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Sample records for kyojiba wo riyoshita

  1. Improved visible light photocatalytic activity of WO3 through CuWO4 for phenol degradation

    NASA Astrophysics Data System (ADS)

    Chen, Haihang; Xiong, Xianqiang; Hao, Linlin; Zhang, Xiao; Xu, Yiming

    2016-12-01

    Development of a visible light photocatalyst is challenging. Herein, we report a significant activity enhancement of WO3 upon addition of CuWO4. Reaction was carried out under visible light for phenol degradation in aqueous suspension in the presence of H2O2. A maximum reaction rate was observed at 1.0 wt% CuWO4, which was 2.1 and 4.3 times those measured with WO3 and CuWO4, respectively. Similar results were also obtained from the photocatalytic formation of OH radicals, and from the electrochemical reduction of O2. A possible mechanism responsible for the improved activity of WO3 is proposed, involving the electron transfer from CuWO4 to WO3, followed by the reduction of H2O2 over WO3.

  2. PH Sensitive WO3-Based Microelectrochemical Transistors.

    DTIC Science & Technology

    1986-09-22

    a WO3 target. The cyclic voltammetry of these microelectrodes indicates that WO3 connects individual microelectrodes, since the voltammogram of a...transistor that is sensitive to pH. The cyclic voltammetry is pH-dependent and consistent with pH-dependent transistor characteristics, which indicate that the

  3. Synthesis and characterization of WO3 nanomaterials.

    PubMed

    Pandey, N K; Tiwari, Karunesh; Roy, Akash

    2011-02-01

    This work reports a simple, quick and economical method to prepare WO3 nanomaterials. Prepared tungsten trioxide materials have been sintered at 700 degrees C for three hours. The material has been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). Crystallite size of the WO3 nanostructures obtained by Shearer's formula are between 12 and 72 nm and their grain size by SEM are from 20 to 105 nm. The humidity-sensitive electrical properties of the WO3 nanomaterial have been studied using d.c. measurements.

  4. Metastable superconductivity of W/WO3 interface

    NASA Astrophysics Data System (ADS)

    Palnichenko, A. V.; Vyaselev, O. M.; Mazilkin, A. A.; Zver`kova, I. I.; Khasanov, S. S.

    2017-03-01

    Metastable W/WO3 interface has been formed at the surface of a tungsten metal bar using a solid state redox reaction of W with powdered WO3. Superconductivity at 35 ≤ T ≤ 75 K in the W/WO3 interfacial layer has been observed by means of the ac magnetic susceptibility and electrical resistance measurements. Comparative analysis of the experimental results infers that the W/WO3 interfacial layer consists of weakly linked superconducting regions.

  5. Growth of BaWO4 fishbone-like nanostructures in w/o microemulsion.

    PubMed

    Zhang, Xu; Xie, Yi; Xu, Fen; Tian, Xiaobo

    2004-06-01

    BaWO(4) fishbone-like nanostructures with fourfold structural symmetry have been successfully grown in w/o microemulsion. The BaWO(4) fishbone-like nanostructures have four rows of nanorods, epitaxially grown on the stem and perpendicular to the stem. The obtained samples are characterized by means of XRD, TEM, HRTEM, and SEM. It is found that the water content has a large influence on the size of the product and the molar ratio between cations and anions plays an important role in the morphology of the product. It is assumed that site-selective surfactant adsorption may be responsible for the formation of the BaWO(4) fishbone-like nanostructures.

  6. Reactivity of Hydrogen and Methanol on (001) Surfaces of WO3, ReO3, WO3/ReO3 and ReO3/WO3

    SciTech Connect

    Ling, Sanliang; Mei, Donghai; Gutowski, Maciej S.

    2011-05-16

    Bulk tungsten trioxide (WO3) and rhenium trioxide (ReO3) share very similar structures but display different electronic properties. WO3 is a wide bandgap semiconductor while ReO3 is an electronic conductor. With the advanced molecular beam epitaxy techniques, it is possible to make heterostructures comprised of layers of WO3 and ReO3. These heterostructures might display reactivity different than pure WO3 and ReO3. The interactions of two probe molecules (hydrogen and methanol) with the (001) surfaces of WO3, ReO3, and two heterostructures ReO3/WO3 and WO3/ReO3 were investigated at the density functional theory level. Atomic hydrogen prefers to adsorb at the terminal O1C sites forming a surface hydroxyl on four surfaces. Dissociative adsorption of a hydrogen molecule at the O1C site leads to formation of a water molecule adsorbed at the surface M5C site. This is thermodynamically the most stable state. A thermodynamically less stable dissociative state involves two surface hydroxyl groups O1CH and O2CH. The interaction of molecular hydrogen and methanol with pure ReO3 is stronger than with pure WO3 and the strength of the interaction substantially changes on the WO3/ReO3 and ReO3/WO3 heterostructures. The reaction barriers for decomposition and recombination reactions are sensitive to the nature of heterostructure. The calculated adsorption energy of methanol on WO3(001) of -65.6 kJ/mol is consistent with the previous experimental estimation of -67 kJ/mol. This material is based upon work supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences.

  7. Polarized Raman spectra of the oriented NaY(WO 4) 2 and KY(WO 4) 2 single crystals

    NASA Astrophysics Data System (ADS)

    Macalik, L.; Hanuza, J.; Kaminskii, A. A.

    2000-11-01

    Polarized Raman scattering spectra of the NaY(WO 4) 2 (NYW) single crystal have been measured. Its structure is described in the tetragonal space group isomorphic to CaWO 4 scheelite. The A g, B g and E g spectra were made and discussed in terms of factor group analysis. These spectra are compared to those of monoclinic KY(WO 4) 2 (KYW) single crystals whose structure differs from the other crystal. The NYW unit cell comprises of the isolated WO 4 tetrahedra whereas the KYW structure is built from the WO 6 octahedra joined by WO 2W double bonds and WOW single bridges. The vibrational characteristics of the bridge bond systems are proposed. On this basis, the role of the vibronic transitions for the KYW crystal doped with Eu 3+ ions is discussed.

  8. In situ synthesis of CdS/CdWO4/WO3 heterojunction films with enhanced photoelectrochemical properties

    NASA Astrophysics Data System (ADS)

    Zhan, Faqi; Li, Jie; Li, Wenzhang; Yang, Yahui; Liu, Wenhua; Li, Yaomin

    2016-09-01

    CdS/CdWO4/WO3 heterojunction films on fluorine-doped tin oxide (FTO) substrates are for the first time prepared as an efficient photoanode for photoelectrochemical (PEC) hydrogen generation by an in situ conversion process. The samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet visible spectrometry (UV-vis) and X-ray photoelectron spectroscopy (XPS). The CdS hollow spheres (∼80 nm) sensitized WO3 plate film with a CdWO4 buffer-layer exhibits increased visible light absorption and a significantly improved photoelectrochemical performance. The photocurrent density at 0 V (vs. Ag/AgCl) of the CdS/CdWO4/WO3 anode is ∼3 times higher than that of the CdWO4/WO3 anode, and ∼9 times higher than that of pure WO3 under illumination. The highest incident-photon-to-current-efficiency (IPCE) value increased from 16% to 63% when the ternary heterojunction was formed. This study demonstrates that the synthesis of ternary composite photocatalysts by the in situ conversion process may be a promising approach to achieve high photoelectric conversion efficiency.

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

    PubMed Central

    2012-01-01

    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. PMID:22587669

  10. Nd:SrWO 4 and Nd:BaWO 4 Raman lasers

    NASA Astrophysics Data System (ADS)

    Šulc, J.; Jelínková, H.; Basiev, T. T.; Doroschenko, M. E.; Ivleva, L. I.; Osiko, V. V.; Zverev, P. G.

    2007-09-01

    Properties of the laser operation and simultaneously stimulated Raman scattering in the SRS-active neodymium doped SrWO4 and BaWO4 crystals coherently end-pumped at wavelength 752 nm by pulsed free-running alexandrite laser radiation were investigated. The Nd3+ ion emission at wavelength λNd ˜ 1.06 μm was corresponding to 4F3/2 → 4I11/2 transition. To reach the SRS-self-conversion threshold inside Raman crystal the Nd3+ lasers were operating in a Q-switching regime. For Q-switching LiF:F2- crystal as a saturable absorber was used. Raman self-conversion at wavelength ˜1.17 μm was successfully reached with both tungstate crystals. The shortest generated pulse (1.3 ns FWHM) and highest peak power (615 kW) was obtained with Nd:BaWO4 Raman laser Q-switched by LiF:F2- crystal with initial transmission T0 = 60%. Up to 0.8 mJ was registered at the first Stokes wavelength 1169 nm. Using Q-switched Nd:SrWO4 laser higher energy in Raman emission was obtained (1.23 mJ) but generated pulse was longer (2.9 ns FWHM) resulting in lower peak power (430 kW).

  11. Nd:SrWO4 Raman laser

    NASA Astrophysics Data System (ADS)

    Jelinkova, Helena; Sulc, Jan; Doroschenko, Maxim E.; Skornyakov, Vadim V.; Kravtsov, Sergey B.; Basiev, Tasoltan T.; Zverev, Peter G.

    2004-09-01

    Properties of the laser operation and simultaneously stimulated Raman scattering in the new SRS-active neodymium doped SrWO4 crystal coherently end-pumped by alexandrite 752 nm laser radiation were investigated. The maximum generated energy 90 mJ from the free-running Nd3+:SrWO4 laser at 1057 nm wavelength was obtained with the output coupler reflectivity 52%. The slope efficiency reached s = 0.52, the beam characteristic parameters M2 and divergence q were 2.5 +/- 0.1, and 1.5 +/- 0.1 mrad, respectively. Maximal output energy of 1.46 mJ for the fundamental wavelength was obtained for Q-switched Nd3+:SrWO4 oscillator with a double Fabry-Perrot as the output coupler (R = 48%), and with the 5% initial transmission of LiF:F2- saturable absorber. Up to 0.74 mJ energy was registered at the first Stokes frequency. The pulse duration was 5 ns and 2.4 ns for the fundamental and Stokes radiation, respectively. The energy of 1.25 mJ at 1170 nm was obtained for closed Raman resonator with special mirrors. For the case of mode-locking, two dye saturable absorbers (ML51 dye in dichlorethan and 3955 dye in ethanol) were used and SRS radiation in the form of pulse train was observed. The influence of the various Raman laser output couplers reflectivity as well as the initial transmissions of passive absorbers were investigated with the goal of the output energy maximization at the Stokes wavelength. In the output, the total measured energy was 1.8 mJ (for ML51 dye) and 2.4 mJ (for 3955 dye). The SRS output at 1170 nm was approximately 20% of total energy.

  12. The green emission and local structure of the scintillator PbWO 4

    NASA Astrophysics Data System (ADS)

    Qi, Zeming; Shi, Chaoshu; Zhou, Dongfang; Tang, Honggao; Liu, Tao; Hu, Tiandou

    2001-12-01

    The green emission of lead tungstate (PbWO 4 ) is closely related to structure defects. For studying the mechanism of the green emission, the local structure of PbWO 4 has been first investigated by extended X-ray absorption fine structure using synchrotron radiation. The results indicate that the excess oxygen in air-annealed PbWO 4 exists and forms “WO 4+O i” centers. The green emission of PbWO 4 is not caused by (WO 3+F) centers, but probably originates from the centers of “WO 4+O i”.

  13. Synthesis of S-doped WO3 nanowires with enhanced photocatalytic performance towards dye degradation

    NASA Astrophysics Data System (ADS)

    Han, Fugui; Li, Heping; Fu, Li; Yang, Jun; Liu, Zhong

    2016-05-01

    In this letter, S-doped WO3 nanowires (S-WO3) were prepared using a hydrothermal method followed by a low-temperature solid-state annealing treatment. The synthesized S-WO3 was characterized by SEM, EDX, XRD, XPS, Raman spectroscopy, UV-vis DRS and photocurrent responses. The results indicated that S could enhance the light harvesting capacity of WO3 nanowires. The photocatalytic performance of the S-WO3 was investigated by photodegradation of methyl orange (MO) under visible light irradiation. Results demonstrated that the photocatalytic activity of the S-WO3 nanowires is much higher than that of pure WO3 nanowires.

  14. WO3 nanopaticles and PEDOT:PSS/WO3 composite thin films studied for photocatalytic and electrochromic applications

    NASA Astrophysics Data System (ADS)

    Ivanov Boyadjiev, Stefan; Manduca, Bruno; Szűcs, Júlia; Miklós Szilágyi, Imre

    2016-03-01

    WO3 is a widely studied material for electrochromic and photocatalytic applications. In the present study, WO3 nanoparticles with a controlled structure (monoclinic or hexagonal) were obtained by controlled thermal decomposition of hexagonal ammonium tungsten bronze in air at 500 °C and 600 °C, respectively. The formation, morphology, structure and composition of the as-prepared nanoparticles were studied by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDX). The photocatalytic activity of the monoclinic and hexagonal WO3 nanoparticles was studied by decomposing methyl orange in aqueous solution under UV light irradiation. In order to study the electrochromic properties of the WO3 nanoparticles, as well to introduce them for self-cleaning photocatalytic surface applications, thin films were prepared from the WO3 particles together with a conductive polymer. For this, PEDOT:PSS was used, which gives excellent opportunities for obtaining transparent and conductive thin films, suitable for both electrochromic and photocatalytic applications. By spin-coating, transparent PEDOT:PSS/WO3 composite thin films were prepared, on which cyclic voltammetry measurements were performed, and the coloring and bleaching states were studied. Our initial results for the PEDOT:PSS/WO3 composite thin films are promising, suggesting that such composites, after further development, might be successfully used in electrochromic devices and photocatalysis.

  15. Photoluminescence in solid solutions and thin films of tungstates CaWO{sub 4}-CdWO{sub 4}

    SciTech Connect

    Taoufyq, A.; Mauroy, V.; Guinneton, F.; Valmalette, J-C.; Fiorido, T.; Benlhachemi, A.; Lyoussi, A.; Nolibe, G.; Gavarri, J-R.

    2015-07-01

    In this study, we present two types of studies on the luminescence properties under UV and X-ray excitations of solid solutions Ca{sub 1-x}Cd{sub x}WO{sub 4} and of thin layers of CaWO{sub 4} and CdWO{sub 4}. These tungstate based solid solutions are susceptible to be integrated into new radiation sensors, in order to be used in different fields of applications such as reactor measurements, safeguards, homeland security, nuclear nondestructive assays, LINAC emission radiation measurement. However these complex materials were rarely investigated in the literature. One first objective of our studies was to establish correlations between luminescence efficiency, chemical substitution and the degree of crystallization resulting from elaboration conditions. A second objective will be to determine the efficiency of luminescence properties of thin layers of these materials. In the present work, we focus our attention on the role of chemical substitution on photon emissions under UV and X-ray irradiations. The luminescence spectra of Ca{sub 1-x}Cd{sub x}WO{sub 4} polycrystalline materials have been investigated at room temperature as a function of composition (0≤x≤1). In addition, we present a preliminary study of the luminescence of CaWO{sub 4} and CdWO{sub 4} thin layers: oscillations observed in the case of X-ray excitations in the luminescence spectra are discussed. (authors)

  16. Photocatalytic properties of h-WO3 nanoparticles obtained by annealing and h-WO3 nanorods prepared by hydrothermal method

    NASA Astrophysics Data System (ADS)

    Boyadjiev, Stefan I.; Nagy-Kovács, Teodóra; Lukács, István; Szilágyi, Imre M.

    2016-03-01

    In the present study, two different methods for preparing hexagonal WO3 (h-WO3) photocatalysts were used - controlled thermal decomposition and hydrothermal synthesis. WO3 nanoparticles with hexagonal structure were obtained by annealing (NH4)xWO3-y at 500 °C in air. WO3 nanorods were prepared by a hydrothermal method using sodium tungstate Na2WO4, HCl, (COOH)2 and NaSO4 precursors at 200 °C. The formation, morphology, structure and composition of the as-prepared nanoparticles and nanorods were studied by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDX). The photocatalytic activity of the h-WO3 nanoparticles and nanorods was studied by decomposing methyl orange in aqueous solution under UV light irradiation.

  17. Large single crystal growth of MnWO4-type materials from high-temperature solutions

    NASA Astrophysics Data System (ADS)

    Gattermann, U.; Röska, B.; Paulmann, C.; Park, S.-H.

    2016-11-01

    A simple high-temperature growth apparatus was constructed to obtain large crystals of chemically gradient (In, Na)-doped MnWO4solid-solutions. This paper presents the crystal growth and characterisation of both MnWO4and epitaxially grown (In, Na): MnWO4crystals on MnWO4. These large monolithic crystals were made in two steps: A MnWO4 crystal was grown in the crystallographic main direction [001] applying the Czochralski method, followed by the top seeded growth of (In, Na): MnWO4 solid-solutions with an oriented seed crystal of MnWO4. Such a monolithic crystal will serve to fundamental investigation of coupling properties at boundaries between various multiferroic MnWO4-typesolid-solutions.

  18. Improved red emission by codoping Li+ in ZnWO4:Eu3+ phosphors

    NASA Astrophysics Data System (ADS)

    Chen, Guiqiang; Wang, Fengli; Yu, Jie; Zhang, Haisheng; Zhang, Xiao

    2017-01-01

    ZnWO4:Eu3+ and ZnWO4:Eu3+/Li+ phosphors have been synthesized successfully by a microwave-assist hydrothermal process. The phase, morphology and luminescent properties are investigated carefully. The XRD and FTIR results indicate that ZnWO4:Eu3+ and ZnWO4:Eu3+/Li+ phosphors have the monoclinic phase. The SEM images indicate that ZnWO4:Eu3+ and ZnWO4:Eu3+/Li+ phosphors are cubes with average particle size about 1 μm. Under the excitation at 395 nm, ZnWO4:Eu3+ and ZnWO4:Eu3+/Li+ phosphors show emission bands originating from the 5D0 → 7Fj (j = 0, 1, 2 and 3) transitions of Eu3+ ions. The Li+ ion acts as charge compensator and results in the enhancement of emission intensity.

  19. Preparation and physical properties of CuxWO3

    NASA Astrophysics Data System (ADS)

    Koriche, N.; Bessekhouad, Y.; Bouguelia, A.; Trari, M.

    2012-04-01

    We report on the study of WO3 doped with Cu using sol-gel (CuxWO3d) and impregnation (CuxWO3i) methods. All materials are well crystallized and exhibit single phases whose crystallite size ranges from 17 to 100 nm depending on Cu amount and the preparation technique. The conductivity dependence on temperature demonstrates semiconductor behavior and follows the Arrhenius model, with activation energies, Eσ, commonly in the range 0.4-0.6 eV. Moreover, the thermopower study shows that CuxWO3d is mainly of p-type conductivity, whereas CuxWO3i is n-type. The mechanism of conduction is attributed to a small polaron hopping. The doping process is found to decrease the interband transition down to 520 nm depending on the preparation conditions. The photoelectrochemical characterization confirms the conductivity type and demonstrates that the photocurrent Jph increases with Cu-doping. Taking into consideration the activation energy, the flat band potential and the band gap energy, the band positions of each material are proposed according to the preparation method and Cu amount.

  20. Synthesis of high aspect ratio WO2 nanostructures

    NASA Astrophysics Data System (ADS)

    Coşkun, Selim; Koziol, Krzysztof K. K.

    2016-02-01

    Tungsten oxide (WO2) nanorods and nanowires were prepared by the heat treatment of WO2 nanocrystalline powders in the presence of Ar. Nanocrystalline powders produced by a simple water-assisted route at the room temperature were annealed at different temperatures for different durations, which yielded orthorhombic and monoclinic WO2 crystals. Annealing the powders at 700 °C and above resulted in orthorhombic WO2 nanorods/nanowires with an average diameter of 60-70 nm beside the monoclinic WO2 nanocrystalline powders with a diameter of 5 nm. The lengths of the nanorods increased from several 100 nm up to several 10 µm with increasing temperature while their diameters did not change. With increased length, nanowires became more elastic in nature having a cotton-like fabric. The prepared nanostructures have been characterized by X-ray powder diffraction measurements, scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. An oriented attachment mechanism leading to root growth from a parent structure was proposed.

  1. Photocatalytic activity of Bi2WO6/Bi2S3 heterojunctions: the facilitation of exposed facets of Bi2WO6 substrate

    NASA Astrophysics Data System (ADS)

    Yan, Long; Wang, Yufei; Shen, Huidong; Zhang, Yu; Li, Jian; Wang, Danjun

    2017-01-01

    Bi2S3/Bi2WO6 hybrid architectures with exposed (020) Bi2WO6 facets have been synthesized via a controlled anion exchange approach. X-ray photoelectron spectroscopy (XPS) reveals that a small amount of Bi2S3 was formed on the surface of Bi2WO6 during the anion exchange process, thus leading to the transformation from the Bi2WO6 to Bi2S3/Bi2WO6. A rhodamine B (RhB) aqueous solution was chosen as model organic pollutants to evaluate the photocatalytic activities of the Bi2S3/Bi2WO6 catalysts. Under visible light irradiation, the Bi2S3/Bi2WO6-TAA displayed the excellent visible light photoactivities compared with pure Bi2S3, Bi2WO6 and other composite photocatalysts. The efficient photocatalytic activity of the Bi2S3/Bi2WO6-TAA composite microspheres was ascribed to the constructed heterojunctions and the inner electric field caused by the exposed (020) Bi2WO6 facets. Active species trapping experiments revealed that h+ and O2rad - are the main active species in the photocatalytic process. Furthermore, the as-obtained photocatalysts showed good photocatalytic activity after four recycles. The results presented in this study provide a new concept for the rational design and development of highly efficient photocatalysts.

  2. Degradation of methylene blue using porous WO3, SiO2-WO3, and their Au-loaded analogs: adsorption and photocatalytic studies.

    PubMed

    DePuccio, Daniel P; Botella, Pablo; O'Rourke, Bruce; Landry, Christopher C

    2015-01-28

    A facile sonochemical approach was used to deposit 3-5 nm monodisperse gold nanoparticles on porous SiO2-WO3 composite spheres, as confirmed by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). High-resolution TEM (HR-TEM) and energy dispersive X-ray spectroscopy (EDS) further characterized the supported Au nanoparticles within the Au-SiO2-WO3 composite. These analyses showed isolated Au nanoparticles within both SiO2- and WO3-containing regions. Selective etching of the SiO2 matrix from Au-SiO2-WO3 yielded a pure Au-WO3 material with well-dispersed 10 nm Au nanoparticles and moderate porosity. This combined sonochemical-nanocasting technique has not been previously used to synthesize Au-WO3 photocatalysts. Methylene blue (MB) served as a probe for the adsorption capacity and visible light photocatalytic activity of these WO3-containing catalysts. Extensive MB demethylation (azures A, B, C, and thionine) and polymerization of these products occurred over WO3 under dark conditions, as confirmed by electrospray ionization mass spectrometry (ESI-MS). Photoirradiation of these suspensions led to further degradation primarily through demethylation and polymerization pathways, regardless of the presence of Au nanoparticles. Ring-opening sulfur oxidation to the sulfone was a secondary photocatalytic pathway. According to UV-vis spectroscopy, pure WO3 materials showed superior MB adsorption compared to SiO2-WO3 composites. Compared to their respective nonloaded catalysts, Au-SiO2-WO3 and Au-WO3 catalysts exhibited enhanced visible light photocatalytic activity toward the degradation of MB. Specifically, the rates of MB degradation over Au-WO3 and Au-SiO2-WO3 during 300 min of irradiation were faster than those over their nonloaded counterparts (WO3 and SiO2-WO3). These studies highlight the ability of Au-WO3 to serve as an excellent adsorbant and photodegradation catalyst toward MB.

  3. Intrinsic Defects and H Doping in WO3

    PubMed Central

    Zhu, Jiajie; Vasilopoulou, Maria; Davazoglou, Dimitris; Kennou, Stella; Chroneos, Alexander; Schwingenschlögl, Udo

    2017-01-01

    WO3 is widely used as industrial catalyst. Intrinsic and/or extrinsic defects can tune the electronic properties and extend applications to gas sensors and optoelectonics. However, H doping is a challenge to WO3, the relevant mechanisms being hardly understood. In this context, we investigate intrinsic defects and H doping by density functional theory and experiments. Formation energies are calculated to determine the lowest energy defect states. O vacancies turn out to be stable in O-poor environment, in agreement with X-ray photoelectron spectroscopy, and O-H bond formation of H interstitial defects is predicted and confirmed by Fourier transform infrared spectroscopy. PMID:28098210

  4. Intrinsic Defects and H Doping in WO3

    NASA Astrophysics Data System (ADS)

    Zhu, Jiajie; Vasilopoulou, Maria; Davazoglou, Dimitris; Kennou, Stella; Chroneos, Alexander; Schwingenschlögl, Udo

    2017-01-01

    WO3 is widely used as industrial catalyst. Intrinsic and/or extrinsic defects can tune the electronic properties and extend applications to gas sensors and optoelectonics. However, H doping is a challenge to WO3, the relevant mechanisms being hardly understood. In this context, we investigate intrinsic defects and H doping by density functional theory and experiments. Formation energies are calculated to determine the lowest energy defect states. O vacancies turn out to be stable in O-poor environment, in agreement with X-ray photoelectron spectroscopy, and O-H bond formation of H interstitial defects is predicted and confirmed by Fourier transform infrared spectroscopy.

  5. Facile Hydrogen Evolution Reaction on WO3Nanorods

    PubMed Central

    2007-01-01

    Tungsten trioxide nanorods have been generated by the thermal decomposition (450 °C) of tetrabutylammonium decatungstate. The synthesized tungsten trioxide (WO3) nanorods have been characterized by XRD, Raman, SEM, TEM, HRTEM and cyclic voltammetry. High resolution transmission electron microscopy and X-ray diffraction analysis showed that the synthesized WO3nanorods are crystalline in nature with monoclinic structure. The electrochemical experiments showed that they constitute a better electrocatalytic system for hydrogen evolution reaction in acid medium compared to their bulk counterpart.

  6. Reactive Sputter Deposition of WO3/Ag/WO3 Film for Indium Tin Oxide (ITO)-Free Electrochromic Devices.

    PubMed

    Yin, Yi; Lan, Changyong; Guo, Huayang; Li, Chun

    2016-02-17

    Functioning both as electrochromic (EC) and transparent-conductive (TC) coatings, WO3/Ag/WO3 (WAW) trilayer film shows promising potential application for ITO-free electrochromic devices. Reports on thermal-evaporated WAW films revealed that these bifunctional WAW films have distinct EC characteristics; however, their poor adhesive property leads to rapid degradation of coloring-bleaching cycling. Here, we show that WAW film with improved EC durability can be prepared by reactive sputtering using metal targets. We find that, by introducing an ultrathin tungsten (W) sacrificial layer before the deposition of external WO3, the oxidation of silver, which leads to film insulation and apparent optical haze, can be effectively avoided. We also find that the luminous transmittance and sheet resistance were sensitive to the thicknesses of tungsten and silver layers. The optimized structure for TC coating was obtained to be WO3 (45 nm)/Ag (10 nm)/W (2 nm)/WO3 (45 nm) with a sheet resistance of 16.3 Ω/□ and a luminous transmittance of 73.7%. Such film exhibits compelling EC performance with decent luminous transmittance modulation ΔTlum of 29.5%, fast switching time (6.6 s for coloring and 15.9 s for bleaching time), and long-term cycling stability (2000 cycles) with an applied potential of ±1.2 V. Thicker external WO3 layer (45/10/2/100 nm) leads to larger modulation with maximum ΔTlum of 46.4%, but at the cost of significantly increasing the sheet resistance. The strategy of introducing ultrathin metal sacrificial layer to avoid silver oxidation could be extended to fabricating other oxide-Ag-oxide transparent electrodes via low-cost reactive sputtering.

  7. Multiple Horizontal Transfers of Bacteriophage WO and Host Wolbachia in Fig Wasps in a Closed Community

    PubMed Central

    Wang, Ningxin; Jia, Sisi; Xu, Heng; Liu, Yong; Huang, Dawei

    2016-01-01

    Wolbachia-bacteriophage WO is a good model system for studying interactions between bacteria and viruses. Previous surveys of insect hosts have been conducted via sampling from open or semi-open communities; however, no studies have reported the infection patterns of phage WO of insects living in a closed community. Figs and fig wasps form a peculiar closed community in which the Ficus tree provides a compact syconium habitat for a variety of fig wasp. Therefore, in this study, we performed a thorough survey of Wolbachia and bacteriophage WO infection patterns in a total of 1406 individuals from 23 fig wasps species living on three different fig tree species. The infection rates of Wolbachia and phage WO were 82.6% (19/23) and 39.1% (9/23), respectively. Additionally, phage WO from fig wasps showed strong insect host specificity based on orf7 sequences from fig wasps and 21 other insect species. Probably due to the physical barrier of fig syconium, most phage WO from fig wasps form a specific clade. Phylogenetic analysis showed the absence of congruence between WO and host Wolbachia, WO and insect host, as well as Wolbachia and fig wasps, suggesting that both Wolbachia and phage WO exchanged frequently and independently within the closed syconium. Thus, the infection pattern of bacteriophage WO from fig wasps appeared quite different from that in other insects living outside, although the effect and the transfer routes of phage WO are unclear, which need to be investigated in the future. PMID:26913026

  8. Multiple Horizontal Transfers of Bacteriophage WO and Host Wolbachia in Fig Wasps in a Closed Community.

    PubMed

    Wang, Ningxin; Jia, Sisi; Xu, Heng; Liu, Yong; Huang, Dawei

    2016-01-01

    Wolbachia-bacteriophage WO is a good model system for studying interactions between bacteria and viruses. Previous surveys of insect hosts have been conducted via sampling from open or semi-open communities; however, no studies have reported the infection patterns of phage WO of insects living in a closed community. Figs and fig wasps form a peculiar closed community in which the Ficus tree provides a compact syconium habitat for a variety of fig wasp. Therefore, in this study, we performed a thorough survey of Wolbachia and bacteriophage WO infection patterns in a total of 1406 individuals from 23 fig wasps species living on three different fig tree species. The infection rates of Wolbachia and phage WO were 82.6% (19/23) and 39.1% (9/23), respectively. Additionally, phage WO from fig wasps showed strong insect host specificity based on orf7 sequences from fig wasps and 21 other insect species. Probably due to the physical barrier of fig syconium, most phage WO from fig wasps form a specific clade. Phylogenetic analysis showed the absence of congruence between WO and host Wolbachia, WO and insect host, as well as Wolbachia and fig wasps, suggesting that both Wolbachia and phage WO exchanged frequently and independently within the closed syconium. Thus, the infection pattern of bacteriophage WO from fig wasps appeared quite different from that in other insects living outside, although the effect and the transfer routes of phage WO are unclear, which need to be investigated in the future.

  9. Tripartite associations among bacteriophage WO, Wolbachia, and host affected by temperature and age in Tetranychus urticae.

    PubMed

    Lu, Ming-Hong; Zhang, Kai-Jun; Hong, Xiao-Yue

    2012-11-01

    A phage density model of cytoplasmic incompatibility (CI), which means lytic phages reduce bacterial density associated with CI, significantly enhances our understanding of the tripartite associations among bacteriophage WO, Wolbachia and host. However, WO may alternate between lytic and lysogenic life cycles or change phage production under certain conditions including temperature, host age and host species background. Here, extreme temperatures can induce an alteration in the life cycle of WO and change the tripartite associations among WO, Wolbachia and CI. Based on the accumulation of the WO load, WO can transform into the lytic life cycle with increasing age. These findings confirmed that the environment plays an important role in the associations among WO, Wolbachia and host.

  10. Tunable luminescence and enhanced photocatalytic activity for Eu(III) doped Bi2WO6 nanoparticles.

    PubMed

    Gu, Haidong; Yu, Lei; Wang, Juan; Ni, Min; Liu, Tingting; Chen, Feng

    2017-04-15

    A series of Eu(III) doped Bi2WO6 nanoparticles were synthesized by a hydrothermal process. The obtained Bi2WO6:Eu(III) nanoparticles were characterized by XRD, SEM, luminescence spectrophotometer and DRS. The XRD and TEM results indicate that the Eu(III) doping concentration has no influence on the phase and morphology. However, the Eu(III) doping can tune the luminescence and enhance the photocatalytic activity of Bi2WO6. With the increases of Eu(3+) doping concentrations, the emission intensity of WO6(6-) group decreases nut the photocatalytic activity increases. The tunable luminescence of Bi2WO6:Eu(III) nanoparticles results from the energy transfer from WO6(6-) group to Eu(III) ion. The enhanced performance can be ascribed to efficient separation of electron and hole pairs after doping Eu(III) into the Bi2WO6 lattice.

  11. Tunable luminescence and enhanced photocatalytic activity for Eu(III) doped Bi2WO6 nanoparticles

    NASA Astrophysics Data System (ADS)

    Gu, Haidong; Yu, Lei; Wang, Juan; Ni, Min; Liu, Tingting; Chen, Feng

    2017-04-01

    A series of Eu(III) doped Bi2WO6 nanoparticles were synthesized by a hydrothermal process. The obtained Bi2WO6:Eu(III) nanoparticles were characterized by XRD, SEM, luminescence spectrophotometer and DRS. The XRD and TEM results indicate that the Eu(III) doping concentration has no influence on the phase and morphology. However, the Eu(III) doping can tune the luminescence and enhance the photocatalytic activity of Bi2WO6. With the increases of Eu3 + doping concentrations, the emission intensity of WO66 - group decreases nut the photocatalytic activity increases. The tunable luminescence of Bi2WO6:Eu(III) nanoparticles results from the energy transfer from WO66 - group to Eu(III) ion. The enhanced performance can be ascribed to efficient separation of electron and hole pairs after doping Eu(III) into the Bi2WO6 lattice.

  12. Synthesis of a highly reactive form of WO2Cl2, its conversion into nanocrystalline mono-hydrated WO3 and coordination compounds with tetramethylurea.

    PubMed

    Bortoluzzi, Marco; Evangelisti, Claudio; Marchetti, Fabio; Pampaloni, Guido; Piccinelli, Fabio; Zacchini, Stefano

    2016-10-21

    A new form of WO2Cl2 was obtained by modification of a literature procedure. Both the newly prepared WO2Cl2 and the commercial yellow WO2Cl2 exhibited an orthorhombic structure (powder X-ray diffraction, P-XRD), and their air exposure at room temperature afforded light green and lemon yellow WO3·H2O (orthorhombic phase), respectively. These materials were characterized by P-XRD, high-resolution transmission electron microscopy (HR-TEM) and scanning transmission electron microscopy (S-TEM). The analyses revealed the nanocrystalline nature of light green WO3·H2O, and the prevalent amorphism of lemon yellow WO3·H2O. The reactions of grey WO2Cl2 with one and two equivalents of tetramethylurea (tmu), in CH2Cl2 at room temperature, led to the isolation of the trinuclear complex [WO2Cl2(tmu)]3, 1 (45% yield), and the mononuclear one WO2Cl2(tmu)2, 2 (64%), respectively. Compounds 1 and 2 were fully characterized by analytical and spectroscopic methods, single crystal X-ray diffraction (SC-XRD) and DFT calculations.

  13. Current and voltage noise in WO3 nanoparticle films

    NASA Astrophysics Data System (ADS)

    Hoel, A.; Vandamme, L. K. J.; Kish, L. B.; Olsson, E.

    2002-04-01

    Current and voltage noise measurements have been carried out on nanoparticle WO3 films. The fluctuation dissipation theorem holds, which indicates that the observed noise is an equilibrium phenomenon. Results on the thinnest films show that noise measurements can be used for quality assessment of nanocrystalline insulating films.

  14. Morphologically different WO3 nanocrystals in photoelectrochemical water oxidation

    NASA Astrophysics Data System (ADS)

    Biswas, Soumya Kanti; Baeg, Jin-Ook; Moon, Sang-Jin; Kong, Ki-jeong; So, Won-Wook

    2012-01-01

    Different morphologies of WO3 nanocrystals such as nanorods and nanoplates have been obtained under hydrothermal conditions using ammonium metatungstate as the precursor in presence of different organic acids such as citric, oxalic, and tartaric acid in the reaction medium. Detailed characterization of the crystal structure, particle morphology, and optical band gap of the synthesized powders have been done by X-ray diffraction, transmission electron microscopy, scanning electron microscopy and solid-state UV-visible spectroscopy study. The as-synthesized materials are WO3 hydrates with orthorhombic phase which transform to the hexagonal WO3 through dehydration upon heating at 350 °C. The resultant products are crystalline with nanoscale dimensions. Finally, the photoactivity of the synthesized materials annealed at 500 °C has been compared employing in photoelectrochemical water oxidation under the illumination of AM 1.5G simulated solar light (100 mWcm-2). The photocurrent measurements upon irradiation of light exhibit obvious photocatalytic activity with a photocurrent of about 0.77, 0.61, and 0.65 mAcm-2 for the WO3 film derived with the oxalic acid, tartaric, and citric acid assisting agents, respectively, at 1.8 V versus Ag/AgCl electrode.

  15. Tungsten-based nanomaterials (WO3 & Bi2WO6): Modifications related to charge carrier transfer mechanisms and photocatalytic applications

    NASA Astrophysics Data System (ADS)

    Girish Kumar, S.; Koteswara Rao, K. S. R.

    2015-11-01

    Heterogeneous photocatalysis is an ideal green energy technology for the purification of wastewater. Although titania dominates as the reference photocatalyst, its wide band gap is a bottleneck for extended utility. Thus, search for non-TiO2 based nanomaterials has become an active area of research in recent years. In this regard, visible light absorbing polycrystalline WO3 (2.4-2.8 eV) and Bi2WO6 (2.8 eV) with versatile structure-electronic properties has gained considerable interest to promote the photocatalytic reactions. These materials are also explored in selective functional group transformation in organic reactions, because of low reduction and oxidation potential of WO3 CB and Bi2WO6 VB, respectively. In this focused review, various strategies such as foreign ion doping, noble metal deposition and heterostructuring with other semiconductors designed for efficient photocatalysis is discussed. These modifications not only extend the optical response to longer wavelengths, but also prolong the life-time of the charge carriers and strengthen the photocatalyst stability. The changes in the surface-bulk properties and the charge carrier transfer dynamics associated with each modification correlating to the high activity are emphasized. The presence of oxidizing agents, surface modification with Cu2+ ions and synthesis of exposed facets to promote the degradation rate is highlighted. In depth study on these nanomaterials is likely to sustain interest in wastewater remediation and envisaged to signify in various green energy applications.

  16. WO{sub 3} nanoplates, hierarchical flower-like assemblies and their photocatalytic properties

    SciTech Connect

    Huang, Jianhua Xiao, Liang; Yang, Xiaolong

    2013-08-01

    Graphical abstract: WO{sub 3} nanoplates, hierarchical flower-like assemblies and their visible light-driven photocatalytic properties for degradation of rhodamine B. - Highlights: • Preparation of monoclinic WO{sub 3} by a hydrothermal reaction of PbWO{sub 4} in the presence of HNO{sub 3}. • Single-crystalline WO{sub 3} nanoplates were formed when 4 M HNO{sub 3} solution was used. • WO{sub 3} flowers were assembled by nanoplates when 15 M HNO{sub 3} solution was used. • The products showed excellent visible light-driven photodegradation of rhodamine B. - Abstract: Monoclinic WO{sub 3} was prepared by a hydrothermal reaction of PbWO{sub 4} in the presence of HNO{sub 3}. WO{sub 3} rectangular nanoplates with a side length of 50–150 nm and a thickness of about 25 nm were obtained at 4 M HNO{sub 3} solution. And the single crystal nature was confirmed by the selected area electron diffraction. Whereas WO{sub 3} hierarchical flower-like assemblies with 3–5 μm in diameter were self-organized by nanoplates in the presence of 15 M HNO{sub 3} solution. Compared with commercial WO{sub 3} particles, our products showed an enhancement of photocatalytic properties for the degradation of rhodamine B under visible light irradiation.

  17. Preparation and characterization of WO3 nanoparticles, WO3/TiO2 core/shell nanocomposites and PEDOT:PSS/WO3 composite thin films for photocatalytic and electrochromic applications

    NASA Astrophysics Data System (ADS)

    Boyadjiev, Stefan I.; Santos, Gustavo dos Lopes; Szżcs, Júlia; Szilágyi, Imre M.

    2016-03-01

    In this study, monoclinic WO3 nanoparticles were obtained by thermal decomposition of (NH4)xWO3 in air at 600 °C. On them by atomic layer deposition (ALD) TiO2 films were deposited, and thus core/shell WO3/TiO2 nanocomposites were prepared. We prepared composites of WO3 nanoparticles with conductive polymer as PEDOT:PSS, and deposited thin films of them on glass and ITO substrates by spin coating. The formation, morphology, composition and structure of the as-prepared pure and composite nanoparticles, as well thin films, were studied by TEM, SEM-EDX and XRD. The photocatalytic activity of both the WO3 and core/shell WO3/TiO2 nanoparticles was studied by decomposing methyl orange in aqueous solution under UV light irradiation. Cyclic voltammetry measurements were performed on the composite PEDOT:PSS/WO3 thin films, and the coloring and bleaching states were studied.

  18. Enhancement of the photocatalytic activity and electrochemical property of graphene-SrWO4 nanocomposite

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoyan; Nie, Yu; Yang, Hongxun; Sun, Shengnan; Chen, Yingying; Yang, Tongyi; Lin, Shengling

    2016-05-01

    SrWO4 is a promising candidate as not only photocatalyst for the removal of organic pollutants from water, but also electrode material for energy storage devices. However, the drawbacks of its poor adsorptive performance, low electrical conductivity, and high recombination rate of photogenerated electron-hole pair impede its practical applications. In this work, we have developed a new graphene/SrWO4 nanocomposite synthesized via a facile chemical precipitation method. Characterizations show that SrWO4 nanoparticles with 80 nm or so deposited on the surface of graphene nanosheets. Graphene nanosheets in the graphene-SrWO4 hybrid could increase adsorptive property, improve the electrical conductivity of hybrid, and reduce the recombination of electron-hole pairs. As a kind of photocatalyst or electrode material for supercapacitor, the binary graphene-SrWO4 hybrid presents enhanced photocatalytic activity and electrochemical property compared to pure SrWO4.

  19. Facile synthesis of hierarchical double-shell WO3 microspheres with enhanced photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Wang, Zhenfeng; Chu, Deqing; Wang, Limin; Wang, Lipeng; Hu, Wenhui; Chen, Xiangyu; Yang, Huifang; Sun, Jingjing

    2017-02-01

    Hierarchical double-shell WO3 microspheres (HDS-WO3) have been successfully obtained through the thermal decomposition of WO3·H2O formed by metal salts as the templates. The products were characterized by X-ray diffraction (XRD), and the morphology was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, the HDS-WO3 microspheres were analyzed by the Thermogravimetric (TG) and Brunauer-Emmett-Teller (BET) analysis. The synthetic mechanism of the products with hierarchical structures was proposed. The obtained HDS-WO3 exhibits excellent photocatalytic efficiency (84.9%), which is much higher than other WO3 sample under visible light illumination.

  20. NixWO2.72 nanorods as an efficient electrocatalyst for oxygen evolution reaction

    DOE PAGES

    Xi, Zheng; Mendoza-Garcia, Adriana; Zhu, Huiyuan; ...

    2017-01-13

    NixWO2.72 nanorods (NRs) are synthesized by a one-pot reaction of Ni(acac)2 and WCl4. In the rod structure, Ni(II) intercalates in the defective perovskite-type WO2.72 and is stabilized. The NixWO2.72 NRs show the x-dependent electrocatalysis for the oxygen evolution reaction (OER) in 0.1M KOH with Ni0.78WO2.72 being the most efficient, even outperforming the commercial Ir-catalyst. Lastly, the synthesis is not limited to NixWO2.72 but can be extended to MxWO2.72 (M = Co, Fe) as well, providing a new class of oxide-based catalysts for efficient OER and other energy conversion reactions.

  1. Photocatalytic Removal of Microcystin-LR by Advanced WO3-Based Nanoparticles under Simulated Solar Light

    PubMed Central

    Zhao, Chao; Li, Dawei; Feng, Chuanping; Zhang, Zhenya; Sugiura, Norio; Yang, Yingnan

    2015-01-01

    A series of advanced WO3-based photocatalysts including CuO/WO3, Pd/WO3, and Pt/WO3 were synthesized for the photocatalytic removal of microcystin-LR (MC-LR) under simulated solar light. In the present study, Pt/WO3 exhibited the best performance for the photocatalytic degradation of MC-LR. The MC-LR degradation can be described by pseudo-first-order kinetic model. Chloride ion (Cl−) with proper concentration could enhance the MC-LR degradation. The presence of metal cations (Cu2+ and Fe3+) improved the photocatalytic degradation of MC-LR. This study suggests that Pt/WO3 photocatalytic oxidation under solar light is a promising option for the purification of water containing MC-LR. PMID:25884038

  2. Snake River Plain FORGE Well Data for WO-2

    DOE Data Explorer

    Robert Podgorney

    1991-07-29

    Well data for the WO-2 well located in eastern Snake River Plain, Idaho. This data collection includes lithology reports, borehole logs, temperature at depth data, neutron density and gamma data, and rock strength parameters for the WO-2 well. This collection of data has been assembled as part of the site characterization data used to develop the conceptual geologic model for the Snake River Plain site in Idaho, as part of phase 1 of the Frontier Observatory for Research in Geothermal Energy (FORGE) initiative. They were assembled by the Snake River Geothermal Consortium (SRGC), a team of collaborators that includes members from national laboratories, universities, industry, and federal agencies, lead by the Idaho National Laboratory (INL).

  3. Invasion noise in nanoparticle WO3/Au thin film devices

    NASA Astrophysics Data System (ADS)

    Hoel, Anders; Ederth, Jesper; Heszler, Peter; Kish, Laszlo B.; Olsson, Eva; Granqvist, Claes-Goeran

    2001-11-01

    Conduction noise measurements were carried out in the 0.3 to 45 Hz frequency range on Au films covered by a thin layer of tungsten trioxide (WO3) nanoparticles. Exposing the films to alcohol vapor resulted in a gradually increased noise intensity which went through a maximum after an exposure time of the order of 15 min. The maximum noise intensity could increase by several orders of magnitude above the initial level. Longer exposure times made the noise decrease and approach its original value. This effect was not observed in the absence of WO3 nanoparticles. The phenomenon is discussed in terms of a new invasion noise model in which the noise is related to the insertion and extraction of mobile chemical species.

  4. Light-controlled resistive switching of ZnWO{sub 4} nanowires array

    SciTech Connect

    Zhao, W. X.; Sun, B.; Liu, Y. H.; Wei, L. J.; Li, H. W.; Chen, P.

    2014-07-15

    ZnWO{sub 4} nanowires array was prepared on the titanium substrate by a facile hydrothermal synthesis, in which the average length of ZnWO{sub 4} nanowires is about 2um and the diameter of individual ZnWO{sub 4} nanowire ranges from 50 to 70 nm. The bipolar resistive switching effect of ZnWO{sub 4} nanowires array was observed. Moreover, the performance of the resistive switching device is greatly improved under white light irradiation compared with that in the dark.

  5. Ag Nanoparticle-Sensitized WO3 Hollow Nanosphere for Localized Surface Plasmon Enhanced Gas Sensors.

    PubMed

    Yao, Yao; Ji, Fangxu; Yin, Mingli; Ren, Xianpei; Ma, Qiang; Yan, Junqing; Liu, Shengzhong Frank

    2016-07-20

    Ag nanoparticle (NP)-sensitized WO3 hollow nanospheres (Ag-WO3-HNSs) are fabricated via a simple sonochemical synthesis route. It is found that the Ag-WO3-HNS shows remarkable performance in gas sensors. Field-emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM) images reveal that the Agx-WO3 adopts the HNS structure in which WO3 forms the outer shell framework and the Ag NPs are grown on the inner wall of the WO3 hollow sphere. The size of the Ag NPs can be controlled by adjusting the addition amount of WCl6 during the reaction. The sensor Agx-WO3 exhibits extremely high sensitivity and selectivity toward alcohol vapor. In particular, the Ag(15nm)-WO3 sensor shows significantly lower operating temperature (230 °C), superior detection limits as low as 0.09 ppb, and faster response (7 s). Light illumination was found to boost the sensor performance effectively, especially at 405 and 900 nm, where the light wavelength resonates with the absorption of Ag NPs and the surface oxygen vacancies of WO3, respectively. The improved sensor performance is attributed to the localized surface plasmon resonance (LSPR) effect.

  6. Metastable Tetragonal CdWO4 Nanoparticles Synthesized with a Solvothermal Method

    SciTech Connect

    Rondinone, Adam Justin; Travaglini, Dustin H; Pawel, Michelle D; Mahurin, Shannon Mark; Dai, Sheng

    2007-01-01

    CdWO{sub 4} has only previously been reported in the monoclinic, or wolframite, phase. Here we report the first metastable, tetragonal or scheelite, CdWO4 nanopowder. The tetragonal CdWO{sub 4} was synthesized by a propylene glycol solvothermal method. The scheelite phase is stabilized by a combination of high surface area and surface complexation by the propylene glycol. The CdWO{sub 4} is stable at 1 bar to 300 C, and converts back to the monoclinic wolframite phase between 300 and 500 C. The nanopowder exhibits cubic morphology and the average particle size of the nanopowder is around 50 nm.

  7. Surface oxygen vacancies on WO3 contributed to enhanced photothermo-synergistic effect

    NASA Astrophysics Data System (ADS)

    Li, Yingying; Wang, Changhua; Zheng, Han; Wan, Fangxu; Yu, Fei; Zhang, Xintong; Liu, Yichun

    2017-01-01

    Photothermooxidation has demonstrated a high efficiency in the removal of volatile organic compounds in air. Among photothermocatalysts, attention is presently focused on composites of noble metal/metal oxide or metal oxide/metal oxide. Instead, in this work, we present a case of single oxide WO3 subjected to hydrogen treatment as photothermocatalyst. With the increase of hydrogen treatment temperature, the color of WO3 changes from yellow to blue to dark blue and a phase transition from WO3 to WO2.72 to WO2 is accompanied, suggesting an increase of concentration of oxygen vacancy. Photothermocatalytic test against degradation of gaseous acetaldehyde at 60 °C under UV light shows that WO3-x sample with low concentration of oxygen vacancy displays the most significant synergetic effect between photocatalysis and thermocatalysis. Its photothermocatalytic activity in terms of CO2 evolution rate is 5.2 times higher than that of photocatalytic activity. However, WO3-WO2.72 and WO2 with high degree of oxygen deficiency show insignificant synergetic effect between photocatalysis and thermocatalysis. The reason for the different synergistic effect over above samples is believed to lie in balance between decreased activation energy of lattice oxygen and recombination of photogenerated electrons and holes induced by oxygen deficiency.

  8. Synthesis and ionic liquid gating of hexagonal WO{sub 3} thin films

    SciTech Connect

    Wu, Phillip M. E-mail: beasley@stanford.edu; Munakata, Ko; Hammond, R. H.; Geballe, T. H.; Beasley, M. R. E-mail: beasley@stanford.edu; Ishii, Satoshi; Tanabe, Kenji; Tokiwa, Kazuyasu

    2015-01-26

    Via thin film deposition techniques, the meta-stable in bulk crystal hexagonal phase of tungsten oxide (hex-WO{sub 3}) is stabilized as a thin film. The hex-WO{sub 3} structure is potentially promising for numerous applications and is related to the structure for superconducting compounds found in WO{sub 3}. Utilizing ionic liquid gating, carriers were electrostatically induced in the films and an insulator-to-metal transition is observed. These results show that ionic liquid gating is a viable technique to alter the electrical transport properties of WO{sub 3}.

  9. First-principles reinvestigation of bulk WO3

    NASA Astrophysics Data System (ADS)

    Hamdi, Hanen; Salje, Ekhard K. H.; Ghosez, Philippe; Bousquet, Eric

    2016-12-01

    Using first-principles calculations, we analyze the structural properties of tungsten trioxide WO3. Our calculations rely on density functional theory and the use of the B1-WC hybrid functional, which provides very good agreement with experimental data. We show that the hypothetical high-symmetry cubic reference structure combines several ferroelectric and antiferrodistortive (antipolar cation motions, rotations, and tilts of oxygen octahedra) structural instabilities. Although the ferroelectric instability is the largest, the instability related to antipolar W motions combines with those associated to oxygen rotations and tilts to produce the biggest energy reduction, yielding a P 21/c ground state. This nonpolar P 21/c phase is only different from the experimentally reported P c ground state by the absence of a very tiny additional ferroelectric distortion. The calculations performed on a stoichiometric compound so suggest that the low-temperature phase of WO3 is not intrinsically ferroelectric and that the experimentally observed ferroelectric character might arise from extrinsic defects such as oxygen vacancies. Independently, we also identify never observed R 3 m and R 3 c ferroelectric metastable phases with large polarizations and low energies close to the P 21/c ground state, which makes WO3 a potential antiferroelectric material. The relative stability of various phases is discussed in terms of the anharmonic couplings between different structural distortions, highlighting a very complex interplay.

  10. Eukaryotic association module in phage WO genomes from Wolbachia

    PubMed Central

    Bordenstein, Sarah R.; Bordenstein, Seth R.

    2016-01-01

    Viruses are trifurcated into eukaryotic, archaeal and bacterial categories. This domain-specific ecology underscores why eukaryotic viruses typically co-opt eukaryotic genes and bacteriophages commonly harbour bacterial genes. However, the presence of bacteriophages in obligate intracellular bacteria of eukaryotes may promote DNA transfers between eukaryotes and bacteriophages. Here we report a metagenomic analysis of purified bacteriophage WO particles of Wolbachia and uncover a eukaryotic association module in the complete WO genome. It harbours predicted domains, such as the black widow latrotoxin C-terminal domain, that are uninterrupted in bacteriophage genomes, enriched with eukaryotic protease cleavage sites and combined with additional domains to forge one of the largest bacteriophage genes to date (14,256 bp). To the best of our knowledge, these eukaryotic-like domains have never before been reported in packaged bacteriophages and their phylogeny, distribution and sequence diversity imply lateral transfers between bacteriophage/prophage and animal genomes. Finally, the WO genome sequences and identification of attachment sites will potentially advance genetic manipulation of Wolbachia. PMID:27727237

  11. Improvement of radiopurity level of enriched 116CdWO4 and ZnWO4 crystal scintillators by recrystallization

    NASA Astrophysics Data System (ADS)

    Barabash, A. S.; Belli, P.; Bernabei, R.; Borovlev, Yu. A.; Cappella, F.; Caracciolo, V.; Cerulli, R.; Danevich, F. A.; Incicchitti, A.; Kobychev, V. V.; Konovalov, S. I.; Laubenstein, M.; Mokina, V. M.; Polischuk, O. G.; Safonova, O. E.; Shlegel, V. N.; Tretyak, V. I.; Tupitsyna, I. A.; Umatov, V. I.; Zhdankov, V. N.

    2016-10-01

    As low as possible radioactive contamination of a detector plays a crucial role to improve sensitivity of a double beta decay experiment. The radioactive contamination of a sample of 116CdWO4 crystal scintillator by thorium was reduced by a factor ≈10, down to the level 0.01 mBq/kg (228Th), by exploiting the recrystallization procedure. The total alpha activity of uranium and thorium daughters was reduced by a factor ≈3, down to 1.6 mBq/kg. No change in the specific activity (the total α activity and 228Th) was observed in a sample of ZnWO4 crystal produced by recrystallization after removing ≈0.4 mm surface layer of the crystal.

  12. Temperature and acidity effects on WO{sub 3} nanostructures and gas-sensing properties of WO{sub 3} nanoplates

    SciTech Connect

    Zhang, Huili; Liu, Zhifang; Yang, Jiaqin; Guo, Wei; Zhu, Lianjie; Zheng, Wenjun

    2014-09-15

    Graphical abstract: Generally, large acid quantity and high temperature are beneficial to the formation of anhydrous WO3, but the acidity effect on the crystal phase is weaker than that of temperature. Large acid quantity is found helpful to the oriented growth of tungsten oxides, forming a nanoplate-like product. - Highlights: • Large acid quantity is propitious to the oriented growth of a WO{sub 3} nanoplate. • Effect of acid quantity on crystal phases of products is weaker than that of temperature. • One step hydrothermal synthesis of WO{sub 3} is facile and can be easily scaled up. • A WO{sub 3} nanoplate shows a fast response and distinct sensing selectivity to acetone gas. - Abstract: WO{sub 3} nanostructures were successfully synthesized by a facile hydrothermal method using Na{sub 2}WO{sub 4}·2H{sub 2}O and HNO{sub 3} as raw materials. They are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The specific surface area was obtained from N{sub 2} adsorption–desorption isotherm. The effects of the amount of HNO{sub 3}, hydrothermal temperature and reaction time on the crystal phases and morphologies of the WO{sub 3} nanostructures were investigated in detail, and the reaction mechanism was discussed. Large amount of acid is found for the first time to be helpful to the oriented growth of tungsten oxides, forming nanoplate-like products, while hydrothermal temperature has more influence on the crystal phase of the product. Gas-sensing properties of the series of as-prepared WO{sub 3} nanoplates were tested by means of acetone, ethanol, formaldehyde and ammonia. One of the WO{sub 3} nanoplates with high specific surface area and high crystallinity displays high sensitivity, fast response and distinct sensing selectivity to acetone gas.

  13. Annealing dynamics of WO{sub 3} by in situ XRD

    SciTech Connect

    Righettoni, Marco; Pratsinis, Sotiris E.

    2014-11-15

    Highlights: • Flame-made WO{sub 3} nanoparticles with closely controlled crystal and grain size. • Dynamic phase transition of annealing of pure and Si-doped WO{sub 3} by in situ XRD. • Irreversible evolution of WO{sub 3} crystallinity by heating/cooling during its annealing. • Si-doping alters the WO{sub 3} crystallinity dynamics and stabilizes nanosized WO{sub 3}. • Flame-made nano-WO{sub 3} can sense NO at the ppb level. - Abstract: Tungsten trioxide is a semiconductor with distinct applications in gas sensors, catalysis, batteries and pigments. As such the transition between its different crystal structures during its annealing are of interest, especially for sensor applications. Here, WO{sub 3} nanoparticles with closely controlled crystal and grain size (9–15 nm) and phase composition are made by flame spray pyrolysis and the formation of different WO{sub 3} phases during annealing is investigated. Most notably, the dynamic phase transition and crystal size evolution of WO{sub 3} during heating and cooling is monitored by in situ X-ray diffraction revealing how metastable WO{sub 3} phases can be captured stably. The effect of Si-doping is studied since it is used in practise to control crystal growth and phase transition during metal oxide synthesis and processing. Finally the influence of annealing on the WO{sub 3} sensing performance of NO, a lung inflammation tracer in the human breath, is explored at the ppb-level.

  14. Effect of crystallization water on the structural and electrical properties of CuWO{sub 4} under high pressure

    SciTech Connect

    Wang, Li; Yan, Jiejuan; Liu, Cailong; Liu, Xizhe; Han, Yonghao E-mail: cc060109@qq.com; Gao, Chunxiao E-mail: cc060109@qq.com; Ke, Feng; Wang, Qinglin; Li, Yanchun; Ma, Yanzhang

    2015-11-16

    The effect of crystallization water on the structural and electrical properties of CuWO{sub 4} under high pressure has been investigated by in situ X-ray diffraction and alternating current impedance spectra measurements. The crystallization water was found to be a key role in modulating the structural stability of CuWO{sub 4} at high pressures. The anhydrous CuWO{sub 4} undergoes two pressure-induced structural transitions at 8.8 and 18.5 GPa, respectively, while CuWO{sub 4}·2H{sub 2}O keeps its original structure up to 40.5 GPa. Besides, the crystallization water makes the electrical transport behavior of anhydrous CuWO{sub 4} and CuWO{sub 4}·2H{sub 2}O quite different. The charge carrier transportation is always isotropic in CuWO{sub 4}·2H{sub 2}O, but anisotropic in the triclinic and the third phase of anhydrous CuWO{sub 4}. The grain resistance of CuWO{sub 4}·2H{sub 2}O is always larger than that of anhydrous CuWO{sub 4} in the entire pressure range. By analyzing the relaxation response, we found that the large number of hydrogen bonds can soften the grain characteristic frequency of CuWO{sub 4}·2H{sub 2}O over CuWO{sub 4} by one order of magnitude.

  15. Congruence of Behavioral Symptomatology in Children with ADD/H, ADD/WO, and Learning Disabilities.

    ERIC Educational Resources Information Center

    Stanford, Lisa D.; Hynd, George W.

    1994-01-01

    This study compared parent and teacher behavioral ratings for 77 children (ages 5-16) diagnosed as having attention deficit disorder with hyperactivity (ADD/H), attention deficit disorder without hyperactivity (ADD/WO), or learning disabilities (LD). ADD/WO and LD children were rated similarly on symptoms of withdrawal and impulsivity but differed…

  16. Optical properties of WO{sub 3} thin films using surface plasmon resonance technique

    SciTech Connect

    Paliwal, Ayushi; Sharma, Anjali; Gupta, Vinay E-mail: vgupta@physics.du.ac.in; Tomar, Monika

    2014-01-28

    Indigenously assembled surface plasmon resonance (SPR) technique has been exploited to study the thickness dependent dielectric properties of WO{sub 3} thin films. WO{sub 3} thin films (80 nm to 200 nm) have been deposited onto gold (Au) coated glass prism by sputtering technique. The structural, optical properties and surface morphology of the deposited WO{sub 3} thin films were studied using X-ray diffraction, UV-visible spectrophotometer, Raman spectroscopy, and Scanning electron microscopy (SEM). XRD analysis shows that all the deposited WO{sub 3} thin films are exhibiting preferred (020) orientation and Raman data indicates that the films possess single phase monoclinic structure. SEM images reveal the variation in grain size with increase in thickness. The SPR reflectance curves of the WO{sub 3}/Au/prism structure were utilized to estimate the dielectric properties of WO{sub 3} thin films at optical frequency (λ = 633 nm). As the thickness of WO{sub 3} thin film increases from 80 nm to 200 nm, the dielectric constant is seen to be decreasing from 5.76 to 3.42, while the dielectric loss reduces from 0.098 to 0.01. The estimated value of refractive index of WO{sub 3} film is in agreement to that obtained from UV-visible spectroscopy studies. The strong dispersion in refractive index is observed with wavelength of incident laser light.

  17. Correlation between surface chemistry, density and band gap in nanocrystalline WO3 thin films

    SciTech Connect

    Vemuri, Venkata Rama Ses; Engelhard, Mark H.; Ramana, C.V.

    2012-03-01

    Nanocrystalline WO3 thin films were produced by sputter-deposition by varying the ratio of argon to oxygen in the reactive gas mixture during deposition. The surface chemistry, physical characteristics, and optical properties of nanocrystalline WO3 films were evaluated using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray reflectivity (XRR), and spectrophotometric measurements. The effect of ultra-microstructure was significant on the optical properties of WO3 films. The XPS analyses indicate the formation of stoichiometric WO3 with tungsten existing in fully oxidized valence state (W6+). However, WO3 films grown at high oxygen concentration (>60%) in the sputtering gas mixture were over stoichiometric with excess oxygen. XRR simulations, which are based on isotropic WO3 film - SiO2 interface - Si substrate model, indicate that the density of WO3 films is sensitive to the oxygen content in the sputtering gas. The spectral transmission of the films increased with the increasing oxygen. The band gap of these films increases from 2.78 eV to 3.25 eV with increasing oxygen. A direct correlation between the film-density and band gap in nanocrystalline WO3 films is established based on the observed results.

  18. Detecting hydrogen using graphene quantum dots/WO3 thin films

    NASA Astrophysics Data System (ADS)

    Fardindoost, Somayeh; Iraji zad, Azam; Sadat Hosseini, Zahra; Hatamie, Shadie

    2016-11-01

    In the present work we report an approach to resistive hydrogen sensing based on graphene quantum dots (GQDs)/WO3 thin films that work reproducibly at low temperatures. GQDs were chemically synthesized and evenly dispersed in WO3 solution with 1:1 molar ratio. The structural evaluation and crystallization of the prepared films was studied by x-ray diffraction, Raman and scanning electron microscopy (SEM) techniques. The SEM images showed uniform distribution of the GQDs in WO3 films with sizes around 50 nm. Raman experiment showed the GQDs are partially reduced with high edge defects as hydroxyl and carboxyl groups which involve both in bridging between WO3 grains via bindings as well as interacting with target gas molecules. GQDs can develop an electron conductive network and shorten the current transport paths inside the sensitive films. As a result, they improved the poor electrical properties and charge transfer of pure WO3. Resistive hydrogen sensing showed significant decrease in the working temperature for GQDs/WO3 films compared to pure WO3 films. The working temperature of about 150 °C with 15 and 40 s response and recovery times are significant characteristics of the introduced sensing structure. Then palladium (Pd) was added as a catalyst in GQDs/WO3 film to make the sensing materials selective to hydrogen. Pd doped film worked at temperature of 120 °C with high selectivity and improved response magnitude to hydrogen gas.

  19. Strain Accommodation By Facile WO6 Octahedral Distortion and Tilting During WO3 Heteroepitaxy on SrTiO3(001)

    SciTech Connect

    Du, Yingge; Gu, Meng; Varga, Tamas; Wang, Chong M.; Bowden, Mark E.; Chambers, Scott A.

    2014-08-27

    In this paper, we show that compared to other BO6 octahedra in ABO3 structured perovskite oxides, the WO6 octahedra in tungsten trioxide (WO3) can withstand a much larger degree of distortion and tilting to accommodate interfacial strain, which in turn strongly impact the nucleation, structure, and defect formation during the epitaxial growth of WO3 on SrTiO3(001). A meta-stable tetragonal phase can be stabilized by epitaxy and a thickness dependent phase transition (tetragonal to monoclinic) is observed. In contrast to misfit dislocations to accommodate the interfacial stain, the facial WO6 octahedral distortion and tilting give rise to three types of planar defects that affect more than 15 monolayers from the interface. These atomically resolved, unusual interfacial defects may significantly alter the electronic, electrochromic, and mechanical properties of the epitaxial films.

  20. Microwave-assisted synthesis and photocatalytic properties of flower-like Bi2WO6 and Bi2O3-Bi2WO6 composite.

    PubMed

    Li, Zhao-Qian; Chen, Xue-Tai; Xue, Zi-Ling

    2013-03-15

    Flower-like Bi(2)WO(6) and Bi(2)O(3)-Bi(2)WO(6) composite microstructures have been synthesized via a facile and rapid microwave-assisted hydrothermal method through controlling the experimental parameters. The phases and morphologies of the products are characterized by powder X-ray diffraction (XRD), energy dispersion X-ray analysis (EDX), high resolution transmission electron microscopy (HRTEM), and scanning electron microscopy (SEM). Photocatalytic experiments indicate that such Bi(2)O(3)-Bi(2)WO(6) composite possesses higher photocatalytic activity for RhB degradation under visible-light irradiation in comparison with pure Bi(2)O(3) and Bi(2)WO(6). On the basis of the calculated energy band positions, the enhanced photocatalytic activity is attributed to the effective separation of electron-hole pairs between the two semiconductors. The present study provides a new strategy to design composite materials with enhanced photocatalytic activity.

  1. High photocatalytic capability of self-assembled nanoporous WO3 with preferential orientation of (002) planes.

    PubMed

    Guo, Yafeng; Quan, Xie; Lu, Na; Zhao, Huimin; Chen, Shuo

    2007-06-15

    Self-assembled nanoporous tungsten oxide (WO3) with preferential orientation (002) planes was successfully synthesized on the tungsten sheet by anodization in a 0.2 wt % NaF and 0.3% (V/V) HF mixture solution in a 1:1 ratio. The pores, of a highly ordered self-assembled structure, had an average size of approximately 70 nm. X-ray diffraction identified a monoclinic WO3 structure and fine preferential orientation of (002) planes. A maximum photoconversion efficiency of 17.2% was obtained for the self-assembled nanoporous WO3 under high-pressure mercury lamp illumination. The photocatalytic (PC) degradation of pentachlorophenol (PCP) in aqueous solution using the self-assembled nanoporous WO3 photocatalyst, performed under both high-pressure mercury lamp and Xe lamp illumination, showed more excellent PC capability than WO3 film and TiO2 nanotube arrays.

  2. Characterization of MAPLE deposited WO3 thin films for electrochromic applications

    NASA Astrophysics Data System (ADS)

    Boyadjiev, S. I.; Stefan, N.; Szilágyi, I. M.; Mihailescu, N.; Visan, A.; Mihailescu, I. N.; Stan, G. E.; Besleaga, C.; Iliev, M. T.; Gesheva, K. A.

    2017-01-01

    Tungsten trioxide (WO3) is a widely studied material for electrochromic applications. The structure, morphology and optical properties of WO3 thin films, grown by matrix assisted pulsed laser evaporation (MAPLE) from monoclinic WO3 nano-sized particles, were investigated for their possible application as electrochromic layers. A KrF* excimer (λ=248 nm, ζFWHM=25 ns) laser source was used in all experiments. The MAPLE deposited WO3 thin films were studied by atomic force microscopy (AFM), grazing incidence X-ray diffraction (GIXRD) and Fourier transform infrared spectroscopy (FTIR). Cyclic voltammetry measurements were also performed, and the coloring and bleaching were observed. The morpho-structural investigations disclosed the synthesis of single-phase monoclinic WO3 films consisting of crystalline nano-grains embedded in an amorphous matrix. All thin films showed good electrochromic properties, thus validating application of the MAPLE deposition technique for the further development of electrochromic devices.

  3. Gamma-ray irradiation induced bulk photochromism in WO3-P2O5 glass

    NASA Astrophysics Data System (ADS)

    Shen, Wei; Baccaro, Stefania; Cemmi, Alessia; Xu, Xiaoqing; Chen, Guorong

    2015-11-01

    In the present work, photochromism of WO3-P2O5 glass under gamma-ray irradiation was reported. As-prepared glass samples with different WO3 content are all optically transparent in the visible wavelength range thanks to the addition of a small amount of oxidizing couple Sb2O3-NaNO3. The photochromic properties are identified by transmission spectra of the glasses before and after irradiation. The results show that the irradiation induced darkening results from the reduction of W6+ to W5+ or W4+. The existence of WO6 clusters in glasses of high WO3 content is proved by XPS, which is the main reason for the obvious photochromic effects. The WO3-P2O5 glass is a promising candidate in gamma-ray sensitive detector.

  4. Photoelectron spectromicroscopy study of metal-insulator transition in NaxWO3

    NASA Astrophysics Data System (ADS)

    Paul, Sanhita; Ghosh, Anirudha; Dudin, Pavel; Barinov, Alexei; Chakraborty, Anirban; Ray, Sugata; Sarma, D. D.; Oishi, Shuji; Raj, Satyabrata

    2013-07-01

    We have investigated the validity of percolation model, which is quite often invoked to explain the metal-insulator transition in sodium tungsten bronzes, NaxWO3 by photoelectron spectromicroscopy. The spatially resolved direct spectromicroscopic probing on both the insulating and metallic phases of high quality single crystals of NaxWO3 reveals the absence of any microscopic inhomogeneities embedded in the system within the experimental limit. Neither any metallic domains in the insulating host nor any insulating domains in the metallic host have been found to support the validity of percolation model to explain the metal-insulator transition in NaxWO3. The possible origin of insulating phase in NaxWO3 is due to the Anderson localization of all the states near EF. The localization occurs because of the strong disorder arising from random distribution of Na+ ions in the WO3 lattice.

  5. Photoactivity and stability of Ag2WO4 for organic degradation in aqueous suspensions

    NASA Astrophysics Data System (ADS)

    Chen, Haihang; Xu, Yiming

    2014-11-01

    Silver tungstate as photocatalyst for water splitting and dye degradation has been reported, but the catalyst stability is not known. In this work, we find that both α- and β-Ag2WO4 are not stable under UV light for the photocatalytic degradation of phenol and azo-dye X3B in aqueous solutions. Comparatively, β-Ag2WO4 was more photoactive, but less stable than α-Ag2WO4. Solid characterization with X-ray diffraction and scanning electron microscope showed that metallic silver particles were produced with the two catalysts, consequently resulting into decrease in the activity for organic degradation. Measurement of photoluminescence revealed that β-Ag2WO4 had a weaker band gap emission and higher portion of structural defects than α-Ag2WO4. A possible mechanism responsible for the observed difference in photoactivity and stability between the two tungstates is proposed.

  6. MWCNT/WO{sub 3} nanocomposite photoanode for visible light induced water splitting

    SciTech Connect

    Yousefzadeh, Samira; Reyhani, Ali; Naseri, Naimeh; Moshfegh, Alireza Z.

    2013-08-15

    The Multi-walled carbon nanotube (MWCNT)/WO{sub 3} nanocomposite thin films with different MWCNT’s weight percentages were prepared by sol–gel method as visible light induced photoanode in water splitting reaction. Weight percentage of MWCNT in the all nanocomposite thin films was confirmed by TGA/DSC analysis. According to XPS analysis, oxygenated groups at the surface of the MWCNT and stoichiometric formation of WO{sub 3} thin films were determined, while the crystalline structure of the nanocomposite samples was studied by XRD indicating (0 0 2) peak of MWCNT in the monoclinic phase of WO{sub 3}. The influence of different weight percentage (wt%) of MWCNT on WO{sub 3} photoactivity showed that the electron conductivity, charge transfer and electron life time had improved as compared with the pure WO{sub 3}. Based on linear sweep voltammetry and chronoamperometry measurements, the (1 wt%) MWCNT/WO{sub 3} nanocomposite thin films photoanode has a maximum photocurrent density of ∼4.5 A/m{sup 2} and electron life time of about 57 s. - Graphical abstract: Photocurrent density versus time at constant potential (0.7 V) for the WO{sub 3} films containing different MWCNT weight percentages annealed at 400 °C under 1000 Wm{sup −2} visible photo-illumination. Display Omitted - Highlights: • MWCNT/ WO{sub 3} nanocomposite thin films were synthesized using sol–gel derived method. • TGA/DSC confirmed the weight percentage of MWCNT in the all nanocomposite thin films. • XPS analysis revealed that WO{sub 3} was attached on the oxygenated group of MWCNT surface. • The Highest Photoelectrochemical activity is achieved for (1 wt%)MWCNT/WO{sub 3} thin film.

  7. Epitaxial growth of high quality WO3 thin films

    DOE PAGES

    Leng, X.; Pereiro, J.; Strle, J.; ...

    2015-09-09

    We have grown epitaxial WO3 films on various single-crystal substrates using radio-frequency (RF) magnetron sputtering. While pronounced surface roughness is observed in films grown on LaSrAlO4 substrates, films grown on YAlO3 substrates show atomically flat surfaces, as demonstrated by atomic force microscopy (AFM) and X-ray diffraction (XRD) measurements. The crystalline structure has been confirmed to be monoclinic by symmetric and skew-symmetric XRD. Furthermore, the dependence of the growth modes and the surface morphology on the lattice mismatch is discussed.

  8. Small polaron formation in porous WO3-x nanoparticle films

    NASA Astrophysics Data System (ADS)

    Ederth, J.; Hoel, A.; Niklasson, G. A.; Granqvist, C. G.

    2004-11-01

    Porous tungsten oxide nanoparticle films were prepared by reactive gas evaporation. The structure was studied by x-ray diffraction and scanning electron microscopy, and the oxygen nonstoichiometry was inferred by x-ray photoelectron spectroscopy, elastic recoil detection analysis, and neutron scattering. Specifically, the films consisted of WO3-x with 0.25

  9. Photoinduced (WO4)3--La3+ center in PbWO4: Electron spin resonance and thermally stimulated luminescence study

    NASA Astrophysics Data System (ADS)

    Laguta, V. V.; Martini, M.; Meinardi, F.; Vedda, A.; Hofstaetter, A.; Meyer, B. K.; Nikl, M.; Mihóková, E.; Rosa, J.; Usuki, Y.

    2000-10-01

    The localization of electrons at W6+ sites perturbed by lanthanum in PbWO4 is studied by electron spin resonance (ESR) and thermally stimulated luminescence (TSL) measurements. The (WO4)3--La3+ centers are created at the W6+ sites close to La3+ in two different ways: (i) direct trapping of electrons from the conduction band under ultraviolet or x-ray irradiation at T=60 K (ii) retrapping of electrons freed from unperturbed (WO4)3- centers after irradiation at T<40 K followed by heating up to T around 60 K. Electron transfer from La3+-perturbed to unperturbed W6+ sites stimulated by red light illumination is also observed. The proposed mechanism of electron localization at one of four equivalent tungstate ions close to La3+ is based on the pseudo-Jahn-Teller effect, which gives rise to a rhombic distortion of (WO4)3- complex. At T~95-98 K the (WO4)3--La3+ centers are thermally ionized giving rise to a TSL glow peak due to the recombination of detrapped electrons with localized holes. The emission spectrum of the TSL features one band peaking at 2.8 eV. The temperature dependence of both TSL and ESR intensity is analyzed in the frame of a general order recombination model. The thermal ionization energy of (WO4)3--La3+ centers has been calculated to be approximately 0.27 eV.

  10. Synthesis of chemically bonded BiOCl@Bi2WO6 microspheres with exposed (0 2 0) Bi2WO6 facets and their enhanced photocatalytic activities under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Ma, Yongchao; Chen, Zhiwei; Qu, Dan; Shi, Jinsheng

    2016-01-01

    Bi2WO6 photocatalysts has been extensively studied for its photocatalytic activity. However, few works have been conducted on hierarchical Bi2WO6 composite photocatalysts with specifically exposed facets. In this work, we report a facile method to synthesize BiOCl@Bi2WO6 hierarchical composite microspheres. Bi2WO6 nanosheets with specifically exposed (0 2 0) facet were directly formed on the surface of BiOCl precursor microspheres via a controlled anion exchange route between BiOCl and Na2WO4. The visible-light photocatalytic activity of the BiOCl@Bi2WO6 heterojunction with exposed (0 2 0) facets (denoted as BiOCl@Bi2WO6) was investigated by degradation of Rhodamine B (RhB) and ciprofloxacin (CIP) aqueous solution under visible light irradiation. The experimental results indicated that the BiOCl@Bi2WO6 composite microsphere with intimate interfacial contacts exhibited improved efficiency for RhB photodegradation in comparison with pure BiOCl and Bi2WO6. The BiOCl@Bi2WO6 composite microsphere also shows high photocatalytic activity for degradation of CIP under visible light irradiation. The enhanced photocatalytic performance of BiOCl@Bi2WO6-020 hierarchical microspheres can be ascribed to the improved visible light harvesting ability, high charge separation and transfer. This work will make significant contributions toward the exploration of novel heterostructures with high potential in photocatalytic applications.

