Publications

An investigation of transition metal clusters deposited on graphite and metal oxide substrates by a combined use of XPS, UPS and Auger spectroscopy

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.

Pressure-induced phase transitions in nanocrystalline ReO₃

Pressure-induced phase transitions in the nanocrystals of ReO3 with an average diameter of ∼12 nm have been investigated in detail by using synchrotron x-ray diffraction and the results compared with the literature data of bulk samples of ReO3. The study shows that the ambient-pressure cubic I phase (space group ) transforms to a monoclinic phase (space group C 2/c), then to a rhombohedral I phase (space group ), and finally to another rhombohedral phase (rhombohedral II, space group ) with increasing pressure over the 0.0–20.3 GPa range. The cubic I to monoclinic transition is associated with the largest volume change (∼5%), indicative of a reconstructive transition. The transition pressures are generally lower than those known for bulk ReO3. The cubic II () or tetragonal (P4/mbm) phases do not occur at lower pressures. The nanocrystals are found to be more compressible than bulk ReO3. On decompression to ambient pressure, the structure does not revert back to the cubic I structure.

An EELS study of water, methanol, formaldehyde and formic acid adsorbed on clean and oxygen-covered zinc(0001) surfaces

No abstract is provided for this article.

Borocarbonitrides, B_<i>x</i>C_<i>y</i>N_<i>z</i>: Synthesis, Characterization, and Properties with Potential Applications

Borocarbonitrides, BxCyNz, constitute a new family of layered two-dimensional materials and can be considered to be derived from graphene. They can be simple composites containing graphene and BN domains or more complex materials possessing B-C and C-N bonds besides B-N and C-C bonds. Properties of these materials depend on the composition, and the method of synthesis, wherein one can traverse from the insulating end (BN) to the conducting end (graphene). In this article, we present an up-to-date review of the various aspects of borocarbonitrides including synthesis, characterization and properties. Some of the properties have potential applications, typical of them being in gas adsorption and energy devices such as supercapacitors, fuel cells and batteries. Performance of borocarbonitrides as catalysts in the electrochemical hydrogen evolution reaction is impressive. It is noteworthy that with certain compositions on borocarbonitrides, field-effect transistors can be fabricated.

Spectroscopic studies of hydrogen bonding in donor-acceptor systems

Hydrogen bonding between various donors and acceptors has been investigated by employing infra-red, n.m.r. and electronic spectroscopy. The effects of acidity of the acceptor and the basicity of the donor on the thermodynamics of hydrogen bonding have been investigated. The relations between ΔH°, ΔνOH, ΔF° and other parameters have been discussed.

HighT c superconductivity in oxides derived from La1·8Sr0·2CuO4

No abstract is provided for this article.

ChemInform Abstract: High Catalytic Efficiency of Transition‐Metal Complexes Encapsulated in a Cubic Mesoporous Phase.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Chemical design of solid inorganic materials

Graphen‐analoge anorganische Schichtmaterialien

Die Entdeckung von Graphen war eine Sensation für die Chemie, aber auch für die Physik, die Materialwissenschaften und verwandte Gebiete. Die ungewöhnlichen Eigenschaften des Graphens weckten auch ein Interesse an anderen Schichtmaterialien wie Molybdänsulfid und Bornitrid. So sind in den letzten Jahren verschiedene ein‐ und mehrlagige Chalkogenide und andere anorganische Materialien mit interessanten Eigenschaften und Anwendungsmöglichkeiten hergestellt und charakterisiert worden. Dieser Aufsatz gibt eine Übersicht über neue zweidimensionale Nanomaterialien. Dabei behandeln wir nicht nur Synthese und Charakterisierung, sondern auch spektroskopische und optische, magnetische und elektrische Eigenschaften und mögliche Anwendungen. Außerdem werden Kompositmaterialien aus anorganischen Schichtstrukturen mit Graphen und Polymeren und schließlich Borcarbonitride behandelt.

