Synthesis of W18O49 nanorod via ammonium tungsten oxide and its interesting optical properties

W(18)O(49) nanorods were synthesized by pyrolyzing (NH(4))(x)WO(3+x/2) nanorods precursors, which were prepared by a hydrothermal reaction using sulfate as a structure-directing agent, in a reductive atmosphere of H(2)(5 vol %)/N(2) at 500 °C for 1 h. W(18)O(49) nanorods showed high transmittance in the visible region as well as excellent shielding properties of NIR lights. A simulated experiment revealed that excellent heat insulating performance can be realized by applying a 70% visible light transparent W(18)O(49) coating on a quartz glass. Meanwhile, the W(18)O(49) nanorods also showed strong absorption of NIR light and instantaneous conversion of photoenergy to heat. In a word, W(18)O(49) nanorods hold interesting optical properties and are a promising material in a wide range of applications.     

Morphology-controlled synthesis of W18O49 nanostructures and their near-infrared absorption properties

The morphology-controlled synthesis and near-infrared (NIR) absorption properties of W(18)O(49) were systematically investigated for the application of innovative energy-saving windows. Various morphologies of W(18)O(49), such as nanorods, nanofibers, nanograins, nanoassembles, nanoplates, and nanoparticles, with various sizes were successfully synthesized by solvothermal reactions using organic alcohols as reaction media and WCl(6), W(EtO)(6), and WO(3) solids as the tungsten source. W(18)O(49) nanorods of less than 50 nm in length showed the best optical performance as an effective solar filter, which realized high transmittance in the visible region as well as excellent shielding properties of NIR light. Meanwhile, the W(18)O(49) nanorods also exhibited strong absorption of NIR light and instantaneous conversion of the absorbed photoenergy to the local heat.     

Atmospheric pressure chemical vapor deposition: an alternative route to large-scale MoS2 and WS2 inorganic fullerene-like nanostructures and nanoflowers

Large-scale MoS2 and WS2 inorganic fullerene-like (IF) nanostructures (onionlike nanoparticles, nanotubes) and elegant three-dimensional nanoflowers (NF) have been selectively prepared through an atmospheric pressure chemical vapor deposition (APCVD) process with the reaction of chlorides and sulfur. The morphologies were controlled by adjusting the deposition position, the deposition temperature, and the flux of the carrier gas. All of the nanostructures have been characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). A reaction mechanism is proposed based on the experimental results. The surface area of MoS2 IF nanoparticles and the field-emission effect of as-prepared WS2 nanoflowers is reported.     

Synthesis of WO3 nanorods by reacting WO(OMe)4 under autogenic pressure at elevated temperature followed by annealing

This article reports on the fabrication of WO(3) nanorods using an efficient straightforward synthetic technique, without a catalyst, and using a single precursor. The thermal dissociation of WO(OMe)(4) at 700 degrees C in a closed Swagelok cell under an air/inert atmosphere yielded W(18)O(49) nanorods. Annealing of W(18)O(49) at 500 degrees C under an air atmosphere led to the formation of pure WO(3) nanorods. The obtained products are characterized by morphological (scanning electron microscopy and transmission electron microscopy), structural (X-ray diffraction analysis, high-resolution scanning electron microscopy, and Raman spectroscopy), and compositional [energy-dispersive X-ray and elemental (C, H, N, S) analysis] measurements. The mechanism of the formation of nonstoichiometric W(18)O(49) nanorods is supported by the measured analytical data and several control experiments.     

Shock-wave resistance of WS2 nanotubes

The shock-wave resistance of WS(2) nanotubes has been studied and compared to that of carbon nanotubes. Detailed structural features of post-shock samples were investigated using HRTEM, XRD, and Raman spectroscopy. WS(2) nanotubes are capable of withstanding shear stress caused by shock waves of up to 21 GPa, although some nanotube tips and nanoparticles containing multiple structural defects in the bending regions are destroyed. Small WS(2) species, consisting of only a few layers, are extruded from the nanotubes. Well-crystallized tube bodies were found to exhibit significant stability under shock, indicating high tensile strength. XRD and Raman analyses have confirmed this structural stability. Under similar shock conditions, WS(2) tubes are more stable than carbon nanotubes, the latter being transformed into a diamond phase. WS(2) nanotubes containing small concentrations of defects possess significantly higher mechanical strength, and, as a consequence, hollow WS(2) nanoparticles are expected to act as excellent lubricants under much higher loading than was previously thought.     

