WO3纳米片：基于有机-无机杂化前驱物的制备及光催化性能

以商业三氧化钨粉末做为钨源,通过合成WO_x-EDA（EDA=乙二胺）有机-无机杂化纳米带为前驱物,再加盐酸酸化,迅速得到中间产物正交型钨酸单晶纳米片。再在空气气氛下,将中间产物在管式炉中煅烧2h,最终得到单斜型三氧化钨单晶纳米片。一系列对比实验的结果表明,在由杂化纳米带转变成钨酸纳米片时,反应温度、反应时间、酸化浓度等实验参数对产物的结构和形貌有着很大的影响。通过计算,制得的三氧化钨纳米片带隙为2.48eV。对比于商业三氧化钨粉末,三氧化钨纳米片在可见光降解罗丹明B（RhB）中表现出更优越的性能。     

WO_3纳米片:基于无机-有机杂化前驱物的制备及光催化性能

以商业三氧化钨粉末做为钨源,通过合成WOx-EDA(EDA=乙二胺)无机-有机杂化纳米带为前驱物,再加盐酸酸化,迅速得到中间产物正交型钨酸单晶纳米片。再在空气气氛下,将中间产物在管式炉中煅烧2 h,最终得到单斜型三氧化钨单晶纳米片。一系列对比实验的结果表明,在由杂化纳米带转变成钨酸纳米片时,反应温度、反应时间、酸化浓度等实验参数对产物的结构和形貌有着很大的影响。通过计算,制得的三氧化钨纳米片带隙为2.48 eV。对比于商业三氧化钨粉末,三氧化钨纳米片在可见光降解罗丹明B(RhB)中表现出更优越的性能。     

Ba0.15WO3: A bronze with an original pentagonal tunnel structure

The structure of a new barium tungsten bronze, Ba_0.15WO₃, has been established by X-ray diffraction and high-resolution microscopy studies. This bronze is orthorhombic, space group Pbm2 or Pbmm, with a = 8.859(3) Å, b = 10.039(8) Å, and c = 3.808(2)Å. The “WO₃” framework is built up from corner-sharing WO₆ octahedra forming pentagonal tunnels where the barium ions are located. Structural relationships with hexagonal tungsten bronze and tetragonal tungsten bronze structures are discussed.     

Synthesis of polyethylene glycol (PEG) assisted tungsten oxide (WO3) nanoparticles for L-dopa bio-sensing applications

Nanocrystalline tungsten oxides (WO_3−δ) are currently receiving a lot of attention because of their interesting electrical, magnetic, optical and mechanical properties. In this report, we present the synthesis of PEG assisted tungsten oxide (WO₃) nanoparticles by simple household microwave irradiation (2.45 GHz) method. The samples were characterized using powder X-ray diffraction (XRD), thermal analysis (TG/DTA), transmission electron microscopy (TEM), UV-visible diffusion reflectance spectroscopy (UV-VIS-DRS), cyclic voltammetry and electrochemical impedance spectroscopy. Powder XRD results revealed that both the samples prepared with and without surfactant crystallize in the orthorhombic structure corresponding to WO₃·H₂O phase. Subsequent annealing under identical conditions (600 °C/air/6 h) led to significantly different products i.e. monoclinic W₁₇O₄₇ from surfactant free sample and orthorhombic WO₃ from PEG assisted sample. Blue emission was observed through UV-VIS-DRS with blue shift and the band gap energy was estimated as 2.7 and 3.28 eV for PEG assisted as prepared (WO₃·H₂O) and annealed samples (WO₃) respectively. Electrochemical measurements have been performed on all the samples deposited on the surface of glassy carbon (GC) electrode which showed high sensitivity and good selectivity for PEG assisted sample (WO₃·H₂O) for the direct detection of l-dopa.     

