原位水解-硝酸镧电位滴定法测定钛合金化铣腐蚀溶液中总氟化物

基于氟钛配合物的原位水解以及硝酸镧电位滴定法建立了测定钛合金化铣腐蚀溶液中总氟化物浓度的新方法。在六次甲基四胺(HMTA)缓冲溶液中,氟钛配合物发生原位水解并释放出游离氟离子,以氟离子选择电极(F-ISE)为指示电极进行测定。对影响测定的各项参数(如p H值、HMTA溶液用量、钛离子浓度等)做了条件实验并予以优化。实验结果表明Ti(Ⅳ)浓度在0~20 g/L范围内对于氟离子测定无干扰,方法的相对标准偏差(RSDs,n=6)在0.27%~0.62%之间,加标回收率在99.5%~101.1%之间。此外,本文对氟钛配合物原位水解反应的机理也进行了探讨,溶液中氟钛配合物的主要存在形式为TiF_6~(2-),适宜的酸度是水解反应进行的必要条件,HMTA作为缓冲溶液为水解反应持续进行提供恒定的p H环境,La(NO_3)_3作为氟清除剂降低游离氟离子浓度促进水解反应的进行,伴随滴定过程氟钛配合物发生完全水解。     

Dinuclear neodymium and lanthanum bis(2,6‐diisopropylphenyl) phosphate complexes bearing a hydroxide ligand: catalytic activity of the Nd complex in 1,3‐diene polymerization

The reactions of K[(2,6‐ⁱPr₂C₆H₃‐O)₂POO] either with LaCl₃(H₂O)₇ or with Nd(NO₃)₃(H₂O)₆ in a 3:1 molar ratio, followed by vacuum drying and recrystallization from alkanes, have led to the formation of diaquapentakis[bis(2,6‐diisopropylphenyl) phosphato]‐μ‐hydroxido‐dilanthanum hexane disolvate, [La₂(C₂₄H₃₄O₄P)₅(OH)(H₂O)₂]·2C₆H₁₄, ( 1 )·2(hexane), and tetraaquatetrakis[bis(2,6‐diisopropylphenyl) phosphato]‐μ‐hydroxido‐dineodymium bis(2,6‐diisopropylphenyl) phosphate heptane disolvate, [Nd₂(C₂₄H₃₄O₄P)₄(OH)(H₂O)₄]·2C₆H₁₄, ( 2 )·2(heptane). The compounds crystalize in the P2₁/n and P space groups, respectively. The diaryl‐substituted organophosphate ligand exhibits three different coordination modes, viz. κ²O,O′‐terminal [in ( 1 ) and ( 2 )], κO‐terminal [in ( 1 )] and μ₂‐κ¹O:κ¹O′‐bridging [in ( 1 ) and ( 2 )]. Binuclear structures ( 1 ) and ( 2 ) are similar and have the same unique Ln₂(μ‐OH)(μ‐OPO)₂ core. The structure of ( 2 ) consists of an [Nd₂{(2,6‐ⁱPr₂C₆H₃‐O)₂POO}₄(OH)(H₂O)₄]⁺ cation and a [(2,6‐ⁱPr₂C₆H₃‐O)₂POO]⁻ anion, which are bound via four intermolecular O—H…O hydrogen bonds. The molecular structure of ( 1 ) displays two O—H…O hydrogen bonds between OH/H₂O ligands and a κ¹O‐terminal organophosphate ligand, which resembles, to some extent, the `free' [(2,6‐ⁱPr₂C₆H₃‐O)₂POO]⁻ anion in ( 2 ). NMR studies have shown that the formation of ( 1 ) undoubtedly occurs due to intramolecular hydrolysis during vacuum drying of the aqueous La tris(phosphate) complex. Catalytic experiments have demonstrated that the presence of the coordinated hydroxide anion and water molecules in precatalyst ( 2 ) substantially lowered the catalytic activity of the system prepared from ( 2 ) in butadiene and isoprene polymerization compared to the catalytic system based on the neodymium tris[bis(2,6‐diisopropylphenyl) phosphate] complex, which contains neither OH nor H₂O ligands.     