Comprehensive interpretation of a substitution effect on an order-disorder phase transition in A(1-x)MxW2O(8-y) (A = Zr, Hf; M = trivalent cations) and other ZrW2O8-based solid solutions

Hf(1-x)Lu(x)W(2)O(8-y) solid solutions up to x = 0.04, based on a negative thermal expansion material HfW(2)O(8), were synthesized by a solid state reaction method. X-ray diffraction experiments of these solid solutions from 90 to 560 K indicated thermal contraction with increasing temperature. Temperatures of order-disorder phase transition (T(trs)) associated with the orientation of WO(4) tetrahedra were determined from disappearance of a characteristic diffraction peak (310). The T(trs) of the solid solutions drastically decreased with increasing Lu content. Saturated order parameters (eta(s)) associated with the orientational order of the WO(4) pairs were estimated from the characteristic diffraction peak at sufficient low temperature. These behaviors of Hf(1-x)Lu(x)W(2)O(8-y) are consistent with those of Zr(1-x)M(x)W(2)O(8-y) (M = Sc, Y, In, Lu). The drastic suppression of T(trs) in Hf(1-x)Lu(x)W(2)O(8-y) can be interpreted in the framework of a model proposed for Zr(1-x)M(x)W(2)O(8-y), which states the existence of a local nanoregion including the WO(4) pairs having the frozen-in orientational disorder. To understand the substitution effect on the order-disorder phase transition comprehensively, classification based on the saturated order parameter eta(s) of the phase transition of AW(2)O(8) (A = Hf, Zr)-based solid solutions was carried out and discussed.     

一维硫化镉/二维二硫化钨纳米异质结用于超高活性光催化制氢

基于半导体的太阳能光催化分解水制氢技术是一种环境友好、潜力巨大的绿色氢能制造方案.常用的块体半导体材料一般具有较弱的可见光吸收、快速的光生载流子复合以及较低的光催化制氢效率等缺点.因此,设计开发具有宽光谱光吸收、稳定性好、催化活性高的太阳能光催化材料是促进光催化制氢发展的关键,也是该研究方向的挑战之一.硫化镉纳米材料是...     

钢铁表面W—S簇合物彩色钝化膜的组成和结构

通过（ＮＨ４）２ＷＳ４溶液浸渍，在钢铁表面获得了具有良好装饰效果和耐蚀性能的彩色Ｗ－Ｓ簇合物膜．ＦＴ－ＩＲ、Ｆ－ＩＲ、ＦＴ－Ｒａｍａｎ、ＸＰＳ和ＡＥＳ分析结果表明，簇合物膜中存在Ｗ—Ｓ—Ｆｅ、端基Ｗ—Ｓ和端基Ｗ—Ｏ键，膜层由Ｗ、Ｓ、Ｆｅ、Ｏ元素组成，膜外层各元素价态分别为＋６、＋６（＋４）、＋３、－２，膜内层其价态则分别为＋６（＋４）、－２、＋２、－２．膜为多分子层结构，从ＡＥＳ深度分布曲线的组成恒定区求得了元素的相对原子分数和膜层厚度．反应时间越长，膜越厚．在２５０℃空气中加热２ｈ后膜层所含元素种类和价态不变，但各元素的分布和膜的结构发生了变化     

Raman spectroscopic study of tungsten(VI) oxosulfato complexes in WO3-K2S2O7-K2SO4 molten mixtures: stoichiometry, vibrational properties, and molecular structure