  11. Extended x-ray absorption fine structure spectroscopy and first-principles study of SnWO4

    NASA Astrophysics Data System (ADS)

    Kuzmin, A.; Anspoks, A.; Kalinko, A.; Timoshenko, J.; Kalendarev, R.

    2014-04-01

    The local atomic structure in α- and β-SnWO4 was studied by synchrotron radiation W L3-edge x-ray absorption spectroscopy at 10 and 300 K. Strongly distorted WO6 octahedra were found in α-SnWO4, whereas nearly regular WO4 tetrahedra were observed in β-SnWO4, confirming previous results. The structural results obtained were supported by the first-principles calculations, suggesting that the second-order Jahn-Teller effect is responsible for octahedral distortion.

  12. Enhancement of visible-light photocatalytic activity of silver and mesoporous carbon co-modified Bi2WO6

    NASA Astrophysics Data System (ADS)

    Zhao, Qian; Gong, Ming; Liu, Wangping; Mao, Yulin; Le, Shukun; Ju, Shang; Long, Fei; Liu, Xiufang; Liu, Kai; Jiang, Tingshun

    2015-03-01

    Ordered mesoporous carbon CMK-3 was prepared by hard template method using SBA-15 as template, sucrose as carbon source. Flower/sphere-like Bi2WO6 and CMK-3/Bi2WO6 photocatalysts were synthesized by hydrothermal method, and then Ag/Bi2WO6 and Ag/Bi2WO6/CMK-3 composite photocatalysts were prepared via a photoreduction process. The samples were characterized by XRD, UV-vis, TEM (HR-TEM), SEM, N2 physical adsorption and PL and their photocatalytic activities were evaluated by the photocatalytic degradation of methylene blue (MB) under visible light irradiation. The results show that both incorporating of CMK-3 and Ag loading greatly improved the photocatalytic activity of Bi2WO6, and the content of CMK-3 and silver have an impact on the photocatalytic activity of Bi2WO6. The photocatalytic activity of Ag/Bi2WO6/CMK-3 photocatalyst is superior to the activities of CMK-3/Bi2WO6 and Ag/Bi2WO6 under comparable conditions, and Ag/Bi2WO6/CMK-3 photocatalyst has high stability and is easy to be recycled. Also, the mechanism for the enhancement of the photocatalytic activity of CMK-3 and Ag co-modified Bi2WO6 was also investigated.

  13. Ag loaded WO3 nanoplates for efficient photocatalytic degradation of sulfanilamide and their bactericidal effect under visible light irradiation.

    PubMed

    Zhu, Wenyu; Liu, Jincheng; Yu, Shuyan; Zhou, Yan; Yan, Xiaoli

    2016-11-15

    Sulfonamides (SAs) are extensively used antibiotics and their residues in the water bodies propose potential threat to the public. In this study, degradation efficiency of sulfanilamide (SAM), which is the precursor of SAs, using WO3 nanoplates and their Ag heterogeneous as photocatalysts was investigated. WO3 nanoplates with uniform size were synthesized by a facile one step hydrothermal method. Different amount of Ag nanoparticles (Ag NPs) were loaded onto WO3 nanoplates using a photo-reduction method to generate WO3/Ag composites. The physio-chemical properties of synthesized nanomaterials were systematically characterized. Photodegradation of SAM by WO3 and WO3/Ag composites was conducted under visible light irradiation. The results show that WO3/Ag composites performed much better than pure WO3 where the highest removal rate was 96.2% in 5h. Ag as excellent antibacterial agent also endows certain antibacterial efficiency to WO3, and 100% removal efficiency against Escherichia Coli and Bacillus subtilis could be achieved in 2h under visible light irradiation for all three WO3/Ag composites synthesized. The improved performance in terms of SAM degradation and antibacterial activity of WO3/Ag can be attributed to the improved electron-hole pair separation rate where Ag NPs act as effective electron trapper during the photocatalytic process.

  14. Pickering w/o emulsions: drug release and topical delivery.

    PubMed

    Frelichowska, Justyna; Bolzinger, Marie-Alexandrine; Valour, Jean-Pierre; Mouaziz, Hanna; Pelletier, Jocelyne; Chevalier, Yves

    2009-02-23

    The skin absorption from Pickering emulsions as a new dosage form was investigated for the first time. Pickering emulsions are stabilized by adsorbed solid particles instead of emulsifier molecules. They are promising dosage forms that significantly differ from classical emulsions within several features. The skin permeation of a hydrophilic model penetrant (caffeine) was investigated from a w/o Pickering emulsion and compared to a w/o classical emulsion stabilized with an emulsifier. Both emulsions had the same composition and physicochemical properties in order to focus on the effect of the interfacial layer on the drug release and skin absorption processes. The highest permeation rates were obtained from the Pickering emulsion with a pseudo-steady state flux of 25 microg cm(-2)h(-1), threefold higher than from a classical emulsion (9.7 microg cm(-2)h(-1)). After 24h exposure, caffeine was mostly in the receptor fluid and in the dermis; cumulated amounts of caffeine were higher for the Pickering emulsion. Several physicochemical phenomena were investigated for clearing up the mechanisms of enhanced permeation from the Pickering emulsion. Among them, higher adhesion of Pickering emulsion droplets to skin surface was disclosed. The transport of caffeine adsorbed on silica particles was also considered relevant since skin stripping showed that aggregates of silica particles entered deeply the stratum corneum.

  15. Luminescence in trilanthanumtrichlorotungstate (La 3WO 6Cl 3)

    NASA Astrophysics Data System (ADS)

    Blasse, G.; Dirksen, G. J.; Brixner, L. H.

    1983-03-01

    The luminescence properties of La 3WO 6Cl 3 are reported and discussed. The tungstate group occurs as a trigonal prismatic WO 6-6 complex. The blue luminescence is, for the greater part, quenched at room temperature. No energy migration occurs in this lattice. The decay times are discussed in terms of a simple molecular-orbital (MO) scheme. The luminescence of the following activating ions was studied: Mo 6+, Bi 3+, Eu 3+, Sm 3+, Ce 3+, and Tb 3+. The molybdate group produces a red emission with low efficiency. The Bi 3+ ion induces a narrow band emission with small Stokes shift. This is interpreted using a Bi 3+O 2-W 6+ charge-transfer state. Except for Ce 3+, the rare earth activators show luminescence, but the total transfer efficiency from tungstate to the rare-earth ions is low. This is not due to the one-step tungstate-rare-earth transfer (which is efficient), but to the localized nature of the tungstate excitation. The Eu 3+ charge-transfer band is at very low energies.

  16. Combustion synthesis and characterization of nanocrystalline WO3.

    PubMed

    Morales, Walter; Cason, Michael; Aina, Olawunmi; de Tacconi, Norma R; Rajeshwar, Krishnan

    2008-05-21

    The energy payback time associated with the semiconductor active material is an important parameter in a photovoltaic solar cell device. Thus lowering the energy requirements for the semiconductor synthesis step or making it more energy-efficient is critical toward making the overall device economics more competitive relative to other nonpolluting energy options. In this communication, combustion synthesis is demonstrated to be a versatile and energy-efficient method for preparing inorganic oxide semiconductors such as tungsten trioxide (WO3) for photovoltaic or photocatalytic solar energy conversion. The energy efficiency of combustion synthesis accrues from the fact that high process temperatures are self-sustained by the exothermicity of the combustion process, and the only external thermal energy input needed is for dehydration of the fuel/oxidizer precursor mixture and bringing it to ignition. Importantly, we show that, in this approach, it is also possible to tune the optical characteristics of the oxide semiconductor (i.e., shift its response toward the visible range of the electromagnetic spectrum) in situ by doping the host semiconductor during the formative stage itself. As a bonus, the resultant material shows enhanced surface properties such as markedly improved organic dye uptake relative to benchmark samples obtained from commercial sources. Finally, this synthesis approach requires only very simple equipment, a feature that it shares with other "mild" inorganic semiconductor synthesis routes such as sol-gel chemistry, chemical bath deposition, and electrodeposition. The present study constitutes the first use of combustion synthesis for preparing WO3 powder comprising nanosized particles.

  17. Giant Born effective charges in cubic WO_3.

    NASA Astrophysics Data System (ADS)

    Detraux, Francois; Ghosez, Philippe; Gonze, Xavier

    1997-03-01

    WO3 crystallizes in many different phases. It is also sometimes considered in a reference idealized simple cubic structure (defect-perovskite) where the tungsten is at the center of the cell and the oxygens at the middle of each face. Using a variational formulation of the density functional perturbation theory and a planewave-pseudopotential approach, we compute the Born effective charges for this idealized cubic structure, with an optimized lattice parameter of 3.73 ÅThe values obtained are anomalously large with respect to the nominal ionic charge (+6 on W and -2 on O). For the tungsten atom, the effective charge tensor is isotropic and Z_W= +12.43. For the oxygen, we must consider two different elements corresponding respectively to a displacement of the atom parallel or perpendicular to the W-O bond: Z^*O allel= -9.07 and Z^*O ⊥= -1.66. The giant anomalous contributions to Z^*W and Z^*O allel can be explained by transfer of charge produced by dynamic changes of hybridization between the O-2p and W-5d orbitals.

  18. Hierarchically plasmonic photocatalysts of Ag/AgCl nanocrystals coupled with single-crystalline WO3 nanoplates

    NASA Astrophysics Data System (ADS)

    Chen, Deliang; Li, Tao; Chen, Qianqian; Gao, Jiabing; Fan, Bingbing; Li, Jian; Li, Xinjian; Zhang, Rui; Sun, Jing; Gao, Lian

    2012-08-01

    The hierarchical photocatalysts of Ag/AgCl@plate-WO3 have been synthesized by anchoring Ag/AgCl nanocrystals on the surfaces of single-crystalline WO3 nanoplates that were obtained via an intercalation and topochemical approach. The heterogeneous precipitation process of the PVP-Ag+-WO3 suspensions with a Cl- solution added drop-wise was developed to synthesize AgCl@WO3 composites, which were then photoreduced to form Ag/AgCl@WO3 nanostructures in situ. WO3 nanocrystals with various shapes (i.e., nanoplates, nanorods, and nanoparticles) were used as the substrates to synthesize Ag/AgCl@WO3 photocatalysts, and the effects of the WO3 contents and photoreduction times on their visible-light-driven photocatalytic performance were investigated. The techniques of TEM, SEM, XPS, EDS, XRD, N2 adsorption-desorption and UV-vis DR spectra were used to characterize the compositions, phases and microstructures of the samples. The RhB aqueous solutions were used as the model system to estimate the photocatalytic performance of the as-obtained Ag/AgCl@WO3 nanostructures under visible light (λ >= 420 nm) and sunlight. The results indicated that the hierarchical Ag/AgCl@plate-WO3 photocatalyst has a higher photodegradation rate than Ag/AgCl, AgCl, AgCl@WO3 and TiO2 (P25). The contents and morphologies of the WO3 substrates in the Ag/AgCl@plate-WO3 photocatalysts have important effects on their photocatalytic performance. The related mechanisms for the enhancement in visible-light-driven photodegradation of RhB molecules were analyzed.The hierarchical photocatalysts of Ag/AgCl@plate-WO3 have been synthesized by anchoring Ag/AgCl nanocrystals on the surfaces of single-crystalline WO3 nanoplates that were obtained via an intercalation and topochemical approach. The heterogeneous precipitation process of the PVP-Ag+-WO3 suspensions with a Cl- solution added drop-wise was developed to synthesize AgCl@WO3 composites, which were then photoreduced to form Ag/AgCl@WO3 nanostructures in

  19. The W@WO3 ohmic contact induces a high-efficiency photooxidation performance.

    PubMed

    Wan, Fangxu; Kong, Lina; Wang, Changhua; Li, Yingying; Liu, Yichun; Zhang, Xintong

    2017-01-31

    The Schottky-type metal-semiconductor (M-S) junction works well in promoting the separation of photogenerated carriers. In this paper, another type of M-S junction, Ohmic contact of W@WO3, has been developed via an acid partial oxidation strategy. By simply tuning the experimental parameters including the acid concentration and the reaction time, WO3 nanosheets are epitaxially grown on a W core; moreover, the thickness and density of the WO3 shell can be finely controlled. The photocatalytic activities of samples are tested via degradation of gaseous acetaldehyde under UV light irradiation. The results show that the W@WO3 core-shell composite with a thinner and looser WO3 shell exhibits a higher mineralization ability of acetaldehyde to carbon dioxide. An Ohmic contact between the W core and the WO3 shell is fairly confirmed by means of photo-electronic measurements. It is believed that the built-in electric field at the interface of the Ohmic contact leads to the migration of photogenerated electrons from WO3 to W, which is beneficial for separation of the electron-hole pairs and hence an enhanced photooxidation ability.

  20. Structural and gasochromic properties of WO3 films prepared by reactive sputtering deposition

    NASA Astrophysics Data System (ADS)

    Yamamoto, S.; Hakoda, T.; Miyashita, A.; Yoshikawa, M.

    2015-02-01

    The effects of deposition temperature and film thickness on the structural and gasochromic properties of tungsten trioxide (WO3) films used for the optical detection of diluted cyclohexane gas have been investigated. The WO3 films were prepared on SiO2 substrates by magnetron sputtering, with the deposition temperature ranging from 300 to 550 °C in an Ar and O2 gas mixture. The films were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), and Rutherford backscattering spectroscopy (RBS). The gasochromic properties of the WO3 films, coated with a catalytic Pt layer, were examined by exposing them to up to 5% cyclohexane in N2 gas. It was found that (001)-oriented monoclinic WO3 films, with a columnar structure, grew at deposition temperatures between 400 and 450 °C. Furthermore, (010)-oriented WO3 films were preferably formed at deposition temperatures higher than 500 °C. The gasochromic characterization of the Pt/WO3 films revealed that (001)-oriented WO3 films, with cauliflower-like surface morphology, were appropriate for the optical detection of cyclohexane gas.

  1. Superconducting phase diagram of InxWO3 synthesized by indium deintercalation

    NASA Astrophysics Data System (ADS)

    Bocarsly, Joshua D.; Hirai, Daigorou; Ali, M. N.; Cava, R. J.

    2013-07-01

    We report the superconducting phase diagram of the hexagonal tungsten bronze (HTB) InxWO3. The InxWO3 samples were prepared by indium deintercalation of the thermodynamically stable parent phase In0.33WO3. By employing this technique, a lowest indium content in the HTB phase of x \\sim 0.07 was achieved, which cannot be obtained by conventional solid-state reaction. In addition, accurately and reproducibly controlled indium content and homogeneous samples enable us to perform a systematic study of the physical properties of InxWO3. Most of the InxWO3 samples exhibit a superconducting transition and the highest transition temperature T_{\\text{c}} = 4.2\\text{K} in InxWO3 was observed at x= 0.11 . The indium content dependence of T_{\\text{c}}(x) shows remarkable similarities to other MxWO3 (M=\\text{K} and Rb) HTBs. Our results reveal the universality of physical properties in the HTB family and give a strategy to achieve higher T_{\\text{c}} in HTBs.

  2. Enhanced photocatalytic activity of cadmium-doped Bi2WO6 nanoparticles under simulated solar light

    NASA Astrophysics Data System (ADS)

    Song, Xu Chun; Li, Wen Ting; Huang, Wan Zhen; Zhou, Huan; Yin, Hao Yong; Zheng, Yi Fan

    2015-03-01

    Novel cadmium-doped Bi2WO6 nanoparticles with different Cd contents have been synthesized by a one-step route using ethylene glycol and water as solvents at 180 °C for 12 h. The as-synthesized samples were characterized in detailed by SEM, XRD, EDS, HRTEM, UV-Vis DRS, BET techniques, and so on. The results shown that with the increase of the Cd2+ addition, the crystal structure, lattice space, and absorption edge were not significantly changed and the calculated band gap value was 2.58 eV. However, the flower-like Bi2WO6 sphere was gradually destroyed. Simultaneously, the surface area and photocurrent responses of the catalysts were greatly increased. Photocatalytic activity of the Cd-doped Bi2WO6 samples was determined by monitoring the change of RhB concentration under simulated solar light. The results revealed that cadmium doping greatly improved the photocatalytic efficiency of Bi2WO6. The Bi2WO6 sample with R Cd = 0.05 displayed the highest photocatalytic activity, and the degradation rate is about two times greater than pure Bi2WO6. Moreover, the Cd-Bi2WO6 photocatalyst remained stable even after five consecutive cycles. A possible mechanism of photocatalytic activity enhancement on basis of the experimental results was proposed.

  3. Dual preparation of hydrophobic and hydrophilic BaWO{sub 4}:Eu phosphors

    SciTech Connect

    Cho, Young-Sik; Huh, Young-Duk

    2016-06-15

    Highlights: • Red-emitting BaWO{sub 4}:Eu phosphors were prepared in hexane-water bilayer system. • The hydrophobic nanometer-sized BaWO{sub 4}:Eu phosphors were obtained in hexane. • The hydrophilic micrometer-sized BaWO{sub 4}:Eu dendrites were obtained in water. - Abstract: BaWO{sub 4}:Eu phosphors were prepared by performing a solvothermal reaction in a water–hexane bilayer system. A barium oleate (and europium oleate) complex was obtained in hexane via a phase transfer reaction involving Ba{sup 2+} (and Eu{sup 3+}) ions in an aqueous solution of sodium oleate. The outer surfaces of the nanometer-sized BaWO{sub 4}:Eu phosphors were capped by the long alkyl chain of oleate; therefore, the hydrophobic nanometer-sized BaWO{sub 4}:Eu phosphors preferentially dissolved in the hexane layer. The micrometer-sized BaWO{sub 4}:Eu phosphors were obtained in the water layer. The BaWO{sub 4}:Eu phosphors prepared in hexane and water yielded sharp strong absorption and emission peaks at 464 and 615 nm, respectively, due to the {sup 7}F{sub 0} → {sup 5}D{sub 2} and the {sup 5}D{sub 0} →{sup 7} F{sub 2} transitions of the Eu{sup 3+} ions. The BaWO{sub 4}:Eu phosphors are good candidate red-emitting phosphors for use in InGaN blue-emitting diodes, which have an emission wavelength of 465 nm.

  4. Electrodeposition of WO3 nanoparticles into surface mounted metal-organic framework HKUST-1 thin films.

    PubMed

    Yoo, Hyeonseok; Welle, Alexander; Guo, Wei; Choi, Jinsub; Redel, Engelbert

    2017-03-17

    We describe a novel procedure to fabricate WO3@surface-mounted metal-organic framework (SURMOF) hybrid materials by electrodeposition of WO3 nanoparticles into HKUST-1, also termed Cu3(BTC)2 SURMOFs. These materials have been characterized using x-ray diffraction, time-of-flight secondary ion mass spectrometry, scanning electron microscopy, x-ray photoelectron spectroscopy as well as linear sweep voltammetry. The WO3 semiconductor/SURMOF heterostructures were further tested as hybrid electrodes in their performance for hydrogen evolution reaction from water.

  5. High photocurrent conversion efficiency in self-organized porous WO{sub 3}

    SciTech Connect

    Berger, S.; Tsuchiya, H.; Ghicov, A.; Schmuki, P.

    2006-05-15

    Self-organized porous structures of WO{sub 3} were grown on tungsten by an anodic oxidation, and their photoelectrochemical properties were characterized. The porous WO{sub 3} layers show a regular morphology with average pore sizes of approximately 70 nm and a pore wall thickness of approximately 10 nm. As formed layers show an amorphous structure but the layers can be altered to a crystalline monoclinic structure by thermal annealing. The annealed porous WO{sub 3} layers show a very high specific photocurrent conversion efficiency.

  6. Fabrication and photocatalysis of mesoporous ZnWO{sub 4} with PAMAM as a template

    SciTech Connect

    Lin Shen Chen Jiebo; Weng Xiulan; Yang Liuyi; Chen Xinqin

    2009-05-06

    Mesoporous ZnWO{sub 4} was prepared with the template of PAMAM. The as-formed samples were characterized by X-ray diffraction (XRD), nitrogen absorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-vis diffuse reflectance spectroscopy (DRS). It is found that the size of pore is in the range of 5-22 nm and that the porosity of ZnWO{sub 4} is composed of aggregated ZnWO{sub 4} nanoparticles. The photocatalytic activities towards degradation of rhodamine B (RhB) and malachite green (MG) under UV light has been investigated. The formation mechanism of mesoporous structures is proposed.

  7. Metal-insulator transition in NaxWO3: Photoemission spectromicroscopy study

    NASA Astrophysics Data System (ADS)

    Paul, Sanhita; Ghosh, Anirudha; Raj, Satyabrata

    2014-04-01

    We have investigated the validity of percolation model, which is quite often invoked to explain the metal-insulator transition in sodium tungsten bronzes, NaxWO3 by photoelectron spectromicroscopy. The spatially resolved direct spectromicroscopic probing on both the insulating and metallic phases of high quality single crystals of NaxWO3 reveals the absence of any microscopic inhomogeneities embedded in the system within the experimental limit. Neither any metallic domains in the insulating host nor any insulating domains in the metallic host have been found to support the validity of percolation model to explain the metal-insulator transition in NaxWO3.

  8. Electrodeposition of WO3 nanoparticles into surface mounted metal–organic framework HKUST-1 thin films

    NASA Astrophysics Data System (ADS)

    Yoo, Hyeonseok; Welle, Alexander; Guo, Wei; Choi, Jinsub; Redel, Engelbert

    2017-03-01

    We describe a novel procedure to fabricate WO3@surface-mounted metal–organic framework (SURMOF) hybrid materials by electrodeposition of WO3 nanoparticles into HKUST-1, also termed Cu3(BTC)2 SURMOFs. These materials have been characterized using x-ray diffraction, time-of-flight secondary ion mass spectrometry, scanning electron microscopy, x-ray photoelectron spectroscopy as well as linear sweep voltammetry. The WO3 semiconductor/SURMOF heterostructures were further tested as hybrid electrodes in their performance for hydrogen evolution reaction from water.

  9. Scheelite (CaWO4)-type microphosphors: Facile synthesis, structural characterization and photoluminescence properties

    NASA Astrophysics Data System (ADS)

    Han, Yuanyuan; Wang, Dan; Liang, Danyang; Wang, Shiqi; Lu, Guoxin; Wang, Xiaoyu; Pei, Nana

    2016-11-01

    Scheelite (CaWO4)-type microphosphors were synthesized by the precipitation method assisted with cetyltrimethyl ammonium bromide (CTAB). All compounds crystallized in the tetragonal structure with space group I41/a (No. 88). FE-SEM micrographs illustrate the spherical-like morphologies and rough surface. PL spectra indicate the broad emission peak maximum at 613 nm under UV excitation. Luminescence decay curves monitored by 5D 6 -7F 0 transition (λex = 394 nm) of Eu3+ in doped CaWO4 are presented, the curves exhibit a single-exponential feature and the lifetime for doped CaWO4 is 0.61 ms.

  10. Enhanced field-emission from SnO2:WO(2.72) nanowire heterostructures.

    PubMed

    Shinde, Deodatta R; Chavan, Padmakar G; Sen, Shashwati; Joag, Dilip S; More, Mahendra A; Gadkari, S C; Gupta, S K

    2011-12-01

    The field-emission properties of SnO(2):WO(2.72) hierarchical nanowire heterostructure have been investigated. Nanoheterostructure consisting of SnO(2) nanowires as stem and WO(2.72) nanothorns as branches are synthesized in two steps by physical vapor deposition technique. Their field emission properties were recorded. A low turn-on field of ~0.82 V/μm (to draw an emission current density ~10 μA/cm(2)) is achieved along with stable emission for 4 h duration. The emission characteristic shows the SnO(2):WO(2.72) nanoheterostructures are extremely suitable for field-emission applications.

  11. Synthesis of WC powder through microwave heating of WO3-C mixture

    NASA Astrophysics Data System (ADS)

    Behnami, Amir Karimzadeh; Hoseinpur, Arman; Sakaki, Masoud; Bafghi, Mohammad Sh.; Yanagisawa, Kazumichi

    2017-02-01

    A simple, easy, and low-cost process for the fabrication of tungsten carbide (WC) powder through microwave heating of WO3-C mixtures was developed. Thermodynamic calculations and experimental investigations were carried out for WO3-C and W-C systems, and a formation mechanism was proposed. In the results, for the synthesis of WC, the use of over stoichiometric amount of C together with a specially assembled experimental setup (which effectively retains heat in the system) is necessary. The WC powder is successfully obtained by heating WO3:5C mixture for 900 s in a domestic microwave oven.

  12. CTAB-assisted ultrasonic synthesis, characterization and photocatalytic properties of WO{sub 3}

    SciTech Connect

    Sánchez-Martínez, D. Gomez-Solis, C.; Torres-Martinez, Leticia M.

    2015-01-15

    Highlights: • WO{sub 3} 2D nanostructures were synthesized by ultrasound method assisted with CTAB. • WO{sub 3} morphology was mainly of rectangular nanoplates with a thickness of ∼50 nm. • The highest surface area value of WO{sub 3} was obtained to lowest concentration of CTAB. • WO{sub 3} activity was attributed to morphology, surface area and the addition of CTAB. • WO{sub 3} nanoplates were able to causing almost complete mineralization of rhB and IC. - Abstract: WO{sub 3} 2D nanostructures have been prepared by ultrasound synthesis method assisted with CTAB using different molar ratios. The formation of monoclinic crystal structure of WO{sub 3} was confirmed by X-ray powder diffraction (XRD). The characterization of the WO{sub 3} samples was complemented by analysis of scanning electron microscopy (SEM), which revealed morphology mainly of rectangular nanoplates with a thickness of around 50 nm and length of 100–500 nm. Infrared spectroscopy (FT-IR) was used to confirm the elimination of the CTAB in the synthesized samples. The specific surface area was determinate by the BET method and by means of diffuse reflectance spectroscopy (DRS) it was determinate the band-gap energy (E{sub g}) of the WO{sub 3} samples. The photocatalytic activity of the WO{sub 3} oxide was evaluated in the degradation reactions of rhodamine B (rhB) and indigo carmine (IC) under Xenon lamp irradiation. The highest photocatalytic activity was observed in the samples containing low concentration of CTAB with morphology of rectangular nanoplates and with higher surface area value than commercial WO{sub 3}. Photodegradation of rhB and IC were followed by means of UV–vis absorption spectra. The mineralization degree of organic dyes by WO{sub 3} photocatalyst was determined by total organic carbon analysis (TOC) reaching percentages of mineralization of 92% for rhB and 50% for IC after 96 h of lamp irradiation.

  13. Using crystallographic shear to reduce lattice thermal conductivity: high temperature thermoelectric characterization of the spark plasma sintered Magnéli phases WO2.90 and WO2.722.

    PubMed

    Kieslich, Gregor; Veremchuk, Igor; Antonyshyn, Iryna; Zeier, Wolfgang G; Birkel, Christina S; Weldert, Kai; Heinrich, Christophe P; Visnow, Eduard; Panthöfer, Martin; Burkhardt, Ulrich; Grin, Yuri; Tremel, Wolfgang

    2013-10-07

    Engineering of nanoscale structures is a requisite for controlling the electrical and thermal transport in solids, in particular for thermoelectric applications that require a conflicting combination of low thermal conductivity and low electrical resistivity. We report the thermoelectric properties of spark plasma sintered Magnéli phases WO2.90 and WO2.722. The crystallographic shear planes, which are a typical feature of the crystal structures of Magnéli-type metal oxides, lead to a remarkably low thermal conductivity for WO2.90. The figures of merit (ZT = 0.13 at 1100 K for WO2.90 and 0.07 at 1100 K for WO2.722) are relatively high for tungsten-oxygen compounds and metal oxides in general. The electrical resistivity of WO2.722 shows a metallic behaviour with temperature, while WO2.90 has the characteristics of a heavily doped semiconductor. The low thermopower of 80 μV K(-1) at 1100 K for WO2.90 is attributed to its high charge carrier concentration. The enhanced thermoelectric performance for WO2.90 compared to WO2.722 originates from its much lower thermal conductivity, due to the presence of crystallographic shear and dislocations in the crystal structure. Our study is a proof of principle for the development of efficient and low-cost thermoelectric materials based on the use of intrinsically nanostructured materials rather than artificially structured layered systems to reduce lattice thermal conductivity.

  14. Growth and crystallographic characterization of molecular beam epitaxial WO3 and MoO3/WO3 thin films on sapphire substrates

    NASA Astrophysics Data System (ADS)

    Yano, Mitsuaki; Koike, Kazuto; Matsuo, Masayuki; Murayama, Takayuki; Harada, Yoshiyuki; Inaba, Katsuhiko

    2016-09-01

    Molecular beam epitaxy of tungsten trioxide (WO3) on (01 1 bar 2)-oriented (r-plane) sapphire substrates and molybdenum trioxide (MoO3) on the WO3 was studied by focusing on their crystallogrhaphic properties. Although polycrystalline monoclinic (γ-phase) WO3 films were grown at 500 °C and they became single-crystalline (0 0 1)-oriented γ-phase at 700 °C, the latter films were oxygen-deficient from stoichiometry and contained dense and deep thermal etchpits. By using a two-step growth method where only the initial 15 nm was grown at 700 °C and the rest part was grown at 500 °C, (0 0 1)-oriented γ-phase single-crystalline WO3 films with stoichiometric composition and smooth surface were obtained. On top of the 15-nm-thick WO3 initiation layer, (1 1 0)-oriented orthorhombic (α-phase) MoO3 films with smooth surface were obtained.

  15. Photoreduction of non-noble metal Bi on the surface of Bi2WO6 for enhanced visible light photocatalysis

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaojing; Yu, Shan; Liu, Yang; Zhang, Qian; Zhou, Ying

    2017-02-01

    In this report, Bi2WO6-Bi composite was prepared through an in situ photoreduction method and was characterized systematically by X-Ray diffraction, transmission electron microscopy, X-Ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy. The as-prepared Bi2WO6-Bi maintains the same crystal structure with the pristine Bi2WO6 regardless of some surface defects. Nevertheless, these surface defects result in the change of surface oxygen adsorption mode from hydroxyl to molecular oxygen on Bi2WO6. Photocatalytic activity over Bi2WO6-Bi is 2.4 times higher than that of Bi2WO6 towards the degradation of organic dye Rhodamine B (RhB) under visible light irradiation (λ > 420 nm). A deep study shows that cleavage of benzene ring is the main pathway for RhB degradation over Bi2WO6, but both the benzene cleavage and de-ethylation pathway coexist for RhB decomposition in the presence of Bi2WO6-Bi as the photocatalyst. Photoelectrochemical study including transient photocurrent tests and electrochemical impedance spectroscopy measurements shows that Bi2WO6-Bi could facilitate the charge transfer process compared to Bi2WO6. These data above has indicated a new insight into the promotion mechanism based on Bi related heterostructures.

  16. Preparation of WO3/g-C3N4 composites and their application in oxidative desulfurization

    NASA Astrophysics Data System (ADS)

    Zhao, Rongxiang; Li, Xiuping; Su, Jianxun; Gao, Xiaohan

    2017-01-01

    WO3/graphitic carbon nitride (g-C3N4) composites were successfully synthesized through direct calcining of a mixture of WO3 and g-C3N4 at 400 °C for 2 h. The WO3 was prepared by calcination of phosphotungstic acid at 550 °C for 4 h, and the g-C3N4 was obtained by calcination of melamine at 520 °C for 4 h. The WO3/g-C3N4 composites were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), and Brunner-Emmett-Teller analysis (BET). The WO3/g-C3N4 composites exhibited stronger XRD peaks of WO3 and g-C3N4 than the WO3 and pure g-C3N4. In addition, two WO3 peaks at 25.7° and 26.6° emerged for the 36% -WO3/g-C3N4 composite. This finding indicated that WO3 was highly dispersed on the surface of the g-C3N4 nanosheets and interacted with the nanosheets, which resulted in the appearance of (012) and (022) planes of WO3. The WO3/g-C3N4 composite also exhibited a larger specific surface area and higher degree of crystallization than WO3 or pure g-C3N4, which resulted in high catalytic activity of the catalyst. Desulfurization experiments demonstrated that the desulfurization rate of dibenzothiophene (DBT) in model oil reached 91.2% under optimal conditions. Moreover, the activity of the catalyst was not significantly decreased after five recycles.

  17. Piezo-optic coefficients of CaWO4 crystals

    NASA Astrophysics Data System (ADS)

    Mytsyk, B. G.; Kost', Ya. P.; Demyanyshyn, N. M.; Andrushchak, A. S.; Solskii, I. M.

    2015-01-01

    All components of the piezo-optic coefficient matrix of calcium tungstate crystals, belonging to the 4/ m symmetry class, are determined. The reliability of the piezo-optic effect measurements in CaWO4 crystals is achieved by determining each piezo-optic coefficient from several experimental geometries and is also based on the correlation of the absolute piezo-electric coefficients and the path-difference coefficients. The rotation-shear diagonal coefficients π44 and π66 and three principal piezo-optic coefficients π11, π13, and π31 are refined by the polarization-optical method. It is confirmed that both the interferometric and polarization-optical methods should be used to study the piezo-optic effect with high accuracy. The results show that calcium tungstate is a promising material for acousto-optical and photoelastic modulation.

  18. Efficient photoelectrochemical water splitting by anodically grown WO3 electrodes.

    PubMed

    Cristino, Vito; Caramori, Stefano; Argazzi, Roberto; Meda, Laura; Marra, Gian Luigi; Bignozzi, Carlo Alberto

    2011-06-07

    The potentiostatic anodization of metallic tungsten has been investigated in different solvent/electrolyte compositions with the aim of improving the water oxidation ability of the tungsten oxide layer. In the NMF/H(2)O/NH(4)F solvent mixture, the anodization leads to highly efficient WO(3) photoanodes, which, combining spectral sensitivity, an electrochemically active surface, and improved charge-transfer kinetics, outperform, under simulated solar illumination, most of the reported nanocrystalline substrates produced by anodization in aqueous electrolytes and by sol-gel methods. The use of such electrodes results in high water electrolysis yields of between 70 and 90% in 1 M H(2)SO(4) under a potential bias of 1 V versus SCE and close to 100% in the presence of methanol.

  19. Sonochromic effect in WO{sup 3} colloidal suspensions

    SciTech Connect

    Kamat, P.V.; Vinodgopal, K.

    1996-11-13

    In recent years there has been a burst of activities in investigating sonolytic reactions. The usefulness of this technique in synthesizing colloidal semiconductors and metals and dissolution of MnO{sup 2} colloids has also been demonstrated. We have now employed semiconductor colloids to investigate the radical reactions in sonolytic processes. In this study we present our preliminary results from the reaction of WO{sup 3} colloids with sonolytically generated H atoms. Sodium tungstate, oxalic acid, and Acid Orange 7 were obtained from Aldrich. Acid Orange 7 was purified by column chromatography. All other chemicals were analytical reagents of highest available purity. The analysis experiments were carried out with a 640 kHz sonolysis setup of Ultrasonic Energy Systems (Panama City, FL). 24 refs., 4 figs.

  20. Anomalously large Born effective charges in cubic WO3

    NASA Astrophysics Data System (ADS)

    Detraux, F.; Ghosez, Ph.; Gonze, X.

    1997-07-01

    Within density-functional theory, we compute the Born effective charges of tungsten trioxyde in its reference cubic phase (defect-perovskite structure). For the tungsten atom, the effective charge tensor is isotropic, with Z*W=+12.51. For the oxygen atoms, the two independent components of the tensor, corresponding, respectively, to a displacement of the atom parallel or perpendicular to the W-O bond, have the values Z*O||=-9.13 and Z*O⊥=-1.68. Z*W and Z*O|| are anomalously large with respect to the nominal ionic charges (+6 on W and -2 on O), but compatible with the Born effective charges found in related ABO3-perovskite compounds.

  1. Fabrication of luminescent SrWO{sub 4} thin films by a novel electrochemical method

    SciTech Connect

    Chen Lianping Gao Yuanhong

    2007-10-02

    Highly crystallized SrWO{sub 4} thin films with single scheelite structure were prepared within 60 min by a cell electrochemical method. X-ray diffraction analysis shows that SrWO{sub 4} thin films have a tetragonal structure. Scanning electron microscopy examinations reveal that SrWO{sub 4} grains grow well in tetragonal tapers and grains like flowers or bunches, which can usually form by using the electrolysis electrochemical method, have disappeared under cell electrochemical conditions. X-ray photoelectron spectra and energy dispersive X-ray microanalysis examinations demonstrate that the composition of the film is consistent with its stoichiometry. These SrWO{sub 4} films show a single blue emission peak (located at 460 nm) using an excitation wave of 230 nm. The speed of cell electrochemical method can be controlled by changing temperature. The optimum treatment temperature is about 50-60 deg. C.

  2. Bacteriophage WO Can Mediate Horizontal Gene Transfer in Endosymbiotic Wolbachia Genomes

    PubMed Central

    Wang, Guan H.; Sun, Bao F.; Xiong, Tuan L.; Wang, Yan K.; Murfin, Kristen E.; Xiao, Jin H.; Huang, Da W.

    2016-01-01

    Phage-mediated horizontal gene transfer (HGT) is common in free-living bacteria, and many transferred genes can play a significant role in their new bacterial hosts. However, there are few reports concerning phage-mediated HGT in endosymbionts (obligate intracellular bacteria within animal or plant hosts), such as Wolbachia. The Wolbachia-infecting temperate phage WO can actively shift among Wolbachia genomes and has the potential to mediate HGT between Wolbachia strains. In the present study, we extend previous findings by validating that the phage WO can mediate transfer of non-phage genes. To do so, we utilized bioinformatic, phylogenetic, and molecular analyses based on all sequenced Wolbachia and phage WO genomes. Our results show that the phage WO can mediate HGT between Wolbachia strains, regardless of whether the transferred genes originate from Wolbachia or other unrelated bacteria. PMID:27965627

  3. Hydrothermal Fabrication of WO3 Hierarchical Architectures: Structure, Growth and Response

    PubMed Central

    Wu, Chuan-Sheng

    2015-01-01

    Recently hierarchical architectures, consisting of two-dimensional (2D) nanostructures, are of great interest for potential applications in energy and environmental. Here, novel rose-like WO3 hierarchical architectures were successfully synthesized via a facile hydrothermal method. The as-prepared WO3 hierarchical architectures were in fact assembled by numerous nanosheets with an average thickness of ~30 nm. We found that the oxalic acid played a significant role in governing morphologies of WO3 during hydrothermal process. Based on comparative studies, a possible formation mechanism was also proposed in detail. Furthermore, gas-sensing measurement showed that the well-defined 3D WO3 hierarchical architectures exhibited the excellent gas sensing properties towards CO. PMID:28347062

  4. Enhanced electrochemical performance of monoclinic WO3 thin film with redox additive aqueous electrolyte.

    PubMed

    Shinde, Pragati A; Lokhande, Vaibhav C; Chodankar, Nilesh R; Ji, Taeksoo; Kim, Jin Hyeok; Lokhande, Chandrakant D

    2016-12-01

    To achieve the highest electrochemical performance for supercapacitor, it is very essential to find out a suitable pair of an active electrode material and an electrolyte. In the present work, a simple approach is employed to enhance the supercapacitor performance of WO3 thin film. The WO3 thin film is prepared by a simple and cost effective chemical bath deposition method and its electrochemical performance is tested in conventional (H2SO4) and redox additive [H2SO4+hydroquinone (HQ)] electrolytes. Two-fold increment in electrochemical performance for WO3 thin film is observed in redox additive aqueous electrolyte compared to conventional electrolyte. WO3 thin film showed maximum specific capacitance of 725Fg(-1), energy density of 25.18Whkg(-1) at current density of 7mAcm(-2) with better cycling stability in redox electrolyte. This strategy provides the versatile way for designing the high performance energy storage devices.

  5. Facile and controlled synthesis of aligned WO3 nanorods and nanosheets as an efficient photocatalyst material

    NASA Astrophysics Data System (ADS)

    Ahmed, Bilal; Kumar, Sumeet; Ojha, Animesh K.; Donfack, P.; Materny, A.

    2017-03-01

    In this work, we have performed a facile and controlled synthesis of WO3 nanorods and sheets in different crystal phases (triclinic, orthorhombic and monoclinic) of WO3 using the sol-gel method. The detailed structures of the synthesized materials were examined by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy measurements. The shapes and crystal phases of the WO3 nanostructures were found to be highly dependent on the calcination temperature. The variation in crystalline phases and shapes is modified the electronic structure of the samples, which causes a variation in the value of optical band gap. The value of the Raman line intensity ratio I264/I320 has been successfully used to identify the structural transition from the triclinic to the orthorhombic phase of WO3. The PL spectra of the synthesized products excited at wavelengths 380, 400, and 420 nm exhibit intense emission peaks that cover the complete visible range (blue-green-red). The emission peaks at 460 and 486 nm were caused by the near band-edge and band to band transition, respectively. The peaks in spectral range 500-600 nm might be originated from the presence of oxygen vacancies lying within the energy band gap. The synthesized WO3 nanostructures showed improved photocatalytic activity for the photodegradation of MB dye. The enhanced photocatalytic activity of WO3 nanosheets compared to WO3 nanorods for photodegradation of methylene blue (MB) dye could be due to the shape of the nanostructured WO3. The sheet type of structure provides more active surface for the interaction of dye molecules compared to the rods, which results in a more efficient degradation of the dye molecules.

  6. [Doctor's degree thesis of Tomasz Adolf Wołkowiński "Carditidis rheumaticae historia"].

    PubMed

    Stembrowicz, W

    2001-01-01

    In 1817 on the University of Vilnius Faculty of Medicine, T. A. Wołkowiński, a student of the eminent clinician Józef Frank, defended his doctor's degree thesis about a direct relation between rheumatic disease and cardiomegaly. It was probably the first paper in Poland describing with details the rheumatic heart disease. Unfortunately we don't know much about T. A. Wołkowiński's life.

  7. Light-Driven Au-WO3@C Janus Micromotors for Rapid Photodegradation of Dye Pollutants.

    PubMed

    Zhang, Qilu; Dong, Renfeng; Wu, Yefei; Gao, Wei; He, Zihan; Ren, Biye

    2017-02-08

    A novel light-driven Au-WO3@C Janus micromotor based on colloidal carbon WO3 nanoparticle composite spheres (WO3@C) prepared by one-step hydrothermal treatment is described. The Janus micromotors can move in aqueous media at a speed of 16 μm/s under 40 mW/cm(2) UV light due to diffusiophoretic effects. The propulsion of such Au-WO3@C Janus micromotors (diameter ∼ 1.0 μm) can be generated by UV light in pure water without any external chemical fuels and readily modulated by light intensity. After depositing a paramagnetic Ni layer between the Au layer and WO3, the motion direction of the micromotor can be precisely controlled by an external magnetic field. Such magnetic micromotors not only facilitate recycling of motors but also promise more possibility of practical applications in the future. Moreover, the Au-WO3@C Janus micromotors show high sensitivity toward extremely low concentrations of sodium-2,6-dichloroindophenol (DCIP) and Rhodamine B (RhB). The moving speed of motors can be significantly accelerated to 26 and 29 μm/s in 5 × 10(-4) wt % DCIP and 5 × 10(-7) wt % RhB aqueous solutions, respectively, due to the enhanced diffusiophoretic effect, which results from the rapid photocatalytic degradation of DCIP and RhB by WO3. This photocatalytic acceleration of the Au-WO3@C Janus micromotors confirms the self-diffusiophoretic mechanism and opens an opportunity to tune the motility of the motors. This work also offers the light-driven micromotors a considerable potential for detection and rapid photodegradation of dye pollutants in water.

  8. Synthesis and evaluation of α-Ag2WO4 as novel antifungal agent

    NASA Astrophysics Data System (ADS)

    Foggi, Camila C.; Fabbro, Maria T.; Santos, Luís P. S.; de Santana, Yuri V. B.; Vergani, Carlos E.; Machado, Ana L.; Cordoncillo, Eloisa; Andrés, Juan; Longo, Elson

    2017-04-01

    Because of the need for new antifungal materials with greater potency, microcrystals of α-Ag2WO4, a complex metal oxide, have been synthetized by a simple co-precipitation method, and their antifungal activity against Candida albicans has been investigated. A theoretical model based on clusters that are building blocks of α-Ag2WO4 has been proposed to explain the experimental results.

  9. Controllable synthesis of hierarchical nanostructures of CaWO{sub 4} and SrWO{sub 4} via a facile low-temperature route

    SciTech Connect

    Chen, Z.; Gong, Q.; Zhu, J.; Yuan, Y.P.; Qian, L.W.; Qian, X.F.

    2009-01-08

    CaWO{sub 4} and SrWO{sub 4} nanostructures have been synthesized via a simple microemulsion-mediated route. With careful control of the fundamental experimental parameters including the concentration of reactants, the reaction time and the temperature, the products with different morphologies of dumbbell, coral, rod and dendrite have been obtained, respectively. The possible formation mechanism of these unique morphologies has been proposed based on surfactant self-assembly under different experimental conditions. The as-synthesized CaWO{sub 4} samples with various morphologies exhibit different photoluminescence properties. X-ray powder diffraction, transmission electron microscopy, field-emission scanning electron microscopy, and luminescence spectroscopy were used to characterize these products.

  10. Investigation of x-ray photoelectron spectroscopic (XPS), cyclic voltammetric analyses of WO3 films and their electrochromic response in FTO/WO3/electrolyte/FTO cells

    NASA Astrophysics Data System (ADS)

    Sivakumar, R.; Gopalakrishnan, R.; Jayachandran, M.; Sanjeeviraja, C.

    2006-06-01

    Electrochromic thin films of tungsten oxide (WO3) were prepared on transparent conducting oxide substrates, i.e., fluorine doped tin oxide coated (FTO or SnO2:F) glass and microscopic glass substrates by the electron beam evaporation technique using pure WO3 (99.99%) pellets at various substrate temperatures (i.e., Tsub = room temperature (RT, 30 °C), 100 °C and 200 °C). The films were prepared under vacuum of the order of 1 × 10-5 mbar. The room temperature prepared films were further post-heat-treated (Tanne) at 200 and 300 °C for about 1 h in the vacuum environment. The prepared films are in monoclinic phase. The chemical composition has been characterized by using the XPS technique. The W 4f and O 1s core levels of WO3 films have been studied on the samples. The obtained core level binding energies revealed the WO3 films contained six-valent tungsten (W6+). The electrochemical nature of the films was studied by a three-electrode electrochemical cell in the configuration of FTO/WO3/H2SO4/Pt, SCE, using the cyclic voltammetry (CV) technique. Electrochromic devices (ECDs) of the general type FTO/WO3/electrolyte/FTO were studied. The films produced at higher substrate temperature show smaller modulation of the visible spectrum, compared with the films produced at lower temperatures. The significant chemical bonding nature associated with the coloring/bleaching process which follows the H+ ion incorporation in the film is studied by FTIR analysis. The W-O-W framework peak was observed at 563 cm-1 and confirms the stability of the films in the electrochemical analysis. The results obtained from cyclic voltammetry technique and ECD cell characterization are used to emphasize the suitability for some applications of the solar control systems.

  11. WO3/TiO2 nanotube photoanodes for solar water splitting with simultaneous wastewater treatment.

    SciTech Connect

    Reyes, Karla Rosa; Robinson, David B.

    2013-05-01

    Nanostructured WO3/TiO2 nanotubes with properties that enhance solar photoconversion reactions were developed, characterized and tested. The TiO2 nanotubes were prepared by anodization of Ti foil, and WO3 was electrodeposited on top of the nanotubes. SEM images show that these materials have the same ordered structure as TiO2 nanotubes, with an external nanostructured WO3 layer. Diffuse reflectance spectra showed an increase in the visible absorption relative to bare TiO2 nanotubes, and in the UV absorption relative to bare WO3 films. Incident simulated solar photon-to-current efficiency increased from 30% (for bare WO3) to 50% (for WO3/TiO2 composites). With the addition of diverse organic pollutants, the photocurrent densities exhibited more than a 5-fold increase. Chemical oxygen demand measurements showed the simultaneous photodegradation of organic pollutants. The results of this work indicate that the unique structure and composition of these composite materials enhance the charge carrier transport and optical properties compared with the parent materials.

  12. Phonon properties of nanosized MnWO{sub 4} with different size and morphology

    SciTech Connect

    Maczka, MirosLaw; Ptak, Maciej; Kurnatowska, Michalina; Kepinski, Leszek; Tomaszewski, PaweL; Hanuza, Jerzy

    2011-09-15

    Highly hierarchical barlike and flowerlike MnWO{sub 4} microcrystals have been synthesized for the first time by a hydrothermal method, where ethanolamine (EA) and cetyltrimethylamonnium bromide (CTAB) play important roles in directing growth and self-assembly of these structures. The possible formation process has been proposed. In addition, platelike nanosized MnWO{sub 4} was also synthesized by annealing of a precursor obtained by coprecipitation method. The obtained samples were characterized by XRD, SEM, TEM, Raman and IR methods. Raman spectra showed relatively weak dependence on particle size and morphology of the particles. In contrast to this behavior, IR-active bands showed pronounced shifts and changes in relative intensities on particle size and the morphology. Origin of this behavior is discussed. - Graphical Abstract: SEM images of MnWO{sub 4} particles prepared by hydrothermal process at 150 deg. C (left panel) and 200 deg. C (right panel). Highlights: > Hydrothermal synthesis with ethanolamine enables growth of hierarchical nanosized MnWO{sub 4} particles. > Annealing of a precursor obtained by coprecipitation method enables growth of platelike MnWO{sub 4} nanoparticles. > Raman and IR spectra of MnWO{sub 4} nanoparticles depend on both size and morphology of the nanoparticles. > We discuss origin of this behavior.

  13. Modulating memristive performance of hexagonal WO3 nanowire by water-oxidized hydrogen ion implantation

    PubMed Central

    Zhou, Yong; Peng, Yuehua; Yin, Yanling; Zhou, Fang; Liu, Chang; Ling, Jing; Lei, Le; Zhou, Weichang; Tang, Dongsheng

    2016-01-01

    In a two-terminal Au/hexagonal WO3 nanowire/Au device, ions drifting or carriers self-trapping under external electrical field will modulate the Schottky barriers between the nanowire and electrodes, and then result in memristive effect. When there are water molecules adsorbed on the surface of WO3 nanowire, hydrogen ions will generate near the positively-charged electrode and transport in the condensed water film, which will enhance the memristive performance characterized by analogic resistive switching remarkably. When the bias voltage is swept repeatedly under high relative humidity level, hydrogen ions will accumulate on the surface and then implant into the lattice of the WO3 nanowire, which leads to a transition from semiconducting WO3 nanowire to metallic HxWO3 nanowire. This insulator-metal transition can be realized more easily after enough electron-hole pairs being excited by laser illumination. The concentration of hydrogen ions in HxWO3 nanowire will decrease when the device is exposed to oxygen atmosphere or the bias voltage is swept in atmosphere with low relative humidity. By modulating the concentration of hydrogen ions, conductive hydrogen tungsten bronze filament might form or rupture near electrodes when the polarity of applied voltage changes, which will endow the device with memristive performance characterized by digital resistive switching. PMID:27600368

  14. Modulating memristive performance of hexagonal WO3 nanowire by water-oxidized hydrogen ion implantation.

    PubMed

    Zhou, Yong; Peng, Yuehua; Yin, Yanling; Zhou, Fang; Liu, Chang; Ling, Jing; Lei, Le; Zhou, Weichang; Tang, Dongsheng

    2016-09-07

    In a two-terminal Au/hexagonal WO3 nanowire/Au device, ions drifting or carriers self-trapping under external electrical field will modulate the Schottky barriers between the nanowire and electrodes, and then result in memristive effect. When there are water molecules adsorbed on the surface of WO3 nanowire, hydrogen ions will generate near the positively-charged electrode and transport in the condensed water film, which will enhance the memristive performance characterized by analogic resistive switching remarkably. When the bias voltage is swept repeatedly under high relative humidity level, hydrogen ions will accumulate on the surface and then implant into the lattice of the WO3 nanowire, which leads to a transition from semiconducting WO3 nanowire to metallic HxWO3 nanowire. This insulator-metal transition can be realized more easily after enough electron-hole pairs being excited by laser illumination. The concentration of hydrogen ions in HxWO3 nanowire will decrease when the device is exposed to oxygen atmosphere or the bias voltage is swept in atmosphere with low relative humidity. By modulating the concentration of hydrogen ions, conductive hydrogen tungsten bronze filament might form or rupture near electrodes when the polarity of applied voltage changes, which will endow the device with memristive performance characterized by digital resistive switching.

  15. Modulating memristive performance of hexagonal WO3 nanowire by water-oxidized hydrogen ion implantation

    NASA Astrophysics Data System (ADS)

    Zhou, Yong; Peng, Yuehua; Yin, Yanling; Zhou, Fang; Liu, Chang; Ling, Jing; Lei, Le; Zhou, Weichang; Tang, Dongsheng

    2016-09-01

    In a two-terminal Au/hexagonal WO3 nanowire/Au device, ions drifting or carriers self-trapping under external electrical field will modulate the Schottky barriers between the nanowire and electrodes, and then result in memristive effect. When there are water molecules adsorbed on the surface of WO3 nanowire, hydrogen ions will generate near the positively-charged electrode and transport in the condensed water film, which will enhance the memristive performance characterized by analogic resistive switching remarkably. When the bias voltage is swept repeatedly under high relative humidity level, hydrogen ions will accumulate on the surface and then implant into the lattice of the WO3 nanowire, which leads to a transition from semiconducting WO3 nanowire to metallic HxWO3 nanowire. This insulator-metal transition can be realized more easily after enough electron-hole pairs being excited by laser illumination. The concentration of hydrogen ions in HxWO3 nanowire will decrease when the device is exposed to oxygen atmosphere or the bias voltage is swept in atmosphere with low relative humidity. By modulating the concentration of hydrogen ions, conductive hydrogen tungsten bronze filament might form or rupture near electrodes when the polarity of applied voltage changes, which will endow the device with memristive performance characterized by digital resistive switching.

  16. MWCNT/WO3 nanocomposite photoanode for visible light induced water splitting

    NASA Astrophysics Data System (ADS)

    Yousefzadeh, Samira; Reyhani, Ali; Naseri, Naimeh; Moshfegh, Alireza Z.

    2013-08-01

    The Multi-walled carbon nanotube (MWCNT)/WO3 nanocomposite thin films with different MWCNT’s weight percentages were prepared by sol-gel method as visible light induced photoanode in water splitting reaction. Weight percentage of MWCNT in the all nanocomposite thin films was confirmed by TGA/DSC analysis. According to XPS analysis, oxygenated groups at the surface of the MWCNT and stoichiometric formation of WO3 thin films were determined, while the crystalline structure of the nanocomposite samples was studied by XRD indicating (0 0 2) peak of MWCNT in the monoclinic phase of WO3. The influence of different weight percentage (wt%) of MWCNT on WO3 photoactivity showed that the electron conductivity, charge transfer and electron life time had improved as compared with the pure WO3. Based on linear sweep voltammetry and chronoamperometry measurements, the (1 wt%) MWCNT/WO3 nanocomposite thin films photoanode has a maximum photocurrent density of ~4.5 A/m2 and electron life time of about 57 s.

  17. Preparation, characterization and photocatalytic behavior of WO3-fullerene/TiO2 catalysts under visible light

    PubMed Central

    2011-01-01

    WO3-treated fullerene/TiO2 composites (WO3-fullerene/TiO2) were prepared using a sol-gel method. The composite obtained was characterized by BET surface area measurements, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, transmission electron microscopy, and UV-vis analysis. A methyl orange (MO) solution under visible light irradiation was used to determine the photocatalytic activity. Excellent photocatalytic degradation of a MO solution was observed using the WO3-fullerene, fullerene-TiO2, and WO3-fullerene/TiO2 composites under visible light. An increase in photocatalytic activity was observed, and WO3-fullerene/TiO2 has the best photocatalytic activity; it may attribute to the increase of the photo-absorption effect by the fullerene and the cooperative effect of the WO3. PMID:21774800

  18. DFT study of CO sensing mechanism on hexagonal WO3 (0 0 1) surface: The role of oxygen vacancy

    NASA Astrophysics Data System (ADS)

    Tian, FengHui; Zhao, Linghuan; Xue, Xu-Yan; Shen, Yaoyao; Jia, Xiangfeng; Chen, Shougang; Wang, Zonghua

    2014-08-01

    In this work, density functional theory (DFT) calculations have been used to study the adsorption of CO on the oxygen deficient hexagonal WO3 (h-WO3) (0 0 1) surface. Two different situations including the O- and WO-terminated h-WO3 (0 0 1) surfaces are considered. The influence of surface defect density is also concerned. Calculations proposed that the oxygen vacancy exert negative effects on the sensing ability of the h-WO3 material. Under relatively higher defect density, the presence of the oxygen vacancy on both of the O and WO-terminated (0 0 1) surfaces all decreases their sensitivity to CO gas to some extent, while they are still sensitive enough to detect CO gas with the charge transfers of 0.498 and 0.129 e, respectively. Whereas, under lower defect density, calculations indicated that the sensitivity of the material can be lowered largely.

  19. Comparative studies of monoclinic and orthorhombic WO3 films used for hydrogen sensor fabrication on SiC crystal

    NASA Astrophysics Data System (ADS)

    Zuev, V. V.; Grigoriev, S. N.; Romanov, R. I.; Fominski, V. Y.; Volosova, M. A.; Demin, M. V.

    2016-09-01

    Amorphous WOx films were prepared on the SiC crystal by using two different methods, namely, reactive pulsed laser deposition (RPLD) and reactive deposition by ion sputtering (RDIS). After deposition, the WOx films were annealed in an air. The RISD film possessed a m-WO3 structure and consisted of closely packed microcrystals. Localized swelling of the films and micro-hills growth did not destroy dense crystal packing. RPLD film had layered β-WO3 structure with relatively smooth surface. Smoothness of the films were destroyed by localized swelling and the micro-openings formation was observed. Comparative study of m-WO3/SiC, Pt/m-WO3/SiC, and P-WO3/SiC samples shows that structural characteristics of the WO3 films strongly influence on the voltage/current response as well as on the rate of current growth during H2 detection at elevated temperatures.

  20. Continuous-wave laser operation of Tm and Hoco-doped NaY(WO(4))(2) and NaLu(WO(4))(2) crystals.

    PubMed

    Han, X; Fusari, F; Serrano, M D; Lagatsky, A A; Cano-Torres, J M; Brown, C T A; Zaldo, C; Sibbett, W

    2010-03-15

    Tetragonal single crystals of NaT(WO(4))(2) (T = Y or Lu) co-doped with Tm(3+) and Ho(3+) ions have been employed for broadly tunable and efficient room-temperature laser operation at around 2 mum. With Ti:sapphire laser pumping at 795 nm, a slope efficiency and a maximum output power as high as 48% and 265 mW, respectively, have been achieved at 2050 nm from a Tm,Ho:NaY(WO(4))(2) crystal. Tuning from 1830 nm to 2080 nm has also been obtained using an intracavity Lyot filter.

  1. Effect of fluorine, nitrogen, and carbon impurities on the electronic and magnetic properties of WO{sub 3}

    SciTech Connect

    Shein, I. R.; Ivanovskii, A. L.

    2013-06-15

    Within electron density functional theory with the use of the Vienna ab-initio simulation package (VASP), the effect of the sp substitutional impurities of fluorine (n-type dopant), nitrogen, and carbon (p-type dopants) on the electronic and magnetic properties of tungsten trioxide WO{sub 3} is studied. It is established that these impurities induce the transformation of tungsten trioxide (nonmagnetic semiconductor) into nonmagnetic metal (WO{sub 3}:F), magnetic semimetal (WO{sub 3}:N), or magnetic metal (WO{sub 3}:C) states.

  2. Inductive effect of poly(vinyl pyrrolidone) on morphology and photocatalytic performance of Bi2WO6

    NASA Astrophysics Data System (ADS)

    Zhang, Qiang; Chen, Jinxing; Xie, Yunyun; Wang, Mozhen; Ge, Xuewu

    2016-04-01

    Bi2WO6 has great potential applications in the field of photocatalyst due to its excellent visible-light photocatalytic performance. This work studied the detailed morphological evolution of Bi2WO6 particles synthesized in a simple hydrothermal system induced by the stabilizer poly(vinyl pyrrolidone) (PVP). The XRD and HRTEM results show PVP would not change the crystal structure of Bi2WO6, but the distribution of PVP on the initially formed Bi2WO6 nanosheets will induce the crystal growth, resulting in a distinct morphology evolution of Bi2WO6 with the increase of the concentration of PVP. At the same time, with the increase of the molecular weight of PVP, the morphology of Bi2WO6 varied from simple sheet-like (S-BWO) to some complicated morphology, such as flower-like (F-BWO), red blood cell-like (B-BWO), and square-pillar-like (SP-BWO). The photocatalytic performances of Bi2WO6 with various morphologies on the decomposition of RhB under visible light irradiation reveal that S-BWO has the best photocatalytic performance, while SP-BWO has the worst. This work not only gives the explanation of the inductive effect of PVP molecular chains on the morphological formation of Bi2WO6 particles, but also provides the controllable way to the preparation of Bi2WO6 with various morphologies taking advantage of the stabilizer PVP.

  3. Experimental and theoretical investigation of a mesoporous KxWO3 material having superior mechanical strength

    NASA Astrophysics Data System (ADS)

    Dey, Sonal; Anderson, Sean T.; Mayanovic, Robert A.; Sakidja, Ridwan; Landskron, Kai; Kokoszka, Berenika; Mandal, Manik; Wang, Zhongwu

    2016-01-01

    Mesoporous materials with tailored properties hold great promise for energy harvesting and industrial applications. We have synthesized a novel tungsten bronze mesoporous material (KxWO3; x ~ 0.07) having inverse FDU-12 type pore symmetry and a crystalline framework. In situ small angle X-ray scattering (SAXS) measurements of the mesoporous K0.07WO3 show persistence of a highly ordered meso-scale pore structure to high pressure conditions (~18.5 GPa) and a material with remarkable mechanical strength despite having ~35% porosity. Pressure dependent in situ SAXS measurements reveal a bulk modulus κ = 44 +/- 4 GPa for the mesoporous KxWO3 which is comparable to the corresponding value for the bulk monoclinic WO3 (γ-WO3). Evidence from middle angle (MAXS) and wide angle X-ray scattering (WAXS), high-resolution transmission electron microscopy (HR-TEM) and Raman spectroscopy shows that the presence of potassium leads to the formation of a K-bearing orthorhombic tungsten bronze (OTB) phase within a monoclinic WO3 host structure. Our ab initio molecular dynamics calculations show that the formation of the OTB phase provides superior strength to the mesoporous K0.07WO3.Mesoporous materials with tailored properties hold great promise for energy harvesting and industrial applications. We have synthesized a novel tungsten bronze mesoporous material (KxWO3; x ~ 0.07) having inverse FDU-12 type pore symmetry and a crystalline framework. In situ small angle X-ray scattering (SAXS) measurements of the mesoporous K0.07WO3 show persistence of a highly ordered meso-scale pore structure to high pressure conditions (~18.5 GPa) and a material with remarkable mechanical strength despite having ~35% porosity. Pressure dependent in situ SAXS measurements reveal a bulk modulus κ = 44 +/- 4 GPa for the mesoporous KxWO3 which is comparable to the corresponding value for the bulk monoclinic WO3 (γ-WO3). Evidence from middle angle (MAXS) and wide angle X-ray scattering (WAXS), high

  4. Synthesis and photoactivity enhancement of Ba doped Bi{sub 2}WO{sub 6} photocatalyst

    SciTech Connect

    Li, Wen Ting; Huang, Wan Zhen; Zhou, Huan; Yin, Hao Yong; Zheng, Yi Fan; Song, Xu Chun

    2015-04-15

    Highlights: • The Ba-doped Bi{sub 2}WO{sub 6} photocatalyst have been synthesized by a hydrothermal route. • The photocatalytic activity of Bi{sub 2}WO{sub 6} was greatly enhanced by Ba-doping. • The effect of Ba on the catalytic activity of Bi{sub 2}WO{sub 6} was studied and discussed. - Abstract: In this study, Bi{sub 2}WO{sub 6} doped with different barium contents were successfully prepared by a simple hydrothermal route at 180 °C for 12 h. The as-synthesized samples were characterized in detailed by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis diffusere flectance spectroscopy (UV–vis DRS) and Brunauer–Emmet–Teller (BET) theory. Their photocatalytic activities were evaluated by photodegradation of Rhodamine B (RhB) under simulated solar light. As a result, the photocatalytic properties were enhanced after Ba doping and the Ba-doped Bi{sub 2}WO{sub 6} with R{sub Ba} = 0.15 showed the highest photocatalytic activities of 96.3% RhB was decomposed in 50 min. Close investigation revealed that the proper Ba doped into Bi{sub 2}WO{sub 6} could not only increases its BET surface area, decrease its crystalline size, but also act as electron traps and facilitate the separation of photogenerated electron–hole pairs. The mechanism of enhanced photocatalytic activities of Ba-doped Bi{sub 2}WO{sub 6} were further investigated.

  5. Synthesis of WO 3 nanoparticles for superthermites by the template method from silica spheres

    NASA Astrophysics Data System (ADS)

    Gibot, Pierre; Comet, Marc; Vidal, Loic; Moitrier, Florence; Lacroix, Fabrice; Suma, Yves; Schnell, Fabien; Spitzer, Denis

    2011-05-01

    Nanosized WO 3 tungsten trioxide was prepared by calcination of H 3P 4W 12O 40· xH 2O phosphotungstic acid, previously dissolved in a silica colloidal solution. The influence of the silica spheres/tungsten precursor weight ratio ( x) was investigated. The pristine oxide powders were characterized by XRD, nitrogen adsorption, SEM and TEM techniques. A specific surface area and a pore volume of 64.2 m 2 g -1 and 0.33 cm 3 g -1, respectively, were obtained for the well-crystallized WO 3 powder prepared with x = 2/3 and after the removal of the silica template. The WO 3 particles exhibit a sphere-shaped morphology with a particle size of 13 and 320 nm as function of the x ratio. The performance and the sensitivity levels of the thermites prepared from aluminium nanoparticles mixed with (i) the smallest tungsten (VI) oxide material and (ii) the microscale WO 3 were compared. The combustion of these energetic composites was investigated by time resolved cinematography (TRC). This unconventional experimental technique consists to ignite the dried compressed composites by using a CO 2 laser beam, in order to determine their ignition delay time (IDT) and their combustion rate. The downsizing WO 3 particles improves, without ambiguity, the energetic performances of the WO 3/Al thermite. For instance, the ignition delay time was greatly shortened from 54 ± 10 ms to 5.7 ± 0.2 ms and the combustion velocity was increased by a factor 50 to reach a value of 4.1 ± 0.3 m/s. In addition, the use of WO 3 nanoparticles sensitizes the mixture to mechanical stimuli but decreases the sensitivity to electrostatic discharge.

  6. Deactivation of the TiO2 photocatalyst by coupling with WO3 and the electrochemically assisted high photocatalytic activity of WO3.

    PubMed

    Tada, Hiroaki; Kokubu, Akio; Iwasaki, Mitsunobu; Ito, Seisihro

    2004-05-25

    Patterned TiO2 stripes were formed on a sol-gel crystalline WO3 film by using a chemically modified sol-gel method (pat-TiO2/WO3), and the coupling effect on the photocatalytic activity was studied. Although the photoinduced electron transfer from TiO2 to WO3 was confirmed by labeling and visualization of the reduction sites with Ag particles, the photocatalytic activities of TiO2 for both the gas-phase oxidation of CH3CHO and the liquid-phase oxidation of 2-naphthol decreased significantly with the coupling. This finding was rationalized in terms of the decrease in the rate of the electron transfer from the semiconductor-(s) to 02 with the coupling, which was estimated from the kinetic analysis of the photopotential relaxation. When the excited electrons were removed by a SnO2 underlayer, the WO3 film exhibited a high photocatalytic activity exceeding that of TiO2 for the oxidation of 2-naphthol.

  7. Structural, vibrational and luminescence properties of the (1−x)CaWO{sub 4}−xCdWO{sub 4} system

    SciTech Connect

    Taoufyq, A.; Guinneton, F.; Valmalette, J-C.; Arab, M.; Benlhachemi, A.; Bakiz, B.; Villain, S.; and others

    2014-11-15

    In the present work, we investigate the structural, microstructural, vibrational and luminescence properties of the system (1−x)CaWO{sub 4}−xCdWO{sub 4} with x ranging between 0 and 1. Polycrystalline samples were elaborated using a coprecipitation technique followed by thermal treatment at 1000 °C. The samples were then characterized using X-ray diffraction, scanning electron microscopy, Raman spectroscopy and luminescence analyses. X-ray diffraction profile analyses using Rietveld method showed that two kinds of solid solutions Ca{sub 1−x}Cd{sub x}WO{sub 4} having scheelite and wolframite structures, with respectively tetragonal and monoclinic crystal cells, were observed, with a biphasic system for compositions x=0.6 and 0.7. The scanning electron microscopy experiments showed a complex evolution of morphologies and crystallite sizes as x increased. The vibration modes of Raman spectra were characteristic of composition-dependent disordered solid solutions with decreasing wavenumbers as x increased. Luminescence experiments were performed under UV-laser light irradiation. The energies of emission bands increased linearly with cadmium composition x. The integrated intensity of luminescence reached a maximum value for the substituted wolframite phase with composition x=0.8. - Graphical abstract: Luminescence on UV excitation (364.5 nm) of (1−x)CaWO{sub 4−x}CdWO{sub 4} system, elaborated from coprecipitation technique at 1000 °C, with 0WO{sub 4} polycrystalline phases with 0≤x≤0.5. (b) Maximum of luminescence intensity for the composition x=0.8. - Highlights: • Solid solutions Ca{sub 1−x}Cd{sub x}WO{sub 4} are elaborated from coprecipitation technique. • The structures of two types of solid solutions are refined using Rietveld method. • A maximum of luminescence is obtained for an intermediate composition x=0.8.

  8. TiO2(B) nanoparticle-functionalized WO3 nanorods with enhanced gas sensing properties.

    PubMed

    Zhang, Hongxin; Wang, Shurong; Wang, Yanshuang; Yang, Jiedi; Gao, Xueling; Wang, Liwei

    2014-06-14

    In this work, TiO2(B) nanoparticle (NP)-functionalized WO3 nanorods (NRs) were synthesized by a two-step solution strategy, with a hydrothermal process for WO3 NRs and hydrolyzation of Ti(OBu)4 for the functionalization of TiO2(B) NPs. Various techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), were employed to investigate the morphology, microstructure, crystalline nature and chemical composition of the prepared TiO2(B) NP-functionalized WO3 NRs. SEM and TEM results revealed that the TiO2(B)-WO3 composite showed a rod-like nanostructure with a diameter in the range from 93 to 154 nm and a rough surface, which could increase the accessible surface area and the amount of surface active sites, thus improving the properties or performance of the as-prepared composite NRs. XRD and XPS analysis clearly verified that monoclinic TiO2(B) NPs, a metastable polymorph of TiO2, were successfully supported on the WO3 NRs. Gas sensing measurement results for several common reductive organic gases such as acetone, ethanol, ether, methanol and formaldehyde demonstrated that the sensor based on the as-obtained TiO2(B) NP-functionalized WO3 NRs exhibited obviously enhanced responses compared with a pure WO3 NR based sensor, as well as fast response-recovery speeds, good reproducibility and good stability, indicating their promising application in gas sensors. The excellent gas sensing performance could be attributed to the unique 1D rod-like nanostructure with a rough surface, the existence of TiO2-WO3 heterojunctions and the catalytic effect of the TiO2(B) NPs. The as-prepared TiO2(B) NP-functionalized WO3 NRs will also have very good prospects in electrochromic devices and catalysis applications.

  9. Synthesis of ZnWO4 Electrode with tailored facets: Deactivating the Microorganisms through Photoelectrocatalytic methods

    NASA Astrophysics Data System (ADS)

    Zhan, Su; Zhou, Feng; Huang, Naibao; Liu, Yujun; He, Qiuchen; Tian, Yu; Yang, Yifan; Ye, Fei

    2017-01-01

    The exotic invasive species from the ballast water in the ship will bring about serious damages to ecosystem. Photocatalyst films have been widely studied for sterilization. In this study, ZnWO4 with different exposed facets was synthesized by hydrothermal method, and ZnWO4 film electrodes have been applied in ballast water treatment through the electro-assisted photocatalytic system. Then the samples were investigated by X-ray diffraction (XRD), X-ray photo-electron spectroscopy (XPS), Field emission on scanning electron microcopy (FE-SEM), Transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS), BET specific surface area analysis, Fourier transform infrared (FT-IR) and Electrochemical impedance spectra (EIS). ZnWO4 with an appropriate exposure of (0 1 1) facets ratio exhibited the best photocatalytic and photoelectrocatalytic activities. The microorganisms deactivated completely in 10 min by ZnWO4 films with 3 V bias. The mechanisms of (0 1 1) facets enhanced the photocatalytic and photoelectrocatalytic activities which were deduced based on the calculated result from the first principles. Simultaneously, appropriate exposed facets and applied bias could reduce the recombination of the photogenerated electron-hole pairs, and improve the photocatalytic activities of ZnWO4.

  10. Fabrication of core/shell ZnWO4/carbon nanorods and their Li electroactivity

    NASA Astrophysics Data System (ADS)

    Shim, Hyun-Woo; Lim, Ah-Hyeon; Lee, Gwang-Hee; Jung, Hang-Chul; Kim, Dong-Wan

    2012-01-01

    Carbon-coated ZnWO4 [C-ZW] nanorods with a one-dimensional core/shell structure were synthesised using hydrothermally prepared ZnWO4 and malic acid as precursors. The effects of the carbon coating on the ZnWO4 nanorods are investigated by thermogravimetry, high-resolution transmission electron microscopy, and Raman spectroscopy. The coating layer was found to be in uniform thickness of approximately 3 nm. Moreover, the D and G bands of carbon were clearly observed at around 1,350 and 1,600 cm-1, respectively, in the Raman spectra of the C-ZW nanorods. Furthermore, lithium electroactivities of the C-ZW nanorods were evaluated using cyclic voltammetry and galvanostatic cycling. In particular, the formed C-ZW nanorods exhibited excellent electrochemical performances, with rate capabilities better than those of bare ZnWO4 nanorods at different current rates, as well as a coulombic efficiency exceeding 98%. The specific capacity of the C-ZW nanorods maintained itself at approximately 170 mAh g-1, even at a high current rate of 3 C, which is much higher than pure ZnWO4 nanorods.

  11. The Facile Hydrothermal Preparation of Orthorhombic WO3 With (001) Facet and Its Photocatalytic Performance.

    PubMed

    Deng, Xiaoyan; Dou, Jinbiao; Li, Fenfen; Gao, Hongtao; Liu, Guangjun

    2015-12-01

    The orthorhombic WO3 nanoplates with (001) facet were fabricated via a facile hydrothermal process, using HBF4 as the acid source. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and UV-vis diffused reflectance spectroscopy (DRS), respectively. It indicated that the obtained product was orthorhombic WO3 (JCPDS No. 20-1324). And the energy gap was estimated to be 2.52 eV by the intersection point of the tangent of the absorption edge and the baseline. It was affirmed that WO3 crystalline grew along the (001) direction, indicating the product was exposed with (001) facet. The photocatalytic activity of (001) WO3 nanoplates was investigated on the degradation of Rhodamine B (RhB). It demonstrated that photocatalysts exhibited obvious photocatalytic performance under visible light irradiation. The degradation rate of RhB with the typical product reached 95% after being irradiated for 5 h. It indicated that the photocatalytic efficiency of WO3 could be improved by controlling the crystal growth and its morphology.

  12. Oxygen partial pressure effects on the magnetron sputtered WO3 films

    NASA Astrophysics Data System (ADS)

    Merhan Muğlu, G.; Gür, E.

    2016-04-01

    Electrochromism is changing color of a substance in response to the applied an external electric field and the phenomenon is reversible. WO3 is very attractive material due to its electrochromic properties as well as it is also attractive for many different applications such as gas sensors, phosphorous screen, textile, glass industry. In this study, it is aimed to provide optimization of the optical and structural characteristics of WO3 by changing the growth parameters mainly the oxygen partial pressure. The partial pressure of oxygen was changed with increments of 0.7 mTorr. For the analysis, X-ray Diffraction (XRD), absorption, Raman spectroscopy measurements were used. When O2 gas increased, peaks belong to the WO3 was observed in XRD patterns at the 2 theta angles of 23.0, 11.0, 23.5 and 28.5 angles corresponding to the (002), (020) and (220) planes, respectively. This shows that there is a significant effect of increasing O2 partial pressure in the formation of WO3 films. The bandgap energy of the WO3 thin films are found to be around 3.0 eV. Raman measurements showed vibrational modes of W-O-W stretching and bending modes which shows small shifts depending on the partial pressures of the O2. Obtained results indicated that better crystal structure is obtained with higher O2 gas partial pressure.

  13. Electrical characterization of H2S adsorption on hexagonal WO3 nanowire at room temperature

    NASA Astrophysics Data System (ADS)

    Liu, Binquan; Tang, Dongsheng; Zhou, Yong; Yin, Yanling; Peng, Yuehua; Zhou, Weichang; Qin, Zhu'ai; Zhang, Yong

    2014-10-01

    We have characterized the electrical transport properties of Au/WO3 nanowire/Au devices in ambient air and gaseous H2S to investigate the adsorption kinetics of H2S molecules on the surface of WO3 nanowire at room temperature. The WO3 nanowire devices exhibit increasing linear conductance and electrical hysteresis in H2S. Furthermore, the contact type between Au electrode and WO3 nanowire can be converted from original ohmic/Schottky to Schottky/ohmic after being exposed to H2S. These results suggest that adsorbed H2S molecules are oxidized by holes to form hydrogen ions and S atoms, which will result in formation of hydrogen tungsten bronze and desorption of previously chemically adsorbed H2O molecules. Adsorbed H2S molecules can also oxidize previously adsorbed and ionized oxygen, which will release the electrons from the ionized oxygen and then weaken upward band bending at the surface of WO3 nanowire.

  14. Characterization of nanosized Al{sub 2}(WO{sub 4}){sub 3}

    SciTech Connect

    Nihtianova, D.; Velichkova, N.; Nikolova, R.; Koseva, I.; Yordanova, A.; Nikolov, V.

