Structure and properties of lithium thio-boro-germanate glasses

Structural studies of the ternary xLi₂S + (1 − x)[0.5B₂S₃ + 0.5GeS₂] glasses using IR, Raman, and ¹¹B NMR show that the Li₂S is not shared proportionately between the GeS₂ and B₂S₃ sub-networks of the glass. The IR spectra indicate that the B₂S₃ glass network is under-doped in comparison to the corresponding composition in the xLi₂S + (1 − x)B₂S₃ binary system. Additionally, the Raman spectra show that the GeS₂ glass network is over-modified. Surprisingly, however, the ¹¹Boron static NMR gives evidence that ∼80% of the boron atoms are in tetrahedral coordinated. A super macro tetrahedron, B₁₀S₁₈⁻⁶ is proposed as one of the structures in these glasses in which can account for the apparent low fraction of Li₂S present in the B₂S₃ sub-network while at the same time enabling the high fraction of tetrahedral borons in the glass.     

Structural and magnetic properties of a syn-anti carboxylate bridged one-dimensional copper(II) complex with ferromagnetic exchange interaction

The compound [Cu(phen)(O₂CCF₃)₂]_n (phen = 1,10-phenanthroline) has been synthesized and its crystal structure determined. It crystallizes in monoclinic space group C2/c, with a = 19.229(7), b = 11.281(5), c = 7.621(2) Å, = 104.305(12)°, and Z = 4. The crystal structure is polymeric, being built from infinite zigzag chains of trifluoroacetate bridged copper(II), with the phenanthroline ligands being stacked between the chains. The variable-temperature (13–300 K) magnetic susceptibility and ESR data are reported and a weak ferromagnetic exchange interaction is observed with the exchange parameter estimated as J = 2.9 cm^–1.     

Structure and magnetic properties of lead vanadate glasses

X-ray photoelectron spectroscopy (XPS) has been used to obtain structural information on the xPbO · (1−x)V₂O₅ glass system where x=0.22, 0.35, 0.43, and 0.54. The binding energies from the Pb 4f_7/2 and Pb 4f_5/2 core levels decrease with increasing PbO content while the full-width at half-maximum of these peaks increase. The O 1s spectra show an asymmetry for samples having composition x<0.5, which results from oxygen atoms in the V–O–V configuration (bridging oxygens) and from oxygen atoms in the V–O–Pb and Pb–O–Pb configurations (non-bridging oxygens). The number of non-bridging oxygens was found to increase from 81% to 92% with increasing PbO content. For x=0.54, the O 1s spectrum was symmetric indicating that all three oxygen configurations have essentially the same binding energy. This behavior in addition to the decreasing binding energies of the Pb 4f levels with increasing PbO content suggest that the Pb–O bonds are becoming more covalent in nature and that eventually PbO changed its role from a glass modifier to a glass former for x>0.5. The asymmetric V 2p_3/2 peaks for the x<0.4 glasses indicate the presence of a small concentration of V⁴⁺ ions in addition to V⁵⁺ ions, while the symmetric V 2p_3/2 peaks for the more concentrated PbO vanadate glasses indicate only V⁵⁺ being present. The concentration of V⁴⁺ ions (0–4%) from the XPS data is consistent with determinations from magnetic susceptibility measurements on the same glass samples. In addition to the paramagnetic contribution (Curie–Weiss temperature-dependent behavior) from the V⁴⁺ ions, the susceptibility for these oxide glasses consisted of a positive, constant contribution arising from the temperature-independent paramagnetic V₂O₅ exceeding the diamagnetism from the core ions.     

