Novel CuI/tributyl phosphine catalyst system for amination of aryl chlorides

A simple and efficient methodology for the synthesis of triarylamines from aryl chlorides in a single step has been demonstrated using a novel CuI/tributyl phosphine catalyst system with high activity and selectivity (80-87% yield).     

Effect of variation of metal and non-metal elements on various properties of rare-earth-based inverse perovskites Gd3XY (X = Ga,In and Y = B,N)

Ferromagnetic rare-earth-based inverse perovskites Gd₃AlX (X = B, N) are studied using hybrid functionals in the framework of density functional theory. Different exchange correlation potentials are employed to analyze the structural parameters and geometry of the materials. The spin polarization and band structure explain the metallic behavior of these materials with high values of magnetic moment. The calculated elastic constants specify all materials are ordered perovskite compounds, among which Gd₃GaB, Gd₃GaN, Gd₃InN are brittle in nature while as Gd₃InB is ductile in nature. The quasi-harmonic Debye model was used to predict the thermodynamic properties of the material. The analysis of thermoelectric properties viz. Seebeck coefficient, electronic and thermal conductivities at higher temperature has been carried out. To check the optoelectronic response of the material various optical properties have been calculated up to 14 eV photon energy range. The competent thermoelectric and optoelectronic properties with high value of magnetic moment and ductile character suggests the application in thermoelectric and electro-optic devices.     

Synthesis and characterization of nano-composite ion-exchanger; its adsorption behavior

A novel organic-inorganic nanocomposite cation-exchanger has been synthesized via sol-gel method. It was characterized on the basis of FTIR, XRD, SEM, TEM, AFM and Raman studies. The structural studies reveal semi-crystalline nature of the material with the particle size ranging from 1-5 nm. Physiochemical properties such as ion-exchange capacity, chemical and thermal stability of composite material have also been determined. Bifunctional behavior of the material has been indicated by its pH titrations curves. The nanocomposite material exhibits improved thermal stability, higher ion-exchange capacity and better selectivity for toxic heavy metals. The ion-exchange material shows an ion-exchange capacity of 1.8 meq g(-1) for Na(+) ions. Sorption behavior of metal ions on the material was studied in different solvents. The cation exchanger was found to be selective for Pb(II), Hg(II) and Zr(IV) ions. The limit of detection (LOD) and the limit of quantification (LOQ) for Pb(II) ion was found to be 0.85 and 2.85 μg L(-1). Analytically important separations of heavy metal ions in synthetic mixtures as well as industrial effluents and natural water were achieved with the exchanger. The practical utility of polyanilineZr(IV)sulphosalicylate cation exchanger has been established for the analysis and recovery of heavy metal ions in environmental samples.     

Comparative study of titanium(IV)-based exchangers in aqueous and mixed solvent systems

The antimonate, arsenate, tungstate, molybdate and selenite of titanium have been synthesized. Their composition and chemical and thermal stability have been determined. Effects of pH and temperature on ion-exchange capacity have been studied. Titanium antimonate was found to be the most stable. The utility of these ion-exchangers for analytical separations was examined by determining the distribution coefficients for 26 metal ions in some aqueous, non-aqueous and mixed solvent systems. Quantitative separations of HgCd, PbCu and PbZn have been achieved on titanium tungstate columns, and LaBa mixtures have been separated on a titanium arsenate column.     

Edge clique cover of claw-free graphs

The smallest number of cliques, covering all edges of a graph , is called the (edge) clique cover number of and is denoted by . It is an easy observation that if is a line graph on vertices, then . G. Chen et al. [Discrete Math. 219 (2000), no. 1–3, 17–26; MR1761707] extended this observation to all quasi-line graphs and questioned if the same assertion holds for all claw-free graphs. In this paper, using the celebrated structure theorem of claw-free graphs due to Chudnovsky and Seymour, we give an affirmative answer to this question for all claw-free graphs with independence number at least three. In particular, we prove that if is a connected claw-free graph on vertices with three pairwise nonadjacent vertices, then and the equality holds if and only if is either the graph of icosahedron, or the complement of a graph on vertices called “twister” or the power of the cycle , for some positive integer .     

Construction of phase diagrams for nanoscaled Ising thin films on the honeycomb lattice using cellular automata simulation approach

The phase diagrams of the three-layer Ising model on the honeycomb lattice with a diluted surface have been constructed using the probabilistic cellular automata based on Glauber algorithm. The effects of the exchange interactions on the phase diagrams have been investigated. A general mathematical expression for the critical temperature is obtained in terms of relative coupling r = J₁/J and Δ_s = (J_s/J) ? 1, where J and J_s represent the nearest neighbor coupling within inner- and surface-layers, respectively, and each magnetic site in the surface-layer is coupled with the nearest neighbor site in the inner-layer via the exchange coupling J₁. In the case of antiferromagnetic coupling between surface-layer and inner-layer, system reveals many interesting phenomena, such as the possibility of existence of compensation line before the critical temperature.     

Investigation of the optimal annealing temperature for the enhanced thermoelectric properties of MOCVD-grown ZnO films

In this study, we demonstrate the optimization of the annealing temperature for enhanced thermoelectric properties of ZnO. Thin films of ZnO are grown on a sapphire substrate using the metal organic chemical Vapor Deposition (MOCVD) technique. The grown films are annealed in an oxygen environment at 600–1000°C, with a step of 100°C for one hour. Seebeck measurements at room temperature revealed that the Seebeck coefficient of the sample that was not annealed was 152 μV/K, having a carrier concentration of N _D ~ 1.46 × 10¹⁸ cm^–3. The Seebeck coefficient of the annealed films increased from 212 to 415 μV/K up to 900°C and then decreased at 1000°C. The power factor is calculated and found to have an increasing trend with the annealing temperature. This observation is explained by the theory of Johnson and Lark–Horovitz that thermoelectric properties are enhanced by improving the structure of ZnO thin films. The Hall measurements and PL data strongly justify the proposed argument.     

Effect of dispersion and selective localization of carbon nanotubes on rheology and electrical conductivity of polyamide 6 (PA6), Polypropylene (PP), and PA6/PP nanocomposites

Nanocomposites were prepared by adding 1–3 vol % multiwalled carbon nanotubes (MWCNTs) to polyamide 6 (PA6), polypropylene (PP), and their co‐continuous blends of 60/40 and 50/50 volume compositions. Because of the good interaction and interfacial adhesion to the PA6, nanotubes were disentangled and distributed evenly through nanocomposites containing PA6. In contrast, lack of active interactions between the matrix and the CNTs resulted in poor tube dispersion in PP. These observations were then verified by studying the rheology and electrical conductivity of their respective nanocomposites. Absence of percolated CNT clusters and possible wrapping of the tubes by PA6 resulted in low electrical conductivity of PA6/CNT nanocomposites. On the other hand, despite the weak dispersion of the tubes, electrical conductivities of PP/CNT nanocomposites were much higher than all other counterparts. This could be the result of good three‐dimensional distribution of the agglomerated bundles and secondary aggregation of tubes in PP. Adding CNTs to blends of PA6/PP (60/40 and 50/50) resulted in almost full localization of carbon nanotubes in PA6, leading to their higher effective concentration. At the same CNT loadings, the blend nanocomposites had three to seven orders of magnitude higher electrical conductivity than pure PA6. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 368–378