1.3-μm-emission properties and local structure of Dy3+ in chalcohalide glasses

Spectroscopic properties and local structure of rare-earth ions in Ge–Ga–S glasses with the addition of alkali halides were investigated. The intensity of the 1.31-μm emission from Dy³⁺ (⁶F_11/2·⁶H_9/2 → ⁶H_15/2) increased sharply when the appropriate amount of alkali halides was added, at the expense of the 1.75-μm emission intensity (⁶H_11/2 →⁶H_15/2). The lifetimes of the 1.31-μm emission level also increased as much as 35 times from 38 μs for Ge–Ga–S glass (0.1 at.% Dy³⁺) to 1320 μs for glass containing 10 mol% of CsBr. These enhancements occurred only when the ratio of MX(M = K,Cs and X = Br, I)/Ga was equal to or larger than unity. Phonon side band (PSB) showed that the several local phonon modes, with the frequencies around 100 cm^–1, were coupled to 4f electrons of Eu³⁺. The nearest neighbors of Eu³⁺ ions are composed of halogen ions that are part of well-structured complex such as EuCl₃, tetrahedral 〚GaS_3/2Cl〛^– subunit and/or Ga₂Cl₆. A small amount of As was added to increase the resistivity against the recrystallization during re-heating. The best composition for practical usage was 0.7 〚Ge_0.25As_0.10S_0.65〛–0.15 GaS_3/2–0.15 CsBr. This glass also exhibited high resistance against the attack of liquid water and is therefore a potential material for efficient fiber-optic amplifiers.     

Luminescence of RE~(3+) and energy transfer from Gd~(3+) to RE~(3+) (RE = Dy, Eu) in SrGdAlO_4:RE~(3+)

Spectral properties of Gd3+, Dy3+ and Eu3+ ions in SrGdAlO4 are reported in detail. A cooperative vibronic transition of Gd3+ and the emission from the higher 5DJ (J=1, 2, 3) levels of Eu3+ were observed. Energy transfer occurs from Gd3+ to Dy3+ and to Eu3+. The influence of Gd3+ and Dy3+ concentrations on the luminescence intensity is discussed.     

Spectroscopic properties and luminescence concentration quenching of the Pr3+ ion in La1−xPrxOCl

Luminescence spectra ofLa_1−xPr_xOCl(0.01 ≤ x ≤ 0.3) were recorded at liquid helium and room temperature. From these spectra, the energy level diagram of Pr³⁺ in LaOCl was deduced. The decay times of the Pr³⁺ emission in La_1−xPr_xOCl were measured using a high-resolution dye laser system. The linear concentration quenching and exponential decay times are explained assuming cross relaxation and energy transfer between the Pr³⁺ ions.     

Synthesis of palladium–polypyrrole nanocomposite and its electrocatalytic properties in the oxidation of formaldehyde

Three alternative methods were developed for the synthesis of modifying palladium–polypyrrole layers on the surface of an inert electrode. Their electrocatalytic activity toward formaldehyde under inert atmosphere was checked. All the suggested methods are one-stage and allow synthesis of a film on the electrode surface from a solution containing a palladium salt and pyrrole in the absence of other active reagents. The electrochemical methods (potentiodynamic and double cathodic and anodic pulses techniques) in an aqueous medium give films with poorly reproducible electrocatalytic properties, while the chemical redox synthesis affords films with reproducibly high electroactivity toward methylene glycolate.     

Synthesis,structure and photoluminescence properties of Ho3+ doped TTB–BaTa2O6 phosphors

Ho³⁺ doped TTB–BaTa₂O₆ phosphors were produced by the solid state reaction method. XRD analysis confirmed the formation of BaTa₂O₆ single phase which was accomplished by heat treatment at 1425 °C for 20 h. The crystal structure of TTB–BaTa₂O₆ allowed doping concentration of Ho³⁺ ions up to 10 mol%, maintaining a single phase composition. A second phase of HoTaO₄ begins to appear at 15 mol%. The lattice structure and the crystallite sizes changed with the concentration of Ho³⁺. In SEM analysis, it was also shown that BaTa₂O₆ grain sizes changed with the concentration of Ho³⁺. EDS analysis revealed that the Ta/Ba ratio increased on the grains depending on Ho³⁺ concentration. Charge balance of the structure was formulated through the EDS results. In fluorometer analysis, a strong green emission (λ_em = 546.9 nm) was observed in the visible spectral region. The emission increased with the doping concentration of up to 2.5 mol%, and above this level decreased due to concentration quenching.     