Phase diagrams and optical properties of binary liquid crystalline systems of cobalt (II) caprylate with lithium and lead caplylates

The concentration and temperature ranges of liquid crystal and glass formation in binary systems of cobalt (II) caprylate with either lithium or lead caplylates have been studied by differential thermal analysis and optical polarization microscopy. Absorption spectra of Co(II) cations in mesophases and glasses of these binary caprylate systems have been analyzed as a function of temperature and composition to get information on the coordination of Co(II) ions.For the binary system of lead–cobalt caprylate, we found that the Co(II) ions are octahedrally coordinated over the range of temperatures and compositions studied, whereas in the binary lithium–lead caprylate system, the Co(II) ions can exist in both octahedral and tetrahedral coordination depending on composition and temperature. Thermochromic behavior was observed for all compositions studied here, from blue to violet and pink, depending on the composition and temperature of the system studied. An unusual increase of optical density with decreased Co(II) ion concentration has been observed for the Co–Li caprylate binary system up to 50 mol%. An increasingly ionic Co(II) coordination environment as Li ion concentration increases facilitates a concomitant increase in the proportion of more optically dense tetrahedrally coordinated Co(II) ions.     

Synthetically tuned structural variations in coordination polymers based on dicyanamide toward diverse physical properties

Three new two-dimensional coordination polymers (CPs), {Ni[N(CN)₂]₂(H₂O)₂·2DMAC}_n for 1, {Ni[N(CN)₂]₂(DMAC)₂}_n for 2, and {Co[N(CN)₂]₂(DMSO)₂}_n for 3, have been synthesized with different synthetic methods. The crystallographic analysis indicates that CPs 1 and 3 crystallize in the monoclinic system with space group of P2₁/c, while CP 2 crystallizes in the orthorhombic system with space group of Pnma. CPs 1 and 3 exhibit the antiferromagnetic properties, while CP 2 shows the weak ferromagnetic property. The solid-state luminescence properties of CPs 1–3 have also been investigated. Compared with the dicyanamide, 1 and 2 show the blue shift with emission maximum around 310?nm, while CP 3 shows the band at 335?nm.     

Structure and lithium ion diffusion in lithium silicate glasses and at their interfaces with lithium lanthanum titanate crystals

Solid state lithium ion electrolytes are important to the development of next generation safer and high power density lithium ion batteries. Lithium containing glasses such as lithium silicate glasses have been widely studied due to their high ionic conductivity. Recently, lithium silicate glasses were introduced in polycrystalline lithium lanthanum titanate (LLT) ceramics as intergranular thin films between the crystalline grains to achieve higher lithium ion conductivities in these solid state electrolytes. In this work, we present investigations of the structure and diffusion behavior of lithium silicate glasses and their interfaces with LLT crystals using molecular dynamics simulations. The short and medium range structures of the lithium silicate glasses were characterized and the ceramic/glass interface models were obtained using MD simulations. Lithium ion diffusion behaviors in the glass and across the glass/ceramic interfaces, as well as the effect of atomic structure on diffusion behaviors, were investigated. It was found that there existed a minor segregation of lithium ions at the glass/crystal interface. The interface lithium ion diffusion energy barrier was found to be dominated by the glass phase.     

Structure and properties of cobalt(II) complex with a tetraaza macrocycle containing 2-pyridylmethyl pendant arms

The complex [Co(L)]Cl₂·10H²O (1) (L = 2,13,-bis(2-pyridylmethyl)-3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]docosane) has been synthesized and structurally characterized. Compound 1 crystallizes in the triclinic system, space group P-1 with a = 9.731(2) Å, b = 9.789(2) Å, c = 11.998(1) Å, = 66.66(1)°, = 76.95(1)°, = 87.99(2)°, V = 1020.4(3) ų, and Z = 1. The crystal structure of 1 shows that the complex is centrosymmetric and the cobalt(II) ion has a slightly distorted octahedral geometry with four nitrogen atoms of the macrocycle and two nitrogen atoms of the pendent arms at the axial positions. Cyclic voltammetry for 1 undergoes reversible one-electron oxidation to the Co(III) and irreversible one-electron reduction to the Co(I).     

