Na2WO4 Solution Research Articles

ChemInform Abstract: Polyol‐Mediated Low‐Temperature Synthesis of Crystalline Tungstate Nanoparticles MWO4 (M: Mn, Fe, Co, Ni, Cu, Zn).

AbstractThe title nanoparticles are prepared from diethylene glycol solutions of M(OAc)2 or Cu(NO3)2 by addition of aqueous Na2WO4 solution (pH 4.8—5.5, 220 °C, 1 h, <85% yield).

ChemInform Abstract: A One‐Step Hydrothermal Preparation Strategy for Layered BiIO4/Bi2WO6 Heterojunctions with Enhanced Visible Light Photocatalytic Activities.

AbstractLayered BiIO4/Bi2WO6 (2, 5, 10, and 15%) heterojunctions are prepared by hydrothermal processing of an aqueous suspension of Bi(NO3)3 and a I2O3, Na2WO4 solution (autoclave, 180 °C, 1 d).

ChemInform Abstract: First Stable Nitrate‐Encapsulated Sandwich Type Polyoxometalate: Synthesis, Structural Characterization, and Catalytic Performance.

AbstractNa4K5 [K3Cu3(NO3) (PW9O34)2] is synthesized from an aqueous solution of Na2WO4, Na2HPO4, Cu(NO3)2, and HCl (pH 7.5, 90 °C, 1 h followed by addition of KCl; 79% yield).

ChemInform Abstract: A Redox‐Triggered Structural Rearrangement in an Iodate‐Templated Polyoxotungstate Cluster Cage.

Abstract(TEAH)5Na [H5W18O59(IO3)] ·5H2O (I; TEAH: (HO‐CH2‐CH2)3NH+), the first example of a polyoxometalate with encapsulated IO3‐, is synthesized from an aqueous solution of Na2WO4, H5IO6, and TEAHCl (pH 1.3 adjusted with 6M HCl, reflux, 1 h; yield given in g).

One-step hydrothermal preparation of TiO2/WO3 nanocomposite films on anodized stainless steel for photocatalytic degradation of organic pollutants

TiO2/WO3 nanocomposite film was deposited on anodized stainless steel by one step hydrothermal reaction. Polished stainless steel foil was anodized to form nanopore arrays on the surface that is favorable for the immobilization of photocatalyst. The TiO2/WO3 nanocomposite film prepared in 0.01mol/L (NH4)2TiF6 and 0.0066mol/L Na2WO4 solution at 120°C for 3h exhibits the maximum photocatalytic activity, which is five times higher than that of pure TiO2 film and eight times higher than that of pure WO3 film. As compared with the pure TiO2 film, the main absorption edge of the WO3/TiO2 nanocomposite film shifts toward visible region and the absorption intensity is obviously improved. The nanocomposite film has a preferable crystallinity of anatase TiO2 and the monoclinic WO3, as revealed by X-ray diffraction and X-ray photoelectron spectroscopy. Scanning electron microscopy images show that the nanocomposite film is homogenous in size distribution and uniform in morphology. The high resolution transmission electron microscopy images further demonstrate the formation of mixed crystal between WO3 and TiO2 nanoparticles. The excellent photocatalytic activity of the nanocomposite film should be attributed to the formation of heterojunction between TiO2 and WO3 nanoparticles that can facilitate the separation of photo-generated electron–hole pairs.

Systematic Study of the Interaction Between VIV Centres and LnIII Ions in Well Defined {V 2 IV LnIII}{AsIIIW9O33}2 Sandwich-Type Clusters: Part 2

The gadolinium (Gd) member of a new type of heteropolytungstates that contain one lanthanide and two transition metal ions in a triangular arrangement is reported. The compound NaK6Gd0.33 [((VO)2Gd(H2O)4K2(H2O)2(Na)(H2O)2)(α-B-AsW9O33)2]·24H2O (1) was prepared from acidified aqueous solutions of Na2WO4·2H2O, As2O3 and VOSO4·5H2O to which Gd3+ ions were added. The single crystal X-ray structure analysis (monoclinic, space group P21/m) shows that the anion consists of two [α-B-AsIIIW9O33]9− trilacunary Keggin-type units linked by two VO2+, one Gd3+ as well as weakly by two K+ and one Na+ ions, resulting in a sandwich-type structure with idealized C 2v symmetry. The problem of positioning crystal lattice and special polyoxometalate sites with different cations is discussed also in connection with supramolecular chemistry aspects and as an option for further research. A fit of the magnetic susceptibility yielded exchange coupling constants of J VV = −2.55 cm−1 (anti-ferromagnetic) between the vanadium ions and J GdV = 0.6 cm−1 (ferromagnetic) between the Gd and each of the two vanadium ions. The complete magnetochemical analysis also revealed a partial occupancy of the Na+ sites in the counter-cation–water system by Gd3+ ions (0.33 Gd3+ ions in total).

ChemInform Abstract: Controlled Synthesis of PbWO4 Dendrites by a Simple Sonochemical Method.

AbstractPbWO4 dendrites are prepared by irradiation of an aqueous solution of K2C2O4, Na2WO4, and Pb(NO3)2 with a high‐intensity ultrasonic horn under ambient air.

