The Reaction Mechanism and Kinetics of the Zn2.5VMoO8 Phase Synthesis in the Solid State

Studies on the reaction kinetics and mechanism of the synthesis of the Zn_2.5VMoO₈ compound in the solid state have been carried out in situ in a high-temperature X-ray diffraction attachment. The apparent activation energy, 212±26 kJ mol^-1 was calculated by using the diffusion controlled Ginstling-Brounstein model. There was also determined a temperature dependence of unit cell parameters for Zn₃V₂O₈ and Zn_2.5VMoO₈. This revised version was published online in July 2006 with corrections to the Cover Date.     

Study on Phase Relations in Zn3V2O8–ZnMoO4 System

The phase equlibria established in the Zn₃V₂O₈–ZnMoO₄ system over the whole component concentration range up to 1000°C have been investigated. A phase diagram has been constructed using the results of DTA and XRD methods. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis and Growth of Flower-Like Zn-Doped CdSe Microstructures

Hexagonal phase flower-like Zn-doped CdSe (Cd_1-xZn_xSe, x = 0.3) semiconductor microstructures from the solid air-stable precursor have been achieved in the mixed solution of ethylenediamine (en) and ethylene glycol (EG) at 180°C for 12 hours. Characterized by powder x-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy dispersive spectrum (EDS), and UV-vis absorption spectroscopy, it can be seen that the as-synthesized Cd_0.7Zn_0.3Se is hexagonal phase, and each flower-like Cd_0.7Zn_0.3Se microstructure is made up of many Cd_0.7Zn_0.3Se nanoflakes. From the UV-vis absorption spectrum of the product, it was observed that the optical band gap energies of flower-like Cd_0.7Zn_0.3Se microstructures shift toward shorter wavelengths compared with CdSe.     

5-二乙胺基-2-(吡啶-2’-亚氨甲基)苯酚的合成及其对Zn2+的识别

本文利用2-氨基吡啶与4-二乙胺基水杨醛反应合成了5-二乙胺基-2-(吡啶-2’-亚氨甲基)苯酚(探针L),对其结构进行了表征。在DMSO/Tris(6:4, v/v, pH =7.4)溶液中,探针L高选择性荧光“关-开”识别Zn₂₊,在365 nm紫外灯照射下,由无荧光变成蓝色荧光。实验表明,探针L与Zn₂₊的结合比为1:1,结合常数为2.6×10₃ L. mol_-1,检测限为 9.39×10_-7mol/L,pH适用范围为7-11,并可检测水样中的Zn₂₊。     

Thermal and photochemical effects on the structure,morphology, thermal and optical properties of PVA/Ni0.04Zn0.96O and PVA/Fe0.03Zn0.97O nanocomposite films

Ni_0.04Zn_0.96O and Fe_0.03Zn_0.97O with average diameter of 23 and 19 nm, respectively, have been synthesized by a modified sol–gel method to be used in the preparation of (100 − x)/x poly(vinyl alcohol)/oxide nanocomposite films, with x = 0, 1, 3 and 5 (in wt.%). A 125 W-Hg vapor lamp with emission above 254 nmwas used to irradiate PVA/Ni_0.04Zn_0.96O and PVA/Fe_0.03Zn_0.97O films. The effect on their structural, thermal, morphological and optical properties was studied by TG, DSC, DRX, AFM, UV–vis and PL spectrophotometry. The Ni_0.04Zn_0.96O addition on PVA films decreases the thermal stability of the polymer in inert and in oxidative atmosphere. In contrast, the Fe_0.03Zn_0.97O presence in the PVA films seems to increase the thermal stability of the polymer. The characteristic peak of the crystalline phase of PVA and wurtzite phase of the zinc oxide were identified through X-ray diffraction in both films. The crystallinity of the PVA film increases with UV irradiation and with the presence of Ni_0.04Zn_0.96O and Fe_0.03Zn_0.97O. The roughness of the PVA film was not modified by the addition of the doped oxides; however, it increases after UV irradiation, more significantly in the films containing the oxides. The PVA film exhibits absorption around 280 nm characteristic of π–π^∗ transitions related to carbonyl groups from residuals acetate, while the 95/05 PVA/Ni_0.04Zn_0.96O and 95/05 PVA/Fe_0.03Zn_0.97O nanocomposite films show absorption at the visible region which is characteristics of the band gap reduction of the doped oxides. The photoluminescence of PVA was modified by the presence of the oxides in the film. These nanocomposite films are interesting due to their thermal, mechanical (flexible) properties and low cost of production. In addition they are also able to exhibit peculiar optical properties showing potential to be used in photonic devices, gas sensors and organic solar cell applications.     

