Copper(I) 2-pyridyl selenolates and tellurolates: synthesis, structures and their utility as molecular precursors for the preparation of copper chalcogenide nanocrystals and thin films.

The complexes, [Cu{EC(5)H(3)(R-3)N}](4) (E/R = Se/Me or Te/R; R = H or Me) were isolated by the reaction between CuCl and NaEC(5)H(3)(R-3)N and were characterized by elemental analyses, uv-vis and NMR ((1)H, (13)C) spectroscopy. The crystal structures of [Cu{SeC(5)H(3)(Me-3)N}](4) and [Cu(TeC(5)H(4)N)](4) revealed that the molecules are tetrameric in which each copper atom lies at the vertex of the tetrahedron and each face of the tetrahedron is capped by the bridging pyridylchalcogenolate ligand. Thermal behavior of these complexes was studied by thermogravimetric analysis. Depending on reaction conditions, thermolysis gave both stoichiometric and non-stoichiometric copper chalcogenides, which were characterized by XRD, EDX, SEM, TEM and SAED techniques. These precursors were used for the preparation of nanocrystals and for deposition of thin films of copper chalcogenides by AACVD (Aerosol Assisted Chemical Vapor Deposition).

Sm(2-x)Dy(x)Zr2O7 pyrochlores: probing order-disorder dynamics and multifunctionality.

The present work involves the synthesis of a series of Sm(2-x)Dy(x)Zr(2)O(7) compounds (0.0 ≤ x ≤ 2.0) by a controlled gel combustion process. The powders were thoroughly analyzed by powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy, and diffuse-reflectance UV-visible spectroscopy. The powder XRD studies revealed the system to be single-phasic throughout with retention of pyrochlore-type ordering until 40 mol % of Dy(3+), beyond which the pyrochlore lattice gives way to the defect fluorite structure. Interestingly, Raman spectroscopic studies (as against XRD studies) showed retention of pyrochlore-type ordering throughout the homogeneity range of the compositions studied. This is perhaps the first study that reports retention of a weak pyrochlore-type superstructure in the Dy(2)Zr(2)O(7) system, which was otherwise known to crystallize in the defect fluorite system. The ionic conductivity measurements showed an increase in the activation energy (E(a)) with an increase in the mole percent of Dy(3+) owing to the decreased mobility with an increase in the degree of disorder. The system possesses a tunable band gap with varying amounts of Dy(3+). First-principles calculations were performed to support a decrease in the band gap of the doped system with an increase in the Dy(3+) content. The potential as photocatalysts of some of these compositions was explored, and they exhibited high photocatalytic activity for degradation of xylenol orange, with t(1/2) increasing from pure Sm(2)Zr(2)O(7) to pure Dy(2)Zr(2)O(7).

Development of a (147)Pm source for beta-backscatter thickness gauge applications.

This paper describes a method for the preparation of (147)Pm sources, utilized in the determination of graphite coating thickness on the inner surface of the zircaloy cladding tube of nuclear fuels. (147)Pm was adsorbed on a limited surface area [1.5mm (ϕ)×2mm (l)] of a cylindrical aluminum rod [1.5mm (ϕ)×10mm (l)]. In brief, the selected tip area [1.5mm (ϕ)×2mm (l)] was anodized at a current density of 15mA/cm(2) at 15°C in 3M·H(2)SO(4) for 2h followed by immersion of this area in 10µL of (147)Pm solution containing 37MBq (1mCi) of activity at pH 6.0 for 24h. The radioactive area was subsequently covered with a thin layer of Polymethyl Methacrylate (PMMA) to prevent leaching of (147)Pm from the source. The quantity of incorporated (147)Pm activity was assayed in a calibrated ion chamber. Quality control tests were carried out to ensure nonleachability, uniform distribution of activity and stability of the sources.

2-Pyridyl selenolates of antimony and bismuth: Synthesis, characterization, structures and their use as single source molecular precursor for the preparation of metal selenide nanostructures and thin films.

Reactions of SbCl(3) and BiCl(3) with M'Se-C(5)H(3)(R-3)N (M' = Li or Na; R = H or Me) gave homoleptic selenolate complexes of the general formula [M{Se-C(5)H(3)(R-3)N}(3)] (M = Sb or Bi). The complexes were characterized by elemental analysis, UV-vis and NMR ((1)H, (13)C and (77)Se) spectroscopy. The single crystal X-ray analysis of [M{Se-C(5)H(3)(Me-3)N}(3)].nH(2)O (M/n = Sb/1.5 and Bi/0.5) revealed that the antimony complex adopts a trigonal pyramidal configuration with monodentate selenolate ligands while the bismuth analogue acquires a distorted square pyramidal configuration defined by two chelating and one monodentate selenolate groups. Pyrolysis of [M{Se-C(5)H(3)(Me-3)N}(3)] either in a furnace or in hexadecylamine (HDA) at different temperatures gave a variety of M(2)Se(3) nanostructures. Thin films of metal selenides have also been deposited on glass substrate by aerosol-assisted chemical vapor deposition (AACVD). Both nanostructures and thin films of metal selenides were characterized by UV-vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM).

Effect of doping on the morphology and multiferroic properties of BiFeO3 nanorods.

In this study we report the synthesis of BiFeO(3) nanorods using a sonochemical technique. The nanorods had a diameter of 20-50 nm, a length of 100-500 nm and exhibit aspect ratios in the range of 5-10. However, after doping, the TEM images of Bi(0.9)Ba(0.1)Fe(0.9)Mn(0.1)O(3) and Bi(0.9)Ca(0.1)Fe(0.9)Cr(0.1)O(3) samples show that the aspect ratios of both the double doped samples have reduced considerably, while retaining the crystallinity of the particles. BiFeO(3) nanorods show a weak ferromagnetic order at room temperature, which is quite different from the linear M-H relationship reported for bulk BiFeO(3). The saturation magnetization of these BiFeO(3) nanostructures has been found to increase on doping with various metal ions (Ba(2+), Ca(2+), Mn(2+), Cr(3+)), reaching a maximum value of 1.35 emu g(-1) for the Bi(0.9)Ba(0.1)Fe(0.9)Mn(0.1)O(3) nanostructures. However, saturation of electric polarization was observed only in case of the Bi(0.9)Ca(0.1)Fe(0.9)Cr(0.1)O(3) nanostructures.

First-principles study of the H(2) interaction with transition metal (Ti, V, Ni) doped Mg(0001) surface: Implications for H-storage materials.

Using first-principles calculations we have investigated the interaction of hydrogen molecules with clean and M (Ti, V, and Ni) doped Mg(0001) surfaces. The calculations have been carried out using plane-wave-based pseudopotential method under the formalism of density functional theory. First we have calculated the stability of the M atoms on the Mg surface. On the basis of the energetic criteria, we found that all these M atoms prefer to substitute one of the Mg atoms from the second layer than the top surface atom. In the second step we have studied the interaction of a hydrogen molecule with the clean and doped Mg surface. The results show that for M atoms at the surface, the hydrogen molecule undergoes spontaneous dissociative chemisorptions. However, for M atoms in the second layer, it requires to cross an activation barrier to undergo molecular dissociation. Furthermore, to understand the mobility of hydrogen atoms on the surface we have calculated the diffusion energy barriers for the M doped surface. Contrary to the molecular dissociation behavior, it is found that the mobility of hydrogen atoms on the surface is easier if the M atoms are placed in the second layer in comparison to that in the top surface layer. It is believed that the results of the present study provide useful information based on the first-principles calculations for synthesizing Mg based materials for hydrogen storage with optimal performance.