ChemInform Abstract: Assembly of a Gigantic Polyoxometalate Cluster {W200Co8O660} in a Networked Reactor System.

Abstract{(Me2NH2)6 [H4CoW11O39] ·6H2O}n (I), Na4(Me2NH2)10 [H4CoW22O76(H2O)2] ·20H2O (II), and Na16(Me2NH2)72 [H16Co8W200O660 (H2O)40]·ca.600H2O (III) are synthesized in a networked reactor system (three primary reactors, each with two external reagent inputs, are connected together in a triangular arrangement with a central secondary reactor) from aqueous solutions of Na2WO4, CoCl2, Me2NH·HCl, Na2S2O4, and HCl.

Global kinetic evaluation during the reduction of CoWO4 with methane for the production of hydrogen

CoWO4 (CW) promoted with 10% Ni (CW–Ni) and 10% La2O3 (CW–La) were used as oxygen carriers in redox cycles of CH4/Ar and H2O/Ar to evaluate their global kinetics (reaction rate, order, constant and activation energy) with methane for the production of hydrogen. CoWO4 was synthesized by co-precipitation from equimolar solutions of Na2WO4 and Co(NO3)2 and calcined at 950 °C. Ni and La nitrate solutions were incorporated to CoWO4 by impregnation. Kinetic data was collected by thermogravimetric analysis (TGA) at 2, 5 and 8% CH4/Ar and at 850, 900 and 950 °C for two consecutive redox cycles. Oxidation was performed using 5% H2O/Ar at 900 °C. Results indicate a global first order reaction for the three materials. Activation energies during the first cycle for CW, CW–Ni and CW–La were 52.8, 32 and 33.4 kcal/mol, respectively, thus reflecting the influence of Ni and La2O3 in a greater reaction rate with respect to CW.

Pressure dependence of the Raman spectra of aqueous solutions and anthracene

The shifts of the main bands in the Raman spectra during isothermal pressurization up to 140 MPa for anthracene and 1 M solutions of NaClO4 and Na2WO4 are measured using an optical cell with sapphire windows. The resulting shifts in the maxima of the spectral bands (from 0.6 to 1.1 cm−1 per 100 MPa) are close to the published value for a 1 M Na2SO4 aqueous solution.

Hydrothermal Synthesis of Tungsten Oxide Nanoparticles

In the present paper, the tungsten oxide nanoparticles were fabricated via a hydrothermal treatment of the H2WO4 precursors. The H2WO4 precursors were prepared by method of precipitation reaction between aqueous Na2WO4 and HCl solution. The products are characterized in detail by multiform techniques: scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and energy-dispersive X-ray analysis. The results show that products are WO3 nanoparticles with diameter of about 100-150 nm.

ChemInform Abstract: Synthesis of Faceted β‐SnWO4 Microcrystals with Enhanced Visible‐Light Photocatalytic Properties.

AbstractHighly crystalline β‐SnWO4 truncated rhombic dodecahedrons with sharp edges and smooth faces are synthesized from a water‐in‐oil microemulsion loaded with a methanolic solution of SnCl2 and an aqueous solution of Na2WO4 (200 °C, 1 h, 50—60% yield).

Fabrication and characterization of WO3/Ag/WO3 multilayer transparent anode with solution-processed WO3 for polymer light-emitting diodes

The dielectric/metal/dielectric multilayer is suitable for a transparent electrode because of its high-optical and high-electrical properties; however, it is fabricated by an expensive and inefficient multistep vacuum process. We present a WO3/Ag/WO3 (WAW) multilayer transparent anode with solution-processed WO3 for polymer light-emitting diodes (PLEDs). This WAW multilayer not only has high transmittance and low resistance but also can be easily and rapidly fabricated. We devised a novel method to deposit a thin WO3 layer by a solution process in an air environment. A tungstic acid solution was prepared from an aqueous solution of Na2WO4 and then converted to WO3 nanoparticles (NPs) by a thermal treatment. Thin WO3 NP layers form WAW multilayer with a thermal-evaporated Ag layer, and they improve the transmittance of the WAW multilayer because of its high transmittance and refractive index. Moreover, the surface of the WO3 layer is homogeneous and flat with low roughness because of the WO3 NP generation from the tungstic acid solution without aggregation. We performed optical simulation and experiments, and the optimized WAW multilayer had a high transmittance of 85% with a sheet resistance of 4 Ω/sq. Finally, PLEDs based on the WAW multilayer anode achieved a maximum luminance of 35,550 cd/m2 at 8 V, and this result implies that the solution-processed WAW multilayer is appropriate for use as a transparent anode in PLEDs.

ChemInform Abstract: Efficient Synthesis of Plate‐Like Crystalline Hydrated Tungsten Trioxide Thin Films with Highly Improved Electrochromic Performance.

AbstractNanostructured 3WO3·H2O films are prepared by hydrothermal treatment of a crystal‐seed‐coated F‐doped tin oxide glass substrate and an aqueous Na2WO4 solution containing HCl, H2O2, and Na2SO4 as a capping agent (autoclave, 180 °C, 2 h).

