Search results for "Molybdate"
showing 10 items of 31 documents
Gas phase heterogeneous partial oxidation reactions
2018
Abstract Mixed metal oxides are used as catalysts in the gas phase partial oxidation of hydrocarbons. This paper will present the principles of catalyst choice for selective oxidation reactions as well as the structural features of metal oxide catalysts. The nature of active sites in selective oxidation reactions will also be briefly discussed. We will pay special attention to several representative reactions: (1) ODH of short chain alkanes (from C1 to C4), (2) propene partial oxidation/ammoxidation on bismuth molybdate based catalysts, (3) n-butane direct oxidation to maleic anhydride on VPO type catalysts, and (4) propane direct oxidation/ammoxidation on mixed MoVTe(Sb)Nb–O catalysts. Fin…
Electron Spin Resonance study of charge trapping in α-ZnMoO4 single crystal scintillator
2015
The origin and properties of electron and hole traps simultaneously appearing in a-ZnMoO4 scintillator after X-ray irradiation at low temperatures (T < 35 K) were studied by Electron Spin Resonance (ESR). ESR spectrum of the electron type trap shows pronounced superhyperfine structure due to the interaction of electron spin with nuclear magnetic moments of 95,97Mo and 67Zn lattice nuclei. Considering the nearly tetragonal symmetry of the center this allows us to identify the electron trap as an electron self-trapped at the (Mo(1)O4) 2 complex. Nearly 60% reduction of the spin–orbit coupling at the Mo(1) ion is caused by the overlap of the Mo and ligand oxygen orbitals indicating an essentia…
Keyhole limpet haemocyanin: negative staining in the presence of trehalose
1995
Abstract Samples of unpurified and purified haemocyanin from the giant keyhole limpet Megathura crenulata have been studied by transmission electron microscopy (TEM) using mixtures of trehalose with the negative stains, uranyl acetate and ammonium molybdate. Trehalose is a known protein preservative during air and freeze drying, UV irradiation and high temperatures, and therefore offers the possibility of protecting proteins during the drying of negatively-stained specimens and their subsequent electron microscopical study. Evidence is presented that trehalose possesses satisfactory stability within the electron beam during conventional room temperature, negative-staining studies. The combi…
Negative Staining and Cryo-negative Staining: Applications in Biology and Medicine
2013
Negative staining is widely applicable to isolated viruses, protein molecules, macromolecular assemblies and fibrils, subcellular membrane fractions, liposomes and artificial membranes, synthetic DNA arrays, and also to polymer solutions and a variety of nanotechnology samples. Techniques are provided for the preparation of the necessary support films (continuous carbon and holey/perforated carbon). The range of suitable negative stains is presented, with some emphasis on the benefit of using ammonium molybdate and of negative stain-trehalose combinations. Protocols are provided for the single droplet negative staining technique (on continuous and holey carbon support films), the floating a…
Negative staining across holes: application to fibril and tubular structures.
2007
The negative staining technique, when used with holey carbon support films, presents superior imaging conditions than is the case when samples are adsorbed to continuous carbon films. A demonstration of this negative staining approach is presented, using ammonium molybdate in combination with trehalose, applied to several fibrillar and tubular samples. Fibrils formed from the amyloid-beta peptide and the protease inhibitor pepstain A spread very well unsupported across holes and the different polymorphic fibril forms can be readily assessed. However, tubular forms of amyloid-beta have a tendency to be flattened, due to surface tension forces prior to and during specimen drying. Sub-fibril a…
Reactivity of H2S and H2S/H2 Mixture With Molybdenum Oxide Thin Films Epitaxied on CoO (100) : Characterization by Rheed and Auger Spectroscopy
2010
Molybdenum-Cobalt composite oxide films were prepared by the evaporation of molybdenum trioxide on a fresh cleaved CoO (100) surface (Thickness = 10 A). The MoO3-CoO interface has been characterized simultaneously by reflexion high electron diffraction (RHEED) and Auger Electron Spectroscopy (AES). The thin film structure and composition depend on the annealing temperature. After a 300°C treatment, metallic cobalt islands nucleate at the interface thin film - CoO (100) and crystallize with the cubic FCC symmetry. After a 700°C treatment cobalt molybdate (a CoMoO4) islands grow. The metastable crystallites are epitaxied on CoO (100). After a 900°C treatment, the thin film consists of flat tw…
8-Hydroxyquinoline-2-Carboxylic Acid as Possible Molybdophore: A Multi-Technique Approach to Define Its Chemical Speciation, Coordination and Sequest…
2020
8-hydroxyquinoline-2-carboxylic acid (8-HQA) has been found in high concentrations (0.5&ndash
The role of molybdenum in Mo-doped V–Mg–O catalysts during the oxidative dehydrogenation of n-butane
1999
Abstract A detailed study on the influence of the addition of molybdenum ions on the catalytic behaviour of a selective vanadium–magnesium mixed oxide catalyst in the oxidation of n-butane has been performed. The catalysts have been prepared by impregnation of a calcined V–Mg–O mixed oxides (23.8 wt% of V2O5) with an aqueous solution of ammonium heptamolybdate, and then calcined, and further characterised by several physico-chemical techniques, i.e. SBET, XRD, FTIR, FT-Raman, XPS, H2-TPR. MgMoO4, in addition to Mg3V2O8 and MgO, have been detected in all the Mo-doped samples. The incorporation of molybdenum modifies not only the number of V5+-species on the catalyst surface and the reducibil…
Synthesis of MoO3 Nanostructures and Their Facile Conversion to MoS2 Fullerenes and Nanotubes.
2007
The fast thermolysis of ammonium molybdate leads to a mixture of MoO3 and Mo5.3O14.5(OH)2.8(H2O)1.36 with spherical and rod-like morphologies. The oxide mixture can be converted in quantitative yield to inorganic fullerene-type (IF) MoS2 and MoS2 nanotubes (NT) by H2S reduction using a facile and quick procedure. The products were studied by X-Ray Diffraction (XRD) and by Transmission Electron Microscopy (TEM). TEM analysis reveals that the spherical and rod-like morphology of the oxide precursor is preserved during the H2S treatment.
Transmission electron microscopical studies on some haemolymph proteins from the marine polychaete Nereis virens.
2001
Abstract The hexagonal bilayer haemoglobin molecule from Nereis virens has been investigated in a comparative study using several different negative stain electron microscopical specimen preparations (i.e. by conventional adsorption to continuous carbon support films, by the negative staining-carbon film technique and by negative staining across the holes of holey carbon support films with air-drying and rapid freezing/cryo-negative staining). The benefits and limitations of these different approaches are indicated, with the overall conclusion that negative staining with ammonium molybdate across holes creates the best possibilities for molecular imaging, and also has the potential for the …