    2011-11-15

    Graphical abstract: TEM method allows to detect small quantities of impurities not detectable by other methods. In our case impurities of W{sub 5}O{sub 14} are detected in Al{sub 2}(WO{sub 4}){sub 3} nanopowder. Highlights: {yields} Nanosized Al{sub 2}(WO{sub 4}){sub 3} by simple co-precipitation method. {yields} Spherical particles with mean size of 22 nm distributed between 10 and 40 nm at 630 {sup o}C. {yields} XRD, DTA and TEM confirm well defined products with perfect structure. {yields} TEM locality allows detection of impurities not detectable by XRD and DTA. -- Abstract: Nanosized aluminum tungstate Al{sub 2}(WO{sub 4}){sub 3} was prepared by co-precipitation reaction between Na{sub 2}WO{sub 4} and Al(NO{sub 3}){sub 3} aqueous solutions. The powder size and shape, as well as size distribution are estimated after different conditions of powder preparation. The purity of the final product was investigated by XRD and DTA analyses, using the single crystal powder as reference. Between the specimen and the reference no difference was detected. The crystal structure of Al{sub 2}(WO{sub 4}){sub 3} nanosized powder was confirmed by TEM (SAED, HRTEM). In additional, TEM locality allows to detect some W{sub 5}O{sub 14} impurities, which are not visible by conventional X-ray powder diffraction and thermal analyses.

  15. Agx@WO3 core-shell nanostructure for LSP enhanced chemical sensors

    PubMed Central

    Xu, Lijie; Yin, Ming-Li; (Frank) Liu, Shengzhong

    2014-01-01

    Exceptional properties of graphene have triggered intensive research on other 2D materials. Surface plasmon is another subject being actively explored for many applications. Herein we report a new class of core-shell nanostructure in which the shell is made of a 2D material for effective plasmonic propagation. We have designed a much enhanced chemical sensor made of plasmonic Agx@(2D-WO3) that combines above advantages. Specifically, the sensor response increases from 38 for Agx-WO3 mixture to 217 for the Agx@(2D-WO3) core-shell structure; response and recovery time are shortened considerably to 2 and 5 seconds; and optimum sensor working temperature is lowered from 370°C to 340°C. Light irradiation is found to increase the Agx@(2D-WO3) sensor response, particularly at blue wavelength where it resonates with the absorption of Ag nanoparticles. Raman scattering shows significantly enhanced intensity for both the 2D-WO3 shell and surface adsorbates. Both the resonance sensor enhancement and the Raman suggest that the improved sensor performance is due to nanoplasmonic mechanism. It is demonstrated that (1) 2D material can be used as the shell component of a core-shell nanostructure, and (2) surface plasmon can effectively boost sensor performance. PMID:25339285

  16. Nanobrick-like WO3 thin films: Hydrothermal synthesis and electrochromic application

    NASA Astrophysics Data System (ADS)

    Kondalkar, V. V.; Kharade, R. R.; Mali, S. S.; Mane, R. M.; Patil, P. B.; Patil, P. S.; Choudhury, S.; Bhosale, P. N.

    2014-09-01

    Nanobrick-like WO3 thin films have been synthesized via facile hydrothermal route. Nanostructured WO3 thin films were characterized using X-ray diffraction (XRD), UV-Vis-NIR spectrophotometer, scanning electron microscopy (SEM), atomic force microscopy (AFM) to investigate the intentional properties such as phase structure, optical properties and surface morphology. Moreover electrochromic (EC) performance of WO3 thin film was investigated in 0.5 M LiClO4/PC by means of cyclic voltammetry (CV), chronocoulometry (CC) and chronoamperometry (CA). The value of diffusion coefficient (D) was determined from anodic peak current and was found to be 1.51 × 10-9 cm2/s. The response time of 6.9 s for bleaching (tb) and 9.7 s for coloration (tc) was observed with excellent reversibility 76%. The coloration efficiency for nanobricks WO3 is 39.24 cm2/C. CIE 1931 L∗ab values for colored and bleached films were estimated at 2° observer using D-65 illumination. The electrochromic studies show highly reversible and the stable nature of WO3 thin film which provides a versatile and promising application towards the fabrication of smart windows.

  17. H.sub.2O doped WO.sub.3, ultra-fast, high-sensitivity hydrogen sensors

    DOEpatents

    Liu, Ping [Denver, CO; Tracy, C Edwin [Golden, CO; Pitts, J Roland [Lakewood, CO; Lee, Se-Hee [Lakewood, CO

    2011-03-22

    An ultra-fast response, high sensitivity structure for optical detection of low concentrations of hydrogen gas, comprising: a substrate; a water-doped WO.sub.3 layer coated on the substrate; and a palladium layer coated on the water-doped WO.sub.3 layer.

  18. ZnWO{sub 4}–Cu system with enhanced photocatalytic activity by photo-Fenton-like synergistic reaction

    SciTech Connect

    Song, Jimei; Wang, Hong; Hu, Gang; Zhao, Shaojuan; Hu, Haiqin; Jin, Baokang

    2012-11-15

    Highlights: ► A novel coupled system of ZnWO{sub 4}–Cu exhibited much higher catalytic activity than pure ZnWO{sub 4} with H{sub 2}O{sub 2} under UV-light irradiation. ► The enhanced catalytic activity of ZnWO{sub 4}–Cu system was due to the synergistic effect of photocatalysis and Fenton-like process. ► The possible mechanism of the synergistic effect was proposed. -- Abstract: A novel coupled system of ZnWO{sub 4}–Cu, combining two different advanced oxidation processes of photocatalysis and Fenton-like for the degradation of organic dyes, was successfully synthesized. The as-synthesized samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS). The nanosized ZnWO{sub 4}–Cu samples exhibited much higher catalytic activity than pure ZnWO{sub 4}. In the presence of the ZC-0.2, the MB solution was completely degraded (the degradation ratio reached 97.79%); while for the ZC-0, the degradation ratio was only 72.29%. The effects of the amount of Cu on the photocatalytic performance of ZnWO{sub 4}–Cu were investigated in detail. The result showed that the synergistic effect between Cu and ZnWO{sub 4} played a key role. The possible mechanism of the synergistic system was proposed.

  19. Synthesis, characterization and electrochemical studies of nanostructured CaWO{sub 4} as platinum support for oxygen reduction reaction

    SciTech Connect

    Farsi, Hossein; Barzgari, Zahra

    2014-11-15

    Highlights: • Nanostructured CaWO{sub 4} was fabricated by co-precipitation method. • Platinum was electrodeposited onto the surface prepared nanostructured CaWO{sub 4}. • Pt/CaWO{sub 4}-graphite demonstrate good oxygen reduction reaction activity. - Abstract: In the present work, we employed nanostructured calcium tungstate as a supporting material for platinum, a well-known electrocatalyst for oxygen reduction. The co-precipitation method has been utilized to synthesize nanostructured calcium tungstate from aqueous solution. The structure and morphology of the obtained CaWO{sub 4} were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Preparation of the Pt/CaWO{sub 4}-graphite catalyst was carried out by electrodeposition of Pt onto the surface of CaWO{sub 4}/graphite electrode. The physical properties of the catalyst were determined by scanning electron microscopy analysis and energy dispersive X-ray (SEM/EDX). The electrochemical activity of the Pt/CaWO{sub 4}-graphite for the oxygen reduction reaction (ORR) was investigated in acid solution by cyclic voltammetry measurements, linear sweep voltammetry, and electrochemical impedance spectroscopy. The results revealed that the Pt/CaWO{sub 4}-graphite has higher electrocatalytic activity for oxygen reduction in comparison with Pt/graphite catalyst.

  20. Photocatalytic energy storage ability of TiO2-WO3 composite prepared by wet-chemical technique.

    PubMed

    Cao, Linglin; Yuan, Jian; Chen, Mingxia; Shangguan, Wenfeng

    2010-01-01

    TiO2-WO3 hybrid photocatalysts were prepared using wet-chemical technique, and their energy storage performance was characterized by electrochemical galvanostatic method. TiO2 powder was coupled with WO3 powder, which was used as electron pool and the reductive energy could be stored in. As a result, the prepared TiO2-WO3 had good energy storage ability while pure TiO2 showed no capacity and pure WO3 showed quite low performance. The energy storage ability was affected by the crystal structure of WO3 and calcination temperature. The photocatalyst had better capacity when WO3 had low degree of crystallinity, since its loose structure made it easier for electrons and cations to pass through. The photocatalytic energy storage performance was also affected by the molar ratio of TiO2 to WO3. Energy storage capacity was significantly dependent on the composition, reaching the maximum value at TiO2/WO3 1:1 (mol/mol).

  1. Flexible electrochromics: magnetron sputtered tungsten oxide (WO3-x) thin films on Lexan (optically transparent polycarbonate) substrates

    NASA Astrophysics Data System (ADS)

    Uday Kumar, K.; Murali, Dhanya S.; Subrahmanyam, A.

    2015-06-01

    Tungsten oxide (WO3-x) based electrochromics on flexible substrates is a topic of recent interest. The present communication reports the electrochromic properties of WO3-x thin films grown on lexan, an optically transparent polycarbonate thermoplastic substrate. The WO3-x films are prepared at room temperature (300 K) by the reactive DC magnetron sputtering technique. The physical properties of metal oxide thin films are known to be controlled by the oxygen stoichiometry of the film. In the present work, the WO3-x thin films are prepared by varying the oxygen flow rates. All the WO3-x thin films are amorphous in nature. The electrochromic performance of the WO3-x thin films is evaluated by cyclic voltammetry measurements on tin doped indium oxide (ITO) coated lexan and glass substrates. The optical band gap of WO3-x thin films grown on lexan substrates (at any given oxygen flow rate) is significantly higher than those grown on glass substrates. The coloration efficiency of WO3-x thin films (at an oxygen flow rate of 10 sccm) on lexan substrates is: 143.9 cm2 C-1 which is higher compared to that grown on glass: 90.4 cm2 C-1.

  2. Facile hydrothermal synthesis of TiO2-Bi2WO6 hollow superstructures with excellent photocatalysis and recycle properties.

    PubMed

    Hou, Ya-Fei; Liu, Shu-Juan; Zhang, Jing-huai; Cheng, Xiao; Wang, You

    2014-01-21

    One-dimensional mesoporous TiO2-Bi2WO6 hollow superstructures are prepared using a hydrothermal method and their photocatalysis and recycle properties are investigated. Experimental results indicate that anatase TiO2 nanoparticles are coupled with hierarchical Bi2WO6 hollow tubes on their surfaces. The TiO2-Bi2WO6 structure has a mesoporous wall and the pores in the wall are on average 21 nm. The hierarchical TiO2-Bi2WO6 heterostructures exhibit the highest photocatalytic activity in comparison with P25, pure Bi2WO6 hollow tube and mechanical mixture of Bi2WO6 tube and TiO2 nanoparticle in the degradation of rhodamine B (RhB) under simulated sunlight irradiation. The as-prepared TiO2-Bi2WO6 heterostructures can be easily recycled through sedimentation and they retains their high photocatalytic activity during the cycling use in the simulated sunlight-driving photodegradation process of RhB. The prepared mesoporous TiO2-Bi2WO6 with hollow superstructure is therefore a promising candidate material for water decontamination use.

  3. ZnO nanoplates surfaced-decorated by WO3 nanorods for NH3 gas sensing application

    NASA Astrophysics Data System (ADS)

    Dien Nguyen, Dac; Do, Duc Tho; Hien Vu, Xuan; Vuong Dang, Duc; Chien Nguyen, Duc

    2016-03-01

    Zinc oxide (ZnO) nanoplates and tungsten trioxide (WO3) nanorods were synthesized by hydrothermal treatment from zinc nitrate/potassium hydroxide and sodium tungstate/hydrochloric acid, respectively. The structure, morphology and compositions of the as-prepared WO3/ZnO nano-composites were characterized by x-ray diffraction, field emission scanning electron microscopy and energy dispersive spectroscopy. The obtained ZnO nanoplates have regular shape, single-crystal wurtzite structure with the thickness of 40 nm and 200 versus 400 nm in lateral dimensions. The WO3 nanorods possess the average diameter of 20 nm and the length of approximately 120 nm which were distributed on the surfaces of ZnO nanoplates. The WO3/ZnO nano-composites were prepared by grinding WO3 nanorods powder with ZnO nanoplates powder in various weight ratios (1:2, 1:1 and 2:1). The NH3 gas sensing properties of WO3/ZnO nano-composites were examined through the electrical resistance measurement. The gas sensing performance of the WO3/ZnO composite with weight ratio of 1:1 was better compared with that of other samples. For this sample, the maximum response to 300 ppm NH3 was 24 at the operating temperature of 250 °C. In addition, the gas sensing mechanism of the WO3/ZnO composites was discussed.

  4. Enhancement of photoelectric response of bacteriorhodopsin by multilayered WO3 x H2O nanocrystals/PVA membrane.

    PubMed

    Li, Rui; Hu, Fengping; Bao, Qiaoliang; Bao, Shujuan; Qiao, Yan; Yu, Shucong; Guo, Jun; Li, Chang Ming

    2010-02-07

    For the first time, a multilayered WO(3) x H(2)O/PVA membrane on bacteriorhodopsin (bR) is constructed to significantly enhance the photoelectric response of bR by the spillover effect of WO(3) x H(2)O nanocrystals, providing great potential in its important applications in bioelectronics and proton exchange membrane fuel cells.

  5. The band structure of WO3 and non-rigid-band behaviour in Na0.67WO3 derived from soft x-ray spectroscopy and density functional theory.

    PubMed

    Chen, B; Laverock, J; Piper, L F J; Preston, A R H; Cho, S W; DeMasi, A; Smith, K E; Scanlon, D O; Watson, G W; Egdell, R G; Glans, P-A; Guo, J-H

    2013-04-24

    The electronic structure of single-crystal WO3 and Na0.67WO3 (a sodium-tungsten bronze) has been measured using soft x-ray absorption and resonant soft x-ray emission oxygen K-edge spectroscopies. The spectral features show clear differences in energy and intensity between WO3 and Na0.67WO3. The x-ray emission spectrum of metallic Na0.67WO3 terminates in a distinct Fermi edge. The rigid-band model fails to explain the electronic structure of Na0.67WO3 in terms of a simple addition of electrons to the conduction band of WO3. Instead, Na bonding and Na 3s-O 2p hybridization need to be considered for the sodium-tungsten bronze, along with occupation of the bottom of the conduction band. Furthermore, the anisotropy in the band structure of monoclinic γ-WO3 revealed by the experimental spectra with orbital-resolved geometry is explained via density functional theory calculations. For γ-WO3 itself, good agreement is found between the experimental O K-edge spectra and the theoretical partial density of states of O 2p orbitals. Indirect and direct bandgaps of insulating WO3 are determined from extrapolating separations between spectral leading edges and accounting for the core-hole energy shift in the absorption process. The O 2p non-bonding states show upward band dispersion as a function of incident photon energy for both compounds, which is explained using the calculated band structure and experimental geometry.

  6. The band structure of WO3 and non-rigid-band behaviour in Na0.67WO3 derived from soft x-ray spectroscopy and density functional theory

    NASA Astrophysics Data System (ADS)

    Chen, B.; Laverock, J.; Piper, L. F. J.; Preston, A. R. H.; Cho, S. W.; DeMasi, A.; Smith, K. E.; Scanlon, D. O.; Watson, G. W.; Egdell, R. G.; Glans, P.-A.; Guo, J.-H.

    2013-04-01

    The electronic structure of single-crystal WO3 and Na0.67WO3 (a sodium-tungsten bronze) has been measured using soft x-ray absorption and resonant soft x-ray emission oxygen K-edge spectroscopies. The spectral features show clear differences in energy and intensity between WO3 and Na0.67WO3. The x-ray emission spectrum of metallic Na0.67WO3 terminates in a distinct Fermi edge. The rigid-band model fails to explain the electronic structure of Na0.67WO3 in terms of a simple addition of electrons to the conduction band of WO3. Instead, Na bonding and Na 3s-O 2p hybridization need to be considered for the sodium-tungsten bronze, along with occupation of the bottom of the conduction band. Furthermore, the anisotropy in the band structure of monoclinic γ-WO3 revealed by the experimental spectra with orbital-resolved geometry is explained via density functional theory calculations. For γ-WO3 itself, good agreement is found between the experimental O K-edge spectra and the theoretical partial density of states of O 2p orbitals. Indirect and direct bandgaps of insulating WO3 are determined from extrapolating separations between spectral leading edges and accounting for the core-hole energy shift in the absorption process. The O 2p non-bonding states show upward band dispersion as a function of incident photon energy for both compounds, which is explained using the calculated band structure and experimental geometry.

  7. Structural investigations of TiO2-WO3-Au porous composites

    NASA Astrophysics Data System (ADS)

    Rusu, M.; Baia, M.; Pap, Zs.; Danciu, V.; Baia, L.

    2014-09-01

    In the present study, a morpho-structural analysis of heat treated TiO2-WO3-Au aerogel composites is presented. Simultaneously, the influence of the loaded Au nanoparticles on the morphological and structural characteristics of the TiO2-WO3 aerogel is also analyzed. X-ray diffraction data (XRD) and Raman spectroscopy measurements indicated that TiO2 crystallizes mainly in anatase phase, while the WO3 structure remains amorphous. The morphological features of the samples, i.e. crystallites mean size, particle size distribution, and specific surface area of the pores, are investigated by using XRD, transmission electron microscopy (TEM), and N2 adsorption/desorption, respectively. The results indicate a decrease in size of the titania crystallites as the tungsten oxide content increases. The diffuse reflectance spectra modified by applying a Kubelka-Munk transformation reveal that the presence of gold nanoparticles improves the material's response in the visible domain.

  8. Synthesis of CaWO4 nanocolloidal suspension via pulsed laser ablation and its optical properties

    NASA Astrophysics Data System (ADS)

    Ryu, Jeong Ho; Park, Gyeong Seon; Kim, Kang Min; Lim, Chang Sung; Yoon, Jong-Won; Shim, Kwang Bo

    2007-09-01

    Pulsed laser ablation (PLA) in the liquid phase was successfully employed to synthesize calcium tungstate (CaWO4) nanocolloidal suspension. The crystalline phase, particle morphology and laser ablation mechanism for the colloidal nanoparticles were investigated using XRD, TEM and SEM. The obtained colloidal suspension consisted of well-dispersed CaWO4 nanoparticles which showed a spherical shape with sizes ranging from 5 to 30 nm. The laser ablation and the nanoparticle forming process were discussed under consideration of the photo-ablation mechanism, where the nanoparticles were generated by rapid condensation of the plume in high pressured ethanol vapor. The optical properties of the prepared CaWO4 colloidal nanoparticles were analyzed in detail using XPS, Raman spectroscopy, UV-Vis spectroscopy and PL spectrophotometry. The optical band gap was estimated by Tauc and Menths law.

  9. Hydrothermal synthesis of assembled sphere-like WO3 architectures and their gas-sensing properties

    NASA Astrophysics Data System (ADS)

    Zhang, Hejing; Liu, Tianmo; Huang, Long; Guo, Weiwei; Liu, Dejun; Zeng, Wen

    2012-04-01

    Unique assembled sphere-like WO3 architectures were successfully synthesized through a facile hydrothermal method in the presence of malic acid followed by subsequent heat treatment. We found that malic acid played a significant role in governing morphologies of WO3·xH2O precursors during hydrothermal process. A possible formation mechanism was also proposed in detail. Experimental results showed that the optimized hydrothermal precursor could be dehydrated to mixed composition of hexagonal and monoclinic WO3 with the unique sphere-like porous architecture after being annealed at 400 °C for 2.5 h. Besides, gas-sensing measurement indicated that the well-defined 3D assembled sphere-like architectures exhibited the highest sensor response to ethanol at the optimal temperature of 250 °C among the samples.

  10. Degradation of dimethylformamide on the surface of the nanosized WO3 films studied by infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Gavrilyuk, A. I.

    2016-07-01

    Here I report on the degradation of dimethylformamide on the surface of the nanosized WO3 films under the action of light. Dimethylformamide, a substance that has a series of interesting properties, was adsorbed on the surface of the WO3 films and its adsorption mechanism and transformations under the action of light have been investigated with the help of the IR spectroscopy. The spirit of the research is that both DMF modifications have been used i.e., conventional and that with the substitution of hydrogen atoms by deuterium. Formation of two weak bonds (donor-acceptor bond and hydrogen bond) provides a great catalytic effect for photo-initiated proton-coupled electron transfer from the adsorbed molecules to the WO3 film surface. The mechanism of the detachment of hydrogen atoms and subsequent transformation of the adsorbed molecules has been investigated and discussed.

  11. Improved Gas Response at Room Temperature of Activated Nanocrystalline WO3 Films

    NASA Astrophysics Data System (ADS)

    Reyes, L. F.; Saukko, S.; Hoel, A.; Lantto, V.; Granqvist, C. G.; Lappalainen, J.

    2004-01-01

    Advanced reactive gas deposition was used to produce pure and Auactivated nanocrystalline WO3 films for gas-sensing studies. Many different methods such as X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive spectroscopy, scanning electron microscopy, and atomic force microscopy were used to characterize structural properties of the films. The WO3 particles in the films had the high-temperature tetragonal crystal structure after deposition, and the average crystallite size was about 10nm. The effect of sintering on structural, electrical, and gassensing properties of both pure and Au-activated WO3 films was also studied. Gas response experiments with films on alumina substrate were done at different operation temperatures, from room temperature up to about 450°C, at exposure to different concentrations of H2S and H2 in dry synthetic air.

  12. Understanding the Potential of WO3 Based Sensors for Breath Analysis

    PubMed Central

    Staerz, Anna; Weimar, Udo; Barsan, Nicolae

    2016-01-01

    Tungsten trioxide is the second most commonly used semiconducting metal oxide in gas sensors. Semiconducting metal oxide (SMOX)-based sensors are small, robust, inexpensive and sensitive, making them highly attractive for handheld portable medical diagnostic detectors. WO3 is reported to show high sensor responses to several biomarkers found in breath, e.g., acetone, ammonia, carbon monoxide, hydrogen sulfide, toluene, and nitric oxide. Modern material science allows WO3 samples to be tailored to address certain sensing needs. Utilizing recent advances in breath sampling it will be possible in the future to test WO3-based sensors in application conditions and to compare the sensing results to those obtained using more expensive analytical methods. PMID:27801881

  13. Effect of Pt Nanoparticles on the Optical Gas Sensing Properties of WO3 Thin Films

    PubMed Central

    Qadri, Muhammad U.; Diaz Diaz, Alex Fabian; Cittadini, Michaela; Martucci, Alessandro; Pujol, Maria Cinta; Ferré-Borrull, Josep; Llobet, Eduard; Aguiló, Magdalena; Díaz, Francesc

    2014-01-01

    Thin films of tungsten trioxide were deposited on quartz substrates by RF magnetron sputtering. Different annealing temperatures in the range from 423 to 973 K were used under ambient atmosphere. The influence of the annealing temperature on the structure and optical properties of the resulting WO3 thin films were studied. The surface morphology of the films is composed of grains with an average size near 70 nm for the films annealed between 773 and 973 K. Some of the WO3 thin films were also coated with Pt nanoparticles of about 45 nm in size. Spectrometric measurements of transmittance were carried out for both types of WO3 samples in the wavelength range from 200–900 nm, to determine the effect of the exposure to two different gases namely H2 and CO. Films showed fast response and recovery times, in the range of few seconds. The addition of Pt nanoparticles enables reducing the operation temperature to room temperature. PMID:24977386

  14. Metal-insulator transition in Na{sub x}WO{sub 3}: Photoemission spectromicroscopy study

    SciTech Connect

    Paul, Sanhita Ghosh, Anirudha Raj, Satyabrata

    2014-04-24

    We have investigated the validity of percolation model, which is quite often invoked to explain the metal-insulator transition in sodium tungsten bronzes, Na{sub x}WO{sub 3} by photoelectron spectromicroscopy. The spatially resolved direct spectromicroscopic probing on both the insulating and metallic phases of high quality single crystals of Na{sub x}WO{sub 3} reveals the absence of any microscopic inhomogeneities embedded in the system within the experimental limit. Neither any metallic domains in the insulating host nor any insulating domains in the metallic host have been found to support the validity of percolation model to explain the metal-insulator transition in Na{sub x}WO{sub 3}.

  15. Synthesis and room-temperature NO2 gas sensing properties of a WO3 nanowires/porous silicon hybrid structure

    NASA Astrophysics Data System (ADS)

    Zeng, Peng; Zhang, Ping; Hu, Ming; Ma, Shuang-Yun; Yan, Wen-Jun

    2014-05-01

    We report on the fabrication and performance of a room-temperature NO2 gas sensor based on a WO3 nanowires/porous silicon hybrid structure. The W18O49 nanowires are synthesized directly from a sputtered tungsten film on a porous silicon (PS) layer under heating in an argon atmosphere. After a carefully controlled annealing treatment, WO3 nanowires are obtained on the PS layer without losing the morphology. The morphology, phase structure, and crystallinity of the nanowires are investigated by using field emission scanning electron microscopy (FESEM), X-ray diffractometer (XRD), and high-resolution transmission electron microscopy (HRTEM). Comparative gas sensing results indicate that the sensor based on the WO3 nanowires exhibits a much higher sensitivity than that based on the PS and pure WO3 nanowires in detecting NO2 gas at room temperature. The mechanism of the WO3 nanowires/PS hybrid structure in the NO2 sensing is explained in detail.

  16. Signature of polaron formation in Na0.025WO3: Photoemission and X-ray diffraction investigations

    NASA Astrophysics Data System (ADS)

    Paul, Sanhita; Ghosh, Anirudha; Raj, Satyabrata

    2013-06-01

    We have carried out temperature dependent high-resolution angle-resolved photoemission spectroscopy and x-ray diffraction studies on non-stoichiometric sodium tungsten bronzes (NaxWO3 for x=0.025). Our photoemission investigation shows evidence for polaron formation at the valence band edge and the photoemission spectra collected in different modes of the electron analyzer suggest that the density of states at valence band edge gradually moves to other k-points in the Brillouin zone with increasing temperature and explain the dynamics of polaron formation in Na0.025WO3. Infact our x-ray diffraction measurements reveal a structural modification of Na0.025WO3 around 230K. The corner sharing WO6 octadedra gets sufficiently distorted at low temperature due to displacement of tugsten and oxygen atoms from their mean position. This structural modification induces polaron formation in Na0.025WO3 below 230K.

  17. Synthesis and photo-degradation application of WO3/TiO2 hollow spheres.

    PubMed

    Lv, Kezhen; Li, Jie; Qing, Xiaoxia; Li, Wenzhang; Chen, Qiyuan

    2011-05-15

    A WO(3)/TiO(2) composite, hollow-sphere photocatalyst with average diameter of 320 nm and shell thickness of 50 nm was successfully prepared using a template method. UV-vis diffuse reflectance spectra illustrated that the main absorption edges of the WO(3)/TiO(2) hollow spheres were red-shifted compared to the TiO(2) hollow spheres, indicating an extension of light absorption into the visible region of the composite photocatalyst. The WO(3) and TiO(2) phases were confirmed by X-ray diffraction analysis. BET isotherms revealed that the specific surface area and average pore diameter of the hollow spheres were 40.95 m(2)/g and 19 nm, respectively. Photocatalytic experiments indicate that 78% MB was degraded by WO(3)/TiO(2) hollow spheres under visible light within 80 min. Under the same conditions, only 24% MB can be photodegraded by TiO(2). The photocatalytic mineralization of MB, catalyzed by TiO(2) and WO(3)/TiO(2), proceeded at a significantly higher rate under UV irradiation than that under visible light, and more significant was the increase in the apparent rate constant with the WO(3)/TiO(2) composite semiconductor material which was 3.2- and 3.5-fold higher than with the TiO(2) material under both UV and visible light irradiation. The increased photocatalytic activity of the coupled nanocomposites was attributed to photoelectron/hole separation efficiency and the extension of the wavelength range of photoexcitation.

  18. Photoluminescence in the Ca{sub x}Sr{sub 1-x}WO{sub 4} system at room temperature

    SciTech Connect

    Porto, S.L.; Longo, E.; Simoes, L.G.P.; Lima, S.J.G.; Ferreira, J.M.; Soledade, L.E.B.; Espinoza, J.W.M.; Cassia-Santos, M.R.; Maurera, M.A.M.A.; Paskocimas, C.A.; Santos, I.M.G. Souza, A.G.

    2008-08-15

    In this work, a study was undertaken about the structural and photoluminescent properties, at room temperature, of powder samples from the Ca{sub x}Sr{sub 1-x}WO{sub 4} (x=0-1.0) system, synthesized by a soft chemical method and heat treated between 400 and 700 deg. C. The material was characterized using Infrared, UV-vis and Raman spectroscopy and XRD. The most intense PL emission was obtained for the sample calcined at 600 deg. C, which is neither highly disordered (400-500 deg. C), nor completely ordered (700 deg. C). Corroborating the role of disorder in the PL phenomenon, the most intense PL response was not observed for pure CaWO{sub 4} or SrWO{sub 4}, but for Ca{sub 0.6}Sr{sub 0.4}WO{sub 4}. The PL emission spectra could be separated into two Gaussian curves. The lower wavelength peak is placed around 530 nm, and the higher wavelength peak at about 690 nm. Similar results were reported in the literature for both CaWO{sub 4} and SrWO{sub 4}. - Graphical abstract: The structural and room temperature photoluminescence of Ca{sub x}Sr{sub 1-x}WO4 synthesized by a soft chemical method was studied. The most intense PL emission was obtained for the sample calcined at 600 deg. C, that is neither highly disordered (400-500 deg. C), nor completely ordered (700 deg. C). Corroborating the role of disorder in the PL phenomenon, the most intense PL response was not observed for pure CaWO{sub 4} or SrWO{sub 4}, but for Ca{sub 0.6}Sr{sub 0.4}WO{sub 4}.

  19. One-dimensional WO{sub 3} and its hydrate: One-step synthesis, structural and spectroscopic characterization

    SciTech Connect

    Iwu, Kingsley O.; Galeckas, Augustinas; Rauwel, Protima; Kuznetsov, Andrej Y.; Norby, Truls

    2012-01-15

    We report on a one-step hydrothermal growth of one-dimensional (1D) WO{sub 3} nanostructures, using urea as 1D growth-directing agent and a precursor free of metals other than tungsten. By decreasing the pH of the starting solution, the size of the nanostructures was reduced significantly, this development being accompanied by the realization of phase pure hexagonal WO{sub 3} nanorods (elimination of monoclinic impurity phase) and a red shift in optical absorption edge. Surface analyses indicated the presence of reduced tungsten species in the WO{sub 3} nanostructures, which increased two-fold in a hydrated WO{sub 3} phase obtained with further decrease in pH. We suggest that oxygen vacancies are responsible for this defect state in WO{sub 3}, while protons are responsible or contribute significantly to the same in the hydrated phase. - Graphical abstract: The figure illustrates the role of pH in morphological and absorption edge evolution of WO{sub 3} (hydrate) as well as the variation in the concentration of defect electrons between anhydrous and hydrated WO{sub 3}. Highlights: Black-Right-Pointing-Pointer WO{sub 3} nanorods prepared in a one step procedure. Black-Right-Pointing-Pointer HCl (aq) enables phase pure WO{sub 3} nanorods. Black-Right-Pointing-Pointer HCl (aq) induces significant reduction in dimension of and red shift in absorption edge of nanorods. Black-Right-Pointing-Pointer W{sup 5+} detected in hydrothermal WO{sub 3} phase, the concentration of which increases in the hydrated phase. Black-Right-Pointing-Pointer W{sup 5+} from the two phases due to different positive defects.

  20. Hydrothermal synthesis of NiWO4 crystals for high performance non-enzymatic glucose biosensors

    PubMed Central

    Mani, Sivakumar; Vediyappan, Veeramani; Chen, Shen-Ming; Madhu, Rajesh; Pitchaimani, Veerakumar; Chang, Jia-Yaw; Liu, Shang-Bin

    2016-01-01

    A facile hydrothermal route for the synthesis of ordered NiWO4 nanocrystals, which show promising applications as high performance non-enzymatic glucose sensor is reported. The NiWO4-modified electrodes showed excellent sensitivity (269.6 μA mM−1 cm−2) and low detection limit (0.18 μM) for detection of glucose with desirable selectivity, stability, and tolerance to interference, rendering their prospective applications as cost-effective, enzyme-free glucose sensors. PMID:27087561

  1. End pumped yellow laser performance of Dy3+:ZnWO4

    NASA Astrophysics Data System (ADS)

    Xia, Zhongchao; Yang, Fugui; Qiao, Liang; Yan, Fengpo

    2017-03-01

    We report an end pumped single transverse-mode (TEM00) yellow laser based on Dy3+:ZnWO4 crystal. The pump light is InGaN blue laser diode at 450 nm with the maximum power of 1.5 W. A 3 cm length Dy3+:ZnWO4 crystal served as the gain medium. By way of the square filter, we discuss the TEM00 properties. In continuous-wave operation and single transverse-mode, a maximum output power of 0.110 W and a slope efficiency of 13.0% are achieved at an emission wavelength of 575 nm.

  2. Surface morphology-controlled fabrication of Na2WO4 films with high structural stability

    NASA Astrophysics Data System (ADS)

    Yang, Dachi; Hernandez, Jose A.; Katiyar, Ram S.; Fonseca, Luis F.

    2016-06-01

    Films with designed surface morphologies are of great importance for high-performance devices and other applications such as gas sensors and catalysts. Na2WO4 films with various surface morphologies have been fabricated via physical evaporation inside the chamber created by approaching mouth to mouth two alumina boats containing precursors and by covering alumina boat with aluminum foil, respectively. The temperature-dependence Raman investigation reveals red shifting of the Raman peaks with increasing temperature in all cases. The observed Raman shifts are relatively small confirming high stability of the Na2WO4 films within the investigated temperature range.

  3. Optical Properties of Potassium Erbium Double Tungstate KEr(WO4)2

    DTIC Science & Technology

    2001-01-01

    UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADPO 11914 TITLE: Optical Properties of Potassium Erbium Double Tungstate ...potassium erbium double tungstate KEr(W0 4)2 T.Zayarnyukl*, M.T.Borowiecl*, V.DyakonovŖ, H.Szymczak’, E.Zubov Ŗ, A.Pavlyuk3, M.Barafiski’ 1Institute of... tungstate KEr(WO4)2 are reported. The single crystals of KEr(WO4)2 were grown by Top Seeded Solution Growth (TSSG) technique. They belong to the chain

  4. Structural analysis and optical properties of the Bi2–xYxWO6 system

    PubMed Central

    Pasternak, S.; Levy, D.; Paz, Y.

    2016-01-01

    Photocatalytic conversion of solar energy into chemical energy has attracted considerable interest for several decades. One compound already reported as a visible-light-active photocatalyst for water splitting is BiYWO6, a member of the Bi2–xYxWO6 family of compounds. The structural and optical properties of other members of this family have not been reported to date. In this work, we synthesized various compositions of Bi2–xYxWO6, studied their optical properties, and report their structural parameters obtained by utilizing powder diffraction coupled with Rietveld refinement. PMID:28066155

  5. Hydrothermal synthesis of NiWO4 crystals for high performance non-enzymatic glucose biosensors

    NASA Astrophysics Data System (ADS)

    Mani, Sivakumar; Vediyappan, Veeramani; Chen, Shen-Ming; Madhu, Rajesh; Pitchaimani, Veerakumar; Chang, Jia-Yaw; Liu, Shang-Bin

    2016-04-01

    A facile hydrothermal route for the synthesis of ordered NiWO4 nanocrystals, which show promising applications as high performance non-enzymatic glucose sensor is reported. The NiWO4-modified electrodes showed excellent sensitivity (269.6 μA mM-1 cm-2) and low detection limit (0.18 μM) for detection of glucose with desirable selectivity, stability, and tolerance to interference, rendering their prospective applications as cost-effective, enzyme-free glucose sensors.

  6. Synthesis and characterization of novel WO{sub 3} loaded Ag–ZnO and its photocatalytic activity

    SciTech Connect

    Subash, B.; Krishnakumar, B.; Pandiyan, V.; Swaminathan, M.; Shanthi, M.

    2013-01-15

    Graphical abstract: Display Omitted Highlights: ► A novel WO{sub 3} loaded Ag–ZnO was prepared by a simple solvothermal method. ► ‘Ag’ traps the electron from both ZnO and WO{sub 3} reducing electro–hole recombination. ► WO{sub 3}–Ag–ZnO is more efficient than Ag–ZnO, WO{sub 3}–ZnO, Ag–WO{sub 3} and undoped catalysts. ► WO{sub 3}–Ag–ZnO material will be much useful for the treatment of dye effluents. -- Abstract: A novel WO{sub 3} loaded Ag–ZnO photocatalyst was successfully synthesized by a simple solvothermal method and characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) images, energy dispersive spectrum (EDS), diffuse reflectance spectra (DRS), photoluminescence spectra (PL), cyclic voltammetry (CV) and Brunauer–Emmett–Teller (BET) surface area measurements. The photocatalytic activity of WO{sub 3}–Ag–ZnO was investigated for the degradation of RR 120 and RO 4 dyes in aqueous solution using UV-A light. WO{sub 3}–Ag–ZnO is found to be more efficient than Ag–ZnO, WO{sub 3}–ZnO, Ag–WO{sub 3}, commercial ZnO, prepared ZnO, TiO{sub 2}-P25 and TiO{sub 2} (Merck) at neutral pH for the mineralization of dyes. First time we have reported that novel WO{sub 3} loaded Ag–ZnO has been found to be very efficient for two azo dyes removal when compared to commercially available catalyst (Degussa P25, ZnO (Merck) and TiO{sub 2} (Merck)). The mineralization of dyes has been confirmed by chemical oxygen demand (COD) measurements. A mechanism of degradation has been proposed for the higher efficiency of WO{sub 3}–Ag–ZnO.

  7. Electronic polarizability and interaction parameter of gadolinium tungsten borate glasses with high WO{sub 3} content

    SciTech Connect

    Taki, Yukina; Shinozaki, Kenji; Honma, Tsuyoshi; Dimitrov, Vesselin; Komatsu, Takayuki

    2014-12-15

    Glasses with the compositions of 25Gd{sub 2}O{sub 3}–xWO{sub 3}–(75−x)B{sub 2}O{sub 3} with x=25–65 were prepared by using a conventional melt quenching method, and their electronic polarizabilities, optical basicities Λ(n{sub o}), and interaction parameters A(n{sub o}) were estimated from density and refractive index measurements in order to clarify the feature of electronic polarizability and bonding states in the glasses with high WO{sub 3} contents. The optical basicity of the glasses increases monotonously with the substitution of WO{sub 3} for B{sub 2}O{sub 3}, and contrary the interaction parameter decreases monotonously with increasing WO{sub 3} content. A good linear correlation was observed between Λ(n{sub o}) and A(n{sub o}) and between the glass transition temperature and A(n{sub o}). It was proposed that Gd{sub 2}O{sub 3} oxide belongs to the category of basic oxide with a value of A(n{sub o})=0.044 Å{sup −3} as similar to WO{sub 3}. The relationship between the glass formation and electronic polarizability in the glasses was discussed, and it was proposed that the glasses with high WO{sub 3} and Gd{sub 2}O{sub 3} contents would be a floppy network system consisting of mainly basic oxides. - Graphical abstract: This figure shows the correlation between the optical basicity and interaction parameter in borate-based glasses. The data obtained in the present study for Gd{sub 2}O{sub 3}–WO{sub 3}–B{sub 2}O{sub 3} glasses are locating in the correlation line for other borate glasses. These results shown in Fig. 8 clearly demonstrate that Gd{sub 2}O{sub 3}–WO{sub 3}–B{sub 2}O{sub 3} glasses having a wide range of optical basicity and interaction parameter are regarded as glasses consisting of acidic and basic oxides. - Highlights: • Gd{sub 2}O{sub 3}–WO{sub 3}–B{sub 2}O{sub 3} glasses with high WO{sub 3} contents were prepared. • Electronic polarizability and interaction parameter were estimated. • Optical basicity increases

  8. Numerical model of the catchments of the oziąbel and wołczyński strumień rivers - Wołczyn municipality

    NASA Astrophysics Data System (ADS)

    Olichwer, Tomasz; Wcisło, Marek; Staśko, Stanisław; Buczyński, Sebastian; Modelska, Magdalena; Tarka, Robert

    2012-10-01

    The article presents a numerical model designed for determining groundwater dynamics and water balance of the catchments of the Oziąbel (Czarna Woda) river and the Wołczyński Strumień river in Wołczyn region. Hydrogeological mapping and modelling research covered the area of 238.9 km2. As a result of measurements performed in 2008-2009, flows were determined in major rivers and water table positions were measured at 26 points. In the major part of the area described, the water table, lying at the depth of 1.5-18.7 m, has unconfined character, and the aquifer is built of Neogene (Quaternary) sands and gravels. In the area under study, groundwaters are drawn from 6 wells with total withdrawal of 6133 m3/d. The numerical modelling was performed with the use of Visual Modflow 3.1.0 software. The area was partitioned by a discretization grid with a step size l = 250 m. The conceptual model of the hydrogeological system is based on hydrological data gathered over a period of one year, data from HYDRO bank database, cross-sections and maps. The boundaries of the modelled hydrogeological system were established on the watersheds of the Wołczyński Strumień river and the Oziąbel river, apart from the areas where they run together. The modelled area was extended (271.5 km2) around the Wołczyński Strumień river catchment to achieve a more effective mapping of the anthropogenic impact on its balance and the hydrodynamic system of the catchment area. The structure is characterised by the occurrence of one or rarely two aquifers separated by a pack of Quaternary clays. The investigation produced a detailed water balance and its components.

  9. Dopant-dependent reflectivity and refractive index of microcrystalline HxWO3 and LixWO3 bronze thin films.

    PubMed

    Hussain, Zahid

    2002-11-01

    Reflectivity spectra of HxWO3 and LiWO3 thin films were measured over the photon energy range from 0.4 to 4.2 eV. It was found that microcrystalline tungsten bronzes have reflectances of 8%-30% over the dopant concentration range x (0 < or = x < or = 0.25). Values for the real part of refractive index n were also determined from the refined reflectivity data. The optical data are interpreted by use of a modified Drude-Zener model together with a single-oscillator model to differentiate between bound and free electronic states. The values of high-frequency dielectric constant epsilon(hf) of MxWO3 (M = H+, Li+) bronzes were determined from the refractive-index data for estimation of the effective electronic masses involved in optical and polaronic transitions. A single-oscillator model showed that oscillator energy Ea and dispersion energy Ed increased and decreased, respectively, with increasing x values, opposite what occurs in crystalline tungsten bronzes. These findings support the fact that Bloch electrons are almost absent; instead, the polaronic species (W5+ and W4+) are assumed to control the reflectivity modifications (or variations in the refractive index) that are associated with the microcrystalline tungsten bronzes.

  10. Physical properties and surface/interface analysis of nanocrystalline WO3 films grown under variable oxygen gas flow rates

    SciTech Connect

    Vemuri, R. S.; Carbjal-Franco, G.; Ferrer, D. A.; Engelhard, Mark H.; Ramana, Chintalapalle V.

    2012-10-15

    Nanocrystalline WO3 films were grown by reactive magnetron sputter-deposition in a wide range of oxygen gas flow rates while keeping the deposition temperature fixed at 400 oC. The physical characteristics of WO3 films were evaluated using grazing incidence X-ray diffraction (GIXRD), X-ray reflectivity (XRR) and transmission electron microscopy (TEM) measurements. Physical characterization indicates that the thickness, grain size, and density of WO3 films are sensitive to the oxygen gas flow rate during deposition. XRD data indicates the formation of tetragonal WO3 films. The grain size increases from 21 to 25 nm with increasing oxygen gas flow rate to 65%, at which point the grain size exhibits a decreasing trend to attain the lowest value of 15 nm at 100% oxygen. TEM analysis provides a model consisting of isotropic WO3 film (nanocrystalline)-SiO2 interface (amorphous)-Si(100) substrate. XRR simulations, which are based on this model, provide excellent agreement to the experimental data indicating that the normalized thickness of WO3 films decreases with the increasing oxygen gas flow rate. The density of WO3 films increases with increasing oxygen gas flow rate.

  11. Reduced graphene oxide wrapped Bi2WO6 hybrid with ultrafast charge separation and improved photoelectrocatalytic performance

    NASA Astrophysics Data System (ADS)

    Wang, Huan; Liang, Yinghua; Liu, Li; Hu, Jinshan; Cui, Wenquan

    2017-01-01

    A reduced graphene oxide (rGO) wrapped Bi2WO6 (Bi2WO6@rGO) hybrid as photoelectrode for enhanced photoelectrocatalytic (PEC) degradation of organic pollutants is reported, which exhibited excellent charge separation and photoconversion efficiency. The core@shell structured Bi2WO6@rGO photoelectrode yielded a pronounced 1.56-fold and 23.8-fold photocurrent density at 1.0 V vs. saturated calomel electrode (SCE), than that of loading structured Bi2WO6-rGO and pure Bi2WO6. The Bi2WO6@rGO hybrid exhibited enhanced photoelectrocatalytic efficiency for degradation of Rhodamine B (RhB), which was 43.0% and 65.6% higher than that of photocatalytic (PC) and electrocatalytic (EC) processes, respectively. The enhancement in PEC degradation of RhB benefited from: (1) a strong interaction and a wide range of conjugation were formed in the core@shell system; (2) a 0.26 V of flat band potential was negatively shifted in case of Bi2WO6@rGO composite; (3) the photogenerated electrons and holes could be spatially separated by external electric potentials.

  12. Experimental and theoretical investigation of a mesoporous K(x)WO3 material having superior mechanical strength.

    PubMed

    Dey, Sonal; Anderson, Sean T; Mayanovic, Robert A; Sakidja, Ridwan; Landskron, Kai; Kokoszka, Berenika; Mandal, Manik; Wang, Zhongwu

    2016-02-07

    Mesoporous materials with tailored properties hold great promise for energy harvesting and industrial applications. We have synthesized a novel tungsten bronze mesoporous material (K(x)WO3; x ∼ 0.07) having inverse FDU-12 type pore symmetry and a crystalline framework. In situ small angle X-ray scattering (SAXS) measurements of the mesoporous K(0.07)WO3 show persistence of a highly ordered meso-scale pore structure to high pressure conditions (∼18.5 GPa) and a material with remarkable mechanical strength despite having ∼35% porosity. Pressure dependent in situ SAXS measurements reveal a bulk modulus κ = 44 ± 4 GPa for the mesoporous K(x)WO3 which is comparable to the corresponding value for the bulk monoclinic WO3 (γ-WO3). Evidence from middle angle (MAXS) and wide angle X-ray scattering (WAXS), high-resolution transmission electron microscopy (HR-TEM) and Raman spectroscopy shows that the presence of potassium leads to the formation of a K-bearing orthorhombic tungsten bronze (OTB) phase within a monoclinic WO3 host structure. Our ab initio molecular dynamics calculations show that the formation of the OTB phase provides superior strength to the mesoporous K(0.07)WO3.

  13. Improved WO3 photocatalytic efficiency using ZrO2 and Ru for the degradation of carbofuran and ampicillin.

    PubMed

    Gar Alalm, Mohamed; Ookawara, Shinichi; Fukushi, Daisuke; Sato, Akira; Tawfik, Ahmed

    2016-01-25

    The photocatalytic degradation of carbofuran (pesticide) and ampicillin (pharmaceutical) using synthesized WO3/ZrO2 nanoparticles under simulated solar light was investigated. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectra analyses were used to characterize the prepared catalysts. The optimum ratio of WO3 to ZrO2 was determined to be 1:1 for the degradation of both contaminants. The degradation of carbofuran and ampicillin by WO3/ZrO2 after 240 min of irradiation was 100% and 96%, respectively. Ruthenium (Ru) was employed as an additive to WO3/ZrO2 to enhance the photocatalytic degradation rate. Ru/WO3/ZrO2 exhibited faster degradation rates than WO3/ZrO2. Furthermore, 100% and 97% degradation of carbofuran and ampicillin, respectively, was achieved using Ru/WO3/ZrO2 after 180 min of irradiation. The durability of the catalyst was investigated by reusing the same suspended catalyst, which achieved 92% of its initial efficiency. The photocatalytic degradation of ampicillin and carbofuran followed pseudo-first order kinetics according to the Langmuir-Hinshelwood model.

  14. Effects of Nickel Doping on the Multiferroic and Magnetic Phases of MnWO 4

    DOE PAGES

    Poudel, N.; Lorenz, B.; Lv, B.; ...

    2015-12-15

    There are various orders in multiferroic materials with a frustrated spiral spin modulation inducing a ferroelectric state are extremely sensitive to small perturbations such as magnetic and electric fields, external pressure, or chemical substitutions. A classical multiferroic, the mineral Hubnerite with chemical formula MnWO4, shows three different magnetic phases at low temperature. The intermediate phase between 7.5K < T < 12.7K is multiferroic and ferroelectricity is induced by an inversion symmetry breaking spiral Mn-spin order and strong spin-lattice interactions. Furthermore, the substitution of Ni2+ (spin 1) for Mn2+ (spin 5/2) in MnWO4 and its effects on the magnetic and multiferroicmore » phases are studied. The ferroelectric phase is stabilized for low Ni content (up to 10%). Upon further Ni doping, the polarization in the ferroelectric phase is quickly suppressed while a collinear and commensurate magnetic phase, characteristic of the magnetic structure in NiWO4, appears first at higher temperature, gradually extends to lower temperature, and becomes the ground state above 30% doping. Between 10% and 30%, the multiferroic phase coexists with the collinear commensurate phase. In this concentration region, the spin spiral plane is close to the a-b plane which explains the drop of the ferroelectric polarization. Finally, the phase diagram of Mn1-xNixWO4 is derived by a combination of magnetic susceptibility, specific heat, electric polarization, and neutron scattering measurements.« less

  15. Formation and electrochemical characterization of anodic ZrO2-WO3 mixed oxide nanotubular arrays

    NASA Astrophysics Data System (ADS)

    Whitman, Stuart R.; Raja, Krishnan S.

    2014-06-01

    ZrO2-WO3 mixed oxide nanotubes were synthesized by a simple electrochemical anodization route. The oxide nanotubes contained a mixture of metastable hexagonal WO3 and monoclinic (and orthorhombic) ZrO2 phases, as well as a mixed-oxide ZrW2O8 phase that showed a metastable tetragonal symmetry. Evaluation of photo-activity of the materials showed generation of photo-potentials of -85 mV and -230 mV in the as-anodized and annealed conditions. Because of the mismatch in the band edge positions of the WO3 and ZrO2 phases and the resultant relaxation of photo-generated charge carriers, no significant photo-current density could be observed. The arrays of oxide nanotubes are considered for electrochemical capacitor application because of their morphology-assisted fast charge/discharge kinetics and large surface area. Presence of a large concentration of charge defects (on the order of 1021 cm-3) and the reported high proton conductivity of the ZrO2-WO3 mixed oxide rendered high capacitance, which decreased with an increase in the scan rate of cyclic voltammetry. The highest measured capacitance was 40.03 mF/cm2 at a scan rate of 10 mV/s and the lowest was 1.93 mF/cm2 at 1 V/s in 1 M sulfuric acid solution.

  16. Environmentally friendly aqueous solution synthesis of hierarchical CaWO4 microspheres at room temperature.

    PubMed

    Wang, Wenshou; Zhen, Liang; Xu, Chengyan; Zhang, Baoyou; Shao, Wenzhu

    2008-03-01

    An environmentally friendly route for the synthesis of hierarchical CaWO4 microspheres with novel morphology at room temperature has been successfully developed. CaCl2 and Na2WO4 were used as reaction regents, and distilled water was used as an environmentally friendly solvent. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence spectroscopy. This green wet-chemical route provides a simple, one-step, low-cost approach for the large-scale synthesis of hierarchical CaWO4 microspheres with relatively uniform diameters of 3-6 microm. The hierarchical microspheres are built up with numerous nanorods with an average diameter of 50 nm, which are radially oriented to the microsphere center. SEM observations of different intermediates indicate the possible growth process, in which the hierarchical structure growth is from nuclei through kayak-like, rod-like, peanut-like, dumbbell-like, and peach-like structures to final microspheres, via "self-assembled preferential end growth" of kayak-like particles in aqueous solution. The hierarchical CaWO4 microspheres exhibit a strong, broad blue emission peak of 412 nm.

  17. Composite WO3/TiO2 nanostructures for high electrochromic activity

    DOE PAGES

    Reyes-Gil, Karla R.; Stephens, Zachary D.; Stavila, Vitalie; ...

    2015-01-06

    A composite material consisting of TiO2 nanotubes (NT) with WO3 electrodeposited on its surface has been fabricated, detached from its Ti substrate, and attached to a fluorine-doped tin oxide (FTO) film on glass for application to electrochromic (EC) reactions. Several adhesion layers were tested, finding that a paste of TiO2 made from commercially available TiO2 nanoparticles creates an interface for the TiO2 NT film to attach to the FTO glass, which is conductive and does not cause solution-phase ions in an electrolyte to bind irreversibly with the material. The effect of NT length and WO3 concentration on the EC performancemore » were studied. As a result, the composite WO3/TiO2 nanostructures showed higher ion storage capacity, better stability, enhanced EC contrast, and longer memory time compared with the pure WO3 and TiO2 materials« less

  18. Enhanced photocatalytic activity in anodized WO3-loaded TiO2 nanotubes

    NASA Astrophysics Data System (ADS)

    Nazari, M.; Golestani-Fard, F.; Bayati, R.; Eftekhari-Yekta, B.

    2015-04-01

    In this work, TiO2 and WO3-grafted TiO2 nanotubes were grown via anodizing of titanium substrates in tungstate containing electrolytes. The samples were characterized in detail by XRD, XPS, SEM, EDX, and UV-Vis spectrophotometry techniques. Besides, photocatalytic characteristics were evaluated through measuring the degradation rate of 4-chlorophenol to establish a correlation between structure and photochemical properties. We were able to control morphology and growth mode of nanotubes from a tubular to a worm-like structure by changing the electrolyte composition. The samples possessed an anatase-rutile matrix where the anatase/rutile ratio was found to increase with the concentration of tungstate in the electrolyte. We attributed this observation to change in electrical conductivity of the electrolyte and the heat generated on the substrates. It was unambiguously revealed that a composite of WO3 and TiO2 forms and, in parallel, tungsten is doped into the crystalline lattice of TiO2. The maximum photocatalytic reaction rate constant for TiO2 and WO3-TiO2 samples was determined to be 0.0131 and 0.0174 min-1 respectively. The grafting TiO2 nanotubes with WO3 enhances the photocatalytic activity mainly due to the hindrance of charge carrier recombination and the formation of a more acidic surface. We established a correlation between structure, stoichiometry, and photocatalytic characteristics of nanotubes.

  19. Simple route to (NH4)(x)WO3 nanorods for near infrared absorption.

    PubMed

    Guo, Chongshen; Yin, Shu; Dong, Qiang; Sato, Tsugio

    2012-06-07

    Described here is how to synthesize one-dimensional ammonium tungsten bronze ((NH(4))(x)WO(3)) by a facile solvothermal approach in which ethylene glycol and acetic acid were employed as solvents and ammonium paratungstate was used as a starting material, as well as how to develop the near infrared absorption properties of (NH(4))(x)WO(3) nanorods for application as a solar light control filter. The as-obtained product was characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetry (TG), atomic force microscope (AFM) and UV-Vis-NIR spectra. The SEM and TEM images clearly revealed that the obtained sample possessed rod/fiber-like morphologies with diameters around 120 nm. As determined by UV-Vis-NIR optical measurement, the thin film consisted of (NH(4))(x)WO(3) nanoparticles, which can selectively transmit most visible lights, but strongly absorb the near-infrared (NIR) lights and ultraviolet rays. These interesting optical properties make the (NH(4))(x)WO(3) nanorods suitable for the solar control windows.

  20. Electrochemical Performance of Morphologically Different Bi2WO6 Nanostructures Synthesized via a Hydrothermal Route

    NASA Astrophysics Data System (ADS)

    Wang, Fei; Yang, Hua; Zhang, Haimin; Su, Junyan; Wang, Xiangxian

    2017-01-01

    Morphologically different Bi2WO6 nanostructures have been synthesized via a hydrothermal route, where the morphology was tailored by varying the pH value of the precursor solution. The samples prepared at pH 1, 7, and 11 consisted of flower-like hierarchical structures with average diameter of 7 μm, irregular flake-like structures with average thickness of 90 nm, and uniform spherical structures with average size of 85 nm, respectively. The electrochemical performance of the as-prepared Bi2WO6 samples was investigated by cyclic voltammetry, galvanostatic charge-discharge measurements, and electrochemical impedance spectroscopy. In 1 M KOH electrolyte at current density of 0.5 mA cm-2, the specific capacitance of the Bi2WO6 with flower-like hierarchical, flake-like, and spherical structure was measured to be 255 F g-1, 214 F g-1, and 412 F g-1, respectively. After 850 charge-discharge cycles at current density of 3 mA cm-2, the capacitance of the three samples remained at 87%, 78%, and 95% of the initial value, respectively. Among the three types of Bi2WO6 morphology, the spherical structure delivered the best electrochemical performance.

  1. Hydrothermal synthesis and NH3 gas sensing property of WO3 nanorods at low temperature

    NASA Astrophysics Data System (ADS)

    Dien Nguyen, Dac; Vuong Dang, Duc; Chien Nguyen, Duc

    2015-09-01

    One-dimensional self-assembled single-crystalline hexagonal tungsten trioxide (WO3) nanostructures were synthesized by wet chemical-assisted hydrothermal processing at 120 °C for 24 h using sodium tungstate and hydrochloric acid. Urchin-like hierarchical nanorods (petal size: ∼16 nm diameter and 110 nm length) were obtained. The samples were characterized by field emission scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy and x-ray diffraction. Sensors based on WO3 nanorods were fabricated by coating them on SiO2/Si substrate attached with Pt interdigitated electrodes. NH3 gas-sensing properties of WO3 nanorods were measured at different temperatures ranging from 50 °C to 350 °C and the response was evaluated as a function of ammonia gas concentration. The gas-sensing results reveal that WO3 nanorods sensor exhibits high sensitivity and selectivity to NH3 at low operating temperature (50 °C). The maximum response reached at 50 °C was 192 for 250 ppm NH3, with response and recovery times of 10 min and 2 min, respectively.

  2. Hydrothermal Synthesis and Ammonia Sensing Properties of WO3/Fe2O3 Nanorod Composites

    NASA Astrophysics Data System (ADS)

    Dien, Nguyen Dac; Phuoc, Luong Huu; Hien, Vu Xuan; Vuong, Dang Duc; Chien, Nguyen Duc

    2017-01-01

    WO3 nanorods (NRs) and α-Fe2O3 NRs were fabricated by hydrothermal treatment. Composites of these materials were created by mixing with ratios of 1:2, 1:1 and 2:1 in weight. Morphology, structure and composition characteristics of the WO3/Fe2O3 NRs composites were characterized by scanning electron microscopy, x-ray diffraction and energy dispersive x-ray spectroscopy analyses. The results of sensing measurements indicated that the sensor based on WO3:Fe2O3 with the ratio of 2:1 exhibited fairly good sensitivity toward NH3 at 300°C and the sensor based on WO3:Fe2O3 with the ratio of 1:1 can be used as a NH3 sensor with an operating temperature of 350°C. Selectivity and response-recovery times are suitable for practical applications. Finally, the mechanism for the improvement in the gas-sensing property was discussed.

  3. Electrochromism and photocatalysis in dendrite structured Ti:WO3 thin films grown by sputtering

    NASA Astrophysics Data System (ADS)

    Karuppasamy, A.

    2015-12-01

    Titanium doped tungsten oxide (Ti:WO3) thin films with dendrite surface structures were grown by co-sputtering titanium and tungsten in Ar + O2 atmosphere. Ti:WO3 thin films were deposited at oxygen flow rates corresponding to pressures in the range 1.0 × 10-3-5.0 × 10-3 mbar. Argon flow rate and sputtering power densities for titanium (2 W/cm2) and tungsten (3 W/cm2) were kept constant. Ti:WO3 films deposited at an oxygen pressure of 5 × 10-3 mbar are found to be better electrochromic and photocatalytic. They have high optical modulation (80% at λ = 550 nm), coloration efficiency (60 cm2/C at λ = 550 nm), electron/ion storage and removal capacity (Qc: -22.01 mC/cm2, Qa: 17.72 mC/cm2), reversibility (80%) and methylene blue decomposition rate (-1.38 μmol/l d). The combined effects of titanium doping, dendrite surface structures and porosity leads to significant enhancement in the electrochromic and photocatalytic properties of Ti:WO3 films.

  4. Characterization of MeWO 4 (Me = Ba, Sr and Ca) nanocrystallines prepared by sonochemical method

    NASA Astrophysics Data System (ADS)

    Thongtem, Titipun; Phuruangrat, Anukorn; Thongtem, Somchai

    2008-09-01

    Metal tungstates (MeWO 4, Me = Ba, Sr and Ca) were successfully prepared using the corresponding Me(NO 3) 2·2H 2O and Na 2WO 4·2H 2O in ethylene glycol by the 5 h sonochemical process. The tungstate phases with scheelite structure were detected with X-ray diffraction (XRD) and selected area electron diffraction (SAED). Their calculated lattice parameters are in accord with those of the JCPDS cards. Transmission electron microscopy (TEM) revealed the presence of nanoparticles composing the products. Their average sizes are 42.0 ± 10.4, 18.5 ± 5.1 and 13.1 ± 3.3 nm for Me = Ba, Sr and Ca, respectively. Interplanar spaces of the crystals were also characterized with high-resolution TEM (HRTEM). Their crystallographic planes are aligned in systematic array. Six different vibration wavenumbers were detected using Raman spectrometer and are specified as ν1(A g), ν3(B g), ν3(E g), ν4(B g), ν2(A g) and free rotation. Fourier transform infrared (FTIR) spectra provided the evidence of scheelite structure with W-O anti-symmetric stretching vibration of [WO 4] 2- tetrahedrons at 786-883 cm -1. Photoluminescence emission of the products was detected over the range of 384-416 nm.

  5. Lattice dynamics study of scheelite tungstates under high pressure I. BaWO4

    NASA Astrophysics Data System (ADS)

    Manjón, F. J.; Errandonea, D.; Garro, N.; Pellicer-Porres, J.; Rodríguez-Hernández, P.; Radescu, S.; López-Solano, J.; Mujica, A.; Muñoz, A.

    2006-10-01

    Room-temperature Raman scattering has been measured in barium tungstate (BaWO4) up to 16GPa . We report the pressure dependence of all the Raman active first-order phonons of the tetragonal scheelite phase ( BaWO4-I , space group I41/a ), which is stable at normal conditions. As pressure increases the Raman spectrum undergoes significant changes around 6.9GPa due to the onset of the structural phase transition to the monoclinic BaWO4-II phase (space group P21/n ). This transition is only completed above 9.5GPa . A further change in the spectrum is observed at 7.5GPa related to a scheelite-to-fergusonite transition. The scheelite, BaWO4-II , and fergusonite phases coexist up to 9.0GPa due to the sluggishness of the I→II phase transition. Further to the experimental study, we have performed ab initio lattice dynamics calculations that have greatly helped us in assigning and discussing the pressure behavior of the observed Raman modes of the three phases.

  6. Lattice dynamics study of scheelite tungstates under high pressure II. PbWO4

    NASA Astrophysics Data System (ADS)

    Manjon, F. J.; Errandonea, D.; Garro, N.; Pellicer-Porres, J.; López-Solano, J.; Rodríguez-Hernández, P.; Radescu, S.; Mujica, A.; Muñoz, A.

    2006-10-01

    Room-temperature Raman scattering has been measured in lead tungstate up to 17GPa . We report the pressure dependence of all the Raman modes of the tetragonal scheelite phase ( PbWO4-I or stolzite, space group I41/a ), which is stable at ambient conditions. Upon compression the Raman spectrum undergoes significant changes around 6.2GPa due to the onset of a partial structural phase transition to the monoclinic PbWO4-III phase (space group P21/n ). Further changes in the spectrum occur at 7.9GPa , related to a scheelite-to-fergusonite transition. This transition is observed due to the sluggishness and kinetic hindrance of the I→III transition. Consequently, we found the coexistence of the scheelite, PbWO4-III , and fergusonite phases from 7.9to9GPa , and of the last two phases up to 14.6GPa . We have performed ab initio lattice-dynamics calculations, which have greatly helped us in assigning the Raman modes of the three phases and discussing their pressure dependence. The Raman modes of the free WO4 molecule are discussed.

  7. NO{sub 2} gas sensing of flame-made Pt-loaded WO{sub 3} thick films

    SciTech Connect

    Samerjai, Thanittha; Tamaekong, Nittaya; Liewhiran, Chaikarn; Wisitsoraat, Anurat; Phanichphant, Sukon

    2014-06-01

    Unloaded WO{sub 3} and 0.25–1.0 wt% Pt-loaded WO{sub 3} nanoparticles for NO{sub 2} gas detection were synthesized by flame spray pyrolysis (FSP) and characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The BET surface area (SSA{sub BET}) of the nanoparticles was measured by nitrogen adsorption. The NO{sub 2} sensing properties of the sensors based on unloaded and Pt-loaded WO{sub 3} nanoparticles were investigated. The results showed that the gas sensing properties of the Pt-loaded WO{sub 3} sensors were excellent to those of the unloaded one. Especially, 0.25 wt% Pt-loaded WO{sub 3} sensor showed highest response to NO{sub 2} than the others at low operating temperature of 150 °C. - Graphical abstract: The response of 0.25 wt% Pt-loaded WO3 sensor was 637 towards NO{sub 2} concentration of 10 ppm at 150 °C. - Highlights: • Unloaded and Pt-loaded WO{sub 3} nanoparticles for NO{sub 2} gas detection were synthesized by flame spray pyrolysis (FSP). • Gas sensing properties of the Pt-loaded WO{sub 3} sensors were excellent to those of the unloaded one. • 0.25 wt% Pt-loaded WO{sub 3} sensor showed highest response to NO{sub 2} at low operating temperature of 150 °C.

  8. Solar photocatalytic activity of TiO2 modified with WO3 on the degradation of an organophosphorus pesticide.

    PubMed

    Ramos-Delgado, N A; Gracia-Pinilla, M A; Maya-Treviño, L; Hinojosa-Reyes, L; Guzman-Mar, J L; Hernández-Ramírez, A

    2013-12-15

    In this study, the solar photocatalytic activity (SPA) of WO3/TiO2 photocatalysts synthesized by the sol-gel method with two different percentages of WO3 (2 and 5%wt) was evaluated using malathion as a model contaminant. For comparative purpose bare TiO2 was also prepared by sol-gel process. The powders were characterized by X-ray diffraction (XRD), Raman spectroscopy, diffuse reflectance UV-vis spectroscopy (DRUV-vis), specific surface area by the BET method (SSABET), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy with a high annular angle dark field detector (STEM-HAADF). The XRD, Raman, HRTEM and STEM-HAADF analyses indicated that WO3 was present as a monoclinic crystalline phase with nanometric cluster sizes (1.1 ± 0.1 nm for 2% WO3/TiO2 and 1.35 ± 0.3 nm for 5% WO3/TiO2) and uniformly dispersed on the surface of TiO2. The particle size of the materials was 19.4 ± 3.3 nm and 25.6 ± 3 nm for 2% and 5% WO3/TiO2, respectively. The SPA was evaluated on the degradation of commercial malathion pesticide using natural solar light. The 2% WO3/TiO2 photocatalyst exhibited the best photocatalytic activity achieving 76% of total organic carbon (TOC) abatement after 300 min compared to the 5% WO3/TiO2 and bare TiO2 photocatalysts, which achieved 28 and 47% mineralization, respectively. Finally, experiments were performed to assess 2% WO3/TiO2 catalyst activity on repeated uses; after several successive cycles its photocatalytic activity was retained showing long-term stability.

  9. Synthesis of carbon doped WO3·0.33H2O hierarchical photocatalyst with improved photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Zheng, Yi; Chen, Gang; Yu, Yaoguang; Zhou, Yansong; He, Fang

    2016-01-01

    A carbon doping method is developed to overcome the drawback of conventional carbon doping method. The carbon dopant is synthesized by treating carbon with dilute nitric acid through hydrothermal process. Carbon-doped WO3·0.33H2O (Csbnd WO3·0.33H2O) is obtained by adding the carbon dopant solution, and then through an additional hydrothermal process. Based on XRD, Raman and XPS, carbon have been incorporated into the interstitial position of WO3·0.33H2O unit cell rather than substitution of oxygen in lattice of WO3·0.33H2O, which induces distortion of WO6 octahedron and lattice defect. In addition, carbon doping also induces the emergence of new level above the valence band. The new level increases the migration pathway of photo-generated carriers, which reduces the recombination rate of photo-generated carriers. The changes of band structure, distortion of WO6 octahedron and lattice defect are beneficial to improve the photocatalytic performance of WO3·0.33H2O. Compared with pristine WO3·0.33H2O, Csbnd WO3·0.33H2O display better photocatalytic performance on degradation of rhodamine B (RhB), which include the faster de-ethylation process and cycloreversion process. Moreover, the experiments of radical quenchers confirmed that the h+ display the main influence on degradation of RhB. This study implies that carbon can be doped into some metal oxide hydrates through a mild preparation process, which provides a possible way for the synthesis of carbon doped thermal unstable materials.

  10. High photocatalytic performance of BiOI/Bi2WO6 toward toluene and Reactive Brilliant Red

    NASA Astrophysics Data System (ADS)

    Li, Huiquan; Cui, Yumin; Hong, Wenshan

    2013-01-01

    BiOI sensitized nano-Bi2WO6 photocatalysts with different BiOI contents were successfully synthesized by a facile deposition method at room temperature, and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) high-resolution transmission electron microscopy (HR-TEM), photoluminescence (PL) spectra, UV-vis diffuse reflection spectroscopy (UV-vis DRS) and Brunauer-Emmett-Teller (BET) surface area measurements. The photocatalytic activity of BiOI/Bi2WO6 was evaluated by the photo-degradation of Reactive Brilliant Red (X-3B) in suspended solution and toluene in gas phase. It has been shown that the BiOI/Bi2WO6 catalysts exhibit a coexistence of both tetragonal BiOI and orthorhombic Bi2WO6 phases. With increasing BiOI content, the absorption intensity of BiOI/Bi2WO6 catalysts increases in the 380-600 nm region and the absorption edge shifts significantly to longer wavelengths as compared to pure Bi2WO6. The 13.2% BiOI/Bi2WO6 catalyst exhibits obviously higher UV and visible light photocatalytic activities than commercial P25, pure Bi2WO6 and BiOI, for the photodegradation of toluene and X-3B. The remarkably enhanced photocatalytic activities can be attributed to the fact that the proper BiOI sensitized nano-Bi2WO6 increase its BET surface area, decrease band-gap energy, enhance absorption in the 380-600 nm region and inhibit the recombination of photo-induced carriers.

  11. Observation on long afterglow of Tb{sup 3+} in CaWO{sub 4}

    SciTech Connect

    Wu, Haoyi; Hu, Yihua; Kang, Fengwen; Chen, Li; Wang, Xiaojuan; Ju, Guifang; Mu, Zhongfei

    2011-12-15

    Graphical abstract: The afterglow of Tb{sup 3+} is observed in CaWO{sub 4} matrix. The main emission of the afterglow is ascribed to the {sup 5}D{sub 4} {yields} {sup 7}F{sub 5} and {sup 5}D{sub 4} {yields} {sup 7}F{sub 6}. Emission due to {sup 5}D{sub 3} {yields} {sup 7}F{sub 4} and {sup 5}D{sub 3} {yields} {sup 7}F{sub 5} is weak. The cross-relaxation dominate the afterglow emission and it enhances the transition from {sup 5}D{sub 4} whereas from {sup 5}D{sub 3}. Highlights: Black-Right-Pointing-Pointer A green long afterglow is observed from Tb{sup 3+} in CaWO{sub 4} matrix. Black-Right-Pointing-Pointer Two traps which may have a strong influence on the afterglow properties are revealed by TL. Black-Right-Pointing-Pointer A mechanism model based on energy transfer from WO{sub 4}{sup 2-} group to Tb{sup 3+} followed by cross-relaxation is proposed. -- Abstract: The Tb{sup 3+} doped CaWO{sub 4} phosphors are synthesized via high temperature solid state reaction. The X-ray diffraction shows that small amount of Tb{sup 3+} does not have a significant influence on the structure of CaWO{sub 4}. A broad absorption band of the WO{sub 4}{sup 2-} group is observed from photoluminescence and the energy transfer from WO{sub 4}{sup 2-} group to Tb{sup 3+} ions induces the f-f transition. The cross-relaxation between two adjacent Tb{sup 3+} ions weakens {sup 5}D{sub 3}-{sup 7}F{sub j} transitions and enhances the {sup 5}D{sub 4}-{sup 7}F{sub j} transitions, leading to a green long afterglow of the phosphors. The thermoluminescence curves centered around 75 Degree-Sign C reveal the trap depth for afterglow generation is about 0.74-0.77 eV. The optimum Tb{sup 3+} concentration for afterglow properties is about 1%. A deep hole trap is induced when Tb{sup 3+} concentration exceeds 1% and it suppresses the thermoluminescence and the decay properties.

  12. The assemblage WO2 + H2O as a steady-state hydrogen source in moderately reduced hydrothermal experiments

    USGS Publications Warehouse

    Cygan, G.L.; I-Ming, Chou

    1990-01-01

    The values of fH2 for the assemblage WO2 + WO2.72 + H2O (designated as WO) have been measured in sealed Au capsules under an external pressure of 2 kbar CH4 and between 650 and 800??C using Ag-AgBr-HBr sensors of fH2. The fH2 values obtained can be represented by the equation log(fWOH2)2kbar,T(??0.06) = (-1924.9 ??(T,K) + 4.06 and are found to be slightly greater than those associated with the previously calibrated C-CH4 buffer. -from Authors

  13. On the low-lying states of WO - A comparison with CrO and MoO

    NASA Technical Reports Server (NTRS)

    Nelin, C. J.; Bauschlicher, C. W., Jr.

    1985-01-01

    The four low-lying states of WO were investigated and compared with similar states of CrO and MoO. For all these systems the ground state is 5 Pi, but the ordering of the upper states is different between WO and either CrO or MoO. The difference in the state ordering arises in part from the fact that in WO all of the states are formed from W(+) in a d4S1 configuration, whereas in both CrO and MoO some states are formed from the d5 configuration and others from the d4S1 configuration.

  14. Temperature dependent x-ray diffraction study of lightly doped Na{sub x}WO{sub 3}

    SciTech Connect

    Paul, Sanhita; Mukherjee, G. D.; Ghosh, Anirudha; Raj, Satyabrata; Oishi, S.

    2011-03-21

    Temperature dependent x-ray diffraction studies have been carried out on nonstoichiometric lightly doped sodium tungsten bronze (Na{sub x}WO{sub 3} for x=0.025). The investigation reveals a structural modification around 230 K. Although the high and low temperature phases are monoclinic but at low temperature the corner sharing WO{sub 6} octahedra get significantly distorted due to displacement of tungsten and oxygen atoms from its mean position. This structural modification induces polaron formation in Na{sub 0.025}WO{sub 3} below 230 K.

  15. Theory of the Color Change of NaxWO3 as a Function of Na-Charge Doping

    SciTech Connect

    Xue, Y.; Zhang, Y.; Zhang, P.

    2009-01-01

    We report theoretical investigations of the coloration of WO{sub 3} upon charge insertion using sodium tungsten bronze (Na{sub x}WO{sub 3}) as a model system. Our results explain well the systematic color change of Na{sub x}WO{sub 3} from dark blue to violet, red-orange, and finally to golden yellow as sodium concentration x increases from 0.3 to unity. Proper accounts for both the interband and the intraband contributions to the optical response are found to be very important for a detailed understanding of the coloration mechanism in this system.

  16. Unprecedented Dawson isomerism induced by a central [WO5] and four 45°-rotated belt square pyramids.

    PubMed

    Xu, Xin; Dong, Huan-Li; Sang, Rui-Li; Xu, Li

    2012-12-28

    The seventh type of Wells-Dawson isomer, δ-[(WO(5))W(17)Cu(H(2)O)O(55)](10-) (1a) was obtained as a consequence of the formation of the first central square-pyramidal [WO(5)] moiety that results in a 45° rotation of the four belt [CuO(5)]/[WO(5)] square pyramids, establishing a new type of WD isomerism involving the rotation of the belt polyhedra, that were previously believed to stay unchanged.

  17. Polymorphism in Strontium Tungstate SrWO4 under Quasi-Hydrostatic Compression.

    PubMed

    Santamaria-Perez, David; Errandonea, Daniel; Rodriguez-Hernandez, Placida; Muñoz, Alfonso; Lacomba-Perales, Raul; Polian, Alain; Meng, Yue

    2016-10-03

    The structural and vibrational properties of SrWO4 have been studied experimentally up to 27 and 46 GPa, respectively, by angle-dispersive synchrotron X-ray diffraction and Raman spectroscopy measurements as well as using ab initio calculations. The existence of four polymorphs upon quasi-hydrostatic compression is reported. The three phase transitions were found at 11.5, 19.0, and 39.5 GPa. The ambient-pressure SrWO4 tetragonal scheelite-type structure (S.G. I41/a) undergoes a transition to a monoclinic fergusonite-type structure (S.G. I2/a) at 11.5 GPa with a 1.5% volume decrease. Subsequently, at 19.0 GPa, another structural transformation takes place. Our calculations indicate two possible post-fergusonite phases, one monoclinic and the other orthorhombic. In the diffraction experiments, we observed the theoretically predicted monoclinic LaTaO4-type phase coexisting with the fergusonite-type phase up to 27 GPa. The coexistence of the two phases and the large volume collapse at the transition confirm a kinetic hindrance typical of first-order phase transitions. Significant changes in Raman spectra suggest a third pressure-induced transition at 39.5 GPa. The conclusions extracted from the experiments are complemented and supported by ab initio calculations. Our data provides insight into the structural mechanism of the first transition, with the formation of two additional W-O contacts. The fergusonite-type phase can be therefore considered as a structural bridge between the scheelite structure, composed of [WO4] tetrahedra, and the new higher pressure phases, which contain [WO6] octahedra. All the observed phases are compatible with the high-pressure structural systematics predicted for ABO4 compounds using crystal-chemistry arguments such as the diagram proposed by Bastide.