The dissolution reaction of WO3 in pure molten K2S2O7 and in molten K2S2O7-K2SO4 mixtures is studied under static equilibrium conditions in the XWO3(0) = 0-0.33 mol fraction range at temperatures up to 860 °C. High temperature Raman spectroscopy shows that the dissolution leads to formation of W(VI) oxosulfato complexes, and the spectral features are adequate for inferring the structural and vibrational properties of the complexes formed. The band characteristics observed in the W=O stretching region (band wavenumbers, intensities, and polarization characteristics) are consistent with a dioxo W(=O)2 configuration as a core unit within the oxosulfato complexes formed. A quantitative exploitation of the relative Raman intensities in the binary WO3-K2S2O7 system allows the determination of the stoichiometric coefficient, n, of the complex formation reaction WO3 + nS2O7(2-) --> C(2n-). It is found that n = 1; therefore, the reaction WO3 + S2O7(2-) > WO2(SO4)2(2-) with six-fold W coordination is proposed as fully consistent with the observed Raman features. The effects of the incremental dissolution and presence of K2SO4 in WO3-K2S2O7 melts point to a WO3 · K2S2O7 · K2SO4 stoichiometry and a corresponding complex formation reaction in the ternary molten WO3-K2S2O7-K2SO4 system according to WO3 + S2O7(2-) + SO4(2-) --> WO2(SO4)3(4-). The coordination sphere of W in WO2(SO4)2(2-) (binary system) is completed with two oxide ligands and two chelating sulfate groups. A dimeric [{WO2(SO4)2}2(μ-SO4)2](8-) configuration is proposed for the W oxosulfato complex in the ternary system, generated from inversion symmetry of aWO2(SO4)3(4-) moiety resulting in two bridging sulfates. The most characteristic Raman bands for the W(VI) oxosulfato complexes pertain to W(=O)2 stretching modes (i) at 972 (polarized) and 937 (depolarized) cm(-1) for the ν(s) and ν(as) W(=O)2 modes of WO2(SO4)2(2-), and (ii) at 933 (polarized) and 909 (depolarized) cm(-1) for the respective modes of [{WO2(SO4)2}2(μ-SO4)2](8-).     

Large cluster formation through multiple substitution with lanthanide cations (La, Ce, Nd, Sm, Eu, and Gd) of the polyoxoanion

Several new large polyoxotungstates have been synthesized by reaction of lanthanide cations with the well-known "As(4)W(40)" anion, [(B-alpha-AsO(3)W(9)O(30))(4)(WO(2))(4)](28-) (1). The heteropolyanions [(H(2)O)(11)Ln(III)(Ln(III)(2)OH)(B-alpha-AsO(3)W(9)O(30))(4)(WO(2))(4)](20)(-) (Ln = Ce, Nd, Sm, Gd) (2-4) (Ln(3)As(4)W(40)) and [M(m)()(H(2)O)(10)(Ln(III)(2)OH)(2)(B-alpha-AsO(3)W(9)O(30))(4)(WO(2))(4)]((18-m)(-)) (Ln = La, Ce, Gd and M = Ba, K, none) (5-7) (Ln(4)As(4)W(40)) have been isolated as alkali metal and ammonium salts, respectively, and characterized by single-crystal X-ray analysis, elemental analysis, and IR and (183)W-NMR spectroscopy. The X-ray analyses revealed interanionic W-O-Ln bonds between adjacent Ln(x)()As(4)W(40) units forming a "dimer" for x = 3 and chains for x = 4. Upon dissolving in water these bonds hydrolyze and the monomeric species form. The straightforward syntheses which require the use of concentrated NaCl solutions (1-4 M) and the addition of stoichiometric amounts of Ba(2+) or K(+) reemphasize the importance of the presence of appropriate countercations for the assembly of large polyoxometalate structures.     

An inorganic route for controlled synthesis of W18O49 nanorods and nanofibers in solution

In this work, we describe a simple inorganic route for synthesis of monodispersed W(18)O(49) nanorods with dimensional control in the quantum confinement regime. The single-crystalline W(18)O(49) nanorods can be prepared into stable colloidal solutions, or assembled into fibrous and/or paper forms by tuning process parameters. The important role of Na(2)SO(4) salt in the synthesis has been demonstrated. This inorganic route should be feasible for large-scale production of low-dimensional nanostructured W(18)O(49).     

Promoting infrared light driven photocatalytic activity of W18O49 nanorods by coupling polypyrrole

Research on Chemical Intermediates - It is essential to promote the infrared light driven photocatalytic activity of W18O49. To do this, W18O49 nanorods coupled with polypyrrole (PPY) have been...     

Synthesis, X-ray and neutron diffraction characterization, and ionic conduction properties of a new oxothiomolybdate Li3[Mo8S8O8(OH)8[HWO5(H2O)]] x 18H2O

The new oxothiomolybdate anion [Mo8S8O8(OH)8[HWO5(H2O)]]3- (denoted HMo8W3-) has been synthesized in aqueous solution by an acido-basic condensation reaction. Four (Mo(V)2S2O2) building blocks are connected through hydroxo bridges around a central [W(VI)O6] octahedron. X-ray and neutron diffraction studies have been performed on single crystals of the lithium salt Li3[Mo8S8O8(OH)8[HWO5(H2O)]] x 18H2O (Li3HMo8W x 18H2O) in an aqueous grown from HMo8W3- solution of LiCl (1 M). The neutron diffraction experiment enabled us to locate both the protons and the lithium ions. In the structure of Li3HMo8W x 18H20, ring-shaped anions interleaved by a cluster of disordered hydrogen-bonded water molecules stack on top of each other along lithium pillars. The lithium columns are formed by alternating edge-sharing octahedra and tetrahedra, with one lithium site in four being totally vacant. Ionic conductivity measurements on pressed pellets have shown that Li3HMo8W x 18H2O is a good ionic conductor at room temperature (sigma = 10(-5) S cm(-1)), but the ionic conductivity on single crystals is smaller by two orders of magnitude and is isotropic; this suggests the main path of conduction involves surface protons rather than lithium ions of the bulk.     