Synthesis and thermal properties of NiSbS–As doped phase

The substitution of Sb with As in the NiSbS intermetallic compound was studied in the framework of evaluating a possible increase of the thermoelectric properties. Different NiSb_1?xAs_xS samples were synthesized with increasing amounts of As (0 < x < 0.66) employing a simple synthetic route using a muffle furnace. Scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy was used to investigate the microstructure. X-ray powder diffraction techniques were employed in order to study the possible existence of a solid solution between NiSbS and NiAsS compounds, as well as to identify the crystal structure and determine the lattice parameters. All compounds were found to crystallise with the NiSbS prototype (cP12-P2₁3), with lattice parameters varying from a = 0.59341(7) nm (x = 0) to a = 0.56849(6) nm (x = 1). Good agreement with Vegard’s law was evidenced. Thermal measurements on NiSb_1?xAs_xS samples were carried out using DTA instruments to evaluate the thermal stability and the melting temperatures.     

Synthesis and properties of zinc–nickel–carbon nanotube composite coatings

Composite electrochemical coatings modified with carbon nanotubes were produced on the basis of the zinc–nickel alloy. The functional properties (friction coefficient, protective capacity) of the composite coatings were studied in comparison with zinc–nickel alloys without a dispersed phase. It was found that, upon inclusion of carbon nanotubes particles into zinc–nickel deposits, their sliding friction coefficient decreases by a factor of 1.3–1.4 and the range of passive-state potentials becomes two times wider.     

Electrochemical properties and extraction of Dy on liquid Sn electrode in LiCl–KCl molten salt

Journal of Solid State Electrochemistry - To extract dysprosium (Dy) from LiCl–KCl molten salt, the electrochemical properties of Dy on liquid Sn electrode were explored by various...     

Luminescence and energy transfer of Ce~(3+) and Dy~(3+) in BaLaB_9O_(16)

Under the excitation of UV light, the composition dependence of luminescence properties of Ce3+ and Dy3+ in BaLaB9O16 has been studied. The mechanisms of energy transfer from Ce3+ to Dy3+ and of concentration quenching of Dy3+ emission under the excitation of UV light have been presented as well.     

Synthesis and properties of double copper(I)–nickel(II) sulfite

Pourbaix diagrams of Cu–H₂SO4–H₂O and Ni–H₂SO₄–H₂O systems have been refined, and stability regions of the sulfite phases have been determined. State diagrams of double copper(I)–copper(II) and copper(I)–nickel(II) sulfites have been constructed. Double copper(I)–nickel(II) sulfite has been isolated from aqueous solutions saturated with sulfur dioxide. The solutions at different ratios of the metals have been studied by spectrophotometry; the isolated double sulfite has been studied by X-ray diffraction, IR spectroscopy, dispersion analysis, and thermal analysis. Fundamentals of thermodynamic prognostication of the Cu₂SO₃·MSO₃ double sulfites synthesis have been elaborated.     

Synthesis and some properties of a new compound in the Al–Sb–V–O system

A new compound in the Al?CSb?CV?CO system of the composition AlSbVO₆ was successfully synthesized by a solid-state reaction and characterized by powder XRD diffraction. The structural and thermal properties of AlSbVO₆ were investigated. The infra-red spectrum of the new phase is presented.     

Synthesis and properties of Co–Pt alloy silica core-shell particles

This paper describes a method for fabrication of silica-coated Co–Pt alloy nanoparticles in a liquid phase process. The Co–Pt nanoparticles were prepared from CoCl₂ (4.2 × 10⁻⁵ M), H₂PtCl₆ (1.8 × 10⁻⁵ M), citric acid (4 × 10⁻⁴ M) and NaBH₄ (1.2 × 10⁻² M) with a Co:Pt mole ratio of 7:3. The silica coating was performed in water/ethanol solution with a silane coupling agent, 3-aminopropyltrimethoxysilane (8 × 10⁻⁵ M), and a silica source, tetraethoxyorthosilicate (7.2 × 10⁻⁴ M) in the presence of the Co–Pt nanoparticles. Observations with a transmittance electron microscope and a scanning transmission electron microscope revealed that the Co-rich and Pt-rich nanoparticles were coated with silica. According to X-ray diffraction measurements, core particles were crystallized to metallic Co crystallites and fcc Co–Pt alloy crystallites with annealing in air at 300–500 °C. Magnetic properties of the silica-coated particles were strongly dependent on annealing temperature. Maximum values of 11.4 emu/g-sample for saturation magnetization and 365 Oe for coercive field were obtained for the particles annealed at 300 and 500 °C, respectively. Annealing at a temperature as high as 700 °C destroyed the coating structures because of crystallization of silica shell, resulting in reduction in saturation magnetization and coercive field.     