  18. WoSIS: providing standardised soil profile data for the world

    NASA Astrophysics Data System (ADS)

    Batjes, Niels H.; Ribeiro, Eloi; van Oostrum, Ad; Leenaars, Johan; Hengl, Tom; Mendes de Jesus, Jorge

    2017-01-01

    The aim of the World Soil Information Service (WoSIS) is to serve quality-assessed, georeferenced soil data (point, polygon, and grid) to the international community upon their standardisation and harmonisation. So far, the focus has been on developing procedures for legacy point data with special attention to the selection of soil analytical and physical properties considered in the GlobalSoilMap specifications (e.g. organic carbon, soil pH, soil texture (sand, silt, and clay), coarse fragments ( < 2 mm), cation exchange capacity, electrical conductivity, bulk density, and water holding capacity). Profile data managed in WoSIS were contributed by a wide range of soil data providers; the data have been described, sampled, and analysed according to methods and standards in use in the originating countries. Hence, special attention was paid to measures for soil data quality and the standardisation of soil property definitions, soil property values, and soil analytical method descriptions. At the time of writing, the full WoSIS database contained some 118 400 unique shared soil profiles, of which some 96 000 are georeferenced within defined limits. In total, this corresponds with over 31 million soil records, of which some 20 % have so far been quality-assessed and standardised using the sequential procedure discussed in this paper. The number of measured data for each property varies between profiles and with depth, generally depending on the purpose of the initial studies. Overall, the data lineage strongly determined which data could be standardised with acceptable confidence in accord with WoSIS procedures, corresponding to over 4 million records for 94 441 profiles. The publicly available data - WoSIS snapshot of July 2016 - are persistently accessible from ISRIC WDC-Soils through doi:10.17027/isric-wdcsoils.20160003.

  19. Physical properties of rf magnetron sputter deposited NiO:WO3 thin films

    NASA Astrophysics Data System (ADS)

    Usha, K. S.; Sivakumar, R.; Sanjeeviraja, C.; Ichimura, M.

    2015-01-01

    The present study describes various physical properties of mixed nickel-tungsten oxide (NiO:WO3) (95:5) thin films prepared on glass substrate by rf magnetron sputtering due to the variation in rf power (100, 150, and 200 W). X-ray diffraction study shows that all the deposited films are amorphous in nature. The maximum transmittance of 97% in the infrared region was observed for the film deposited at 100 W rf power. A systematic reduction in the optical band gap is observed with increasing rf power, which is associated with the rf power induced effect leading to the production of localized states near the band edges of NiO:WO3. The Urbach energy (EU) value was found to increase with rf power, which may be due to the increased defects in the NiO matrix. From the optical study, we have evaluated various parameters such as refractive index, packing density, lattice dielectric constant, ratio between free carrier density and free carrier effective mass, plasma frequency, and dispersion energy parameters, etc. These results are discussed and correlated well with the light of possible mechanisms underlying the phenomena. The compositional purity of the film was confirmed by energy dispersive x-ray analysis (EDAX) and Auger electron spectroscopic (AES) measurements. The Raman spectra of NiO:WO3 films show two peaks corresponding to one-phonon LO mode at 560 cm-1 and two-phonon LO mode at 1100 cm-1 due to the vibrations of Ni-O bonds and a strong peak at 860 cm-1 corresponds to the stretching vibration of W-O pair in the WO6 group. The band edge emission at 369 nm was observed in photoluminescence spectra.

  20. Apical and basolateral transferrin receptors in polarized BeWo cells recycle through separate endosomes

    PubMed Central

    1991-01-01

    Contrary to most other epithelia, trophoblasts in the human placenta, which form the physical barrier between the fetal and the maternal blood circulation, express high numbers of transferrin receptors on their apical cell surface. This study describes the establishment of a polarized trophoblast-like cell line BeWo, which exhibit a high expression of transferrin receptors on the apex of the cells. Cultured on permeable filter supports, BeWo cells formed a polarized monolayer with microvilli on their apical cell surface. Across the monolayer a transepithelial resistance developed of approximately 600 omega.cm2 within 4 d. Depletion of Ca2+ from the medium decreased the resistance to background levels, showing its dependence on the integrity of tight junctions. Within the same period of time the secretion of proteins became polarized. In addition, the compositions of integral membrane proteins at the apical and basolateral plasma membrane domains were distinct as determined by domain-selective iodination. Similar to placental trophoblasts, binding of 125I-labeled transferrin to BeWo monolayers revealed that the transferrin receptor was expressed at both plasma membrane domains. Apical and basolateral transferrin receptors were found in a 1:2 surface ratio and exhibited identical dissociation constants and molecular weights. After uptake, transferrin recycled predominantly to the domain of administration, indicating separate recycling pathways from the apical and basolateral domain. This was confirmed by using diaminobenzidine cytochemistry, a technique by which colocalization of endocytosed 125I-labeled and HRP-conjugated transferrin can be monitored. No mixing of the two types of ligands was observed, when both ligands were simultaneously internalized for 10 or 60 min from opposite domains, demonstrating that BeWo cells possess separate populations of apical and basolateral early endosomes. In conclusion, the trophoblast-like BeWo cell line can serve as a unique

  1. Electrochemical and electrochromic properties of layer-by-layer films from WO(3) and chitosan.

    PubMed

    Huguenin, Fritz; Gonzalez, Ernesto R; Oliveira, Osvaldo N

    2005-07-07

    The design of improved materials for electrochromic applications now involves extensive use of novel composites, thus requiring an investigation of the mechanisms responsible for electrochromism in these structures. Using films of WO(3) and chitosan produced with the layer-by-layer (LBL) technique, we demonstrate that characteristics such as the number of electrochemical active sites (K), the molar absorption coefficient (epsilon), and the electrochromic efficiency (eta) can be obtained using the quadratic logistic equation (QLE). The complexation ability between chitosan and WO(3) allowed the growth of visually uniform multilayers of the composite, with the same amount of material adsorbed in each deposition cycle. By fitting the absorbance changes (DeltaA) resulting from the electronic intervalence transfer from W(V) to W(VI) sites in four-bilayer LBL films of WO(3)/chitosan and WO(3)/chitosan with ethanol in the precursor dispersion, K was estimated to be ca. 5.5 x 10(-8) mol cm(-2) and 3.6 x 10(-8) mol cm(-2), respectively. The molar absorption coefficient and electrochromic efficiency vary with the charge injected because of the saturation of W(V) sites and the dissipation and feedback effects implicit in the QLE associated with ion-network interactions, such as the proton trapping effect. The LBL film of WO(3)/chitosan showed a smaller molar absorption coefficient and electrochromic efficiency than that containing ethanol because of a greater proton trapping effect for the LBL film with no ethanol. This enhanced trapping effect was seen as a decrease in the electronic flux involved in intervalence transfer in electrochemical impedance spectroscopy experiments.

  2. Preparation of ultra-thin and high-quality WO3 compact layers and comparision of WO3 and TiO2 compact layer thickness in planar perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Zhang, Jincheng; Shi, Chengwu; Chen, Junjun; Wang, Yanqing; Li, Mingqian

    2016-06-01

    In this paper, the ultra-thin and high-quality WO3 compact layers were successfully prepared by spin-coating-pyrolysis method using the tungsten isopropoxide solution in isopropanol. The influence of WO3 and TiO2 compact layer thickness on the photovoltaic performance of planar perovskite solar cells was systematically compared, and the interface charge transfer and recombination in planar perovskite solar cells with TiO2 compact layer was analyzed by electrochemical impedance spectroscopy. The results revealed that the optimum thickness of WO3 and TiO2 compact layer was 15 nm and 60 nm. The planar perovskite solar cell with 15 nm WO3 compact layer gave a 9.69% average and 10.14% maximum photoelectric conversion efficiency, whereas the planar perovskite solar cell with 60 nm TiO2 compact layer achieved a 11.79% average and 12.64% maximum photoelectric conversion efficiency.

  3. Size- and shape-controlled conversion of tungstate-based inorganic-organic hybrid belts to WO3 nanoplates with high specific surface areas.

    PubMed

    Chen, Deliang; Gao, Lian; Yasumori, Atsuo; Kuroda, Kazuyuki; Sugahara, Yoshiyuki

    2008-10-01

    Two-dimensional monoclinic WO(3) nanoplates with high specific surface areas are synthesized through a novel conversion process using tungstate-based inorganic-organic hybrid micro/nanobelts as precursors. The process developed involves a topochemical transformation of tungstate-based inorganic-organic hybrid belts into WO(3) nanoplates via an intermediate product of H(2)WO(4) nanoplates, utilizing the similarity of the W-O octahedral layers in both H(2)WO(4) and WO(3). The as-obtained WO(3) nanoplates show a single-crystalline nanostructure with the smallest side along the [001] direction. The WO(3) nanoplates are 200-500 nm x 200-500 nm x 10-30 nm in size, and their specific surface areas are up to 180 m(2) g(-1). Photocatalytic measurements of visible-light-driven oxidation of water for O(2) generation in the presence of Ag(+) ions indicate that the activity of the as-obtained WO(3) nanoplates is one order of magnitude higher than that of commercially available WO(3) powders.

  4. Dehydration, Dehydrogenation, and Condensation of Alcohols on Supported Oxide Catalysts Based on Cyclic (WO3)3 and (MoO3)3 Clusters

    SciTech Connect

    Rousseau, Roger J.; Dixon, David A.; Kay, Bruce D.; Dohnalek, Zdenek

    2014-01-01

    Supported early transition metal oxides have important applications in numerous catalytic reactions. In this article we review preparation and activity of well-defined model WO3 and MoO3 catalysts prepared via deposition of cyclic gas-phase (WO3)3 and (MoO3)3 clusters generated by sublimation of WO3 and MoO3 powders. Conversion of small aliphatic alcohols to alkenes, aldehydes/ketons, and ethers is employed to probe the structure-activity relationships on model WO3 and MoO3 catalysts ranging from unsupported (WO3)3 and (MoO3)3 clusters embedded in alcohol matrices, to (WO3)3 clusters supported on surfaces of other oxides, and epitaxial and nanoporous WO3 films. Detailed theoretical calculations reveal the underlying reaction mechanisms and provide insight into the origin of the differences in the WO3 and MoO3 reactivity. For the range of interrogated (WO3)3 they further shed light into the role structure and binding of (WO3)3 clusters with the support play in determining their catalytic activity.

  5. Forskolin-induced differentiation of BeWo cells stimulates increased tumor growth in the chorioallantoic membrane (CAM) of the turkey (Meleagris gallopavo) egg.

    PubMed

    Schneider, Ralf; Borges, Marcus; Kadyrov, Mamed

    2011-05-01

    Invasiveness of BeWo cells has been assessed in a variety of assay systems including matrigel and mouse. At the same time BeWo cells are mostly used as model system for trophoblast fusion. Here we aimed to test the properties of BeWo cells in a combined approach. We forced BeWo cells to differentiate by culturing the cells in the presence of forskolin and then used these cells for invasion assays on the chorioallantoic membrane (CAM) of the turkey. The chorioallantoic membranes of turkey eggs were incubated with medium containing forskolin, BeWo cells cultured in medium alone, BeWo cells cultured in forskolin and washed, and BeWo cells cultured in forskolin and used directly for application. Suspensions were applied onto ten CAM per condition. For local tumor formation eggs were checked for tumor development every 24h macroscopically for up to 12 days and immunohistochemistry for cytokeratin 18 and Ki-67 were used for further analysis. Forskolin alone did not have any deleterious effect on the CAM. When the CAM was incubated with BeWo cells cultured in medium 40% of the eggs developed a macroscopically visible tumor. BeWo cells stimulated with forskolin and washed induced tumor growth in 50% of the eggs, while forskolin stimulated BeWo cells applied directly onto the CAM induced tumor growth in 70% of the eggs. Forced differentiation of BeWo cells by forskolin may lead to syncytial fusion in a plastic culture dish. Under the conditions used here, i.e. in direct contact to a living tissue, forskolin-induced differentiation of BeWo cells leads to an increase in tumor formation in the CAM. Thus BeWo cells may use signaling pathways to decide for both differentiation pathways similar to primary trophoblast depending on the environment.

  6. Advancing the Chemistry of CuWO4 for Photoelectrochemical Water Oxidation.

    PubMed

    Lhermitte, Charles R; Bartlett, Bart M

    2016-06-21

    Photoelectrochemical (PEC) cells are an ongoing area of exploration that provide a means of converting solar energy into a storable chemical form (molecular bonds). In particular, using PEC cells to drive the water splitting reaction to obtain H2 could provide a clean and sustainable route to convert solar energy into chemical fuels. Since the discovery of catalytic water splitting on TiO2 photoelectrodes by Fujishima and Honda, significant efforts have been directed toward developing high efficiency metal oxides to use as photocatalysts for this reaction. Improving the efficiency of PEC cells requires developing chemically stable, and highly catalytic anodes for the oxygen-evolution reaction (OER). This water oxidation half reaction requires four protons and four electrons coupling in two bond making steps to form O2, which limits the rate. Our group has accelerated efforts in CuWO4 as a candidate for PEC OER chemistry. Its small band gap of 2.3 eV allows for using visible light to drive OER, and the reaction proceeds with a high degree of chemoselectivity, even in the presence of more kinetically accessible anions such as chloride, which is common to seawater. Furthermore, CuWO4 is a chemically robust material when subjected to the highly oxidizing conditions of PEC OER. The next steps for accelerating research using this (and other), ternary phase oxides, is to move beyond reporting the basic PEC measurements to understanding fundamental chemical reaction mechanisms operative during OER on semiconductor surfaces. In this Account, we outline the process for PEC OER on CuWO4 thin films with emphasis on the chemistry of this reaction, the reaction rate and selectivity (determined by controlled-potential coulometry and oxygen-detection experiments). We discuss key challenges with CuWO4 such as slow kinetics and the presence of an OER-mediating mid-gap state, probed by electrochemical impedance spectroscopy. We propose that this mid-gap state imparts the observed

  7. One-dimensional Z-scheme TiO2/WO3/Pt heterostructures for enhanced hydrogen generation

    NASA Astrophysics Data System (ADS)

    Gao, Hongqing; Zhang, Peng; Hu, Junhua; Pan, Jimin; Fan, Jiajie; Shao, Guosheng

    2017-01-01

    One-dimensional Z-scheme TiO2/WO3/Pt heterostructures were fabricated by integrating a facile electrospinning technique and subsequent annealing in air. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy, were used to characterize the as-fabricated samples. The results showed that the H2-generation of the as-fabricated one-dimensional Z-scheme TiO2/WO3/Pt heterostructures (S2) was greatly enhanced compared with pure TiO2 nanofibers (S0) and TiO2/WO3 nanofibers (S1). The enhanced photocatalyst activities were mainly attributed to the solid-state Z-scheme photosynthetic heterojunction system with Pt nanoparticle as an electron collector and WO3 as a hole collector, leading to effective charge separation on these semiconductors, which were evidenced by electrochemical impedance spectroscopy (EIS) and photocurrent analysis.

  8. Electrosprayed heterojunction WO3/BiVO4 films with nanotextured pillar structure for enhanced photoelectrochemical water splitting

    NASA Astrophysics Data System (ADS)

    Mali, Mukund G.; Yoon, Hyun; Kim, Min-woo; Swihart, Mark T.; Al-Deyab, Salem S.; Yoon, Sam S.

    2015-04-01

    We demonstrate that the addition of a tungsten oxide (WO3) layer beneath a bismuth vanadate (BiVO4) photocatalyst layer with a nanotextured pillar morphology significantly increases the photocurrent density in photoelectrochemical water splitting. The WO3-BiVO4 bilayer films produced a photocurrent of up to 3.3 mA/cm2 under illumination at 100 mW/cm2 (AM1.5 spectrum). The bilayer film was characterized by scanning electron microscopy, X-ray diffraction, and photoelectrochemical methods, which confirmed the superiority of the bilayer film in terms of its morphology and charge separation and transport ability. Both WO3 and BiVO4 were deposited by electrostatic spraying under open-air conditions, which resulted in nanotextured pillars of BiVO4 atop a smooth WO3 film. The optimal coating conditions are also reported.

  9. Effect of Oral Administration of Tungsten Trioxide (WO3) Particles on Hispathological Feature of liver and kidney in Rat

    NASA Astrophysics Data System (ADS)

    Munawaroh, H. S. H.; Nandiyanto, A. B. D.; Gumilar, G. G.; Widi, A.; Subangkit, M.

    2017-03-01

    This study aims to investigate the toxicity and histopathology of tungsten trioxide (WO3) administration on rat’s liver and kidney. The LD50 of WO3 was determined and the sub acute toxicity was evaluated by orally administration of 5000 mg kg-1 of WO3 to rat for 14 consecutive days. Parameter of blood cells, ALT, creatinine, and BUN were experimentally measured. The toxicological evaluation showed that WO3 is a non toxic compound with the LD50 higher that 5000 mg kg-1. No biochemical change was observed for creatinine and Blood Urea Nitrogen parameter. In contrast, ALT parameter shows higher value in the experiment than that in the control group. Histopathological changes on rat’s liver and kidney were also studied. Small defects in rat’s liver and kidney were found, which may interfere the functional of related enzymes.

  10. Degradation of 4-chlorophenol in TiO2, WO3, SnO2, TiO2/WO3 and TiO2/SnO2 systems.

    PubMed

    Lin, Cheng-Fang; Wu, Chung-Hsin; Onn, Zong-Nan

    2008-06-15

    The present study was undertaken to evaluate the degradation performance of 4-chlorophenol (4-CP) using TiO2/WO3 and TiO2/SnO2 systems. A BET surface area analyzer, UV-vis spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron spectroscopy for chemical analysis (ESCA) were employed to characterize the photocatalyst. The band edge wavelength increased to 475 nm and gap energy decreased to 2.61 eV in the TiO2/WO3 system as compare to the single TiO2. Although the specific surfaces area of TiO2/WO3 decreases due to its larger size as compared to either TiO2 or WO3, the 4-CP degradation efficiency significantly increased as compared to single TiO2 or WO3 system at 435 nm wavelength. The TiO2/WO3 degradation of 4-CP at 369 nm was in fact inhibited. For TiO2/SnO2, the degradation efficiency also suffered at 369 nm, and only slightly increased compared to otherwise hardly 4-CP degraded in single TiO2 or SnO2 system. Since there is a significant accumulation of byproducts, the buildup of these intermediates on the catalyst surface may be responsible for their poor performance.

  11. Gal-1 silenced trophoblast tumor cells (BeWo) show decreased syncytium formation and different miRNA production compared to non-target silenced BeWo cells

    PubMed Central

    Hutter, Stefan; Morales-Prieto, Diana M.; Andergassen, Ulrich; Tschakert, Lisa; Kuhn, Christina; Hofmann, Simone; Markert, Udo R.; Jeschke, Udo

    2016-01-01

    ABSTRACT Galectin-1 (gal-1), a member of the mammalian β-galactoside-binding proteins, exerts biological effects by recognition of glycan ligands, including those involved in cell adhesion and growth regulation. In previous studies, we demonstrated that gal-1 induces cell differentiation processes on the membrane of choriocarcinoma cells BeWo, including the receptor tyrosine kinases (RTKs) REarranged during Transfection (RET), Janus Kinase 2 (JAK2) and Vascular endothelial growth factor receptor 3 (VEGFR3). Furthermore, Mitogen-Activated Protein Kinases (MAPK) and serine/threonine kinases were phosphorylated by gal-1. In addition, gal-1 in trophoblast cells in vitro induced syncytium formation especially after concentration dependent stimulation of the cells with this galectin. This is in contrast to MAPK-inhibitor U0126 that reduced syncytium formation of BeWo cells. The aim of this study was to analyze the syncytium formation abilities of BeWo cells that were gal-1 silenced. We found a significantly reduced syncytium formation rate in gal-1 silenced BeWo cells. In addition, these cells show a different miRNA expression profile. In summary, we found that gal-1 is a major trigger for fusion processes in BeWo cells. This function is accompanied by different regulation of miRNA synthesis in the BeWo cell culture model. PMID:26418280

  12. Studies on RF sputtered (WO3)1-x (V2O5)x thin films for smart window applications

    NASA Astrophysics Data System (ADS)

    Meenakshi, M.; Sivakumar, R.; Perumal, P.; Sanjeeviraja, C.

    2016-05-01

    V2O5 doped WO3 targets for RF sputtering thin film deposition were prepared for various compositions. Thin films of (WO3)1-x (V2O5)x were deposited on to glass substrates using these targets. Structural characteristics of the prepared targets and thin films were studied using X-ray diffraction. Laser Raman studies were carried out on the thin films to confirm the compound formation.

  13. Synthesis of WO{sub 3} nanoparticles by citric acid-assisted precipitation and evaluation of their photocatalytic properties

    SciTech Connect

    Sánchez-Martínez, D.; Martínez-de la Cruz, A.; López-Cuéllar, E.

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► WO{sub 3} nanoparticles were synthesized by a simple citric acid-assisted precipitation. ► WO{sub 3} photocatalyst was able to the partial mineralization of rhB, IC and MO. ► WO{sub 3} can be considered as a photocatalyst active under visible light irradiation. -- Abstract: WO{sub 3} nanoparticles were synthesized by citric acid-assisted precipitation method using a 1:1.5 molar ratio of ammonium paratungstate hydrate (H{sub 42}N{sub 10}O{sub 42}W{sub 12}·xH{sub 2}O):citric acid (C{sub 6}H{sub 8}O{sub 7}). The formation of monoclinic crystal structure of WO{sub 3} at different temperatures was confirmed by X-ray powder diffraction (XRD). The characterization of the samples synthesized was complemented by transmission electron microscopy (TEM), Brunauer–Emmitt–Teller surface area (BET) and diffuse reflectance spectroscopy (DRS). According to the thermal treatment followed during the synthesis of WO{sub 3}, the morphology of the nanoparticles formed was characterized by rectangular and ovoid shapes. The photocatalytic activity of WO{sub 3} obtained under different experimental conditions was evaluated in the degradation of rhodamine B (rhB), indigo carmine (IC), methyl orange (MO), and Congo red (CR) in aqueous solution under UV and UV–vis radiation. The highest photocatalytic activity was observed in the sample obtained by thermal treatment at 700 °C. In general, the sequence of degradation of the organic dyes was: indigo carmine (IC) > rhodamine B (rhB) > methyl orange (MO) > Congo red (CR). The mineralization degree of organic dyes by WO{sub 3} photocatalysts was determined by total organic carbon analysis (TOC) reaching percentages of mineralization of 82% (rhB), 85% (IC), 28% (MO), and 7% (CR) for 96 h of lamp irradiation.

  14. Optical absorption and emission properties of Nd 3+ in TeO 2 -WO 3 and TeO 2 -WO 3 -CdO glasses

    NASA Astrophysics Data System (ADS)

    Bilir, G.; Ozen, G.

    2011-11-01

    Effects of WO 3 and CdO on the spectroscopic properties of Nd 3+ doped tellurite glasses were investigated. The optical band gaps and Urbach energies of the samples were determined using the dependence of the absorption coefficient on the photon energy. The Urbach energies were found to vary from 0.18 to 0.25 eV as the WO 3 content in the binary glasses decreased from 20.0 to 10.0 mol% while the optical band gap of the same glasses did not show an appreciable dependence on the glass composition. Judd-Ofelt ( Ωt) parameters were calculated from the optical absorption spectra measured at room temperature. In all the glasses the J-O parameters follow the same trend as Ω2> Ω6> Ω4. The J-O intensity parameters were used to compute the radiative properties such as the radiative transition probabilities ( Aed), branching ratios ( β) and radiative lifetimes ( τr) for all the possible fluorescence bands. The fluorescence spectra obtained upon 805.2 nm excitation exhibited an intense emission band centered at 1064 nm ( 4F 3/2→ 4I 11/2) and two weak bands at 910 nm ( 4F 3/2→ 4I 9/2), and 1340 nm ( 4F 3/2→ 4I 13/2). The stimulated emission cross-section for the 1064 nm emission was determined using the emission spectra. The highest gain bandwidth ( σe×Δ λP) was determined to be 155.4 for the 0.79TeO 2-0.15WO 3-0.05CdO ternary glass composition, which could be more useful as promising material for the design and development of fiber amplifiers and lasers.

  15. A facile synthesis of ZnWO{sub 4} nanoparticles by microwave assisted technique and its application in photocatalysis

    SciTech Connect

    Garadkar, K.M.; Ghule, L.A.; Sapnar, K.B.; Dhole, S.D.

    2013-03-15

    Highlights: ► Nanocrystalline ZnWO{sub 4} particles were successfully prepared by a microwave method. ► Spherical morphology with a 10 nm size. ► The band is 3.4 eV. ► The photodegradation of RhB was 95% within 25 min. - Abstract: A simple microwave assisted technique has been successfully developed to synthesize ZnWO{sub 4} nanoparticles. The X-ray diffraction results indicated that the synthesized nanoparticles exhibited only wolframite structure. Structural, morphological and optical properties of ZnWO{sub 4} nanoparticles have been analyzed by XRD, SEM, TEM EDAX, UV–vis and FT-IR spectral measurements. The transmission electron microscopy (TEM) image revealed that particle size of ZnWO{sub 4} nanoparticles was found to be 10 nm, the band-gap of ZnWO{sub 4} nanoparticles was found to be 3.4 eV. The photocatalytic activities for aqueous Rhodamine B and Methylene Blue samples were investigated and observed that ZnWO{sub 4} nanoparticles exhibited highly enhanced photocatalytic activity towards RhB than MB.

  16. Preparation of hexagonal WO{sub 3} from hexagonal ammonium tungsten bronze for sensing NH{sub 3}

    SciTech Connect

    Szilagyi, Imre Miklos Wang Lisheng; Gouma, Pelagia-Irene; Balazsi, Csaba; Madarasz, Janos; Pokol, Gyoergy

    2009-03-05

    Hexagonal tungsten oxide (h-WO{sub 3}) was prepared by annealing hexagonal ammonium tungsten bronze, (NH{sub 4}){sub 0.07}(NH{sub 3}){sub 0.04}(H{sub 2}O){sub 0.09}WO{sub 2.95}. The structure, composition and morphology of h-WO{sub 3} were studied by XRD, XPS, Raman, {sup 1}H MAS (magic angle spinning) NMR, scanning electron microscopy (SEM), and BET-N{sub 2} specific surface area measurement, while its thermal stability was investigated by in situ XRD. The h-WO{sub 3} sample was built up by 50-100 nm particles, had an average specific surface area of 8.3 m{sup 2}/g and was thermally stable up to 450 deg. C. Gas sensing tests showed that h-WO{sub 3} was sensitive to various levels (10-50 ppm) of NH{sub 3}, with the shortest response and recovery times (1.3 and 3.8 min, respectively) to 50 ppm NH{sub 3}. To this NH{sub 3} concentration, the sensor had significantly higher sensitivity than h-WO{sub 3} samples prepared by wet chemical methods.

  17. WO3 Nanofiber-Based Biomarker Detectors Enabled by Protein-Encapsulated Catalyst Self-Assembled on Polystyrene Colloid Templates.

    PubMed

    Choi, Seon-Jin; Kim, Sang-Joon; Cho, Hee-Jin; Jang, Ji-Soo; Lin, Yi-Min; Tuller, Harry L; Rutledge, Gregory C; Kim, Il-Doo

    2016-02-17

    A novel catalyst functionalization method, based on protein-encapsulated metallic nanoparticles (NPs) and their self-assembly on polystyrene (PS) colloid templates, is used to form catalyst-loaded porous WO3 nanofibers (NFs). The metallic NPs, composed of Au, Pd, or Pt, are encapsulated within a protein cage, i.e., apoferritin, to form unagglomerated monodispersed particles with diameters of less than 5 nm. The catalytic NPs maintain their nanoscale size, even following high-temperature heat-treatment during synthesis, which is attributed to the discrete self-assembly of NPs on PS colloid templates. In addition, the PS templates generate open pores on the electrospun WO3 NFs, facilitating gas molecule transport into the sensing layers and promoting active surface reactions. As a result, the Au and Pd NP-loaded porous WO3 NFs show superior sensitivity toward hydrogen sulfide, as evidenced by responses (R(air)/R(gas)) of 11.1 and 43.5 at 350 °C, respectively. These responses represent 1.8- and 7.1-fold improvements compared to that of dense WO3 NFs (R(air)/R(gas) = 6.1). Moreover, Pt NP-loaded porous WO3 NFs exhibit high acetone sensitivity with response of 28.9. These results demonstrate a novel catalyst loading method, in which small NPs are well-dispersed within the pores of WO3 NFs, that is applicable to high sensitivity breath sensors.

  18. Nanospherical composite of WO3 wrapped NaTaO3: Improved photodegradation of tetracycline under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Qu, Lingnan; Lang, Junyu; Wang, Shuwei; Chai, Zhanli; Su, Yiguo; Wang, Xiaojing

    2016-12-01

    In this paper, WO3-wrapped NaTaO3 nanospheres photocatalysts with different W/Ta molar ratios were successfully prepared via a facile hydrothermal method. The samples were characterized by X-ray diffraction, transmission and scan electron microscopy, X-ray photoelectron spectroscopy, FT-IR spectrum, UV-vis diffuse reflectance spectroscopy, and Barrett-Emmett-Teller technique. The photocatalytic activities for degrading tetracycline hydrochloride under visible light irradiation were examined. The results indicated that the as-prepared NaTaO3@WO3 photocatalysts showed the obvious enhancement in the tetracycline hydrochloride degradation ratio, compared with the pure NaTaO3 and WO3 under visible light irradiation. The optimum percentage of NaTaO3@WO3 composites with a 60.88% degradation rate was W:Ta = 0.3:1 in mole, which was mainly attributed to the effective separation of the photo-generated electron and hole as well as the expanding of the absorption edge to the visible region due to the spherical heterojunction by wrapping WO3 on the surface of NaTaO3. The radicals trapping experiments demonstrated that there were multiple active species during the degrading process of TC. The possible mechanism of tetracycline hydrochloride degradation by NaTaO3@WO3 composite was also proposed.

  19. Facile synthesis of 2-D Cu doped WO3 nanoplates with structural, optical and differential anti cancer characteristics

    NASA Astrophysics Data System (ADS)

    Mehmood, Faisal; Iqbal, Javed; Gul, Asma; Ahmed, Waqqar; Ismail, M.

    2017-04-01

    Simple chemical co-precipitation method has been employed to synthesize two dimensional copper (Cu) doped tungsten oxide (WO3) nanoplates. A numbers of characterization techniques have been used to investigate their structural, optical and biocompatible anti cancer properties. The XRD results have confirmed the monoclinic crystal structure of WO3 nanoplates, and also successful doping of Cu ions into the WO3 crystal lattice. The presence of functional groups and chemical bonding have been verified through FTIR and Raman spectroscopy. The SEM images demonstrate that both undoped and Cu doped WO3 samples have squares plate like morphology. The EDX spectra confirm the presence of Cu, W and O ions. Diffuse reflectance spectroscopy (DRS) analysis has revealed a substantial red-shift in the absorption edge and a decrease in the band gap energy of nanoplates with Cu doping. Photoluminescence spectroscopy has been used to study the presence of defects like oxygen vacancies. Furthermore, the differential cytotoxic properties of Cu doped WO3 samples have been evaluated against human breast (MCF-7) and liver (Hep-2) cancer cells with ectocervical epithelial (HECE) healthy cells. The present findings confirm that the Cu doped WO3 nanoplates can be used as an efficient biocompatible anti cancer agent.

  20. Bi2WO6 nano- and microstructures: shape control and associated visible-light-driven photocatalytic activities.

    PubMed

    Zhang, Lisha; Wang, Wenzhong; Zhou, Lin; Xu, Haolan

    2007-09-01

    The shape-controlled synthesis of nano- and microstructured materials has opened up new possibilities to improve their physical and chemical properties. In this work, new types of Bi(2)WO(6) with complex morphologies, namely, flowerlike, tyre- and helixlike, and platelike shapes, have been controllably synthesized by a facile hydrothermal process. The benefits of the present work also stem from the first report on the transformation of Bi(2)WO(6) from three-dimensional (3D) flowerlike superstructures to 2D platelike structures, and on the formation of tyre- and helixlike Bi(2)WO(6) superstructures. UV/Vis absorption spectra show that the optical properties of Bi(2)WO(6) samples are relevant to their size and shape. More importantly, the photocatalytic activities of Bi(2)WO(6) nano- and microstructures are strongly dependent on their shape, size, and structure for the degradation of Rhodamine B (RhB) under visible-light irradiation. The reasons for the differences in the photocatalytic activities of these Bi(2)WO(6) nano- and microstructures are further investigated.

  1. Atomic layer deposition of diisopropylaminosilane on WO3(001) and W(110): a density functional theory study.

    PubMed

    Lee, Kyungtae; Lee, Woojin; Lee, Hyo Sug; Shin, Jaikwang; Park, Jieun; Lee, Seongsuk; Choi, Samjong; Kim, Sueryeon; Kim, Jinseong; Shim, Youngseon

    2016-10-26

    The decomposition reactions of the Si precursor, diisopropylaminosilane (DIPAS), on W(110) and hydroxylated WO3(001) surfaces are investigated to elucidate the initial reaction mechanism of the atomic layer deposition (ALD) process using density functional theory (DFT) calculations combined with ab initio molecular dynamics (AIMD) simulations. The decomposition reaction of DIPAS on WO3(001) consists of two steps: Si-N dissociative chemisorption and decomposition of SiH3*. It is found that the Si-N bond cleavage of DIPAS is facile on WO3(001) due to hydrogen bonding between the surface OH group and the N atom of DIPAS. The rate-determining step of DIPAS decomposition on WO3(001) is found to be the Si-H dissociation reaction of the SiH3* reaction intermediate which has an activation barrier of 1.19 eV. On the contrary, sequential Si-H dissociation reactions first occur on W(110) and then the Si-N dissociation reaction of the C5H7NSi* reaction intermediate is found to be the rate-determining step, which has an activation barrier of 1.06 eV. As a result, the final products in the DIPAS decomposition reaction on WO3(001) are Si* and SiH*, whereas Si* atoms remain with carbon impurities on W(110), which imply that the hydroxylated WO3 surface is more efficient for the ALD process.

  2. Immobilization of WO{sub 3} or MoO{sub 3} on macroscopic silica fiber via CNFs template

    SciTech Connect

    Wu, Qiang Zhao, Li; Han, Ruobing

    2013-08-01

    Graphical abstract: Uniform immobilization of tungsten trioxide (WO{sub 3}) or molybdenum trioxide (MoO{sub 3}) on silica fiber was successfully achieved by using carbon nanofibers (CNFs) as template. FE-SEM coupled with XRD analysis confirmed the template effect and the existence of WO{sub 3} or MoO{sub 3} immobilized on silica fiber. It is expected that such materials with direct macroscopic shapes would hold promise as highly functionalized materials for potential practical applications, especially in photocatalysis. - Highlights: • WO{sub 3} or MoO{sub 3} with macroscopic shapes were successfully obtained. • WO{sub 3} and MoO{sub 3} immobilization depended on CNFs templates. • FE-SEM and XRD confirmed the structure and phase composition. - Abstract: Uniform immobilization of tungsten trioxide (WO{sub 3}) or molybdenum trioxide (MoO{sub 3}) on silica fiber was successfully achieved by using carbon nanofibers (CNFs) as template. Field emission scanning electron microscopy (FE-SEM), coupled with X-ray diffraction (XRD) analysis confirmed the template effect and the existence of WO{sub 3} or MoO{sub 3} immobilized on silica fiber. It is expected that such materials with direct macroscopic shapes would hold promise as highly functionalized materials for potential practical applications, especially in photocatalysis.

  3. Synthesis of TiO2/WO3 nanoparticles via sonochemical approach for the photocatalytic degradation of methylene blue under visible light illumination.

    PubMed

    Anandan, Sambandam; Sivasankar, Thirugnanasambandam; Lana-Villarreal, Teresa

    2014-11-01

    Through an ultrasound assisted method, TiO2/WO3 nanoparticles were synthesized at room temperature. The XRD pattern of as-prepared TiO2/WO3 nanoparticles matches well with that of pure monoclinic WO3 and rutile TiO2 nanoparticles. TEM images show that the prepared TiO2/WO3 nanoparticles consist of mixed square and hexagonal shape particles about 8-12nm in diameter. The photocatalytic activity of TiO2/WO3 nanoparticles was tested for the degradation of a wastewater containing methylene blue (MB) under visible light illumination. The TiO2/WO3 nanoparticles exhibits a higher degradation rate constant (6.72×10(-4)s(-1)) than bare TiO2 nanoparticles (1.72×10(-4)s(-1)) under similar experimental conditions.

  4. A significant cathodic shift in the onset potential and enhanced photoelectrochemical water splitting using Au nanoparticles decorated WO3 nanorod array.

    PubMed

    Xu, Fang; Yao, Yanwen; Bai, Dandan; Xu, Ruishu; Mei, Jingjing; Wu, Dapeng; Gao, Zhiyong; Jiang, Kai

    2015-11-15

    Au nanoparticles decorated WO3 nanorod array was prepared and applied for solar water oxidation. Scanning electron microscopy and transmission electron microscop images showed that Au distributed on the surface of WO3 nanorod array. The surface plasmon resonance effect of Au nanoparticles contributed to the enhancement of photoelectrochemical performance of Au-WO3 photoanode, such as enhanced photocurrent density of 1.17mA/cm(2) at 1.0V vs Ag/AgCl, a cathodic shift of onset of ∼0.2V and higher stability. UV-vis absorption, electrochemical impedance and Mott-Schottky measurements proved that Au-WO3 photoanode has enhanced light absorption, lower transfer resistance, increased photogenerated carriers density and higher hole injection yield. Therefore, Au-WO3 photoanode exhibited higher photoelectrochemical performance than WO3 photoanode.

  5. A hierarchically porous anatase TiO2 coated-WO3 2D IO bilayer film and its photochromic properties.

    PubMed

    Li, Hua; Wu, Huazhong; Xiao, Jiajia; Su, Yanli; Robichaud, Jacques; Brüning, Ralf; Djaoued, Yahia

    2016-01-18

    A hierarchically porous anatase TiO2 coated-WO3 2D inverse opal (IO) bilayer film was fabricated on ITO glass using a layer by layer route with a hierarchically porous TiO2 top layer and an ordered super-macroporous WO3 2D IO bottom layer. This novel TiO2 coated-WO3 2D IO bilayer film was evaluated for photochromic applications.

  6. Defect engineering of two-dimensional WO3 nanosheets for enhanced electrochromism and photoeletrochemical performance

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaofang; Zheng, Xiaoli; Yan, Bo; Xu, Tao; Xu, Qun

    2017-04-01

    The capability of introduction of oxygen vacancies in a controlled way has emerged as the heart of modern transition metal oxide semiconductor chemistry. As chemical defects, the oxygen vacancies have been proposed as electron donors, which are prone to increase carrier density and promote charge carrier separation. Herein, we have successfully prepared 2D WO3 ultrathin nanosheets with abundant surface oxygen vacancies by a combination of facile solvothermal reaction and hydrogenation method. The resultant hydrogenated WO3 ultrathin nanosheets exhibit remarkable electrochromism and photocatalytic performances compared with the non-hydrogenated samples, mainly due to their increased oxygen vacancies, narrowed band gap coupled with fast charge transfer and enhanced adsorption of visible light.

  7. Synthesis and characterization of WO{sub 3} nanostructures prepared by an aged-hydrothermal method

    SciTech Connect

    Huirache-Acuna, R.; Paraguay-Delgado, F.; Albiter, M.A.; Lara-Romero, J.; Martinez-Sanchez, R.

    2009-09-15

    Nanostructures of tungsten trioxide (WO{sub 3}) have been successfully synthesized by using an aged route at low temperature (60 deg. C) followed by a hydrothermal method at 200 deg. C for 48 h under well controlled conditions. The material was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Specific Surface Area (S{sub BET}) were measured by using the BET method. The lengths of the WO{sub 3} nanostructures obtained are between 30 and 200 nm and their diameters are from 20 to 70 nm. The growth direction of the tungsten oxide nanostructures was determined along [010] axis with an inter-planar distance of 0.38 nm.

  8. Crystal Structure and Phase Transitions of Sr2CdWO6

    SciTech Connect

    Gateshki,M.; Igartua, J.; Faik, A.

    2007-01-01

    The crystal structure of Sr2CdWO6, prepared by solid state reaction, was determined by high-resolution X-ray diffraction at different temperatures. At room temperature, this compound has a monoclinic structure (space group P21/n) with a=5.7463(1), b=5.8189(1), c=8.1465(1), {beta}=90.071(1). At 1105 K the structure is converted to tetragonal (space group I4/m). Diffraction data also suggest that a cubic phase exists above 1220 K. Comparing the phase transition temperatures of Sr2CdWO6 with those of other compounds of the Sr2MWO6 family reported previously, it was observed that the transition temperatures are higher in compounds with low-tolerance factors. At the same time, the temperature range in which the intermediate tetragonal phase exists is reduced.

  9. Sub-nanosecond Yb:KLu(WO4)2 microchip laser.

    PubMed

    Loiko, P; Serres, J M; Mateos, X; Yumashev, K; Yasukevich, A; Petrov, V; Griebner, U; Aguiló, M; Díaz, F

    2016-06-01

    A diode-pumped Yb:KLu(WO4)2 microchip laser passively Q-switched by a Cr4+:YAG saturable absorber generated a maximum average output power of 590 mW at 1031 nm with a slope efficiency of 55%. The pulse characteristics were 690 ps/47.6 μJ at a pulse repetition frequency of 12.4 kHz. The output beam had an excellent circular profile with M2<1.05. Yb:KLu(WO4)2 is very promising for ultrathin sub-ns microchip lasers.

  10. Fabrication and high temperature electronic behaviors of n-WO3 nanorods/p-diamond heterojunction

    NASA Astrophysics Data System (ADS)

    Wang, Liying; Cheng, Shaoheng; Wu, Chengze; Pei, Kai; Song, Yanpeng; Li, Hongdong; Wang, Qinglin; Sang, Dandan

    2017-01-01

    This work explores the temperature-dependent characteristic and carrier transport behavior of a heterojunction of n-WO3 nanorods (NRs)/p-diamond. The n-type WO3 NRs grown by the hydrothermal method were deposited on a p-type boron-doped diamond film. The p-n heterojunction devices showed good thermal stability and have rectification characteristic from room temperature up to 290 °C. With increasing temperature, the turn-on voltages were decreased, and the rectification ratios were relatively high. The calculated ideality factor of the device decreased monotonously with increased temperature. The carrier transport mechanisms at different applied bias voltages following Ohmic laws, recombination-tunneling, and space-charge-limited current conduction of the heterojunction are discussed depending on temperature.

  11. Graphene Q-switched Tm:KY(WO4)2 waveguide laser

    NASA Astrophysics Data System (ADS)

    Kifle, E.; Mateos, X.; Loiko, P.; Yumashev, K.; Yasukevich, A.; Petrov, V.; Griebner, U.; Aguiló, M.; Díaz, F.

    2017-04-01

    We report on the first Tm3+-doped double tungstate waveguide laser passively Q-switched by a graphene saturable absorber using a 12.4 µm-thick 3 at.% Tm:KY0.58Gd0.22Lu0.17(WO4)2 epitaxial layer grown on a (0 1 0)-oriented pure KY(WO4)2 substrate. This laser generated 5.8 nJ/195 ns pulses at 1831.8 nm corresponding to a pulse repetition frequency of 1.13 MHz. These are the shortest pulses achieved in passively Q-switched Tm waveguide lasers. The laser slope efficiency was 9% and the Q-switching conversion efficiency reached 45%. Graphene is promising for the generation of ns pulses at ~2 µm in Tm3+-doped double tungstate waveguide lasers operating in the MHz-range.

  12. Synthesis and characterizations of isolated WO4 anchored on mesoporous TiTUD-1 support

    NASA Astrophysics Data System (ADS)

    Pachamuthu, Muthusamy P.; Maheswari, Rajamanickam; Ramanathan, Anand

    2017-04-01

    The titanium incorporated mesoporous silicate TUD-1 (Si/Ti ratio 40) was synthesized by non-surfactant route, and utilized as a support for tungstate (WO42-) species with variable loading (5-30 wt%). The structural and textural properties of these samples were evaluated from X-ray diffraction (XRD) and N2 physisorption studies. Diffuse reflectance UV-vis (DR UV-vis), Fourier transform infrared (FTIR), Fourier transform Raman (FT Raman) spectra evidenced the Ti4+ coordination and the formation of WO42- species, further supported by X-ray photoelectron spectroscopy (XPS) studies. Scanning electron microscope-energy dispersive X-ray analysis (SEM-EDAX), High resolution transmission electron microscope (HRTEM) further support the materials morphology corroborating other characterizations. The catalytic activities of these materials were tested in the liquid phase, solvent free esterification of acetic acid with n-butanol. About 95% of acetic acid conversion resulted by these catalysts with 8 h of reaction time.

  13. Solvothermal synthesis, characterization and photocatalytic performance of Zn-rich ZnWO4 nanocrystals

    NASA Astrophysics Data System (ADS)

    Wang, Yunjian; Liping, Li; Li, Guangshe

    2017-01-01

    Present work focuses on the surface composition disorder, its origin and relevance to photoluminescent and photocatalytic properties of ZnWO4 nanocrystals. ZnWO4 nanoparticles were synthesized under solvothermal conditions, in which formic acid was employed for both the nonstoichiometry and kinetic size control. Nonstoichiometry ranging from 1.05 to 1.18 was originated from the surface Zn-rich disorder layer, as reflected by an excess of cation Zn2+ in the X-ray photoelectron spectroscopy and a new Raman vibration mode at about 930 cm-1 and HR-TEM images. Surface Zn-rich disorder layer has shown a great impact on the structure and properties, including lattice expansion, band-gap narrowing, luminescence enhancement, as well as photocatalytic weakening effect. The investigation on surface composition disorder of multi-component oxides is helpful to deeply understand their formation process and further to find a new functionality optimizing approach.

  14. Quantitative hole collection for photoelectrochemical water oxidation with CuWO4.

    PubMed

    Gao, Yuan; Hamann, Thomas W

    2017-01-19

    The hole collection efficiency of water oxidation was evaluated for CuWO4 electrodes from comparisons of the photocurrent of H2O2 and Na2SO3 oxidation as well as intensity modulated photocurrent spectroscopy (IMPS) measurements. We found current multiplication using H2O2, however use of Na2SO3 and IMPS revealed quantitative water oxidation at 1.23 V vs. RHE.

  15. 5-Hydroxymethyl-oxazolidin-2-one antibacterials. Actelion Pharmaceuticals: WO2008062379.

    PubMed

    Phillips, Oludotun A; Sharaf, Leyla H

    2009-04-01

    The application, WO2008062379, claims chimeric compounds comprising chemically linked 5-hydroxymethyl-oxazolidinone and tetracyclic-quinolone moieties. The claimed compounds are potent expanded-range antibacterial agents against selected gram-positive and gram-negative bacteria, which may exhibit dual mode of action as inhibitors of topoisomarases IV and protein synthesis. The structures of the compounds suggest that the linkers are chemically and biochemically stable. This application represents part of recently initiated research efforts at Actelion.

  16. Structural, microstructural and vibrational analyses of the monoclinic tungstate BiLuWO{sub 6}

    SciTech Connect

    Ait Ahsaine, H.; Taoufyq, A.; Patout, L.; Ezahri, M.; Benlhachemi, A.; Bakiz, B.; Villain, S.; Guinneton, F.; Gavarri, J.-R.

    2014-10-15

    The bismuth lutetium tungstate phase BiLuWO{sub 6} has been prepared using a solid state route with stoichiometric mixtures of oxide precursors. The obtained polycrystalline phase has been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. In the first step, the crystal structure has been refined using Rietveld method: the crystal cell was resolved using monoclinic system (parameters a, b, c, β) with space group A2/m. SEM images showed the presence of large crystallites with a constant local nominal composition (BiLuW). TEM analyses showed that the actual local structure could be better represented by a superlattice (a, 2b, c, β) associated with space groups P2 or P2/m. The Raman spectroscopy showed the presence of vibrational bands similar to those observed in the compounds BiREWO{sub 6} with RE=Y, Gd, Nd. However, these vibrational bands were characterized by large full width at half maximum, probably resulting from the long range Bi/Lu disorder and local WO{sub 6} octahedron distortions in the structure. - Graphical abstract: The average structure of BiLuWO{sub 6} determined from X-ray diffraction data can be represented by A2/m space group. Experimental Electron Diffraction patterns along the [0vw] zone axes of the monoclinic structure and associated simulated patterns show the existence of a monoclinic superstructure with space group P2 or P2/m. - Highlights: • A new monoclinic BiLuWO{sub 6} phase has been elaborated from solid-state reaction. • The space group of the monoclinic disordered average structure should be A2/m. • Transmission electron microscopy leads to a superlattice with P2/m space group. • Raman spectroscopy suggests existence of local disorder.

  17. PbWO4 crystals for the CMS electro-magnetic calorimeter

    NASA Astrophysics Data System (ADS)

    Organtini, Giovanni

    1997-02-01

    In this paper results obtained by the CMS collaboration in the study of the properties of PbWO4 crystals chosen to construct the electro-magnetic calorimeter for the CMS experiment at LHC are reported. The main activities carried out by the collaboration during 1995/1996 were devoted to the definition of the properties of the crystals needed to fully characterise them for the final calorimeter assembly.

  18. PbWO 4 crystals for the CMS electro-magnetic calorimeter

    NASA Astrophysics Data System (ADS)

    Organtini, Giovanni; CMS Collaboration

    1998-02-01

    In this paper results obtained by the CMS collaboration in the study of the properties of PbWO 4 crystals chosen to construct the electro-magnetic calorimeter for the CMS experiment at LHC are reported. The main activities carried out by the collaboration during 1995/1996 were devoted to the definition of the properties of the crystals needed to fully characterise them for the final calorimeter assembly.

  19. [Characterization of pure and doped amorphous WO3 films by Raman spectroscopy].

    PubMed

    Lü, Gang; Wu, Yong-Gang; Wu, He-Yun; Xia, Zi-Huan; Liu, Ren-Chen

    2012-11-01

    Pure, TiO2-doped and TiO2/Ag-doped WO3 films were prepared by evaporation and electron beam evaporating. Raman spectroscopy and chronoamperometry were used to characterize the electrochromic properties of the samples. The correlation between the relative intensity of the Raman peaks, corresponding to the Raman sharp peak of the crystalline phase at 810 cm(-1) is negative, that is to say the higher the relative intensity of the Raman peaks, the smaller the coloration efficiency.

  20. Development of w/o microemulsion for transdermal delivery of iodide ions.

    PubMed

    Lou, Hao; Qiu, Ni; Crill, Catherine; Helms, Richard; Almoazen, Hassan

    2013-03-01

    The objective of this study was to develop a water-in-oil (w/o) microemulsion which can be utilized as a transdermal delivery for iodide ions. Several w/o microemulsion formulations were prepared utilizing Span 20, ethanol, Capryol 90®, and water. The selected formulations had 5%, 10%, 15%, 20%, and a maximum of 23% w/w water content. Potassium iodide (KI) was incorporated in all formulations at 5% w/v. Physicochemical characterizations were conducted to evaluate the structure and stability. These studies included: mean droplet size, pH, viscosity, conductivity, and chemical stability tests. In vitro human skin permeation studies were conducted to evaluate the diffusion of the iodide ion through human skin. The w/o microemulsion formulations were stable and compatible with iodide ions with water content ranging from 5% to 23% w/w. The addition of KI influenced the physicochemical properties of microemulsion as compared to blank microemulsion formulations. In vitro human skin permeation studies indicated that selected formulations improved iodide ion diffusion significantly as compared to control (KI solution; P value<0.05). Iodide ions were entrapped within the aqueous core of w/o microemulsion. Span 20, ethanol and Capryol 90 protected the iodide ions against oxidation and formed a stable microemulsion. It is worth to note that according to Hofmeister series, iodide ions tend to lower the interfacial tension between water and oil and consequently enhance overall stability. This work illustrates that microemulsion system can be utilized as a vehicle for the transdermal administration of iodide.

  1. Heterojunction-based two-dimensional N-doped TiO2/WO3 composite architectures for photocatalytic treatment of hazardous organic vapor.

    PubMed

    Lee, Joon Yeob; Jo, Wan-Kuen

    2016-08-15

    Two-dimensional nanosheet structures of N-doped TiO2/WO3 composites (WO3-N-TNSs) with varying WO3 loadings were synthesized by incorporating WO3 and N sources into sonochemically prepared TiO2 nanosheets (TNSs). These nanostructures were employed as photocatalysts, and their efficacy in the decomposition of hazardous hexane vapor was investigated. The photocatalytic efficiencies of the WO3-N-TNS composites were higher than those of N-doped TNS (N-TNS), which in turn were higher than the corresponding values for un-doped TNS. These variations were ascribed to the different light absorbance efficiencies, adsorption abilities, and charge carrier separations between the samples. An optimal WO3 loading for the performance of WO3-N-TNS was determined. Interestingly, the photocatalytic efficiency for hexane mixed with isopropyl alcohol (IPA) was lower than that for pure hexane, whereas the degradation efficiency for IPA did not vary with the feed method. Also investigated were the hexane conversion into CO2 over a representative WO3-N-TNS sample, the durability of the photocatalyst, and potential byproduct formation. Based on measurements of the hydroxyl radical population, a heterojunction-type mechanism was considered more plausible than a direct Z-scheme-type mechanism for the photocatalytic decomposition of hexane over the WO3-N-TNS photocatalysts.

  2. Fabrication and photocatalytic activity enhanced mechanism of direct Z-scheme g-C3N4/Ag2WO4 photocatalyst

    NASA Astrophysics Data System (ADS)

    Zhu, Bicheng; Xia, Pengfei; Li, Yao; Ho, Wingkei; Yu, Jiaguo

    2017-01-01

    Herein, a direct Z-scheme graphitic carbon nitride (g-C3N4)/silver tungstate (Ag2WO4) photocatalyst was prepared by a facile in situ precipitation method using g-C3N4 as a support and silver nitrate as a precursor. X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and elemental mapping demonstrated that β-Ag2WO4 nanoparticles were evenly distributed on the surface of g-C3N4 nanosheets, which acted as a support for the nucleation and growth of β-Ag2WO4 and inhibited the phase transformation of metastable β-Ag2WO4 to stable α-Ag2WO4. Photocatalytic experiments indicated that the g-C3N4/Ag2WO4 nanocomposite photocatalyst displayed a better photocatalytic activity than pure g-C3N4 and Ag2WO4 toward the degradation of methyl orange. The enhanced photocatalytic performance of g-C3N4/Ag2WO4 could be well explained by a direct Z-scheme photocatalytic mechanism. This mechanism was related to the efficient space separation of photogenerated electron-hole pairs and the great oxidation and reduction capabilities of the g-C3N4/Ag2WO4 system. This work provided new insights into the design and fabrication of g-C3N4-based direct Z-scheme photocatalysts.

  3. Composite WO3/TiO2 nanostructures for high electrochromic activity.

    SciTech Connect

    Reyes, Karla Rosa; Stephens, Zachary Dan.; Robinson, David B.

    2013-05-01

    A composite material consisting of TiO2 nanotubes (NTs) with WO3 electrodeposited homogeneously on its surface has been fabricated, detached from its substrate, and attached to a fluorine-doped tin oxide film on glass for application to electrochromic (EC) reactions. A paste of TiO2 made from commercially available TiO2 nanoparticles creates an interface for the TiO2 NT film to attach to the FTO glass, which is conductive and does not cause solution-phase ions in an electrolyte to bind irreversibly with the material. The effect of NT length on the current density and the EC contrast of the material were studied. The EC redox reaction seen in this material is diffusion- limited, having relatively fast reaction rates at the electrode surface. The composite WO3/TiO2 nanostructures showed higher ion storage capacity, better stability, enhanced EC contrast and longer memory time compared with the pure WO3 and TiO2.

  4. Heme-mediated apoptosis and fusion damage in BeWo trophoblast cells

    PubMed Central

    Liu, Mingli; Hassana, Salifu; Stiles, Jonathan K.

    2016-01-01

    Placental malaria (PM) is a complication associated with malaria infection during pregnancy that often leads to abortion, premature delivery, intrauterine growth restriction and low birth weight. Increased levels of circulating free heme, a by-product of Plasmodium-damaged erythrocytes, is a major contributor to inflammation, tissue damage and loss of blood brain barrier integrity associated with fatal experimental cerebral malaria. However, the role of heme in PM remains unknown. Proliferation and apoptosis of trophoblasts and fusion of the mononucleated state to the syncytial state are of major importance to a successful pregnancy. In the present study, we examined the effects of heme on the viability and fusion of a trophoblast-derived cell line (BeWo). Results indicate that heme induces apoptosis in BeWo cells by activation of the STAT3/caspase-3/PARP signaling pathway. In the presence of forskolin, which triggers trophoblast fusion, heme inhibits BeWo cell fusion through activation of STAT3. Understanding the effects of free plasma heme in pregnant women either due to malaria, sickle cell disease or other hemolytic diseases, will enable identification of high-risk women and may lead to discovery of new drug targets against associated adverse pregnancy outcome. PMID:27796349

  5. Spectroscopic and laser characterization of Yb,Tm:KLu(WO4)2 crystal

    NASA Astrophysics Data System (ADS)

    Loiko, P. A.; Serres, J. M.; Mateos, X.; Demesh, M. P.; Yasukevich, A. S.; Yumashev, K. V.; Petrov, V.; Griebner, U.; Aguiló, M.; Díaz, F.

    2016-01-01

    We report on a comprehensive spectroscopic and laser characterization of monoclinic Yb,Tm:KLu(WO4)2 crystals. Stimulated-emission cross-section spectra corresponding to the 3F4 → 3H6 transition of Tm3+ ions are determined. The radiative lifetime of the 3F4 state of Tm3+ ions is 0.82 ms. The maximum Yb3+ → Tm3+ energy transfer efficiency is 83.9% for 5 at.% Yb - 8 at.% Tm doping. The fractional heat loading for Yb,Tm:KLu(WO4)2 is 0.45 ± 0.05. Using a hemispherical cavity and 5 at.% Yb - 6 at.% Tm doped crystal, a maximum CW power of 227 mW is achieved at 1.983-2.011 μm with a maximum slope efficiency η = 14%. In the microchip laser set-up, the highest slope efficiency is 20% for a 5 at.% Yb- 8 at.% Tm doped crystal with a maximum output power of 201 mW at 1.99-2.007 μm. Operation of Yb,Tm:KLu(WO4)2 as a vibronic laser emitting at 2.081-2.093 μm is also demonstrated.

  6. BiVO(4)/CuWO(4) heterojunction photoanodes for efficient solar driven water oxidation.

    PubMed

    Pilli, Satyananda Kishore; Deutsch, Todd G; Furtak, Thomas E; Brown, Logan D; Turner, John A; Herring, Andrew M

    2013-03-07

    BiVO(4)/CuWO(4) heterojunction electrodes were prepared using spray deposition of a highly porous bismuth vanadate film onto the surface of an electrodeposited three dimensional network connected copper tungstate. Bilayer BiVO(4)/CuWO(4)/fluorine doped tin oxide glass (FTO) electrodes demonstrated higher photocurrent magnitudes than either with BiVO(4)/FTO or CuWO(4)/FTO electrodes in 1.0 M Na(2)SO(4) electrolyte buffered at pH 7. The photocurrent is enhanced by the formation of the heterojunction that aids charge carrier collection brought about by the band edge offsets. When the pH 7 buffered electrolytes contained 1.0 M bicarbonate is employed instead of 1.0 M sulfate, the charge transfer resistance was decreased. This led to nearly 1.8 times the photocurrent density at 1.0 V vs. Ag/AgCl. The photocurrent was stable over 24 hours in bicarbonate electrolyte.

  7. Substituted indole Mcl-1 inhibitors: a patent evaluation (WO2015148854A1).

    PubMed

    Song, Ting; Wang, Ziqian; Zhang, Zhichao

    2016-10-04

    The myeloid cell leukemia 1 (Mcl-1) protein, an anti-apoptotic member of Bcl-2 family, plays a critical role in the development and maintenance of many cancers and is listed in the 'top ten' pathological factors across the diversity of human cancers. The patent described in this evaluation (WO2015148854A1) claimed substituted indole Mcl-1 inhibitors for the treatment of diseases and conditions (e.g., cancer) characterized by the over-expression or dysregulation of Mcl-1 proteins. A variety of 2-position substituents distinguished indole Mcl-1 inhibitors claimed in this patent from another two patents by AbbVie Inc. (WO2008131000A2 and WO2008130970A1). They exhibited low-nanomolar binding affinities and >100-fold selectivity over Bcl-2 and Bcl-xL in vitro, and low-micromolar killing abilities against a panel of tumour cell lines. Moreover, the compounds in this patent revealed that the structural basis for selective Mcl-1 inhibitors may not completely depend on the 5 known binding hot-spots, and conformational flexibility of Mcl-1 protein could contribute to the binding specificity.

  8. Non-equilibrium Phonons in CaWO4: Issues for Phonon Mediated Particle Detectors

    NASA Astrophysics Data System (ADS)

    Msall, Madeleine; Head, Timothy; Jumper, Daniel

    2009-03-01

    The CRESST experiment looks for evidence of dark matter particles colliding with nuclei in CaWO4, using cryogenic bolometers sensitive to energy deposition ˜ 10 keV with a few percent accuracy. Calibration of the energy deposited in the phonon system depends upon the details of the evolution of the non-equilibrium energy in the CaWO4 absorber. Our phonon images sensitively measure variations in angular phonon flux, providing key information about the elastic constants and scattering rates that determine the energy evolution. Phonon pulses, created by focused photoexcitation of a 150 nm Cu film, are detected after propagation through 3 mm of CaWO4. The 20 ns Ar-ion laser pulse creates a localized (10-3 mm^2) source of 10-20 K blackbody phonons. The sample is at 2 K. Our images show that the elastic constants derived from ultrasonic velocities along high symmetry axes do not accurately predict the total phonon flux along non-symmetry directions. We present new data on the dependence of phonon flux on excitation level and discuss the influence of isotope and anharmonic decay on the shape of phonon pulses in these ultrapure samples. Thanks to J.P. Wolfe and the Frederick Seitz Materials Research Laboratory, Urbana, IL, for partial support of this work.

  9. Optical properties and photocatalytic activities of tungsten oxide (WO3) with platinum co-catalyst addition

    NASA Astrophysics Data System (ADS)

    Widiyandari, Hendri; Firdaus, Iqbal; Kadarisman, Vincencius Gunawan Slamet; Purwanto, Agus

    2016-02-01

    This research reported the optical properties and photocatalytic activities of tungsten oxide with platinum co-catalyst addition (WO3/Pt) film. The platinum was deposited on the surface of WO3 particle using photo deposition method, while the film formation of WO3/Pt on the glass substrate was prepared using spray deposition method. The addition of Pt of 0, 1, 2, and 4 wt.% resulted that the energy band gap value of the films were shifted to 2.840, 2.752, 2.623 and 2.507 eV, respectively. The as-prepared films were tested for methylene blue (MB) dye photo-degradation using the LED (light emitting diode) lamp as a visible domestic source light. The enhancement of photocatalytic activity was observed after the addition of Pt as a co-catalyst. The degradation kinetics analysis of the photo-catalyst showed that the Pt addition resulted increasing of photo-catalysis reaction rate constant, k.

  10. Electrochemical Nanolithography on Amorphous WO3 Thin Films Using Scanning Tunneling Microscope in Air

    NASA Astrophysics Data System (ADS)

    Qiu, Hong; Lu, Yong-Feng; Mai, Zhi-Hong

    2001-11-01

    Tungsten oxide (WO3) thin films have shown interesting properties as lithography resist materials. In this study, the scanning tunneling microscope (STM) was used in air for nanometer etching of α-WO3-x thin films, an n-type semiconductor. The current-voltage (I-V) curve was found to be affected by the water layer absorbed on the surface. For low voltage (< 3 V) with long duration (˜ 10 s) or high voltage pulse (> 3 V) with short pulsewidth (˜ 200 ms), holes were formed on the film surface at high humidity (> 70%) by applying a pulse voltage. A threshold voltage existed for hole formation. Higher pulse voltage and negative polarity corresponded to larger modified size. All the structures formed in STM images were topographical in nature by comparison with the AFM images. The hole formation was reasonably attributed to electrochemistry and high dissolution of WO3 in high pH solutions, which was co-manifested by links between the holes and eroded materials on the surface. Alkaline solutions instead of deionized water were chosen to act in the tip-surface gap. Alkaline ions being expelled from the tip due to electric polarity demonstrated the ion movement and their effect on etching. Lines of nanometer width were fabricated.

  11. Pressure-induced phase transitions of β-type pyrochlore CsTaWO6

    DOE PAGES

    Zhang, F. X.; Tracy, C. L.; Shamblin, J.; ...

    2016-09-30

    The β-type pyrochlore CsTaWO6 was studied by synchrotron X-ray diffraction (XRD) and Raman scattering methods up to pressures of 43 GPa using a diamond anvil cell (DAC). With increasing pressure, the cubic pyrochlore in space group of Fd-3¯m with combining macron]m transforms to an orthorhombic structure (space group: Pnma) at 5.9 GPa and then to a monoclinic structure (space group: P21/c) at ~18 GPa. The structural evolution in CsTaWO6 is a continuous process and experimental results suggest that the initial cubic phase has a tetragonal distortion at ambient conditions. Both XRD and Raman measurements indicate that the pressure-induced phase transitionsmore » in CsTaWO6 are reversible. Lastly, these results may provide a structural explanation of previous experimental resistivity measurement results for the isostructural superconductor K(Cs)Os2O6 at high pressure conditions.« less

  12. TiO2/WO3 photoactive bilayers in the UV-Vis light region

    NASA Astrophysics Data System (ADS)

    Vasilaki, E.; Vernardou, D.; Kenanakis, G.; Vamvakaki, M.; Katsarakis, N.

    2017-04-01

    In this work, photoactive bilayered films consisting of anatase TiO2 and monoclinic WO3 were synthesized by a sol-gel route. Titanium isopropoxide and tungsten hexachloride were used as metal precursors and deposition was achieved by spin-coating on Corning glass substrates. The samples were characterized by X-ray diffraction, photoluminescence, UV-Vis, and Raman spectroscopy, as well as field emission scanning electron microscopy. The prepared immobilized catalysts were tested for their photocatalytic performance by the decolorization of methylene blue in aqueous matrices, under UV-Vis light irradiation. The annealing process influenced the crystallinity of the bilayered films, while the concentration of the tungsten precursor solution and the position of the tungsten trioxide layer further affected their photocatalytic performance. In particular, the photocatalytic performance of the bilayered films was optimized at a concentration of 0.1 M of the WO3 precursor solution, when deposited as an overlying layer on TiO2 by two annealing steps ( 76% methylene blue decolorization in 300 min of irradiation versus 59% in the case of a bare TiO2 film). In general, the coupled layer catalysts exhibited superior photoactivity compared to that of bare TiO2 films with WO3 acting as an electron trap, resulting, therefore, in a more efficient electron-hole separation and inhibiting their recombination.

  13. Radiopurity of CaWO4 crystals for direct dark matter search with CRESST and EURECA

    NASA Astrophysics Data System (ADS)

    Münster, A.; Sivers, M. v.; Angloher, G.; Bento, A.; Bucci, C.; Canonica, L.; Erb, A.; Feilitzsch, F. v.; Gorla, P.; Gütlein, A.; Hauff, D.; Jochum, J.; Kraus, H.; Lanfranchi, J.-C.; Laubenstein, M.; Loebell, J.; Ortigoza, Y.; Petricca, F.; Potzel, W.; Pröbst, F.; Puimedon, J.; Reindl, F.; Roth, S.; Rottler, K.; Sailer, C.; Schäffner, K.; Schieck, J.; Scholl, S.; Schönert, S.; Seidel, W.; Stodolsky, L.; Strandhagen, C.; Strauss, R.; Tanzke, A.; Uffinger, M.; Ulrich, A.; Usherov, I.; Wawoczny, S.; Willers, M.; Wüstrich, M.; Zöller, A.

    2014-05-01

    The direct dark matter search experiment CRESST uses scintillating CaWO4 single crystals as targets for possible WIMP scatterings. An intrinsic radioactive contamination of the crystals as low as possible is crucial for the sensitivity of the detectors. In the past CaWO4 crystals operated in CRESST were produced by institutes in Russia and the Ukraine. Since 2011 CaWO4 crystals have also been grown at the crystal laboratory of the Technische Universität München (TUM) to better meet the requirements of CRESST and of the future tonne-scale multi-material experiment EURECA. The radiopurity of the raw materials and of first TUM-grown crystals was measured by ultra-low background γ-spectrometry. Two TUM-grown crystals were also operated as low-temperature detectors at a test setup in the Gran Sasso underground laboratory. These measurements were used to determine the crystals' intrinsic α-activities which were compared to those of crystals produced at other institutes. The total α-activities of TUM-grown crystals as low as 1.23±0.06 mBq/kg were found to be significantly smaller than the activities of crystals grown at other institutes typically ranging between ~ 15 mBq/kg and ~ 35 mBq/kg.

  14. Spectroscopy of tetragonal Eu:NaGd(WO4)2 crystal

    NASA Astrophysics Data System (ADS)

    Loiko, P. A.; Vilejshikova, E. V.; Mateos, X.; Serres, J. M.; Dashkevich, V. I.; Orlovich, V. A.; Yasukevich, A. S.; Kuleshov, N. V.; Yumashev, K. V.; Grigoriev, S. V.; Vatnik, S. M.; Bagaev, S. N.; Pavlyuk, A. A.

    2016-07-01

    We report on growth and detailed spectroscopic study of Eu3+-doped tetragonal sodium gadolinium double tungstate, Eu:NaGd(WO4)2, a new promising crystal for deep-red lasers. Large-volume crystal doped with 4.9 at.% Eu is grown by Czochralski method along the [001] crystallographic direction. Absorption of Eu3+ ions is studied at room temperature (RT) and at 6 K. For the absorption band related to the 7F1 → 5D1 transition suitable for pumping of Eu:NaGd(WO4)2, the maximum cross-section is σabs = 1.2 × 10-21 cm2 at 535.5 nm with the full width at half maximum (FWHM) of 3.1 nm (at RT, for E || a polarization). For the 5D0 → 7F4 transition, the maximum stimulated-emission cross-section is σSE = 1.6 × 10-21 cm2 at 698.3 nm (RT, E || c polarization). Lifetime of the 5D0 state is 490 ± 10 μs (at RT). Under UV excitation, Eu:NaGd(WO4)2 provides intense red emission with CIE coordinates (x = 0.671, y = 0.329).

  15. Visible-light-driven Bi 2 O 3 /WO 3 composites with enhanced photocatalytic activity

    DOE PAGES

    Adhikari, Shiba P.; Dean, Hunter; Hood, Zachary D.; ...

    2015-10-19

    Semiconductor heterojunctions (composites) have been shown to be effective photocatalytic materials to overcome the drawbacks of low photocatalytic efficiency that results from electron–hole recombination and narrow photo-response range. We prepared a novel visible-light-driven Bi2O3/WO3 composite photocatalyst by hydrothermal synthesis. The composite was characterized by scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) surface area, Raman spectroscopy, photoluminescence spectroscopy (PL) and electrochemical impedance spectroscopy (EIS) to better understand the structures, compositions, morphologies and optical properties. Bi2O3/WO3 heterojunction was found to exhibit significantly higher photocatalytic activity towards the decomposition of Rhodaminemore » B (RhB) and 4-nitroaniline (4-NA) under visible light irradiation compared to that of Bi2O3 and WO3. A tentative mechanism for the enhanced photocatalytic activity of the heterostructured composite is discussed based on observed activity, band position calculations, photoluminescence, and electrochemical impedance data. Our study provides a new strategy for the design of composite materials with enhanced visible light photocatalytic performance.« less

  16. Self-bleaching mechanism of electrochromic WO{sub 3} films

    SciTech Connect

    Zhang, J.G.; Benson, D.K.; Tracy, C.E.; Webb, J.; Deb, S.K.

    1993-12-31

    The authors report the first investigation of the self-bleaching behavior of electrochemically colored WO{sub 3} films. These films exhibit accelerated self-bleaching behavior over an 8-hour period when exposed to ambient air and show negligible or limited transmittance changes in other environments. The rate of self-bleaching in these films also depends on their preparation conditions, the electrolytes used in the coloring process, and film thickness and roughness. Self-bleaching in a WO{sub 3} film colored by lithium ions can be attributed mainly to the reaction between Li{sup +} ions and water vapor, but self-bleaching in WO{sub 3} films colored by protons may be mainly due to the reaction between H{sup +} and oxygen. The fast self-bleaching of the films in their early stages is dominated by the reaction of surface Li{sup +} or H{sup +} ions which are in direct contact with the reactive gases. The rate of self-bleaching increases with increasing film surface roughness but decreases with film thickness. The latter stages of self-bleaching exhibit a slower transmittance increase and are limited by diffusion of the reaction species.

  17. WO3/Pt nanoparticles promote light-induced lipid peroxidation and lysosomal instability within tumor cells

    NASA Astrophysics Data System (ADS)

    Clark, Andrea J.; Petty, Howard R.

    2016-02-01

    Although metal-metal oxide nanoparticles have attracted considerable interest as catalysts, they have attracted little interest in nanomedicine. This is likely due to the fact that metal oxide semiconductors generally require biologically harmful ultraviolet excitation. In contrast, this study focuses upon WO3/Pt nanoparticles, which can be excited by visible light. To optimize the nanoparticles’ catalytic performance, platinization was performed at alkaline pH. These nanoparticles destroyed organic dyes, consumed dissolved oxygen and produced hydroxyl radicals. 4T1 breast cancer cells internalized WO3/Pt nanoparticles within the membrane-bound endo-lysosomal compartment as shown by electron and fluorescence microscopy. During visible light exposure, but not in darkness, WO3/Pt nanoparticles manufacture reactive oxygen species, promote lipid peroxidation, and trigger lysosomal membrane disruption. As cells of the immune system degrade organic molecules, produce reactive oxygen species, and activate the lipid peroxidation pathway within target cells, these nanoparticles mimic the chemical attributes of immune effector cells. These biomimetic nanoparticles should become useful in managing certain cancers, especially ocular cancer.

  18. Carbon materials as additives to WO3 for an enhanced conversion of simulated solar light

    NASA Astrophysics Data System (ADS)

    Carmona, Rocío; Velasco, Leticia; Laurenti, Enzo; Maurino, Valter; Ania, Conchi

    2016-02-01

    We have explored the impact of the incorporation of nanoporous carbons as additives to tungsten oxide on the photocatalytic degradation of two recalcitrant pollutants: rhodamine B and phenol, under simulated solar light. For this purpose, WO3/carbon mixtures were prepared using three carbon materials with different properties (in terms of porosity, structural order and surface chemistry). Despite the low carbon content used (2 wt. %), a significant increase in the photocatalytic performance of the semiconductor was observed for all the catalysts. Moreover, the influence of the carbon additive on the performance of the photocatalysts was found to be very different for the two pollutants. Carbon additives of hydrophobic nature increased the photodegradation yield of phenol compared to bare WO3, likely due to the higher affinity and stronger interactions of phenol molecules towards basic nanoporous carbons. Oppositely, the use of acidic carbon additives led to higher rhodamine B conversions due to increased acidity of the WO3/carbon mixtures and the stronger affinity of the pollutant for acidic catalyst’s surfaces. As a result, the photooxidation of rhodamine B is favored by means of a coupled (photosensitized and photocatalytic) degradation mechanism. All these results highlight the importance of favoring the interactions of the pollutant with the catalyst’s surface through a detailed design of the features of the photocatalyst.

  19. Room-temperature deposition of nanocrystalline PbWO 4 thin films by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Ryu, J. H.; Yoon, J.-W.; Shim, K. B.; Koshizaki, N.

    2006-07-01

    Pulsed laser ablation (PLA) was applied to synthesize nanocrystalline PbWO4 thin films onto glass substrates. The effects of Ar background gas pressure on phase evolution, microstructures and optical characteristics of PbWO4 thin films were investigated in detail. The PLA processes were carried out at room temperature without substrate heating or post-annealing treatment. XRD and HR-TEM results revealed that the PbWO4 thin films are composed of nanocrystalline and amorphous phases. Moreover, the films contained a high density of lattice defects such as twin boundaries and edge dislocations. The crystallite size and crystallinity increased, which were associated with a change in surface morphology as the Ar pressure increased. Reduced tungsten states W5+ or W4+ induced by oxygen vacancies were observed at 10 Pa and the atomic concentration of all constituent element was almost stoichiometric, especially the [Pb]/[W] ratio, which was nearly unity above 50 Pa. The optical energy band-gap was 3.03 eV at 50 Pa and increased to 3.35 eV at 100 Pa, which are narrower than the reported value (4.20 eV). This optical band-gap narrowing could be attributed to localized band-tail states and new energy levels induced by the amorphous structure and inherent lattice defects.

  20. Preparation of ultra-thin and high-quality WO{sub 3} compact layers and comparision of WO{sub 3} and TiO{sub 2} compact layer thickness in planar perovskite solar cells

    SciTech Connect

    Zhang, Jincheng; Shi, Chengwu Chen, Junjun; Wang, Yanqing; Li, Mingqian

    2016-06-15

    In this paper, the ultra-thin and high-quality WO{sub 3} compact layers were successfully prepared by spin-coating-pyrolysis method using the tungsten isopropoxide solution in isopropanol. The influence of WO{sub 3} and TiO{sub 2} compact layer thickness on the photovoltaic performance of planar perovskite solar cells was systematically compared, and the interface charge transfer and recombination in planar perovskite solar cells with TiO{sub 2} compact layer was analyzed by electrochemical impedance spectroscopy. The results revealed that the optimum thickness of WO{sub 3} and TiO{sub 2} compact layer was 15 nm and 60 nm. The planar perovskite solar cell with 15 nm WO{sub 3} compact layer gave a 9.69% average and 10.14% maximum photoelectric conversion efficiency, whereas the planar perovskite solar cell with 60 nm TiO{sub 2} compact layer achieved a 11.79% average and 12.64% maximum photoelectric conversion efficiency. - Graphical abstract: The planar perovskite solar cell with 15 nm WO{sub 3} compact layer gave a 9.69% average and 10.14% maximum photoelectric conversion efficiency, whereas the planar perovskite solar cell with 60 nm TiO{sub 2} compact layer achieved a 11.79% average and 12.64% maximum photoelectric conversion efficiency. Display Omitted - Highlights: • Preparation of ultra-thin and high-quality WO{sub 3} compact layers. • Perovskite solar cell with 15 nm-thick WO{sub 3} compact layer achieved PCE of 10.14%. • Perovskite solar cell with 60 nm-thick TiO{sub 2} compact layer achieved PCE of 12.64%.