Magnetic properties and sensitized visible and NIR luminescence of DyIII and EuIII coordination polymers by energy transfer antenna ligands

Two coordination polymers, {[Ln(2-stp)(4,4′-bipy)(H₂O)].(H₂O)}, [Ln = Dy (1) and Eu (2), 2-stp = 2-sulfoterephthalate and 4,4′-bipy = 4,4′-bipyridine] have been characterized by solid state UV-vis, FTIR spectra, X-ray single crystal diffraction and solid state photoluminescence. Variable-temperature magnetic susceptibility and isothermal magnetization as function of external magnetic field is also studied for both complexes. After ligand-mediated excitation, both complexes show the characteristic visible and NIR luminescence of the corresponding Ln^III ions (Ln = Dy, Eu) which is due to efficient energy transfer from the ligands to the central Ln^III ions via an antenna effect. The indirect energy transfer in both complexes has been investigated and discussed in detail.     

The use of carborane anions in coordination polymers and extended solids

The use of carboranes as counter-anions for metal-organic frameworks or coordination polymers is reviewed. While carboranes are weakly coordinating they can form interactions to Ag(I) as well as other metal centers. Thus carboranes may have one of a number of roles in transition metal networks: as a non-coordinating templating counter-anion; as a bulky terminal ligand, and thus topologically trivial but likely to be structure-directing to some degree; or as a bridging ligand.     

Structure of lithium borate and strontium borate glasses with high modifier contents

The structure of lithium borate and strontium borate glasses with high Li₂O and SrO contents was examined using the experimental results of ESR and the optical absorption of Cu²⁺ ions, and the Mössbauer spectra of Fe³⁺ ions and Raman spectra of these glasses. The results indicate the existence of non-bridging oxygens belonging to orthoborate and pyroborate groups, structural groups of diborate and high pressure forms of metaborate above 30 mol% of the modifier contents in these glasses. Among these four structural groups, the diborate group rapidly decreased with an increase of the modifier contents, while the other three groups increased with an increase of the modifier contents.     

Structural and physical properties of cobalt nanocluster composite glasses

Composite systems with metallic nanoparticles embedded in dielectrics present peculiar physical properties which are attractive in several application fields. In the case of transition elements, the magnetic properties of the metal clusters embedded in a dielectric matrix mainly depend on the particle size and structure. In this work, silica films containing cobalt atoms were synthesized by RF magnetron co-sputtering deposition technique, with cobalt concentration of a few atomic percent. X-ray diffraction and transmission electron microscopy showed the presence of hcp cobalt nanoclusters in the as-deposited sample with the highest cobalt concentration. After deposition, thermal treatments were performed to promote cobalt compounds or nanoparticle formation. The thermal treatments were able to change the oxidation state of cobalt atoms, as well as the structure of metallic cobalt nanoclusters (from hcp to fcc), their final size depending on both the preparation parameters and the subsequent annealing atmospheres.     

Structure and self-assembly synthesis of a novel heterometallic one-dimensional coordination polymer: {[Cu(II)(DETA)I·DMF]2[Pb2I6]} n

A novel organic–inorganic hybrid coordination polymer {[Cu(II)(DETA)I·DMF]₂[Pb₂I₆]} _n (DETA = diethylene triamine, DMF = N,N′-dimethyl formamide) was synthesized by the reaction of CuSO₄·6H₂O, DETA, Pb(NO₃)₂ and NaI in DMF/H₂O mixed solvent at room temperature. Structural characterization of X-ray single diffraction reveals that the polymeric negative chain [Pb₂I₆] _n ²⁻ is built up by face-sharing of PbI₆ octahedrons. Upon the hydrogen bonds interaction between N–H···I and N–H···O, structure-directing reagent chain {[Cu(II)(DETA)I·DMF]₂} _n ²⁺ presents one-dimension arrangement. Structure-directing reagent chains and polymeric negative chains are in combination with each other by static attracting force to form the so-called hybrid structure. The title compound was further characterized by IR, EA, UV-Vis and fluorescence spectrum.     