硫化态NiW/Al2O3催化剂加氢脱硫活性相的研究Ⅰ.XPS和HREM表征

 采用孔饱和共浸法制备了一系列具有相同W含量和不同Ni含量的NiW/Al2O3催化剂,并对相应的硫化态催化剂进行了XPS和HREM表征. 结果表明,引入的助剂Ni优先修饰WS2晶粒的边角位置,形成高活性的NiWS相. 催化剂中助剂Ni在噻吩加氢脱硫反应中的显著促进效应(活性提高了约30倍)与形成的NiWS活性相数量有关. 同时,助剂Ni的引入使得催化剂表面WS2晶粒的堆叠程度略有增加,晶片长度略有减小;而且引入助剂后WOx相的硫化度提高了近20%. 但相比之下,活性相织构的变化和硫化度的增大对催化脱硫活性的贡献较小,不是Ni产生助剂效应的主要原因.     

Selective synthesis and characterization of single-crystal silver molybdate/tungstate nanowires by a hydrothermal process

Selective synthesis of uniform single crystalline silver molybdate/tungstate nanorods/nanowires in large scale can be easily realized by a facile hydrothermal recrystallization technique. The synthesis is strongly dependent on the pH conditions, temperature, and reaction time. The phase transformation was examined in details. Pure Ag(2)MoO(4) and Ag(6)Mo(10)O(33) can be easily obtained under neutral condition and pH 2, respectively, whereas other mixed phases of Mo(17)O(47), Ag(2)Mo(2)O(7,) Ag(6)Mo(10)O(33) were observed under different pH conditions. Ag(6)Mo(10)O(33) nanowires with uniform diameter 50-60 nm and length up to several hundred micrometers were synthesized in large scale for the first time at 140 degrees C. The melting point of Ag(6)Mo(10)O(33) nanowires were found to be about 238 degrees C. Similarly, Ag(2)WO(4), and Ag(2)W(2)O(7) nanorods/nanowires can be selectively synthesized by controlling pH value. The results demonstrated that this route could be a potential mild way to selectively synthesize various molybdate nanowires with various phases in large scale.     

Artificial lamellar mesostructures to WS(2) nanotubes

A direct pyrolysis method from artificial lamellar mesostructures to nanotubes was developed for the synthesis of tungsten disulfide (WS(2)) nanotubes. In this process, a tungsten sulfide artificial lamellar mesostructure composite with intercalated cetyltrimethylammonium cations (WS-L) was prepared on the basis of the recently developed template self-assembly of anionic tungstates (WS(4)(2-)) and cationic surfactant molecules (CTA(+)) in solution under appropriate conditions. After heating of this inorganic-surfactant lamellar composite material in an argon atmosphere to 850 degrees C, bulk quantities of uniform WS(2) nanotubes with diameters of 5-37.5 nm and lengths ranging from 0.2 to 5 microm were produced, which revealed a general rolling mechanism of layered sheets for tubule formation. The observations of transmission electron microscopy are in good agreement with the proposed rolling mechanism.     

Pulsed laser syntheses of layer-structured WS2 nanomaterials in water

We used water as an environmental friendly medium for the synthesis of hexagonal WS2 nanoparticles by the pulsed laser method. The materials collected on substrates were oriented with the 2H-WS2 basal planes parallel to the surface. The use of water, UV lasers, and large WS2 targets prevented the nanoparticles from restructuring into inorganic fullerenes, which were observed in research using hydrocarbon solvents, longer wavelength lasers, and dispersed powder targets. Fairly good dispersion of nanoparticles suggests that large surface areas are available for chemical reactivity.     