Nanostructure and formation mechanism of Pt-WO3/C nanocatalyst by ethylene glycol method

Pt-WO3 nanoparticles uniformly dispersed on Vulcan XC-72R carbon black were prepared by an ethylene glycol method. The morphology, composition, nanostructure, electrochemical characteristics and electrocatalytic activity were characterized, and the formation mechanism was investigated. The average particle size was 2.3 nm, the same as that of Pt/C catalyst. The W/Pt atomic ratio was 1/20, much lower than the design of 1/3. The deposition of WO3·xH2O nanoparticles on Vulcan XC-72R carbon black was found to be very difficult by TEM. From XPS and XRD, the Pt nanoparticles were formed in the colloidal solution of Na2WO4, the EG insoluble Na2WO4 resulted in the decreased relative crystallinity and increased crystalline lattice constant compared with those of Pt/C catalyst and, subsequently, the higher specific electrocatalytic activity as determined by CV. The Pt-mass and Pt-electrochemically-active-specific-surface-area based anodic peak current densities for ethanol oxidation were 422.2 mA·mg−1Pt and 0.43 mA·cm−2Pt, 1.2 and 1.1 times higher than those of Pt/C catalyst, respectively.

Controllable synthesis and luminescent properties of three-dimensional nanostructured CaWO4:Tb3+ microspheres

Three-dimensional (3D) nanostructured CaWO4:Tb3+microspheres assembled by submicrospindles were synthesized via a mild sonochemical route from an aqueous solution of CaCl2, TbCl3 and Na2WO4 with the aid of surfactant Polyglycol 600 (PEG-600). The crystal structure and morphology of the as-prepared products were characterized by using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). Rietveld refinement was carried out on the XRD data. The results showed that the CaWO4:Tb3+nanoparticles can be formed without ultrasonic irradiation or addition of PEG-600. With continuously increasing irradiation time the submicrospindles and microspheres could be self-assembled. The central diameter and length of the submicrospindles are around 190 and 500nm, respectively. The 3D CaWO4:Tb3+nanostructured microspheres with diameter of 2–4μm were assembled by the submicrospindles. A possible formation mechanism for the 3D-structured CaWO4:Tb3+microspheres was proposed. The Photoluminescent (PL) properties of Tb3+ions in the nanostructured CaWO4 microspheres were studied. The energy transfer processes in CaWO4:Tb3+microspheres were analyzed. The electric dipole–dipole energy transfers related to 5D3 level were studied by inspecting the fluorescence decay of 5D3 level. The energy transfer critical distance was estimated.

Corrosion Resistance of Al<sub>2</sub>O<sub>3</sub>-ZrO<sub>2</sub> Composite Coating by Microarc Oxidation on 2A12 Aluminum Alloy

The Al2O3-ZrO2 composite ceramic coatings were prepared on 2A12 aluminum alloy by Microarc oxidation in the mixed electrolyte of 40g/L Na2SiO3 and 8g/L Na2WO4 solution containing different ZrO2 content particles. The thickness of the coatings was measured by an eddy current thickness meter. Microstructure and phase composition were analyzed by scanning election microscopy (SEM) and X-Ray diffraction (XRD), respectively. The experimental results show that ZrO2 in electrolyte can promote coatings growth; Al2O3-ZrO2 composite ceramic coatings consist of α-Al2O3, t-ZrO2, m-ZrO2, and ZrO2 is located in island-like discharge channels and does not destroy the integrity of composite coatings; There is scarcely any erosion on the surface of Al2O3-ZrO2 composite coatings because the intermediate product Zr(OH)4 could suppress composite coating corrosion.

ChemInform Abstract: Luminescence of Complex Ion WO18‐12 in Dy3+ Doped Nanocrystal Gd6WO12 Phosphor.

AbstractNanocrystalline Gd6WO12:Dy3+ phosphor is synthesized by coprecipitation from an aqueous solution of GdCl3, DyCl3 (molar ratio of 99:1), and Na2WO4 (pH < 12 adjusted with NH3, 30 min) followed by calcination at 900 °C for 4 h.

ChemInform Abstract: Self‐Assembly of a Nanosized, Saddle‐Shaped, Solution‐Stable Polyoxometalate Anion Built from Pentagonal Building Blocks: [H34W119Se8Fe2O420] 54‐.

AbstractK44Na10 [H34W119Se8Fe2O420] ·220 H2O is synthesized by slow evaporation of an aqueous solution of Na2WO4, Na2SeO3, KCl, and Fe(NO3)3 (AcOH, HCl, pH 1.7; 4% yield).

ChemInform Abstract: Growth of CaWO4 Crystals from M2WO4 (M: Li, Na, and K) Fluxes.

Calcium tungstate crystals were grown from M2WO4 (M=Li, Na, and K) fluxes. Observations of the obtained CaWO4 crystals showed that a high-temperature solution of Na2WO4 was superior to both Li2WO4 and K2WO4 solutions. It was experimentally confirmed that the Na2WO4 flux chosen on the basis of the guiding principle was the most suitable.