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Sample records for kisho joho wo

  1. The properties of single WO stars

    NASA Astrophysics Data System (ADS)

    Tramper, F.; Straal, S. M.; Gräfener, G.; Kaper, L.; de Koter, A.; Langer, N.; Sana, H.; Vink, J. S.

    2015-01-01

    The enigmatic oxygen sequence Wolf-Rayet (WO) stars represent a very late stage in massive star evolution, although their exact nature is still under debate. The spectra of most of the WO stars have never been analysed through detailed modelling with a non-local thermodynamic equilibrium expanding atmosphere code. Here we present preliminary results of the first homogeneous analysis of the (apparently) single WOs.

  2. Improved photoelectrochemical water oxidation by the WO3/CuWO4 composite with a manganese phosphate electrocatalyst.

    PubMed

    Nam, Ki Min; Cheon, Eun Ah; Shin, Won Jung; Bard, Allen J

    2015-10-01

    We describe a composite of the n-type semiconductors for the photoelectrochemical oxygen evolution reaction (OER). A simple drop-casting technique of mixed precursors and a one-step annealing process were used in the synthesis of the WO3/CuWO4 composite. The composite showed improved photocurrent for water oxidation compared to either of the two compounds individually. We discuss possible electron-hole separation mechanisms in two semiconductors comprising a primary photon-absorbing semiconductor of CuWO4 with a secondary semiconductor of WO3. When the WO3/CuWO4 composite is simultaneously irradiated, the photogenerated hole from the WO3 valence band transfers to CuWO4, which results in an enhanced charge separation of CuWO4. Furthermore, the OER catalytic activity of manganese phosphate (MnPO) was compared to manganese oxide nanoparticles (Mn2O3) by electrochemical measurements, showing that the manganese phosphate was more efficient for the OER reaction. To investigate the effect of catalysts on semiconductors, manganese phosphate was deposited on the WO3/CuWO4 composite. The result demonstrates the promise of manganese phosphate for improving the photocurrent as well as the stability of the WO3/CuWO4 composite. PMID:26371544

  3. Nd2(WO4)3

    PubMed Central

    Weil, Matthias; Stöger, Berthold; Aleksandrov, Lyubomir

    2009-01-01

    The title compound, dineodymium(III) tris­[tungstate(VI)], is a member of the Eu2(WO4)3 structure family and crystallizes isotypically with other rare earth tungstates and molybdates of this formula type. The structure is a derivative of the scheelite (CaWO4) structure and can be considered as an ordered defect variant with a threefold scheelite supercell and one rare earth (RE) site unoccupied. The Nd3+ cations are coordinated by eight O atoms in form of a distorted bicapped trigonal prism. The two unique W cations are tetra­hedrally surrounded by O atoms. One WO4 tetra­hedron has 2 symmetry and is relatively undistorted whereas the other tetra­hedron differs considerably from an ideal geometry. This is caused by an additional remote O atom at a distance of 2.149 (4) Å. The resulting WO4 + 1 polyhedra form W2O8 dimers through edge-sharing. Together with the WO4 and NdO8 units, the three-dimensional set-up is accomplished. PMID:21582980

  4. Bacteriophage WO in Wolbachia infecting terrestrial isopods.

    PubMed

    Braquart-Varnier, Christine; Grève, Pierre; Félix, Christine; Martin, Gilbert

    2005-11-18

    Wolbachia are maternally inherited intracellular alpha-proteobacteria that infect a wide range of arthropods. They are associated with a number of different reproductive phenotypes in arthropods and nematodes. In isopod crustacean, Wolbachia are responsible for feminization of genetic males in many species, and for cytoplasmic incompatibility in two species. In this paper, we report the first detection of phage WO from Wolbachia infecting terrestrial isopods. All Wolbachia strains tested in this study were infected with phage WO. Based on the orf7 phage sequence, we identified three different phage sequences in four Wolbachia strains. The phage of Wolbachia infecting Armadillidium vulgare seems to be not active, unlike other phages WO previously described in arthropods. PMID:16198306

