Molybdenum oxides, bulk structure

Beyond providing bulk structural information about 3-D metal oxide phases, Raman spectroscopy can also provide information about the terminating (and thus 2-D) surface layers of bulk metal oxides. For example, surface Nb=O, V = O, and Mo=O functionalities were detected by Raman spectroscopy for bulk Nb2Os, and for vanadium-niobium, molybdenum-vanadium, molybdenum-niobium, and vanadium-antimony mixed oxide phases (Guerrero-Perez and Banares, 2004 Jehng and Wachs, 1991 Zhao et al., 2003). 

XRD patterns of the prepared samples V-Mo-Zeolite are similar to that of zeolites which suggests that the metal species (i.e. oxide, cations,...) are well dispersed through the zeolites structure and the absence of bulk phases in the XRD patterns implies that for these samples the molybdenum and vanadium oxides are present in either a nanocrystalline state or as a small crystallites which measured less than 4 nm in diameter. Furthermore, XRD and FTIR (1500-400 cm 1) showed no significant damage of the zeolite host structure after exchange and thermal treatment except for the sample V2MoMor. 

The simplest networks are one-dimensional a-networks which may be composed of secondary amides, primary amide dimers or nucleophospholipids. In chapter 5, such structures were discussed as micellar rods and tubules in bulk aqueous solutions. Two-dimensional materials such as copper oxide superconductors, molybdenum sulfide lubricants and intercalated graphites are mostly inorganic. The anisotropic properties are a result of covalent bonds in two dimensions and weak interactions in the third dimension. One may, however, also envision strong hydrogen-bond interactions within an organic layer, whereas adjacent layers are held together only by van de Waals interactions. The two-dimensional, or p-network may form spontaneously from an... 

The inclusion of the six transition metal ions — cobalt, copper, iron, manganese, molybdenum, and zinc — in Table 1.1 is no coincidence — we saw earlier that they are essential trace elements for man. So, together with the 11 bulk elements, we have now identified 17 of the essential elements. Their relative positions in the Periodic Table are shown in Fig. 1.3, which presents the first six rows of the Periodic Table, colour-coded into families. Zn has ligand-binding constants intermediate between those of Mg and Ca " and those of the group of five other transition metals. Unlike them, zinc effectively does not have access to any other oxidation state than Zn (the +1 state compounds are very unstable). Zn not only plays a structural role, but can also fulfil a very important function as a Lewis acid (Chapter 12). 

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