Sol–gel synthesis of mesoporous WO3–TiO2 composite thin films for photochromic devices

Mesoporous WO₃–TiO₂ composite films were prepared by a sol gel based two stage dip coating method and subsequent annealing at 450, 500 and 600 °C. An organically modified silicate based templating strategy was adopted in order to obtain a mesoporous structure. The composite films were prepared on ITO coated glass substrates. The porosity, morphology, and microstructures of the resultant products were characterized by scanning electron microscopy, N₂ adsorption–desorption measurements, μ-Raman spectroscopy and X-ray diffraction. Calcination of the films at 450, and 500 °C resulted in mixed hexagonal (h) plus monoclinic phases, and pure monoclinic (m) phase of WO₃, respectively. The degree of crystallization of TiO₂ present in these composite films was not evident. The composite films annealed at 600 °C, however, consist of orthorhombic (o) WO₃ and anatase TiO₂. It was found that the o-WO₃ phase was stabilized by nanocrystalline anatase TiO₂. The thus obtained mesoporous WO₃–TiO₂ composite films were dye sensitized and applied for the construction of photochromic devices. The device constructed using dye sensitized WO₃–TiO₂ composite layer heat treated at 600 °C showed an optical modulation of 51 % in the NIR region, whereas the devices based on the composite layers heat treated at 450, and 500 °C showed only a moderate optical modulation of 24.9, and 38 %, respectively. This remarkable difference in the transmittance response is attributed to nanocrystalline anatase TiO₂ embedded in the orthorhombic WO₃ matrix of the WO₃–TiO₂ composite layer annealed at 600 °C.     

Erratum to: Sol–gel synthesis of mesoporous WO3–TiO2 composite thin films for photochromic devices

Mesoporous WO₃–TiO₂ composite films were prepared by a sol gel based two stage dip coating method and subsequent annealing at 450, 500 and 600 °C. An organically modified silicate based templating strategy was adopted in order to obtain a mesoporous structure. The composite films were prepared on ITO coated glass substrates. The porosity, morphology, and microstructures of the resultant products were characterized by scanning electron microscopy, N₂ adsorption–desorption measurements, μ-Raman spectroscopy and X-ray diffraction. Calcination of the films at 450, and 500 °C resulted in mixed hexagonal (h) plus monoclinic phases, and pure monoclinic (m) phase of WO₃, respectively. The degree of crystallization of TiO₂ present in these composite films was not evident. The composite films annealed at 600 °C, however, consist of orthorhombic (o) WO₃ and anatase TiO₂. It was found that the o-WO₃ phase was stabilized by nanocrystalline anatase TiO₂. The thus obtained mesoporous WO₃–TiO₂ composite films were dye sensitized and applied for the construction of photochromic devices. The device constructed using dye sensitized WO₃–TiO₂ composite layer heat treated at 600 °C showed an optical modulation of 51 % in the NIR region, whereas the devices based on the composite layers heat treated at 450, and 500 °C showed only a moderate optical modulation of 24.9, and 38 %, respectively. This remarkable difference in the transmittance response is attributed to nanocrystalline anatase TiO₂ embedded in the orthorhombic WO₃ matrix of the WO₃–TiO₂ composite layer annealed at 600 °C.     

Visible-light-driven heterostructure Ag/Bi2WO6 nanocomposites synthesized by photodeposition method and used for photodegradation of rhodamine B dye

Visible-light-driven heterostructure Ag/Bi₂WO₆ nanocomposites were prepared by transforming Ag⁺ ions into metallic Ag⁰ nanoparticles loaded on top of Bi₂WO₆ nanoplates under visible light irradiation for 1 h. XRD, XPS, SEM and TEM analyses indicated that spherical metallic Ag nanoparticles were uniformly dispersed on top of orthorhombic Bi₂WO₆ thin nanoplates. Rhodamine B (RhB) was used as a dye model for investigation of photocatalytic performance of Bi₂WO₆ nanoplates with different weight contents of Ag nanoparticles illuminated by visible radiation. In this research, 10% Ag/Bi₂WO₆ nanocomposites have the highest photocatalytic activity in the degradation of RhB at 94.21% within 210 min because of the rapid diffusion of electronic charge through the Schottky barrier between metallic Ag nanoparticles and Bi₂WO₆ thin nanoplates, good electrical conductivity of metallic Ag nanoparticles, inhibited recombination of charge carriers and enhanced photocatalytic activity of Ag/Bi₂WO₆ nanocomposites. Main active species of the photocatalysis and stability of the photocatalyst were also evaluated.

