Fluorescence Enhancement of Rare Earths by Yttrium and its Application

Abstract

A study of the enhancement effect on the fluorescence intensity of the Eu³⁺–-thenoyltrifluoroacetone (TTA)–-cetyltri–-methylammonium bromide (CTMAB) and the Dy³⁺ pyrocatechol–-3,5-disulphonic acid (Tiron) systems by Y³⁺has been carried out. In the presence of yttrium the fluorescence intensity of the systems was enhanced by a factor of about 100 and 15, respectively. The fluorescence intensity was a linear function of the concentration of europium or dysprosium in the range 1.0 × 10^?10–-1.0 × 10^?8mol dm^?3 and 8.0 × 10^?8–-9.0 × 10^?6mol dm^?3, respectively. The detection limit was 1.0 × 10^?11mol dm^?3 and 1.0 × 10^?10mol dm^?3, respectively. The standard addition method was used for the determination of europium or dysprosium in rare earth oxides and gave satisfactory results. The mechanism of enhanced fluorescence was proposed.     

Coherent Raman and Infrared Studies of Sulfur Trioxide

High-resolution (0.001 cm⁻¹) coherent anti-Stokes Raman scattering (CARS) was used to observe the Q-branch structure of the IR-inactive ν₁ symmetric stretching mode of ³²S¹⁶O₃ and its various ¹⁸O isotopomers. The ν₁ spectrum of ³²S¹⁶O₃ reveals two intense Q-branches in the region 1065–1067 cm⁻¹, with surprisingly complex vibrational–rotational structure not resolved in earlier studies. Efforts to simulate this with a simple Fermi-resonance model involving ν₁ and 2ν₄ states do not reproduce the spectral detail, nor do they yield reasonable spectroscopic parameters. A more subtle combination of Fermi resonance and indirect Coriolis interactions with nearby states, 2ν₄(1=0, ±2), ν₂+ν₄(1=±1), 2ν₂(1=0), is suspected and a determination of the location of these coupled states by high-resolution infrared measurements is under way. At medium resolution (0.125 cm⁻¹), the infrared spectra reveal Q-branch features from which approximate band origins are estimated for the ν₂, ν₃, and ν₄ fundamental modes of ³²S¹⁸O₃, ³²S¹⁸O₂¹⁶O, and ³²S¹⁸O¹⁶O₂. These and literature data for ³²S¹⁶O₃ are used to calculate force constants for SO₃ and a comparison is made with similar values for SO₂ and SO. The frequencies and force constants are in excellent agreement with those obtained by Martin in a recent ab initio calculation.     

Formation of Cr(II) Species in the H2/CrO3 System. Parameter control

The thermal behaviour of CrO₃ on heating up to 600°C in dynamic atmospheres of air, N₂ and H₂ was examined by thermogravimetry (TG), differential thermal analysis (DTA), IR spectroscopy and diffuse reflectance spectroscopy (DRS). The results revealed three major thermal events, depending to different extents on the surrounding atmosphere: (i) melting of CrO₃ near 215°C (independent of the atmosphere), (ii) decomposition into Cr₂(CrO₄)₃ at 340–360°C (insignificantly dependent), and (iii) decomposition of the chromate into Cr₂O₃ at 415–490°C (significantly dependent). The decomposition CrO₃ → Cr₂(CrO₄)₃ is largely thermal and involves exothermic deoxygenation and polymerization reactions, whereas the decomposition Cr₂(CrO₄)₃ → Cr₂O₃ involves endothermic reductive deoxygenation reactions in air (or N₂) which are greatly accelerated and rendered exothermic in the presence of H₂. TG measurements as a function of heating rate (2–50°C min⁻¹) demonstrated the acceleratory role of H₂, which extended to the formation of Cr(II) species. This could sustain a mechanism whereby H₂ molecules are considered to chemisorb dissociatively, and then spillover to induce the reduction. DTA measurements as a function of the heating rate (2–50°C min⁻¹) helped in the derivation of non-isothermal kinetic parameters strongly supportive of the mechanism envisaged. This revised version was published online in August 2006 with corrections to the Cover Date.     

Growth of pure and RE-doped Y2O3 single crystals by LHPG technique

High-quality and crack-free Y₂O₃ single crystals containing low concentrations of Tm³⁺, Tb³⁺ and Yb³⁺ were obtained. The crystals were grown in the form of monocrystalline fibers by using a floating zone method with laser heating (laser-heated pedestal growth).     

用复相光催化剂WO3/α-Fe2O3/W深度处理造纸废水的研究

采用光催化法对造纸废水的处理进行了研究.探讨了光催化反应机理,比较了光催化剂的活性顺序,讨论了复相光催化剂的组成、用量、试液pH值、光照时间与COD、色度去除率的关系.实验结果表明:采用WO₃/α-Fe₂O₃/W为复相光催化剂,其组成为WO₃:α-Fe₂O₃:W＝75:24:1,当其用量为0.500g、pH＝6.5、光照22h,造纸废水的COD和色度去除率分别达到68.3%和71.2%.     