Reactions of a tungsten trisulfido complex of hydridotris(3,5-dimethylpyrazol-1-yl)borate (Tp*) [Et(4)N][Tp*WS(3)] with CuX (X = Cl, NCS, or CN): isolation, structures, and third-order NLO properties

Reactions of a tungsten trisulfido complex of hydridotris(3,5-dimethylpyrazol-1-yl)borate (Tp*) [Et4N][Tp*WS3] (1) with 3 equiv of CuCl in CHCl3 afforded a tetranuclear anionic cluster [Et4N][Tp*W(mu3-S)3(CuCl)3] (2), while that of 1 with 3 equiv of CuNCS in MeCN produced a decanuclear neutral cluster (major product) [Tp*W(mu3-S)3Cu3(mu-NCS)3(CuMeCN)]2 (3) along with a binuclear anionic cluster (minor product) [Et4N][Tp*WO(mu-S)2(CuNCS)] (4). Solvothermal reactions of 1 with 3 equiv of CuCN in MeCN at 80 degrees C for 48 h followed by slowly cooling it to ambient temperature gave rise to a polymeric cluster [Tp*W(mu3-S)(mu-S)2Cu2(MeCN)(mu-CN)]n (5). Compounds 2-5 were characterized by elemental analysis, IR, UV-vis, 1H NMR, and single-crystal X-ray crystallography. The cluster anion of 2 has a [Tp*WS3Cu3] incomplete cube with one Cl atom coordinated at each Cu center. 3 is composed of an unprecedented centrosymmetric W2Cu8 cluster core in which each void of the two single incomplete cubane-like [Tp*W(mu3-S)3Cu3(mu-NCS)]+ cations is partially filled with an extra [Cu(MeCN)(mu-NCS)2]- anion via a pair of Cu-mu-NCS-Cu bridges. The cluster anion of 4 contains one WS2Cu core that is formed by an oxidized [Tp*WO(mu-S)2] species and one CuNCS fragment. 5 consists of butterfly shaped [Tp*W(mu3-S)(mu-S)2Cu2(MeCN)] fragments that are interconnected via cyanide bridges to form a 1D spiral chain extending along the c axis. The successful synthesis of 2-5 from 1 suggests that 1 may be an excellent synthon to the W/Cu/S clusters. In addition, the third-order nonlinear optical (NLO) properties of 1-3 in solution were also investigated by femtosecond degenerate four-wave mixing (DFWM) technique with a 80 fs pulse width at 800 nm. Although 2 was not detected to have NLO effects, 1 and 3 exhibited relatively good optical nonlinearities with the nonlinear refractive index n2 and the third-order nonlinear optical susceptibility chi(3) values being 0.79 x 10(-13) and 0.38 x 10(-14) esu (1) and 2.08 x 10(-13) and 1.00 x 10(-14) esu (3), respectively. The second-order hyperpolarizability gamma value for 3 (5.46 x 10(-32) esu) is ca. 5 times larger than that of its precursor 1.     

Preparation and electrical conductivity of polypyrrole/WS2 layered nanocomposites

Lithium intercalated tungsten disulfide Li(x)WS(2) with x>1 was solvothermally obtained. It was revealed that Li(x)WS(2) can remain mostly unchanged under vacuum (about 4 kPa) for 5 days. The pH dependences of surface zeta potential for single molecular layers of WS(2) were determined, illustrating that its isoeletric point is approximately at pH 3. The polypyrrole/WS(2) layered nanocomposites were prepared via the combination of the exfoliation-restacking technique and in situ oxidative polymerization. The intercalation of PPy into the host galleries resulted in an interlayer expansion of about 3.7 A, which suggested that the intercalated polymeric chains are in a monolayer arrangement with the pyrrole rings lying parallel to the WS(2) host layers. The resulting material shows good thermal stability with the decomposition of the interacted chains within the disulfide galleries occurring at around 400 degrees C. The electrical conductivity of PPy/WS(2) nanocomposite was found to be high in the order of 10(-2) S cm(-1) at ambient temperature.     

WS_2/WO_3光催化选择性氧化苯甲醇制备苯甲醛

采用H2S高温硫化WO3的方法制备了一系列WS2/WO3光催化剂,利用X射线粉末衍射仪、紫外可见光谱仪分析了产物的结构及光吸收性能,考察了WS2/WO3光催化剂光催化选择性氧化苯甲醇制备苯甲醛的性能,讨论了WS2的含量、反应时间、反应液pH对光催化选择性氧化反应过程的影响.结果表明:与WO3和经深度硫化的WO3相比,适当的硫化能显著改善催化剂对苯甲醇的选择性氧化行为,反应时间及pH对苯甲醇的转化率及生成苯甲醛的选择性均有重要影响.