     

Highly efficient mesoporous WO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/KIT-6 catalysts for oxidative desulfurization of dibenzothiophene with hydrogen peroxide

Oxidative desulfurization (ODS) of organic compounds containing sulfur element from a model oil was performed using tungsten oxide catalysts supported on mesoporous silica with cubic Ia3d mesostructure, well-defined mesopores (7.2 nm), high surface area (719 m²/g), and three-dimensional pore network (WO _x /KIT-6). The prepared WO _x /KIT-6 catalysts (5–20 wt% WO _x ) were characterized by X-ray diffraction analysis, N₂ sorption measurements, electron microscopy, H₂-temperature programmed reduction, Raman spectroscopy, and thermogravimetric analysis. Among the mesoporous catalysts, 10 wt% WO _x /KIT-6 exhibited the best catalytic performance. Sulfur-containing organic compounds, such as dibenzothiophene, 4,6-dimethyldibenzothiophene, and benzothiophene, were completely (100 %) removed from the model oil over 10 wt% WO _x /KIT-6 catalyst in 2 h. In addition, the catalyst could be reused several times with only slight decrease in catalytic activity.     

Hydrothermal synthesis of tungsten molybdenum mixed oxides

The phase composition, particle size, and morphology of ultrafine products recovered as a result of hydrothermal treatment of precursor solutions were studied. The precursor solutions were prepared by ion exchange and contained various proportions of tungsten and molybdenum. When tungsten percentages in the precursor solution were 20–95 mol %, the major synthesis product was a mixed oxide (substitutional solid solution (W, Mo)O₃ · 1/3H₂O based on the structure of crystal hydrate WO₃ · 1/3H₂O). When the tungsten percentage was 5 mol %, the product was (W, Mo)O₃ solid solution with the structure of orthorhombic MoO₃. Particle shapes and sizes (ranging from 20 to 8 000 nm) were dictated by the proportion between tungsten and molybdenum compounds in the precursor solution and by the method used to prepare the precursor.     

Products of carbothermal reduction of tungsten oxides in argon flow

The investigation into carbothermal reduction of tungsten oxides has shown that this process involves several steps: WO₃ → WO_2.72 → WO₂ → W. The resulting oxide is rapidly reduced to tungsten metal at 950°C. The carbidization process has a diffusion mechanism. The staged character of carbothermal reduction of tungsten oxides and subsequent carbidization of tungsten are confirmed by scanning electron microscopy, which made it possible to determine the phase composition and size of the resulting particles.     

Growth mechanism and photocatalytic properties of flower-like Bi2WO6 powders synthesized by a microwave hydrothermal method

Pure orthorhombic phase Bi₂WO₆ powders were synthesized by a microwave hydrothermal method in the absence of surfactants and templates, using Bi(NO₃)₃·5H₂O and Na₂WO₄·2H₂O as raw materials. Photocatalytic properties of the samples prepared at different reaction temperatures were also studied with Rhodamine B (RhB) solution as the target catabolite under visible light. The results indicate that flower-like Bi₂WO₆ powders can be obtained by controlling the microwave reaction temperatures in the absence of any additives. The growth of flower-like Bi₂WO₆ powders is a multistage layer assembly process, in which the flower-like Bi₂WO₆ self-assembling with the uniform size about 2 μm is synthesized at 180 °C. At the same time, the photocatalytic reaction rate constant (k) gets up to 0.04167/min and the degradation rate of RhB solution is more than 96 % after being irradiated under visible light for 70 min.     

无模板电化学沉积法制备多孔WO3·2H2O薄膜及其电致变色性能

二水合氧化钨(WO₃·2H₂O)因其独特的层状结构且富含层间结构水,与无水WO₃相比显示出更加优异的电致变色性能。我们采用简单、无模板的阴极电化学沉积方法,成功在氧化铟锡(ITO)导电玻璃基底上制备了WO₃·2H₂O薄膜。通过改变电沉积液中过氧化氢(H₂O₂)的加入量优化沉积液的成分,获得了具有纳米多孔结构的薄膜。由此制备的WO₃·2H₂O薄膜显示出大的光学对比度(633nm处的光学对比度大于90%)、快速的响应速度(着色、褪色时间均小于10s),以及良好的循环稳定性(经10000次循环后,光学对比度仍保持在90%左右)。     