  5. Detection and phylogenetic analysis of bacteriophage WO in spiders (Araneae).

    PubMed

    Yan, Qian; Qiao, Huping; Gao, Jin; Yun, Yueli; Liu, Fengxiang; Peng, Yu

    2015-11-01

    Phage WO is a bacteriophage found in Wolbachia. Herein, we represent the first phylogenetic study of WOs that infect spiders (Araneae). Seven species of spiders (Araneus alternidens, Nephila clavata, Hylyphantes graminicola, Prosoponoides sinensis, Pholcus crypticolens, Coleosoma octomaculatum, and Nurscia albofasciata) from six families were infected by Wolbachia and WO, followed by comprehensive sequence analysis. Interestingly, WO could be only detected Wolbachia-infected spiders. The relative infection rates of those seven species of spiders were 75, 100, 88.9, 100, 62.5, 72.7, and 100 %, respectively. Our results indicated that both Wolbachia and WO were found in three different body parts of N. clavata, and WO could be passed to the next generation of H. graminicola by vertical transmission. There were three different sequences for WO infected in A. alternidens and two different WO sequences from C. octomaculatum. Only one sequence of WO was found for the other five species of spiders. The discovered sequence of WO ranged from 239 to 311 bp. Phylogenetic tree was generated using maximum likelihood (ML) based on the orf7 gene sequences. According to the phylogenetic tree, WOs in N. clavata and H. graminicola were clustered in the same group. WOs from A. alternidens (WAlt1) and C. octomaculatum (WOct2) were closely related to another clade, whereas WO in P. sinensis was classified as a sole cluster. PMID:25903547

  6. Synthesis and electrochemical properties of SnWO4.

    PubMed

    Dan, Meiyu; Cheng, Mengqi; Gao, Hong; Zheng, Hao; Feng, Chuanqi

    2014-03-01

    In this paper, a pure SnWO4 was synthesized by solvothermal method. The glucose as a carbon sources was mixed with SnWO4 to prepared SnWO4/C composite. The structure and morphology were characterized by XRD and SEM techniques. The electrochemical properties of SnWO4 and SnWO4/C composite were studied by battery comprehensive testing system and AC impedance spectroscopy. The results showed that the alpha-SnWO4 phase was formed and its particles were ranged from 50 to 250 nm. The alpha-SnWO4/C composites behaved higher reversible discharge capacity and better cycle performance than that of alpha-SnWO4. The reversible discharge capacity of SnWO4/C composites was 780 mA h/g at the current density (50 mA/g) and it could keep at 600 mA h/g after 30 cycles. The reason for SnWO4/C composite to behave outstanding electrochemical properties was discussed also. PMID:24745237

  7. 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.

  8. Effects of WO3 Particle Size in WO3/Epoxy Resin Radiation Shielding Material

    NASA Astrophysics Data System (ADS)

    Dong, Yu; Chang, Shu-Quan; Zhang, Hong-Xu; Ren, Chao; Kang, Bin; Dai, Ming-Zhu; Dai, Yao-Dong

    2012-10-01

    To verify the influence of the functional elements particular size for the radiation attenuation coefficients and mechanical properties radiation shielding material based on epoxy resin, we prepare two WO3/E44 samples with different particular sizes of WO3 by a solidified forming approach. The linear attenuation coefficients of these samples are measured for γ-ray photo energies of 59.6, 121.8, and 344.1 keV, etc. using narrow beam transmission geometry. It is found that the linear attenuation coefficients would increase with the decreasing particle size of the WO3 in the epoxy resin based radiation shielding material. The theoretical values of the linear attenuation coefficients and mass attenuation are calculated using WinXcom, and good agreements between the experimental data and the theoretical values are observed. From the studies of the obtained results, it is reported that from the shielding point of view the nano-WO3 is more effective than micro-WO3 in the epoxy resin based radiation shielding material.

  9. AZD-4818, a chemokine CCR1 antagonist: WO2008103126 and WO2009011653.

    PubMed

    Norman, Peter

    2009-11-01

    The applications WO2008103126 and WO2009011653, respectively, claim: i) Combinations of a spirocyclic piperidine chemokine CCR1 antagonist with a corticosteroid, and their use for the treatment of asthma and chronic obstructive pulmonary disease. ii) Processes for the preparation of a spirocyclic piperidine derivative, a chemokine CCR1 antagonist. These applications point to the preferred compound being a development compound. The evidence for this compound being AZD-4818, a chemokine CCR1 antagonist that was in Phase II development for the treatment of chronic obstructive pulmonary disease, is reviewed in the light of these and earlier patents relating to it. PMID:19586423

  10. 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.

  11. 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).

  12. 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.