掺铒硼酸钙镧晶体的合成、生长及光谱特性

本文合成并以CaO-L i2O-B2O3为助熔剂体系生长得到了掺铒硼酸钙镧(Er3 :La2CaB10O19,Er:LCB)的晶体。X射线粉末衍射分析表明,Er:LCB和LCB具有相同的晶体结构,均属于单斜晶系,C2空间群。Er:LCB晶体的熔点大约为1048℃。测试了Er:LCB晶体的吸收光谱和荧光光谱。Er:LCB晶体在790nm和970nm附近存在的吸收,对应于A lGaAs和InGaAs激光二极管输出波长,其吸收截面分别为1.94×10-20和2.39×10-20cm2。Er:LCB在1531nm附近有发射峰最强,峰宽为16nm。其荧光寿命为0.37m s。     

微波辅助溶胶-凝胶法合成镧掺杂钛酸钡纳米微粉

以乙酸钡、钛酸四丁酯为原料,采用微波辅助溶胶-凝胶法制备La3＋掺杂钛酸钡,通过物相分析、电镜分析、红外分析及电化学分析等手段,研究其晶胞结构与电化学性能的改变. XRD分析表明：La3＋掺杂可以增大钛酸钡的晶胞体积、晶格常数a.扫描电镜分析显示：样品直径约50～200纳米的颗粒,为更小的粒子团聚而成,粒径不均匀,有团聚.红外光谱分析表明：制得的样品具有钙钛矿的钛氧八面体结构.电化学分析表明：La3＋掺杂的钛酸钡可以增大钛酸钡的储电性能,随着La3＋掺杂量的增大,储电量逐渐增加.当La3＋掺杂量达到0.002时,储电性能达到最优,随着La3＋掺杂量的增大,储电性能逐渐降低,但仍然比纯钛酸钡的储电性能好.     

稀土镧对重金属镉污染芥菜的生理生化活性的影响

利用土培方式研究芥菜在重金属镉与稀土镧的单一和复合作用下生理生化活性的变化,结果表明,镉在低浓度(小于4 mg/kg)时对芥菜生理活性影响不大,甚至有轻微的促进作用,而在高浓度时表现出强的胁迫作用;一定浓度范围的稀土镧能较好地促进芥菜的各项生理指标,且对镉的逆境胁迫有缓解作用。在镉的胁迫下,芥菜叶片叶绿素、可溶性蛋白、可溶性糖含量下降,Pro含量上升;在稀土镧的作用下,芥菜叶片叶绿素、可溶性蛋白、可溶性糖含量上升,Pro含量下降。     

Synthesis,Crystal Structure,and Photoluminescent and Semiconductive Properties of [La(C_6NO_2H_5)_3-(H_2O)_2]_(2n)·(nH_5O_2)(nHgCl_5)(2nHgCl_4)·(2nH_2O)

A new heterometallic 4f-5d inorganic-organic metal-isonicotinic acid complex [La(C6NO2H5)3(H2O)2]2n·(nH5O2)(nHgCl5)(2nHgCl4)·(2nH2O) 1 has been synthesized via hydro-thermal reaction and structurally characterized. Complex 1 crystallizes in the space group C2/c of monoclinic system with four formula units in a cell:a =24.140(7),b=20.884(7),c=15.462(2),β=127.46(1)°,V=6187(3)3,C36H47Cl13Hg3La2N6O20,Mr=2224.24,Dc=2.388 g/cm3,Z=4,T=293(2) K,μ(MoKα)=9.401 mm-1,F(000)=4160 and R/wR=0.0376/0.0636 for 4130 observed reflections (I > 2σ(I)) and 5617 unique reflections. Complex 1 is characteristic of a one-dimensional polycationic chain-like structure. Photoluminescent investigation reveals that the title complex displays interesting emissions in violet and orange regions. The luminescence spectra show stronger orange emission than violet emission. Optical absorption spectra of 1 reveal the presence of a wide optical bandgap of 3.41 eV.     

