Absorption metal oxide bulk

A comparison of the X-ray absorption edges of bulk gold and Aujs [39,40] indicates that all the main features of the edge of the bulk metal are also exhibited by the cluster, the white line intensity showing qualitatively that the gold atoms in the cluster have a low mean oxidation state [150], closely approaching that in the bulk. 

Macroscopic experiments allow determination of the capacitances, potentials, and binding constants by fitting titration data to a particular model of the surface complexation reaction [105,106,110-121] however, this approach does not allow direct microscopic determination of the inter-layer spacing or the dielectric constant in the inter-layer region. While discrimination between inner-sphere and outer-sphere sorption complexes may be presumed from macroscopic experiments [122,123], direct determination of the structure and nature of surface complexes and the structure of the diffuse layer is not possible by these methods alone [40,124]. Nor is it clear that ideas from the chemistry of isolated species in solution (e.g., outer-vs. inner-sphere complexes) are directly transferable to the surface layer or if additional short- to mid-range structural ordering is important. Instead, in situ (in the presence of bulk water) molecular-scale probes such as X-ray absorption fine structure spectroscopy (XAFS) and X-ray standing wave (XSW) methods are needed to provide this information (see Section 3.4). To date, however, there have been very few molecular-scale experimental studies of the EDL at the metal oxide-aqueous solution interface (see, e.g., [125,126]). 

First qualitative analyses of the Fourier transformations (FTs) of the respective EXAFS (extended X-ray absorption fine structure) oscillations of the reference compounds (figure 6) show peaks up to 5.5 A while the incorporated transition metal oxides A and B show only peaks up to 3.3 A. A comparison of the first shell (oxygen shell) between 1 and 2 A shows no difference in the magnitude for the reference CoFe2C>4 and the products A and B. In contrast, the higher shells, which represent the metal-metal distances, are strongly reduced for the products A and B compared to the bulk reference compounds, which is another indication for small particles within the pores. Further quantitative EXAFS analyses are currently in progress. 

Optically induced transitions between energy levels characteristic of the bulk lattice, followed by transfer of energy or charge to the adsorbate Absorption of CdS, ZnO, Ti02 etc. inside their band edges [53] Adsorbent-initiated (ANI) Oxygen photosorption at 02/metal oxide interfaces... 

IR and UV-VIS spectroscopies. The use of IR method enables one to control the loading of precursors and their further transformation into the oxide moiety. At the metal loading as low as a few wt % (metal basis), the IR bands characteristic of metal oxides are too weak to judge on their formation. As to electron absorption spectra, this technique was successfully applied in [8] not only to identify the metal sulfide and solenoid nanoclusters encapsulated in zeolites but also to estimate their mean sizes basing on the blue-shift of absorption-edge in respect to bulk material. Unfortunately, this technique in studying the supported metal oxides turned out to be ineffective mainly because of too broad bands obtained for the samples subjected these investigation. 

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