  13. Orthorhombic WO 3Formed via a Ti-Stabilized WO 3· {1}/{3}H 2O Phase

    NASA Astrophysics Data System (ADS)

    Pecquenard, B.; Lecacheux, H.; Livage, J.; Julien, C.

    1998-01-01

    Stable solutions of WO3precursors have been prepared via the dissolution of tungstic acid, H2WO4, in hydrogen peroxide. A crystalline peroxopolytungstic acid WO3·H2O2·nH2O (n≈0.1) is obtained upon drying. Peroxo groups decompose at 200°C, giving an amorphous tungsten oxide that crystallizes into the stable monoclinic WO3around 400°C. Completely different results are obtained when Ti(OPri)4is added to the precursor solution. The orthorhombic phase WO3·{1}/{3}H2O is first obtained. As is well known, this hydrated oxide leads to h-WO3and m-WO3upon heating. However, in the presence of TiIV, a new metastable orthorhombic tungsten oxide is formed around 400°C. It then transforms irreversibly upon further heating into the stable monoclinic WO3. The presence of TiIVseems to stabilize this new orthorhombic phase.

  14. Microwave-assisted synthesis of Zn-WO3 and ZnWO4 for pseudocapacitor applications

    NASA Astrophysics Data System (ADS)

    Kumar, R. Dhilip; Andou, Y.; Karuppuchamy, S.

    2016-05-01

    Nanosized Zn-WO3 and ZnWO4 materials have been prepared by microwave irradiation method. The physico-chemical characterization of the prepared nanomaterials was carried out by X-ray diffraction (XRD) and high resolution-scanning electron microscopy (HR-SEM) techniques. The size and shape of the ZnWO4 material can be controlled by changing the temperature. The XRD analysis revealed the formation of monoclinic phase of the calcined nanopowder. The HR-SEM images showed the sphere and plate shape particles. The electrochemical behavior of the ZnWO4 modified electrodes was investigated using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) techniques. The synthesized material shows the pseudocapacitance. The specific capacitance of 35.70 F/g was achieved for the Zn-WO3 nanopowder.

  15. 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.

  16. Synthesis, Characterization, and Gas Sensing Applications of WO3 Nanobricks

    NASA Astrophysics Data System (ADS)

    Xiao, Jingkun; Song, Chengwen; Dong, Wei; Li, Chen; Yin, Yanyan; Zhang, Xiaoni; Song, Mingyan

    2015-08-01

    WO3 nanobricks are fabricated by a simple hydrothermal method. Morphology and structure of the WO3 nanobricks are characterized by scanning electron microscopy and x-ray diffraction. Gas sensing properties of the as-prepared WO3 sensor are systematically investigated by a static gas sensing system. The results show that the WO3 nanobricks with defect corners demonstrate good crystallinity, and the mean edge length and wall thickness are 1-1.5 and 400 nm, respectively. The WO3 sensor achieves its maximum sensitivity to 100 ppm ethanol at the optimal operating temperature of 300 °C. Ultra-fast response time (2-3 s) and fast recovery time (4-11 s) of the WO3 sensor toward 100 ppm ethanol are also observed at this optimal operating temperature. Moreover, the WO3 sensor exhibits high selectivity to other gases such as methanol, benzene, hexane, and dichloromethane, indicating its excellent potential application as a gas sensor for ethanol detection.

  17. Examination of the Reduction of the WO3/Zn System

    NASA Astrophysics Data System (ADS)

    Papazoglou, M.; Chaliampalias, D.; Vourlias, G.; Stergioudis, G.

    2010-01-01

    Tungsten is used in several electrical, optical, electronic and chemical applications. The crystal structure and the morphology of tungsten crystallites influence its behavior used in most applications. A method for producing pure tungsten with the desired characteristics is by a reduction reaction using the Self-propagating High temperature Synthesis technique. The reduction of WO3 is accompanied by morphological changes of its structure crystallites, while the addition of Zn to WO3 powder enhances considerably the reduction rate. Moreover zinc reacts with oxygen forming zinc oxide. In the first steps of the reduction process the well defined crystals of WO3 transform to plates-like whispers to WO2,92. With 0,1% wt. Zn concentration, needle shaped crystal growth is favored while mixtures containing 0,3 %wt. zinc favored the formation of WO2,72. The rapid formation of whiskers, with average size 50 μm, seems to result from a vapor to solid transformation. The formation of whiskers of WO2,72 is the controlling step, in determining the final particle size of the tungsten powder. The final reduction step of WO2 to tungsten is achieved without any further morphological change.