International Conference on Superconductivity, ICSC, January 10-14, 1990 Bangalore, India

No abstract is provided for this article.

Modification of the multiferroic properties of Y CrO3 and LuCrO3 by Mn substitution

The effect of Mn substitution on the multiferroic properties of Y CrO3 and LuCrO3 has been investigated. Solid solutions of the type Y Cr1−x Mn x O3 and LuCr1−x Mn x O3 ( x = 0.0 – 0.3 ) possess orthorhombic structures with Pnma and Pbnm space groups respectively. Both the series of materials show canted antiferromagnetic behavior with T N decreasing with increasing x . They also exhibit ferroelectricity with the transition temperature decreasing with increases in x . The x = 0.3 compositions show improved magnetic properties with a ferroelectric transition in the 418–425 K range.

Single-walled carbon nanotube bundles intercalated with semiconductor nanoparticles

Nanoparticles of CdSe, CdS and ZnSe have been incorporated in the inter-tubular gaps of single-walled carbon nanotube (SWNT) bundles. Electron microscope, X-ray diffraction (XRD), electronic spectroscopy and Raman studies have been employed to characterize these systems. The lengths of the intercalate inside the bundles could be varied by changing the reaction conditions. Electronic absorption and photoluminescence studies from the semiconductor intercalates show the expected blue-shift with respect to the corresponding bulk samples in CdS and ZnS samples. The SWNT lattice is expanded on incorporating CdSe as confirmed by XRD in the low-angle range. The expansion in the lattice is also corroborated by the Raman measurements which show a considerable red-shift for both the radial and the tangential modes of the SWNT signal, thus signifying an increase in the van der Waals gap between the tubes in the bundle. The red-shift of the Raman signal is due to the decrease in the inter-tube interactions as well as due to doping effects.

151 Eu and 57 Fe Mössbauer studies of EuCoO 3

No abstract is provided for this article.

CCDC 204199: Experimental Crystal Structure Determination

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.

Relation between O—H stretching frequency and hydrogen bond energy: re-examination of the Badger–Bauer rule

Experimentally a large number of linear relations have been found between the change in OH stretching frequency, Δ, on hydrogen bonding and the hydrogen bond energy, ΔH. A least square treatment of these Δ against ΔH relations is carried out for constant acceptor, variable donor as well as constant donor, variable acceptor systems. Generally, the constant-acceptor plots have much higher values of intercepts than the constant-donor plots. The slopes of the constant-donor plots seem to vary with the basicity of the donor . However, since Δ should go to zero when there is no interaction, it is suggested that the complete Δ against ΔH, relation could be nonlinear. Molecular orbital calculations have been employed to throw light on the Δ against ΔH relation. It is also shown that charge transfer theory when applied to the hydrogen bond predicts a relation between shown that charge transfer theory when applied to the hydrogen bond predicts a relation between ΔH and the quantity (20–2)½ where 0 and , are the free and perturbed OH stretching frequencies.

Novel features of rapidly quenched melts of Bi2(Ca,Sr)3Cu2O8+δ

By roller quenching and water quenching melts of Bi2(Ca, Sr)3Cu2O8+δ, glasses have been obtained. These glasses exhibit two glass transitions as well as two crystallization transitions. Microwave absorption studies show the glass to be weakly superconducting at 77 K, probably due to the presence of ultramicrocrystallites. The glass on crystallization at 870 K gives the crystalline n=1 member of the homologous series Bi2(Ca, Sr)n+1CunO2n+4 and the n=2 member on annealing at 1100 K. The glass route provides a unique means of obtaining the n=2 member of the series. On prolonged annealing of the glass at 1120 K, the n=3 member seems to be formed.

Mechanism of crystal structure transformations. Part 3.—Factors affecting the anatase-rutile transformation

The first page of this article is displayed as the abstract.

Properties of C60 and C70 in the Solid State

No abstract is provided for this article.