A fluorescent 3-D metal-organic framework with unusual tetranuclear zinc secondary building units

A 3-D metal-organic framework (MOF) {Zn₄(μ₃-OH)₂(bdc)₃(pad)₂}·2H₂O (1, H₂bdc = 1,4-benzenedicarboxylic acid, pad = 1,10-phenanthroline-5,6-dione) with unusual Zn₄(μ₃-OH)₂(COO)₆(N₂)₂ secondary building units (SBUs) has been hydrothermally synthesized and characterized by single crystal X-ray diffraction, powder X-ray diffraction, thermogravimetric analysis, elemental analysis, and infrared spectroscopy. The tetranuclear Zn₄ SBU was formed through two dinuclear Zn₂ clusters by sharing two μ₃-OH bridges. Considering this Zn₄ SBU as a six-connected node, the overall framework of 1 has a pcu topology. This tetranuclear Zn₄ SBU can be used as a node in construction of MOFs.     

Ultrasonic-assisted synthesis of PMMA/Ni0.5Zn0.5Fe2O4 nanocomposite in mixed surfactant system

PMMA/Ni_0.5Zn_0.5Fe₂O₄ nanocomposite with superparamagnetic behavior was synthesized by in situ emulsion polymerization of methylmethacrylate (MMA) monomer in the presence of Ni_0.5Zn_0.5Fe₂O₄ colloidal suspension assisted by ultrasonic irradiation. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). XRD and FT-IR spectra confirmed the formation of PMMA/Ni_0.5Zn_0.5Fe₂O₄ nanocomposite. TEM images showed that Ni_0.5Zn_0.5Fe₂O₄ nanoparticles with the particle sizes of about 12 nm were well dispersed in the polymer matrix. The nanocomposite at room temperature exhibited superparamagnetic behavior under applied magnetic field. The formation mechanism of PMMA/Ni_0.5Zn_0.5Fe₂O₄ nanocomposite was proposed as well.     

Zn_2GeO_4纳米棒的制备及发光性质

采用水热合成法制备了纯菱形相的Zn_2GeO_4纳米棒,研究了水热制备前驱体溶液的pH值对材料尺寸及形貌的影响以及Zn_2GeO_4纳米棒的光学性质。扫描电子显微镜(SEM)测试结果表明,随着前驱体溶液pH值的变化样品逐渐由微米级块状结构生长成为纳米颗粒,并且进一步形成纳米棒结构。纳米棒的尺寸由长200 nm变化到500 nm。室温光致发光(PL)光谱中观察到位于450和530 nm两个不同的发光峰,其分别源于Zn_2GeO_4的不同缺陷能级。     

Photocatalytic production of hydrogen in systems based on Cd<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>S/Ni<Superscript>0</Superscript> nanostructures

A relation was established between the composition of Cd _x Zn_1–x S nanoparticles and their ability to accumulate excess negative charge during irradiation. The rate of expenditure of the accumulated charge depends on the composition of the nanoparticles and is determined by their electric capacitance. A correlation was found between the photocatalytic activity of the Cd _x Zn_1–x S nanoparticles in the release of hydrogen from solutions of Na₂SO₃, their composition, and their capacity for photoinduced accumulation of excess charge. It was shown that Ni⁰ nanoparticles photodeposited on the surface of Cd _x Zn_1–x S are effective cocatalysts for the release of hydrogen. It was found that Zn^II additions in photocatalytic systems based on Cd _x Zn_1–x S/Ni⁰ nanostructures have a promoting action on the release of hydrogen from water–ethanol mixtures. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 1, pp. 8–16, January-February, 2009.     

Zn2GeO4纳米棒的制备及发光性质

采用水热合成法制备了纯菱形相的Zn₂GeO₄纳米棒,研究了水热制备前驱体溶液的pH值对材料尺寸及形貌的影响以及Zn₂GeO₄纳米棒的光学性质。扫描电子显微镜（SEM）测试结果表明,随着前驱体溶液pH值的变化样品逐渐由微米级块状结构生长成为纳米颗粒,并且进一步形成纳米棒结构。纳米棒的尺寸由长200 nm变化到500 nm。室温光致发光（PL）光谱中观察到位于450和530 nm两个不同的发光峰,其分别源于Zn₂GeO₄的不同缺陷能级。     

Structure of a di-zinc complex of a bis-calix[4]arene conjugate and its sensing of cysteine among the amino acids

Abstract

A triethylene glycol di-imine locked triazole linked bis-calix[4]arene conjugate (L) and its Zn²⁺ complex [Zn₂L], were synthesised, characterised and the three-dimentional (3-D) structure of the complex was established by single crystal XRD. In this complex, the Zn²⁺ centre exhibits distorted tetrahedral geometry with N₂O₂ binding core. The complex showed selectivity towards cysteine (Cys) with greater sensitivity followed by histidine (His) among the naturally occurring amino acids studied based on fluorescence and absorption spectroscopy. The fluorescence quenching of the complex is much greater with Cys as compared to that of His. The detection limit of Cys is 650 ppb. Release of Zn²⁺ from its complex [Zn₂L] followed by its capture by –SH containing molecules was shown based on absorption and emission spectroscopy. This was also shown in one case by ¹H NMR spectroscopy.     

