http://nopr.niscair.res.in/handle/123456789/7597 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/7602 Title: Preparation of one-dimensional green phosphors (Y,Gd)BO₃:Tb³⁺ nanofibers by electrospinning <br/> <br/>Authors: Liu, Wei; Wang, Ce <br/> <br/>Abstract: <smarttagtype namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="chmetcnv"> One-dimensional (Y, Gd) BO₃: Tb³⁺nanofibers with hexagonal structure have been prepared as potential green phosphors by an electrospinning technique, and characterized with X-ray diffraction,<b style=""> </b>scanning electron microscopy, FT-IR spectrum, TG-DTA and photoluminescence spectra. The effect of annealing temperature on the crystallization and luminescence properties has been studied. The main emission position is centered at 543 nm (⁵<i style="">D</i>₄ →⁷<i style="">F</i>₅). Photoluminescence spectra indicate that fluorescence capability improves with increase in temperature. </smarttagtype> <br/> <br/>Page(s): 307-310 Fri, 26 Feb 2010 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/7601 Title: Carbon nanotubes supported palladium catalysts for selective hydrogenation of cinnamaldehyde under atmospheric pressure <br/> <br/>Authors: Ge, Changhua; Li, Yan; Zhao, Jie; Zhou, Renxian <br/> <br/>Abstract: Carbon nanotubes supported Pd catalysts have been prepared by an impregnation method with aqueous solution containing a Pd(II) salt. The selective hydrogenation of cinnamaldehyde with the catalysts is studied in ethanol at 30 ^oC under atmospheric pressure. A comparison has been made with activated carbon and graphite supported Pd catalysts. The results show that all the Pd/CNTs catalysts prepared with different Pd precursors exhibit good catalytic properties. The Pd/CNTs(a) catalyst prepared with Pd(NH₃)₄Cl₂ as Pd precursor shows remarkably high selectivity (90.8%) for the conversion of cinnamaldehyde (92.0%) with 18.1 mmol H₂ g^-1 min^-1 hydrogenation rate. The influence of the solvent polarity and promoter has been investigated. The results demonstrate that highly polar solvent is advantageous for catalytic activity of Pd/CNTs(a) catalyst, while traces of weak base is advantageous for selective hydrogenation of C=C double bond.<b></b> <br/> <br/>Page(s): 281-287 Fri, 26 Feb 2010 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/7600 Title: Oxidation of lower oxyacids of phosphorus by tetraethylammonium chlorochromate: A kinetic and mechanistic study <br/> <br/>Authors: Vadera, Khushboo; Sharma, D; Agarwal, S; Sharma, Pradeep K <br/> <br/>Abstract: Oxidation of lower oxyacids of phosphorus by tetraethylammonium chlorochromate in dimethyl sulphoxide leads to the formation of corresponding oxyacids with phosphorus in a higher oxidation state. The reaction exhibits 1:1 stoichiometry. The reaction is first order each with respect to chlorochromate and the oxyacids. The reaction does not induce polymerization of acrylonitrile. The oxidation of deuterated phosphinic and phosphorous acids exhibits a substantial primary kinetic isotope effect. The oxidation has been studied in nineteen different organic solvents. The effect of solvent indicates that the solvent polarity plays a major role in the process. It has been shown that the pentacoordinated tautomer of the phosphorus oxyacid is the reactive reductant and the tricoordinated form of phosphorus oxyacids does not participate in the oxidation process. A mechanism involving transfer of a hydride ion in the rate determining step has been proposed. <br/> <br/>Page(s): 302-306 Fri, 26 Feb 2010 22:58:59 GMT http://nopr.niscair.res.in/handle/123456789/7599 Title: Low temperature heat capacities and standard molar enthalpy of formation of the coordination compound Zn(His)(NO₃)₂.1/2H₂O(s) (His = L-⍺- Histidine) <br/> <br/>Authors: Yang, Wei-Wei; Di, You-Ying; Kong, Yu-Xia; Tan, Zhi-Cheng; Gao, Sheng-Li <br/> <br/>Abstract: Low temperature heat capacities of the solid coordination compound Zn(His)(NO₃)₂.1/2H₂O(s) have been measured by a precision automated adiabatic calorimeter over the temperature range 78 - 371 K. The initial dehydration temperature of the coordination compound is determined to be, <i style="">T</i>_D= 326.75 K, by analysis of the heat-capacity curve. The experimental values of the molar heat capacities in the temperature region have been fitted to a polynomial equation of heat capacities with the reduced temperature (<i style="">X</i>), [<i style="">X</i> = <i style="">f </i>(<i style="">T</i>)], by least squares method. Enthalpies of dissolution of {ZnSO₄.7H₂O(s) + 2NaNO₃(s) + L-His(s)} and {Zn(His)(NO₃)₂.1/2H₂O(s) + Na₂SO₄(s)} in 100 ml of 2 mol dm^-3 HCl(aq) at <i style="">T</i> = 298.15 K have been determined to be <i style=""></i>Δ_d<i>H</i>⁰_m,1= 79.830 ± 0.058 kJ mol^-1 and <i style=""></i>Δ_d<i>H</i>⁰_m,2= 51.146 ± 0.041 kJmol^-1 respectively, with a isoperibol solution-reaction calorimeter. The standard molar enthalpy of formation of the compound is determined as <b style=""></b>Δ_f<i>H</i>⁰_m(Zn(His)(NO₃)₂.1/2H₂O, s, 298.15 K) = - 1207.19 ± 2.82 kJ mol^-1 from the enthalpies of dissolution of the reactants and products and other thermodynamic data by a Hess thermochemical cycle. Furthermore, the reliability of the Hess thermochemical cycle has been verified by comparing UV/vis spectra and the refractive indices of solutions obtained from dissolution of the {ZnSO₄.7H₂O(_S) + 2NaNO₃(s) + L-His(s)} and from dissolution of the {Zn(His)(NO₃)₂.1/2H₂O(s) + Na₂SO₄(s)} mixtures. <br/> <br/>Page(s): 295-301 Fri, 26 Feb 2010 22:58:59 GMT