2,089 publications from this institution
Theoretical and experimental studies suggest that lithium ion binds strongly to the carbonyl group in amides. The consequent changes in the molecular geometry of the amide are verified by changes in the infrared spectra and increased barrier heights to rotation
Molecular beams generated from the vapors above the surfaces of alcohol−water mixtures have been examined by mass spectrometry. The alcohols examined are methanol, ethanol, n-propanol, and n-butanol. The variation of the vapor-phase mole fraction of the alcohol, estimated from the cluster populations in the molecular beam, with the liquid mole fraction is found to be identical to that of the surface concentration of the alcohol in the liquid obtained from surface-tension measurements. The populations of the neat alcohol clusters, as distinct from those of alcohol−water clusters, also exhibit a comparable trend. Surface enrichment is considerably more pronounced in the case of n-butanol and n-propanol compared to that of ethanol.
Graphenes with varying number of layers can be synthesized by different strategies. Thus, single-layer graphene is obtained by the reduction of single layer graphene oxide, CVD and other methods besides micromechanical cleavage. Few-layer graphenes are prepared by the conversion of nanodiamond, arc-discharge of graphite and other means. We briefly present the various methods of synthesis and the nature of graphenes obtained. We then discuss the various properties of graphenes. The remarkable property of graphene of quenching fluorescence of aromatic molecules is shown to be associated with photo-induced electron transfer, on the basis of fluorescence decay and time-resolved transient absorption spectroscopic measurements. The interaction of electron donor and acceptor molecules with few-layer graphene samples has been discussed. Decoration of metal nano-particles on graphene sheets and the resulting changes in electronic structure are examined. Few-layer graphenes exhibit ferromagnetic features along with antiferromagnetic properties, independent of the method of preparation. Graphene-like MoS 2 and WS 2 have been prepared by chemical methods, and the materials are characterized by electron microscopy, atomic force microscopy (AFM) and other methods. Boron nitride analogues of graphene have been obtained by a simple chemical procedure starting with boric acid and urea and have been characterized by various techniques.
NbO2, Nb0.98V0.02O2, and Nb0.95V0.05O2 transform from semiconducting to metallic state at temperatures higher than the DTA phase-transition temperatures. Vibrational mode softening and c-axis NbNb pairing appear to be important factors in the mechanism of these transitions. In the solid solutions, c a ratio is maximum at x = 0.5 since the metal-metal interaction along the c axis becomes minimum; conductivity is minimum at this composition since there are no mobile electrons.
No abstract is provided for this article.
High-resolution 11 B magic-angle-spinning (MAS) NMR investigations of boric oxide and alkali borate glasses have been carried out. The chemical shift of the trigonal boron shows anomalous behaviour around 10 mol. % alkali oxide. In an attempt to explain this unusual feature, we have carefully examined the structural model for B 2 O 3 glass. The study suggests that around 66% of the boron atoms is likely to be present in the boroxol units, the rest being present in loose BO 3/2 units. This model is not only consistent with the earlier literature but also shows that stringent topochemical factors are involved in the formation of the tetraborate and the diborate units in alkali borate glasses. It seems plausible that the remarkable tendency of B 2 O 3 to vitrify may itself have a structural origin.
Thiol-derivatised nanoparticles of Au, Pt and Ag (diameter 1–10 nm) forming superstructures, are prepared by the acid-facilitated transfer of well characterized particles in a hydrosol to a toluene layer containing the thiol.
In order to investigate the supramolecular hydrogen-bonded networks and other structural features exhibited by compounds containing an organic cation and an inorganic anion, sulfates of the organic diamines, ethylenediamine (I), 1,3-diaminopropane (II), piperazine (III), and 1,4-diazabicyclo[2.2.2]octane (DABCO) (IV) have been prepared investigated by X-ray crystallography. While II, III, and IV crystallize in the centrosymmetric space group, Pbca, P21/n, Pbcn, respectively, I crystallizes in the non-centrosymmetric space group, P41 exhibiting chirality and weak NLO properties. I–IV exhibit different types of supramolecular H-bonded networks involving the organic cation and the SO2− 4 anion. The nature and strength of the H-bonding network vary from one compound to another, with the strongest network found in piperazinium sulfate, III, and the weakest in II. While in III, water molecules form part of the H-bonded network, they are present as guest molecules in the channels of IV. Thermal stability of the compounds as well as the infrared spectra reflect the stabilities of these H-bonded solids.
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.
Cu and Ni clusters deposited on graphite and metal oxide (TiO2, Al2O3) supports have been investigated by X-ray and UV photoelectron spectroscopy as well as Auger electron spectroscopy. The 2p core-level binding energy of the cluster increases with the decrease in the cluster size and the maximum shift in the case of the smallest cluster is 0.8–1.4 eV (relative to the bulk), the actual value depending on the substrate. The metal LMM Auger line shifts to lower kinetic energies with the decrease in the cluster size and this shift is considerably larger (1.4–3.3 eV) than that of the 2p binding energy. The shifts in the position and intensities of the valence bands with the cluster size have also been studied; the 3d band intensity approaches zero for the smallest cluster size studied by us, the number of atoms in the smallest cluster being in the range 25–75. One of the conclusions from the study is that the magnitude of the shifts in the core-level binding energy and the Auger kinetic energy due to the decrease in the cluster size depends on the substrate, being largest on an insulating substrate such as Al2O3 and least on graphite.
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.