Kinetics and binding properties of cloramphenicol imprinted polymers

Molecularly imprinted polymers (MIPs) are easily obtained by a non-covalent approach through the copolymerisation of suitable functional monomers and cross-linkers in the presence of the print molecule. Removal of the template leaves a polymer that selectively recognises it. However, experimental data have demonstrated that non-covalent molecularly imprinted polymers exhibit a heterogeneous binding sites distribution. In this work, two different imprinted polymers for chloramphenicol (CAP), obtained using different template concentrations, were evaluated for their kinetics and affinity binding properties against CAP in a batch approach. Experimental binding isotherms were fitted to Langmuir, Freundlich and Langmuir–Freundlich isotherms and the affinity distribution corresponding to the Freundlich isotherm was used to extract binding parameters. Parallel studies were performed for the binding of chloramphenicol diacetate to the CAP-imprinted polymers.     

Magnesium-doped potassium lithium niobate crystal and its properties

High quality magnesium-doped potassium lithium niobate (designated as KLN:Mg) single crystal was grown for the first time. The tetragonal tungsten bronze structure of the Mg:KLN crystal was determined by X-ray powder diffraction, in which the lattice parameters were A=1.262nm and C=0.398nm. High temperature X-ray diffraction patterns showed that the expansion of the lattice with increasing temperature was less than that of the undoped crystal. The transmittance of the as-grown crystal was measured. It increased by 80% from the cutoff wavelength 380nm to 450nm. The transmittance for 404nm was 50%, which is larger than that of the undoped crystals. The frequency-doubling property of KLN crystal was analyzed. Preliminary frequency doubling experiments showed that the crystal could generate blue light of 404nm through noncritical phase matching (NCPM) second harmonic generation (SHG) using a 808nm diode laser at room temperature.     

Nonlinear optical properties of lithium sulfate monohydrate

In this paper, all eight tensor components of the nonlinear optical susceptibility tensor for second harmonic generation were determined for monoclinic non‐centrosymmetric lithium sulfate monohydrate, Li₂SO₄·H₂O, using the Maker fringe technique at the wavelength λ=1064 nm. The largest component of the nonlinear optical susceptibility tensor was 0.34 pm/V. This crystal has the maximum effective value 0.13 pm/V along the phase matching directions at type I and 0.10 pm/V at type II. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural and optical properties of lithium barium bismuthate glasses

Structural and optical properties of some ion-conducting lithium barium bismuthate glasses have been studied. The structure of these glasses has been explored from the compositional variation of the density, the molar volume and the glass transition temperature. The density and the molar volume decrease with the increase of lithium ion content in these glasses keeping the barium content fixed. The optical studies in the ultraviolet–visible (UV–VIS) and infrared (IR) regions for all these glasses show a sharp cut-off and a large transmitting window, which make them appealing candidates for the different spectral devices.     

The preparation and properties of cerium-activated lithium glass scintillators

We report the preparation of cerium activated lithium glass scintillators for thermal neutron detection and their properties. The technological requirements and appropriate compositions are proposed, by which high detection efficiency of lithium glass scintillators for thermal neutrons can be obtained. When used as neutron detectors, the ⁶Li glass ST-602 affords excellent pulse height discrimination against gamma radiation, particularly in the case of thin ⁶Li glass.     

Mechanical properties of single crystalline and glassy lithium triborate

Mechanical properties of LiB₃O₅ single crystal plates with different orientation as well as of glass with the same composition have been investigated. The nano‐ (H) and microhardness (H_M), the reduced Young's modulus (E_r) and the crack behaviour of the samples were studied. Both hardness and Young's modulus of glass appeared smaller in comparison to corresponding single crystal data (H ∼ 7 – 8 GPa, H_M ∼ 6 GPa, E_r ∼ 70 – 80 GPa for glass and H ∼ 10 – 15 GPa, H_M ∼ 6 –11 GPa, E_r ∼ 93 – 155 GPa for single crystal). H, E_r, and the plane of crack propagation proved orientation‐dependent. Cracks in the glass sample were not observed up to 0.49 N microindentation load, whereas for the single crystal the cracks appeared already at 0.098N. In single crystals the observed cleavage planes {211} and/or {412} are oriented nearly parallel to planes of B‐O rings. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)