  1. Numerical simulation and experimental study of PbWO4/EPDM and Bi2WO6/EPDM for the shielding of γ-rays

    NASA Astrophysics Data System (ADS)

    Song, Chi; Zheng, Jian; Zhang, Quan-Ping; Li, Yin-Tao; Li, Ying-Jun; Zhou, Yuan-Lin

    2016-08-01

    The MCNP5 code was employed to simulate the γ-ray shielding capacity of tungstate composites. The experimental results were applied to verify the applicability of the Monte Carlo program. PbWO4 and Bi2WO6 were prepared and added into ethylene propylene diene monomer (EPDM) to obtain the composites, which were tested in the γ-ray shielding. Both the theoretical simulation and experiments were carefully chosen and well designed. The results of the two methods were found to be highly consistent. In addition, the conditions during the numerical simulation were optimized and double-layer γ-ray shielding systems were studied. It was found that the γ-ray shielding performance can be influenced not only by the material thickness ratio but also by the arrangement of the composites. Supported by Research Funds of Southwest University of Science and Technology (15zx7159) and Open Fund of State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Sichuan Province (13zxfk07)

  2. Low-temperature synthesis of homogeneous solid solutions of scheelite-structured Ca1-xSrxWO4 and Sr1-xBaxWO4 nanocrystals

    DOE PAGES

    Culver, Sean P.; Greaney, Matthew J.; Tinoco, Antonio; ...

    2015-07-24

    Here, a series of compositionally complex scheelite-structured nanocrystals of the formula A1-xA’xWO4 (A = Ca, Sr, Ba) have been prepared under benign synthesis conditions using the vapor diffusion sol–gel method. Discrete nanocrystals with sub-20 nm mean diameters were obtained after kinetically controlled hydro- lysis and polycondensation at room temperature, followed by composition-dependent thermal aging at or below 60 °C. Rietveld analysis of X-ray diffraction data and Raman spectroscopy verified the synthesis of continuous and phase-pure nanocrystal solid solutions across the entire composition space for A1-xA’xWO4, where 0 ≤ x ≤ 1. Elemental analysis by X-ray photoelectron and inductively coupled plasma-more » atomic emission spectroscopies demonstrated excellent agreement between the nominal and experi- mentally determined elemental stoichiometries, while energy dispersive X-ray spectroscopy illustrated good spatial elemental homogeneity within these nanocrystals synthesized under benign conditions.« less

  3. Evaluate humidity sensing properties of novel TiO{sub 2}–WO{sub 3} composite material

    SciTech Connect

    Lin, Wang-De; Lai, De-Sheng; Chen, Min-Hung; Wu, Ren-Jang; Chen, Fu-Chou

    2013-10-15

    Graphical abstract: TiO{sub 2}–WO{sub 3} (1:1) showed better humidity sensing properties than others within the range of 12–90% relative humidity (RH), the response and recovery time were about 20 s and 160 s, respectively. Compared to the previous studies, the prepared sensor exhibits higher sensitivity (S = 451) and the low hysteresis value was around 0.13% at 32% RH. - Highlights: • Novel TiO{sub 2}–WO{sub 3} composite material was prepared for humidity sensor. • The sensor exhibits higher sensitivity (S = 451). • Low hysteresis value was around 0.13% at 32% RH. - Abstract: A novel TiO{sub 2}–WO{sub 3} composite material was prepared using a different proportion of TiO{sub 2} and WO{sub 3} to that investigated in previous studies. The obtained mesoporous material was characterized using X-ray diffraction, Fourier transform infrared spectrometry, transmission electron microscopy, energy dispersive X-ray spectroscopy, and N{sub 2} adsorption-desorption techniques. The humidity-sensing properties were measured using an inductance, capacitance and resistance analyzer. The results demonstrated that the TiO{sub 2}–WO{sub 3} sample with a ratio of 1:1 showed better humidity sensing properties. Compared to previous studies, the prepared sensor exhibited higher sensitivity (S = 451) and the lower hysteresis value was around 0.13% at 32% RH. Complex impedance analysis indicated that the enhanced humidity sensitivity was probably due to spherical Brunauer–Emmett–Teller surface area and the hetero-junction between TiO{sub 2}–WO{sub 3} thin films, while the impedance varied about three orders of magnitude. Our results demonstrated the potential application of TiO{sub 2}–WO{sub 3} composite for fabricating high performance humidity sensors.

  4. Enhancement of photocatalytic properties of Bi{sub 2}WO{sub 6} nanoparticles by Pt deposition

    SciTech Connect

    Mohamed, R.M.; Aazam, E.S.

    2013-09-01

    Graphical abstract: - Highlights: • Pt/Bi{sub 2}WO{sub 6} was used for photocatalytic degradation of methyl orange dye. • Photocatalytic degradation was dependent on wt% of Pt reaction time, and weight of catalyst. • Kinetic study revealed that the photocatalytic degradation of methyl orange dye followed the first order. • Catalyst re-use revealed the present photocatalyst remain effective and active after five cycles. - Abstract: Bi{sub 2}WO{sub 6} nanoparticles were prepared using a hydrothermal method, and Pt was immobilized on the surface of Bi{sub 2}WO{sub 6} via a photo-assisted deposition (PAD) method. The samples produced were characterized using X-ray diffraction, ultraviolet and visible spectroscopy, photoluminescence emission spectra, transmission electron microscopy, extended X-ray absorption fine structure, and surface area measurements. Furthermore, the catalytic performance of the Bi{sub 2}WO{sub 6} and Pt/Bi{sub 2}WO{sub 6} samples was examined in the degradation of methyl orange dye (MO) under visible light. The extended X-ray absorption fine structure (EXAFS) results, which showed the presence of peaks assigned to the Pt–Pt at approximately 2.50 Å, indicate the formation of nanoscale Pt features. The UV–vis spectral analysis detected a red shift after loading the Pt into the Bi{sub 2}WO{sub 6}. The maximum degradation efficiency achieved was 100% with 0.3 Pt/Bi{sub 2}WO{sub 6} as the photocatalyst after a 30-min reaction time. The catalyst could be reused without any loss in activity for the first five cycles.

  5. Preparation and characterization of zinc and copper co-doped WO3 nanoparticles: Application in photocatalysis and photobiology.

    PubMed

    Mohammadi, Sanaz; Sohrabi, Maryam; Golikand, Ahmad Nozad; Fakhri, Ali

    2016-08-01

    In this study, pure, Zn, Cu, Zn,Cu co-doped WO3 nanoparticles samples were prepared by precipitation and co-precipitation methods. These nanoparticles were characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), energy dispersive X-ray spectrometer (EDX), Dynamic light scattering (DLS), UV-visible and photoluminescence (PL) spectroscopy. The synthesized pure, Zn, Cu, Zn,Cu co-doped WO3 nanoparticles have smart optical properties and average sizes with 3.2, 3.12, 3.08 and 2.97eV of band-gap, 18.1, 23.2, 25.7 and 30.2nm, respectively. Photocatalytic activity of four nanoparticles was studying towards degradation of gentamicin antibiotic under ultraviolet and visible light irradiation. The result showed that Zn,Cu co-doped WO3 possessed high photocatalytic activity. The photocatalytic activity of WO3 nanoparticles could be remarkably increased by doping the Zn and Cu impurity. This can be attributed to the fact that the red shift of absorption edge and the trapping effect of the mono and co-doped WO3 nanoparticles. The research result presents a general and effective way to prepare different photocatalysts with enhanced visible and UV light-driven photocatalytic performance. Antibacterial activity of four different WO3 nanoparticles against Escherichia coli bacterium has been assessed by the agar disc method under light irradiation and dark medium. It is concluded from the present findings that WO3 nanoparticles can be used as an efficient antibacterial agent.

  6. A templated method to Bi2WO6 hollow microspheres and their conversion to double-shell Bi2O3/Bi2WO6 hollow microspheres with improved photocatalytic performance.

    PubMed

    Li, Xiaona; Huang, Renkun; Hu, Yanhua; Chen, Yongjuan; Liu, Wenjun; Yuan, Rusheng; Li, Zhaohui

    2012-06-04

    Bi(2)WO(6) hollow microspheres with dimension of ca. 1.5 μm were synthesized via a hydrothermal method using polystyrene particles as the template. The as-prepared Bi(2)WO(6) hollow microspheres can be further transformed to double-shell Bi(2)O(3)/Bi(2)WO(6) hollow microspheres. The samples were fully characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, N(2)-sorption Brunauer-Emmett-Teller surface area, UV-vis diffuse-reflectance spectroscopy, and X-ray photoelectron spectroscopy. The as-formed double-shell Bi(2)O(3)/Bi(2)WO(6) hollow microspheres exhibit enhanced photocatalytic activity due to the hollow nature and formation of the p-n junction between p-type Bi(2)O(3) and n-type Bi(2)WO(6). The study provides a general and effective method in the fabrication of composition and dimension-tunable composite hollow microspheres with sound heterojunctions that may show a variety of applications.

  7. Low Thermal Gradient Czochralski growth of large CdWO{sub 4} crystals and electronic properties of (010) cleaved surface

    SciTech Connect

    Atuchin, V.V.; Galashov, E.N.; Khyzhun, O.Y.; Bekenev, V.L.; Pokrovsky, L.D.; Borovlev, Yu.A.; Zhdankov, V.N.

    2016-04-15

    The crystal growth of large high-quality inclusion-free CdWO4 crystals, 110 mm in diameter and mass up to 20 kg, has been carried out by the Low Thermal Gradient Czochralski (LTG Cz) technique. The high-purity CdWO{sub 4}(010) surface has been prepared by cleavage and high structural quality of the surface has been verified by RHEED, revealing a system of Kikuchi lines. The chemical state and electronic structure of the surface have been studied using X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES). The total and partial densities of states of the CdWO{sub 4} tungstate were calculated employing the first-principles full potential linearized augmented plane wave (FP-LAPW) method. The results indicate that the principal contributors to the valence band of CdWO{sub 4} are the Cd 4d, W 5d and O 2p states which contribute mainly at the bottom, in the central portion and at the top of the valence band, respectively, with also significant contributions of the mentioned states throughout the whole CdWO{sub 4} valence-band region. With respect to the occupation of the O 2p states, the results of the FP-LAPW calculations are confirmed by comparison on a common energy scale of the XPS valence-band spectrum and the XES band representing the energy distribution of the O 2p states in this compound. Additionally, the FP-LAPW data allow us to conclude that the CdWO{sub 4} tungstate is a non-direct semiconductor. - Highlights: • Large high-quality CdWO{sub 4} crystals, up to 115 mm in diameter and mass up to 20 kg, have been grown. • The high-purity cleaved CdWO{sub 4}(010) surface has been studied by the XPS and XES methods. • The principal contributors to the CdWO{sub 4} valence band are the Cd 4d, W 5d and O 2p states.

  8. Enhanced visible light photocatalytic activity by Cu2O-coupled flower-like Bi2WO6 structures

    NASA Astrophysics Data System (ADS)

    Liu, Li; Ding, Lan; Liu, Yongguang; An, Weijia; Lin, Shuanglong; Liang, Yinghua; Cui, Wenquan

    2016-02-01

    Cu2O nanodots decorated flower-like Bi2WO6 were prepared via an interfacial self-assembly method. The Cu2O nanodots, with an average diameters of 20 nm, were dispersed on the surface of Bi2WO6 uniformly, as evidenced by characterization of the structure and composition. The as-prepared Cu2O/Bi2WO6 hybrid photocatalysts revealed the lower charge-transfer resistance, higher photocurrent intensity and the outstanding photocatalytic activity. The 3 wt% Cu2O/Bi2WO6 composites showed the highest degrade rate for methylene blue (MB), which was 2.14 and 12.25 times that of the pure Bi2WO6 and Cu2O, respectively. Significantly, the superior stability was also observed in the five cyclic runs. The enhanced photocatalytic performance was attributed to the enhancement of visible light absorption efficiency as well as the efficient photo-generated charge separation originated from a strong interaction in the intimately contact interface, which was confirmed by the results of photocurrent and EIS measurements. Based on the experimental results, a mechanisms on enhancement of photocatalytic activity have been emphasized.

  9. Hierarchical Nanostructured WO3 with Biomimetic Proton Channels and Mixed Ionic-Electronic Conductivity for Electrochemical Energy Storage.

    PubMed

    Chen, Zheng; Peng, Yiting; Liu, Fang; Le, Zaiyuan; Zhu, Jian; Shen, Gurong; Zhang, Dieqing; Wen, Meicheng; Xiao, Shuning; Liu, Chi-Ping; Lu, Yunfeng; Li, Hexing

    2015-10-14

    Protein channels in biologic systems can effectively transport ions such as proton (H(+)), sodium (Na(+)), and calcium (Ca(+)) ions. However, none of such channels is able to conduct electrons. Inspired by the biologic proton channels, we report a novel hierarchical nanostructured hydrous hexagonal WO3 (h-WO3) which can conduct both protons and electrons. This mixed protonic-electronic conductor (MPEC) can be synthesized by a facile single-step hydrothermal reaction at low temperature, which results in a three-dimensional nanostructure self-assembled from h-WO3 nanorods. Such a unique h-WO3 contains biomimetic proton channels where single-file water chains embedded within the electron-conducting matrix, which is critical for fast electrokinetics. The mixed conductivities, high redox capacitance, and structural robustness afford the h-WO3 with unprecedented electrochemical performance, including high capacitance, fast charge/discharge capability, and very long cycling life (>50,000 cycles without capacitance decay), thus providing a new platform for a broad range of applications.

  10. Efficient red phosphor double-perovskite Ca3WO6 with A-site substitution of Eu3+.

    PubMed

    Zhao, Xin; Wang, Jiajia; Fan, Li; Ding, Yufeng; Li, Zhaosheng; Yu, Tao; Zou, Zhigang

    2013-10-07

    Luminescent properties of Eu(3+) activated double perovskite structure Ca3WO6 were investigated. It emits an ideal red color centered at the wavelength of 618 nm with suitable excitation from f-f transitions of Eu(3+) ions (360-550 nm) matching the near ultraviolet and blue LEDs. Charge compensation effect of Li(+), Na(+), and K(+) was investigated, and K(+) proved to be the best. The co-doping ion K(+) has a great effect on the lattice distortion of the host matrix Ca3WO6, which facilitates the red emission of Eu(3+). The substitution site for Ca in Ca3WO6 was analyzed in detail by Raman spectra and calculation results. A-site substitution is responsible for the red emission of Eu(3+) activated Ca3WO6. The integrated emission intensity of optimal Ca3WO6:K(+),Eu(3+) excited at 395 nm is about 3.5 times greater than that of Y2O2S:Eu(3+) commercial phosphors, which makes it a promising red phosphor for white LEDs.

  11. Effects of Ti addiction in WO 3 thin film ammonia gas sensor prepared by dc reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Hu, Ming; Yong, Cholyun; Feng, Youcai; Lv, Yuqiang; Han, Lei; Liang, Jiran; Wang, Haopeng

    2006-11-01

    WO 3 sensing films (1500 Å) were deposited using dc reactive magnetron sputtering method on alumina substrate on which patterned interdigital Pt electrodes were previously formed. The additive Ti was sputtered with different thickness (100-500 Å) onto WO 3 thin films and then the films as-deposited were annealed at 400°C in air for 3h. The crystal structure and chemical composition of the films were characterized by XRD and XPS analysis. The effect of Ti addition on sensitive properties of WO 3 thin film to the NH 3 gas was then discussed. WO 3 thin films added Ti revealed excellent sensitivity and response characteristics in the presence of low concentration of NH 3 (5-400 ppm) gas in air at 200°C operating temperature. Especially,in case 300 Å thickness of additive Ti, WO 3 thin films have a promotional effect on the response speed to NH 3 and selectivity enhanced with respect to other gases (CO, C IIH 5OH, CH 4). The influence of different substrates, including alumina, silicon and glass, on sensitivity to NH 3 gas has also been investigated.

  12. Redetermination of the structure of ALa2WO7 (A=Ba, Sr) with fluorite-like metal ordering

    NASA Astrophysics Data System (ADS)

    Fu, W. T.; IJdo, D. J. W.; Bontenbal, A.

    2013-05-01

    The crystal structures of ALa2WO7 (A=Ba, and Sr) at room temperature were re-determined by the Rietveld method using the combined X-ray and neutron powder diffraction data. The compounds are confirmed to be isomorphic, crystallizing in the space group P1121/b. In ALa2WO7 the ordering of metal atoms is fluorite-like, but it differs from that of the fluorite-defect compounds of the formula Ln3MO7 (Ln=lanthanide or Y, M=pentavalent metal). The structure of ALa2WO7 consists of isolated WO6 octahedra, whereas in the normal Ln3MO7 the MO6 octahedra share corners forming one-dimensional chains. Although ALa2WO7 has a centric space group, La ions are not situate at the centre of symmetry, which explains the 5D0→7F2 transition being dominant in emission spectrum of Eu-doped materials.

  13. Localized excitons and defects in PbWO4 single crystals: a luminescence and photo-thermally stimulated disintegration study

    NASA Astrophysics Data System (ADS)

    Krasnikov, A.; Nikl, M.; Zazubovich, S.

    The cover picture refers to the article by Aleksei Krasnikov et al., that was selected as Editor's Choice [1]. It depicts a fragment of a lead tungstate (PbWO4) crystal lattice structure and illustrates the complex anion (WO4)2- tetrahedra bonded to the Pb2+ cation. Perturbation of the (WO4)2- tetrahedra by defects nearby results in exciton localization near the defects and a slightly different emission spectrum, which is shown in the diagram. Localized excitons are evidenced for the first time in the PbWO4 structure. Under selective irradiation of PbWO4 crystals in the ultraviolet spectral region, the decay of various localized excitons into stable defects takes place, which can be detected by a sensitive thermally stimulated luminescence method. Aleksei Krasnikov is a PhD student at the University of Tartu, Estonia. Martin Nikl holds a position as a senior scientist and head of the Laboratory of Luminescence and Scintillation Materials at the Institute of Physics of the Czech Academy of Sciences. Svetlana Zazubovich is a senior scientist at the Institute of Physics, University of Tartu. The research groups of Martin Nikl and Svetlana Zazubovich have been collaborating closely for the last 15 years mainly in the field of optical spectroscopy of wide band-gap scintillation materials

  14. WO3∕SiO2 composite optical films for the fabrication of electrochromic interference filters.

    PubMed

    Baloukas, Bill; Martinu, Ludvik

    2012-06-01

    New security devices based on innovative technologies and ideas are essential in order to limit counterfeiting's profound impact on our economy and society. Interference security image structures have been in circulation for more than 20 years, but commercially available iridescent products now represent a potential threat. Therefore, the introduction of active materials, such as electrochromic WO3, to present-day optical security devices offers interesting possibilities. We have previously proposed electrochromic interference filters based on porous and dense WO3, which possessed an angle-dependent and voltage-driven color shift. However, the low index contrast required filters with a high number of layers. In this article, we increase the index contrast (0.61) by mixing WO3 with SiO2 and study the physical and electrochromic properties of mixtures. We next combine high and low index films in tandem configurations to observe the bleaching/coloration dynamics. To account for the film performance, we propose a simple explanation based on the differences in electron diffusion coefficients. An 11 layer electrochromic interference filter (EIF) based on the alternation of pure WO3 and (WO3)0.17(SiO2)0.83 films with a blue to purple angular color shift is then presented. Finally, we discuss possible applications of these EIFs for security.

  15. Application of Black Pearl carbon-supported WO 3 nanostructures as hybrid carriers for electrocatalytic RuSe x nanoparticles

    NASA Astrophysics Data System (ADS)

    Miecznikowski, Krzysztof; Kulesza, Pawel J.; Fiechter, Sebastian

    2011-07-01

    RuSe x electrocatalytic nanoparticles were deposited onto hybrid carriers composed of Black Pearl carbon-supported tungsten oxide; and the resulting system's electrochemical activity was investigated during oxygen reduction reaction. The tungsten oxide-utilizing and RuSe x nanoparticle-containing materials were characterized using transmission electron microscopy, X-ray diffraction and electrochemical diagnostic techniques such as cyclic voltammetry and rotating ring-disk voltammetry. Application of Black Pearl carbon carriers modified with ultra-thin films of WO 3 as matrices (supports) for RuSe x catalytic centers results during electroreduction of oxygen in 0.5 mol dm -3 H 2SO 4 (under rotating disk voltammetric conditions) in the potential shift of ca. 70 mV towards more positive values relative to the behavior of the analogous WO 3-free system. Also the percent formation (at ring in the rotating ring-disk voltammetry) of the undesirable hydrogen peroxide has been decreased approximately twice by utilizing WO 3-modified carbon carriers. The results are consistent with the bifunctional mechanism in which oxygen reduction is initiated at RuSe x centers and the hydrogen peroxide intermediate is reductively decomposed at reactive WO 3-modified Black Pearl supports. The electrocatalytic activity of the system utilizing WO 3-modified Black Pearl supports has been basically unchanged upon addition of acetic acid, formic acid or methyl formate to the sulfuric acid supporting electrolyte.

  16. Preparation and characterization of spray deposited n-type WO{sub 3} thin films for electrochromic devices

    SciTech Connect

    Sivakumar, R.; Moses Ezhil Raj, A.; Subramanian, B.; Jayachandran, M.; Trivedi, D.C.; Sanjeeviraja, C

    2004-08-03

    The n-type tungsten oxide (WO{sub 3}) polycrystalline thin films have been prepared at an optimized substrate temperature of 250 deg. C by spray pyrolysis technique. Precursor solution of ammonium tungstate ((NH{sub 4}){sub 2}WO{sub 4}) was sprayed onto the well cleaned, pre-heated fluorine doped tin oxide coated (FTO) and glass substrates with a spray rate of 15 ml/min. The structural, surface morphological and optical properties of the as-deposited WO{sub 3} thin films were studied. Mott-Schottky (M-S) studies of WO{sub 3}/FTO electrodes were conducted in Na{sub 2}SO{sub 4} solution to identify their nature and extract semiconductor parameters. The electrochromic properties of the as-deposited and lithiated WO{sub 3}/FTO thin films were analyzed by employing them as working electrodes in three electrode electrochemical cell using an electrolyte containing LiClO{sub 4} in propylene carbonate (PC) solution.

  17. Porous Au-embedded WO3 Nanowire Structure for Efficient Detection of CH4 and H2S

    PubMed Central

    Minh Vuong, Nguyen; Kim, Dojin; Kim, Hyojin

    2015-01-01

    We developed a facile method to fabricate highly porous Au-embedded WO3 nanowire structures for efficient sensing of CH4 and H2S gases. Highly porous single-wall carbon nanotubes were used as template to fabricate WO3 nanowire structures with high porosity. Gold nanoparticles were decorated on the tungsten nanowires by dipping in HAuCl4 solution, followed by oxidation. The surface morphology, structure, and electrical properties of the fabricated WO3 and Au-embedded WO3 nanowire structures were examined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and current–voltage measurements. Formation of a nanowire structure resulted in significant enhancement in sensing response to H2S and CH4 gases. Furthermore, Au embedment into the WO3 nanowire structures remarkably improved the performance of the sensors. The increase in response performance of sensors and adsorption–desorption kinetic processes on the sensing layers were discussed in relation with the role of Au embedment. PMID:26087355

  18. Preparation and optimization of CdWO4-polymer nano-composite film as an alpha particle counter

    NASA Astrophysics Data System (ADS)

    Ziluei, Hossein; Azimirad, Rouhollah; Mojtahedzadeh Larijani, Majid; Ziaie, Farhoud

    2017-04-01

    In this research work, CdWO4/polymer composite films with different thicknesses were prepared using Poly-methyl acrylate polymer and synthesized CdWO4 powder. The CdWO4 powder was synthesized by a simple co-precipitation method in the laboratory. X-ray diffraction, photoluminescence, Fourier transformed infrared spectroscopy and energy-dispersive X-ray spectroscopy proved that the CdWO4 powder was successfully prepared. Moreover, photoluminescence analysis showed that adding polymer does not change the emission peak of CdWO4. Also, the responses of all samples were measured using an 241Am alpha source with 1860 Bq activity. Results showed that the sample having thickness of 177 mg/cm2 has the best counting efficiency (over 2π geometry) among the others. The efficiency measurement was further evaluated using a 230Th source whose activity is 190.7 Bq. It revealed that the counting efficiency of this sample for both 241Am and 230Th was nearly equal.

  19. Mo incorporation in WO{sub 3} thin film photoanodes: Tailoring the electronic structure for photoelectrochemical hydrogen production

    SciTech Connect

    Baer, M.; Weinhardt, L.; Marsen, B.; Cole, B.; Gaillard, N.; Miller, E.; Heske, C.

    2010-01-18

    The electronic surface structure of Mo-incorporated WO{sub 3} (''WO{sub 3}:Mo'') is investigated using direct and inverse photoemission and compared to that of pure (Mo-free) WO{sub 3}. The films are found to be n-type with an electronic surface band gap of 3.27 (+-0.15) eV. The conduction band minimum (valence band maximum) is 0.64 (+-0.10) eV above [2.63 (+-0.10) eV below] the Fermi level and at most 0.38 (+-0.11) eV above the H{sup +}/H{sub 2} reduction potential [at least 1.66 (+-0.11) eV below the H{sub 2}O/O{sub 2} oxidation potential]. The findings suggest an explanation why WO{sub 3}:Mo/WO{sub 3} bilayer structures show improved photoelectrochemical performance compared to respective single layer photoanodes.

  20. Structural and electronic engineering of 3DOM WO3 by alkali metal doping for improved NO2 sensing performance.

    PubMed

    Wang, Zhihua; Fan, Xiaoxiao; Han, Dongmei; Gu, Fubo

    2016-05-19

    Novel alkali metal doped 3DOM WO3 materials were prepared using a simple colloidal crystal template method. Raman, XRD, SEM, TEM, XPS, PL, Hall and UV-Vis techniques were used to characterize the structural and electronic properties of all the products, while the corresponding sensing performances targeting ppb level NO2 were determined at different working temperatures. For the overall goal of structural and electronic engineering, the co-effect of structural and electronic properties on the improved NO2 sensing performance of alkali metal doped 3DOM WO3 was studied. The test results showed that the gas sensing properties of 3DOM WO3/Li improved the most, with the fast response-recovery time and excellent selectivity. More importantly, the response of 3DOM WO3/Li to 500 ppb NO2 was up to 55 at room temperature (25 °C). The especially high response to ppb level NO2 at room temperature (25 °C) in this work has a very important practical significance. The best sensing performance of 3DOM WO3/Li could be ascribed to the most structure defects and the highest carrier mobility. And the possible gas sensing mechanism based on the model of the depletion layer was proposed to demonstrate that both structural and electronic properties are responsible for the NO2 sensing behavior.

  1. Electrical characterization of H{sub 2}S adsorption on hexagonal WO{sub 3} nanowire at room temperature

    SciTech Connect

    Liu, Binquan; Tang, Dongsheng Zhou, Yong; Yin, Yanling; Peng, Yuehua; Zhou, Weichang; Qin, Zhu'ai; Zhang, Yong

    2014-10-28

    We have characterized the electrical transport properties of Au/WO{sub 3} nanowire/Au devices in ambient air and gaseous H{sub 2}S to investigate the adsorption kinetics of H{sub 2}S molecules on the surface of WO{sub 3} nanowire at room temperature. The WO{sub 3} nanowire devices exhibit increasing linear conductance and electrical hysteresis in H{sub 2}S. Furthermore, the contact type between Au electrode and WO{sub 3} nanowire can be converted from original ohmic/Schottky to Schottky/ohmic after being exposed to H{sub 2}S. These results suggest that adsorbed H{sub 2}S molecules are oxidized by holes to form hydrogen ions and S atoms, which will result in formation of hydrogen tungsten bronze and desorption of previously chemically adsorbed H{sub 2}O molecules. Adsorbed H{sub 2}S molecules can also oxidize previously adsorbed and ionized oxygen, which will release the electrons from the ionized oxygen and then weaken upward band bending at the surface of WO{sub 3} nanowire.

  2. Oxygen vacancy induced Bi2WO6 for the realization of photocatalytic CO2 reduction over the full solar spectrum: from the UV to the NIR region.

    PubMed

    Kong, Xin Ying; Choo, Yen Yee; Chai, Siang-Piao; Soh, Ai Kah; Mohamed, Abdul Rahman

    2016-12-06

    Photocatalytic CO2 reduction over the UV-Vis-NIR broad spectrum was realized for the first time. The presence of surface oxygen vacancy defects on Bi2WO6 resulted in significant photocatalytic enhancement over the pristine counterpart under UV and visible light irradiation. Meanwhile, the photocatalytic responsiveness of Bi2WO6-OV was successfully extended to the NIR region.

  3. In situ synthesis of Bi2S3 sensitized WO3 nanoplate arrays with less interfacial defects and enhanced photoelectrochemical performance

    PubMed Central

    Liu, Canjun; Yang, Yahui; Li, Wenzhang; Li, Jie; Li, Yaomin; Chen, Qiyuan

    2016-01-01

    In this study, Bi2S3 sensitive layer has been grown on the surface of WO3 nanoplate arrays via an in situ approach. The characterization of samples were carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and ultraviolet–visible absorption spectroscopy (UV-vis). The results show that the Bi2S3 layer is uniformly formed on the surface of WO3 nanoplates and less interfacial defects were observed in the interface between the Bi2S3 and WO3. More importantly, the Bi2S3/WO3 films as photoanodes for photoelectrochemical (PEC) cells display the enhanced PEC performance compared with the Bi2S3/WO3 films prepared by a sequential ionic layer adsorption reaction (SILAR) method. In order to understand the reason for the enhanced PEC properties, the electron transport properties of the photoelectrodes were studied by using the transient photocurrent spectroscopy and intensity modulated photocurrent spectroscopy (IMPS). The Bi2S3/WO3 films prepared via an in situ approach have a greater transient time constant and higher electron transit rate. This is most likely due to less interfacial defects for the Bi2S3/WO3 films prepared via an in situ approach, resulting in a lower resistance and faster carrier transport in the interface between WO3 and Bi2S3. PMID:26988275

  4. Facile fabrication of crack-free large-area 2D WO3 inverse opal films by a 'dynamic hard-template' strategy on ITO substrates.

    PubMed

    Li, Hua; Thériault, Jolaine; Rousselle, Bruno; Subramanian, Balaji; Robichaud, Jacques; Djaoued, Yahia

    2014-02-28

    A 'dynamic hard-template' infiltration strategy for crack-free large-area synthesis of 2D WO3 inverse opal (IO) films on ITO substrates using a wide range of sizes of sacrificial PS spheres is reported. Thus prepared WO3 IO films were successfully used as an active electrode in the fabrication of an electrochromic device.

  5. In situ synthesis of Bi2S3 sensitized WO3 nanoplate arrays with less interfacial defects and enhanced photoelectrochemical performance

    NASA Astrophysics Data System (ADS)

    Liu, Canjun; Yang, Yahui; Li, Wenzhang; Li, Jie; Li, Yaomin; Chen, Qiyuan

    2016-03-01

    In this study, Bi2S3 sensitive layer has been grown on the surface of WO3 nanoplate arrays via an in situ approach. The characterization of samples were carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and ultraviolet–visible absorption spectroscopy (UV-vis). The results show that the Bi2S3 layer is uniformly formed on the surface of WO3 nanoplates and less interfacial defects were observed in the interface between the Bi2S3 and WO3. More importantly, the Bi2S3/WO3 films as photoanodes for photoelectrochemical (PEC) cells display the enhanced PEC performance compared with the Bi2S3/WO3 films prepared by a sequential ionic layer adsorption reaction (SILAR) method. In order to understand the reason for the enhanced PEC properties, the electron transport properties of the photoelectrodes were studied by using the transient photocurrent spectroscopy and intensity modulated photocurrent spectroscopy (IMPS). The Bi2S3/WO3 films prepared via an in situ approach have a greater transient time constant and higher electron transit rate. This is most likely due to less interfacial defects for the Bi2S3/WO3 films prepared via an in situ approach, resulting in a lower resistance and faster carrier transport in the interface between WO3 and Bi2S3.

  6. Construction of 3D V2O5/hydrogenated-WO3 nanotrees on tungsten foil for high-performance pseudocapacitors.

    PubMed

    Wang, Fengmei; Li, Yuanchang; Cheng, Zhongzhou; Xu, Kai; Zhan, Xueying; Wang, Zhenxing; He, Jun

    2014-06-28

    3D semiconductor nanostructures have proved to be a rich system for the exploring of high-performance pseudocapacitors. Herein, a novel 3D WO3 nanotree on W foil is developed via a facile and green method. Both capacitance and conductivity of the WO3 nanotree electrode are greatly improved after hydrogenation treatment (denoted as H-WO3). First-principles calculation based on the experiments reveals the mechanism of the hydrogenation treatment effect on the 3D WO3 nanotrees. The surface O of 3D WO3 nanotrees gains electrons from the adsorbed H, and consequently certain electrons are back-donated to the neighboring W, thus providing the conducting channel on the surface. Ultrathin V2O5 films were coated on the H-WO3 nanotrees via a simple, low-cost, environmentally friendly electrochemical technique. This V2O5/H-WO3 electrode exhibited a remarkable specific capacitance of 1101 F g(-1) and an energy density of 98 W h kg(-1). The solid-state device based on the V2O5/H-WO3 electrodes shows excellent stability and practical application. Our work opens up the potential broad application of hydrogenation treatment of semiconductor nanostructures in pseudocapacitors and other energy storage devices.

  7. Crystallization and photoluminescence properties of α-RE2(WO4)3 (RE: Gd, Eu) in rare-earth tungsten borate glasses

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Honma, Tsuyoshi; Komatsu, Takayuki

    2013-03-01

    Glasses with the compositions of 22.5RE2O3-47.5WO3-30B2O3 (mol%) (RE: Gd, Eu) were prepared by a conventional melt quenching method, and α-Gd2(WO4)3 and α-Eu2(WO4)3 crystals were synthesized through their crystallization. The two types of WO4 tetrahedra present in α-RE2(WO4)3 provide the Raman bands at 931-934 cm-1 for WIIO4 tetrahrdra with much distortions and at 946-950 cm-1 for WIO4 tetrahedra with a near regular symmetry. The crystallized samples containing α-Eu2(WO4)3 exhibit strong red emissions under the excitation at 396 and 467 nm, although the base glass has no photoluminescence emission. α-Gd2(WO4)3 and α-Eu2(WO4)3 crystals were patterned on the glass surface by irradiations of a continuous wave Yb:YVO4 fiber laser (wavelength: 1080 nm).

  8. Simultaneous Synthesis of WO3-x Quantum Dots and Bundle-Like Nanowires Using a One-Pot Template-Free Solvothermal Strategy and Their Versatile Applications.

    PubMed

    Wang, Yao; Wang, Xiaoxia; Xu, Yuanhong; Chen, Tao; Liu, Mengli; Niu, Fushuang; Wei, Shuang; Liu, Jingquan

    2017-04-01

    Tungsten oxide (WO3-x ), a new alternative to conventional semiconductor material, has attracted numerous attentions owning to its widespread potential applications. Various methods have been reported for the synthesis of WO3-x nanostructures such as nanowires or nanodots. However, templates or surfactants are often required for the synthesis, which significantly complicate the process and hinder the broad applications. Herein, one-pot template/surfactant-free solvothermal method is proposed to synthesize the WO3-x nanostructures including fluorescent quantum dots (QDs) and bundle-like nanowires simultaneously. The as-prepared WO3-x QDs can be well dispersed in aqueous medium, exhibit excellent photoluminescent properties, and show an average size of 3.25 ± 0.25 nm as evidenced by transmission electron microscopy. Meanwhile, the diameter of the WO3-x nanowires is found to be about 27.5 nm as manifested by the scanning electron microscope images. The generation mechanism for these two WO3-x nanostructures are systematically studied and proposed. The WO3-x QDs have been successfully applied in efficient fluorescent staining and specific ferric ion detection. Moreover, the WO3-x nanowires can be utilized as effective dielectric materials for electromagnetic wave absorption.

  9. Effect of WO3 nanoparticle loading on the microstructural, mechanical and corrosion resistance of Zn matrix/TiO2-WO3 nanocomposite coatings for marine application

    NASA Astrophysics Data System (ADS)

    Popoola, A. P. I.; Daniyan, A. A.; Umoru, L. E.; Fayomi, O. S. I.

    2017-03-01

    In this study, for marine application purposes, we evaluated the effect of process parameter and particle loading on the microstructure, mechanical reinforcement and corrosion resistance properties of a Zn-TiO2-WO3 nanocomposite produced via electrodeposition. We characterized the morphological properties of the composite coatings with a Scanning Electron Microscope (SEM) equipped with an Energy Dispersive Spectrometer (EDS). We carried out mechanical examination using a Dura Scan hardness tester and a CERT UMT-2 multi-functional tribological tester. We evaluated the corrosion properties by linear polarization in 3.5% NaCl. The results show that the coatings exhibited good stability and the quantitative particle loading greatly enhanced the structural and morphological properties, hardness behavior and corrosion resistance of the coatings. We observed the precipitation of this alloy on steel is greatly influenced by the composite characteristics.

  10. Effect of WO3 nanoparticle loading on the microstructural, mechanical and corrosion resistance of Zn matrix/TiO2-WO3 nanocomposite coatings for marine application

    NASA Astrophysics Data System (ADS)

    Popoola, A. P. I.; Daniyan, A. A.; Umoru, L. E.; Fayomi, O. S. I.

    2017-01-01

    In this study, for marine application purposes, we evaluated the effect of process parameter and particle loading on the microstructure, mechanical reinforcement and corrosion resistance properties of a Zn-TiO2-WO3 nanocomposite produced via electrodeposition. We characterized the morphological properties of the composite coatings with a Scanning Electron Microscope (SEM) equipped with an Energy Dispersive Spectrometer (EDS). We carried out mechanical examination using a Dura Scan hardness tester and a CERT UMT-2 multi-functional tribological tester. We evaluated the corrosion properties by linear polarization in 3.5% NaCl. The results show that the coatings exhibited good stability and the quantitative particle loading greatly enhanced the structural and morphological properties, hardness behavior and corrosion resistance of the coatings. We observed the precipitation of this alloy on steel is greatly influenced by the composite characteristics.

  11. Synthesis, energy transfer and luminescence properties of Ca{sub 2}MgWO{sub 6}:Sm{sup 3+}, Bi{sup 3+} phosphor

    SciTech Connect

    Cao, Renping; Xu, Haidong; Luo, Wenjie; Luo, Zhiyang; Guo, Siling; Xiao, Fen; Ao, Hui

    2016-09-15

    Graphical abstract: PL spectra of Ca{sub 2}MgWO{sub 6}:Sm{sup 3+} and Ca{sub 2}MgWO{sub 6}:Sm{sup 3+}, Bi{sup 3+} phosphors with excitation at 407 nm, and the corresponding CIE chromaticity diagram and chromaticity coordinates. - Highlights: • Novel Ca{sub 2}MgWO{sub 6}:Sm{sup 3+}, Bi{sup 3+} phosphor is synthesized by solid-state reaction method in air. • Emission intensity of Ca{sub 2}MgWO{sub 6}:Sm{sup 3+} phosphor is enhanced ∼2 times after co-doped Bi{sup 3+} ion. • Charge compensation and energy transfer may be explained via luminescence properties. • Luminous mechanism is analyzed by energy level diagrams of WO{sub 6}{sup 6−} group, Sm{sup 3+} and Bi{sup 3+} ions. - Abstract: Novel Ca{sub 2}MgWO{sub 6}:Sm{sup 3+}, Bi{sup 3+} phosphor is synthesized by solid-state reaction method in air. Host Ca{sub 2}MgWO{sub 6} with excitation 300 nm emits blue light. Ca{sub 2}MgWO{sub 6}:Bi{sup 3+} phosphor with excitation 300 and 338 nm emits yellow light. Ca{sub 2}MgWO{sub 6}:Sm{sup 3+} phosphor with excitation 300 nm exhibits tunable emission from blue to red light by increasing Sm{sup 3+} doping concentration from 0 to 8 mol%, however, only emits red light with excitation 407 nm. Ca{sub 2}MgWO{sub 6}:Sm{sup 3+}, Bi{sup 3+} phosphor with excitation 300 and 338 nm emits red light. The optimal Sm{sup 3+} doping concentration is ∼5 mol% in Ca{sub 2}MgWO{sub 6}:Sm{sup 3+} phosphor. After Bi{sup 3+} ion is co-doped, luminescence properties of Ca{sub 2}MgWO{sub 6}:Sm{sup 3+} phosphor can be improved obviously because of Bi{sub 2}O{sub 3} as fluxing agent role and energy transfer from Bi{sup 3+} to Sm{sup 3+} ions. The possible luminous mechanism of Ca{sub 2}MgWO{sub 6}:Sm{sup 3+}, Bi{sup 3+} phosphor is analyzed and explained by simplified energy level diagrams of WO{sub 6}{sup 6−} group, Bi{sup 3+} and Sm{sup 3+} ions.

  12. Hollow Sodium Tungsten Bronze (Na0.15WO3) Nanospheres: Preparation, Characterization, and Their Adsorption Properties

    PubMed Central

    2009-01-01

    We report herein a facile method for the preparation of sodium tungsten bronzes hollow nanospheres using hydrogen gas bubbles as reactant for chemical reduction of tungstate to tungsten and as template for the formation of hollow nanospheres at the same time. The chemical composition and the crystalline state of the as-prepared hollow Na0.15WO3nanospheres were characterized complementarily, and the hollow structure formation mechanism was proposed. The hollow Na0.15WO3nanospheres showed large Brunauer–Emment–Teller specific area (33.8 m2 g−1), strong resistance to acids, and excellent ability to remove organic molecules such as dye and proteins from aqueous solutions. These illustrate that the hollow nanospheres of Na0.15WO3should be a useful adsorbent. PMID:20596394

  13. White Lighting Upconversion in Tm3+/Ho3+/Yb3+ Co-Doped CaWO4

    NASA Astrophysics Data System (ADS)

    Chung, Jun Ho; Yeop Lee, Sang; Shim, Kwang Bo; Ryu, Jeong Ho

    2012-05-01

    Controllable white upconversion (UC) luminescence was obtained from Tm3+/Ho3+/Yb3+-codoped CaWO4. Under the excitation of a 980 nm single wavelength laser diode, the Tm3+/Ho3+/Yb3+-codoped CaWO4 exhibited bright white UC luminescence composed of blue emission from Tm3+ and green and red emissions from Ho3+ visible to the naked eye. The intensity ratios of green, red, and blue UC emissions varied with Tm3+/Ho3+ concentrations, which can control white UC emission ranging from the cool to the warm region. Various white UC colors can be easily changed by adjusting the Tm3+/Ho3+ concentrations in the CaWO4 matrix.

  14. Facile synthesis of Bi2WO6/Bi2O3-loaded polyurethane sponge with enhanced visible light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Zhang, Fengjun; Wang, Zhi; Wang, Tianye; Jia, Liwei; Wang, Chao; Zhang, Shengyu

    2016-03-01

    In this study, Bi2WO6/Bi2O3-loaded polyurethane sponge composite photocatalyst was successfully synthesized via a facile two-step approach. The composite was characterized by X-ray diffraction, ultraviolet-visible diffuse reflectance, and scanning electron microscopy. The Bi2WO6/Bi2O3 photocatalyst was successfully loaded on polyurethane sponge and the composite displayed enhanced absorption in the ultraviolet-to-visible light region. Furthermore, the composite exhibited enhanced photocatalytic activity and reusability towards the degradation of rhodamine B (RhB) under visible light. This work demonstrates a facile method for synthesizing Bi2WO6/Bi2O3-loaded polyurethane sponge with enhanced photocatalytic activity and easy immobilization of the photocatalyst for application in environmental purification.

  15. Hollow Sodium Tungsten Bronze (Na0.15WO3) Nanospheres: Preparation, Characterization, and Their Adsorption Properties.

    PubMed

    Hou, Jing; Zuo, Guanke; Shen, Guangxia; Guo, He; Liu, Hui; Cheng, Ping; Zhang, Jingyan; Guo, Shouwu

    2009-07-17

    We report herein a facile method for the preparation of sodium tungsten bronzes hollow nanospheres using hydrogen gas bubbles as reactant for chemical reduction of tungstate to tungsten and as template for the formation of hollow nanospheres at the same time. The chemical composition and the crystalline state of the as-prepared hollow Na0.15WO3nanospheres were characterized complementarily, and the hollow structure formation mechanism was proposed. The hollow Na0.15WO3nanospheres showed large Brunauer-Emment-Teller specific area (33.8 m2 g-1), strong resistance to acids, and excellent ability to remove organic molecules such as dye and proteins from aqueous solutions. These illustrate that the hollow nanospheres of Na0.15WO3should be a useful adsorbent.

  16. Insulator-to-metal transition of WO3 epitaxial films induced by electrochemical Li-ion intercalation

    NASA Astrophysics Data System (ADS)

    Yoshimatsu, Kohei; Soma, Takuto; Ohtomo, Akira

    2016-07-01

    We investigated the systematic evolution of the structural and electronic properties of Li x WO3 films induced by Li-ion electrochemical reactions. Chronoamperometric Li-ion intercalation could control the Li content up to x ∼ 0.5. The resistivity decreased abruptly with increasing x, and the films underwent an insulator-to-metal transition (IMT) within a range of 0.2 < x < 0.24, which was consistent with the IMT of cubic Na x WO3. X-ray diffraction analyses revealed the coexistence of tetragonal and cubic phases across the IMT, suggesting that the alkaline ion content was the primary factor in the metallic conductivity of the ReO3-type WO3 system.

  17. WO3/Pt nanoparticles are NADPH oxidase biomimetics that mimic effector cells in vitro and in vivo

    NASA Astrophysics Data System (ADS)

    Clark, Andrea J.; Coury, Emma L.; Meilhac, Alexandra M.; Petty, Howard R.

    2016-02-01

    To provide a means of delivering an artificial immune effector cell-like attack on tumor cells, we report the tumoricidal ability of inorganic WO3/Pt nanoparticles that mimic a leukocyte’s functional abilities. These nanoparticles route electrons from organic structures and electron carriers to form hydroxyl radicals within tumor cells. During visible light exposure, WO3/Pt nanoparticles manufacture hydroxyl radicals, degrade organic compounds, use NADPH, trigger lipid peroxidation, promote lysosomal membrane disruption, promote the loss of reduced glutathione, and activate apoptosis. In a model of advanced breast cancer metastasis to the eye’s anterior chamber, we show that WO3/Pt nanoparticles prolong the survival of 4T1 tumor-bearing Balb/c mice. This new generation of inorganic photosensitizers do not photobleach, and therefore should provide an important therapeutic advance in photodynamic therapy. As biomimetic nanoparticles destroy targeted cells, they may be useful in treating ocular and other forms of cancer.

  18. A ternary TiO2/WO3/graphene nanocomposite adsorbent: facile preparation and efficient removal of Rhodamine B

    NASA Astrophysics Data System (ADS)

    Zhang, Yong-qiang; Li, Xiao-hui; Lü, Jie; Si, Chong-dian; Liu, Guang-jun; Gao, Hong-tao; Wang, Pi-bo

    2014-08-01

    Ternary TiO2/WO3/graphene (TWG) nanocomposites were prepared by a facile salt-ultrasonic assisted hydrothermal method. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption. Both anatase TiO2 and orthorhombic WO3 formed in the nanocomposites, along with a highly disordered overlay of individual graphene nanosheets. Polyhedral and spherical TiO2 and WO3 nanoparticles of uniform size 10-30 nm were densely anchored to the graphene sheets. The maximum specific surface area of the products was 144.59 m2·g-1. The products showed clear abilities for the removal of Rhodamine B in the absence of illumination. Furthermore, the adsorption activity of the products exhibited only a slight decrease after three successive cycles. The results demonstrate that the ternary nanocomposites could be used as a high-efficiency adsorbent for the removal of environmental contaminants.

  19. Exchange-Induced Negative-U Charge Order in N-Doped WO3: A Spin-Peierls-Like System

    SciTech Connect

    Huda, M. N.; Yan, Y.; Wei, S.-H.; Al-Jassim, M. M.

    2009-01-01

    An unconventional spin-Peierls-type distortion was found in a nonmagnetic atom N doped pseudo-one-dimensional WO{sub 3} system. The periodicity of the initial ferromagnetic WO{sub 3}:N is doubled in one direction, and the band gap opens up due to this distortion. The magnetic moment at the N site is asymmetric in the distorted system, and the interaction between the localized spin is very weak. We show that the large exchange interaction of the nitrogen 2p atomic orbital and the pseudo-one-dimensional W-O-W chain in monoclinic WO{sub 3} structure is the origin of this spin-Peierls-like transition that leads to the stabilization of an unusual negative-U charge-ordered system.

  20. Heterogeneous photo-Fenton decolorization of methylene blue over LiFe(WO4)2 catalyst.

    PubMed

    Ji, Fei; Li, Chaolin; Zhang, Jiahuan; Deng, Lei

    2011-02-28

    Heterogeneous photo-Fenton process using LiFe(WO(4))(2) as catalyst was studied to degrade Methylene blue (MB) dye in aqueous solution. The results indicated that LiFe(WO(4))(2) could effectively catalyze the decolorization of MB in the presence of UV light and H(2)O(2). The effects of different parameters such as amounts of catalyst, H(2)O(2) concentration, initial pH of the dye solution, initial dye concentration and UV light intensity on the decolorization efficiency of the process were investigated. It was found that LiFe(WO(4))(2) possessed a wide applicable pH range. X-ray photoelectron spectroscopy (XPS) was applied to investigate the transformation between Fe(III) and Fe(II). It was also observed that catalytic behavior could be reproduced in consecutive experiments without a considerable drop in the process efficiency.

  1. In-situ observation of self-regulated switching behavior in WO{sub 3-x} based resistive switching devices

    SciTech Connect

    Hong, D. S.; Wang, W. X.; Chen, Y. S. Sun, J. R.; Shen, B. G.

    2014-09-15

    The transmittance of tungsten oxides can be adjusted by oxygen vacancy (V{sub o}) concentration due to its electrochromic property. Here, we report an in-situ observation of resistive switching phenomenon in the oxygen-deficient WO{sub 3-x} planar devices. Besides directly identifying the formation/rupture of dark-colored conductive filaments in oxide layer, the stripe-like WO{sub 3-x} device demonstrated self-regulated switching behavior during the endurance testing, resulting in highly consistent switching parameters after a stabilizing process. For very high V{sub o}s mobility was demonstrated in the WO{sub 3-x} film by the pulse experiment, we suggested that the electric-field-induced homogeneous migration of V{sub o}s was the physical origin for such unique switching characteristics.

  2. Surface characterization studies on the interaction of V2O5-WO3/TiO2 catalyst for low temperature SCR of NO with NH3

    NASA Astrophysics Data System (ADS)

    Zhang, Shule; Zhong, Qin

    2015-01-01

    This study aimed at elucidating the surface characterization of V2O5-WO3/TiO2 catalyst to investigate the interaction of V, W and Ti species for the improvement of the catalytic activity in the SCR reaction at low-temperature. Analysis by XRD, UV-vis, PL spectra and DFT theoretical calculations, XPS, EPR and in situ DRIFT showed that WO3 could interact with TiO2 to improve the electrons transfer, and the WO3 hybridization with V2O5 could also improve the reducibility and formation of reduced V2O5 species for the V2O5-WO3/TiO2 catalyst. These aspects resulted in the NO oxidation and NO3 - decomposition that were responsible for the high catalytic activity of V2O5-WO3/TiO2 catalyst.

  3. Enhanced photoelectric conversion efficiency of dye sensitized solar cells via the incorporation of one dimensional luminescent BaWO4:Eu(3+) nanowires.

    PubMed

    Wang, Yuping; Qu, Yang; Pan, Kai; Wang, Guofeng; Li, Yadong

    2016-09-25

    One dimensional hierarchical BaWO4:Eu(3+) nanowires have been prepared via a hydrothermal method for the first time. The obtained BaWO4:Eu(3+) nanowires are not only a promising down-conversion luminescence material, but also can be used to improve the efficiency of dye sensitized solar cells, resulting an efficiency of 7.66%, which is a noticeable enhancement of 15% compared to the cell without BaWO4:Eu(3+) nanowires. We suggest that the enhancement of the efficiencies of the TiO2-BaWO4:Eu(3+) composite cells was mainly related to the light scattering of BaWO4:Eu(3+).

  4. Charge Density Wave and Crystal Structure of KxWO3 (x=0.20 and 0.22) Prepared by Hybrid Microwave Method

    NASA Astrophysics Data System (ADS)

    Chen, Runze; Gao, Chaojun; Bu, Kun; Hao, Xiaoyu; Wang, Zichen; Wen, Lianjun; Guo, Juan; Chao, Mingju; Liang, Erjun; Yang, Lihong; Dong, Cheng

    2017-02-01

    Potassium tungsten bronzes KxWO3 (x=0.20 and 0.22) with the coexistence of charge density wave (CDW) and superconductivity (SC) were prepared from K2WO4, WO3 and W powders using a hybrid microwave method. The structure refinement confirmed that all samples had a pure hexagonal phase with the space group of P63 /mcm. The distortion degree of W-O octahedron declines with x and is independent of synthesis condition for the same x (=0.20). The CDW transition is studied as a function of residual resistivity ratio. By increasing the crystallinity of sample, this transition can be suppressed, which is probably attributed to the interaction between CDW and defects in crystallites. The CDW transition temperature increases with x, which may be related to the decline of the distortion degree of W-O octahedron. The competition between CDW and SC is observed according to the resistivity and magnetization measurements.

  5. [Growth of codoped CdWO4 crystals by Bridgman method and their optical spectra].

    PubMed

    Yu, Can; Xia, Hai-Ping; Wang, Dong-Jie; Chen, Hong-Bing

    2011-09-01

    The CdWO4 crystals with good quality in the size of Phi25 mm x 120 mm, doped with Co in 0.5% molar fraction in the raw composition, were grown by the Bridgman method by taking -70 degrees C x cm(-1) of solid-liquid interface and -0.50 mm x h(-1) growth rate. The crystal presents transparence and deep blue. The X-ray diffraction (XRD) was used to characterize the crystals. Three absorption peaks at 518, 564 and 655 nm respectively, which are attributed to the overlapping of 4 T1 (4F) --> 4A2 (4F) and 4 T1 (4F) --> 4 T1 (4P) of Co2+ octahedrons, and a wide band centered at 1 863 nm, which is attributed to 4Ti (4F) --> 4 T2 (4F), was observed. The absorption results indicated that the Co ions presented +2 valence in crystal and located within the distorted oxygen octahedrons. The crystal-field parameter D(q) and the Racah parameter B were estimated to be 990 and 726.3 cm(-1) respectively based on the absorption spectra. A fluorescence emission at 778 nm (4T1 (4P) --> 4 T1 (4F)) for codoped CdWO4 crystals was observed under excitation by 520 nm light. It can be deduced from the changes in absorption and emission intensity of different parts of crystal that the concentration of Co2+ ion in crystal increased along growing direction and the effective distribution coefficient of Co2+ ion in CdWO4 crystal is less than 1.

  6. A New Prescription for the Mass-loss Rates of WC and WO Stars

    NASA Astrophysics Data System (ADS)

    Tramper, F.; Sana, H.; de Koter, A.

    2016-12-01

    We present a new empirical prescription for the mass-loss rates of carbon- and oxygen-sequence Wolf-Rayet stars as a function of their luminosity, surface chemical composition, and initial metallicity. The new prescription is based on results of detailed spectral analyses of WC and WO stars and improves the often applied Nugis and Lamers relation. We find that the mass-loss rates of WC and WO stars (with X = 0 and Y ≲ 0.98) can be expressed as {log} \\dot{M}=-9.20+0.85{log}(L/L ⊙) + 0.44 log Y + 0.25 log (Z Fe/Z Fe,⊙). This relation is based on mass-loss determinations that assume a volume-filling factor of 0.1, but the prescription can easily be scaled to account for other volume-filling factors. The residual of the fit is σ = 0.06 dex. We investigated whether the relation can also describe the mass loss of hydrogen-free WN stars and showed that it can when an adjustment of the metallicity dependence ({log} \\dot{M}\\propto 1.3{log}({Z}{Fe}/{Z}{Fe,⊙ })) is applied. Compared to that of Nugis and Lamers, \\dot{M} is less sensitive to the luminosity and the surface abundance, implying a stronger mass loss of massive stars in their late stages of evolution. The modest metallicity dependence implies that if WC or WO stars are formed in metal-deficient environments, their mass-loss rates are higher than currently anticipated. These effects may result in the formation of a larger number of SNe Ic and fewer black holes and may favor the production of superluminous SNe Ic through interaction with C- and O-rich circumstellar material or dense stellar wind.

  7. Study on the decomposition of trace benzene over V2O5-WO3 ...

    EPA Pesticide Factsheets

    Commercial and laboratory-prepared V2O5–WO3/TiO2-based catalysts with different compositions were tested for catalytic decomposition of chlorobenzene (ClBz) in simulated flue gas. Resonance enhanced multiphoton ionization-time of flight mass spectrometry (REMPI-TOFMS) was employed to measure real-time, trace concentrations of ClBz contained in the flue gas before and after the catalyst. The effects of various parameters, including vanadium content of the catalyst, the catalyst support, as well as the reaction temperature on decomposition of ClBz were investigated. The results showed that the ClBz decomposition efficiency was significantly enhanced when nano-TiO2 instead of conventional TiO2 was used as the catalyst support. No promotion effects were found in the ClBz decomposition process when the catalysts were wet-impregnated with CuO and CeO2. Tests with different concentrations (1,000, 500, and 100 ppb) of ClBz showed that ClBz-decomposition efficiency decreased with increasing concentration, unless active sites were plentiful. A comparison between ClBz and benzene decomposition on the V2O5–WO3/TiO2-based catalyst and the relative kinetics analysis showed that two different active sites were likely involved in the decomposition mechanism and the V=O and V-O-Ti groups may only work for the degradation of the phenyl group and the benzene ring rather than the C-Cl bond. V2O5-WO3/TiO2 based catalysts, that have been used for destruction of a wide variet

  8. Ag/WO3-codoped TiO2 nanoparticles: relation between structure, sorption, and photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Xu, Jing Y.; Wen, Chen; Jia, Li M.; Xiao, Chang F.

    2009-07-01

    Nanostructured Ag/WO3-TiO2 particles responding to sunlight were synthesized by dissolving silver nitrate, sodium tungstate and tetrabutyl titanate precursors in a suitable solvent. The obtained powders were characterized by a series of analytical methods including X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, Zeta potential measurements and UV-vis diffuse reflectance spectra (UV-vis DRS) to demonstrate their physicochemical properties. The as-prepared Ag/WO3-TiO2 samples were evaluated for their photocatalytic activity towards the degradation of methylene blue (MB) under sunlight irradiations. Both silver (Ag) and tungsten (W) species were well dispersed over TiO2 surface with less than 6.0 mol % Ag and 3.0 mol % W to Ti element and contributed to a formation of crystalline WO3. XRD analysis particularly demonstrates the existence of mixed-phase TiO2 materials, to which the improvement in photocatalytic activity is attributed. Besides, the light absorption of doped samples is prominent red shifted relative to the pure TiO2 due to the synergetic effect among the components of Ag, WO3 and TiO2 in the codoped-TiO2. The particle size of the Ag/WO3-TiO2 powders was found to be a decrease which is accompanied with the increase of the surface area. The excellent stability and dispersity of the Ag/WO3-TiO2 powders in aqueous solution could be attributed to the enhanced Zeta potential. On the other hand, the adsorption performances of different samples were tested in the removal of two dyes from aqueous solution(congo red and methylene blue). The first-order adsorption equilibrium constants were determined and the results obtained were fitted by Langmuir monolayer formation. Thus, the Langmuir adsorption isotherm parameters were estimated from the experimental data.

  9. Electron microscopy analyses and electrical properties of the layered Bi{sub 2}WO{sub 6} phase

    SciTech Connect

    Taoufyq, A.; Ait Ahsaine, H.; Patout, L.; Benlhachemi, A.; Ezahri, M.; and others

    2013-07-15

    The bismuth tungstate Bi{sub 2}WO{sub 6} was synthesized using a classical coprecipitation method followed by a calcination process at different temperatures. The samples were characterized by X-ray diffraction, simultaneous thermogravimetry and differential thermal analysis (TGA/DTA), scanning and transmission electron microscopy (SEM, TEM) analyses. The Rietveld analysis and electron diffraction clearly confirmed the Pca2{sub 1} non centrosymmetric space group previously proposed for this phase. The layers Bi{sub 2}O{sub 2}{sup 2+} and WO{sub 4}{sup 2−} have been directly evidenced from the HRTEM images. The electrical properties of Bi{sub 2}WO{sub 6} compacted pellets systems were determined from electrical impedance spectrometry (EIS) and direct current (DC) analyses, under air and argon, between 350 and 700 °C. The direct current analyses showed that the conduction observed from EIS analyses was mainly ionic in this temperature range, with a small electronic contribution. Electrical change above the transition temperature of 660 °C is observed under air and argon atmospheres. The strong conductivity increase observed under argon is interpreted in terms of formation of additional oxygen vacancies coupled with electron conduction. - Graphical abstract: High resolution transmission electron microscopy: inverse fast Fourier transform giving the layered structure of the Bi{sub 2}WO{sub 6} phase, with a representation of the cell dimensions (b and c vectors). The Bi{sub 2}O{sub 2}{sup 2+} and WO{sub 4}{sup 2−} sandwiches are visible in the IFFT image. - Highlights: • Using transmission electron microscopy, we visualize the layered structure of Bi{sub 2}WO{sub 6}. • Electrical analyses under argon gas show some increase in conductivity. • The phase transition at 660 °C is evidenced from electrical modification.

  10. Characterization of phase structures in semiconducting SnWO4 powders by Mössbauer and Raman spectroscopies

    NASA Astrophysics Data System (ADS)

    Solis, J. L.; Frantti, J.; Lantto, V.; Häggström, L.; Wikner, M.

    1998-06-01

    Stannous tungstate, SnWO4, crystallizes in the low-temperature α and high-temperature β phases. α-SnWO4 powders were prepared by heating an equimolar mixture of SnO and WO3 either in vacuum or in argon atmosphere at 600 °C for 15 h. The high-temperature β phase was obtained as metastable at room temperature after heating the mixture at 800 °C and rapid quenching. In addition to x-ray-diffraction studies, 119Sn Mössbauer and Raman spectroscopies were used as ``local'' probes for the characterization of the phase structures in the semiconducting and gas-sensitive powders. The composition of the powders was measured by the energy-dispersive spectroscopy of x rays. Mössbauer spectroscopy, especially, as a very local probe for tin atoms gave valuable information of small extra phase(s) in the α- and β-SnWO4 powders originating in the oxidation of Sn2+ ions in the SnWO4 structures into the Sn4+ form. The Sn2+ Mössbauer doublet from both α and β phases showed some asymmetry not published before. The asymmetry was possible to relate to the Goldanskii-Karyagin effect with calculations based on published results for the atomic positions and thermal displacement parameters in the x-ray temperature factor of the α- and β-SnWO4 structures. Raman spectra are given together with peak frequencies from a curve fit for both α- and β-phase powders. The symmetries and selection rules of the normal modes at the center of the Brillouin zone are also given for both α and β phases.

  11. Phase transformation of lithium tungsten bronzes, Li {sub x}WO{sub 3}, at room temperature ambient conditions

    SciTech Connect

    Dey, K.R.; Ruescher, C.H. . E-mail: C.ruescher@mineralogie.uni-hannover.de; Gesing, Th.M.; Hussain, A.

    2007-04-12

    Samples of Li {sub x}WO{sub 3} with x = 0.05-0.7 were synthesized at 700 deg. C for 7 days using appropriate amounts of Li{sub 2}WO{sub 4}, WO{sub 3} and WO{sub 2} in evacuated sealed silica tubes. The products reveal different phases of perovskite tungsten bronze (PTB). An interesting phenomenon observed for the PTB phases is the gradual change in colours when they are exposed at room temperature ambient conditions (in air). This effect has been investigated using X-ray powder diffraction, infrared absorption and optical reflectivity methods for the powdered samples before and after 30 and 90 days in air. The spectra of the samples with x = 0.25-0.5 are dominated by a peak with maximum around 16,000 cm{sup -1} in the Kubelka Munk spectra which is related to the cubic Li {sub x}WO{sub 3} phase. The peak intensity increases with increasing x. After 30 days of exposure in air this peak disappeared for x < 0.5 samples due to a diffusion of Li from Li {sub x}WO{sub 3}. X-ray and IR data show a gradual transformation into the lower symmetric phases (PTB{sub cubic} {sup {yields}} PTB{sub tetragonal} {sup {yields}} PTB{sub orthorhombic} {sup {yields}} PTB{sub monoclinic}). The results suggest that Li is attracted by O{sub 2} to the surface forming Li{sub 2}O which further reacts with H{sub 2}O and CO{sub 2} in air. The in air altered samples regain their original colour when reheated at 500 deg. C in vacuum.

  12. Unique and facile solvothermal synthesis of mesoporous WO3 using a solid precursor and a surfactant template as a photoanode for visible-light-driven water oxidation

    PubMed Central

    2014-01-01

    Mesoporous tungsten trioxide (WO3) was prepared from tungstic acid (H2WO4) as a tungsten precursor with dodecylamine (DDA) as a template to guide porosity of the nanostructure by a solvothermal technique. The WO3 sample (denoted as WO3-DDA) prepared with DDA was moulded on an electrode to yield efficient performance for visible-light-driven photoelectrochemical (PEC) water oxidation. Powder X-ray diffraction (XRD) data of the WO3-DDA sample calcined at 400°C indicate a crystalline framework of the mesoporous structure with disordered arrangement of pores. N2 physisorption studies show a Brunauer-Emmett-Teller (BET) surface area up to 57 m2 g-1 together with type IV isotherms and uniform distribution of a nanoscale pore size in the mesopore region. Scanning electron microscopy (SEM) images exhibit well-connected tiny spherical WO3 particles with a diameter of ca. 5 to 20 nm composing the mesoporous network. The WO3-DDA electrode generated photoanodic current density of 1.1 mA cm-2 at 1.0 V versus Ag/AgCl under visible light irradiation, which is about three times higher than that of the untemplated WO3. O2 (1.49 μmol; Faraday efficiency, 65.2%) was evolved during the 1-h photoelectrolysis for the WO3-DDA electrode under the conditions employed. The mesoporous electrode turned out to work more efficiently for visible-light-driven water oxidation relative to the untemplated WO3 electrode. PMID:25313301

  13. Optimizing the Replication of Multi-Quality Web Applications Using ACO and WoLF

    DTIC Science & Technology

    2006-09-14

    similar approach was used to merge WoLF with ACS- TSP (an ACO algorithm) to solve a Traveling Salesman Problem in [26]. The variables used for policy update...OPTIMIZING THE REPLICATION OF MULTI-QUALITY WEB APPLICATIONS USING ACO AND WOLF THESIS Judson C Dressler, Second Lieutenant, USAF AFIT/GCS/ENG/06-05...Air Force, Department of Defense, or the U.S. Government. AFIT/GCS/ENG/06-05 OPTIMIZING THE REPLICATION OF MULTI-QUALITY WEB APPLICATIONS USING ACO AND

  14. Crystallographic dependence of photocatalytic activity of WO3 thin films prepared by molecular beam epitaxy.

    PubMed

    Li, Guoqiang; Varga, Tamas; Yan, Pengfei; Wang, Zhiguo; Wang, Chongmin; Chambers, Scott A; Du, Yingge

    2015-06-21

    We investigated the impact of crystallographic orientation on the photocatalytic activity of single crystalline WO3 thin films prepared by molecular beam epitaxy on the photodegradation of rhodamine B (RhB). A clear effect is observed, with (111) being the most reactive surface, followed by (110) and (001). Photoreactivity is directly correlated with the surface free energy determined by density functional theory calculations. The RhB photodegradation mechanism is found to involve hydroxyl radicals in solution formed from photo-generated holes and differs from previous studies performed on nanoparticles and composites.

  15. Epitaxial growth of high quality WO3 thin films

    SciTech Connect

    Leng, X.; Pereiro, J.; Strle, J.; Bollinger, A. T.; Bozovic, I.

    2015-09-09

    We have grown epitaxial WO3 films on various single-crystal substrates using radio-frequency (RF) magnetron sputtering. While pronounced surface roughness is observed in films grown on LaSrAlO4 substrates, films grown on YAlO3 substrates show atomically flat surfaces, as demonstrated by atomic force microscopy (AFM) and X-ray diffraction (XRD) measurements. The crystalline structure has been confirmed to be monoclinic by symmetric and skew-symmetric XRD. Furthermore, the dependence of the growth modes and the surface morphology on the lattice mismatch is discussed.

  16. In vitro transport mechanism of psoralen in a human placental cell line (BeWo cells).

    PubMed

    Guo, Jie; Song, Dianrong; Han, Fang; Zhang, Wei; Wang, Yanan; Wang, Yuhua; Du, Wenxin

    2015-01-01

    The mechanism by which psoralen is transported across the placenta was investigated in the BeWo human placental cell line derived from choriocarcinoma in a transwell assay system using liquid chromatography-mass spectrometry/mass spectrometry detection. Psoralen uptake by BeWo cells increased linearly over the concentration range of 0.01 µM to 100 µM (r (2) = 0.997) and was not saturable. Psoralen uptake by BeWo cells was not affected by temperature (4 °C, room temperature, and 37 °C; p > 0.05). Psoralen transport increased linearly over 180 min (r (2) = 0.988) with 3.08 ± 0.26 %, 5.47 ± 0.21 %, 7.54 ± 0.06 %, 9.40 ± 0.37 %, 11.49 ± 0.31 %, and 12.46 ± 0.61 % transferred from the apical chamber to the basolateral chamber in the transwell assays at 30, 60, 90, 120, 150, and 180 min, respectively. The rate of transport showed the same tendency, increasing linearly from 0.13 ± 0.01 pmol/s to 0.58 ± 0.03 pmol/s over the concentration range of 25 µM to 100 µM (r (2) = 0.989). The apparent permeability coefficient for psoralen (100 µM) was 5.62 ± 0.24 × 10(-6) cm/s and 5.53 ± 0.47 × 10(-6) cm/s before and after treatment with verapamil (100 µM), respectively (p > 0.05). The efflux value for psoralen was approximately 1. These data show that psoralen is well absorbed and crosses the placental barrier via passive diffusion in the BeWo cell line.

  17. Measurement of thermal lensing in a CW BaWO4 intracavity Raman laser.

    PubMed

    Bonner, Gerald M; Pask, Helen M; Lee, Andrew J; Kemp, Alan J; Wang, Jiyang; Zhang, Huaijin; Omatsu, Takashige

    2012-04-23

    The thermal lens induced in an a-cut BaWO(4) crystal by stimulated Raman scattering is measured using lateral shearing interferometry. The strength of the lens is proportional to the Stokes output power. For light polarized parallel to the a-axis, and a Stokes mode radius of 120 μm, the lens is negative and highly astigmatic: -0.8 D W(-1) in the plane parallel to the a-axis and -7.7 D W(-1) in the plane parallel to the c-axis. The implications of this thermal lens for Raman laser design are discussed.

  18. WO{sub 3} thin film based multiple sensor array for electronic nose application

    SciTech Connect

    Ramgir, Niranjan S. E-mail: deepakcct1991@gmail.com; Goyal, C. P.; Datta, N.; Kaur, M.; Debnath, A. K.; Aswal, D. K.; Gupta, S. K.; Goyal, Deepak E-mail: deepakcct1991@gmail.com

    2015-06-24

    Multiple sensor array comprising 16 x 2 sensing elements were realized using RF sputtered WO{sub 3} thin films. The sensor films were modified with a thin layer of sensitizers namely Au, Ni, Cu, Al, Pd, Ti, Pt. The resulting sensor array were tested for their response towards different gases namely H{sub 2}S, NH{sub 3}, NO and C{sub 2}H{sub 5}OH. The sensor response values measured from the response curves indicates that the sensor array generates a unique signature pattern (bar chart) for the gases. The sensor response values can be used to get both qualitative and quantitative information about the gas.

  19. Highly sensitive and stable relative humidity sensors based on WO3 modified mesoporous silica

    NASA Astrophysics Data System (ADS)

    Tomer, Vijay K.; Duhan, Surender

    2015-02-01

    This study investigates the effectiveness of using WO3 loaded mesoporous silica nanocomposite developed using one step hydrothermal method for measuring relative humidity (RH) at room temperature. On measuring the sensing response, the nanocomposite sensor exhibits excellent linearity, negligible hysteresis, swift response and recovery time, good repeatability, and outstanding stability in 11%-98% RH range. The complex impedance spectra of the sensor at different RHs were used to explore the humidity sensing mechanism. This work could encourage a right approach to blueprint practical humidity sensors with high sensitivity, long stability and fast response/recovery time.

  20. Influence of electron beam irradiation on structural and optical properties of α-Ag2WO4 nanoparticles.

    PubMed

    A, Sreedevi; K P, Priyanka; K K, Babitha; S, Ganesh; Varghese, T

    2016-09-01

    The influence of 8MeV electron beam irradiation on the structural and optical properties of silver tungstate (α-Ag2WO4) nanoparticles synthesized by chemical precipitation method was investigated. The dose dependent effect of electron irradiation was investigated by various characterization techniques such as, X-ray diffraction, scanning electron microscopy, UV-vis absorption spectroscopy, photoluminescence and Raman spectroscopy. Systematic studies confirm that electron beam irradiation induces non-stoichiometry, defects and particle size variation on α-Ag2WO4, which in turn results changes in optical band gap, photoluminescence spectra and Raman bands.

  1. Proton intercalated two-dimensional WO3 nano-flakes with enhanced charge-carrier mobility at room temperature

    NASA Astrophysics Data System (ADS)

    Zhuiykov, Serge; Kats, Eugene; Carey, Benjamin; Balendhran, Sivacarendran

    2014-11-01

    Quasi two-dimensional (Q2D) semiconducting metal oxides with enhanced charge carrier mobility hold tremendous promise for nano-electronics, photonics, catalysis, nano-sensors and electrochromic applications. In addition to graphene and metal dichalcogenides MX2 (M = Mo, W; X = S, Se, Te), 2D sub-stoichiometric WO3-x is gaining importance as a promising semiconductor material for field-effect-transistor (FET) based devices. A combination of high permittivity, suppression of the Coulomb effects, and their stratified structure enhances the carrier mobility in such a material. Additionally, the sub-stoichiometry of this semiconductor oxide allows the reduction of the bandgap and increase of the free charge carriers at the same time. Here, we report for the first time H+ intercalated WO3 FETs, made of Q2D nano-flakes, with enhanced charge-carrier mobility exceeding 319 cm2 V-1 s-1 comparable with the charge-carrier mobility of Q2D dichalcogenides MoS2 and WSe2. Analyses indicate that the enhanced electrical properties of the sub-stoichiometric WO3-x depend on the oxygen vacancies in the intercalated nano-flakes. These findings confirmed that Q2D sub-stoichiometric WO3-x is a promising material for various functional FET devices.Quasi two-dimensional (Q2D) semiconducting metal oxides with enhanced charge carrier mobility hold tremendous promise for nano-electronics, photonics, catalysis, nano-sensors and electrochromic applications. In addition to graphene and metal dichalcogenides MX2 (M = Mo, W; X = S, Se, Te), 2D sub-stoichiometric WO3-x is gaining importance as a promising semiconductor material for field-effect-transistor (FET) based devices. A combination of high permittivity, suppression of the Coulomb effects, and their stratified structure enhances the carrier mobility in such a material. Additionally, the sub-stoichiometry of this semiconductor oxide allows the reduction of the bandgap and increase of the free charge carriers at the same time. Here, we report

  2. Angle-resolved photoemission spectroscopy of the insulating NaxWO3: Anderson localization, polaron formation, and remnant Fermi surface.

    PubMed

    Raj, S; Hashimoto, D; Matsui, H; Souma, S; Sato, T; Takahashi, T; Sarma, D D; Mahadevan, Priya; Oishi, S

    2006-04-14

    The electronic structure of the insulating sodium tungsten bronze, Na(0.025)WO(3), is investigated by high-resolution angle-resolved photoemission spectroscopy. We find that near-E(F) states are localized due to the strong disorder arising from random distribution of Na+ ions in the WO(3) lattice, which makes the system insulating. The temperature dependence of photoemission spectra provides direct evidence for polaron formation. The remnant Fermi surface of the insulator is found to be the replica of the real Fermi surface in the metallic system.

  3. High pressure investigations of Na0.025WO3: x-ray diffraction and Raman spectroscopy studies.

    PubMed

    Basu, Abhisek; Paul, Sanhita; Polentarutti, M; Bais, G; Oishi, S; Raj, Satyabrata; Mukherjee, Goutam Dev

    2011-09-14

    High pressure x-ray diffraction and Raman spectroscopy studies have been carried out on non-stoichiometric sodium tungsten bronze, Na(0.025)WO(3). The high pressure investigations reveal a phase transition at about 2 GPa by a change of space group symmetry from P2(1)/n to P2(1)/c in the monoclinic cell followed by a second structural transformation to a triclinic lattice around 18 GPa. There are volume changes with these structural transformations, which are driven by rotation and significant distortion of WO(6) octahedra due to the displacement of tungsten and oxygen atoms from their mean positions in the unit cell.

  4. Acrylonitrile butadiene rubber (NBR)/manganous tungstate (MnWO4) nanocomposites: Characterization, mechanical and electrical properties

    NASA Astrophysics Data System (ADS)

    Ramesan, M. T.; Abdu Raheem V., P.; Jayakrishnan, P.; Pradyumnan, P. P.

    2014-10-01

    Nanocomposites of NBR with manganous-tungstate nanoparticles were prepared through vulcanization process. The extent of interaction of nanoparticles with the polymer was studied by FTIR, SEM, XRD, TGA and AC conductivity. FTIR and XRD ascertain the interaction of NBR with MnWO4 nanoparticles. SEM analysis established that the nanopartilces were well dispersed in the macromolecular chain of NBR. The mechanical properties of the nanocomposites were studied as a function of filler loading. The nanocomposites exhibited enhanced thermal stability as seen in TGA. Conductivity and dielectric properties of nanocomposites increase with increase in concentration of MnWO4 nanoparticles (7phr) and thereafter the value decreases.

  5. Exciton-exciton interactions in CdWO{sub 4} irradiated by intense femtosecond vacuum ultraviolet pulses

    SciTech Connect

    Kirm, M.; Nagirnyi, V.; Feldbach, E.; De Grazia, M.; Carre, B.; Merdji, H.; Guizard, S.; Geoffroy, G.; Gaudin, J.; Fedorov, N.; Martin, P.; Vasil'ev, A.; Belsky, A.

