Publications

Investigations of Fe-Ru bimetallic catalysts by in situ M�ssbauer and EXAFS studies

No abstract is provided for this article.

A combined XPS-UPS-EELS study of nitrogen adsorbed on clean and barium-promoted iron surfaces: The nature of the precursor to dissociation

For N2 on a clean Fe surface, the adsorbed precursor in a parallel orientation becomes predominant around 110 K, while at lower temperatures it coexists with a weakly adsorbed species. On a Ba-promoted Fe surface, however, N2 is present exclusively in the precursor state in the temperature range 80–150 K following moderate exposure. Besides exhibiting a low N-N stretching frequency of 1530 cm−1, the precursor shows a clear separation between the 5σ and 1π levels in the UPS; the precursor dissociates to give a nitridic species around 160 K.

Thermodynamics and Kinetics of Oxidation of <font>Pr</font>₂<font>O</font>₃ and <font>Tb</font>₂<font>O</font>₃ to Nonstoicheiometric Oxides

No abstract is provided for this article.

Direct measurement of the charge ordering gap in using vacuum tunnelling

We have used tunnelling spectroscopy (TS) to probe the density of states (DOS) of the rare earth manganate , which shows a transition to a charge ordered (CO) antiferromagnetic insulating state from a ferromagnetic metallic state. We find that a gap opens up in the DOS around the Fermi level, , as the solid is cooled below the charge ordering temperature . The charge ordering gap was found to be strongly temperature dependent for and for it reaches a limiting value of nearly 0.27 eV. Above the temperature dependence of the DOS at was found to be similar to that of the solids such as which show colossal magnetoresistance but no charge ordering.

Phase transformations in solids

No abstract is provided for this article.

Deffect Structure of LAMNO3

No abstract is provided for this article.

Novel series of thallium cuprate superconductors

The TlCa1−x Lnx Sr2 Cu2 O7+δ(Ln = rare earth) system shows electron-superconductivity when x= 0.25 and hole-superconductivity when x> 0.25. The Tc is generally in the 60–90K in both these regimes. TlSr2−x Lax CuOy (1021) also show electron or hole superconductivity (Tc∼40K) depending on x.

Solid State Chemistry

No abstract is provided for this article.

1,2-, 1,3- and 1,4-Benzenedicarboxylates of Cd and Zn of different dimensionalities: Process of formation of the three-dimensional structure

A systematic study of the benzenedicarboxylates (BDCs) formed by cadmium and zinc with the three isomeric dicarboxylic acids in the presence or absence of amines has been carried out. Several BDCs have been prepared under hydrothermal conditions and their structures established by X-ray crystallography. It is pointed out that the formation of the three-dimensional structures is most favored in the case of 1,4-benzenedicarboxylic acid. An example of a Zn 1,4-BDC where the three-dimensional structure is formed favorably with the increase in reaction temperature is discussed. A one-dimensional chain structure is shown to transform to a three-dimensional structure as a function of time at an appropriate temperature.

Foreword by Professor C.N.R. Rao

Unknown

A novel method of preparing thiol-derivatised nanoparticles of gold, platinum and silver forming superstructures

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.

¹¹ B NMR spectra and structure of boric oxide and alkali borate glasses

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.

Probing the structural changes in the phase transitions of a Bi2MoO6 catalyst: the nature of the intermediate-temperature phase

The nature of the phase transitions of Bi2MoO6 has been investigated by the combined use of X-ray diffraction and X-ray absorption spectroscopy. The distorted MoO6 octahedra in the low-temperature form are shown to undergo further distortion in the intermediate-temperature form before transforming to MoO4 tetrahedra in the high-temperature phase.

RETRIEVAL AND SIMULATION OF UV PHOTOELECTRON SPECTRA OF ORGANIC MOLECULES

No abstract is provided for this article.

Surface Enrichment in Alcohol−Water Mixtures

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.

A study of graphene decorated with metal nanoparticles

Interaction of nanoparticles of metals such as Ag, Au, Pt and Pd with graphene has been examined by employing Raman spectroscopy and first-principles calculations. There is a significant shift of the G-band as well as of the other bands, in addition to variation in the relative intensities of D- and 2D-bands when the metal nanoparticles are deposited on graphene. The shifts in the G- and D-bands show meaningful trends with the ionization energies of the metals as well as the charge-transfer energies. Results from the calculations underscore the importance of charge-transfer between the metal particles and graphene.

Erratum

13C nuclear magnetic resonance studies of the binding of alkali and alkaline earth metal salts to amides

13 C resonances of carbonyl and methyl groups in amides are shifted down-field on interaction with alkali and alkaline earth metal salts. The magnitude of the shift depends on the ionic potential of the cation. Ions like Li+ bind to the amide carbonyl group both in neat amide solutions as well as in concentrated salt solutions in water.