis-semiclathrochelate, which was initially isolated with bis-capping germanium(IV) tetraethoxide. A further H+-catalyzed macrocyclization with triethyl orthoformate produced germanium-capped bis-clathrochelate. The obtained mono- and bis-clathrochelates have been characterized using elemental analysis, PD mass, IR, UV–Vis and 1H and 13C NMR spectra, and X-ray crystallography (for FeNx3(Sb(C2H5)3)2 complex), as well as by cyclic voltammograms. The distortion angle ϕ values and the main distances in the clathrochelate frameworks have been deduced using 57Fe Mössbauer parameters, and EXAFS data and molecular mechanics calculations, respectively.

Novel cluster Ru chalcogenide materials MoxRuySez and RuxTey were studied in situ using EXAFS in the transmission mode during the oxygen reduction reaction. Reversible changes in the structure of the active center were revealed for the electrochemical reaction as a function of the applied electrode potential. The shift of the potential in the anodic direction from 0.08 to 0.78 V versus rhe (reference hydrogen electrode) in the presence of oxygen resulted in an increase of the Ru-O and simultaneous decrease of the Ru-Ru coordination numbers in the first coordination shell of Ru. Along with the variation of the coordination numbers, we observed reversible changes of the coordination distances: a decrease of the Ru-O and an increase of the Ru-Ru distance with the positive polarization. These changes witness the distortion of the catalytic center upon oxygen adsorption. A tentative mechanism of oxygen activation on RuxXy cluster materials is proposed on the basis of the in situ EXAFS data.

The acoustic properties and crystal structure of high-Tc superconducting cuprates and the related antiferromagnetic phases CuO and Y2BaCuO5 exhibit similar properties at a temperature of about 160 K and 240 K. These properties can be associated with the formation of inhomogeneous state of phase separation. Analysis of the magnetic properties of Y2BaCuO5 shows that these effects are of a nonmagnetic nature. The results of EXAFS data for the high-Tc superconducting compound Hg0.8Tl0.2Ba2Ca2Cu3O8.10 show that the phenomenon of phase separation is suppressed by superconductivity.

A family of novel catalysts for oxygen electroreduction is presented, based on nanostructured RuxXy chalcogenide compounds (X=S, Se, Te). EXAFS data suggest that the catalysts have a core of ruthenium atoms, which has triangular co-ordination and a direct metalmetal bond. Depending on the chalcogen, the Ru-cluster consists of two or three metal layers of different size and mutual co-ordination with chalcogen atoms co-ordinated to the periphery of the cluster. Variation of the chalcogen type affects the size of the Ru-cluster and the strength of its interaction with the chalcogen. This influences the interaction of Ru-clusters with oxygen and thus their activity in the reduction of molecular oxygen.

The state of a platinum carbonyl cluster in an initial aqueous acetone solution and its transformations on the surface of aluminum oxide in the course of catalyst preparation were studied by EXAFS spectroscopy. It was found that water enters the polynuclear framework of the dissolved cluster (the Pt–O distance is 2.55 Å, where O is the oxygen atom of water). Structural changes in the supported cluster in the course of catalyst preparation exhibited a strong interaction of platinum with alumina (the Pt–O distance is 1.92–1.95 Å), beginning at the step of H 2 [Pt 3 (CO) 6 ] 5 adsorption. This interaction was retained upon the subsequent high-temperature treatments of the catalyst. The structures of samples prepared from platinum carbonyl and chloroplatinic acid were significantly different. In the former case, a surface prototype was formed from the initial cluster; in the latter case, the sample consisted of platinum metal clusters of a considerable size.

A new method was developed for the preparation of sulfide catalysts supported on aluminum oxide. The surface assembling of a direct precursor of the active component was used in this method. The method consists in the sequential immobilization of binuclear molybdenum complexes with S-containing ligands on the support surface followed by the immobilization of nickel (cobalt) compounds at the surface molybdenum complexes. The complexation and structure of the resulting complexes in solution and the structure of surface complexes were studied by 95 Mo and 17 O NMR, IR, and EXAFS spectroscopy. The surface assembling of a direct precursor of the active component of sulfide hydrodesulfurization catalysts was demonstrated using IR and EXAFS spectroscopy. The activity of the resulting catalysts in a model reaction of thiophene hydrogenolysis was comparable to the activity of sulfide catalysts of the metal complex origin and was much higher than the activity of commercial catalysts and catalysts prepared by impregnation.

Translation Moiré pictures were first observed in interference topographs obtained using Synchrotron radiation. A film interferometer was prepared on the base of the GeSi heterosystem. Another film interferometer, which presents the heterosystem of epitaxial Si/ porous Si/ substrate Si, permitted us to observe a decrease in the bending of the film atomic planes at annealing of the heterosystem. This bend smoothing was calculated with the sensitivity better than 1Å with the use of X-ray interference topographs. Contrast peculiarities in Moiré pictures are discussed for nondiffracting layers and crystal quantum wells.

Complex oxides: La2NiO4 (I), La3Ni2O7 (II) and La4Ni3O10 (III), belonging to the homologous series Lan+1MenO3n+1, were prepared by the traditional ceramic technique (I) and by that of citrate or nitrate precursors (II), (III). The crystal structure of all samples was determined by means of X-ray diffraction, neutron diffraction and synchrotron radiation spectroscopy. Data on nickel coordination were obtained by EXAFS spectroscopy. Phases (II) and (III) were used for structural investigations as prepared powders (quenched from 1100°C in air), phase (I) was pressed into rectangular bars (5×5×30 mm) and sintered at 1370°C for 5 h. Structural parameters of all phases were refined based on Cmca (I), Cmcm (II) and Cmca (III) space group using the Rietveld analysis. Bond lengths in all compounds were calculated. Oxygen octahedrons centered by nickel ions were distorted in (I) and (II). (I) has two and (II) has four different Ni–O interatomic distances. Phase (III) has both ideal and distorted octahedrons in the structure and two types of nonequivalent Ni sites, as a result. The oxidation state of cations was estimated using the average cation–anion distance approach and the so-called bond valence approach. The results allowed us to suggest that Ni3+ preferably occupied the Ni1 sites, i.e. it is possible to assume some charge ordering inside the lattice.

The synchrotron investigation method is presented for structure research of semiconductor heterosystems with homogeneous layers and superlattices using the variable wavelength of a synchrotron radiation beam passing at the immobile sample. The used experimental procedure is potentially suitable for in situ X-ray diffractometry during the growth of epitaxial layers. For the proposed procedure, the equations are derived for the first time to measure tetragonal crystal lattice distortions and superlattice period distribution. The experimental results have been obtained for heterosystems with layers of AlxGa1−xAs grown by molecular-beam epitaxy (MBE) onto GaAs substrates.

The series of Ru chalcogenide compounds is obtained by varying the nature of the chalcogen with the transition metal (Ru) matrix. The EXAFS technique reveals that the electrocatalytic centre is Ru in a cluster matrix. Furthermore, a reversible change in the structure of the active centre as a function of the applied electrode potential appears.