    2009-06-15

    Exciton-exciton interaction is experimentally revealed and quantitatively analyzed in a wide band-gap scintillator material CdWO{sub 4}. Under high-intensity femtosecond vacuum ultraviolet excitation, the CdWO{sub 4} luminescence is quenched, while its decay becomes essentially nonexponential. We propose an analytical model, which successfully reproduces the decay kinetics recorded in a wide range of excitation densities. The dipole-dipole interaction between excitons leading to their nonradiative decay is shown to be the main cause of a nonproportional response common for many scintillators.

  6. Effect of Na2WO4 on Growth Process and Corrosion Resistance of Micro-arc Oxidation Coatings on 2A12 Aluminum Alloys in CH3COONa Electrolyte

    NASA Astrophysics Data System (ADS)

    Lin, Zhaoqing; Yu, Huijun; He, Siyu; Wang, Diangang; Chen, Chuanzhong

    2016-01-01

    Ceramic coatings were deposited on 2A12 aluminum alloys using micro-arc oxidation (MAO) technology in CH3COONa-Na2WO4 electrolyte. The MAO process was studied by recording the current-time curve. The influences of Na2WO4 concentrations on the coatings in CH3COONa electrolyte were investigated. The results show that the Na2WO4 concentrations affect the MAO process and performances of the coatings directly. Na2WO4 in excess is harmful for the formation of Al2O3 in this electrolyte. The corrosion resistance was enhanced with the decrease of Na2WO4 concentration.

  7. Coaxial electrospinning of WO3 nanotubes functionalized with bio-inspired Pd catalysts and their superior hydrogen sensing performance

    NASA Astrophysics Data System (ADS)

    Choi, Seon-Jin; Chattopadhyay, Saptarshi; Kim, Jae Jin; Kim, Sang-Joon; Tuller, Harry L.; Rutledge, Gregory C.; Kim, Il-Doo

    2016-04-01

    Macroporous WO3 nanotubes (NTs) functionalized with nanoscale catalysts were fabricated using coaxial electrospinning combined with sacrificial templating and protein-encapsulated catalysts. The macroporous thin-walled nanotubular structures were obtained by introducing colloidal polystyrene (PS) particles to a shell solution of W precursor and poly(vinylpyrrolidone). After coaxial electrospinning with a core liquid of mineral oil and subsequent calcination, open pores with an average diameter of 173 nm were formed on the surface of WO3 NTs due to decomposition of the PS colloids. In addition, catalytic Pd nanoparticles (NPs) were synthesized using bio-inspired protein cages, i.e., apoferritin, and uniformly dispersed within the shell solution and subsequently on the WO3 NTs. The resulting Pd functionalized macroporous WO3 NTs were demonstrated to be high performance hydrogen (H2) sensors. In particular, Pd-functionalized macroporous WO3 NTs exhibited a very high H2 response (Rair/Rgas) of 17.6 at 500 ppm with a short response time. Furthermore, the NTs were shown to be highly selective for H2 compared to other gases such as carbon monoxide (CO), ammonia (NH3), and methane (CH4). The results demonstrate a new synthetic method to prepare highly porous nanotubular structures with well-dispersed nanoscale catalysts, which can provide improved microstructures for chemical sensing.Macroporous WO3 nanotubes (NTs) functionalized with nanoscale catalysts were fabricated using coaxial electrospinning combined with sacrificial templating and protein-encapsulated catalysts. The macroporous thin-walled nanotubular structures were obtained by introducing colloidal polystyrene (PS) particles to a shell solution of W precursor and poly(vinylpyrrolidone). After coaxial electrospinning with a core liquid of mineral oil and subsequent calcination, open pores with an average diameter of 173 nm were formed on the surface of WO3 NTs due to decomposition of the PS colloids. In addition

  8. Structural and electronic engineering of 3DOM WO3 by alkali metal doping for improved NO2 sensing performance

    NASA Astrophysics Data System (ADS)

    Wang, Zhihua; Fan, Xiaoxiao; Han, Dongmei; Gu, Fubo

    2016-05-01

    Novel alkali metal doped 3DOM WO3 materials were prepared using a simple colloidal crystal template method. Raman, XRD, SEM, TEM, XPS, PL, Hall and UV-Vis techniques were used to characterize the structural and electronic properties of all the products, while the corresponding sensing performances targeting ppb level NO2 were determined at different working temperatures. For the overall goal of structural and electronic engineering, the co-effect of structural and electronic properties on the improved NO2 sensing performance of alkali metal doped 3DOM WO3 was studied. The test results showed that the gas sensing properties of 3DOM WO3/Li improved the most, with the fast response-recovery time and excellent selectivity. More importantly, the response of 3DOM WO3/Li to 500 ppb NO2 was up to 55 at room temperature (25 °C). The especially high response to ppb level NO2 at room temperature (25 °C) in this work has a very important practical significance. The best sensing performance of 3DOM WO3/Li could be ascribed to the most structure defects and the highest carrier mobility. And the possible gas sensing mechanism based on the model of the depletion layer was proposed to demonstrate that both structural and electronic properties are responsible for the NO2 sensing behavior.Novel alkali metal doped 3DOM WO3 materials were prepared using a simple colloidal crystal template method. Raman, XRD, SEM, TEM, XPS, PL, Hall and UV-Vis techniques were used to characterize the structural and electronic properties of all the products, while the corresponding sensing performances targeting ppb level NO2 were determined at different working temperatures. For the overall goal of structural and electronic engineering, the co-effect of structural and electronic properties on the improved NO2 sensing performance of alkali metal doped 3DOM WO3 was studied. The test results showed that the gas sensing properties of 3DOM WO3/Li improved the most, with the fast response-recovery time and

  9. Rapid preparation and magnetodielectric properties of trirutile Cr{sub 2}WO{sub 6}

    SciTech Connect

    Gaultois, Michael W.; Kemei, Moureen C.; Harada, Jaye K.; Seshadri, Ram

    2015-01-07

    Dense pellets of > 99% purity trirutile Cr{sub 2}WO{sub 6} were prepared in one step from starting oxides using spark plasma sintering, leading to simultaneous reaction and consolidation in 3 min at 1473 K. The reducing environment during processing may be partly responsible for the rapid reaction time in these oxides, with partial reduction of Cr{sup 3+} and the associated oxygen vacancies allowing rapid diffusion of cations. The low-temperature physical properties of Cr{sub 2}WO{sub 6} were examined, and a new transition at T = 5.9 K was observed as an anomaly in the temperature-dependent dielectric permittivity and a corresponding anomaly in the specific heat. A strong enhancement of the magnetocapacitance is observed below this transition temperature at T = 5.9 K and may be associated with a change from collinear spin order to more complex spin order.

  10. Metallic WO2-Carbon Mesoporous Nanowires as Highly Efficient Electrocatalysts for Hydrogen Evolution Reaction.

    PubMed

    Wu, Rui; Zhang, Jingfang; Shi, Yanmei; Liu, Dali; Zhang, Bin

    2015-06-10

    The development of electrocatalysts to generate hydrogen, with good activity and stability, is a great challenge in the fields of chemistry and energy. Here we demonstrate a "hitting three birds with one stone" method to synthesize less toxic metallic WO2-carbon mesoporous nanowires with high concentration of oxygen vacancies (OVs) via calcination of inorganic/organic WO3-ethylenediamine hybrid precursors. The products exhibit excellent performance for H2 generation: the onset overpotential is only 35 mV, the required overpotentials for 10 and 20 mA/cm(2) are 58 and 78 mV, the Tafel slope is 46 mV/decade, the exchange current density is 0.64 mA/cm(2), and the stability is over 10 h. Further studies, in combination with density functional theory, demonstrate that the unusual electronic structure and the large amount of active sites, generated by the high concentration of OVs, as well as the closely attached carbon materials, were key factors for excellent performance. Our results experimentally and theoretically establish metallic transition metal oxides (TMOs) as intriguing novel electrocatalysts for H2 generation. Such TMOs with OVs might be promising candidates for other energy storage and conversion applications.

  11. Hadron calorimeter performance with a PbWO4 EM compartment

    SciTech Connect

    Green, D.

    1996-01-01

    The CMS detector[1] at the LHC has chosen PbWO4 in order to achieve the superior photon energy resolution which is crucial in searching for the 2 photon decay of low mass Higgs bosons. The hadronic compartment is thought to be Cu absorber, since one is immersed in a 4 T magnetic field, read out by scintillator tiles coupled to wavelength shifter (WLS) fibers. The combined performance of this calorimeter is of interest in the study of jets and missing transverse energy (neutrino, SUSY signatures). For this reason, a test was made of the electromagnetic (EM) compartment combined with a reasonable approximation to the baseline HCAL ``barrel`` calorimeter. Data was taken in the H4 CERN beamline. The EM compartment was a 7 {times} 7 square array of PbWO4 crystals, which for the purposes of this study are considered as a single readout in depth (or ``compartment``) [2]. The HCAL module consisted of large scintillator plates with 24 individual longitudinal readout channels. The EM compartment was followed by 10 Cu plates each 3 cm thick, followed by 9 Cu plates each 6 cm thick. This set of absorber plates represented the HCAL compartments inside the coil. The coil itself [1] was approximated as Al and Fe plates, of a total thickness of about 1.4 absorption lengths. The coil mockup was sampled and then followed by 4 plates of 8 cm thick Cu, each with an individual readout which represented a test of the ``Tailcatcher`` concept.

  12. Sulfur K-edge XANES for methylene blue in photocatalytic reaction over WO3 nanomaterials

    NASA Astrophysics Data System (ADS)

    Komori, K.; Yoshida, T.; Nomoto, T.; Yamamoto, M.; Tsukada, C.; Yagi, S.; Yajima, M.; Kajita, S.; Ohno, N.

    2015-12-01

    We investigated the photocatalysis of dendritic nanostructured WO3/W composite materials fabricated by He plasma irradiation to tungsten plates, followed by the surface oxidation. The samples promoted the decolorization reaction of methylene blue (MB) aqueous solution under near infrared (NIR) light irradiation. To verify the MB molecule is actually decomposed by the photocatalysis of the samples, reaction products were analyzed by S K-edge XANES measurements for the MB solution kept with the samples under the light irradiation or in the dark. By the light irradiation, the σ*(S-C) peak in the XANES spectra reduced and a new peak originated from SO42- species was clearly observed, suggesting that S-C bonds in a MB molecule are broken by the NIR light irradiation and finally the sulfur species exists in the solution in the state of SO42- ion. After the adsorption reaction in the dark, the XANES spectra of the sample surfaces showed a sharp π*(S-C) peaks, indicating that MB molecules are adsorbed on the sample surfaces and stacked each other by the π-π interaction. These results demonstrate that the photocatalytic decomposition of MB molecules really proceeds over WO3/W composite materials even under NIR light irradiation.

  13. Integrated readout electronics for the PbWO{sub 4} photon spectrometer

    SciTech Connect

    Simpson, M.L.; Alley, G.T.; Awes, T.

    1995-12-31

    The PbWO{sub 4} calorimeter of the ALICE detector is designed to detect the prompt photons to provide direct information on the partonic, early phases of the heavy-ion interaction. The goal is to measure all the photons over a large enough solid angle to reconstruct both {pi}{sup 0}`s and {eta}`s. A proposed readout system for the ALICE PbWO{sub 4} photon spectrometer is presented. In one proposed implementation, light will be detected from each end of the crystals by PIN photodiodes and this signal will be amplified by charge-sensitive amplifiers. The 73,728 channel readout system will accept the preamplifier signals and deliver digitized data to the data collection modules. A readout board will consist of 8-channel, custom front-end chips which form energy and timing signals, and board-level control and communication circuits. Many of the subcircuits proposed for this spectrometer have been developed for use in other applications. The performance of these circuits is shown.

  14. PH Tester Gauge Repeatability and Reproducibility Study for WO3 Nanostructure Hydrothermal Growth Process

    NASA Astrophysics Data System (ADS)

    Abd Rashid, Amirul; Hayati Saad, Nor; Bien Chia Sheng, Daniel; Yee, Lee Wai

    2014-06-01

    PH value is one of the important variables for tungsten trioxide (WO3) nanostructure hydrothermal synthesis process. The morphology of the synthesized nanostructure can be properly controlled by measuring and controlling the pH value of the solution used in this facile synthesis route. Therefore, it is very crucial to ensure the gauge used for pH measurement is reliable in order to achieve the expected result. In this study, gauge repeatability and reproducibility (GR&R) method was used to assess the repeatability and reproducibility of the pH tester. Based on ANOVA method, the design of experimental metrics as well as the result of the experiment was analyzed using Minitab software. It was found that the initial GR&R value for the tester was at 17.55 % which considered as acceptable. To further improve the GR&R level, a new pH measuring procedure was introduced. With the new procedure, the GR&R value was able to be reduced to 2.05%, which means the tester is statistically very ideal to measure the pH of the solution prepared for WO3 hydrothermal synthesis process.

  15. Pressure-Induced Structural and Electronic Transition in Sr2ZnWO6 Double Perovskite.

    PubMed

    Li, Nana; Manoun, Bouchaib; Tang, Lingyun; Ke, Feng; Liu, Fengliang; Dong, Haini; Lazor, Peter; Yang, Wenge

    2016-07-05

    High-pressure structural and electrical properties of Sr2ZnWO6 double perovskite were investigated using in situ angle-dispersive synchrotron X-ray diffraction (XRD), Raman, and alternating current (AC) impedance spectroscopy. A structural transition from monoclinic (P21/n) to triclinic (P1̅) phase around 9 GPa was observed due to the pressure-induced distortion of (W, Zn)O6 octahedron. In situ high-pressure Raman spectroscopy showed the increasing interaction among O-W-O in WO6 octahedron with pressure and a transition pressure consistent with the XRD results. From the AC impedance spectroscopy measurements, the resistivity increased steeply by ∼1 order of magnitude around 11 GPa, indicating an electronic transition accompanying the symmetry change. The increase in the interaction among O-W-O enhances the attraction of O(2-) electrons toward W(6+), thus increasing the covalence, which in turn lowers the charge transfer energy between O(2-) and W(6+) and induces the resistivity increase under high pressure.

  16. An efficient frequency-doubled Nd:KLu(WO4)2 laser at 535 nm

    NASA Astrophysics Data System (ADS)

    Fu, Qiang; Zhang, Xingyu; Liu, Zhaojun; Cong, Zhenhua; Zhang, Huaijin; Li, Jing; Yu, Haohai; Wang, Weitao

    2016-03-01

    An efficient laser diode pumped frequency-doubled Nd:KLu(WO4)2 laser at 535 nm was demonstrated for the first time. For continuous wave (CW) operation, the obtained maximum output power was 2.4 W and the overall optical-to-optical conversion efficiency with respect to the absorbed pump power was 20.5%. For active Q-switching operation, the obtained maximum average output power was 2.6 W and the conversion efficiency with regard to the absorbed pump power was 26.8%. The corresponding pulse repetition rate (PRR), pulse width, single pulse energy and peak power were 30 kHz, 36.6 ns, 86.7 μJ, and 2.4 kW, respectively. On the basis of rate equations, the characteristics of the actively Q-switched frequency-doubled Nd:KLu(WO4)2 laser were simulated. The theoretical results of the average output power and pulse width were obtained. They were in agreement with the measured data on the whole.

  17. Microsphere morphology tuning and photo-luminescence properties of monoclinic Y2WO6

    NASA Astrophysics Data System (ADS)

    Gao, Hong; Bai, Yulong; Zhang, Junying; Tang, Zilong

    2015-04-01

    Effects of the solution pH value and reaction time on the precursor morphology and photoluminescence properties are investigated for hydrothermally prepared monoclinic Y2WO6 phosphors. In the near-neutral environment, sodium dodecyl benzene sulfonate (SDBS) surfactant forms small microspheres micelles as template to synthesize microspherical precursor. H+ ions concentration affects the arrangement of negative ionic surfactant SDBS. As a result, jujube-liked and popcorn-like loose microspheres formed at low pH value. When the pH value is 5.2 and the hydrothermal reaction time reaches 24 h, respectively, the strongest luminescent intensity can be obtained. Under this condition, the precursor presented regular microsphere with diameter of 4.0 μm. After high-temperature heat treatment, the obtained phosphor particles still exhibit microsphere-like shape. Therefore, we provide an effective method to tune the morphology of Y2WO6 phosphors and study the relationship between morphology and luminescent performance.

  18. WO3/W Nanopores Sensor for Chemical Oxygen Demand (COD) Determination under Visible Light

    PubMed Central

    Li, Xuejin; Bai, Jing; Liu, Qiang; Li, Jianyong; Zhou, Baoxue

    2014-01-01

    A sensor of a WO3 nanopores electrode combined with a thin layer reactor was proposed to develop a Chemical Oxygen Demand (COD) determination method and solve the problem that the COD values are inaccurately determined by the standard method. The visible spectrum, e.g., 420 nm, could be used as light source in the sensor we developed, which represents a breakthrough by limiting of UV light source in the photoelectrocatalysis process. The operation conditions were optimized in this work, and the results showed that taking NaNO3 solution at the concentration of 2.5 mol·L−1 as electrolyte under the light intensity of 214 μW·cm−2 and applied bias of 2.5 V, the proposed method is accurate and well reproducible, even in a wide range of pH values. Furthermore, the COD values obtained by the WO3 sensor were fitted well with the theoretical COD value in the range of 3–60 mg·L−1 with a limit value of 1 mg·L−1, which reveals that the proposed sensor may be a practical device for monitoring and controlling surface water quality as well as slightly polluted water. PMID:24940868

  19. Band tail absorption saturation in CdWO4 with 100 fs laser pulses.

    PubMed

    Laasner, R; Fedorov, N; Grigonis, R; Guizard, S; Kirm, M; Makhov, V; Markov, S; Nagirnyi, V; Sirutkaitis, V; Vasil'ev, A; Vielhauer, S; Tupitsyna, I A

    2013-06-19

    The decay kinetics of the excitonic emission of CdWO4 scintillators was studied under excitation by powerful 100 fs laser pulses in the band tail (Urbach) absorption region. A special imaging technique possessing both spatial and temporal resolution provided a unique insight into the Förster dipole-dipole interaction of self-trapped excitons, which is the main cause of the nonlinear quenching of luminescence in this material. In addition, the saturation of phonon-assisted excitonic absorption due to extremely short excitation pulses was discovered. A model describing the evolution of electronic excitations in the conditions of absorption saturation was developed and an earlier model of decay kinetics based on the Förster interaction was extended to include the saturation effect. Compared to the previous studies, a more accurate calculation yields 3.7 nm as the Förster interaction radius. It was shown that exciton-exciton interaction is the main source of scintillation nonproportionality in CdWO4. A quantitative description using a new model of nonproportionality was presented, making use of the corrected value of the Förster radius.

  20. Electrochemical study of aqueous asymmetric FeWO4/MnO2 supercapacitor

    NASA Astrophysics Data System (ADS)

    Goubard-Bretesché, Nicolas; Crosnier, Olivier; Buvat, Gaëtan; Favier, Frédéric; Brousse, Thierry

    2016-09-01

    The concept of an asymmetric FeWO4/MnO2 electrochemical capacitor cycled in a neutral aqueous electrolyte is presented for the first time. Commercially available cryptomelane-type MnO2 and synthesized nanocrystalline FeWO4 were used as positive and negative electrode materials, respectively. Prior to assembling the cell, the electrodes have been individually tested in a 5 M LiNO3 electrolyte solution to define both the adequate balance of active material in the supercapacitor and the proper working voltage window. Then, the full asymmetric device has been cycled between 0 and 1.4 V for over 40,000 cycles and subjected to accelerated ageing tests under floating conditions at different voltages, without any significant change on its electrochemical behavior. This remarkable stability shows the interest of developing full oxide-based asymmetric supercapacitors operating in non-toxic aqueous electrolytes that could compete with commercial carbon-based electrochemical double-layer capacitors.

  1. Analysis of SnO2|WO3 Heterocontact Properties during the Detection of Hydrogen Sulphide

    PubMed Central

    Suchorska-Woźniak, Patrycja; Rac, Olga; Fiedot, Marta; Teterycz, Helena

    2014-01-01

    The main objective of the paper was the analysis of the properties of SnO2|WO3 heterocontact as well as the determination of its response to 50 ppm of hydrogen sulphide. It was noticed that the sensitivity of the sensor being tested to hydrogen sulphide depended significantly on the polarization direction. When its parameters were compared with those of sensors the gas-sensitive layer of which was made only from one type of metal oxide, a high impact of the heterocontact on the electric charge transport was noticed. The value of the activation energy of the electric conductivity is clearly dependent on the polarization direction. A mechanism of physicochemical processes occurring in a planar sensor with a heterocontact was suggested, and three areas differing in the width of depleted layer, where the inter-phase boundary of SnO2|WO3 had the most essential impact on the parameters of the sensor being tested, were distinguished and described. PMID:25360578

  2. Monolayered Bi2WO6 nanosheets mimicking heterojunction interface with open surfaces for photocatalysis

    NASA Astrophysics Data System (ADS)

    Zhou, Yangen; Zhang, Yongfan; Lin, Mousheng; Long, Jinlin; Zhang, Zizhong; Lin, Huaxiang; Wu, Jeffrey C.-S.; Wang, Xuxu

    2015-09-01

    Two-dimensional-layered heterojunctions have attracted extensive interest recently due to their exciting behaviours in electronic/optoelectronic devices as well as solar energy conversion systems. However, layered heterojunction materials, especially those made by stacking different monolayers together by strong chemical bonds rather than by weak van der Waal interactions, are still challenging to fabricate. Here the monolayer Bi2WO6 with a sandwich substructure of [BiO]+-[WO4]2--[BiO]+ is reported. This material may be characterized as a layered heterojunction with different monolayer oxides held together by chemical bonds. Coordinatively unsaturated Bi atoms are present as active sites on the surface. On irradiation, holes are generated directly on the active surface layer and electrons in the middle layer, which leads to the outstanding performances of the monolayer material in solar energy conversion. Our work provides a general bottom-up route for designing and preparing novel monolayer materials with ultrafast charge separation and active surface.

  3. Polarized-neutron-scattering studies on the chiral magnetism in multiferroic MnWO4

    NASA Astrophysics Data System (ADS)

    Finger, T.; Senff, D.; Schmalzl, K.; Schmidt, W.; Regnault, L. P.; Becker, P.; Bohatý, L.; Braden, M.

    2010-02-01

    Neutron diffraction with spherical polarization analysis is a powerful tool for studying the multiferroic materials where the ferroelectric polarization arises from a complex magnetic structure. Analyzing the off-diagonal terms in the polarization matrix one may directly detect the chiral contributions even in a multidomain arrangement. In MnWO4 one can control the chiral magnetism by varying an electric field at constant temperature. The analysis of multiferroic hysteresis cycles at four equivalent magnetic Bragg peaks fully agrees with a nearly monodomain chiral arrangement controlled by the electric field. A pronounced asymmetry of the hysteresis cycles and memory effects point to strong pinning of the chiral magnetism in MnWO4. We find a second-order harmonic modulation which exhibits both magnetic and structural character and which may be related with the domain pinning. The observed interference between the nuclear and the magnetic modulation is another manifestation of the coupling between the crystal structure and the magnetism in the multiferroic oxides.

  4. Monolayered Bi2WO6 nanosheets mimicking heterojunction interface with open surfaces for photocatalysis

    PubMed Central

    Zhou, Yangen; Zhang, Yongfan; Lin, Mousheng; Long, Jinlin; Zhang, Zizhong; Lin, Huaxiang; Wu, Jeffrey C.-S.; Wang, Xuxu

    2015-01-01

    Two-dimensional-layered heterojunctions have attracted extensive interest recently due to their exciting behaviours in electronic/optoelectronic devices as well as solar energy conversion systems. However, layered heterojunction materials, especially those made by stacking different monolayers together by strong chemical bonds rather than by weak van der Waal interactions, are still challenging to fabricate. Here the monolayer Bi2WO6 with a sandwich substructure of [BiO]+–[WO4]2−–[BiO]+ is reported. This material may be characterized as a layered heterojunction with different monolayer oxides held together by chemical bonds. Coordinatively unsaturated Bi atoms are present as active sites on the surface. On irradiation, holes are generated directly on the active surface layer and electrons in the middle layer, which leads to the outstanding performances of the monolayer material in solar energy conversion. Our work provides a general bottom-up route for designing and preparing novel monolayer materials with ultrafast charge separation and active surface. PMID:26359212

  5. Phase, thermal and impedance studies of nanosize LiWO via mechanical milling and sintering

    NASA Astrophysics Data System (ADS)

    Han, Tan Kim; Ahmad, Roslina; Johan, Mohd Rafie

    2011-01-01

    Nanosize Li 2WO 4 is successfully synthesized using a mechanical milling method. The mean particle size of milled Li 2WO 4 is 37 nm and 31 nm as measured by Transmission Electron Microscopy (TEM) and X-ray diffraction (XRD) analysis, respectively. The calculated lattice parameter of as-received and milled powder are 0.8326 and 0.8321 nm, respectively. Both powders have been hydrated at room temperature and are highly crystalline with the presence of different types of phases at varying sintering temperatures. There is no Li 2W 2O 7 (JCPDS 28-0598) phase present in the milled powder during the whole sintering process. Meanwhile, the thermogravimetric analysis (TGA) of both powders is in accordance with their phase changes as presented in the XRD spectra. The impedance measurements show that the milled powder has a lower conductivity than that of the as-received powder in overall. The conductivity of the as-received powder increases with sintering temperature but this phenomenon is vice versa for the milled powder. All these trends can be correlated with the Field Emission Scanning Electron Microscopy (FE-SEM) micrographs on both powders.

  6. ZnWO4 anisotropic scintillator for Dark Matter investigation with the directionality technique

    NASA Astrophysics Data System (ADS)

    Bernabei, R.; Belli, P.; Cappella, F.; Caracciolo, V.; Cerulli, R.; Danevich, F. A.; d'Angelo, A.; Di Marco, A.; Incicchitti, A.; Mokina, V. M.; Poda, D. V.; Polischuk, O. G.; Taruggi, C.; Tretyak, V. I.

    2017-03-01

    The ZnWO4 crystal scintillator has unique features that make it very promising to realize a pioneering experiment to pursue Dark Matter investigation with the directionality technique. In particular in this detector the light output and the scintillation pulse shape for heavy particles (p, α, nuclear recoils) depend on the direction of the impinging particle with respect to the crystal axes, while the response to γ/β radiation is isotropic. The anisotropy of the light output can be considered to point out the presence in the diurnal counting rate of a Dark Matter signal produced by candidate particle inducing just nuclear recoils. In addition this crystal detector has also other important characteristics for a Dark Matter experiment: high light output, high level of radiopurity. In this paper the present performances of the developed ZnWO4 crystal scintillator will be summarized together with the possible future improvements. Some reachable sensitivities - under given assumptions - in the investigation of DM candidate particles with the directionality technique will also be addressed.

  7. Construction and Nanoscale Detection of Interfacial Charge Transfer of Elegant Z-Scheme WO3/Au/In2S3 Nanowire Arrays.

    PubMed

    Li, Haijin; Gao, Yuying; Zhou, Yong; Fan, Fengtao; Han, Qiutong; Xu, Qinfeng; Wang, Xiaoyong; Xiao, Min; Li, Can; Zou, Zhigang

    2016-09-14

    Elegant Z-scheme WO3/Au/In2S3 nanowire arrays were precisely constructed through a facile step-by-step route. Surface potential change on pristine or In2S3-Au coated WO3 single nanowire under dark and illumination detected through a Kelvin probe force microscopy (KPFM) technique indicates that the vectorial holes transfer of In2S3 → Au → WO3 should occur upon the excitation of both WO3 and In2S3. In such charge transfer processes, the embedded Au nanoparticles in the heterojunction systems act as a charge mediator for electrons in the conduction band of WO3 and holes in the valence band of In2S3. The strong charge carrier separation ability of this structure will finally enhance the oxidation ability of WO3 with high concertation of photogenerated holes and, further, leave the free electrons in the In2S3 with long surviving time. Therefore, the unique Z-scheme WO3/Au/In2S3 heterostructure shows great visible-light activity toward photocatalytic reduction of CO2 in the presence of water vapor into renewable hydrocarbon fuel (methane: CH4).

  8. Construction and Nanoscale Detection of Interfacial Charge Transfer of Elegant Z-Scheme WO3/Au/In2S3 Nanowire Arrays.

    PubMed

    Li, Haijin; Gao, Yuying; Zhou, Yong; Fan, Fengtao; Han, Qiutong; Xu, Qinfeng; Wang, Xiaoyong; Xiao, Min; Li, Can; Zou, Zhigang

    2016-08-03

    Elegant Z-scheme WO3/Au/In2S3 nanowire arrays were precisely constructed through a facile step-by-step route. Surface potential change on pristine or In2S3-Au coated WO3 single nanowire under dark and illumination detected through a Kelvin probe force microscopy (KPFM) technique indicates that the vectorial holes transfer of In2S3 → Au → WO3 should occur upon the excitation of both WO3 and In2S3. In such charge transfer processes, the embedded Au nanoparticles in the heterojunction systems act as a charge mediator for electrons in the conduction band of WO3 and holes in the valence band of In2S3. The strong charge carrier separation ability of this structure will finally enhance the oxidation ability of WO3 with high concertation of photogenerated holes and, further, leave the free electrons in the In2S3 with long surviving time. Therefore, the unique Z-scheme WO3/Au/In2S3 heterostructure shows great visible-light activity toward photocatalytic reduction of CO2 in the presence of water vapor into renewable hydrocarbon fuel (methane: CH4).

  9. Effects of micro-sized and nano-sized WO3 on mass attenauation coefficients of concrete by using MCNPX code.

    PubMed

    Tekin, H O; Singh, V P; Manici, T

    2017-03-01

    In the present work the effect of tungsten oxide (WO3) nanoparticles on mass attenauation coefficients of concrete has been investigated by using MCNPX (version 2.4.0). The validation of generated MCNPX simulation geometry has been provided by comparing the results with standard XCOM data for mass attenuation coefficients of concrete. A very good agreement between XCOM and MCNPX have been obtained. The validated geometry has been used for definition of nano-WO3 and micro-WO3 into concrete sample. The mass attenuation coefficients of pure concrete and WO3 added concrete with micro-sized and nano-sized have been compared. It was observed that shielding properties of concrete doped with WO3 increased. The results of mass attenauation coefficients also showed that the concrete doped with nano-WO3 significanlty improve shielding properties than micro-WO3. It can be concluded that addition of nano-sized particles can be considered as another mechanism to reduce radiation dose.

  10. Construction of solid-state Z-scheme carbon-modified TiO2/WO3 nanofibers with enhanced photocatalytic hydrogen production

    NASA Astrophysics Data System (ADS)

    Hu, Junhua; Wang, Lijie; Zhang, Peng; Liang, Changhao; Shao, Guosheng

    2016-10-01

    Carbon-layer-coated TiO2/WO3 nanofibers (WTC) were fabricated by combining the electrospinning technique (for TiO2/WO3 nanofibers) and hydrothermal method (for carbon shell). The structure characterization results showed that TiO2/WO3 nanofibers (WT) were encased within an uniform carbon shell about 10 nm in thickness. By adjusting the content of WO3, the graphitization degree of carbon layer could be controlled, and the WTC nanofibers had remarkable light absorption in the visible region. Furthermore, the photoelectrochemical performance and photocatalytic activity were investigated systematically. As expected, the H2-generation rate of the as-prepared composite materials was greatly enhanced compared with pure TiO2 nanofibers (TNFs), TiO2/WO3 nanofibers (WT) and TiO2@carbon core/shell nanofibers (TC). The enhanced activities were mainly attributed to the multichannel-improved charge-carrier photosynthetic heterojunction system with the carbon layer on the surface of TiO2 as an electron collector and WO3 as a hole collector, leading to effective charge separation on these components, which were evidenced by photoluminescence spectroscopy (PL), electrochemical impedance spectroscopy (EIS) and photocurrent analysis. Besides, the addition of WO3 promoted the graphitization of carbon layer, which in turn improved transport of electrons in the carbon layer and also contributed to the performance improvement.

  11. Facile preparation of Z-scheme WO3/g-C3N4 composite photocatalyst with enhanced photocatalytic performance under visible light

    NASA Astrophysics Data System (ADS)

    Cui, Lifeng; Ding, Xiang; Wang, Yangang; Shi, Huancong; Huang, Lihua; Zuo, Yuanhui; Kang, Shifei

    2017-01-01

    Visible-light-driven WO3/g-C3N4 composites photocatalysts were synthesized via a facile one-step simultaneously heating procedure with urea as the main precursor. These prepared catalyst samples were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TG), transmission electron microscopy (TEM), N2 adsorption, ultraviolet-visible diffuse reflection spectroscopy (UV-vis), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and electrochemical impedance spectroscopy (EIS). The photocatalytic activity of the WO3/g-C3N4 composites was evaluated by the photo-degradation of Rhodamine B (RhB) under visible light irradiation. The results indicated that the composites with 25 wt.% WO3 content exhibited highest photocatalytic activity compared to pure WO3, bare g-C3N4 and other WO3/g-C3N4 composites. The favorable photocatalytic activity of WO3/g-C3N4 composites was mainly attributed to the excellent surface properties, enhanced visible-light absorption and the desirable band positions. A possible Z-scheme photocatalytic mechanism was proposed based on structure and electrochemical characterizations results, which can well explain the enhanced migration rate of photogenerated electrons and holes in WO3/g-C3N4 heterojunctions.

  12. A P25/(NH4)xWO3 hybrid photocatalyst with broad spectrum photocatalytic properties under UV, visible, and near-infrared irradiation

    PubMed Central

    Yang, Linfen; Liu, Bin; Liu, Tongyao; Ma, Xinlong; Li, Hao; Yin, Shu; Sato, Tsugio; Wang, Yuhua

    2017-01-01

    In this study, a series of hybrid nanostructured photocatalysts P25/(NH4)xWO3 nanocomposites with the average crystallite size of P25 and (NH4)xWO3 of the sample was calculated to be about 30 nm and 130 nm, were successfully synthesized via a simple one-step hydrothermal method. The as-obtained samples was characterized by transmission electron microscopy (TEM), which implies that the P25/(NH4)xWO3 nanocomposites are fabricated with favourable nanosizd interfacial. The XPS results confirmed that the obtained sample consists of mixed chemical valences of W5+ and W6+, the low-valance W5+ sites could be the origin of NIR absorption. As revealed by optical absorption results, P25/(NH4)xWO3 nanocomposites possess high optical absorption in the whole solar spectrum of 200–2500 nm. Benefiting from this unique photo-absorption property and the synergistic effect of P25 and (NH4)xWO3, broad spectrum response photocatalytic activities covering UV, visible and near infrared regions on degradation of Rhodamine B have been realized by P25/(NH4)xWO3 nanocomposites. Meanwhile, the stability of photocatalysts was examined by the XRD and XPS of the photocatalysts after the reaction. The results show that P25/(NH4)xWO3 photocatalysts has a brilliant application prospect in the energy utilization to solve deteriorating environmental issues. PMID:28368032

  13. Facile formation of Ag{sub 2}WO{sub 4}/AgX (X = Cl, Br, I) hybrid nanorods with enhanced visible-light-driven photoelectrochemical properties

    SciTech Connect

    Li, Jingjing; Yu, Caiyun; Zheng, Changcheng; Etogo, Atangana; Xie, Yunlong; Zhong, Yijun; Hu, Yong

    2015-01-15

    Highlights: • Ag{sub 2}WO{sub 4}/AgX hybrid nanorods were prepared by a facile in-situ anion exchange reaction. • Ag{sub 2}WO{sub 4} nanorods and different X{sup −} ions were reacted in water at room temperature. • The hybrids possess significantly enhanced photoelectrochemical properties. • Ag{sub 2}WO{sub 4}/AgBr hybrids exhibit the highest photocatalytic activity among three samples. • The active species tests were also investigated to confirm photocatalytic mechanism. - Abstract: In this work, we demonstrated a general strategy for the preparation of a series of uniform Ag{sub 2}WO{sub 4}/AgX (X = Cl, Br, I) hybrid nanorods by a facile in-situ anion exchange reaction occurring at room temperature between pregrown Ag{sub 2}WO{sub 4} nanorods and different X{sup −} ions in water. Compared with Ag{sub 2}WO{sub 4} nanorods, further investigation has revealed that the as-prepared hybrid nanorods possess significantly enhanced photocurrent response and photocatalytic activity in degrading methyl orange (MO) under visible-light irradiation. In particular, the Ag{sub 2}WO{sub 4}/AgBr hybrid nanorods exhibit the highest photocatalytic activity among the three kinds of samples. The active species tests indicate that superoxide anion radicals and photogenerated holes are responsible for the enhanced photocatalytic performance.

  14. Dual-functional surfactant-templated strategy for synthesis of an in-situ N2-intercalated mesoporous WO3 photoanode for efficient visible-light-driven water oxidation.

    PubMed

    Li, Dong; Chandra, Debraj; Takeuchi, Ryouchi; Togashi, Takanari; Kurihara, Masato; Saito, Kenji; Yui, Tatsuto; Yagi, Masayuki

    2017-03-01

    N2-intercalated crystalline mesoporous tungsten trioxide (WO3) was synthesized by a thermal decomposition technique using dodecylamine (DDA) as a surfactant template with a dual functional role of an N atom source for N2 intercalation, alongside its conventional structure directing role (by micelle formation) to induce a mesoporous structure. N2 physisorption analysis showed that the specific surface area (57.3 m2 g-1) of WO3 (WO3-DDA) templated with DDA is 2.3 times higher than that (24.5 m2 g-1) of WO3 (WO3-bulk) prepared without DDA due to the mesoporous structure of WO3-DDA. The Raman spectra and XPS spectrum of WO3-DDA indicated formation of N2 intercalated into the WO3 lattice above 450 ºC. The UV-visible diffuse reflectance spectra (DRS) exhibited the significant shift of the absorption edge from 459 nm (2.70 eV) to 487 nm (2.54 eV) by 28 nm due to N2-intercalation. This could be explained by the bandgap narrowing of WO3-DDA by formation of a new intermediate N 2p orbital between the conduction band and valance band of WO3. A WO3-DDA coated ITO electrode calcined at 450 ºC generated a photoanodic current under visible light irradiation below 490 nm due to the PEC water oxidation, compared with ITO/WO3-bulk doing so below 470 nm. The incident photon-to-current conversion efficiency (IPCE = 24.5%) at 420 nm and 0.5 V vs Ag/AgCl was higher than that (2.5%) for ITO/WO3-bulk by one order of magnitude due to the N2 intercalation and the mesoporous structure of WO3-DDA.

  15. Incorporation of Jahn-Teller Cu(2+) Ions into Magnetoelectric Multiferroic MnWO4: Structural, Magnetic, and Dielectric Permittivity Properties of Mn1-xCuxWO4 (x ≤ 0.25).

    PubMed

    Patureau, Pascaline; Josse, Michaël; Dessapt, Rémi; Mevellec, Jean-Yves; Porcher, Florence; Maglione, Mario; Deniard, Philippe; Payen, Christophe

    2015-11-16

    Polycrystalline samples of Mn1-xCuxWO4 (x ≤ 0.5) have been prepared by a solid-state synthesis as well as from a citrate synthesis at moderate temperature (850 °C). The goal is to study changes in the structural, magnetic, and dielectric properties of magnetoelectric type-II multiferroic MnWO4 caused by replacing Jahn-Teller-inactive Mn(2+) (d(5), S = 5/2) ions with Jahn-Teller-active Cu(2+) (d(9), S = 1/2) ions. Combination of techniques including scanning electron microscopy, powder X-ray and neutron diffraction, and Raman spectroscopy demonstrates that the polycrystalline samples with low copper content 0 ≤ x ≤ 0.25 are solid solution that forms in the monoclinic P2/c space group. Rietveld analyses indicate that Cu atoms substitutes for Mn atoms at the Mn crystallographic site of the MnWO4 structure and suggest random distributions of Jahn-Teller-distorted CuO6 octahedra in the solid solution. Magnetic susceptibility reveals that only 5% of Cu substitution suppresses the nonpolar collinear AF1 antiferromagnetic structure observed in pure MnWO4. Type-II multiferroicity survives a weak Cu substitution rate (x < 0.15). Multiferroic transition temperature and Néel temperature increase as the amount of Cu increases. New trends in some of the magnetic properties and in dielectric behaviors are observed for x = 0.20 and 0.25. Careful analysis of the magnetic susceptibility reveals that the incorporation of Cu into MnWO4 strengthens the overall antiferromagnetic interaction and reduces the magnetic frustration.

  16. Study of an Energy Storage and Recovery Concept Based on the W/WO3 Redox Reaction: Part I. Kinetic Study and Modeling of the WO3 Reduction Process for Energy Storage

    NASA Astrophysics Data System (ADS)

    Haboury, Romain; Pal, Uday B.; Zink, Peter A.; Gopalan, Srikanth; Basu, Soumendra N.

    2012-08-01

    Energy storage and recovery using the redox reaction of tungsten/tungsten-oxide is proposed. The system will store energy as tungsten metal by reducing the tungsten oxide with hydrogen. Thereafter, steam will be used to reoxidize the metal and recover the hydrogen. The volumetric energy density of W for storing hydrogen by this process is 21 kWh/L based on the lower heating value (LHV) of hydrogen. The main objective of this investigation was to study the kinetics of the reduction process of tungsten oxide (WO3) and determine the optimum parameters for rapid and complete reduction. Theoretical treatment of isothermal kinetics has been extended in the current work to the reduction of tungsten oxide in powder beds. Experiments were carried out using a thermogravimetric technique under isothermal conditions at different temperatures. The reaction at 1073 K (800 °C) was found to take place in the following sequence: WO3 → WO2.9 → WO2.72 → WO2 → W. Expressions for the last three reaction rate constants and activation energies have been calculated based on the fact that the intermediate reactions proceed as a front moving at a certain velocity while the first reaction occurs in the entire bulk of the oxide. The gas-solid reaction kinetics were modeled mathematically in terms of the process parameters. This model of the reduction has been found to be accurate for bed heights above 1.5 mm and hydrogen partial pressures greater than 3 pct, which is ideal for implementing the energy storage concept.

  17. Composite WO3/TiO2 nanostructures for high electrochromic activity

    SciTech Connect

    Reyes-Gil, Karla R.; Stephens, Zachary D.; Stavila, Vitalie; Robinson, David B.

    2015-01-06

    A composite material consisting of TiO2 nanotubes (NT) with WO3 electrodeposited on its surface has been fabricated, detached from its Ti substrate, and attached to a fluorine-doped tin oxide (FTO) film on glass for application to electrochromic (EC) reactions. Several adhesion layers were tested, finding that a paste of TiO2 made from commercially available TiO2 nanoparticles creates an interface for the TiO2 NT film to attach to the FTO glass, which is conductive and does not cause solution-phase ions in an electrolyte to bind irreversibly with the material. The effect of NT length and WO3 concentration on the EC performance were studied. As a result, the composite WO3/TiO2 nanostructures showed higher ion storage capacity, better stability, enhanced EC contrast, and longer memory time compared with the pure WO3 and TiO2 materials

  18. In situ growth of Ag nanoparticles on α-Ag2WO4 under electron irradiation: probing the physical principles

    NASA Astrophysics Data System (ADS)

    San-Miguel, Miguel A.; da Silva, Edison Z.; Zannetti, Sonia M.; Cilense, Mario; Fabbro, Maria T.; Gracia, Lourdes; Andrés, Juan; Longo, Elson

    2016-06-01

    Exploiting the plasmonic behavior of Ag nanoparticles grown on α-Ag2WO4 is a widely employed strategy to produce efficient photocatalysts, ozone sensors, and bactericides. However, a description of the atomic and electronic structure of the semiconductor sites irradiated by electrons is still not available. Such a description is of great importance to understand the mechanisms underlying these physical processes and to improve the design of silver nanoparticles to enhance their activities. Motivated by this, we studied the growth of silver nanoparticles to investigate this novel class of phenomena using both transmission electron microscopy and field emission scanning electron microscopy. A theoretical framework based on density functional theory calculations (DFT), together with experimental analysis and measurements, were developed to examine the changes in the local geometrical and electronic structure of the materials. The physical principles for the formation of Ag nanoparticles on α-Ag2WO4 by electron beam irradiation are described. Quantum mechanical calculations based on DFT show that the (001) of α-Ag2WO4 displays Ag atoms with different coordination numbers. Some of them are able to diffuse out of the surface with a very low energy barrier (less than 0.1 eV), thus, initiating the growth of metallic Ag nanostructures and leaving Ag vacancies in the bulk material. These processes increase the structural disorder of α-Ag2WO4 as well as its electrical resistance as observed in the experimental measurements.

  19. Simultaneous Reduction of Vanadium (V) and Chromium (VI) in Wastewater by Nanosized ZnWO4 Photocatalysis.

    PubMed

    Zhao, Zengying; Zhang, Baogang; Chen, Daimei; Guo, Zhanhu; Peng, Zhijian

    2016-03-01

    Vanadium (V, V) and chromium (Cr, VI) are simultaneously photocatalytically reduced to less-toxic V(VI) and Cr(III) by mimetic solar light with ZnWO4 nanoparticles prepared by hydrothermal synthesis. The reduction efficiencies can reach 68.8% for V(V) and 97.3% for Cr(VI) in 3 h, respectively, which are comparable to those by microbial fuel cell technology carried out in over 10 days. The prepared ZnWO4 nanoparticles are characterized by XRD, SEM, EDS, TEM, and Uv-vis-DRS tests. Electrochemical calculation shows high acidity benefits the rapid reduction of V(V) and Cr(VI). In addition, the applied ZnWO4 nanoparticles can be recycled and reused for 5 repeated photocatalytic reduction runs. And after 5 runs, the recycled ZnWO4 nanoparticles can also present good photocatalytic activity with a reduction efficiency of about 60% for V(V) and 90% for Cr(VI). The new procedure on the simultaneous reduction of V(V) and Cr(VI) by photocatalysis may be promisingly applied in contaminated wastewaters, combining the remediation and possible V and Cr recovery.

  20. Fabrication and NO2 gas-sensing properties of reduced graphene oxide/WO3 nanocomposite films.

    PubMed

    Su, Pi-Guey; Peng, Shih-Liang

    2015-01-01

    One-pot polyol process was combined with the metal organic decomposition (MOD) method to fabricate a room-temperature NO2 gas sensor based on tungsten oxide and reduced graphene oxide (RGO/WO3) nanocomposite films. Fourier Transform infrared spectrometer (FTIR), X-ray diffractometry (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the microstructure and morphology of the fabricated films. The electrical and NO2 gas-sensing properties of WO3 to which various amounts of RGO were added were measured in detail as a function of concentration of NO2 gas at room temperature, to elucidate the contribution of RGO to the NO2 gas-sensing capacity. The NO2 gas-sensing mechanism of the RGO/WO3 nanocomposite films were explained by considering their composition and microstructures. The sensor that was based on a nanocomposite film of RGO/WO3 exhibited a strong response to low concentrations of NO2 gas at room temperature, satisfactory linearity and favorable long-term stability.

  1. Photocatalytic hydrogen production of the CdS/TiO2-WO3 ternary hybrid under visible light irradiation.

    PubMed

    Chen, Yi-Lin; Lo, Shang-Lien; Chang, Hsiang-Ling; Yeh, Hsiao-Mei; Sun, Liping; Oiu, Chunsheng

    2016-01-01

    An attractive and effective method for converting solar energy into clean and renewable hydrogen energy is photocatalytic water splitting over semiconductors. The study aimed at utilizing organic sacrificial agents in water, modeled by formic acid, in combination with visible light driven photocatalysts to produce hydrogen with high efficiencies. The photocatalytic hydrogen production of cadmium sulfide (CdS)/titanate nanotubes (TNTs) binary hybrid with specific CdS content was investigated. After visible light irradiation for 3 h, the hydrogen production rate of 25 wt% CdS/TNT achieved 179.35 μmol·h(-1). Thanks to the two-step process, CdS/TNTs-WO3 ternary hybrid can better promote the efficiency of water splitting compared with CdS/TNTs binary hybrid. The hydrogen production of 25 wt% CdS/TNTs-WO3 achieved 212.68 μmol·h(-1), under the same condition. Coating of platinum metal onto the WO3 could further promote the reaction. Results showed that 0.2 g 0.1 wt% Pt/WO3 + 0.2 g 25 wt% CdS/TNTs had the best hydrogen production rate of 428.43 μmol·h(-1). The resultant materials were well characterized by high-resolution transmission electron microscope, X-ray diffraction, scanning electron microscopy, and UV-Vis spectra.

  2. Time-resolved luminescence from Jahn-Teller split states of self-trapped excitons in PbWO4

    NASA Astrophysics Data System (ADS)

    Itoh, Minoru; Sakurai, Takaaki

    2006-06-01

    This paper reports the observation of time-resolved luminescence from a self-trapped exciton (STE) localized at tetrahedral (WO4)2- complex anion in PbWO4 . The results clearly reveal that the STE luminescence is composed of three emission bands peaking at 407, 425, and 450nm . Such a composite nature is explained well by assuming that the lowest triplet states of the STE split into three sublevels owing to the symmetry lowering from Td to C3v due to the Jahn-Teller effect. This assumption is in accordance with the theoretical prediction of Bacci [M. Bacci, S. Porcinai, E. Mihóková, M. Nikl, and K. Polák, Phys. Rev. B 64, 104302 (2001); M. Bacci, E. Mihóková, and L. S. Schulman, ibid. 66, 132301 (2002)]. The decay curve of each component and its temperature dependence are investigated in the range of 77to300K . These results are discussed on the basis of an adiabatic potential energy diagram of the triplet STE state. Time-resolved luminescence spectra are also measured for Mo-doped PbWO4 crystals. From a comparison with the spectra of undoped PbWO4 crystals, the Mo-related luminescence is clearly separated from the intrinsic luminescence due to STEs.

  3. Multi-parametric thermal sensing based on NIR emission of Ho(III) doped CaWO4 phosphors

    NASA Astrophysics Data System (ADS)

    Zhou, Xianju; Wang, Rongxue; Xiang, Guotao; Jiang, Sha; Li, Li; Luo, Xiaobing; Pang, Yu; Tian, Yili

    2017-04-01

    Optical thermometry based on trivalent rare earth doped materials has attracted much attention recently. This article reported the temperature dependent near infrared luminescence of Ho3+ doped in CaWO4 phosphors. A series of CaWO4:Ho3+ powders have been synthesized by high temperature solid state reaction. The XRD patterns showed that the Ho3+ ions have occupied the lattice sites of Ca2+ ions in the phosphors. The thermometry effect was demonstrated by different spectroscopic parameters through the emission intensity of Ho3+: 5I6 → 5I8 transition at ∼1190 nm, the spectral shift of the charge transfer band of W-O and the lifetime of Ho3+: 5F4, 5S2 excited state. These three optical parameters present a simple linear relation with the temperature in the range of 30-300 °C. This allows for accurate thermal sensing based on simultaneous measurement of these parameters. Results show that CaWO4:Ho3+ phosphors might be served as a potential candidate for thermometry.

  4. Electronic thermal conductivity, thermoelectric properties and supercapacitive behaviour of conjugated polymer nanocomposite (polyaniline-WO3) thin film

    NASA Astrophysics Data System (ADS)

    Chinedu Amaechi, Ifeanyichukwu; Nwanya, Assumpta C.; Ekwealor, Azubike B. C.; Asogwa, Paul U.; Osuji, Rose U.; Maaza, Malik; Ezema, Fabian I.

    2015-03-01

    A facile two-step, binder-free, chemical bath deposition (CBD) method was successfully employed in the synthesis of WO3 nanograins onto the matrix of conjugated polymer (polyaniline). The X-ray diffraction (XRD) results showed that the nanocomposite retained monoclinic phase of WO3 even when dispersed in polyaniline matrix. Owing to the synergistic effect offered by both the nanocomposite and structured metal oxide which may enhance the surface area, polyaniline-WO3 nanocomposite exhibited good specific capacitance. Polyaniline-WO3 yielded maximum specific capacitance ~96 F/g at scan rate of 5 mV/s in 0.5 M H2SO4 electrolyte. With the electronic thermal conductivity showing strong dependence on temperature, the estimated dimensionless figure of merit zT ~ 10-3 shows that the polymer nanocomposite (PNC) is promising as a new type of thermoelectric material. The electrochemical impedance spectroscopy showed that the PNC exhibited both pseudocapacitive and electric double layer capacitance behaviour.

  5. Flower-like and hollow sphere-like WO{sub 3} porous nanostructures: Selective synthesis and their photocatalysis property

    SciTech Connect

    Huang, Jiarui; Xu, Xiaojuan; Gu, Cuiping; Fu, Gujun; Wang, Weizhi; Liu, Jinhuai

    2012-11-15

    Graphical abstract: -- Abstract: Nanoflake-based flower-like and hollow microsphere-like hydrated tungsten oxide architectures were selectively synthesized by acidic precipitation of sodium tungstate solution at mild temperature. Several techniques, such as X-ray diffraction, scanning electron microscopy, thermogravimetric-differential thermalgravimetric analysis, transmission electron microscopy, and Brunauer–Emmett–Teller N{sub 2} adsorption–desorption analyses, were used to characterize the structure and morphology of the products. The experimental results show that the nanoflake-based flower-like and hollow sphere-like WO{sub 3}·H{sub 2}O architectures can be obtained by changing the concentration of sodium tungstate solution. The possible formation process based on the aggregation–recrystallization mechanism is proposed. The corresponding tungsten oxide three-dimensional architectures were obtained after calcination at 450 °C. Finally, the obtained WO{sub 3} three-dimensional architectures were used as photocatalyst in the experiments. Compared with WO{sub 3} microflowers, the as-prepared WO{sub 3} hollow microspheres exhibit superior photocatalytic property on photocatalytic decomposition of Rhodamine B due to their hollow porous hierarchical structures.

  6. Water photolysis effect on the long-term stability of a fiber optic hydrogen sensor with Pt/WO3

    PubMed Central

    Zhong, Xuexiang; Yang, Minghong; Huang, Chujia; Wang, Gaopeng; Dai, Jixiang; Bai, Wei

    2016-01-01

    One of the technological challenges for hydrogen sensors is long-term stability and reliability. In this article, the UV-light irradiation was introduced into the hydrogen sensing process based on water photolysis effect of Pt/WO3. Ascribing to that, fiber optic hydrogen sensor with Pt/WO3 nanosheets as the sensing element was demonstrated with significantly improved performance of stability. Under UV irradiation, the hydrogen sensor exhibits higher sensitivity and resolution together with a smaller error range than that without UV irradiation. The enhanced performance could be attributed to the effective decomposition of water produced in the hydrogen sensing process due to the water photolysis effect of Pt/WO3. The influence of the water on stability was evaluated using experimental results, and the UV irradiation to remove water was analysed by theoretical and FT-IR spectra. This work provides new strategy of UV-light irradiation to promote the long-term stability of hydrogen sensor using Pt/WO3 as the sensing element. PMID:27966631

  7. Water photolysis effect on the long-term stability of a fiber optic hydrogen sensor with Pt/WO3

    NASA Astrophysics Data System (ADS)

    Zhong, Xuexiang; Yang, Minghong; Huang, Chujia; Wang, Gaopeng; Dai, Jixiang; Bai, Wei

    2016-12-01

    One of the technological challenges for hydrogen sensors is long-term stability and reliability. In this article, the UV-light irradiation was introduced into the hydrogen sensing process based on water photolysis effect of Pt/WO3. Ascribing to that, fiber optic hydrogen sensor with Pt/WO3 nanosheets as the sensing element was demonstrated with significantly improved performance of stability. Under UV irradiation, the hydrogen sensor exhibits higher sensitivity and resolution together with a smaller error range than that without UV irradiation. The enhanced performance could be attributed to the effective decomposition of water produced in the hydrogen sensing process due to the water photolysis effect of Pt/WO3. The influence of the water on stability was evaluated using experimental results, and the UV irradiation to remove water was analysed by theoretical and FT-IR spectra. This work provides new strategy of UV-light irradiation to promote the long-term stability of hydrogen sensor using Pt/WO3 as the sensing element.

  8. Low-Temperature and Solution-Processed Amorphous WO(x) as Electron-Selective Layer for Perovskite Solar Cells.

    PubMed

    Wang, Kai; Shi, Yantao; Dong, Qingshun; Li, Yu; Wang, Shufeng; Yu, Xufeng; Wu, Mengyao; Ma, Tingli

    2015-03-05

    The electron-selective layer (ESL) is an indispensable component of perovskite solar cells (PSCs) and is responsible for the collection of photogenerated electrons. Preparing ESL at a low temperature is significant for future fabrication of flexible PSCs. In this work, solution-processed amorphous WO(x) thin film was prepared facilely at low temperature and used as ESL in PSCs. Results indicated that a large quantity of nanocaves were observed in the WO(x) thin film. In comparison with the conventional TiO2 ESL, the WO(x) ESL exhibited comparable light transmittance but higher electrical conductivity. Compared with the TiO2-based PSCs, PSCs that use WO(x) ESL exhibited comparable photoelectric conversion efficiency, larger short-circuit current density, but lower open-circuit voltage. Electrochemical characterization indicated that the unsatisfied open-circuit voltage and fill factor were caused by the inherent charge recombination. This study demonstrated that this material is an excellent candidate for ESL.

  9. Enhanced Performance of nano-Bi2WO6-Graphene as Pseudocapacitor Electrodes by Charge Transfer Channel

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Liu, Pengliang; Zhang, Yupeng; Xu, Guolong; Lu, Zhengda; Wang, Xiyu; Wang, Yan; Yang, Lingxia; Tao, Xi; Wang, Hongbo; Zhang, Erpan; Xi, Junhua; Ji, Zhenguo

    2015-02-01

    The nano-Bi2WO6/reduced graphene oxide composite obtained by a simple hydrothermal reaction demonstrates a larger specific capacitance of 922 F/g at a charge and discharge currents of 3 A/g with longer cycle life. The As comparison, pristine Bi2WO6 nanoparticles have poor specific capacitance of 574 F/g at a charge and discharge currents of 2 A/g with weak cycle life. Though analyzing the Cyclic voltammetry curves, it is found that there are two oxidation reaction occurring in the materials: oxidation of Bi (III) to Bi (IV) and Bi (III) to Bi (V). The oxidation of Bi (III) to Bi (IV) is reversible while Bi (III) to Bi (V) will cause nonreversible destroy on structure. In this nano-Bi2WO6/reduced graphene oxide composite, graphene with well conductivity will enhance the electrically conducting as charge transfer channel, so that electrons will be transfer much faster in oxidation and most Bi (III) is oxidized to be Bi (IV) which ensure larger specific capacitance and long cycle life. This nano-Bi2WO6/reduced graphene oxide composite has application prospect in high-performance pseudo-capacitors.

  10. Shape evolution of Eu-doped Bi{sub 2}WO{sub 6} and their photocatalytic properties

    SciTech Connect

    Xu, Xuetang Ge, Yuanxing Li, Bin Fan, Fangling Wang, Fan

    2014-11-15

    Highlights: • Hydrothermal synthesis of Eu-doped Bi{sub 2}WO{sub 6} micro/nanostructure without any additives. • Dopant and doping level affect the shape evolution and photocatalytic activities. • Eu-doped Bi{sub 2}WO{sub 6} exhibit superior photocatalytic activity in degradation of RhB. - Abstract: Europium-doped bismuth tungstate (Eu-doped Bi{sub 2}WO{sub 6}) was synthesized via hydrothermal method. The composition, structure, and microstructure of the products were characterized by X-ray diffraction and scanning electron microscopy. Depending on the doping level, nanoflakes and 3D hierarchical microspheres were formed. The photocatalytic activities of all products obtained were evaluated by the degradation of Rhodamine-B under visible light irradiation. A substantially improved photocatalytic performance of Eu-doped Bi{sub 2}WO{sub 6} is achieved. This study demonstrates a simple method that could produce stable photocatalysts with greatly enhanced performance.

  11. Enhanced Performance of nano-Bi2WO6-Graphene as Pseudocapacitor Electrodes by Charge Transfer Channel

    PubMed Central

    Zhang, Jun; Liu, Pengliang; Zhang, Yupeng; Xu, Guolong; Lu, Zhengda; Wang, Xiyu; Wang, Yan; Yang, Lingxia; Tao, Xi; Wang, Hongbo; Zhang, Erpan; Xi, Junhua; Ji, Zhenguo

    2015-01-01

    The nano-Bi2WO6/reduced graphene oxide composite obtained by a simple hydrothermal reaction demonstrates a larger specific capacitance of 922 F/g at a charge and discharge currents of 3 A/g with longer cycle life. The As comparison, pristine Bi2WO6 nanoparticles have poor specific capacitance of 574 F/g at a charge and discharge currents of 2 A/g with weak cycle life. Though analyzing the Cyclic voltammetry curves, it is found that there are two oxidation reaction occurring in the materials: oxidation of Bi (III) to Bi (IV) and Bi (III) to Bi (V). The oxidation of Bi (III) to Bi (IV) is reversible while Bi (III) to Bi (V) will cause nonreversible destroy on structure. In this nano-Bi2WO6/reduced graphene oxide composite, graphene with well conductivity will enhance the electrically conducting as charge transfer channel, so that electrons will be transfer much faster in oxidation and most Bi (III) is oxidized to be Bi (IV) which ensure larger specific capacitance and long cycle life. This nano-Bi2WO6/reduced graphene oxide composite has application prospect in high-performance pseudo-capacitors. PMID:25720545

  12. Controllable one-pot synthesis of a nest-like Bi2WO6/BiVO4 composite with enhanced photocatalytic antifouling performance under visible light irradiation.

    PubMed

    Ju, Peng; Wang, Yi; Sun, Yan; Zhang, Dun

    2016-03-21

    In this study, a novel visible-light-sensitive Bi2WO6/BiVO4 composite photocatalyst was controllably synthesized through a facile one-pot hydrothermal method. The Bi2WO6/BiVO4 composite exhibited a perfect nest-like hierarchical microsphere structure, which was constructed by the self-assembly of nanoplates with the assistance of polyvinylpyrrolidone (PVP). The growth mechanism of the Bi2WO6/BiVO4 composite and the effect of its structure on its photocatalytic performance was investigated and proposed. Experimental results showed that the Bi2WO6/BiVO4 composites displayed enhanced photocatalytic antifouling activities under visible light irradiation compared to pure Bi2WO6 and BiVO4. Bi2WO6/BiVO4-1 exhibited the best photocatalytic antifouling performance, and almost all (99.99%) Pseudomonas aeruginosa (P. aeruginosa), Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria were killed within 30 min. Moreover, the Bi2WO6/BiVO4-1 composite exhibited excellent stability and reusability in the cycled experiments. The photocatalytic antifouling mechanism was proposed based on the active species trapping experiments, revealing that the photo-induced holes (h(+)) and hydroxyl radicals (˙OH) could attack the cell wall and cytoplasmic membrane directly and lead to the death of bacteria. The obviously enhanced photocatalytic activity of the Bi2WO6/BiVO4-1 composite could be mainly attributed to the formation of heterojunctions, accelerating the separation of photo-induced electrons and holes. Furthermore, the large BET surface area combined with the wide photoabsorption region further improved the photocatalytic performance of the Bi2WO6/BiVO4-1 composite. This study provides a new strategy to develop novel composite photocatalysts with enhanced photocatalytic performance for marine antifouling and water purification.

  13. Study on photocurrent of bilayers photoanodes using different combination of WO{sub 3} and Fe{sub 2}O{sub 3}

    SciTech Connect

    Memar, Amir; Daud, Wan Ramli Wan; Eftekhari, Ehsan; Minggu, Lorna Jeffery; Hosseini, Soraya

    2010-08-15

    Bilayer photoanodes were prepared onto glass substrates (FTO) in order to improve generated photocurrents using UV-vis light by water splitting process. A comparative study of photocatalytic was performed over the films surface using Fe{sub 2}O{sub 3,} WO{sub 3} and mixture of bicomponents (Fe{sub 2}O{sub 3}:WO{sub 3}). Different types of films were prepared using Fe{sub 2}O{sub 3,} WO{sub 3} and bicomponents (mixture) on FTO substrates. The films were grown by sol gel method with the PEG-300 as the structure-directing agent. The photo-generated of the samples were determined by measuring the currents and voltages under illumination of UV-vis light. The morphology, structure and related composition distribution of the films have been characterized by SEM, XRD and EDX respectively. Photocurrent measurements indicated surface roughness as the effective parameter in this study. The deposited surfaces by bicomponents or mixture are flat without any feature on the surface while the deposited surfaces by WO{sub 3} appears rough surface as small round (egg-shaped particles) and cauliflower-like. The surface deposited by Fe{sub 2}O{sub 3} show rough no as well as WO{sub 3} surface. The deposited surfaces by WO{sub 3} reveal the higher value of photocurrent measurement due to surface roughness. Indeed, the roughness can be effective in increasing contact surface area between film and electrolyte and diffuse reflection (light scattering effect). The solution (Fe{sub 2}O{sub 3}:WO{sub 3}) shows the low photocurrent value in compare to WO{sub 3} and Fe{sub 2}O{sub 3} hat it may be due to decomposition the compound at 450 {+-} 1 C to iron-tungstate Fe{sub 2}(WO{sub 4}){sub 3}. (author)

  14. Ease synthesis of mesoporous WO3-TiO2 nanocomposites with enhanced photocatalytic performance for photodegradation of herbicide imazapyr under visible light and UV illumination.

    PubMed

    Ismail, Adel A; Abdelfattah, Ibrahim; Helal, Ahmed; Al-Sayari, S A; Robben, L; Bahnemann, D W

    2016-04-15

    Herein, we report the ease synthesis of mesoporous WO3-TiO2 nanocomposites at different WO3 contents (0-5wt%) together with their photocatalytic performance for the degradation of the imazapyr herbicide under visible light and UV illumination. XRD and Raman spectra indicated that the highly crystalline anatase TiO2 phase and monoclinic and triclinic of WO3 were formed. The mesoporous TiO2 exhibits large pore volumes of 0.267cm(3)g-1 and high surface areas of 180m(2)g(-1) but they become reduced to 0.221cm(3)g(-1) and 113m(2)g(-1), respectively upon WO3 incorporation, with tunable mesopore diameter in the range of 5-6.5nm. TEM images show WO3-TiO2 nanocomposites are quite uniform with 10-15nm of TiO2 and 5-10nm of WO3 sizes. Under UV illumination, the overall photocatalytic efficiency of the 3% WO3-TiO2 nanocomposite is 3.5 and 6.6 times higher than that of mesoporous TiO2 and commercial UV-100 photocatalyst, respectively. The 3% WO3-TiO2 nanocomposite is considered to be the optimum photocatalyst which is able to degrade completely (100% conversion) of imazapyr herbicide along 120min with high photonic efficiency ∼8%. While under visible light illumination, the 0.5% WO3-TiO2 nanocomposite is the optimum photocatalyst which achieves 46% photocatalytic efficiency.

  15. Global Coordination and Standardisation in Marine Biodiversity through the World Register of Marine Species (WoRMS) and Related Databases

    PubMed Central

    Bouchet, Philippe; Boxshall, Geoff; Fauchald, Kristian; Gordon, Dennis; Hoeksema, Bert W.; Poore, Gary C. B.; van Soest, Rob W. M.; Stöhr, Sabine; Walter, T. Chad; Vanhoorne, Bart; Decock, Wim

    2013-01-01

    The World Register of Marine Species is an over 90% complete open-access inventory of all marine species names. Here we illustrate the scale of the problems with species names, synonyms, and their classification, and describe how WoRMS publishes online quality assured information on marine species. Within WoRMS, over 100 global, 12 regional and 4 thematic species databases are integrated with a common taxonomy. Over 240 editors from 133 institutions and 31 countries manage the content. To avoid duplication of effort, content is exchanged with 10 external databases. At present WoRMS contains 460,000 taxonomic names (from Kingdom to subspecies), 368,000 species level combinations of which 215,000 are currently accepted marine species names, and 26,000 related but non-marine species. Associated information includes 150,000 literature sources, 20,000 images, and locations of 44,000 specimens. Usage has grown linearly since its launch in 2007, with about 600,000 unique visitors to the website in 2011, and at least 90 organisations from 12 countries using WoRMS for their data management. By providing easy access to expert-validated content, WoRMS improves quality control in the use of species names, with consequent benefits to taxonomy, ecology, conservation and marine biodiversity research and management. The service manages information on species names that would otherwise be overly costly for individuals, and thus minimises errors in the application of nomenclature standards. WoRMS' content is expanding to include host-parasite relationships, additional literature sources, locations of specimens, images, distribution range, ecological, and biological data. Species are being categorised as introduced (alien, invasive), of conservation importance, and on other attributes. These developments have a multiplier effect on its potential as a resource for biodiversity research and management. As a consequence of WoRMS, we are witnessing improved communication within the

  16. One-pot twelve tungsten phosphate acid assisted electrochemical synthesis of WO3-decorated graphene sheets for high-efficiency UV-light-driven photocatalysis

    NASA Astrophysics Data System (ADS)

    Zhao, Yuanmeng; Wei, Xiangyan; Wang, Yinyin; Luo, Fang

    2014-06-01

    In this work, WO3/graphene nanocomposite (WO3/GN) was prepared via an easy and scalable approach to decorate WO3 particles on the graphene sheets from a graphite electrode by twelve tungsten phosphate acid assisted electrochemical exfoliation. The samples were fully characterized by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The photocatalytic performance of the samples was investigated by the decomposition of the methylene blue (MB) under UV light irradiation, which is low power compared with previous published articles. The samples exhibited high degradation rate (up to 80%).

  17. Nano Ag@AgBr surface-sensitized Bi2WO6 photocatalyst: oil-in-water synthesis and enhanced photocatalytic degradation

    NASA Astrophysics Data System (ADS)

    Lin, Shuanglong; Liu, Li; Hu, Jinshan; Liang, Yinghua; Cui, Wenquan

    2015-01-01

    Nano Ag@AgBr decorated on the surface of flower-like Bi2WO6 (hereafter designated Ag@AgBr/Bi2WO6) were prepared via a facile oil-in-water self-assembly method. The photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS), etc. The characterization results indicated that nano Ag@AgBr was observed to be evenly dispersed on the surface of Bi2WO6, and was approximately 20 nm in size. Ag@AgBr/Bi2WO6 composites exhibited excellent UV-vis absorption, due to quantum dimension effect of Ag@AgBr, the surface plasmonic resonance (SPR) of Ag nanoparticles and the special flower-like structure of Bi2WO6. The photoelectrochemical measurement verified that the suitable band potential of Ag@AgBr and Bi2WO6 and the existence of metal Ag resulted in the high efficiency in charge separation of the composite. The photocatalytic activities of the Ag@AgBr/Bi2WO6 samples were examined under visible-light irradiation for the degradation of methylene blue (MB). The composite presented excellent photocatalytic activity due to the synergetic effect of Bi2WO6, AgBr, and Ag nanoparticles. The Ag@AgBr(20 wt.%)/Bi2WO6 sample exhibited the best photocatalytic activity, degrading 95.03% MB after irradiation for 2 h, which was respectively 1.29 times and 1.28 times higher than that of Ag@AgBr and Bi2WO6 photocatalyst. Meanwhile, phenol and salicylic acid were degraded to further prove the degradation ability of Ag@AgBr/Bi2WO6. Additionally, studies performed using radical scavengers indicated that O2-•, •OH and Br0 acted as the main reactive species. Based on above, a photocatalytic mechanism for organics degradation over Ag@AgBr/Bi2WO6 was proposed.

  18. Tunable work function of a WO{sub x} buffer layer for enhanced photocarrier collection of pin-type amorphous silicon solar cells

    SciTech Connect

    Fang Liang; Baik, Seung Jae; Kang, Sang Jung; Seo, Jung Won; Jeon, Jin-Wan; Lim, Koeng Su; Kim, Jeong Won; Kim, Yoon Hak

    2011-05-15

    An in situ postdeposition ultraviolet treatment was proposed to improve the electrical properties of a tungsten oxide (WO{sub x}) buffer layer of pin-type amorphous silicon-based solar cell. Based on the x-ray and ultraviolet photoelectron spectroscopy and the activation energy measurements, it was found that the work function of WO{sub x} is tunable by ultraviolet light treatment, and the collection performance of solar cells incorporating WO{sub x} with the lower work function is further improved. Moreover, the optimal band alignment scheme for a window layer is discussed in terms of obtaining enhanced carrier collection without open circuit voltage degradation.

  19. Nanocrystalline Cs{sub x}WO{sub 3} particles: Effects of N{sub 2} annealing on microstructure and near-infrared shielding characteristics

    SciTech Connect

    Liu, Jing-Xiao; Shi, Fei; Dong, Xiao-Li; Xu, Qiang; Yin, Shu; Sato, Tsugio

    2013-10-15

    In order to further improve the near-infrared shielding properties of cesium tungsten bronze (Cs{sub x}WO{sub 3}) for solar filter applications, Cs{sub x}WO{sub 3} particles were prepared by solvothermal reaction method and the effects of nitrogen annealing on the microstructure and near-infrared shielding properties of Cs{sub x}WO{sub 3} were investigated. The obtained Cs{sub x}WO{sub 3} samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and spectrophotometer. The results indicate that nanosheet-like Cs{sub x}WO{sub 3} particles with hexagonal structure began to transform into nanorods after annealed at temperature higher than 600 °C. The near-infrared shielding properties of Cs{sub x}WO{sub 3} particles could be further improved by N{sub 2} annealing at 500–700 °C. Particularly, the 500 °C-annealed Cs{sub x}WO{sub 3} samples in the N{sub 2} atmosphere showed best near-infrared shielding properties. It was suggested that the excellent near-infrared shielding ability of the 500 °C-annealed Cs{sub x}WO{sub 3} samples is correlated with its minimum O/W atomic ratio and most oxygen vacancies. Highlights: • N{sub 2} annealing could further improve the near-infrared (NIR) shielding of Cs{sub x}WO{sub 3}. • Effects of N{sub 2} annealing on microstructure and NIR shielding of Cs{sub x}WO{sub 3} were studied. • The 500 °C-N{sub 2}-annealed Cs{sub x}WO{sub 3} exhibited minimum O/W ratio and most oxygen vacancies. • The 500 °C-N{sub 2}-annealed Cs{sub x}WO{sub 3} particles exhibited best NIR shielding properties.

  20. Layer-by-layer TiO(2)/WO(3) thin films as efficient photocatalytic self-cleaning surfaces.

    PubMed

    Patrocinio, Antonio Otavio T; Paula, Leonardo F; Paniago, Roberto M; Freitag, Janna; Bahnemann, Detlef W

    2014-10-08

    New TiO2/WO3 films were produced by the layer-by-layer (LbL) technique and successfully applied as self-cleaning photocatalytic surfaces. The films were deposited on fluorine doped tin oxide (FTO) glass substrates from the respective metal oxide nanoparticles obtained by the sol-gel method. Thirty alternative immersions in pH = 2 TiO2 and pH = 10 WO3 sols resulted in ca. 400 nm thick films that exhibited a W(VI)/Ti(IV) molar ratio of 0.5, as determined by X-ray photoelectron spectroscopy. Scanning electron microscopy, along with atomic force images, showed that the resulting layers are constituted by aggregates of very small nanoparticles (<20 nm) and exhibited nanoporous and homogeneous morphology. The electronic and optical properties of the films were investigated by UV-vis spectrophotometry and ultraviolet photoelectron spectroscopy. The films behave as nanoscale heterojunctions, and the presence of WO3 nanoparticles caused a decrease in the optical band gap of the bilayers compared to that of pure LbL TiO2 films. The TiO2/WO3 thin films exhibited high hydrophilicity, which is enhanced after exposition to UV light, and they can efficiently oxidize gaseous acetaldehyde under UV(A) irradiation. Photonic efficiencies of ξ = 1.5% were determined for films constituted by 30 TiO2/WO3 bilayers in the presence of 1 ppm of acetaldehyde, which are ∼2 times higher than those observed for pure LbL TiO2 films. Therefore, these films can act as efficient and cost-effective layers for self-cleaning, antifogging applications.

  1. Magnetically recoverable TiO2-WO3 photocatalyst to oxidize bisphenol A from model wastewater under simulated solar light.

    PubMed

    Dominguez, S; Huebra, M; Han, C; Campo, P; Nadagouda, M N; Rivero, M J; Ortiz, I; Dionysiou, D D

    2016-09-27

    A novel magnetically recoverable, visible light active TiO2-WO3 composite (Fe3O4@SiO2@TiO2-WO3) was prepared to enable the photocatalyst recovery after the degradation of bisphenol A (BPA) under simulated solar light. For comparison, the photocatalytic activity of other materials such as non-magnetic TiO2-WO3, Fe3O4@SiO2@TiO2, TiO2, and the commercial TiO2 P25 was also evaluated under the studied experimental conditions. The structure and morphology of the synthesized materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and electron dispersion spectroscopy (EDS). Moreover, Brunauer-Emmett-Teller (BET) surface area and magnetic properties of the samples were determined. The Fe3O4@SiO2@TiO2-WO3 and TiO2-WO3 led to a BPA degradation of 17.50 and 27.92 %, respectively, after 2 h of the simulated solar light irradiation. Even though their activity was lower than that of P25, which degraded completely BPA after 1 h, our catalysts were magnetically separable for their further reuse in the treatment. Furthermore, the influence of the water matrix in the photocatalytic activity of the samples was studied in municipal wastewater. Finally, the identification of reaction intermediates was performed and a possible BPA degradation pathway was proposed to provide a better understanding of the degradation process. Graphical abstract ᅟ.

  2. Regulation of protein expression and function of octn2 in forskolin-induced syncytialization in BeWo Cells.

    PubMed

    Huang, F-D; Kung, F-L; Tseng, Y-C; Chen, M-R; Chan, H-S; Lin, C-J

    2009-02-01

    Placental OCTN2 is a high-affinity carnitine transporter that can interact with a number of therapeutic agents. The process of syncytialization is associated with the expression of a variety of genes. However, the association between syncytialization and OCTN2 expression is not yet clear. Given that forskolin induces BeWo cells to undergo biochemical and morphological differentiation, the purpose of the present study was to investigate whether the function and expression of OCTN2 are influenced by forskolin treatment during syncytialization. The forskolin-induced differentiation of BeWo cells was validated by secretion of beta-human chorionic gonadotropin (beta-hCG) and syncytin expression. Cellular localization of OCTN2 was analyzed by confocal microscopy. Expression of OCTN2 and the modular proteins PDZK1, PDZK2, NHERF1 and NHERF2 was analyzed by Western blotting and carnitine uptake by BeWo cells was estimated and the kinetic properties of uptake measured. The results showed that forskolin treatment increased beta-hCG secretion and syncytin expression, suggesting induction of syncytialization. Confocal images of BeWo cells showed the localization of OCTN2 in the brush-border membrane. OCTN2 protein expression was upregulated in isolated brush-border membranes by long-term forskolin treatment, but the V(m) for carnitine uptake was unchanged, although the K(m) increased. PDZK1, NHERF1 and NHERF2 protein expression in the brush-border membrane was downregulated by forskolin treatment, whereas PDZK2 levels remained unchanged. In conclusion, protein expression and function of OCTN2 in BeWo cells can be regulated by forskolin treatment. While the presence of forskolin results in an increase in OCTN2 protein expression, the increase in uptake capacity may be compensated by the decreased expression of PDZK1, NHERF1 or NHERF2.