Xenon Trioxide Adducts of O-Donor Ligands; [(CH3)2CO]3XeO3, [(CH3)2SO]3(XeO3)2, (C5H5NO)3(XeO3)2, and [(C6H5)3PO]2XeO3

Xenon trioxide (XeO₃) forms adducts with triphenylphosphine oxide, dimethylsulfoxide, pyridine-N-oxide, and acetone by coordination of the ligand oxygen atoms to the Xe^VI atom of XeO₃. The crystalline adducts were characterized by low-temperature, single-crystal X-ray diffraction, and Raman spectroscopy. Unlike solid XeO₃, which detonates when mechanically or thermally shocked, solid (C₅H₅NO)₃(XeO₃)₂, [(C₆H₅)₃PO]₂XeO₃, and [(CH₃)₂SO]₃(XeO₃)₂ are insensitive to mechanical shock. The [(CH₃)₂SO]₃(XeO₃)₂ adduct slowly decomposes over several days to (CH₃)₂SO₂, Xe, and O₂. All three complexes undergo rapid deflagration when ignited by a flame. Both [(C₆H₅)₃PO]₂XeO₃ and (C₅H₅NO)₃(XeO₃)₂ are room-temperature stable and the [(CH₃)₂CO]₃XeO₃ complex dissociates at room temperature to form a stable solution of XeO₃ in acetone. The xenon coordination sphere of [(C₆H₅)₃PO]₂XeO₃, a distorted square-pyramid, provides the first example of a five-coordinate XeO₃ complex with only two Xe- - -O adduct bonds. The xenon coordination spheres of the remaining adducts are distorted octahedra, comprised of three Xe- - -O secondary bonds that are approximately trans to the primary Xe−O bonds of XeO₃. Quantum-chemical calculations were used to assess the nature of the Xe- - -O adduct bonds, which are described as predominantly electrostatic bonds between the nucleophilic oxygen atoms of the bases and the σ-holes of the electrophilic xenon atoms.     

Highly efficient enrichment and adsorption of rare earth ions (yttrium(III)) by recyclable magnetic nitrogen functionalized mesoporous expanded perlite

A magnetic mesoporous expanded perlite-based (EP_d-APTES@Fe₃O₄) composite was designed and synthesized as a novel adsorbent for enrichment of rare earth ions in aqueous solution. Effect of various factors including the pH of solution, contact time and adsorbent dosage on the adsorption behaviors of yttrium(III) by the EP_d-APTES@Fe₃O₄ nano-material composites from aqueous solution was investigated. The maximum adsorption capacity of the as-prepared materials for yttrium(III) ions was 383.2 mg/g. Among the various isotherm models, the Freundlich isotherm model could well described for the adsorption of the rare earth ions at pH 5.5 and 298.15 K. The kinetic analysis indicated that the adsorption process followed the pseudo-second order kinetics model, and the rate-determining step might be chemical adsorption. Thermodynamic parameters declared that the adsorption process was endothermic. In addition, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and the quantum chemical calculation indicated that the yttrium(III) ions were captured on the EP_d-APTES@Fe₃O₄ surface mainly by coordination with functional group of -NH₂. More importantly, the adsorption-desorption studies indicated that the EP_d-APTES@Fe₃O₄ nano-material composites had a high stability and good recyclability.     

直流等离子体-中阶梯光栅光谱仪测定高纯氧化镧、氧化钇中稀土杂质

本文采用中阶梯光栅光谱仪,直流等离子体光谱法测定高纯(99.99%)氯化镧、氧化钇中稀土杂质元素,由于仪器具有很高的色散率,因而方法具有灵敏度高、干扰少的特点。     

Peculiarities of the vortex dynamics in YBa2Cu3Ox single crystals as revealed by irreversible microwave absorption

We report the results of a wide experimental study of the irreversible modulated microwave absorption as a function of temperature, applied magnetic field and modulation amplitude in the YBa₂Cu₃O_x single crystals. To analyze the experimental data the model of the microwave power dissipation by the flux lines has been developed taking into account thermal fluctuations, the distributions of currents and vortices over a sample. We have obtained the information about regimes of vortex motion in the different areas of the H–T phase diagram and estimated the values of flux flow viscosity and critical current density.     

Chemiluminescence in the reduction of XeO3 by europium(II)

Chemiluminescence has been observed in the reduction of perchloric aqueous solutions of XeO₃ with Eu²⁺ ions, Fast (several seconds) consumption of Eu^II occurs when the ratio of the initial concentrations of the reactants (Eu²⁺]₀ : [XeO₃]₀ < 6; however, the chemiluminescence remains sufficiently bright and prolonged (up to –10 min after nearly complete oxidation of Eu^II to Eu^III). The assumption was made that intermediates in the reduction of XeO₃ participate in the chemiluminescent stages of the process.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2909–2911, December, 1996.