A new structure type of phosphate: Crystal structure of Na2Zn5(PO4)4

A new compound, Na₂Zn₅(PO₄)₄, was identified in the system ZnONa₂OP₂O₅ and high-quality crystal was obtained by the melt method. The crystal structure of this compound was solved by direct method from single crystal X-ray diffraction data. The structure was then refined anisotropically using a full-matrix least square refinement on F² and the refinement converged to R₁=0.0233 and wR₂=0.0544. This compound crystallizes in the orthorhombic system with space group Pbcn, lattice parameters a=10.381(2) Å, b=8.507(1) Å, c=16.568(3) Å and Z=4. The structure is made up of 3D [Zn₅P₄O₁₆]_n²ⁿ⁻ covalent framework consisting of [Zn₄P₄O₁₆]_n⁴ⁿ⁻ layers. The powder diffraction pattern of Na₉Zn₂₁(PO₄)₁₇ is explained by simulating a theoretical pattern with NaZnPO₄ and Na₂Zn₅(PO₄)₄ in the molar ratio of 1:4 and then by Rietveld refinement of experimental pattern. Na₂Zn₅(PO₄)₄ melts congruently at 855 °C and its conductivity is 5.63×10⁻⁹ S/cm.     

Composition-induced phase transition in Ca14Zn6−xGa10+xO35+x/2 (x=0.0 and 0.5)

Novel complex oxides Ca₁₄Zn₆Ga₁₀O₃₅ and Ca₁₄Zn_5.5Ga_10.5O_35.25 were prepared in air at 1200 °C, 72 h. Refinements of their crystal structures using X-ray powder diffraction data showed that Ca₁₄Zn₆Ga₁₀O₃₅ is ordered (S.G. F23, =0.0458, R_p=0.0485, R_wp=0.0659, χ²=1.88) and Ca₁₄Zn_5.5Ga_10.5O_35.25 disordered (S.G. F432, =0.0346, R_p=0.0601, R_wp=0.0794, χ²=2.82) variants of the crystal structure of Ca₁₄Zn₆Al₁₀O₃₅. In the crystal structure of Ca₁₄Zn₆Ga₁₀O₃₅, there are large empty voids, which could be partially occupied by additional oxygen atoms upon substitution of Zn²⁺ by Ga³⁺ as in Ca₁₄Zn_5.5Ga_10.5O_35.25. These oxygen atoms are introduced into the crystal structure of Ca₁₄Zn_5.5Ga_10.5O_35.25 only as a part of four tetrahedra (Zn, Ga)O₄ groups sharing common vertex. This creates a situation where even a minor change in the chemical composition leads to considerable anion and cation disordering resulting in a change of space group from F23 (no. 196) to F432 (no. 209).     

The system Ce–Zn–B at 800 °C

The isothermal section for the system Ce–Zn–B has been established at 800 °C using electron microprobe analysis and X-ray powder diffraction. No ternary compounds exist and mutual solid solubilities of binary phases are negligible. In the concentration range of 10.0–10.5 at% Ce two structural modifications have been confirmed: high temperature βCe₂Zn₁₇ above ∼750 °C with the Th₂Zn₁₇ type (R3?m, a=0.90916(4) nm, c=1.3286(1) nm) and low temperature αCeZn₇ (Ce_1−xZn_5+2x; x∼0.33) up to 750 °C for which we attributed the TbCu₇ type (P6/mmm, a=0.52424(2), c=0.44274(1) nm). The crystal structure of CeZn₇ was derived from the Rietveld refinement of X-ray powder intensities. Precise data on atom site distribution and positional parameters have been furthermore provided from X-ray single crystal refinements for two compounds, for which crystal structures hitherto have only been derived from X-ray diffraction photographs: Ce₃Zn₁₁ (Immm, a=0.45242(2) nm, b=0.88942(3) nm, c=1.34754(4) nm) and Ce₃Zn₂₂ (I4₁/amd; a=0.89363(2) nm, c=2.1804(5) nm).     