  3. Electronic structure of ordered double perovskite Ba2CoWO6

    NASA Astrophysics Data System (ADS)

    Ray, Rajyavardhan; Himanshu, A. K.; Brajesh, Kumar; Choudhary, B. K.; Bandyopadhyay, S. K.; Sen, Pintu; Kumar, Uday; Sinha, T. P.

    2014-04-01

    Ba2CoWO6 (BCoW) has been synthesized in polycrystalline form by solid state reaction at 1200 °C. Structural characterization of the compound was done through X-ray diffraction (XRD) followed by Rietveld analysis of the XRD pattern. The crystal structure is cubic, space group Fm-3m (No. 225) with the lattice parameter, a = 8.210. Optical band-gap of the present system has been calculated using the UV-Vis Spectroscopy and Kubelka-Munk function, it's value being 2.45 eV. A detailed study of the electronic properties has also been carried out using the density functional theory (DFT) techniques implemented on WIEN2k. Importance of electron-electron interaction between the Co ions leading to half-metallic behavior, crystal and exchange splitting together with the hybridization between O and Co, W has been investigated using the total and partial density of states.

  4. Efficient operation of a diode-pumped Yb:NaY(WO(4))(2) laser.

    PubMed

    Xie, G Q; Tang, D Y; Zhang, H J; Wang, J Y; Qian, L J

    2008-02-04

    An efficient diode-pumped Yb:NaY(WO(4))(2) (Yb:NYW) disordered crystal laser has been experimentally demonstrated for the fist time. The Yb:NYW crystal has a peak absorption cross section of 1.09 x 10(-20) cm(2) at 972 nm and emission cross section of 1.24 x 10(-20) cm(2) at 1010 nm. Under an absorbed pump power of 11.7 W, the Yb:NYW laser generated an average output power as high as 4.1 W, with a slope efficiency of 45%. It was found that the laser always operated in a self-pulsing mode, and the laser spectrum showed random jumps with time. The mechanism of self-pulsing in the laser was also investigated.

  5. Atomistic Conversion Reaction Mechanism of WO3 in Secondary Ion Batteries of Li, Na, and Ca.

    PubMed

    He, Yang; Gu, Meng; Xiao, Haiyan; Luo, Langli; Shao, Yuyan; Gao, Fei; Du, Yingge; Mao, Scott X; Wang, Chongmin

    2016-05-17

    Intercalation and conversion are two fundamental chemical processes for battery materials in response to ion insertion. The interplay between these two chemical processes has never been directly seen and understood at atomic scale. Here, using in situ HRTEM, we captured the atomistic conversion reaction processes during Li, Na, Ca insertion into a WO3 single crystal model electrode. An intercalation step prior to conversion is explicitly revealed at atomic scale for the first time for Li, Na, Ca. Nanoscale diffraction and ab initio molecular dynamic simulations revealed that after intercalation, the inserted ion-oxygen bond formation destabilizes the transition-metal framework which gradually shrinks, distorts and finally collapses to an amorphous W and Mx O (M=Li, Na, Ca) composite structure. This study provides a full atomistic picture of the transition from intercalation to conversion, which is of essential importance for both secondary ion batteries and electrochromic devices.

  6. Voigt wave investigation in the KGd(WO4)2:Nd biaxial laser crystal

    NASA Astrophysics Data System (ADS)

    Brenier, Alain

    2015-07-01

    We have investigated the Nd3+-doped KGd(WO4)2 biaxial laser crystal for wave propagation directions in the vicinity of the optical axis at wavelengths tunable around 800 nm. The angular absorption distribution was found to be strongly anisotropic. Increasing absorption, the optical axis splits in two new ones able to propagate unchanged a left or a right circularly polarized light and able to propagate a circularly polarized Voigt wave with a linear spatial dependence. The intensities of the transmitted light in different configurations of polarizations were investigated. The angular displacement of the two optical axes versus the absorbed wavelengths was measured and explained with a single oscillator model. The light energy propagation was found distributed inside a crescent-shaped area.

  7. Casein hydrolysate for uterine infection treatment: a patent evaluation (WO2011132191).

    PubMed

    Cozza, Giorgio

    2012-05-01

    Metritis, endometritis and pyometra are common uterus inflammatory diseases, occurring mainly in the early postpartum period of livestock and farm animals. These infections are primarily associated with contamination of the reproductive tract, in particular uterine. Uterine infections bring to uterine and cervical involution as well as sub-fertility; the high economic loss, due to costs for treatment, milk withdrawal, reduced reproductive performance and premature culling, clearly demonstrate that uterine health in the postpartum period requires substantial medical veterinary attention. A wide variety of therapies for endometritis have been reported, including mainly antibiotics administered either by systemic or local somministration. Here, the patent application WO/2011/132191, which describes an alternative treatment for uterine infection, using casein peptides, is evaluated and discussed.

  8. Ferroelectric properties of highly c-oriented epitaxial Bi2WO6 thin films

    NASA Astrophysics Data System (ADS)

    Ahn, Yoonho; Son, Jong Yeog

    2017-03-01

    Bi2WO6 (BWO) thin films were epitaxially deposited onto single crystal Nb-doped SrTiO3 substrates via pulsed laser deposition (PLD). To control the growth mode of the BWO thin films, the deposition rate was varied from 0.01 to 0.4 nm/pulse. The BWO thin films yielded an island growth mode during a rapid deposition rate of 0.4 nm/pulse. On the other hand, a layer-by-layer growth mode was achieved with a low deposition rate of 0.01 nm/pulse. We could obtain highly c-oriented epitaxial BWO thin films by means of the layer-by-layer mode. Piezoresponse force microscopy revealed that the highly c-oriented epitaxial BWO thin films possessed spontaneous polarizations that were perpendicular to the c-axis.

  9. Two-dimensional, high valence-doped ceria: Ce6WO12(100)/W(110)

    NASA Astrophysics Data System (ADS)

    Stetsovych, Vitalii; Skála, Tomáš; Beran, Jan; Dvořák, Filip; Mazur, Daniel; Tsud, Nataliya; Mašek, Karel; Mysliveček, Josef; Matolín, Vladimír

    2016-05-01

    Doping of oxides for catalytic applications represents one of the most used strategies for improving their catalytic performance. Model catalyst systems for doped oxides that would contain the dopant atoms in a well-defined geometry allowing for investigation of relationships between structure and reactivity are however rare. Here we report on preparation and structural properties of two-dimensional W-doped ceria on W(110) substrate. This model system adopts geometry of two-dimensional Ce6WO12 (100)-oriented thin film, including isolated W6+ ions that donate the charge to Ce3+ ions and act as high-valence dopants. The system represents a model catalyst for prospective use in investigating the role of W6+ active sites in CeOx-WOx catalysts and high valence dopants in ceria in general.

  10. Stability and Demulsification of Water-in-Crude Oil (w/o) Emulsions Via Microwave Heating

    NASA Astrophysics Data System (ADS)

    Nour, Abdurahman. H.; Rosli; Yunus, Mohd.

    Formation of emulsions during oil production and processing is a costly problem, both in terms of chemicals used and production losses. Experimental data are presented to show the influences of Triton X-100, Low sulphur Wax Residue (LSWR), Sorbitan monooleate (Span 83) and Sodium Dedocyl Sulphate (SDDS) on the stability and microwave demulsification of emulsions. It was found that emulsion stability was related to some parameters such as, the surfactant concentrations, water-oil phase ratio (10-90%), temperature and agitation speed. For economic and operational reasons, it is necessary to separate the water completely from the crude oils before transporting or refining them. In this regard, the present study found that microwave radiation method can enhance the demulsification of water-in-oil (w/o) emulsions in a very short time compared to the conventional heating methods.

  11. Long-Range Magnetic Interactions in the Multiferroic Antiferromagnet MnWO4

    SciTech Connect

    Ye, Feng; Fishman, Randy Scott; Fernandez-Baca, Jaime A; Podlesnyak, Andrey A; Ehlers, Georg; Mook Jr, Herbert A; Wang, Y.-Q.; Lorenz, Bernd; Chu, C. W.

    2011-01-01

    The spin-wave excitations of the multiferroic MnWO4 have been measured in its low-temperature collinear commensurate phase using high-resolution inelastic neutron scattering. These excitations can be well described by a Heisenberg model with competing long-range exchange interactions and a single-ion anisotropy term. We find that the magnetic interactions are strongly frustrated within the zigzag spin chain along c-axis and between chains along the a-axis, while the coupling between spin along the b-axis is much weaker. We argue that the balance of these interactions results in the noncollinear incommensurate spin structure associated with the magnetoelectric effect, and the perturbation of the magnetic interactions leads to the observed rich phase diagrams of the chemically-doped materials. This delicate balance can also be tuned by the application of external electric or magnetic fields to achieve practical magnetoelectric control of this type of materials.

  12. Gas-deposited WO3 nanoparticles studied by scanning force microscopy

    NASA Astrophysics Data System (ADS)

    Kopniczky, Judit; Hoel, Anders; Mechler, A.; Heszler, Peter; Granqvist, Claes-Goran

    2004-05-01

    WO3 nanoparticles were generated by gas deposition. Deposits on Al substrates were studied by scanning force microscopy operated in the intermittent-contact (tapping) mode. At low surface coverage (< 0.5 %), we observed single nanoparticles with a mean size of ~ 1.5 nm. An increase of the amount of particles led to agglomerates, which appeared at surface coverages as low as 2 to 4 %. At full coverage the mean agglomerate size was ~ 5 nm. This value did not change as the sample was annealed at temperatures up to 250 °C. The size distribution of the agglomerates was found to be log-normal, i.e., similar to the size distribution of the gas-phase nanoparticles forming the deposit. For explaining the obtained log-normal size distribution of the agglomerates simulations of the agglomeration process were also carried out.

  13. Electrical transport properties of potassium germanide tungstates (K10Ge18WO4): A theoretical study

    NASA Astrophysics Data System (ADS)

    Azam, Sikander; Reshak, A. H.

    2014-06-01

    The total and partial density of states, electronic charge density and optical properties of the monoclinic structure K10Ge18WO4 compound have been investigated using a full relativistic version of the full-potential augmented plane-wave method based on the density functional theory, within local density approximation (LDA), generalized gradient approximation (GGA) and Engel-Vosko GGA (EVGGA). Density of states discloses the semiconductor nature of the calculated compound. There exists a strong hybridization between K-p and K-s, W-d and O-p, W-f and K-p. The analysis of the chemical bonding shows that the bonding possesses strong covalent nature. The dielectric optical properties were also calculated and discussed in detail. The electrical transport coefficients of the under observation compound have been investigated using the density functional theory calculation within EVGGA.

  14. Blue Upconversion Luminescence in Tm3+/Yb3+ Codoped CaWO4 Polycrystals

    NASA Astrophysics Data System (ADS)

    Xu, Yan-Ling; Wang, Yun-Long; Shi, Lian-Sheng; Tan, Xiang

    2013-08-01

    We investigate the upconversion emission of CaWO4:Tm3+/Yb3+ polycrystals prepared by the high-temperature solid-state method. The crystal structure of the polycrystals is characterized by means of x-ray diffraction. Under the excitation of a 980 nm continuous wave diode laser, the samples show intense blue upconversion emissions centered at 473 nm, corresponding to the 1G4→3H6 transition of Tm3+. The dependence of the upconversion emission intensity on the pump power of a laser diode is measured, and the results indicate that the two-photon and three-photon processes contribute simultaneously to the blue upconversion emissions. The possible multi-photon upconversion process and upconversion mechanisms are discussed.

  15. Electronic energy band structure of the double perovskite Ba2MnWO6.

    PubMed

    Fujioka, Yukari; Frantti, Johannes; Nieminen, Risto M

    2008-06-05

    The electronic and magnetic structures of the double perovskite oxide Ba 2MnWO6 (BMW) were determined by employing the density functional theory within the generalized gradient approximation (GGA) + U approach. BMW is considered a prototype double perovskite due to its high degree of B-site ordering and is a good case study for making a comparison between computations and experiments. By adjusting the U-parameter, the electronic energy band structure and magnetic properties, which were consistent with the experimental results, were obtained. These computations revealed that the valence bands are mainly formed from Mn 3d and O 2p states, while the conduction bands are derived from W 5d and O 2p states. The localized bands composed from Mn 3d states are located in the bandgap. The results imply that the formation of polarons in the conduction band initiate the resonance Raman modes observed as a series of equidistant peaks.

  16. Understanding Electrical Conduction States in WO3 Thin Films Applied for Resistive Random-Access Memory

    NASA Astrophysics Data System (ADS)

    Ta, Thi Kieu Hanh; Pham, Kim Ngoc; Dao, Thi Bang Tam; Tran, Dai Lam; Phan, Bach Thang

    2016-05-01

    The electrical conduction and associated resistance switching mechanism of top electrode/WO3/bottom electrode devices [top electrode (TE): Ag, Ti; bottom electrode (BE): Pt, fluorine-doped tin oxide] have been investigated. The direction of switching and switching ability depended on both the top and bottom electrode material. Multiple electrical conduction mechanisms control the leakage current of such switching devices, including trap-controlled space-charge, ballistic, Ohmic, and Fowler-Nordheim tunneling effects. The transition between electrical conduction states is also linked to the switching (SET-RESET) process. This is the first report of ballistic conduction in research into resistive random-access memory. The associated resistive switching mechanisms are also discussed.

  17. Hole capture in PbWO{sub 4}:Mo,La(Y) scintillator crystals

    SciTech Connect

    Laguta, V. V.; Buryi, M.; Nikl, M.; Rosa, J.; Zazubovich, S.

    2011-03-01

    The processes of hole localization in PbWO{sub 4}:Mo,La(Y) single crystals were investigated by electron spin resonance. It was found that the holes created by uv irradiation are trapped at the regular oxygen ions in the vicinity of perturbing defects such as lead vacancies, impurity ions (La,Y), and other lattice imperfections. This leads to a variety of O{sup -} centers which differ in both the thermal stability (from about 160 K up to 240 K) and spectroscopic parameters. The thermal release of such trapped holes and their subsequent recombination with electrons stored at different traps, including (MoO{sub 4}){sup 3-} complexes, are accompanied by the appearance of the thermally stimulated luminescence peaks located at around 190 K and in the 225-250 K range.

  18. High-efficiency continuous-wave Raman conversion with a BaWO(4) Raman crystal.

    PubMed

    Fan, Li; Fan, Ya-Xian; Li, Yu-Qiang; Zhang, Huaijin; Wang, Qin; Wang, Jin; Wang, Hui-Tian

    2009-06-01

    We report a high-efficiency cw Raman conversion with a BaWO(4) Raman crystal in a diode-end-pumped Nd:YVO(4) laser. The Raman threshold is as low as 3.6 W of diode power at 808 nm. The highest output power obtained at the 1,180 nm first-order Stokes line is 3.36 W under the diode power of 25.5 W, corresponding to a slope efficiency of 15.3% and a diode-to-Stokes optical conversion efficiency of 13.2%. The intracavity Raman conversion efficiency is 21.5% with respect to the available output of the 1,064 nm fundamental.

  19. Lasing with conical diffraction feature in the KGd(WO4)2:Nd biaxial crystal

    NASA Astrophysics Data System (ADS)

    Brenier, Alain

    2016-09-01

    With an experimental set-up designed to record simultaneously the far-field and the near-field patterns, we got lasing with feature of conical diffraction in the biaxial Nd3+-doped KGd(WO4)2 crystal. The key-point is that the lasing direction is not single and is constituted by an angular distribution including the optical axis. Very slight changes of crystal orientation leads to crescent shape 1068-nm light distributions in the near-field. The beam launched towards the biaxial crystal is mainly linear polarized with its intensity in agreement with the Nd fluorescence angular distribution. A theoretical background is provided, including the monoclinic and triclinic symmetries and laser amplification including elliptical modes and cavity round trip.

  20. Cathodic shift of onset potential for water oxidation of WO3 photoanode by Zr+ ions implantation

    NASA Astrophysics Data System (ADS)

    Wu, Hengyi; Ren, Feng; Xing, Zhuo; Zheng, Xudong; Wu, Liang; Jiang, Changzhong

    2017-02-01

    Tungsten trioxide is one of the most widely studied semiconductors for photoelectrochemical water splitting. However, its onset potential is too positive. In a photoelectrochemical system, a low onset potential and a high photocurrent for a photoanode are important for enhancing the efficiency of water splitting. It is an effective way to adjust the onset potential by changing the conduction and valence band level. Doping is a powerful way to alter the positions of the energy levels of semiconductors to improve their photoelectrochemical performance. In this paper, we present a method of ion implantation to alter the energy levels by implanting Zr+ ions into WO3. Cathodic shifts of the photocurrent onset potential for water oxidation are achieved. The systematic studies show that ion implantation followed by thermal annealing treatment can form substitutional Zr4+ in WO3. The upward shifts of the conduction band and valence band lead to the cathodic shifts of the onset potential. Two combined factors lead to the upward shift of the conduction band. One is strain induced after doping in the lattices. Another is due to the higher energy level of the Zr 4d orbital than the W 5d orbital. Meanwhile, the oxygen vacancy introduced during the ion implantation can cause an upward shift the valence band maximum. The results indicate that the upward shifts of the conduction band minimum and valence band maximum are good for the photoelectrochemical water splitting. It also shows that an ion implantation technique combined with thermal annealing could be an effective way to enhance the performance of the photoanode for water splitting.

  1. Kinetic behavior of WO3-doped Nb2O5 electrochromic thin films

    NASA Astrophysics Data System (ADS)

    Melo, Luciana O.; Dragunski, Douglas C.; Avellaneda, Cesar O.; Pawlicka, Agnieszka

    2003-07-01

    An electrochromic material (EC) reversibly changes its optical characteristics response, coloring and bleaching states when a small voltage or current is passed through it. This phenomenon is used to develop electrochromic devices like smart windows, which control the amount of heat and light entering in a building and optimize energy consumption. The change of the transparency of these devices involves the injection and extraction of small cations and electrons into the EC material and study of the kinetics of ions injection implies on operation understanding of these devices. Pure and doped niobium oxides (Nb2O5) are promising cathodic electrochromic materials and their electrooptical performance depends strongly of its structural morphology. The sol-gel process allows for facile fabrication of large area coatings at a low cost and offers advantages of controlling the composition and microstructure of the films. In order to study the solid sate diffusion of lithium into Nb2O5, Nb2O5:Li+ and Nb2O5:WO3, two electroanalytical techniques have been used i.e. galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS). GITT have been applied in order to obtain the chemical diffusion coefficient of Lix in Nb2O5 doped and undoped films, where the values approaching were of the 2.5x10-11 cm2s-1 at x=0,83, 7.4x10-13 cm2s-1 at x=1.65 and 1.6x10-10 cm2s-1 at x=0.33 for Nb2O5, Nb2O5:Li+ and Nb2O5-WO3 respectively. From these measurements it was also observed that within each film, D increases as x increases.

  2. Tuning the hopping conductivity of WO3 films by ion bombardment at different temperatures

    NASA Astrophysics Data System (ADS)

    Heinz, B.; Merz, M.; Widmayer, P.; Ziemann, P.

    2001-10-01

    WO3 films, either prepared by sputtering or evaporation under high or ultrahigh vacuum conditions, were irradiated with He+ and Ar+ ions (energy range 300-350 keV) at ambient and low temperatures (77-100 K). The resulting ion induced changes of the optical absorption as well as of the electrical conductivity could be determined on one and the same sample, which enables the variable range hopping (VRH) model to be tested under the assumption that the density of irradiation induced color centers is proportional to the electronic density of states contributing to the hopping conductivity. It is found that the data obtained at 300 K for He+ and Ar+ bombardment can be described within the VRH model by one common conductivity versus absorption curve, even though the effectiveness per projectile of the heavier ion for coloration as well as for increasing the conductivity is much higher. This is different at low temperatures. While the ion induced coloration is practically independent of the irradiation temperature for both projectiles, the effectiveness per projectile to enhance the conductivity is interchanged. This is attributed to the additional damage produced by the heavier ion at low temperatures resulting in strongly impeded hopping processes. Consistent with the VRH model, the temperature dependence of the conductivity of ion bombarded WO3 films follow the Mott "T-1/4" law, if the ion induced conductivity is not too high. For very high ion fluences clear deviations from the VRH model are observed for the conductivity versus absorption curves accompanied by a shift of the above power laws from T-1/4 towards T-1/2.

  3. High energy intracavity pumped eye-safe BaWO4 Raman laser

    NASA Astrophysics Data System (ADS)

    Kitzler, Ondrej; Jelínková, Helena; Å ulc, Jan; Koubíková, Lucia; Němec, Michal; Nejezchleb, Karel; Å koda, Václav

    2013-03-01

    The goal of our research is a compact Raman laser emitting short pulses with high energy and peak power in "eye-safe" region around wavelength 1.5 μm. We utilize intracavity conversion of giant pulses at wavelength 1.34 μm in a BaWO4 Raman crystal (18 mm long, AR coated). Required high energy and peak power was reached using a flash-lamp pumped Nd:YAG laser (rod 100 mm long, diameter 4 mm), Q-switched by V:YAG solid-state saturable absorber (initial transmission 37% @ 1.34 μm). The L-shaped oscillator for 1.34 μm radiation consisted of a concave mirror (r = 0.5 m, HR @ 1.3 μm, HT @ 1.06 μm), flat polarizing intracavity mirror, and output coupler (r = 1 m, HR @ 1.3 μm, R = 39 % @ 1.5 μm). The polarizing mirror ensured stable linearly polarized laser emission and prevented parasitic oscillations at 1.06 μm. The Raman laser oscillator was formed by the output coupler and another intracavity mirror (r = 0.5 m, HR @ 1.5 μm, HT @ 1.3 μm), inserted between BaWO4 and the polarizing mirror. For pumping energy of 28.2 J stable vertically polarized generation of the 1st Stokes radiation at 1528 nm was reached. In multimode operation the output energy was 20 mJ in 2.25 ns pulses. Single mode operation was possible by inserting a 1.5 mm aperture between Nd:YAG and V:YAG crystal. The output energy dropped to 9.7 mJ (even for higher pump power of 30.7 W) and output pulses were shortened to 1.87 ns.

  4. Kinetics of silica particle formation in nonionic W/O microemulsions from TEOS

    SciTech Connect

    Chang, C.L.; Fogler, H.S.

    1996-11-01

    The kinetics of silica particle formation by the ammonia-catalyzed hydrolysis of tetraethyl orthosilicate (TEOS) in water-in-oil (W/O) microemulsions containing a nonionic surfactant was investigated using Fourier-transform infrared spectroscopy, transmission electron microscopy, and light-scattering techniques. The results show that TEOS hydrolysis and silica-particle growth occur at the same rate, indicating the growth of silica particles is rate-controlled by the hydrolysis of TEOS. The rate of TEOS hydrolysis in microemulsions is first order with respect to the concentration of aqueous ammonia (29 wt. % NH{sub 3}), but depends weakly on the concentration of water. Based on the fact that TEOS hydrolysis follows a nucleophilic substitution of the TEOS`s ethoxy group with hydroxyl ion, the kinetic data suggest that both water and ammonia remain predominantly in W/O microemulsion droplets. The rate of TEOS hydrolysis also depends on the surfactant concentration that controls the molecular contact between hydroxyl ions and TEOS in the solution. Due to the reaction-controlled growth mechanism, the silica-particle size distribution retains virtually the same shape over the growth period. The final average size of silica particles can be varied from 26 to 43 nm by adjusting concentrations of water and surfactant. Increasing the water concentration decreases the average size and uniformity of silica particles. For a given water concentration, the smallest and most uniform silica particles are produced at intermediate water-to-surfactant molar ratios (about 1.9). The results are discussed in terms of the effect of water concentration on the stability of the hydrolyzed silica reacting species during the nucleation of particles and of the water-to-surfactant molar ratio on the compartmentalization of silica species in microemulsions.

  5. A Cs(x)WO3/ZnO nanocomposite as a smart coating for photocatalytic environmental cleanup and heat insulation.

    PubMed

    Wu, Xiaoyong; Yin, Shu; Xue, Dongfeng; Komarneni, Sridhar; Sato, Tsugio

    2015-10-28

    A novel CsxWO3/ZnO smart coating was proposed to achieve multiple functions, such as heat insulation, photodecomposition of toxic NO gas, blocking of harmful UV light, etc. In this composite coating, CsxWO3 nanorods were used as a NIR and UV light shielding material while ZnO nanoparticles were utilized as a photocatalyst and a material to enhance visible light transmittance and block UV light. When the mass ratio of CsxWO3/ZnO was 1, the composite coating possessed a very good visible light transmittance of over 80% and an excellent UV-shielding ability. This novel coating showed heat insulation that is superior to the ITO coating and photocatalytic decontamination of NO gas that is superior to the standard TiO2 (P25). The proposed CsxWO3/ZnO smart coating is a promising material not only for energy saving but also for environmental cleanup.

  6. WO x , SiO2, TiO2/Ti composites, fabricated by means of plasma electrolytic oxidation, as catalysts of ethanol dehydration into ethylene

    NASA Astrophysics Data System (ADS)

    Vasilyeva, M. S.; Rudnev, V. S.; Tulush, A. I.; Nedozorov, P. M.; Ustinov, A. Yu.

    2015-06-01

    WO3, SiO2, TiO2/Ti composites are fabricated and studied by means of X-ray diffraction analysis and X-ray photoelectron and IR spectroscopy. It is established that the surface of an oxide coating contains up to 2% of tungsten in the composition of WO3, SiO2, and TiO2, along with carbon compounds. Data on the catalytic activity of SiO2, TiO2/Ti and WO3, SiO2, TiO2/Ti composites in ethanol dehydration are obtained. In the case of WO3, SiO2, TiO2/Ti composites, the degree of conversion and the selectivity of ethanol transformation into ethylene at 480°C reaches 97%.

  7. Maximizing the photo catalytic and photo response properties of multimodal plasmonic Ag/WO(3-x) heterostructure nanorods by variation of the Ag size.

    PubMed

    Ghosh, Sirshendu; Saha, Manas; Paul, Sumana; De, S K

    2015-11-21

    High quality nearly monodisperse colloidal WO3-x nanorods with an aspect ratio ∼18 were synthesized using the thermal decomposition technique. The effects of a capping agent and an activating agent on the nanorod aspect ratio have been studied. Excess carrier concentration due to large oxygen vacancy and smaller width of the nanorods compared to the Bohr exciton radius gives rise to an increase of the band gap. Shape anisotropy in nanorods results in two plasmonic absorbance bands at about 890 nm and 5900 nm corresponding to short axis and long axis plasmon modes. The short axis mode reveals an excellent plasmonic sensitivity of ∼345 nm per refractive index. A plasmonic photocatalysis process based on WO3-x nanorods has been developed to synthesize Ag/WO3-x heterostructures consisting of multiple Ag dots with ∼2 nm size, randomly decorated on the surface of the WO3-x nanorods. Long time irradiation leads to an increase in the size (5 nm) of Ag nanocrystals concomitant with decrease in the number of Ag nanocrystals attached per WO3-x nanorod. Plasmonic photocatalysis followed by thermal annealing produces only one Ag nanocrystal of size ∼10 nm on each WO3-x nanorod. Red shifting and broadening of plasmon bands of Ag nanocrystals and WO3-x nanorods confirm the formation of heterostructures between the metal and semiconductor. Detailed transmission electron micrograph analysis indicates the epitaxial growth of Ag nanocrystals onto WO3-x nanorods. A high photocurrent gain of about 4000 is observed for Ag (10 nm)/WO3-x heterostructures. The photodegradation rate for Rhodamine-B and methylene blue is maximum for Ag (10 nm)/WO3-x heterostructures due to efficient electron transfer from WO3-x nanorods to Ag nanocrystals. Metal plasmon-semiconductor exciton coupling, prominent plasmon absorbance of metal nanoparticles, and formation of an epitaxial interface are found to be the important factors to achieve the maximum photocatalytic activity and fabrication of a

  8. Exploration on anion ordering, optical properties and electronic structure in K{sub 3}WO{sub 3}F{sub 3} elpasolite

    SciTech Connect

    Atuchin, V.V.; Isaenko, L.I.; Kesler, V.G.; Lin, Z.S.; Molokeev, M.S.; Yelisseyev, A.P.; Zhurkov, S.A.

    2012-03-15

    Room-temperature modification of potassium oxyfluorotungstate, G2-K{sub 3}WO{sub 3}F{sub 3}, has been prepared by low-temperature chemical route and single crystal growth. Wide optical transparency range of 0.3-9.4 {mu}m and forbidden band gap E{sub g}=4.32 eV have been obtained for G2-K{sub 3}WO{sub 3}F{sub 3} crystal. Meanwhile, its electronic structure has been calculated with the first-principles calculations. The good agreement between the theorectical and experimental results have been achieved. Furthermore, G2-K{sub 3}WO{sub 3}F{sub 3} is predicted to possess the relatively large nonlinear optical coefficients. - Graphical abstract: Using the cm-size K{sub 3}WO{sub 3}F{sub 3} crystal (left upper), the transmission spectrum (right upper) and XPS valence electronic states (left lower) were measured, agreed with the ab initio results (right lower). Highlights: Black-Right-Pointing-Pointer The cm-size G2-K{sub 3}WO{sub 3}F{sub 3} single crystals are obtained. Black-Right-Pointing-Pointer Optical absorption edge and transmission range are defined for G2-K{sub 3}WO{sub 3}F{sub 3} crystal. Black-Right-Pointing-Pointer Crystal structures of all known K{sub 3}WO{sub 3}F{sub 3} polymorph modifications are determined. Black-Right-Pointing-Pointer Experimental electronic structure is consistent with the first-principles result. Black-Right-Pointing-Pointer G2-K{sub 3}WO{sub 3}F{sub 3} is predicted as a crystal with large NLO coefficients.

  9. TiO{sub 2} nanobelts photocatalysts decorated with Bi{sub 2}WO{sub 6} nanocrystals: Preparation and enhanced photocatalytic activity

    SciTech Connect

    Li, Yang; Wu, Wenjian; Wu, Mingzai; Dai, Peng; Zhang, Lili; Sun, Zhaoqi; Li, Guang; Liu, Xiansong; Chen, Xiaoshuang; Zheng, Xiuwen

    2014-07-01

    Highlights: • TiO{sub 2} nanobelts decorated with Bi{sub 2}WO{sub 6} nanocrystals have been prepared. • The introduction of Bi{sub 2}WO{sub 6} nanocrystals can induce red-shift of absorption edge. • The Bi{sub 2}WO{sub 6}/TiO{sub 2} composites show higher photocatalytic activity than TiO{sub 2} nanobelts. • The Bi{sub 2}WO{sub 6}/TiO{sub 2} composites have long-time recyclable ability of photodegradation. - Abstract: In this paper, the controllable preparation of one-dimensional TiO{sub 2} nanobelts decorated with Bi{sub 2}WO{sub 6} nanocrystals based on Ti foils was reported using two-step hydrothermal treatment method. X-ray photoelectron spectroscopy measurement results exhibited the binding energy changes of Ti and O elements, implying the strong adhesion of Bi{sub 2}WO{sub 6} nanocrystals onto the surface of TiO{sub 2} nanobelts. The ultraviolet–visible (UV–vis) absorption spectra showed that the introduction of Bi{sub 2}WO{sub 6} nanocrystals could induce the red-shift of absorption edge and exhibited a broad absorption band in the visible region, which extended the scope of absorption spectrum and help to improve the photocatalytic degradation efficiency. The photocatalytic experiment results revealed that Bi{sub 2}WO{sub 6}/TiO{sub 2} composites possess higher photocatalytic activities toward methyl orange than pure TiO{sub 2} nanobelts. The degradation efficiency of 90% after 5 cycles indicated that the as-prepared composite photocatalysts exhibited excellent long-time recyclable ability for the degradation of contaminants.

  10. Three-dimensional Ag{sub 2}O/WO{sub 3}·0.33H{sub 2}O heterostructures for improving photocatalytic activity

    SciTech Connect

    He, Xiaoyu; Hu, Chenguo; Xi, Yi; Zhang, Kaiyou; Hua, Hao

    2014-02-01

    Highlights: • Ag{sub 2}O/WO{sub 3}·0.33H{sub 2}O 3D network heterostructures are prepared via a simple precipitatation method. • Ag{sub 2}O/WO{sub 3}·0.33H{sub 2}O networks exhibit much enhanced photocatalytic activity. • High photocatalytic activity is attributed to its heterostructure and 3D architectures. - Abstract: Three-dimensional Ag{sub 2}O/WO{sub 3}·0.33H{sub 2}O heterostructures were fabricated by loading Ag{sub 2}O nanoparticles on WO{sub 3}·0.33H{sub 2}O 3D networks via a simple chemical precipitation method. The Ag{sub 2}O/WO{sub 3}·0.33H{sub 2}O heterostructures exhibited much enhanced photocatalytic activity for the degradation of methylene blue (MB) under simulated solar light irradiation. The optimal molar ratio of Ag{sub 2}O and WO{sub 3}·0.33H{sub 2}O is 1:2. The outstanding photocatalytic activity of the Ag{sub 2}O/WO{sub 3}·0.33H{sub 2}O can be attributed to its large surface area of the three-dimensional networks, the enhanced sunlight absorption and the prevention of electrons–holes combination from the heterostructures. The experiment result demonstrates that wide band gap semiconductor (WO{sub 3}·0.33H{sub 2}O) modified by narrow band gap metal oxide (Ag{sub 2}O) with 3D architecture will be an effective route to enhance its photocatalytic activity.

  11. Ultrasonic-assisted preparation of plasmonic ZnO/Ag/Ag2WO4 nanocomposites with high visible-light photocatalytic performance for degradation of organic pollutants.

    PubMed

    Pirhashemi, Mahsa; Habibi-Yangjeh, Aziz

    2017-04-01

    In this work, plasmonic ternary ZnO/Ag/Ag2WO4 nanocomposites as efficient visible-light-driven photocatalysts prepared by a facile ultrasonic-irradiation method. The as-prepared samples were characterized by XRD, SEM, TEM, EDX, XPS, UV-vis DRS, FT-IR, and PL techniques. The photocatalytic performance of the prepared ZnO/Ag/Ag2WO4 nanocomposites were evaluated by photodegradations of rhodamine B, methylene blue, methyl orange, and fuchsine under visible-light irradiation. The optimal nanocomposite with 15wt% of Ag/Ag2WO4 to ZnO showed the highest photocatalytic activity for RhB degradation, which is about 95 and 19 times higher than those of the Ag/Ag2WO4 and ZnO samples, respectively. The highly enhanced activity of the ZnO/Ag/Ag2WO4 (15%) nanocomposite was attributed to the surface plasmon resonance effect of metallic silver and the formation of heterojunctions between the counterparts, which effectively suppresses recombination of the photogenerated charge carriers. Lastly, the plasmon-enhanced photocatalytic mechanism associated with the ZnO/Ag/Ag2WO4 nanocomposites was discussed.

  12. In situ fabrication of novel Z-scheme Bi2WO6 quantum dots/g-C3N4 ultrathin nanosheets heterostructures with improved photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Liu, Tian-Yu; Huang, Ting; Liu, Xiao-Heng; Zhu, Jun-Wu; Duan, Guo-Rong; Yang, Xu-Jie

    2015-11-01

    The use of solar energy is a promising means for pollution abatement or environmental remediation. In the present work, we report the design and fabrication of Bi2WO6 QDs/g-C3N4 binary heterojunction photocatalysts with highly efficient solar light response, wherein the Bi2WO6 QDs were in situ uniformly immobilized on porous g-C3N4 ultrathin nanosheets (NSs) by one-pot hydrothermal strategy. The photocatalytic performance of the Bi2WO6 QDs/g-C3N4 NSs hybrid composites was evaluated for the photodegradation of Rhodamine B (RhB). It was found that the mass ratio of Bi2WO6 QDs to g-C3N4 nanosheets in the composites significantly affects the photocatalytic activity. Higher amounts of g-C3N4 nanosheets in Bi2WO6 QDs/g-C3N4 composites showed lower photocatalytic activity. The composite with 10 mg g-C3N4 nanosheets exhibited the highest photocatalytic activity, with nearly 11-fold enhancement in photocatalytic efficiency over pure Bi2WO6 QDs. Different from previous reports, a novel Z-scheme photocatalytic mechanism was proposed to explain the enhanced the photocatalytic efficiency.

  13. Crystal structure and superconductivity of rubidium tungsten bronzes Rb{sub x}WO{sub 3} prepared by a hybrid microwave method

    SciTech Connect

    Guo Juan Dong Cheng; Yang Lihong; Chen Hong

    2008-04-01

    The rubidium tungsten bronzes Rb{sub x}WO{sub 3} have been prepared from Rb{sub 2}CO{sub 3}, WO{sub 3} and W powders using hybrid microwave method. The single hexagonal phase samples can be obtained as actual rubidium content x in the range of 0.21-0.33, and their lattice parameters a and c linearly drop and rise with the increase of rubidium content respectively. For samples with x = 0.14, 0.16, 0.18, the superconducting transition temperature T{sub c} from resistivity measurements does not change with the rubidium content, while T{sub c} from susceptibility measurements shows a decrease from 5.3 K for x = 0.14 to 4.8 K for x = 0.18. The charge density wave (CDW) transition appears in Rb{sub 0.21}WO{sub 3}, Rb{sub 0.23}WO{sub 3} and Rb{sub 0.25}WO{sub 3} at about 200-260 K. The CDW transition is most obvious in Rb{sub 0.23}WO{sub 3} which shows the lowest degree of crystallization among the samples.

  14. Preparation of Er(3+):Y3Al5O12/WO3-KNbO3 composite and application in treatment of methamphetamine under ultrasonic irradiation.

    PubMed

    Zhang, Hongbo; Huang, Yingying; Li, Guanshu; Wang, Guowei; Fang, Dawei; Song, Youtao; Wang, Jun

    2017-03-01

    Er(3+):Y3Al5O12/WO3-KNbO3 composite powder as an effective sonocatalyst was prepared via collosol-gelling-hydrothermal and high-temperature calcination methods. The textures of materials were observed by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). In order to estimate the sonocatalytic activity of Er(3+):Y3Al5O12/WO3-KNbO3 composite powder, the sonocatalytic degradation of methamphetamine (MAPA) was performed. Furthermore, the influences of mass ratio of WO3 and KNbO3, ultrasonic irradiation time, catalyst addition amount, initial methamphetamine (MAPA) concentration and used times on the sonocatalytic degradation of methamphetamine (MAPA) caused by Er(3+):Y3Al5O12/WO3-KNbO3 composite powder were investigated by using gas chromatography. Under optimal conditions of 1.00g/L Er(3+):Y3Al5O12/WO3-KNbO3 addition amount and 10.00mg/L methamphetamine (MAPA) initial concentration, 68% of methamphetamine (MAPA) could be removed after 150min ultrasonic irradiation. The experimental results showed that the Er(3+):Y3Al5O12/WO3-KNbO3 as sonocatalyst displayed an excellent sonocatalytic activity in degradation of methamphetamine (MAPA) under ultrasonic irradiation.

  15. Highly Efficient Electronic Sensitization of Non-oxidized Graphene Flakes on Controlled Pore-loaded WO3 Nanofibers for Selective Detection of H2S Molecules

    NASA Astrophysics Data System (ADS)

    Choi, Seon–Jin; Choi, Chanyong; Kim, Sang-Joon; Cho, Hee-Jin; Hakim, Meggie; Jeon, Seokwoo; Kim, Il–Doo

    2015-01-01

    Tailoring of semiconducting metal oxide nanostructures, which possess controlled pore size and concentration, is of great value to accurately detect various volatile organic compounds in exhaled breath, which act as potential biomarkers for many health conditions. In this work, we have developed a very simple and robust route for controlling both the size and distribution of spherical pores in electrospun WO3 nanofibers (NFs) via a sacrificial templating route using polystyrene colloids with different diameters (200 nm and 500 nm). A tentacle-like structure with randomly distributed pores on the surface of electrospun WO3 NFs were achieved, which exhibited improved surface area as well as porosity. Porous WO3 NFs with enhanced surface area exhibited high gas response (Rair/Rgas = 43.1 at 5 ppm) towards small and light H2S molecules. In contrast, porous WO3 NFs with maximized pore diameter showed a high response (Rair/Rgas = 2.8 at 5 ppm) towards large and heavy acetone molecules. Further enhanced sensing performance (Rair/Rgas = 65.6 at 5 ppm H2S) was achieved by functionalizing porous WO3 NFs with 0.1 wt% non-oxidized graphene (NOGR) flakes by forming a Schottky barrier (ΔΦ = 0.11) at the junction between the WO3 NFs (Φ = 4.56 eV) and NOGR flakes (Φ = 4.67 eV), which showed high potential for the diagnosis of halitosis.

  16. HT-solution growth and characterisation of InxNaxMn1-2xWO4 (0

    NASA Astrophysics Data System (ADS)

    Gattermann, U.; Park, S.-H.; Paulmann, C.; Benka, G.; Pfleiderer, C.

    2016-12-01

    A new solid solution system, InxNaxMn1-2xWO4 (0WO4-type multiferroics was investigated. Large single crystals were grown up to several mm in length from high-temperature oxide solutions using a solvent mixture of Na2WO4 and Na2W2O7. Quantitative doping degrees were analyzed by means of electron microprobe. Single crystal X-ray diffraction studies agreed with the polar space group P2 for InxNaxMn1-2xWO4. The complexity of partial (Na+/Mn2+)- and (In3+/Mn2+)-ordering makes their atomic sites unique, explaining the dissymmetrization from P2/c down to P2. This is also valid for the InNaW2O8-type Mn2yIn1-yNa1-yW2O8 solid solution found as co-product in this study. Specific heat and magnetisation measurements showed a paramagnetic dilution effect from (In3+/Na+)-doping while lowering the transition temperature for the multiferroic phase AF2 of InxNaxMn1-2xWO4 with respect to the prototype MnWO4.

  17. Study of two tungstates Ca0.5 Cd0.5 WO4 and Ca0.2 Cd0.8 WO4 by transmission electron microscopy.

    PubMed

    Taoufyq, A; Patout, L; Guinneton, F; Benlhachemi, A; Bakiz, B; Villain, S; Lyoussi, A; Nolibe, G; Gavarri, J-R

    2015-01-01

    To better understand the role of crystal structures and local disorder in the photonic properties of the system (1 - x)CaWO4  - xCdWO4 with 0 < x < 1, two specific phases with compositions x = 0.5 (scheelite phase) and 0.8 (wolframite phase) have been studied by scanning and transmission electron microscopies. High-resolution electron microscopy images and image simulations, associated with X-ray diffraction data, allowed confirming the lattices and space groups I41 /a and P2/c of the two scheelite and wolframite phases, at the local scale. The electron microscopy data show the existence of a high degree of crystallization associated with statistical distribution of Ca or Cd atoms on a Ca1- x Cdx site in each lattice.

  18. Growth of PbWO{sub 4}:MeF{sub 2}(MeF{sub 2} = PbF{sub 2}, BaF{sub 2}) single crystals and their properties

    SciTech Connect

    Baumer, V. N.; Gorobets, Yu. N.; Zelenskaya, O. V.; Kosmyna, M. B.; Nazarenko, B. P.; Puzikov, V. M.; Shekhovtsov, A. N.

    2008-12-15

    PbF{sub 2}-and BaF{sub 2}-doped PbWO{sub 4} crystals have been grown by the Czochralski method. The scintillation characteristics of the grown crystals have been determined. It is shown that introduction of BaF{sub 2} leads to an increase in the light yield of PbWO{sub 4} crystals by 20%, while PbWO{sub 4}:PbF{sub 2} crystals demonstrate a significant increase in radiation hardness.

  19. Growth and optical properties of ZnWO4 single crystals pure and doped with Ca and Eu

    NASA Astrophysics Data System (ADS)

    Kowalski, Z.; Kaczmarek, S. M.; Berkowski, M.; Głowacki, M.; Zhydachevskii, Y. A.; Suchocki, A.

    2017-01-01

    In frames of this work a series of ZnWO4 single crystals, pure and doped with either Ca (5 at%) or Ca (4 at%) and Eu (1 at%), has been grown by the Czochralski method. Phase analysis and structural refinement was performed X-ray powder diffraction and the powder diffraction and the patterns were analyzed by the Rietveld refinement method to analyze the lattice parameters of the crystal structure. Additionally, the absorbance, photoluminescence emission (PL) and photoluminescence excitation (PLE) and EPR spectra were measured and compared to investigate influence of Ca and Eu co-doping on optical properties of the obtained crystals. Furthermore the optical band-gap of the crystals has been calculated. The crystal structure of all mentioned ZnWO4 samples has also discussed in the scope of environment symmetry and possible sites of dopant ions.

  20. Nanochemistry-derived Bi2WO6 nanostructures: towards production of sustainable chemicals and fuels induced by visible light.

    PubMed

    Zhang, Nan; Ciriminna, Rosaria; Pagliaro, Mario; Xu, Yi-Jun

    2014-08-07

    Low cost and easily made bismuth tungstate (Bi2WO6) could be one of the key technologies to make chemicals and fuels from biomass, atmospheric carbon dioxide and water at low cost using solar radiation as an energy source. Its narrow band gap (2.8 eV) enables ideal visible light (λ > 400 nm) absorption. Yet, it is the material's shape, namely the superstructure morphology wisely created via a nanochemistry approach, which leads to better electron-hole separation and much higher photoactivity. Recent results coupled to the versatile photochemistry of this readily available semiconductor suggest that the practical application of nanochemistry-derived Bi2WO6 nanostructures for the synthesis of value-added fine chemicals and fuel production is possible. We describe progress in this important field of chemical research from a nanochemistry viewpoint, and identify opportunities for further progress.

  1. Transport of digoxin-loaded polymeric nanoparticles across BeWo cells, an in vitro model of human placental trophoblast

    PubMed Central

    Albekairi, Norah A; Al-Enazy, Sanaalarab; Ali, Shariq; Rytting, Erik

    2015-01-01

    Background: Fetal arrhythmias can lead to fetal congestive heart failure and hydrops fetalis. Digoxin (the first-line treatment) has low transplacental permeability and high risk of maternal side effects. Biodegradable digoxin-loaded PEGylated poly(lactic-co-glycolic acid) nanoparticles may increase digoxin transport across BeWo b30 cell monolayers (an in vitro model of trophoblast in human placenta) by reducing the drug's interaction with P-gp. Results/methodology: The nanoparticles showed high encapsulation efficiency and sustained release over 48 h. Transport studies revealed significantly increased permeability across BeWo cell layers of digoxin-loaded nanoparticles when compared with free digoxin. P-gp inhibition also increased the permeability of digoxin, but not digoxin-loaded nanoparticles. Conclusion: This represents a novel treatment strategy for fetal cardiovascular disease which may improve maternal and fetal outcomes. PMID:26652279

  2. Mechanisms behind blue, green, and red photoluminescence emissions in CaWO4 and CaMoO4 powders

    NASA Astrophysics Data System (ADS)

    Campos, A. B.; Simões, A. Z.; Longo, E.; Varela, J. A.; Longo, V. M.; de Figueiredo, A. T.; De Vicente, F. S.; Hernandes, A. C.

    2007-07-01

    A combined experimental and theoretical study was conducted to analyze the photoluminescence (PL) properties of ordered and disordered CaWO4 (CW) and CaMoO4 (CM) powders. Two mechanisms were found to be responsible for photoluminescence emission in CW and CM powders. The first one, in the disordered powders, was caused by oxygen complex vacancies [MO3•VOx], [MO3•VO•] and [MO3•VO••], where M =W or Mo, which leads to additional levels in the band gap. The second mechanism, in ordered powders, was caused by an intrinsic slight distortion of the [WO4] or [MoO4] tetrahedral in the short range.

  3. Synthesis of nanovoid Bi(2)WO(6) 2D ordered arrays as photoanodes for photoelectrochemical water splitting.

    PubMed

    Zhang, Liwu; Bahnemann, Detlef

    2013-02-01

    Herein we report a facile and economic method to prepare nanovoid Bi(2)WO(6) 2D ordered arrays employing a simple self-assembly procedure. The electrochemical properties and performance of the 2D nanoarray as a photoanode for water splitting are investigated and compared with a conventional photoanode of similar thickness. The 2D array photoanode shows a much higher photocurrent density and photon-to-H(2) conversion efficiency even with a small content of the Bi(2)WO(6) material. The enhancement is further studied and explained on the basis of the superiority of light scattering and photogenerated hole diffusion within the 2D array structure. This work provides a facile method to improve the efficiency of solar energy conversion systems by minimizing the charge-carrier diffusion length and reducing the light reflection, as well as reducing the amount of the semiconductor material (often costly and/or rare) present in the photoanode.

  4. Photocatalytic activity of the modified composite photocatalyst by introducing the rich-nitrogen complex to the Bi2WO6

    NASA Astrophysics Data System (ADS)

    Wang, Zhi-Nan; Bai, Feng-Ying; Wang, Xuan; Shang, Di; Xing, Yong-Heng

    2016-06-01

    A metal-organic complex [Cd2(L)(N3)4]·DMF was prepared by the reaction of Cd(NO3)2·4H2O, NaN3 and ligand L (L: 1,4-bis(bis(3,5-dimethyl-1H-pyrazol-1-yl)methyl)benzene) in a DMF system. And the complex was characterized by elemental analysis, IR spectroscopy, UV-vis spectroscopy, thermal gravimetric technology, X-ray powder diffraction and single-crystal X-ray diffraction. Furthermore, the complex was combined with Bi2WO6 to form a composite, which was used as photocatalyst to degrade the basic dye methylene blue (MB) under the Xe lamp irradiation. The result revealed that the photocatalytic activity of the composite was better than that of the pure Bi2WO6 and the complex. In addition, the mechanism of the photocatalysis was also studied.

  5. Photocatalytic activity of the modified composite photocatalyst by introducing the rich-nitrogen complex to the Bi2WO6.

    PubMed

    Wang, Zhi-Nan; Bai, Feng-Ying; Wang, Xuan; Shang, Di; Xing, Yong-Heng

    2016-06-15

    A metal-organic complex [Cd2(L)(N3)4]·DMF was prepared by the reaction of Cd(NO3)2·4H2O, NaN3 and ligand L (L: 1,4-bis(bis(3,5-dimethyl-1H-pyrazol-1-yl)methyl)benzene) in a DMF system. And the complex was characterized by elemental analysis, IR spectroscopy, UV-vis spectroscopy, thermal gravimetric technology, X-ray powder diffraction and single-crystal X-ray diffraction. Furthermore, the complex was combined with Bi2WO6 to form a composite, which was used as photocatalyst to degrade the basic dye methylene blue (MB) under the Xe lamp irradiation. The result revealed that the photocatalytic activity of the composite was better than that of the pure Bi2WO6 and the complex. In addition, the mechanism of the photocatalysis was also studied.

  6. Effects of Nickel Doping on the Multiferroic and Magnetic Phases of MnWO 4

    SciTech Connect

    Poudel, N.; Lorenz, B.; Lv, B.; Wang, Y. Q.; Ye, F.; Wang, Jinchen; Fernandez-baca, J. A.; Chu, C. W.

    2015-12-15

    There are various orders in multiferroic materials with a frustrated spiral spin modulation inducing a ferroelectric state are extremely sensitive to small perturbations such as magnetic and electric fields, external pressure, or chemical substitutions. A classical multiferroic, the mineral Hubnerite with chemical formula MnWO4, shows three different magnetic phases at low temperature. The intermediate phase between 7.5K < T < 12.7K is multiferroic and ferroelectricity is induced by an inversion symmetry breaking spiral Mn-spin order and strong spin-lattice interactions. Furthermore, the substitution of Ni2+ (spin 1) for Mn2+ (spin 5/2) in MnWO4 and its effects on the magnetic and multiferroic phases are studied. The ferroelectric phase is stabilized for low Ni content (up to 10%). Upon further Ni doping, the polarization in the ferroelectric phase is quickly suppressed while a collinear and commensurate magnetic phase, characteristic of the magnetic structure in NiWO4, appears first at higher temperature, gradually extends to lower temperature, and becomes the ground state above 30% doping. Between 10% and 30%, the multiferroic phase coexists with the collinear commensurate phase. In this concentration region, the spin spiral plane is close to the a-b plane which explains the drop of the ferroelectric polarization. Finally, the phase diagram of Mn1-xNixWO4 is derived by a combination of magnetic susceptibility, specific heat, electric polarization, and neutron scattering measurements.

  7. Effect of Sensors on the Reliability and Control Performance of Power Circuits in the Web of Things (WoT).

    PubMed

    Bae, Sungwoo; Kim, Myungchin

    2016-09-06

    In order to realize a true WoT environment, a reliable power circuit is required to ensure interconnections among a range of WoT devices. This paper presents research on sensors and their effects on the reliability and response characteristics of power circuits in WoT devices. The presented research can be used in various power circuit applications, such as energy harvesting interfaces, photovoltaic systems, and battery management systems for the WoT devices. As power circuits rely on the feedback from voltage/current sensors, the system performance is likely to be affected by the sensor failure rates, sensor dynamic characteristics, and their interface circuits. This study investigated how the operational availability of the power circuits is affected by the sensor failure rates by performing a quantitative reliability analysis. In the analysis process, this paper also includes the effects of various reconstruction and estimation techniques used in power processing circuits (e.g., energy harvesting circuits and photovoltaic systems). This paper also reports how the transient control performance of power circuits is affected by sensor interface circuits. With the frequency domain stability analysis and circuit simulation, it was verified that the interface circuit dynamics may affect the transient response characteristics of power circuits. The verification results in this paper showed that the reliability and control performance of the power circuits can be affected by the sensor types, fault tolerant approaches against sensor failures, and the response characteristics of the sensor interfaces. The analysis results were also verified by experiments using a power circuit prototype.

  8. Effect of Sensors on the Reliability and Control Performance of Power Circuits in the Web of Things (WoT)

    PubMed Central

    Bae, Sungwoo; Kim, Myungchin

    2016-01-01

    In order to realize a true WoT environment, a reliable power circuit is required to ensure interconnections among a range of WoT devices. This paper presents research on sensors and their effects on the reliability and response characteristics of power circuits in WoT devices. The presented research can be used in various power circuit applications, such as energy harvesting interfaces, photovoltaic systems, and battery management systems for the WoT devices. As power circuits rely on the feedback from voltage/current sensors, the system performance is likely to be affected by the sensor failure rates, sensor dynamic characteristics, and their interface circuits. This study investigated how the operational availability of the power circuits is affected by the sensor failure rates by performing a quantitative reliability analysis. In the analysis process, this paper also includes the effects of various reconstruction and estimation techniques used in power processing circuits (e.g., energy harvesting circuits and photovoltaic systems). This paper also reports how the transient control performance of power circuits is affected by sensor interface circuits. With the frequency domain stability analysis and circuit simulation, it was verified that the interface circuit dynamics may affect the transient response characteristics of power circuits. The verification results in this paper showed that the reliability and control performance of the power circuits can be affected by the sensor types, fault tolerant approaches against sensor failures, and the response characteristics of the sensor interfaces. The analysis results were also verified by experiments using a power circuit prototype. PMID:27608020

  9. Mesoporous film of WO3-the "sunlight" assisted decomposition of surfactant in wastewater for voltammetric determination of Pb

    NASA Astrophysics Data System (ADS)

    Krasnodębska-Ostręga, Beata; Bielecka, Agnieszka; Biaduń, Ewa; Miecznikowski, Krzysztof

    2016-12-01

    In this paper we present the application of "sunlight" assisted digestion in the presence of WO3 to the decomposition of dissolved organic matter, using the anionic surfactant sodium dodecyl sulfate (SDS) and the nonionic surfactant (1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol (Triton™X-114) in natural water samples, prior to the determination of traces residues of lead by stripping voltammetry methods. The results of the study showed firstly that the preparation of reproducible WO3 layers characterized by high mechanical and chemical resistance was possible, and secondly that it was also possible to obtain a high efficiency of decomposition, equal in efficiency to that of the reference method, which was the hydrogen peroxide oxidation assisted by UV, with evaporation nearly to dryness. The developed procedure is suggested to be a no-reagents method for the decomposition of added SDS, leading to 100% recovery of added Pb (II). The anodic stripping voltammetric curves recorded in solution after 4 h irradiation with UV assisted by WO3 were repeatable and increased linearly with standard additions, but the data finally obtained were incorrect. The curves recorded in solution after "sunlight" assisted digestion in the presence of WO3 were repeatable, and increased linearly with an increasing of concentration of standard additions (100% recovery of Pb). In the case of a nonionic surfactant, the decomposition time is at least 6 h. The advantage of the proposed method is the fact that the digestion process does not need the addition of any chemicals for the complete decomposition of organic matter.

  10. Two stacked tandem white organic light-emitting diodes employing WO3 as a charge generation layer

    NASA Astrophysics Data System (ADS)

    Bin, Jong-Kwan; Lee, Na Yeon; Lee, SeungJae; Seo, Bomin; Yang, JoongHwan; Kim, Jinook; Yoon, Soo Young; Kang, InByeong

    2016-09-01

    Recently, many studies have been conducted to improve the electroluminescence (EL) performance of organic lightemitting diodes (OLEDs) by using appropriate organic or inorganic materials as charge generation layer (CGL) for their application such as full color displays, backlight units, and general lighting source. In a stacked tandem white organic light-emitting diodes (WOLEDs), a few emitting units are electrically interconnected by a CGL, which plays the role of generating charge carriers, and then facilitate the injection of it into adjacent emitting units. In the present study, twostacked WOLEDs were fabricated by using tungsten oxide (WO3) as inorganic charge generation layer and 1,4,5,8,9,11- hexaazatriphenylene hexacarbonitrile (HAT-CN) as organic charge generation layer (P-CGL). Organic P-CGL materials were used due to their ease of use in OLED fabrication as compared to their inorganic counterparts. To obtain high efficiency, we demonstrate two-stacked tandem WOLEDs as follows: ITO/HIL/HTL/HTL'/B-EML/ETL/N-CGL/P-CGL (WO3 or HAT-CN)/HTL″/YG-EML/ETL/LiF/Al. The tandem devices with blue- and yellow-green emitting layers were sensitive to the thickness of an adjacent layer, hole transporting layer for the YG emitting layer. The WOLEDs containing the WO3 as charge generation layer reach a higher power efficiency of 19.1 lm/W and the current efficiency of 51.2 cd/A with the white color coordinate of (0.316, 0.318) than the power efficiency of 13.9 lm/W, and the current efficiency of 43.7 cd/A for organic CGL, HAT-CN at 10 mA/cm2, respectively. This performance with inserting WO3 as CGL exhibited the highest performance with excellent CIE color coordinates in the two-stacked tandem OLEDs.

  11. Microwave-assisted synthesis and characterization of SrMoO4 and SrWO4 nanocrystals

    NASA Astrophysics Data System (ADS)

    Thongtem, Titipun; Phuruangrat, Anukorn; Thongtem, Somchai

    2010-08-01

    SrMoO4 and SrWO4 nanocrystals have been synthesized using Sr(NO3)2 and Na2MeO4 (Me = Mo and W) in ethylene glycol by a microwave irradiation method at 50% of 180 W for 20 min. The product phases were detected using X-ray and selected area electron diffractions. They show the body-centered primitive tetragonal structure with the lattice parameters of a = b = 5.4007 Å and c = 12.0330 Å for SrMoO4, and a = b = 5.4274 Å and c = 11.9241 Å for SrWO4. X-ray diffraction patterns of the products, obtained by simulation using CaRIne version 3.1 program, are in accordance with those of the corresponding experiment and International Centre for Diffraction Data. A transmission electron microscope revealed the presence of nanocrystals composing the products, with their sizes in the ranges of 14-40 and 14-38 nm for SrMoO4 and SrWO4, respectively. Six different vibrations of ν 1( A g), ν 3( B g), ν 3( E g), ν 4( B g), ν 2( A g), and ν f.r.( A g) were detected using a Raman spectrometer, and the ν 3( F 2) antisymmetric stretching and ν 4( F 2) bending modes of [MeO4]2- tetrahedrons using a Fourier transform infrared spectrometer. Photoluminescence emissions of SrMoO4 and SrWO4, caused by the 1 T 2 → 1 A 1 transition of electrons, were detected at 410 and 418 nm, respectively.

  12. Advancing multifocal nonlinear microscopy: development and application of a novel multibeam Yb:KGd(WO4)2 oscillator.

    PubMed

    Sheetz, Kraig E; Hoover, Erich E; Carriles, Ramón; Kleinfeld, David; Squier, Jeff A

    2008-10-27

    We present a novel Yb:KGd(WO(4))(2) oscillator design that generates six beams of temporally delayed, 253 fs, 11 nJ pulses. This allows multifocal nonlinear microscopy to be performed without the need for complicated optical multiplexers. We demonstrate our design with twelve simultaneously acquired two-photon, second-harmonic and/or third-harmonic images generated from six laterally separated foci.

  13. Ni-catalysed WO3 nanostructures grown by electron beam rapid thermal annealing for NO2 gas sensing

    NASA Astrophysics Data System (ADS)

    Chandrasekaran, Gopalakrishnan; Sundararaj, Anuraj; Therese, Helen Annal; Jeganathan, K.

    2015-07-01

    Ni-catalysed WO3 (Ni-WO3) nanowires and nanosheets were grown on Si (100) substrates using electron beam evaporation followed by electron beam-assisted rapid thermal annealing process. Gas-sensing measurements were performed for various concentrations of NO2 in dry air at a temperature range of 50-400 °C. Nanowires and nanosheets show optimum sensor response of 229 and 197 at operating temperatures of 200 and 250 °C, respectively, for 100 ppm of NO2 exposure. Nanowires demonstrated a rapid response time of 66 s, but a slow recovery time of 204 s owing to poor rate of desorption of the adsorbed NO2 gas molecules from the internal porous structure of nanowires. In contrast, the recovery time for nanosheet was 126 s due to higher desorption rate of the adhered NO2 molecules associated with low surface area and less porous structure of nanosheet. The gas-sensing mechanism of WO3 nanostructure is discussed briefly.

  14. Nano-Bi2WO6 functionalized flexible SiO2 fibrous film for water purification

    NASA Astrophysics Data System (ADS)

    Ma, Zhijun; Hu, Zhongliang; He, Xin; Fang, Zaijin; Li, Yang; Qiu, Jianrong

    2016-01-01

    Electrospinning-derived nanofibrous films functionalized by photocatalysts have been extensively studied in the applications of environmental remediation. In this investigation, we propose a simple strategy for preparation of flexible and chemically stable nanofibrous films with high photocatalytic efficiency. Specifically, SiO2 nanofibrous film modified with Bi2WO6 nanoparticles was studied as a representative. Flexible SiO2 nanofibers were derived through sol-gel and electrospinning techniques. By simple soaking in precursor solution of Bi2WO6 and calcination, the SiO2 nanofibrous film was functionalized by Bi2WO6 nanoparticles, forming hierarchically porous composite film. Micro morphology, mechanical property and photocatalytic performance were tuned via changing the concentration of the soaking solution. Photocatalytic removal of organic pollutant from water was performed using RhB (Rhodamine B) as a model. The strategy proposed here is also widely applicable for preparation of composite films modified with other kinds of photocatalysts. SiO2-Bi2MoO6, SiO2-TiO2 and SiO2-CuO composite films were prepared in a similar way to demonstrate the versatility of the proposed preparation strategy.

  15. Synthesis and photocatalytic activity of WO(3) nanoparticles prepared by the arc discharge method in deionized water.

    PubMed

    Ashkarran, A A; Iraji Zad, A; Ahadian, M M; Mahdavi Ardakani, S A

    2008-05-14

    In this paper, we discuss the synthesis and characterization of tungsten trioxide nanoparticles prepared by the arc discharge method in deionized (DI) water. The size and morphology of WO(3) nanoparticles prepared using different arc currents (25, 35 and 45 A) were studied. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) results indicate that at an arc current of 25 A, the size of the particles is about 30 nm, and this increases to 64 nm by increasing the arc current. This size increase caused a decrease of optical band gap from 2.9 to 2.6 eV. X-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) spectra demonstrate the formation of the WO(3) phase. Photodegradation of Rhodamine B shows that samples prepared at the lowest current have more photocatalytic activity due to having the smallest particle size and highest surface area. The results demonstrate the ability of the arc discharge method for direct formation of WO(3) nanoparticles in DI water medium.

  16. Effects of ytterbium on electrical and optical properties of BCP/Ag/WO3 transparent electrode based organic photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Oh, Il Soo; Ji, Chan Hyuk; Oh, Se Young

    2016-01-01

    This study introduces dielectric/metal/dielectric multilayers based on a WO3/Ag/WO3 (WAW) anode and Yb/BCP/Ag/WO3 (Yb/BAW) cathode for use in organic photovoltaic cells (OPVs). Here, the Yb/BCP hybrid multilayer provides an effective electron transport layer (ETL), while the Yb doping ensures that voltage loss due to interfacial band bending is effectively suppressed. Transparent OPVs produced with a structure of WAW/P3HT:PCBM/Yb/BAW are shown to exhibit a power conversion efficiency (PCE) of up to 2.42%, achieving a 65.4% fill factor (FF) under one sun irradiation. These results indicate that the use of Yb in transparent OPVs is vastly superior to other ETLs, as it improves the majority of critical parameters such as short circuit current (Jsc), fill factor (FF) and PCE. This is attributed to a decrease in the series resistance and increase in the shunt resistance, while an increase in electron mobility also helps to ensure faster sweep out. [Figure not available: see fulltext.

  17. Fabrication and morphology control of BaWO{sub 4} thin films by microwave assisted chemical bath deposition

    SciTech Connect

    Wang Rui; Liu Chen; Zeng Jia; Li KunWei; Wang Hao

    2009-04-15

    Highly crystallized barium tungstate (BaWO{sub 4}) thin films with dumbbell-like, kernel-like, bowknot-like and cauliflower-like microstructure were synthesized from an aqueous solution containing barium nitrate, ethylenediamine tetraacetate acid disodium and sodium tungstate, via mild microwave assisted chemical bath deposition process. The resulting BaWO{sub 4} films with different morphologies were characterized by X-ray diffraction spectrum, scanning electron microscope, Raman and photoluminescence spectra. The results indicate that the morphologies of final products significantly depend on the reaction conditions including the reaction time, the initial concentration of precursor reagent and the physicochemical characteristics of the substrates. Furthermore, the oriented aggregation mechanism is proposed as a possible formation mechanism of the films with specific morphologies. - Graphical abstract: Highly crystallized BaWO{sub 4} thin films with controllable morphologies have been synthesized via mild microwave assisted chemical bath deposition. The oriented aggregation mechanism has been proposed as the possible formation mechanism of specific films.

  18. Tuning oxygen vacancy photoluminescence in monoclinic Y2WO6 by selectively occupying yttrium sites using lanthanum

    PubMed Central

    Ding, Bangfu; Han, Chao; Zheng, Lirong; Zhang, Junying; Wang, Rongming; Tang, Zilong

    2015-01-01

    The effect of isovalent lanthanum (La) doping on the monoclinic Y2WO6 photoluminescence was studied. Introducing the non-activated La3+ into Y2WO6 brings new excitation bands from violet to visible regions and strong near-infrared emission, while the bands position and intensity depend on the doping concentration. It is interesting to find that doping La3+ into Y2WO6 promotes the oxygen vacancy formation according to the first-principle calculation, Raman spectrum, and synchrotron radiation analysis. Through the Rietveld refinement and X-ray photoelectron spectroscopy results, La3+ is found to mainly occupy the Y2 (2f) site in low-concentration doped samples. With increasing doping concentration, the La3+ occupation number at the Y3 (4g) site increases faster than those at the Y1 (2e) and Y2 (2f) sites. When La3+ occupies different Y sites, the localized energy states caused by the oxygen vacancy pair change their position in the forbidden band, inducing the variation of the excitation and emission bands. This research proposes a feasible method to tune the oxygen vacancy emission, eliminating the challenge of precisely controlling the calcination atmosphere. PMID:25821078

  19. Web-of-Objects (WoO)-Based Context Aware Emergency Fire Management Systems for the Internet of Things

    PubMed Central

    Shamszaman, Zia Ush; Ara, Safina Showkat; Chong, Ilyoung; Jeong, Youn Kwae

    2014-01-01

    Recent advancements in the Internet of Things (IoT) and the Web of Things (WoT) accompany a smart life where real world objects, including sensing devices, are interconnected with each other. The Web representation of smart objects empowers innovative applications and services for various domains. To accelerate this approach, Web of Objects (WoO) focuses on the implementation aspects of bringing the assorted real world objects to the Web applications. In this paper; we propose an emergency fire management system in the WoO infrastructure. Consequently, we integrate the formation and management of Virtual Objects (ViO) which are derived from real world physical objects and are virtually connected with each other into the semantic ontology model. The charm of using the semantic ontology is that it allows information reusability, extensibility and interoperability, which enable ViOs to uphold orchestration, federation, collaboration and harmonization. Our system is context aware, as it receives contextual environmental information from distributed sensors and detects emergency situations. To handle a fire emergency, we present a decision support tool for the emergency fire management team. The previous fire incident log is the basis of the decision support system. A log repository collects all the emergency fire incident logs from ViOs and stores them in a repository. PMID:24531299

  20. Pressure-induced phase transitions of β-type pyrochlore CsTaWO6

    SciTech Connect

    Zhang, F. X.; Tracy, C. L.; Shamblin, J.; Palomares, R. I.; Lang, M.; Park, S.; Park, C.; Tkachev, S.; Ewing, R. C.

    2016-09-30

    The β-type pyrochlore CsTaWO6 was studied by synchrotron X-ray diffraction (XRD) and Raman scattering methods up to pressures of 43 GPa using a diamond anvil cell (DAC). With increasing pressure, the cubic pyrochlore in space group of Fd-3¯m with combining macron]m transforms to an orthorhombic structure (space group: Pnma) at 5.9 GPa and then to a monoclinic structure (space group: P21/c) at ~18 GPa. The structural evolution in CsTaWO6 is a continuous process and experimental results suggest that the initial cubic phase has a tetragonal distortion at ambient conditions. Both XRD and Raman measurements indicate that the pressure-induced phase transitions in CsTaWO6 are reversible. Lastly, these results may provide a structural explanation of previous experimental resistivity measurement results for the isostructural superconductor K(Cs)Os2O6 at high pressure conditions.

  1. Radiopurity of CaWO{sub 4} crystals for direct dark matter search with CRESST and EURECA

    SciTech Connect

    Münster, A.; Sivers, M. v.; Erb, A.; Feilitzsch, F. v.; Gütlein, A.; Lanfranchi, J.-C.; Potzel, W.; Angloher, G.; Bento, A.; Hauff, D.; Petricca, F.; Pröbst, F.; Bucci, C.; Canonica, L.; Gorla, P.; Laubenstein, M.; Jochum, J.; Loebell, J.; Kraus, H.; Ortigoza, Y. E-mail: msivers@ph.tum.de; and others

    2014-05-01

    The direct dark matter search experiment CRESST uses scintillating CaWO{sub 4} single crystals as targets for possible WIMP scatterings. An intrinsic radioactive contamination of the crystals as low as possible is crucial for the sensitivity of the detectors. In the past CaWO{sub 4} crystals operated in CRESST were produced by institutes in Russia and the Ukraine. Since 2011 CaWO{sub 4} crystals have also been grown at the crystal laboratory of the Technische Universität München (TUM) to better meet the requirements of CRESST and of the future tonne-scale multi-material experiment EURECA. The radiopurity of the raw materials and of first TUM-grown crystals was measured by ultra-low background γ-spectrometry. Two TUM-grown crystals were also operated as low-temperature detectors at a test setup in the Gran Sasso underground laboratory. These measurements were used to determine the crystals' intrinsic α-activities which were compared to those of crystals produced at other institutes. The total α-activities of TUM-grown crystals as low as 1.23±0.06 mBq/kg were found to be significantly smaller than the activities of crystals grown at other institutes typically ranging between ∼ 15 mBq/kg and ∼ 35 mBq/kg.

  2. Hydrangeas-like Bi2WO6: facile synthesis, visible-light driven photocatalysis and theoretical analysis.

    PubMed

    Gao, Hongtao; Liu, Fangfang; Li, Xiaohui; Li, Fenfen; Sui, Xiaomei

    2012-08-01

    Hydrangeas-like Bi2WO6 powders were synthesized successfully by salt-ultrasonic assisted hydrothermal process, which were characterized by scanning electron microscopy (SEM), Energy dispersive X-ray (EDS), X-ray diffraction (XRD), and UV-visible diffuse reflectance spectra (UV-Vis DRS), respectively. Bi, W and O elements were contained in the product, which could be tested by EDS. The crystal structure of the catalyst was orthorhombic phase (JCPDS card no.73-1126). And the band gap was estimated to be 2.56 eV from the onset of UV-Vis absorption spectra of the catalyst. In addition, the photocatalytic activities of the products were investigated on the degradation of Rhodamine B (RhB). It demonstrated that photocatalysts exhibited excellent visible-light driven photocatalytic performance. And the target residue was less than 1% in 20 min under Xenon lamp irradiation. First-principles calculations based on density functional theory (DFT) were used to explore the electronic and optical properties of Bi2WO6. And the theoretical calculations could illustrate the photocatalytic performance of Bi2WO6 powders under visible light irradiation.

  3. Comparative description of magnetic interactions in Sr2CuTeO6 and Sr2CuWO6

    NASA Astrophysics Data System (ADS)

    Xu, Yuanhui; Liu, Shanshan; Qu, Nianrui; Cui, Yanli; Gao, Qiangqiang; Chen, Rongna; Wang, Jing; Gao, Faming; Hao, Xianfeng

    2017-03-01

    In this work, we comparatively explored the electronic structure and the low-dimensional magnetic interactions of double-perovskite compounds Sr2CuTeO6 and Sr2CuWO6 through first-principles calculations. The electronic structure calculations indicate that the Cu2+ (3d 9) site is the only magnetic active one, whereas Te6+ and W6+ remain in nonmagnetic states with d 10 and d 0 electronic configurations, respectively. The magnetic exchange interactions have been evaluated on the basis of the classical Heisenberg model. Both Sr2CuTeO6 and Sr2CuWO6 should be strong frustrated 2D magnetism, in excellent agreement with the experimental observations. Nevertheless, the nearest-neighbor antiferromagnetic interaction J 1 plays a determined role in constructing the Néel antiferromagnetic ordering within the square Cu2+ framework of Sr2CuTeO6. While, the next-nearest-neighbor antiferromagnetic interaction J 2 transcends the nearest-neighbor interaction J 1, establishes the collinear antiferromagnetic ordering in Sr2CuWO6. The discrimination has been explored and analyzed in detail using density of states, charge density as well as spin density analysis.

  4. Economic Costs of a Postrelease Intervention for Incarcerated Female Substance Abusers: Recovery Management Checkups for Women Offenders (RMC-WO)

    PubMed Central

    McCollister, Kathryn E.; Scott, Christy K.; Dennis, Michael L.; Freitas, Derek M.; French, Michael T.; Funk, Rodney R.

    2015-01-01

    This study estimates the economic costs of Recovery Management Checkups for Women Offenders (RMC-WO), highlighting the unique mix of services and differential costs between two distinct phases of the intervention. Participants were randomly assigned to quarterly outcome monitoring (OM) only (n=242) or OM plus Recovery Management Checkups (OM-plus-RMC) (n=238). The OM-only condition has a total annual economic cost of $76,010, which equates to $81 quarterly per person. The average cost per OM interview completed is $86. OM-plus-RMC generates a total annual economic cost of $126,717, or $137 quarterly per person. The cost per interview completed is $147 and the cost per intervention session completed is $161. RMC-WO has a relatively modest additional cost compared with the average costs of post-release supervision, which can range from $3.42 ($1,250) per day (year) for probationers to $7.47 ($2,750) per day (year) for parolees. The clinical, economic, and policy implications of incorporating RMC-WO into existing corrections and/or community-based treatment settings are discussed. PMID:27030790

  5. Influence of Doping and Excitation Powers on Optical Thermometry in Yb3+-Er3+ doped CaWO4

    NASA Astrophysics Data System (ADS)

    Wang, Xiangfu; Wang, Yemin; Bu, Yanyan; Yan, Xiaohong; Wang, Jing; Cai, Peiqing; Vu, Thiquynh; Seo, Hyo Jin

    2017-02-01

    Optical thermometry has been widely studied to achieve an inaccessible temperature measurement in submicron scale and it has been reported that the temperature sensitivity depends mainly on host types. In this work, we propose a new method to improve the optical temperature sensitivity of Yb3+-Er3+ co-doped CaWO4 phosphors by doping with Li+, Sr2+, and Mg2+ ions and by controlling excitation powers of 980 nm laser. It is found that the thermometric parameters such as upconversion emission intensity, intensity ratio of green-to-red emission, fluorescence color, emission intensity ratios of thermally coupled levels (2H11/2/4S3/2), and relative and absolute temperature sensitivity can be effectively controlled by doping with Li+, Sr2+, and Mg2+ ions in the Yb3+-Er3+ co-doped CaWO4 system. Moreover, the relative sensitivity SR and the absolute sensitivity SA are proved to be dependent on the pump power of 980 nm laser. The sensitivities of SR and SA in Yb3+-Er3+ co-doped CaWO4 increase about 31.5% and 12%, respectively, by doping with 1 mol% Sr2+.

  6. Upconversion luminescence of lanthanide-doped mixed CaMoO4-CaWO4 micro-/nano-materials.

    PubMed

    Liu, Jing; Kaczmarek, Anna M; Billet, Jonas; Van Driessche, Isabel; Van Deun, Rik

    2016-08-14

    Uniform mixed CaMoO4-CaWO4 micro-/nano-materials have been successfully synthesised by a facile hydrothermal method. The morphology of these upconversion materials could be changed to different shapes and the size could also be decreased from the micro- to nano-scale by varying the type of surfactant used. It was observed that before heat treatment, the materials show relatively weak green light emission under excitation at 975 nm, whereas after heat treatment, the intensity of the upconversion luminescence increases dramatically while the intensity of the red component decreases relatively. By adjusting the molybdate/tungstate ratio, it was found that the samples with a higher molybdate content have stronger luminescence properties. XRD measurements have been done to investigate the structure of the mixed CaMoO4-CaWO4 upconversion materials. The effect of heat treatment at different temperatures on the emission spectra and XRD patterns has also been studied. TG-DTA was used to further confirm the most suitable temperature for heat treatment. The luminescence lifetimes and CIE coordinates for these samples were also determined. Additionally it was found that Gd(3+) co-doping could further increase the upconversion luminescence from these mixed CaMoO4-CaWO4 materials. Finally, monitoring the upconversion luminescence intensity as a function of laser pump power confirmed the upconversion process to be a two-photon absorption mechanism.