Synthesis and glycosidase inhibition properties of triazole-linked calixarene–iminosugar clusters

Calixarene–iminosugar derivatives bearing four 1-deoxynojirimycin units at the upper or lower rim of calix[4]arenes in a fixed cone conformation were synthesized by copper-catalyzed azide-alkyne cycloaddition (CuAAC) and their inhibitory activity was evaluated against five glycosidases. Modest but significant affinity enhancements of up to seven per 1-deoxynojirimycin unit over the monovalent iminosugar derivative were observed for the inhibition of Jack bean (Canavalia ensiformis) α-mannosidase. It was also demonstrated that the residual copper ions did not contribute to the inhibitory properties of the newly prepared calixarene-based multivalent iminosugars.     

Synthesis and magnetic properties of an iminonitroxide-substituted phenolate–Cu complex

A new spin-chelate, iminonitroxide-substituted phenolate–copper complex (1), was designed and prepared. The structure of the complex 1 was considerably deviated from a square-planar geometry. The dihedral angle between the two planes defined by a set of copper, oxygen and nitrogen atoms was about 41°. The complex was found to have a relatively strong ferromagnetic interaction and a weaker antiferromagnetic interaction: J/k_B=+250 K and θ=−17 K using a three-spin model. The ferromagnetic interaction was assigned to the intramolecular interaction between the copper atom and the iminonitroxide. The antiferromagnetic interaction was assigned as an intermolecular interaction. These assignments were supported by susceptibility measurements for the diluted sample in polyvinyl chloride (PVC) film. The antiferromagnetic interaction was tentatively assigned due to the observed short intermolecular contacts between the C5 and O1 atoms or between the H5 and O1 atoms.     

Synthesis and properties of organic–inorganic hybrid liquid crystal gels

Organic–inorganic hybrid liquid crystal (LC) gels have been synthesised by the thiol-ene reaction of a multifunctional cyclic siloxane, 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (TVMCTS) and alkane dithiols, 1,6-hexanedithiol (HDT) or 1,9-decanedithiol (DDT), in LC matrices, 4-cyano-4?-pentylbiphenyl (5CB) or 4′-n-octyl-4-cyano-biphenyl (8CB). The LC gels were prepared in an isotropic phase at 70°C or mesophases at 25°C using radical initiators. The phase transition temperatures from a mesophase to an isotropic phase of the resulting gels were lower than those of the original LCs. The gels containing 8CB (8CB gels) prepared at 25°C showed two phase transitions: smectic-to-nematic and nematic-to-isotropic transitions. By contrast, the 8CB gels synthesised in the isotropic phase showed only one phase transition from smectic phase directly to isotropic phase. Reaction conversions in the LC gels prepared at 70°C were higher than that in the gels prepared at 25°C. Scanning microscopic light scattering analysis of the LC gels cleared homogeneous small size mesh with a small amount of large defect. Polarisation micrographs of the LC gels showed framed optical textures derived from the LC molecules at room temperature. The LC gels containing more than 90 wt% of LC showed electro-optic response.     

Synthesis and properties of covalently linked BF2–oxasmaragdyrin–porphyrin dyads and triad

Two covalently linked diphenyl ethyne bridged unsymmetrical dyads containing porphyrin and BF₂–oxasmaragdyrin and Zn(II)porphyrin and BF₂–oxasmaragdyrin units and one covalently linked triad containing Zn(II)porphyrin, porphyrin and BF₂–oxasmaragdyrin units were synthesized by coupling appropriate functionalized macrocycles under Pd(0) coupling reaction conditions. The dyads and triad were freely soluble in common organic solvents and confirmed by ES-MS spectra. 1D and 2D NMR techniques were used to characterize the dyads and triad. Absorption and electrochemical studies of dyads and triad showed the overlapping features of the constituted macrocycles indicating that the macrocycles retain their basic features in the dyads and triad. The BF₂–oxasmaragdyrin absorbs at lower energy and emits strongly in the visible region compared to porphyrin/Zn(II)porphyrin. Thus, BF₂–oxasmaragdyrin acts as energy acceptor and porphyrin/Zn(II) porphyrin act as energy donor in dyads and triad. The steady state and time-resolved fluorescence studies supported an efficient energy transfer from porphyrin/Zn(II)porphyrin to BF₂–oxasmaragdyrin unit in dyads and triad.     

Synthesis and properties of trifluoromethylating steroid compounds

Trifluoromethyl steroids la,b; 2a,b; 3a,b have been synthesized by starting from estren 3,17-dicarbonyl-3,3-dimethyl ether (4) and dl-18-methyl-2(3)l5(10)-estra-diene-17-carbonyl-3-methyl ether (5),and by using trimthyltrifluoromethylsilane as the trifluoromethylating agent under the catalysis of tetrarnethylam-monium fluoride.The overall yields were 82%,76%; 54%,62%; and 27%,25%,respectively The α-configura tion of trifluoromethyl group of 17-position was determined by X-ray crystal diffraction method Compounds 1a,2a and 3a showed high affinity for rat uterus PRc.The test of biological activities of compounds 1b,2b and 3b is proceeding.