Synthesis and Thermal Stability of Zn4V2O9

A study of synthesis and thermal decomposition of the Zn₄V₂O₉ have been conducted by XRD method using a high-temperature X-ray attachment. A melting temperature and the way of melting that compound have been established. This revised version was published online in July 2006 with corrections to the Cover Date.     

微波水热合成Zn2GeO4纳米带及其光催化活性

采用微波水热法快速合成Zn₂GeO₄纳米带, 研究反应温度、模板剂、原料用量等因素对晶体生长的影响, 并优化其合成条件. 用场发射扫描电镜(FE-SEM)、X射线衍射(XRD)光谱和紫外-可见漫反射吸收光谱(UV-Vis RDS)等手段分析产物的形貌、结构和组成, 考察合成的Zn₂GeO₄在甲基橙光催化降解反应中的性能. 研究结果表明: 微波水热条件下, 以摩尔比为2:1的乙酸锌和氧化锗为原料, 在160℃反应20 min可合成分散均匀的Zn₂GeO₄纳米带, 宽约100 nm, 长为几十微米. 与常规水热法相比,微波水热法合成的Zn₂GeO₄纳米带的本征缺陷减少, 光致发光(PL) 光谱降低,比表面积增大50.7%,光催化活性提高54.7%.     

Preparation of Cu-doped Cd0.1Zn0.9S solid solution by hydrothermal method and its enhanced activity for hydrogen production under visible light irradiation

A series of Cu-doped Cd_0.1Zn_0.9S solid solution with various amounts of Cu dopant was successfully prepared by hydrothermal method. The properties and the photocatalytic activity of the prepared samples for hydrogen production under visible light irradiation were compared to those prepared by co-precipitation method. The Cu-doped Cd_0.1Zn_0.9S samples prepared by hydrothermal method showed both improved crystallinity and photoabsorption ability as compared to the undoped sample. On the other hand, even though Cu-doped Cd_0.1Zn_0.9S prepared by co-precipitation method also showed improved photoabsorption ability in the visible light region, the samples showed poor crystallinity compared to the undoped one. With the same amount of Cu dopant, all samples prepared by hydrothermal method were found to exhibit higher photocatalytic activity for hydrogen production than the samples prepared by co-precipitation method. It was revealed that the amount of Cu dopant, crystallinity and narrow band gap energy are important factors to obtain highly active and stable photocatalysts.     

Fabrication and Optical Properties of Aligned Zn1-xMgxO Nanowire Arrays

Aligned Zn_1-xMg_xO nanowire arrays were successfully prepared on Si(111) substrates via the chemical vapor deposition (CVD) method with a mixture of ZnO, Mg, and activated carbon powders as reactants. The microstructures and optical properties of the synthesized Zn_1-xMg_xO nanowire arrays were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis X-ray (EDAX), and photoluminescence (PL) spectrum analytic apparatus, respectively. While Mg content was achieved or less approximately 0.29 (x, atomic ratio) in ZnO lattice, the crystal lattice of the synthesized samples exhibited wurtzite structure. The Mg atoms were distributed into the ZnO crystal as the interstitial and displaced atoms, and there was no phase separation in preparing Zn_1-xMg_xO nanowire arrays. However, as the Mg content was up to 0.53 (x) in the fabricated Zn_1-xMg_xO samples, a clear phase separation phenomena appeared in the Zn_1-xMg_xO crystal. Compared with the PL spectrum of the pure ZnO nanowire arrays, the analytic results showed that a blue-shift of the near-band edge emission with increasing Mg content was observed in the Zn_1-xMg_xO arrays. And the relative intensities of green peak at ca 535 nm and UV emission peak at ca 376 nm were all restrained.     

Optical Properties of Mg x Zn1−x O Polycrystalline Thin Films Prepared by Sol-Gel Deposition Method

The Mg _x Zn_1–x O alloy thin films were synthesized on Si and quartz substrates by the sol-gel deposition method. The transmittance and cathodoluminescence spectra of the Mg_0.05Zn_0.95O and Mg_0.15Zn_0.85O nanoparticle films were obtained at room temperature. It was found that the bandgap of Mg_0.05Zn_0.95O and Mg_0.15Zn_0.85O films is as large as 3.72 eV and 3.79 eV, respectively. The ultraviolet emission peaks are located at 376 nm and 370 nm, respectively, for the samples annealed at 600°C. When the annealing temperature is elevated to 1000°C, the band-gap decreases to 3.42 eV and an emission line related to the deep-level defect appears at 500 nm. The mechanism behind these phenomena is discussed.