  7. Low-Temperature Ozone Exposure Technique to Modulate the Stoichiometry of WO(x) Nanorods and Optimize the Electrochromic Performance

    SciTech Connect

    Lin, F.; Li, C. P.; Chen, G.; Tenent, R. C.; Wolden, C. A.; Gillaspie, D. T.; Dillon, A. C.; Richards, R. M.; Engtrakul, C.

    2012-06-29

    A low-temperature ozone exposure technique was employed for the post-treatment of WO{sub x} nanorod thin films fabricated from hot-wire chemical vapor deposition (HWCVD) and ultrasonic spray deposition (USD) techniques. The resulting films were characterized with x-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, UV-vis-NIR spectroscopy and x-ray photoelectron spectroscopy (XPS). The stoichiometry and surface crystallinity of the WO{sub x} thin films were subsequently modulated upon ozone exposure and thermal annealing without particle growth. The electrochromic performance was studied in a LiClO{sub 4}-propylene carbonate electrolyte, and the results suggest that the low-temperature ozone exposure technique is superior to the traditional high-temperature thermal annealing (employed to more fully oxidize the WO{sub x}). The optical modulation at 670 nm was improved from 35% for the as-deposited film to 57% for the film after ozone exposure at 150 C. The coloration efficiency was improved and the switching speed to the darkened state was significantly accelerated from 18.0 s for the as-deposited film to 11.8 s for the film after the ozone exposure. The process opens an avenue for low-temperature and cost-effective manufacturing of electrochromic films, especially on flexible polymer substrates.

  8. Hypervariable prophage WO sequences describe an unexpected high number of Wolbachia variants in the mosquito Culex pipiens

    PubMed Central

    Duron, Olivier; Fort, Philippe; Weill, Mylène

    2005-01-01

    Wolbachia are maternally inherited endosymbiotic bacteria that infect many arthropod species and may induce cytoplasmic incompatibility (CI) resulting in abortive embryonic development. Among all the described host species, mosquitoes of the Culex pipiens complex display the highest variability of CI crossing types. Paradoxically, searches for polymorphism in Wolbachia infecting strains and field populations hitherto failed or produced very few markers. Here, we show that an abundant source of the long-sought polymorphism lies in WO prophage sequences present in multiple copies dispersed in the genome of Wolbachia infecting C. pipiens (wPip). We identified up to 66 different Wolbachia variants in C. pipiens strains and field populations and no occurrence of superinfection was observed. At least 49 different Wolbachia occurred in Southern Europe C. pipiens populations, and up to 10 different Wolbachia were even detected in a single population. This is in sharp contrast with North African and Cretan samples, which exhibited only six variants. The WO polymorphism appeared stable over time, and was exclusively transferred maternally. Interestingly, we found that the CI pattern previously described correlates with the variability of Gp15, a prophage protein similar to a bacterial virulence protein. WO prophage sequences thus represent variable markers that now open routes for approaching the molecular basis of CI, the host effects, the structure and dynamics of Wolbachia populations. PMID:16615218

  9. Crystal structure of the 'mixed-layer' Aurivillius phase Bi{sub 5}TiNbWO{sub 15}

    SciTech Connect

    Snedden, Alan; Charkin, Dmitri O.; Dolgikh, Valeriy A.; Lightfoot, Philip . E-mail: pl@st-and.ac.uk

    2005-01-15

    The crystal structure of the Aurivillius phase Bi{sub 5}TiNbWO{sub 15} has been analyzed in detail using powder X-ray and neutron diffraction. The structure can be described as a regular intergrowth of alternating single and double perovskite-like layers sandwiched between fluorite-like bismuth oxide layers, such that the layer sequence is ... [WO{sub 4}]-[Bi{sub 2}O{sub 2}]-[BiTiNbO{sub 7}]-[Bi{sub 2}O{sub 2}] .... There is complete ordering of tungsten within the B sites of the single perovskite layer, so that the structure can be described as a direct intergrowth of the 'component' Aurivillius phases Bi{sub 2}WO{sub 6} and Bi{sub 3}TiNbO{sub 9}. At 25 deg. C the structure adopts the polar orthorhombic space group I2cm, a=5.4231(2)A, b=5.4027(2)A, c=41.744(1)A.

  10. Facile synthesis of PbWO4: applications in photoluminescence and photocatalytic degradation of organic dyes under visible light.

    PubMed

    Saraf, Rohit; Shivakumara, C; Behera, Sukanti; Nagabhushana, H; Dhananjaya, N

    2015-02-05

    Stolzite polymorph of PbWO4 catalyst was prepared by the facile room temperature precipitation method. Structural parameters were refined by the Rietveld analysis using powder X-ray data. PbWO4 was crystallized in the scheelite-type tetragonal structure with space group I41/a (No. 88). Field emission scanning electron microscopy revealed leaf like morphology. Photoluminescence spectra exhibit broad blue emission (425 nm) under the excitation of 356 nm. The photocatalytic degradation of Methylene blue, Rhodamine B and Methyl orange dyes were measured under visible illumination. The 100% dye degradation was observed for MB and RhB dyes within 60 and 105 min. The rate constant was found to be in the decreasing order of MB>RhB>MO which followed the 1st order kinetic mechanism. Therefore, PbWO4 can be a potential candidate for blue component in white LEDs and also acts as a catalyst for the treatment of toxic and non-biodegradable organic pollutants in water.

  11. Facile synthesis of PbWO4: Applications in photoluminescence and photocatalytic degradation of organic dyes under visible light

    NASA Astrophysics Data System (ADS)

    Saraf, Rohit; Shivakumara, C.; Behera, Sukanti; Nagabhushana, H.; Dhananjaya, N.

    2015-02-01

    Stolzite polymorph of PbWO4 catalyst was prepared by the facile room temperature precipitation method. Structural parameters were refined by the Rietveld analysis using powder X-ray data. PbWO4 was crystallized in the scheelite-type tetragonal structure with space group I41/a (No. 88). Field emission scanning electron microscopy revealed leaf like morphology. Photoluminescence spectra exhibit broad blue emission (425 nm) under the excitation of 356 nm. The photocatalytic degradation of Methylene blue, Rhodamine B and Methyl orange dyes were measured under visible illumination. The 100% dye degradation was observed for MB and RhB dyes within 60 and 105 min. The rate constant was found to be in the decreasing order of MB > RhB > MO which followed the 1st order kinetic mechanism. Therefore, PbWO4 can be a potential candidate for blue component in white LEDs and also acts as a catalyst for the treatment of toxic and non-biodegradable organic pollutants in water.

  12. Thermo-optic coefficients and thermal lensing in Nd-doped KGd(WO4)2 laser crystals.

    PubMed

    Loiko, Pavel A; Yumashev, Konstantin V; Kuleshov, Nikolai V; Pavlyuk, Anatoly A

    2010-12-01

    We measured the thermo-optic coefficients dn/dT of anisotropic Nd:KGd(WO(4))(2) crystals at the wavelengths of 1.064 μm and 532 nm (300 K) by a beam deflection method. The values of dn/dT are determined to be dn(p)/dT = -16.0 × 10(-6) K(-1), dn(m)/dT = -11.8 × 10(-6) K(-1), and dn(g)/dT = -19.5 × 10(-6) K(-1) (at 1.064 μm) and dn(p)/dT = -14.3 × 10(-6) K(-1), dn(m)/dT = -10.0 × 10(-6) K(-1), and dn(g)/dT = -15.0 × 10(-6) K(-1) (at 532 nm). Thermal lensing in the flashlamp-pumped N(p)- and N(g)-cut Nd:KGd(WO(4))(2) laser rods was studied at 1.064 μm by a probe beam technique in the nonlasing conditions, and the contribution of the photoelastic term to the thermal lens optical power was estimated. Athermal propagation directions with the definitions dn/dT + (n-1)α(T) = 0 and dn/dT + nα(T) = 0 were found in Nd:KGd(WO(4))(2).

  13. Exclusive reactions and the PbWO4-based Inner Calorimeter for the Electron-Ion Collider

    NASA Astrophysics Data System (ADS)

    Trotta, Richard; Horn, Tanja; Vargas, Andres; Carmignotto, Marco; Ali, Salina; Uniyal, Rishabh

    2017-01-01

    One of the main goals of the Electron-Ion Collider (EIC) is the three-dimensional imaging of nucleon and nuclei and unveiling the role of orbital angular motion of sea quarks and gluons in forming the nucleon spin. These studies are made possible through a new framework developed to explore nucleon structure through the Generalized Parton Distributions (GPDs) and the Transverse Momentum-Dependent parton distributions (TMDs). To carry out the scientific program, a specialized detector is needed. The particle identification requirements are driven by semi-inclusive and exclusive scattering processes like DVCS. For the latter an elimination or reduction of background events is mandatory. This requires good resolution in angle to distinguish between clusters, good energy resolution for measurements of the cluster energy, and the ability to withstand radiation. The small Moliere radius of the PbWO4 crystals makes them an ideal solution for the EIC inner crystal calorimeter. In this talk we will discuss what needs to be done to build a PbWO4-based inner calorimeter, the importance of PbWO4 quality, and results from ongoing crystal characterization efforts.

  14. Band gap states in nanocrystalline WO3 thin films studied by soft x-ray spectroscopy and optical spectrophotometry

    NASA Astrophysics Data System (ADS)

    Johansson, M. B.; Kristiansen, P. T.; Duda, L.; Niklasson, G. A.; Österlund, L.

    2016-11-01

    Nanocrystalline tungsten trioxide (WO3) thin films prepared by DC magnetron sputtering have been studied using soft x-ray spectroscopy and optical spectrophotometry. Resonant inelastic x-ray scattering (RIXS) measurements reveal band gap states in sub-stoichiometric γ-WO3-x with x  =  0.001-0.005. The energy positions of these states are in good agreement with recently reported density functional calculations. The results were compared with optical absorption measurements in the near infrared spectral region. An optical absorption peak at 0.74 eV is assigned to intervalence transfer of polarons between W sites. A less prominent peak at energies between 0.96 and 1.16 eV is assigned to electron excitation of oxygen vacancies. The latter results are supported by RIXS measurements, where an energy loss in this energy range was observed, and this suggests that electron transfer processes involving transitions from oxygen vacancy states can be observed in RIXS. Our results have implications for the interpretation of optical properties of WO3, and the optical transitions close to the band gap, which are important in photocatalytic and photoelectrochemical applications.

  15. Synthesis and characterization of nonsubstituted and substituted proton-conducting La(6-x)WO(12-y).

    PubMed

    Seeger, Janka; Ivanova, Mariya E; Meulenberg, Wilhelm A; Sebold, Doris; Stöver, Detlev; Scherb, Tobias; Schumacher, Gerhard; Escolástico, Sonia; Solís, Cecilia; Serra, José M

    2013-09-16

    Mixed proton-electron conductors (MPEC) can be used as gas separation membranes to extract hydrogen from a gas stream, for example, in a power plant. From the different MPEC, the ceramic material lanthanum tungstate presents an important mixed protonic-electronic conductivity. Lanthanum tungstate La(6-x)WO(12-y) (with y = 1.5x + δ and x = 0.5-0.8) compounds were prepared with La/W ratios between 4.8 and 6.0 and sintered at temperatures between 1300 and 1500 °C in order to study the dependence of the single-phase formation region on the La/W ratio and temperature. Furthermore, compounds substituted in the La or W position were prepared. Ce, Nd, Tb, and Y were used for partial substitution at the La site, while Ir, Re, and Mo were applied for W substitution. All substituents were applied in different concentrations. The electrical conductivity of nonsubstituted La(6-x)WO(12-y) and for all substituted La(6-x)WO(12-y) compounds was measured in the temperature range of 400-900 °C in wet (2.5% H2O) and dry mixtures of 4% H2 in Ar. The greatest improvement in the electrical characteristics was found in the case of 20 mol % substitution with both Re and Mo. After treatment in 100% H2 at 800 °C, the compounds remained unchanged as confirmed with XRD, Raman, and SEM.

  16. Influence of Doping and Excitation Powers on Optical Thermometry in Yb3+-Er3+ doped CaWO4

    PubMed Central

    Wang, Xiangfu; Wang, Yemin; Bu, Yanyan; Yan, Xiaohong; Wang, Jing; Cai, Peiqing; Vu, Thiquynh; Seo, Hyo Jin

    2017-01-01

    Optical thermometry has been widely studied to achieve an inaccessible temperature measurement in submicron scale and it has been reported that the temperature sensitivity depends mainly on host types. In this work, we propose a new method to improve the optical temperature sensitivity of Yb3+-Er3+ co-doped CaWO4 phosphors by doping with Li+, Sr2+, and Mg2+ ions and by controlling excitation powers of 980 nm laser. It is found that the thermometric parameters such as upconversion emission intensity, intensity ratio of green-to-red emission, fluorescence color, emission intensity ratios of thermally coupled levels (2H11/2/4S3/2), and relative and absolute temperature sensitivity can be effectively controlled by doping with Li+, Sr2+, and Mg2+ ions in the Yb3+-Er3+ co-doped CaWO4 system. Moreover, the relative sensitivity SR and the absolute sensitivity SA are proved to be dependent on the pump power of 980 nm laser. The sensitivities of SR and SA in Yb3+-Er3+ co-doped CaWO4 increase about 31.5% and 12%, respectively, by doping with 1 mol% Sr2+. PMID:28240270

  17. Solid-base loaded WO{sub 3} photocatalyst for decomposition of harmful organics under visible light irradiation

    SciTech Connect

    Kako, Tetsuya; Meng, Xianguang; Ye, Jinhua

    2015-10-01

    Composite of NaBiO{sub 3}-loaded WO{sub 3} with a mixing ratio of 10:100 was prepared for photocatalytic harmful-organic-contaminant decomposition. The composite properties were measured using X-ray diffraction, ultraviolet-visible spectrophotometer (UV-Vis), and valence band-X-ray photoelectron spectroscope (VB-XPS). The results exhibited that the potentials for top of the valence band and bottom of conduction band for NaBiO{sub 3} can be estimated, respectively, as +2.5 V and -0.1 to 0 V. Furthermore, WO{sub 3}, NaBiO{sub 3}, and the composite showed IPA oxidation properties under visible-light irradiation. Results show that the composite exhibited much higher photocatalytic activity about 2-propanol (IPA) decomposition into CO{sub 2} than individual WO{sub 3} or NaBiO{sub 3} because of charge separation promotion and the base effect of NaBiO{sub 3}.

  18. Modification of nanocrystalline WO3 with a dicationic perylene bisimide: applications to molecular level solar water splitting.

    PubMed

    Ronconi, Federico; Syrgiannis, Zois; Bonasera, Aurelio; Prato, Maurizio; Argazzi, Roberto; Caramori, Stefano; Cristino, Vito; Bignozzi, Carlo Alberto

    2015-04-15

    [(N,N'-Bis(2-(trimethylammonium)ethylene) perylene 3,4,9,10-tetracarboxylic acid bisimide)(PF6)2] (1) was observed to spontaneously adsorb on nanocrystalline WO3 surfaces via aggregation/hydrophobic forces. Under visible irradiation (λ > 435 nm), the excited state of 1 underwent oxidative quenching by electron injection (kinj > 10(8) s(-1)) to WO3, leaving a strongly positive hole (Eox ≈ 1.7 V vs SCE), which allows to drive demanding photo-oxidation reactions in photoelectrochemical cells (PECs). The casting of IrO2 nanoparticles (NPs), acting as water oxidation catalysts (WOCs) on the sensitized electrodes, led to a 4-fold enhancement in photoanodic current, consistent with hole transfer from oxidized dye to IrO2 occurring on the microsecond time scale. Once the interaction of the sensitizer with suitable WOCs is optimized, 1/WO3 photoanodes may hold potentialities for the straightforward building of molecular level devices for solar fuel production.

  19. Highly flexible room temperature NO2 sensor based on WO3 nanoparticles loaded MWCNTs-RGO hybrid

    NASA Astrophysics Data System (ADS)

    Yaqoob, Usman; Chung, Gwiy-Sang

    2016-02-01

    Fabrication and characterizations of a flexible NO2 sensor based on tungsten trioxide nanoparticles-loaded multi-walled carbon nanotubes-reduced graphene oxide hybrid (WO3 NPs-loaded MWCNTs-RGO) on a polyimide/polyethylene terephthalate (PI/PET) substrate have been investigated. A viscous gel of the hybrid materials (WO3-MWCNTs-RGO) was prepared with the assistance of α-terpineol. To observe the physical and crystalline properties of hybrid materials FESEM, TEM and XRD was carried-out. Afterwards, sensor was fabricated by drop casting hybrid solution between two fingers gold (Au) electrodes. Finally, gas sensing properties were taken out in open air environment. The sensor showed excellent sensing performance towards NO2 including a maximum response of 17% (to 5 ppm), a limit of detection (LOD) of 1 ppm, and relatively short response/recovery time (7/15 min). The sensing behaviors of the fabricated flexible sensor were evaluated systematically at different curvature angles (0-90°) and after several times bending and relaxing (0-107). The sensor exhibited excellent mechanical flexibility and sensing properties at room temperature without any significant performance degradation even at a curvature angle of 90° and after 106 times bending and relaxing process. The results indicates that economical, light weight and mechanical robustness of the proposed WO3 NPs-MWCNTs- RGO hybrid based sensor can be a promising building block for the development of high performance flexible NO2 sensors.

  20. Selective hydrogenolysis of glycerol to propanediols over supported Pt-Re/WO3/ZrO2 catalysts

    NASA Astrophysics Data System (ADS)

    Tong, Qing; Fan, Yining

    2015-04-01

    Biodiesel is an alternative biodegradable and renewable diesel fuel which can replace petroleum diesel in the future. With the development of biodiesel, the by-product glycerol will surplus. So it is environmentally friendly and cost saving to convert the glycerol to high-valued chemical materials like 1, 3-propanediol and 1, 2-propanediol.Supported Pt-Re/WO3/ZrO2 catalysts were synthesized for the selective hydrogenolysis of glycerol to propanediols. The effects of Re doping on the catalytic performance of Pt/WO3/ZrO2 catalysts were investigated. Experimental results indicate that appropriate amount of Re additives significantly increase the glycerol conversion to more than 99% and 1,3-propandiol and 1,2-propandiol yield still increase compare to Pt/WO3/ZrO2 catalysts while reducing the content of Pt from 2 wt.% to 1.5 wt.%. NH3-TPD results show that the adsorbing capacities of NH3 on the catalyst surface increase with the introduction of Re. Temperature-programmed desorption of chemisorbed CO results indicates that Re greatly improve the dispersion of Pt on the catalysts surface. So we draw the conclusion that Re improves the dehydration activity of glycerol and enhances the hydrogenation activity of dehydration-rearrangement product.

  1. Web-of-Objects (WoO)-based context aware emergency fire management systems for the Internet of Things.

    PubMed

    Shamszaman, Zia Ush; Ara, Safina Showkat; Chong, Ilyoung; Jeong, Youn Kwae

    2014-02-13

    Recent advancements in the Internet of Things (IoT) and the Web of Things (WoT) accompany a smart life where real world objects, including sensing devices, are interconnected with each other. The Web representation of smart objects empowers innovative applications and services for various domains. To accelerate this approach, Web of Objects (WoO) focuses on the implementation aspects of bringing the assorted real world objects to the Web applications. In this paper; we propose an emergency fire management system in the WoO infrastructure. Consequently, we integrate the formation and management of Virtual Objects (ViO) which are derived from real world physical objects and are virtually connected with each other into the semantic ontology model. The charm of using the semantic ontology is that it allows information reusability, extensibility and interoperability, which enable ViOs to uphold orchestration, federation, collaboration and harmonization. Our system is context aware, as it receives contextual environmental information from distributed sensors and detects emergency situations. To handle a fire emergency, we present a decision support tool for the emergency fire management team. The previous fire incident log is the basis of the decision support system. A log repository collects all the emergency fire incident logs from ViOs and stores them in a repository.

  2. Maximizing the photo catalytic and photo response properties of multimodal plasmonic Ag/WO3-x heterostructure nanorods by variation of the Ag size

    NASA Astrophysics Data System (ADS)

    Ghosh, Sirshendu; Saha, Manas; Paul, Sumana; de, S. K.

    2015-10-01

    High quality nearly monodisperse colloidal WO3-x nanorods with an aspect ratio ~18 were synthesized using the thermal decomposition technique. The effects of a capping agent and an activating agent on the nanorod aspect ratio have been studied. Excess carrier concentration due to large oxygen vacancy and smaller width of the nanorods compared to the Bohr exciton radius gives rise to an increase of the band gap. Shape anisotropy in nanorods results in two plasmonic absorbance bands at about 890 nm and 5900 nm corresponding to short axis and long axis plasmon modes. The short axis mode reveals an excellent plasmonic sensitivity of ~345 nm per refractive index. A plasmonic photocatalysis process based on WO3-x nanorods has been developed to synthesize Ag/WO3-x heterostructures consisting of multiple Ag dots with ~2 nm size, randomly decorated on the surface of the WO3-x nanorods. Long time irradiation leads to an increase in the size (5 nm) of Ag nanocrystals concomitant with decrease in the number of Ag nanocrystals attached per WO3-x nanorod. Plasmonic photocatalysis followed by thermal annealing produces only one Ag nanocrystal of size ~10 nm on each WO3-x nanorod. Red shifting and broadening of plasmon bands of Ag nanocrystals and WO3-x nanorods confirm the formation of heterostructures between the metal and semiconductor. Detailed transmission electron micrograph analysis indicates the epitaxial growth of Ag nanocrystals onto WO3-x nanorods. A high photocurrent gain of about 4000 is observed for Ag (10 nm)/WO3-x heterostructures. The photodegradation rate for Rhodamine-B and methylene blue is maximum for Ag (10 nm)/WO3-x heterostructures due to efficient electron transfer from WO3-x nanorods to Ag nanocrystals. Metal plasmon-semiconductor exciton coupling, prominent plasmon absorbance of metal nanoparticles, and formation of an epitaxial interface are found to be the important factors to achieve the maximum photocatalytic activity and fabrication of a high speed

  3. Substrate patterning with NiOx nanoparticles and hot-wire chemical vapour deposition of WO3x and carbon nanostructures

    NASA Astrophysics Data System (ADS)

    Houweling, Z. S.

    2011-10-01

    The first part of the thesis treats the formation of nickel catalyst nanoparticles. First, a patterning technique using colloids is employed to create ordered distributions of monodisperse nanoparticles. Second, nickel films are thermally dewetted, which produces mobile species that self-arrange in non-ordered distributions of polydisperse particles. Third, the mobility of the nickel species is successfully reduced by the addition of air during the dewetting and the use of a special anchoring layer. Thus, non-ordered distributions of self-arranged monodisperse nickel oxide nanoparticles (82±10 nm x 16±2 nm) are made. Studies on nickel thickness, dewetting time and dewetting temperature are conducted. With these particle templates, graphitic carbon nanotubes are synthesised using catalytic hot-wire chemical vapour deposition (HWCVD), demonstrating the high-temperature processability of the nanoparticles. The second part of this thesis treats the non-catalytic HWCVD of tungsten oxides (WO3-x). Resistively heated tungsten filaments exposed to an air flow at subatmospheric pressures, produce tungsten oxide vapour species, which are collected on substrates and are subsequently characterised. First, a complete study on the process conditions is conducted, whereby the effects of filament radiation, filament temperature, process gas pressure and substrate temperature, are investigated. The thus controlled growth of nanogranular smooth amorphous and crystalline WO3-x thin films is presented for the first time. Partially crystalline smooth hydrous WO3-x thin films consisting of 20 nm grains can be deposited at very high rates. The synthesis of ultrafine powders with particle sizes of about 7 nm and very high specific surface areas of 121.7±0.4 m2·g-1 at ultrahigh deposition rates of 36 µm·min-1, is presented. Using substrate heating to 600°C or more, while using air pressures of 3·10-5 mbar to 0.1 mbar, leads to pronounced crystal structures, from nanowires, to

  4. Effect of cannabinoids upon the uptake of folic acid by BeWo cells.

    PubMed

    Araújo, João R; Gonçalves, Pedro; Martel, Fátima

    2009-01-01

    Folic acid (FA) is an essential micronutrient that is particularly important during pregnancy for normal placental and fetal development and growth. The placenta and the fetus become frequently exposed to drugs of abuse such as cannabinoids because of maternal use of these substances. The aim of this study was to investigate the influence of cannabinoids on the uptake of FA by BeWo cells. Acute treatment with anandamide (1-10 micromol/l) caused a 15% decrease in (3)H-FA uptake at pH 7.5. Moreover, tetrahydrocannabinol (THC) (1-10 micromol/l) caused a 30% increase, and AM630 (1 mumol/l) a 15% decrease in this parameter at pH 6.5. Neither the inhibitory effect of anandamide nor the stimulatory effect of THC were changed in the presence of cannabi- noid receptor type 1 or type 2 antagonists (AM251 and AM630, respectively). Chronic treatment (48 h) with THC (100 nmol/l) and AM251 (100 nmol/l) decreased the uptake of (3)H-FA by 20% at pH 7.5, and anandamide (1 micromol/l) and AM630 (10-500 nmol/l) increased it by 30%. Moreover, CP55,940 (10 nmol/l) increased the uptake of (3)H-FA by 30% at pH 6.5. RT-PCR analysis showed that the mRNA levels of the reduced folate transporter 1 increased by 9% after chronic treatment with AM630 (500 nmol/l). The mRNA levels of the proton-coupled folate transporter decreased by 17% and increased by 18% after chronic treatment with THC (0.1 mumol/l) and AM251 (100 nmol/l), respectively. In conclusion, (3)H-FA uptake by BeWo cells is significantly, although not very markedly, changed by several distinct CB receptor agonists and antagonists, both after acute and chronic exposure of the cells. The acute effects of cannabinoid receptor agonists do not seem to be mediated by the cannabinoid receptor, and with a few exceptions the chronic effects do not seem to be related to changes in the expression levels of FA transporters.

  5. Irreversible thermochromic response of RF sputtered nanocrystalline BaWO4 films for smart window applications

    NASA Astrophysics Data System (ADS)

    Anil Kumar, C.; Santhosh Kumar, T.; Pamu, D.

    2015-10-01

    We report irreversible thermochromic behaviour of BaWO4 (BWO) films for the first time. BWO films have been deposited at different substrate temperatures (RT, 200, 400, 600 and 800 °C) using RF magnetron sputtering in pure argon plasma. BWO films deposited at 800 °C exhibit crystalline nature. Also, BWO films deposited in the temperature range of 400 - 600 °C exhibit WO3 as a secondary phase and its weight percentage decreases with an increase in deposition temperature, whereas the films deposited at 800 °C exhibited pure tetragonal phase. FESEM images revealed that as the average particle sizes of the films are higher as compared with the thickness of the films and is explained based on Avrami type nucleation and growth. The transmittance of the films decreases with an increase in deposition temperature up to 600 °C and increases thereafter. Films deposited at 600 °C show ≤ 20% transmittance, looking at the films deposited at room temperature and 800 °C exhibits 90 and 70%, respectively. The refractive index and extinction coefficient of the films show profound dependence on crystallinity and packing density. The optical bandgap of BWO films increases significantly with an increase in O2% during the deposition. The optical bandgap of the BWO films deposited at different temperatures in pure argon plasma, are in the range of 3.7 to 3.94 eV whereas the films deposited at 600 °C under different O2 plasma are in the range of 3.6 - 4.5 eV. The formations of colour centres are associated with the oxygen vacancies, which are clearly seen from the optical bandgap studies. The observed irreversible thermochromic behaviour in BWO films is attributed to the presence of oxygen vacancies that arises due to the electrons trapped at oxygen vacancies causing an inter valence charge transfer of W5+ to W6+ and is confirmed through the change in the optical density (ΔOD). Further, the Raman spectra are being used to quantify the presence of oxygen vacancies and the

  6. Novel microwave assisted sol–gel synthesis (MW-SGS) and electrochromic performance of petal like h-WO{sub 3} thin films

    SciTech Connect

    Kharade, Rohini R.; Patil, K.R.; Patil, P.S.; Bhosale, P.N.

    2012-07-15

    Graphical abstract: Electrochromic intercalation and deintercalation of Li{sup +} ions and electrons is facilitated by providing hexagonal tunnel, trigonal cavity and square window which allows easy and fast insertion and extraction of ions. Highlights: ► Novel two step MW-SGS is first time employed to prepare WO{sub 3} thin films. ► MW-SGS is simple and cost effective technique for preparation of nanostructures. ► Petal-like hexagonal WO{sub 3} nanodisks were successfully deposited. ► O/W ratio calculated by XPS studies is 2.89. ► Good electrochromic performance suggests practical usability of proposed technique. -- Abstract: Use of domestic microwave oven is first time employed for chemical deposition of nanocrystalline hexagonal WO{sub 3} (h-WO{sub 3}) thin films. Low cost precursors like sodium tungstate, hydrochloric acid, oxalic acid and potassium sulfate signifies cost effectiveness of this thin film fabrication route. Scanning electron microscopy images reveal formation of petal like nanodisks. A number of analytical techniques were used to characterize the WO{sub 3} petal like nanodisks, including X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy, FT-IR spectroscopy, Raman scattering spectroscopy, UV–visible spectrophotometry and cyclic voltammetry (CV). The X-ray photoelectron spectroscopic studies revealed 2.89 O/W atomic ratio. The electrical transport studies on WO{sub 3} thin films show semiconducting behavior with n-type semiconductivity. The value of determined coloration efficiency is 57.90 cm{sup 2}/C. The mechanism of Li{sup +} intercalation and deinercalation in h-WO{sub 3} matrix is proposed for enhanced electrochromism.

  7. The anti-proliferative effects of a palm oil-derived product and its mode of actions in human malignant melanoma MeWo cells.

    PubMed

    Komarasamy, Thamil Vaani; Sekaran, Shamala Devi

    2012-01-01

    Melanoma incidence and mortality have risen dramatically in recent years. No effective treatment for metastatic melanoma exists; hence currently, an intense effort for new drug evaluation is being carried out. In this study, we investigated the effects of a palm oil-derived nanopolymer called Bio-12 against human malignant melanoma. The nanopolymers of Bio-12 are lipid esters derived from a range of fatty acids of palm oil. Our study aims to identify the anti-proliferative properties of Bio-12 against human malignant melanoma cell line (MeWo) and to elucidate the mode of actions whereby Bio-12 brings about cell death. Bio-12 significantly inhibited the growth of MeWo cells in a concentration- and time- dependent manner with a median inhibitory concentration (IC₅₀) value of 1/25 dilution after 72 h but was ineffective on human normal skin fibroblasts (CCD-1059sk). We further investigated the mode of actions of Bio-12 on MeWo cells. Cell cycle flow cytometry demonstrated that MeWo cells treated with increasing concentrations of Bio-12 resulted in S-phase arrest, accompanied by the detection of sub-G1 content, indicative of apoptotic cell death. Induction of apoptosis was further confirmed via caspase (substrate) cleavage assay which showed induction of early apoptosis in MeWo cells. In addition, DNA strand breaks which are terminal event in apoptosis were evident through increase of TUNEL positive cells and formation of a characteristic DNA ladder on agarose gel electrophoresis. Moreover, treatment of MeWo cells with Bio-12 induced significant increase in lactate dehydrogenase (LDH) activity. These results show that Bio-12 possesses the ability to suppress proliferation of human malignant melanoma MeWo cells and this suppression is at least partly attributed to the initiation of the S-phase arrest, apoptosis and necrosis, suggesting that it is indeed worth for further investigations.

  8. Synthesis and photoluminescence of Eu3+ doped CaGd2(WO4)4 novel red phosphors for white LEDs applications

    NASA Astrophysics Data System (ADS)

    Li, Guifang; Wei, Yunge; Li, Zhimin; Xu, Gu

    2017-04-01

    To provide a systematic study of scheelite structure tungstates, potentially better red phosphors, series of CaGd2-x(WO4)4:Eux were successfully synthesized by the conventional solid state method. X-ray powder diffraction, scanning electron microscopy, fluorescence spectra, decay lifetime measurement and Judd-Ofelt theory were used to investigate the properties of CaGd2(WO4)4:Eu3+ phosphors. The results reveal that CaGd2(WO4)4 compound has monoclinic system with space group I2/b. Under the excitation at 393 nm, Eu3+ doped CaGd2(WO4)4 phosphor exhibits the dominant red emission peak located at 616 nm, which is ascribed to 5D0 → 7F2 transition of Eu3+ ion. Effect of the calcination temperature on the photoluminescence properties has also been studied and it is found that the emission intensity reaches the maximum at 1273 K. In addition, the optimal doping concentration of Eu3+ is determined to be x = 0.8. It can be confirmed that the dipole-dipole interaction type plays an important role in the energy transfer in CaGd2(WO4)4:Eu3+ phosphors through the concentration quenching curve. The Judd-Ofelt parameters Ω2 and Ω4 have been calculated, indicating the lower site symmetry and higher covalency around Eu3+ ions. The CIE coordinates of CaGd1.2(WO4)4:0.8Eu3+ phosphors are x = 0.649 and y = 0.349, which are close to the standard of NTSC. These results show that CaGd2(WO4)4:Eu3+ phosphor can be a potentially better red emitting phosphor for white light emitting diodes (LEDs).

  9. High-energy lithium-ion hybrid supercapacitors composed of hierarchical urchin-like WO3/C anodes and MOF-derived polyhedral hollow carbon cathodes.

    PubMed

    Xu, Juan; Li, Yuanyuan; Wang, Lei; Cai, Qifa; Li, Qingwei; Gao, Biao; Zhang, Xuming; Huo, Kaifu; Chu, Paul K

    2016-09-22

    A lithium-ion hybrid supercapacitor (Li-HSC) comprising a Li-ion battery type anode and an electrochemical double layer capacitance (EDLC) type cathode has attracted much interest because it accomplishes a large energy density without compromising the power density. In this work, hierarchical carbon coated WO3 (WO3/C) with a unique mesoporous structure and metal-organic framework derived nitrogen-doped carbon hollow polyhedra (MOF-NC) are prepared and adopted as the anode and the cathode for Li-HSCs. The hierarchical mesoporous WO3/C microspheres assembled by radially oriented WO3/C nanorods along the (001) plane enable effective Li(+) insertion, thus exhibit high capacity, excellent rate performance and a long cycling life due to their high Li(+) conductivity, electronic conductivity and structural robustness. The WO3/C structure shows a reversible specific capacity of 508 mA h g(-1) at a 0.1 C rate (1 C = 696 mA h g(-1)) after 160 discharging-charging cycles with excellent rate capability. The MOF-NC achieved the specific capacity of 269.9 F g(-1) at a current density of 0.2 A g(-1). At a high current density of 6 A g(-1), 92.4% of the initial capacity could be retained after 2000 discharging-charging cycles, suggesting excellent cycle stability. The Li-HSC comprising a WO3/C anode and a MOF-NC cathode boasts a large energy density of 159.97 W h kg(-1) at a power density of 173.6 W kg(-1) and 88.3% of the capacity is retained at a current density of 5 A g(-1) after 3000 charging-discharging cycles, which are better than those previously reported for Li-HSCs. The high energy and power densities of the Li-HSCs of WO3/C//MOF-NC render large potential in energy storage.

  10. Selective Catalytic Reduction of NO by NH3 with WO3-TiO2 Catalysts: Influence of Catalyst Synthesis Method

    DOE PAGES

    He, Yuanyuan; Ford, Michael E.; Zhu, Minghui; ...

    2016-02-02

    A series of supported WO3/TiO2 catalysts was prepared by a new synthesis procedure involving co-precipitation of an aqueous TiO(OH)2 and (NH4)10W12O41*5H2O slurry under controlled pH conditions. The morphological properties, molecular structures, surface acidity and surface chemistry of the supported WO3/TiO2 catalysts were determined with BET, in situ Raman, in situ IR and temperature-programmed surface reaction (TPSR) spectroscopy, respectively. Isotopic 18O-16O exchange demonstrated that tungsten oxide was exclusively present as surface WOx species on the TiO2 support with mono-oxo W=O coordination. In contrast to previous studies employing impregnation synthesis that found only surface one mono-oxo O=WO4 site on TiO2, the co-precipitationmore » procedure resulted in the formation of two distinct surface WOx species: mono-oxo O=WO4 (~1010-1017 cm-1) on low defect density patches of TiO2 and a second mono-oxo O=WO4 (~983-986 cm-1) on high defect density patches of TiO2. The concentration of the second WOx surface species increases as a function of solution pH. Both surface WOx sites, however, exhibited the same NO/NH3 SCR reactivity. The co-precipitated WO3-TiO2 catalysts synthesized in alkaline solutions exhibited enhanced performance for the NO/NH3 SCR reaction that is ascribed to the greater number of surface defects on the resulting TiO2 support. For the co-precipitated catalyst prepared at pH10, surface NH4+ species on Br nsted acid sites were found to be more reactive than surface NH3* species on Lewis acid sites for SCR of NO with NH3.« less

  11. ZnWO4 nanorods decorated with Ag/AgBr nanoparticles as highly efficient visible-light-responsive photocatalyst for dye AR18 photodegradation

    NASA Astrophysics Data System (ADS)

    Li, Kebin; Xue, Jie; Zhang, Yanhui; Wei, Hong; Liu, Yalan; Dong, Chengxing

    2014-11-01

    A novel Ag-AgBr/ZnWO4 nanorod heterostructure composite was prepared via a facile deposition-precipitation method with ZnWO4 nanorods as the substrate, and characterized by XRD, SEM-EDX, TEM, XPS, and DRS to confirm its structure, morphology, composition, and optical property. The composite was used as a photocatalyst to destroy azo dye Acid Red 18 (AR18) under visible light irradiation. The effects of catalyst composition, solution pH, catalyst loading, and initial dye concentration on photocatalytic degradation rate and efficiency were examined. It was revealed that the photocatalytic activity of Ag-AgBr/ZnWO4 nanojunction system was higher than that of the single ZnWO4 or Ag-AgBr for AR18 degradation under visible light irradiation. The optimal content of Ag-AgBr in Ag-AgBr/ZnWO4 composite was 0.58:1 of Ag/W molar ratio using in the catalyst preparation. Acid pH and decreasing dye initial concentration were favorable to AR18 photodegradation, but the catalyst loading had an optimal value. The catalyst was stable and recyclable, after five successive cycles the photoactivity was fully maintained and the XRD patterns of AgBr displayed no evident change. Photoluminescence spectra revealed the enhanced photocatalytic activity and stability were closely related to the efficient separation of photogenerated carriers in Ag-AgBr/ZnWO4 nanojunction system. Superoxide radicals and holes were found to be main active species for AR18 photodegradation. Finally, the possible mechanism for AR18 degradation over Ag-AgBr/ZnWO4 nanorods under visible light irradiation was proposed as well.

  12. Organic Solar Cells Based on WO2.72 Nanowire Anode Buffer Layer with Enhanced Power Conversion Efficiency and Ambient Stability.

    PubMed

    You, Longzhen; Liu, Bin; Liu, Tao; Fan, Bingbing; Cai, Yunhao; Guo, Lin; Sun, Yanming

    2017-04-12

    Tungsten oxide as an alternative to conventional acidic PEDOT:PSS has attracted much attention in organic solar cells (OSCs). However, the vacuum-processed WO3 layer and high-temperature sol-gel hydrolyzed WOX are incompatible with large-scale manufacturing of OSCs. Here, we report for the first time that a specific tungsten oxide WO2.72 (W18O49) nanowire can function well as the anode buffer layer. The nw-WO2.72 film exhibits a high optical transparency. The power conversion efficiency (PCE) of OSCs based on three typical polymer active layers PTB7:PC71BM, PTB7-Th:PC71BM, and PDBT-T1:PC71BM with nw-WO2.72 layer were improved significantly from 7.27 to 8.23%, from 8.44 to 9.30%, and from 8.45 to 9.09%, respectively compared to devices with PEDOT:PSS. Moreover, the photovoltaic performance of OSCs based on small molecule p-DTS(FBTTh2)2:PC71BM active layer was also enhanced with the incorporation of nw-WO2.72. The enhanced performance is mainly attributed to the improved short-circuit current density (Jsc), which benefits from the oxygen vacancies and the surface apophyses for better charge extraction. Furthermore, OSCs based on nw-WO2.72 show obviously improved ambient stability compared to devices with PEDOT:PSS layer. The results suggest that nw-WO2.72 is a promising candidate for the anode buffer layer materials in organic solar cells.

  13. Increasing student engagement in science through field-based research: University of Idaho's WoW STEMcore Program

    NASA Astrophysics Data System (ADS)

    Squires, A. L.; Boylan, R. D.; Rittenburg, R.; Boll, J.; Allan, P.

    2013-12-01

    A recent statewide survey assessing STEM perceptions in Idaho showed that high school student interest in science and preparation for college are declining. To address this decline we are piloting an interdisciplinary, community and field-based water science education approach for 10th - 12th grade science courses during the 2013-14 school year called WoW STEMcore. The program is led by graduate students in the University of Idaho (UI) Waters of the West (WoW) program. Our methods are based on proven best practices from eight years of NSF GK-12 experience at UI and over a decade of GK-12 experience at more than 300 programs in the U.S. WoW STEMcore works to strengthen partnerships between WoW graduate students, high school teachers, and regional organizations that work on natural resource management or place-based science education with the intent of sustaining and merging efforts to increase scientific literacy among high school students and to better prepare them for higher education. In addition, graduate students gain outreach, education and communication experience and teachers are exposed to new and relevant research content and methods. WoW STEMcore is fostering these partnerships through water themed projects at three northern Idaho high schools. The pilot program will culminate in Spring 2014 with a regional Water Summit in which all participating students and partners will converge at a two-day youth scientific conference and competition where they can showcase their research and the skills they gained over the course of the year. We hypothesize that through a graduate student-led, field-based program that gets students out of the classroom and thinking about water resource issues in their communities, we will 1) fuel high school students' interest in science through hands on and inquiry-based pedagogy and 2) improve preparation for higher education by providing graduate student mentors to discuss the pathway from high school to college to a career. In

  14. Synthesis and characterization of F-doped Cs{sub 0.33}WO{sub 3−x}F{sub x} particles with improved near infrared shielding ability

    SciTech Connect

    Liu, Jingxiao; Luo, Jiayu; Shi, Fei Liu, Suhua; Fan, Chuanyan; Xu, Qiang; Shao, Guolin

    2015-01-15

    F-doped Cs{sub 0.33}WO{sub 3−x}F{sub x} particles were successfully synthesized by the hydrothermal method with hydrofluoric acid as fluorine source, and a new kind of heat insulating films were prepared from dispersion of Cs{sub 0.33}WO{sub 3−x}F{sub x} nanoparticles in polyvinyl alcohol (PVA) aqueous solution. The effects of F doping on the crystal structure and morphology of Cs{sub 0.33}WO{sub 3−x}F{sub x} particles as well as the near-infrared (NIR) shielding ability and heat insulation properties of Cs{sub 0.33}WO{sub 3−x}F{sub x} films were investigated. The results indicated that HF acid addition could promote the formation of rod-like Cs{sub 0.33}WO{sub 3−x}F{sub x} particles during hydrothermal synthesis and increase the yield of Cs{sub 0.33}WO{sub 3−x}F{sub x} powders. Moreover, the as-prepared films from dispersion solution of Cs{sub 0.33}WO{sub 3−x}F{sub x} particles exhibited higher near-infrared (NIR) shielding ability and heat insulating properties than that of the undoped Cs{sub 0.33}WO{sub 3} film. Particularly, the as-prepared Cs{sub 0.33}WO{sub 3−x}F{sub x} sample with F/W (molar ratio)=0.45 showed best NIR shielding ability and transparent heat insulating performance. The formation mechanism of nanorod-like particles and the effects of F doping on the properties of Cs{sub 0.33}WO{sub 3−x}F{sub x} products were discussed. - Graphical abstract: F-doped Cs{sub 0.33}WO{sub 3−x}F{sub x} particles were successfully synthesized by the hydrothermal method with hydrofluoric acid as fluorine source. HF acid addition in the precursor solution could increase the yield of Cs{sub 0.33}WO{sub 3−x}F{sub x} powders and promote the formation of rod-like Cs{sub 0.33}WO{sub 3−x}F{sub x} particles. Moreover, the as-prepared Cs{sub 0.33}WO{sub 3−x}F{sub x} films from dispersion solution of Cs{sub 0.33}WO{sub 3−x}F{sub x} particles exhibited higher near-infrared (NIR) shielding ability and heat insulating properties than that of the undoped

  15. Trypanosoma cruzi induces cellular proliferation in the trophoblastic cell line BeWo.

    PubMed

    Droguett, Daniel; Carrillo, Ileana; Castillo, Christian; Gómez, Fresia; Negrete, Miguel; Liempi, Ana; Muñoz, Lorena; Galanti, Norbel; Maya, Juan Diego; Kemmerling, Ulrike

    2017-02-01

    Congenital transmission of Trypanosoma cruzi (T. cruzi) is partially responsible for the progressive globalization of Chagas disease. During congenital transmission the parasite must cross the placental barrier where the trophoblast, a continuous renewing epithelium, is the first tissue in contact with the parasite. The trophoblast turnover implies cellular proliferation, differentiation and apoptotic cell death. The epithelial turnover is considered part of innate immunity. We previously demonstrated that T. cruzi induces cellular differentiation and apoptosis in this tissue. Here we demonstrate that T. cruzi induces cellular proliferation in a trophoblastic cell line. We analyzed the cellular proliferation in BeWo cells by determining DNA synthesis by BrdU incorporation assays, mitotic index, cell cycle analysis by flow cytometry, as well as quantification of nucleolus organizer regions by histochemistry and expression of the proliferation markers PCNA and Ki67 by Western blotting and/or immunofluorescence. Additionally, we determined the ERK1/2 MAPK pathway activation by the parasite by Western blotting.

  16. Electrical and electro-optical investigations of liquid crystal cells containing WO3 thin films

    NASA Astrophysics Data System (ADS)

    Strangi, G.; Cazzanelli, E.; Scaramuzza, N.; Versace, C.; Bartolino, R.

    2000-08-01

    An interesting application of the fast ion transport properties of tungsten trioxide is presented, when it is inserted as an electrode in nematic liquid crystal (NLC) cells. In a standard sandwichlike cell the nematic liquid crystal, confined between two transparent plane electrodes of purely electronic conductors [indium tin oxide (ITO)], undergoes a molecular reorientation under the action of an external electric field E. This electrically controlled birefringence (electro-optical switching) is proportional to E2, thus polarity insensitive [L. M. Blinov and V. G. Chigrinov, Electrooptic Effects in Liquid Crystal Materials (Springer-Verlag, New York, 1994)]. When a thin film of tungsten trioxide is deposited by magnetron sputtering onto one of the transparent ITO electrodes, and a NLC cell is assembled with such asymmetry, the electro-optical response becomes polarity sensitive [G. Strangi et al., Appl. Phys. Lett. 74, 534 (1999)]. The analysis of this response suggests the occurrence of a reverse internal electric field, associated with the ionic diffusion process of protons always present in these sputtered WO3 films [E. Cazzanelli et al., Electrochim. Acta 44, 3101 (1999)]. By using an opportune voltage waveform it is possible to evaluate such an internal field. Impedance and cyclic voltammetry measurements were carried out on these cells, comparing ``as-deposited'' and ``annealed'' tungsten trioxide electrodes. These studies confirm that an important ionic diffusion process is involved in the establishment of an internal electric field, which modifies the electro-optical response of the nematic liquid crystal cell.

  17. High-pressure structural phase transitions in CuWO[subscript 4

    SciTech Connect

    Ruiz-Fuertes, J.; Errandonea, D.; Lacomba-Perales, R.; Segura, A.; González, J.; Rodríguez, F.; Manjón, F.J.; Ray, S.; Rodríguez-Hernández, P.; Muñoz, A.; Zhu, Zh.; Tu, C.Y.

    2010-07-23

    We study the effects of pressure on the structural, vibrational, and magnetic behavior of cuproscheelite. We performed powder x-ray diffraction and Raman spectroscopy experiments up to 27 GPa as well as ab initio total-energy and lattice-dynamics calculations. Experiments provide evidence that a structural phase transition takes place at 10 GPa from the low-pressure triclinic phase (P1{sup -}) to a monoclinic wolframite-type structure (P2/c). Calculations confirmed this finding and indicate that the phase transformation involves a change in the magnetic order. In addition, the equation of state for the triclinic phase is determined: V{sub 0} = 132.8(2) {angstrom}{sup 3}, B{sub 0} = 139(6) GPa, and B{prime}{sub 0} = 4. Furthermore, experiments under different stress conditions show that nonhydrostatic stresses induce a second phase transition at 17 GPa and reduce the compressibility of CuWO{sub 4}, B{sub 0} = 171(6) GPa. The pressure dependence of all Raman modes of the triclinic and high-pressure phases is also reported and discussed.

  18. Investigation of thermal and optical properties of thin WO3 films by the photothermal Deflection Technique

    NASA Astrophysics Data System (ADS)

    Gaied, I.; Dabbous, S.; Ben Nasrallah, T.; Yacoubi, N.

    2010-03-01

    Owing to its novel physical properties, as well as its technological implication in many fields, the thermal and optical properties of WO3 thin films are studied here. These thin films are prepared from Ammonium Tungstate and deposited on a glass substrate at 400°C by the Spray Pyrolysis Technique. The thermal properties (Thermal conductivity and thermal diffusivity) were studied by the Photothermal Deflection method in its uniform heating case instead of traditionally a non uniform heating one by comparing the experimental amplitude and phase variations versus square root modulation frequency to the corresponding theoretical ones. The best coincidence between theory and experience is obtained for well-defined values of thermal conductivity and thermal diffusivity. The optical properties (optical absorption spectrum and gap energy) were measured using the Photothermal Deflection Spectroscopy (PDS) by drawing the amplitude and phase variation versus wavelength in experimental way and versus absorption coefficient in theoretical one at a fixed modulation frequency. By comparing point by point the normalised experimental and corresponding theoretical amplitude variation, one can deduce the optical absorption spectrum. Using the Tauc law for energies above the gap we can deduce the gap energy. We notice that these films show low thermal conductivity and high transparency in the visible range.

  19. Structure-dependent electrochromic behavior of WO3 thin films under dry lithiation

    NASA Astrophysics Data System (ADS)

    Ashrit, Pandurang V.

    1999-10-01

    The electrochromic (EC) property, reversible coloration of certain materials under double injection of ions and electrons, of transition metal oxides (TMO) such as tungsten trioxide is known to depend strongly on the nature and structure of these materials. Possibility exists to tailor the EC behavior of the different TMOs as per the optical modulation needed. In this work the electrochromic performance of three types of tungsten trioxide films deposited under different conditions leading to nanocrystalline, polycrystalline and amorphous films has been studied by dry lithiation method. A comparative study of the EC coloration of these three types of films has been carried out, with a special emphasis on the nanocrystalline films. The techniques of spectrophotometry and atomic force microscopy have been employed for this study. Each type of tungsten trioxide (WO3) film exhibits a special nature of coloration indicating the potential for its specific application. The nanocrystalline films seem to exhibit a higher overall coloration efficiency and a selective optical modulation compared to the polycrystalline or amorphous films. These films exhibit a very high degree of transmission in the clear state and a high degree of optical modulation concentrated in the infrared region. Hence, the NC films may be of more interest for smart windows from the point of view of energy efficiency. The amorphous films, and even the polycrystalline films under high degree of lithiation, may be more suited for large area display device application due to their efficiency coloration in the visible region of the spectra.

  20. Temperature-dependent spectroscopy and microchip laser operation of Nd:KGd(WO4)2

    NASA Astrophysics Data System (ADS)

    Loiko, P.; Yoon, S. J.; Serres, J. M.; Mateos, X.; Beecher, S. J.; Birch, R. B.; Savitski, V. G.; Kemp, A. J.; Yumashev, K.; Griebner, U.; Petrov, V.; Aguiló, M.; Díaz, F.; Mackenzie, J. I.

    2016-08-01

    High-resolution absorption and stimulated-emission cross-section spectra are presented for monoclinic Nd:KGd(WO4)2 (Nd:KGW) laser crystals in the temperature range 77-450 K. At room-temperature, the maximum stimulated emission cross-section is σSE = 21.4 × 10-20 cm2 at 1067.3 nm, for light polarization E || Nm. The lifetime of the 4F3/2 state of Nd3+ in KGW is practically temperature independent at 115 ± 5 μs. Measurement of the energy transfer upconversion parameter for a 3 at.% Nd:KGW crystal proved that this was significantly smaller than for alternative hosts, ∼2.5 × 10-17 cm3/s. When cut along the Ng optical indicatrix axis, the Nd:KGW crystal was configured as a microchip laser, generating ∼4 W of continuous-wave output at 1067 nm with a slope efficiency of 61% under diode-pumping. Using a highly-doped (10 at.%) Nd:KGW crystal, the slope efficiency reached 71% and 74% when pumped with a laser diode and a Ti:Sapphire laser, respectively. The concept of an ultrathin (250 μm) Nd:KGW microchip laser sandwiched between two synthetic diamond heat-spreaders is demonstrated.

  1. Spin wave excitations in the tetragonal double perovskite Sr2CuWO6

    NASA Astrophysics Data System (ADS)

    Walker, H. C.; Mustonen, O.; Vasala, S.; Voneshen, D. J.; Le, M. D.; Adroja, D. T.; Karppinen, M.

    2016-08-01

    Sr2CuWO6 is a double perovskite proposed to be at the border between two- and three-dimensional magnetism, with a square lattice of S =1/2 Cu2 + ions. We have used inelastic neutron scattering to investigate the spin wave excitations of the system, to find out how they evolve as a function of temperature, as well as to obtain information about the magnetic exchange interactions. We observed well defined dispersive spin wave modes at 6 K, which partially survive above the magnetic ordering temperature TN=24 K. Linear spin wave theory is used to determine the exchange interactions revealing them to be highly two dimensional in nature. Density functional theory calculations are presented supporting this experimental finding, which is in contrast to a previous ab initio study of the magnetic interactions. Our analysis confirms that not the nearest neighbor, but the next nearest neighbor interactions in the tetragonal a b plane are the strongest. Low incident energy measurements reveal the opening of a 0.6(1) meV gap below TN, which suggests the presence of a very weak single ion anisotropy term in the form of an easy axis along a ̂.

  2. Electronic structure of ordered double perovskite Ba{sub 2}CoWO{sub 6}

    SciTech Connect

    Ray, Rajyavardhan; Choudhary, B. K.; Kumar, Uday; Sinha, T. P.

    2014-04-24

    Ba{sub 2}CoWO{sub 6} (BCoW) has been synthesized in polycrystalline form by solid state reaction at 1200 °C. Structural characterization of the compound was done through X-ray diffraction (XRD) followed by Rietveld analysis of the XRD pattern. The crystal structure is cubic, space group Fm-3m (No. 225) with the lattice parameter, a = 8.210. Optical band-gap of the present system has been calculated using the UV-Vis Spectroscopy and Kubelka-Munk function, it’s value being 2.45 eV. A detailed study of the electronic properties has also been carried out using the density functional theory (DFT) techniques implemented on WIEN2k. Importance of electron-electron interaction between the Co ions leading to half-metallic behavior, crystal and exchange splitting together with the hybridization between O and Co, W has been investigated using the total and partial density of states.

  3. Stable hybrid organic/inorganic photocathodes for hydrogen evolution with amorphous WO3 hole selective contacts.

    PubMed

    Mezzetti, Alessandro; Fumagalli, Francesco; Alfano, Antonio; Iadicicco, Daniele; Antognazza, Maria Rosa; di Fonzo, Fabio

    2017-03-08

    Photoelectrochemical H2 production through hybrid organic/inorganic interfaces exploits the capability of polymeric absorbers to drive photo-induced electron transfer to an electrocatalyst in a water environment. Photoelectrode architectures based on solution-processed organic semiconductors are now emerging as low-cost alternatives to crystalline inorganic semiconductors based on Si, oxides and III-V alloys. In this work, we demonstrate that the stability of a hybrid organic/inorganic photocathode, employing a P3HT:PCBM blend as photoactive material, can be considerably improved by introducing an electrochemically stable WO3 hole selective layer, paired with a TiO2 electron selective layer. This hybrid photoelectrode exhibits a photocurrent of 2.48 mA cm(-2) at 0 VRHE, +0.56 VRHE onset potential and a state-of the art operational activity of more than 10 hours. This work gives the perspective that photoelectrodes based on organic semiconductors, coupled with proper inorganic selective contacts, represent a sound new option for the efficient and durable photoelectrochemical conversion of solar energy into fuels.

  4. An on sun parametric study of solar hydrogen production using WO{sub 3} photoanodes

    SciTech Connect

    Halford, Christopher K.; Boehm, Robert F.

    2011-01-15

    The solar production of hydrogen using photoactive electrodes is a topic receiving much attention in recent years. The use of thin metal oxide films as photoanodes allows the water splitting reaction to occur at a much lower applied voltage than would be necessary with a straight electrolysis process. The University of Nevada Las Vegas in collaboration with the UK based firm Hydrogen Solar and funded by the United States Department of Energy, has developed a prototype of this type of cell using a WO{sub 3} photoanode. An on-sun test facility has been constructed by the UNLV Center for Energy Research (CER) where a study is being conducted with regard to the effects various design parameters on the rate of hydrogen evolution. Parameters being studied include electrolyte temperature, electrolyte flow rate, electrolyte resistivity, applied voltage, and membrane to electrode spacing. The data collected is used in a parametric study of the cell performance. The results of this study are then used to establish general trends as to the effects of these parameters on the performance of the cells outside of a laboratory environment. (author)

  5. Heterogeneous WSx/WO3 thorn-bush nanofiber electrodes for sodium-ion batteries

    DOE PAGES

    Ryu, Won -Hee; Wilson, Hope; Sohn, Sungwoo; ...

    2016-01-25

    Heterogeneous electrode materials with hierarchical architectures promise to enable considerable improvement in future energy storage devices. In this study, we report on a tailored synthetic strategy used to create heterogeneous tungsten sulfide/oxide core–shell nanofiber materials with vertically and randomly aligned thorn-bush features, and we evaluate them as potential anode materials for high-performance Na-ion batteries. The WSx (2 ≤ x ≤ 3, amorphous WS3 and crystalline WS2) nanofiber is successfully prepared by electrospinning and subsequent calcination in a reducing atmosphere. To prevent capacity degradation of the WSx anodes originating from sulfur dissolution, a facile post-thermal treatment in air is applied tomore » form an oxide passivation surface. Interestingly, WO3 thorn bundles are randomly grown on the nanofiber stem, resulting from the surface conversion. We elucidate the evolving morphological and structural features of the nanofibers during post-thermal treatment. The heterogeneous thorn-bush nanofiber electrodes deliver a high second discharge capacity of 791 mAh g–1 and improved cycle performance for 100 cycles compared to the pristine WSx nanofiber. Lastly, we show that this hierarchical design is effective in reducing sulfur dissolution, as shown by cycling analysis with counter Na electrodes.« less

  6. Exposure to ethanol and nicotine induces stress responses in human placental BeWo cells.

    PubMed

    Repo, Jenni K; Pesonen, Maija; Mannelli, Chiara; Vähäkangas, Kirsi; Loikkanen, Jarkko

    2014-01-13

    Human placental trophoblastic cancer BeWo cells can be used as a model of placental trophoblasts. We found that combined exposure to relevant exposure concentrations of ethanol (2‰) and nicotine (15 μM) induces an increase in the amount of reactive oxygen species (ROS). Neither ethanol or nicotine alone, nor their combination affected cell viability. However, nicotine decreased cell proliferation, both alone and combined with ethanol. Nicotine increased the expression of the endoplasmic reticulum (ER)-stress related protein GRP78/BiP, but not another marker of ER-stress, IRE1α. We also studied the effects of nicotine and/or ethanol on phosphorylation and expression of three mitogen-activated protein kinases (MAPKs), i.e. JNK, p38 and ERK1/2. Nicotine decreased the phosphorylation of JNK and also had similar effect on total amount of this protein. Phosphorylation and expression of p38 were increased 1.7- and 1.6-fold, respectively, by nicotine alone, and 1.9- and 2.1-fold by the combined treatment. Some increase (1.8-fold) was also seen in the phosphorylation of ERK2 at 48 h, in cells exposed to both ethanol and nicotine. This study shows that ethanol and nicotine, which harm the development of fetus may induce both oxidative and ER stress responses in human placental trophoblastic cells, implicating these mechanisms in their fetotoxic effects.

  7. Study of multiferroic properties of Bi2Fe2WO9 ceramic for device application

    NASA Astrophysics Data System (ADS)

    Rout, Jyoshna; Choudhary, R. N. P.

    2016-09-01

    The Bi2Fe2WO9 ceramic was prepared using a standard solid-state reaction technique. Preliminary analysis of X-ray diffraction pattern revealed the formation of single-phase compound with orthorhombic crystal symmetry. The surface morphology of the material captured using scanning electron microscope (SEM) exhibits formation of a densely packed microstructure. Comprehensive study of dielectric properties showed two anomalies at 200∘C and 450∘C: first one may be related to magnetic whereas second one may be related to ferroelectric phase transition. The field dependent magnetic study of the material shows the existence of small remnant magnetization (Mr) of 0.052emμ/g at room temperature. The existence of magneto-electric (ME) coupling coefficient along with above properties confirms multi-ferroic characteristics of the compound. Selected range temperature and frequency dependent electrical parameters (impedance, modulus, conductivity) of the compound shows that electric properties are correlated to its microstructure. Detailed studies of frequency dependence of ac conductivity suggest that the material obeys Jonscher’s universal power law.

  8. Characterization of PbWO4 crystals for high-energy physics experiments

    NASA Astrophysics Data System (ADS)

    Kim, M. J.; Park, H.; Kim, H. J.

    2016-09-01

    High-energy physics (HEP) experiments have employed many new types of scintillators. Specifically, bismuth germanate, thallium-doped cesium iodide, and lead tungstate (PbWO4, PWO) have been used for the L3 experiment; CLEO II, Belle and BES-III; and CMS, respectively. PWO has particularly beneficial properties, such as high density, fast decay time, short radiation length and radiation hardness. In this study, we tested the PWO crystals at low temperatures to determine their applicability in future calorimeters. Various crystals from the Proton Antiproton Annihilations at Darmstadt (PANDA) experiment in Giessen, the Bogoroditsk Techno-Chemical Plant (BTCP) in Russia and by Shanghai Institute of Ceramics, Chinese Academy of Sciences (SICCAS) in China were investigated. We studied the scintillation properties of PWO crystals, such as their X-ray luminescence, relative light yields, absolute light yields, energy resolutions, decay times and longitudinal uniformities of their light yields. In addition, we measured the temperature dependences of the light yields and decay times by using a 137Cs γ-ray source. The emission spectra of the PWO crystals consisted of a broad band from 350 nm to 700 nm, and the peak emission wavelength in each spectrum was 420 nm. The emission spectra of the PWO crystals from SICCAS were slightly shifted to longer wavelengths compared with those of the crystals from the other institutions.

  9. Highly sensitive and selective WO3 nanoparticle gas sensor operating in thermally modulated dynamic mode

    NASA Astrophysics Data System (ADS)

    Ionescu, Radu; Hoel, Anders; Granqvist, Claes-Goran; Llobet, Eduard; Heszler, Peter

    2004-05-01

    Nanoparticle films of crystalline WO3, designed for gas sensing applications, were deposited on alumina substrates by reactive gas deposition. H2S, ethanol vapour, and binary mixtures of ethanol/H2S, ethanol/NO2 and H2S/NO2 were used in different concentrations for testing the performance of the sensor device. The sensor was operated in dynamic mode by modulating its temperature between 150 and 250 °C. Coefficients were extracted by applying Fast Fourier Transform (FFT) and Discrete Wavelet Transform (DWT) methods to the dynamic resistance response of the sensor. These coefficients were then used as inputs for pattern recognition methods to extract both quantitative (concentration) and qualitative (chemical selectivity) information about the test gases. After sensor calibration, it was possible to detect as little as 200 ppb of ethanol and 20 ppb of H2S with good accuracy. Furthermore, ethanol and H2S could be detected with good sensitivity and selectivity in the presence of both reducing and oxidising gases.

  10. Thickness Dependent Superconductor-Insulator Transition in K0.33WO3

    NASA Astrophysics Data System (ADS)

    Wu, Phillip; Hart, Chris; Luna, Katherine; Munakata, Ko; Geballe, Theodore H.; Beasley, Malcolm R.

    2014-03-01

    We observe a thickness dependent superconductor to insulator transition in K-doped tungsten bronze superconductors. Via a two-step deposition and post-annealing procedure, K-doped WO3 films with reproducible transport properties are obtained. Reducing the film thickness by reducing the film deposition time results in a superconductor to insulator transition. Scanning electron microscopy (SEM) images show that KWO3 crystallites become both thinner and less connected as the deposition time is reduced. Suppression of the density of states at the Fermi level observed using point contact tunneling spectroscopy in the superconducting films demonstrates that disorder-induced increased Coulomb interactions are present. Using the theory of Belitz for the reduction of Tc due to disorder, we can infer that the film with highest observed Tc has a relatively large disorder dependent electron-phonon interaction parameter λ ~ ~ 1.2. Understanding microscopically why certain films display higher Tc will aid in the search for the trace high Tc superconducting anomalies observed in lightly surface doped bronzes. This work supported by an AFOSR under DoD MURI grant FA9550-09-1-0583.

  11. Renewable energy production by photoelectrochemical oxidation of organic wastes using WO3 photoanodes.

    PubMed

    Raptis, Dimitrios; Dracopoulos, Vassilios; Lianos, Panagiotis

    2017-03-22

    The present work has studied renewable hydrogen production by photoelectrocatalytic degradation of model organic substances representing biomass derived organic wastes. Its purpose was to show that renewable energy can be produced by consuming wastes. The study has been carried out by employing nanoparticulate WO3 photoanodes in the presence of ethanol, glycerol or sorbitol, i.e. three substances which are among typical biomass products. In these substances, the molecular weight and the number of hydroxyl groups increases from ethanol to sorbitol. The photocurrent produced by the cell was the highest in the presence of ethanol, smaller in the case of glycerol and further decreased in the presence of sorbitol. The photocurrent was roughly the double of that produced in the absence of an organic additive thus demonstrating current doubling phenomena. Hydrogen was produced only under illumination and was monitored at two forward bias, 0.8 and 1.6V vs Ag/AgCl. Hydrogen production rates followed the same order as the photocurrent thus indicating that hydrogen production by reduction of protons mainly depends on the current flowing through the external circuit connecting photoanode with cathode. The maximum solar-to-hydrogen efficiency reached by the present system was 2.35%.

  12. Dual absorber Fe2O3/WO3 host-guest architectures for improved charge generation and transfer in photoelectrochemical applications

    NASA Astrophysics Data System (ADS)

    Müller, Alexander; Kondofersky, Ilina; Folger, Alena; Fattakhova-Rohlfing, Dina; Bein, Thomas; Scheu, Christina

    2017-01-01

    In this study the influence of the spatial distribution and of different nanostructures of WO3 and Fe2O3 in the dual absorber system Fe2O3/WO3 was systematically investigated for the first time. WO3 was applied as a scaffold and/or as a surface treatment to mesoporous Fe2O3 films. Both approaches strongly increased the performance compared to the individual photoabsorbers. By combining a host guest architecture with a surface treatment, current densities of about 0.7 mA cm‑2 at 1.23 V versus reversible hydrogen electrode under AM 1.5 illumination with an incident photon-to-current efficiency of 17% at 350 nm were achieved without the use of further catalysts. We could identify several beneficial interactions between Fe2O3 and WO3. WO3 strongly scatters visible light, resulting in increased absorption by Fe2O3 and higher current densities. We also determined a cathodic shift in the onset potential to 0.8 V and increased transfer rates of up to 88%. This combination of beneficial effects proves the viability of the presented device architecture.

  13. Mixed-calcination synthesis of CdWO4/g-C3N4 heterojunction with enhanced visible-light-driven photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Tian, Na; Huang, Hongwei; Zhang, Yihe

    2015-12-01

    CdWO4/g-C3N4 composite photocatalysts have been successfully synthesized by a simple mixed-calcination method for the first time. X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and diffuse reflection spectroscopy (DRS) were carried out to analyze the crystal structure, morphology and optical property of the as-prepared samples. The photocatalytic experiments on rhodamine B (RhB) degradation showed that the 1:10 CdWO4/g-C3N4 photocatalyst exhibited the highest efficiency for degradation of RhB under visible light (λ > 420 nm), which was almost 1.6 and 54.6 times as high as those of the pure g-C3N4 and CdWO4, respectively. This enhancement in visible-light photocatalytic activity of CdWO4/g-C3N4 composite should be attributed to the matchable band structures and interfacial interaction between CdWO4 and g-C3N4, resulting in the efficient separation and transfer of photogenerated charge carriers. It was corroborated by the photoluminescence spectroscopy (PL) and active species trapping experiments.

  14. Facile preparation of hexagonal WO3·0.33H2O/C nanostructures and its electrochemical properties for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Liu, Zhiwei; Li, Ping; Dong, Yuan; Wan, Qi; Zhai, Fuqiang; Volinsky, Alex A.; Qu, Xuanhui

    2017-02-01

    Nano-sized hexagonal WO3·0.33H2O/C is prepared by the solution combustion synthesis & hydrothermal method. This material has been used as the anode for high performance lithium-ion batteries for the first time. Carbon layer is uniformly coated on hexagonal WO3·0.33H2O nanoparticles. The samples are characterized by X-ray diffraction (XRD), thermal analysis (TG-DSC), Raman spectra, scanning and transmission electron microscopy (FESEM and TEM). Electrochemical properties are studied by cyclic voltammetry and galvanostatic charge/discharge cycling. Prepared WO3·0.33H2O/C electrode shows high and reversible capacity of 768 mAh g-1 after 200 cycles at 100 mA g-1, which is higher than the reported orthorhombic WO3·0.33H2O. The specific structure can provide efficient channels for transporting Li+ swiftly. Therefore, hexagonal WO3·0.33H2O/C shows a great potential as the anode material for lithium-ion batteries.

  15. Use of the ES-D3 cell differentiation assay, combined with the BeWo transport model, to predict relative in vivo developmental toxicity of antifungal compounds.

    PubMed

    Li, Hequn; Rietjens, Ivonne M C M; Louisse, Jochem; Blok, Martine; Wang, Xinyi; Snijders, Linda; van Ravenzwaay, Bennard

    2015-03-01

    We investigated the applicability of the ES-D3 cell differentiation assay combined with the in vitro BeWo transport model to predict the relative in vivo developmental toxicity potencies. To this purpose, the in vitro developmental toxicity of five antifungal compounds was investigated by characterizing their inhibitory effect on the differentiation of ES-D3 cells into cardiomyocytes. The BeWo transport model, consisting of BeWo b30 cells grown on transwell inserts and mimicking the placental barrier, was used to determine the relative placental transport velocity. The ES-D3 cell differentiation data were first compared to benchmark doses (BMDs) for in vivo developmental toxicity as derived from data reported in the literature. Correlation between the benchmark concentration for 50% effect (BMCd50) values, obtained in the ES-D3 cell differentiation assay, with in vivo BMD10 values showed a reasonable correlation (R(2)=0.57). When the ES-D3 cell differentiation data were combined with the relative transport rates obtained from the BeWo model, the correlation with the in vivo data increased (R(2)=0.95). In conclusion, we show that the ES-D3 cell differentiation assay is able to better predict the in vivo developmental toxicity ranking of antifungal compounds when combined with the BeWo transport model, than as a stand-alone assay.

  16. Visible-light responsive photocatalytic fuel cell based on WO(3)/W photoanode and Cu(2)O/Cu photocathode for simultaneous wastewater treatment and electricity generation.

    PubMed

    Chen, Quanpeng; Li, Jinhua; Li, Xuejin; Huang, Ke; Zhou, Baoxue; Cai, Weimin; Shangguan, Wenfeng

    2012-10-16

    A visible-light driven photocatalytic fuel cell (PFC) system comprised of WO(3)/W photoanode and Cu(2)O/Cu photocathode was established for organic compounds degradation with simultaneous electricity generation. The central idea for its operation is the mismatched Fermi levels between the two photoelectrodes. Under light illumination, the Fermi level of WO(3)/W photoanode is higher than that of Cu(2)O/Cu photocathode. An interior bias can be produced based on which the electrons of WO(3)/W photoanode can transfer from the external circuit to combine with the holes of Cu(2)O/Cu photocathode then generates the electricity. In this manner, the electron/hole pairs separations at two photoelectrodes are facilitated to release the holes of WO(3)/W photoanode and electrons of Cu(2)O/Cu photocathode. Organic compounds can be decomposed by the holes of WO(3)/W photoanode due to its high oxidation power (+3.1-3.2 V(NHE)). The results demonstrated that various model compounds including phenol, Rhodamine B, and Congo red can be successfully decomposed in this PFC system, with the degradation rate after 5 h operation were obtained to be 58%, 63%, and 74%, respectively. The consistent operation for continuous water treatment with the electricity generation at a long time scale was also confirmed from the result. The proposed PFC system provides a self-sustained and energy-saving way for simultaneous wastewater treatment and energy recovery.

  17. WO3/g-C3N4 composites: one-pot preparation and enhanced photocatalytic H2 production under visible-light irradiation.

    PubMed

    Cheng, Cheng; Shi, Jinwen; Hu, Yuchao; Guo, Liejin

    2017-04-21

    A series of WO3/g-C3N4 composites with different WO3 contents were prepared via a facile one-pot pyrolysis method, and showed notably enhanced visible-light-driven photocatalytic H2-evolution activities, with the highest rate of 400 μmol h(-1) gcat(-1) that was 15.0 times of that for pristine g-C3N4. Contents and sizes of WO3 crystallites in the composites were easily adjusted by changing the molar ratios of (NH4)2WS4 to C3H6N6 in the feed reagents, thereby successfully optimizing the Z-scheme system constructed by WO3 and g-C3N4 and thus effectively reducing the recombination of photogenerated charge carriers in g-C3N4. Moreover, pore volumes and surface areas of the composites were gradually enlarged by introducing WO3 into g-C3N4 via the one-pot preparation strategy, therefore promoting the redox reactions to evolve H2. This work presented an effective route to simultaneously optimize the phase compositions and textural structures of photocatalysts for enhanced H2 evolution.

  18. Enhanced near-infrared shielding ability of (Li,K)-codoped WO3 for smart windows: DFT prediction validated by experiment.

    PubMed

    Yang, Chenxi; Chen, Jian-Feng; Zeng, Xiaofei; Cheng, Daojian; Huan, Haifeng; Cao, Dapeng

    2016-02-19

    By means of hybrid density functional theory (DFT) computations, we found that (Li,K)-codoped WO3 shows a significantly enhanced near-infrared (NIR) absorption ability for smart windows, and investigated the influence of doping through the analysis of the electronic structures of pure and doped hexagonal WO3. Furthermore, this codoped material, with a hexagonal tungsten bronze nanostructure, was successfully prepared via a simple one-step hydrothermal reaction for the first time. Transmission electron microscopy images showed that the as-prepared products possessed a nanorod-like morphology with diameters of about 5-10 nm. It was demonstrated that (Li,K)-codoped WO3 presents a better NIR absorption ability than pure, Li-monodoped or K-monodoped WO3, which is in good agreement with our theoretical predictions. The experiment and simulation results reveal that this enhanced optical property in NIR can be explained by the existence of high free electrons existing in (Li,K)-codoped WO3.

  19. Enhanced near-infrared shielding ability of (Li,K)-codoped WO3 for smart windows: DFT prediction validated by experiment

    NASA Astrophysics Data System (ADS)

    Yang, Chenxi; Chen, Jian-Feng; Zeng, Xiaofei; Cheng, Daojian; Huang, Haifeng; Cao, Dapeng

    2016-02-01

    By means of hybrid density functional theory (DFT) computations, we found that (Li,K)-codoped WO3 shows a significantly enhanced near-infrared (NIR) absorption ability for smart windows, and investigated the influence of doping through the analysis of the electronic structures of pure and doped hexagonal WO3. Furthermore, this codoped material, with a hexagonal tungsten bronze nanostructure, was successfully prepared via a simple one-step hydrothermal reaction for the first time. Transmission electron microscopy images showed that the as-prepared products possessed a nanorod-like morphology with diameters of about 5-10 nm. It was demonstrated that (Li,K)-codoped WO3 presents a better NIR absorption ability than pure, Li-monodoped or K-monodoped WO3, which is in good agreement with our theoretical predictions. The experiment and simulation results reveal that this enhanced optical property in NIR can be explained by the existence of high free electrons existing in (Li,K)-codoped WO3.

  20. WO3 Nanoparticles or Nanorods Incorporating Cs2CO3/PCBM Buffer Bilayer as Carriers Transporting Materials for Perovskite Solar Cells.

    PubMed

    Chen, Chih-Ming; Lin, Zheng-Kun; Huang, Wei-Jie; Yang, Sheng-Hsiung

    2016-12-01

    In this work, we demonstrate a novel carrier transporting combination made of tungsten trioxide (WO3) nanomaterials and Cs2CO3/PCBM buffer bilayer for the fabrication of perovskite solar cells (PSCs). Two different types of WO3, including nanoparticles and nanorods, were prepared by sol-gel process and hydrothermal method, respectively. Cs2CO3/PCBM buffer bilayer was inserted between WO3 and perovskite layers to improve charge transfer efficiency and formation of pinhole-free perovskite layer. Besides, the leakage current of the devices containing Cs2CO3/PCBM buffer bilayer was significantly suppressed. The optimized device based on WO3 nanoparticles and Cs2CO3/PCBM bilayer showed an open-circuit voltage of 0.84 V, a short-circuit current density of 20.40 mA/cm(2), a fill factor of 0.61, and a power conversion efficiency of 10.49 %, which were significantly higher than those of PSCs without Cs2CO3/PCBM buffer bilayer. The results revealed that the combination of WO3 nanomaterials and Cs2CO3/PCBM bilayer provides an effective solution for improving performances of PSCs.