Synthesis and Crystal Structure of a Lanthanum(III) Complex with Chelidamic Acid

A new lanthanum complex, (H3O)2[La(C7H3NO5)2(H2O)2]2·3(H2O) or (H3O)2[La(HChel)2(H2O)2]2·3(H2O) 1 (H3Chel = 4-hydroxypyridine-2,6-dicarboxylic(chelidamic) acid), has been prepared by the hydrothermal reaction, and its crystal structure was determined based on single-crystal diffraction data. Compound 1 crystallizes in triclinic, space group P with a = 9.6939(19), b = 10.176(2), c = 11.502(2) (A), α = 111.52(3), β = 93.74(3), γ = 103.33(3)°, V = 1013.0(3) (A)3, Dc = 1.912 g/cm3, Z = 1, Mr = 1166.40, μ = 2.188 mm-1, λ(MoKα) = 0.71073 (A) and F(000) = 574. The final R = 0.0342 and wR = 0.0737 for 4080 observed reflections with I > 2σ(I), and R = 0.0429 and wR = 0.0772 for all data. Compound 1 contains two lanthanum ions, four chelidamic acid ligands, four coordinated water molecules, two hydroniums, and three discrete water molecules. The LaIII atom is ten-coordinated by four oxygen and two nitrogen atoms from two tridentate chelating chelidamic acid ligands, two carboxylic oxygen atoms from an adjacent chelidamic acid ligand and two coordinated water molecules, leading to a distorted dodecahedral geometry. A three-dimensional network is formed by H-bonds.     

Combined DFT and wave function theory approach to excited states of lanthanide luminescent materials: A case study of LaF3:Ce3+

Lanthanide luminescent materials play key roles in modern society, but their first-principles treatment remains a great challenge due to complex manifold of electronic excited states and the difficulty in performing excited state structural relaxations that is necessary to model luminescent properties. Herein, we propose a practical approach that combines embedded cluster model (ECM) based multi-configurational wave function theory (WFT) and occupancy constrained density-functional theory plus the Hubbard U correction (OC-DFT + U) to treat lanthanide doped luminescent materials, using LaF₃:Ce³⁺, a typical scintillator with low symmetry, as a case study. We show that the combined approach yields accurate absorption energies with an error on the order of 200 cm⁻¹, but the emission energies are significantly underestimated, the origin of which is further clarified by vibrationally resolved absorption and emission spectra calculation. This work demonstrates the possibility of combining ECM-based wave function theory and periodic DFT into a comprehensive computational scheme for lanthanide luminescent materials and highlights the limitations of the current implementation of OC-DFT + U for excited state structural optimization.     

Effect of ZnO on sintering and microwave dielectric properties of 0.5CaTiO3-0.5 (Li0.5La0.5) TiO3 ceramics

The novel calcium titanate-lithium lanthanum titanate doped with zinc oxide (0.10, 0.30, and 0.50 mol. %) ceramic samples were prepared by solid-state reaction route. The phase formation, microstructure, densification, and microwave dielectric properties were investigated. It was found that the doping with zinc oxide led to a decrease in sintering temperature by 25 ^oC as compared with pure calcium titanate lithium lanthanum titanate due to the liquid phase effect. Also, the calcium titanate lithium lanthanum titanate (10ZCTLLT&30ZCTLLT)) doped with lower zinc oxide (0.10 and 0.30 mol. %) led to higher densification parameter. This was followed by increasing the zinc oxide doping up to (0.50 mol. %) which resulted in a decrease in densification and microwave dielectric properties which may be attributed to increase in porosity and grain growth upon the evaporation of zinc and oxygen vacancy. This led to the increase in dielectric loss (≈10 × 10^?4) value with 50ZCTLLT. Hence, the best result of microwave dielectric characteristics was obtained for 0.5CaTiO₃–0.5(Li_0.5La_0.5)TiO₃ with (0.10 and 0.30 mol. % ZnO) 10ZCTLLT and 30ZCTLLT ceramic samples sintered at 1175 ^oC/2h, with low dielectric constant (ε_r) = 4.4–10.5, very low dielectric loss = 1.07-2.23 × 10^?4 and high quality factor (Q x ?) ≈59-55 × 10⁴ at 8 GHz. Consequently, they can be used not only in wireless satellite communications technology but also can be used in the fifth-generation telecommunication 5G technology construction.     

Electrochemical behaviour of the LiF-(CaF2)-La2O3 system

The electrochemical behaviour of the LiF-La₂O₃ and LiF-CaF₂-La₂O₃ systems was investigated by means of cyclic voltammetry. Several types of working electrodes (spectrographic pure graphite, W, Mo, Ni, Cu) were used. It was found that chemical reactions take place in the system during the dissolution of lanthanum oxide. The reduction of lithium cations occurred at the most positive potential from the species formed in the melt on ‘inert’ cathodes (W, Mo). The reactive cathodes (Cu, Ni) allowed the lanthanum deposition with depolarisation.