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An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The semiconductor-metal transition in Ti3O5 is significantly affected by vanadium doping. The unit cell volume, ΔH, Δϱ as well as ΔχM decrease markedly up to 0.1% V3O5 and gradually thereafter until at ∼ 10% V3O5, the transition disappears.
Based on in situ X-ray diffraction and EXAFS studies, it is shown that NiTiO3 formed by the reaction of TiO2(anatase) with Ni2+ during the calcination of Ni/TiO2, gives rise to Ni metal and TiO2(rutile) on reduction, a process that may be responsible for the strong interaction between the metal and the oxide support.
Marked changes in the LVV/LMV and LVV/LMM Auger intensity ratios of Co, Ni and Cu are observed on depositing Al on their surfaces. These changes, ascribed to charge-transfer or hybridization effects, are accompanied by changes in the intensity of the satellites next to the core levels of the transition metals.
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Satisfactory solutions have been obtained for the phase transitions of alkali halides by employing the Born-Mayer model with the recently revised van der Waals coefficients. These new coefficients for the most part eliminate the use of high van der Waals term multiplicants K > 1 as required earlier by Rao and co-workers when Mayer's coefficients were employed; there appears to be need for increased van der Waals terms in the Born-Mayer description of alkali halides.
Ternary metal oxynitrides are generally prepared by heating the corresponding metal oxides with ammonia for long durations at high temperatures. In order to find a simple route that avoids use of gaseous ammonia, we have employed urea as the nitriding agent. In this method, ternary metal oxynitrides are obtained by heating the corresponding metal carbonates and transition metal oxides with excess urea. By this route, ternary metal oxynitrides of the formulae MTaO2N (M=Ca, Sr or Ba), MNbO2N (M=Sr or Ba), LaTiO2N and SrMoO3− x N x have been prepared successfully. The oxynitrides so obtained were generally in the form of nanoparticles, and were characterized by various physical techniques.
The valence state of Yb in some of its intermetallics, YbNi2Ge2, YbCu2Si2 and YbPd2Si2 has been investigated by LIII(Yb) absorption edges and X-ray pnotoelectron spectra in the 4f and 4d regions. These studies establish the presence of mixed valence in all three systems and illustrate the utility of 4f and 4d spectra in the study of mixed valence in Yb compounds.
Hydrocarbon (LPG) sensors based on the nanostructures of V2O5 do not exhibit satisfactory characteristics, while sensors based on WO2.72 nanowires show high sensitivity (∼1800) for 2000 ppm of LPG at 200 °C as well as relatively short recovery and response times. Impregnation of WO2.72 nanowires with Pt in the 0.1–1.0 at% range, significantly improves the sensor characteristics, the sensitivity increasing with Pt concentration and reaching a value of ∼106 for 2000 ppm of LPG in the 100–200 °C range with 1 at% Pt. The sensitivity remains high even for 50 ppm of LPG, and is not affected significantly by repeated cycles or humidity. The mechanism of sensing of hydrocarbons by WO2.72 nanowires is explained on the basis of adsorbed oxygen species.
Pd, Ag, Cd and Au clusters of varying sizes have been investigated by scanning tunneling spectroscopy under ultra-high vacuum. The conductance of the clusters decreases markedly when the cluster diameter is ≤1 nm. A plot of the density of states at the Fermi level against the cluster volume varies nearly linearly up to a cluster volume of 4 nm3 (diameter ∼2 nm). Below a cluster diameter of 1 nm, an energy gap occurs, the value of which increases with the decrease in cluster size, reaching values up to 70 meV at small sizes. Clearly, the very small clusters tend to become non-metallic.
The chemistry of Nanomaterials , The chemistry of Nanomaterials , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
The L3/L2 white-line intensity ratio in transition-metal oxides deviates widely from the statistical value of 2 : 1 but shows interesting systematics. In a series of oxides of a given metal, the ratio reaches a maximum for the d5 configuration (e.g. MnO) and a minimum for the d0 configuration (e.g. KMnO4). In a series of monoxides, sesquioxides and dioxides of different metals, the ratio is again a maximum at the d5 configuration and decreases as the configuration changes towards d0 or d10. Our results, obtained by electron energy-loss spectroscopy, carried out in an electron microscope, are interpreted on an atomic mechanism involving spin-spin coupling. According to this model, the L2 transition probability decreases in the progression d0 to d5 whereas the L3 transition probability decreases beyond d5.
Characteristic features of a perilous neuro-degenerative disease such as the Alzhiemer’s disease is fibrillar plaque formation by the amyloid (Aβ) peptide. We have modelled the formation and disintegration of fibrils by studying the aggregate structures formed by Aβ structural motif diphenylalanine as well as insulin and bovine serum albumin at the organic–aqueous interface. Even small concentrations of curcumin in the organic medium or Cu2+ and Zn2+ ions in the aqueous medium are found to break down the fibrillar structures.
Adsorption of oxygen has been studied on (111), (110) and (100) surfaces of Ag, Cu, and Ni employing XPS and UPS. Besides atomic species with an O(1s) binding energy of ~ 530 eV, molecular adsorption is found on all the three Ag surfaces associated with a characteristic O(1s) binding energy of 532 eV. He II spectra show a feature around 2.5 eV due to the molecular species. Molecular adsorption is also found on all the three surfaces of Cu with a characteristic binding energy of 533 eV. He II spectra show characteristic features due to molecular adsorption on these surfaces at 100 K. The proportion of molecular species is maximum on the (111) surfaces and least on the (110) surfaces of both Ag and Cu. On Ni surfaces, there is no molecular adsorption; a unique O(1s) feature ascribed to O1− species is found at 531 eV. The intensity of this feature does not vary significantly with temperature in contrast to the O(1s) feature due to the molecular species on Ag and Cu surfaces.
