Publications

Photoemission studies of the high T_Csuperconductor, YBa₂Cu₃O₇

Considerable changes are observed in the spectra of the valence band and O(ls) regions in YBa2Cu3O7, when the temperature is lowered from 300K to 80K. The results are interpreted in terms of a progressive formation of O2- 2-like species with decreasing temperature. This is accompanied by the transformation of Cu to Cu. It is suggested that the holes generated at the top of the valence band forming the O2- 2-like species may play a crucial role in the superconductivity of the oxide.

Pressure-induced reversible transformation in single-wall carbon nanotube bundles studied by Raman spectroscopy

We report our high-pressure Raman studies on single-wall carbon nanotube bundles carried out up to 25.9 GPa. The intensity of the radial modes decreases more drastically as compared to that of the tangential modes. The former could be followed up in pressure runs to 3 GPa. The most intriguing observation is the anomalous pressure behaviour of the 1594 cm−1 tangential mode between 10 and 16 GPa. This feature, as well as the pressure dependence of intensity, peak position and linewidth, are reversible on decompression. The anomalous pressure dependence is argued to be associated with faceting of the tubes in the bundle, showing their remarkable resilience.

Room temperature giant magnetoresistance in La_1-xPb_xMnO₃

Oxides of the La1-xPbxMnO3 system show giant magnetoresistance around 300 K. In La1-xPbxMnO3 the magnitude of the magnetoresistance (MR) at 320 K is 85% at 6 T and it is nearly temperature independent over a temperature range 40-320 K. All the compositions (0.1<or=x<or=0.5) show a peak in resistivity around 300-340 K and the magnitude of the MR also shows a peak around the same temperatures. This investigation suggests how to hole dope LaMnO3 in order to achieve maximum MR around 300 K so that these materials can have practical applications.

CCDC 666908: 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.

ChemInform Abstract: Unusual Magnetic Properties of Graphene and Related Materials

Review: 89 refs.

The Possibility of a Liquid Superconductor

All superconductors are solids in their superconducting state, this canonical electronic state of matter presently having only been observed well below the melting temperature of the solid. The discovery of high‐temperature superconductivity in cuprates has widened significantly our horizons of the theoretical understanding of the physical phenomenon. A number of observations point to the possibility that superconductors with a high superconducting transition temperature may not be conventional Bardeen–Cooper–Schrieffer (BCS) superconductors, but rather derive from the Bose–Einstein condensation of real‐space pairs. While BCS superconductors exist in the solid state (probably with the exception of metallic liquid hydrogen at ultrahigh pressures), we argue here that a superconducting charged Bose liquid may be found in a true liquid state of condensed matter at ambient pressure. An experimental scenario is outlined in fluid metal–ammonia solutions for stabilizing and observing a high‐temperature superconducting liquid (ca. 230 K) or at least a vitreous superconductor in the corresponding quenched solutions (ca. 160 K).

Electric-field-induced insulator–metal transitions in thin films of charge-ordered rare-earth manganates

Thin films of charge-ordered Nd0.5Ca0.5MnO3, Y0.5Ca0.5MnO3, and Nd0.5Sr0.5MnO3 have been prepared on Si(100) and LaAlO3(100) substrates by the nebulized spray pyrolysis of organometallic precursors. Small electric fields induce insulator–metal transitions in the films with the resistivity decreasing with increasing current. The current–voltage characteristics are non-ohmic and show some hysteresis. The current-induced negative differential resistance found in these manganate films could have potential technological applications.

Improved mechanical properties of polymer nanocomposites incorporating graphene-like BN: Dependence on the number of BN layers

The mechanical properties of composites of polymethylmethacrylate (PMMA) with two-dimensional graphene-like boron nitride (BN) have been investigated to explore the dependence of the properties on the number of BN layers. This study demonstrates that significantly improved mechanical properties are exhibited by the composite with the fewest number of BN layers. Thus, with incorporation of three BN layers, the hardness and elastic modulus of the composite showed an increase of 125% and 130%, respectively, relative to pure PMMA.

Simple Synthesis of MoS₂ and WS₂ Nanotubes

Trisulfide molybdenum complexes have been employed to produce nanotubes by simple heating in a stream of hydrogen. Bamboo-like stacking (see Figure) was observed, suggesting that the stimulus for the growth of MoS2 nanotubes is similar to that of their carbon equivalents. The wide experience gained with trisulfide complexes directs this technique towards the preparation of other layered sulfide nanotubes, although other precursors are also shown to be successful.

Assemblies of single-walled carbon nanotubes generated by covalent cross-linking with organic linkers

Assemblies of covalently linked single-walled carbon nanotubes with superior gas adsorption properties have been prepared and characterized.