Phase transformations in Li2WO4 at high pressure

The phase diagram of Li₂WO₄ has been determined at high pressure up to 160 kbars and a temperature of 800°C. Three new high-pressure phases have been found in the present study. Crystallographic data are given for Li₂WO₄ III and Li₂WO₄ IV by means of single crystal and powder X-ray analyses. Li₂WO₄ III is orthorhombic with the large unit cell containing 16 molecules and having the edges: a₀ = 10.12(4) Å, b₀ = 10.07(1) Å, c₀ = 11.68(6) Å. Li₂WO₄ IV has an orthorhombic unit cell with the parameters: a₀ = 4.96(7) Å, b₀ = 9.72(8) Å, c₀ = 5.93(8)Å and Z = 4. The total volume decrease is estimated to be 24.8% through the high pressure transformations in Li₂WO₄. No spinel-like structure could be found in the present study.     

Fabricating polypyrrole/tungsten oxide hybrid based electrochromic devices using different ionic liquids

A facile approach of polypyrrole (PPy)/tungsten oxide (WO₃) composites electrosynthesized in ionic liquids for fabrication of electrochromic devices is discussed. The electrochromic properties of PPy/tungsten oxide nanocomposite films (PPy/WO₃) prepared in the presence of four different ionic liquids, 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMIMBF₄), 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIMPF₆), 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl) imide (BMIMTFSI), and 1‐butyl‐1‐methylpyrrolidinium bis(trifluoromethylsulfonyl) imide (BMPTFSI) were investigated in detail. Cyclic voltammetry results revealed that PPy/WO₃ nanocomposite films have much more electrochemical activity than those of WO₃ and PPy film. The electrochromic contrast, coloration efficiency, and switching speed of the composite films were determined for electrochromic characteristics. The maximum contrast and the maximum coloration efficiency values were measured as 33.25% and 227.89 cm²/C for the PPy/WO₃/BMIMTFSI composite film. Copyright © 2015 John Wiley & Sons, Ltd.     

Electrochemical Detection of Nitrite Using an Asymmetrically Substituted Cobalt Phthalocyanine Conjugated to Metal Tungstate Nanoparticles

This paper explores the synthesis and characterisation of an asymmetrical Co phthalocyanine (CoPc), and its covalent linking to two tungsten nanoparticles: bismuth tungsten oxide (Bi₂WO₆) and nickel tungsten oxide (NiWO₄). The nanoparticles were also mixed with the CoPc. The CoPc, nanoparticles and their respective conjugates were used as electrocatalysts in the electrochemical detection of nitrite. The electrocatalysts studied in this work had sensitivities ranging from 3–133 μA/mM while the limits of detection (LoDs) ranged between 0.063 μM and 1.7 μM. Bi₂WO₆ and its conjugate exhibited better LoD than corresponding NiWO₄ and conjugate.     

Thick porous tungsten trioxide films by anodization of tungsten in fluoride containing phosphoric acid electrolyte

In the present work, we report on the formation of mesoporous thick tungsten trioxide films grown on tungsten foil by anodization in fluoride containing concentrated phosphoric acid (85%) electrolyte. Under optimized experimental conditions, mesoporous WO₃ films with a thickness up to approximately 2 μm are formed. SEM shows the films to consist of a connected network with a typical pore and feature diameter of ca 50 nm. These films as formed are amorphous and can be annealed to orthorhombic WO₃ structure. These thick porous films can show significant enhanced electrochromic and improved photocatalytic properties.     

L'oxyde double Fe2WO6. I. Structure cristalline et filiation structurale

The authors have found a new structural type, related to α-PbO₂, called tri-α-PbO₂. The oxide Fe₂WO₆ is the prototype. It crystallizes in the orthorhombic system with the following cell parameters: a = 4.576 Å, b = 16.766 Å, and c = 4.967Å. The space group is Pbcn. The structure has been determined by X-ray single-crystal methods and refined by least-squares procedures (R = 0.065).The structure consists of zig-zag chains parallel to the c-axis. Each such chain is built up by MO₆ (M = Fe or W) octahedra-sharing edges. The chains are linked together by corner sharing. There are two types of chains: one containing only iron atoms, the other being an ordered 1-1 arrangement of iron and tungsten atoms.     