A Novel Monomeric Tin(II) Phosphate, [N(C2H5NH3)3]3+[Sn(PO4)(HPO4)]3−·4H2O, Connected through Hydrogen Bonding

The tin(II) phosphate, [N(C2H5NH3)3]3+[Sn(PO4)(HPO4)]3−4H2O, contains monomeric Sn2(PO4)2(HPO4)2units which form a hydrogen-bonded network with the TREN amine (TREN=N(C2H5NH3)3+ 3); triclinic, space groupP1 (no. 2),a=9.579(1),b=10.507(1),c=10.976(1) Å;α=72.93(1)°,β=78.03(1)°,γ=69.82(1)°,V=984.2(1) Å3,Z=2. The Sn2P2O4core of this unit is a common structural feature of open-framework tin phosphates and may play a role as a building block for this class of materials.

Extended x-ray absorption fine structure studies of bimetallic copper-nickel/.gamma.-alumina catalysts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTExtended x-ray absorption fine structure studies of bimetallic copper-nickel/.gamma.-alumina catalystsG. Sankar, S. Vasudevan, and C. N. R. RaoCite this: J. Phys. Chem. 1986, 90, 21, 5325–5328Publication Date (Print):October 1, 1986Publication History Published online1 May 2002Published inissue 1 October 1986https://pubs.acs.org/doi/10.1021/j100412a084https://doi.org/10.1021/j100412a084research-articleACS PublicationsRequest reuse permissionsArticle Views74Altmetric-Citations6LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts

Comparative study of superconducting LaBa/sub 2/Cu/sub 3/O/sub 7-delta/ and La/sub 3-x/Ba/sub 3+x/Cu/sub 6/O/sup 14+delta/*

No abstract is provided for this article.

Molecular charge-transfer interaction with single-layer graphene

While the effect of electrochemical doping on single-layer graphene (SG) with holes and electrons has been investigated, the effect of charge-transfer doping on SG has not been examined hitherto. Effects of varying the concentration of electron donor and acceptor molecules such as tetrathiafulvalene (TTF) and tetracyanoethylene (TCNE) on SG produced by mechanical exfoliation as well as by the reduction of single-layer graphene oxide have been investigated. TTF softens the G-band in the Raman spectrum, whereas TCNE stiffens the G-band. The full-width-at-half-maximum of the G-band increases on interaction with both TTF and TCNE. These effects are similar to those found with few-layer graphene, but in contrast to those found with electrochemical doping. A common feature between the two types of doping is found in the case of the 2-D band, which shows softening and stiffening on electron and hole doping, respectively. The experimental results are explained on the basis of the frequency shifts, electron–phonon coupling and structural inhomogeneities that are relevant to molecule–graphene interaction.

Phase transitions in spin cross-over systems

Role of molecular reorientation in the vitrification of molecular liquids: A Monte Carlo study of the liquid and glassy states of 2,2-dimethylbutane

The liquid and the glassy phases of 2,2-dimethylbutane have been investigated by isothermal isobaric ensemble Monte Carlo simulation. Thermodynamic Properties and radial distribution functions for both the liquid and the glass have been obtained. The radial distribution functions have been classified into three types based on the accessibility of the group. It has been shown that the structure of the Iiquid and the glass can be understood in terms of the above classification of the radial distribution functions. Molecular reorientation plays an important role in the structural rearrangement accompanying glass formation. As much as 35% of the contribution to the increase in the intermolecular interaction energy on vitrification is due to the reorientation of the neighbouring pairs of molecules. The observed changes in the dimerisation energy and the bonding energy distribution function are consistent with the observed structural changes.

A combined experimental and theoretical study of the charge-transfer compound between C60Br8 and tetrathiafulvalene

C60Br8, unlike C60Br6 and C60Cl6, forms a solid charge-transfer compound with tetrathiafulvalene (TTF), the composition being C60Br8 (TTF)8.The unique complex-forming property of C60Br8 can be understood on the basis of the electronic structures of the halogenated derivatives of C60. Molecular orbital calculations show that the low LUMO energy of C60Br8 compared with the other halogen derivatives renders the formation of the complex with TTF favourable, the four virtual LUMOs being able to accept 8 electrons. The Raman spectrum of C60Br8(TTF)8 shows a marked softening of the bands (-46 cm-1 on average) with respect to C60Br8, suggesting that indeed 8 electrons are transferred per C60Br8 molecule,one from each TTF molecule.The complex is weakly paramagnetic and shows a magnetic transition around 80 K.

A single molecule switch based on two Pd nanocrystals linked by a conjugated dithiol

No abstract is provided for this article.