Fabrication of minimal capital-intensive scratch-resistant and hydrophobic tungsten oxide film on stainless steel through spray pyrolysis

In this contribution, a pure and robust tungsten oxide (WO₃) film was accomplished on stainless steel (SS) substrate at 400°C through a minimal capital intensive, simplistic spray pyrolysis method by utilizing a precursor comprising tungsten hexachloride and 2-methoxyethanol. Thermal analysis revealed the precursor's thermal decomposition and crystallization at ~230°C and 255°C, respectively. The fabricated polycrystalline (monoclinic crystal structured) film was uniform and dense in nature, exhibiting surface porosity and average surface roughness of 4.7 % and 15.9 nm, respectively. The average grain size and thickness of film were 360 ± 70 nm and ~3.6 μm, respectively. W, O elemental presence with a close atomic ratio of 1:3 on the film's surface was acquired along with 91 % lattice oxygen. Regardless of applied normal load in the range of 5 to 15 N, an increment of ~22 % in scratch hardness was gained in WO₃-coated SS compared to uncoated one. Hydrophilic natured WO₃ film (water contact angle, WCA, of ~31°) was efficaciously transformed into hydrophobic (WCA, 136°) by chemical modification with octadecyltrichlorosilane to create a self-assembled monolayer on the surface of the film. The hydrophobicity of octadecyltrichlorosilane (OTS)-treated film was found to be preserved even after 100 days.     

不同载体对负载型氧化钨催化剂在己二酸合成反应中的结构及性能影响

以SBA-15、六角介孔二氧化硅（HMS）和SnO₂为载体,通过浸渍法合成了含钨负载型催化剂,并考察了三种催化剂在环氧环己烷选择氧化制备己二酸反应中的催化性能. 通过X射线衍射（XRD）,透射电镜/场发射透射电镜（TEM/FETEM）,紫外-可见漫反射光谱（UV-Vis DRS）,拉曼（Raman）光谱,X射线光电子能谱（XPS）以及傅里叶变换红外（FTIR）光谱等手段对各种催化剂的结构进行表征. 结果表明,载体与催化剂的性能有密切的关系. 以SnO₂为载体的WO₃/SnO₂催化剂活性最高,其次是WO₃/HMS催化剂,WO₃/SBA-15 催化剂的活性最差.XRD 分析显示WO₃/SnO₂催化剂中氧化钨物种的晶化程度最低,TEM 和XPS 结果表明氧化钨物种在WO₃/SnO₂催化剂表面高度分散并且粒径尺寸很小（约2 nm）,UV-Vis DRS结果表明在WO₃/SnO₂催化剂中存在孤立[WO₄]四面体和低聚态的钨物种,这些物种的存在可能是WO₃/SnO₂催化剂具有高活性的主要原因. 此外,WO₃/SnO₂催化剂可以重复使用多次,6 次反应后己二酸（AA）得率仍然保持在80%以上,说明氧化钨物种与SnO₂载体间存在强烈的相互作用,从而提高了催化剂的稳定性.     

Untersuchungen an Metallkatalysatoren. XVII. Phasenaufbau,Dispersität und Dehydrieraktivität Molybdän- und wolframmodifizierter Palladiumkatalysatoren

Investigations on Metal Catalysts. XVII. Phase Structure, Dispersity, and Dehydrogenation Activity of Palladium Catalysts Modifided by Molybdenum and Tungsten Molybdenum and tungsten containing palladium catalysts were prepared by reduction of mixtures from Pd(NO₃)₂ with MoO₃ and WO₃, respectively, with hydrogen at 600°C and 800°C. The powders were characterized by means of several methods: Determination of the oxidation state for molybdenum and tungsten, X-ray measurements, N₂ adsorption, CO chemisorption, H₂ sorption, dehydrogenation of cyclohexane. The properties of the samples (heated at 600°C) are determined to a high degree by the co-existence of the palladium phase as well as the molybdenum and tungsten oxide, respectively, in the mean oxidation state +4. The after-reduction at 800°C leads to a great portion of metallic molybdenum and tungsten in the concerned catalysts. There are references that the treatment at 800°C in the presence of hydrogen causes for the Pd? Mo catalysts an increase of the palladium content in the surface of the crystallites.