  18. 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.

  19. Preparation and Characteristics of Al Matrix Composites Reinforced with ZnWO4 Coated (WO3p + ABOw) Hybrid Reinforcements

    NASA Astrophysics Data System (ADS)

    Feng, Y. C.; Cao, G. J.; Fan, G. H.; Wang, L. P.; Geng, L.

    2013-02-01

    In this article, a ZnWO4 coating was prepared successfully on the surfaces of WO3 particulates and Al18B4O33 whiskers by a chemical precipitation method. Then the Al matrix composite with coated reinforcements was fabricated by a squeeze casting technique. Scanning electronic microscope analysis shows that a thin coating is coated on the surfaces of reinforcements. Differential thermal analysis and x-ray diffraction (XRD) results show that the Zn(OH)2 decomposes at 248°C and that the ZnWO4 is produced by reaction WO3 with ZnO at 716°C. Transmission electronic microscope and XRD analysis show that the coating of ZnWO4 is effective to prevent interfacial reaction between the WO3 particle and the Al matrix. The mechanical property testing shows that the ultimate tensile strength, elastic modulus, and elongation of the hybrid composites with coated reinforcements are improved greatly by introduction of ZnWO4 coating.

  20. Chromic Mechanism in Amorphous WO3 Films

    SciTech Connect

    Zhang, J. G.; Benson, D. K.; Tracy, C. E.; Deb, S. K.; Czanderna, A. W.

    1997-06-01

    We propose a new model for the chromic mechanism in amorphous tungsten oxide films (WO3-y .cntdot. nH2O). This model not only explains a variety of seemingly conflicting experimental results reported in the literature that cannot be explained by existing models, it also has practical implications with respect to improving the coloring efficiency and durability of electrochromic devices. According to this model, a typical as-deposited tungsten oxide film has tungsten mainly in W6+ and W4+ states and can be represented as W6+(1-y) W4+(y)O(3-y) .cntdot. nH2O. The proposed chromic mechanism is based on the small polaron transition between the charge-induced W5+ state and the orignial W4+ state insteasd of the W5+ and W6+ states as suggested in previous models. The correlation between the electrochromic and photochromic behavior in amorphous tungsten oxide films is also discussed.

  1. NH3 sensing characteristics of nano-WO3 thin films deposited on porous silicon.

    PubMed

    Sun, Fengyun; Hu, Ming; Sun, Peng; Zhang, Jie; Liu, Bo

    2010-11-01

    The NH3 sensing characteristics of nano-tungsten trioxide (WO3) thin films deposited on porous silicon (PS) were investigated in the present study. Porous silicon layer was first prepared by electrochemical etching in an HF-based solution on a p(+)-type silicon substrate. Then, WO3 nano-films were deposited on the porous silicon layer by DC magnetron sputtering. Pt electrodes were deposited on the top surface of the WO3 films to obtain the WO3/PS gas sensor. The WO3 films deposited on PS were characterized by SEM, XRD and XPS. The NH3 sensing characteristics for WO3/PS gas sensor were tested at room temperature and 50 degrees C. The results showed that the NH3 sensing characteristics of WO3/PS were superior to WO3/Al2O3 at room temperature. The sensing mechanism of the nano-WO3 thin films based on PS was also discussed. PMID:21138022

  2. Synthesis and photoelectrochemical properties of CdWO4 and CdS/CdWO4 nanostructures

    NASA Astrophysics Data System (ADS)

    Xu, Weina; Zheng, Chunhua; Hua, Hao; Yang, Qi; Chen, Lin; Xi, Yi; Hu, Chenguo

    2015-02-01

    A facile composite-salt-mediated strategy is employed for the first time to synthesize CdWO4 nanowire and nanoflower arrays on cadmium foil substrates. The photoelectrochemical (PEC) properties are measured on the electrodes made of the CdWO4 nanowire and nanoflower arrays under the simulated sunlight illumination. Both electrodes display high sensitive response and photocurrent stability. The photocurrent density of the nanowire arrays electrode reach 0.35 mA/cm2, which is about 3 times as much as that of the nanoflower array electrode. To improve the visible light photocurrent response, CdS nanoparticles are deposited on the CdWO4 nanowire arrays to form a CdS/CdWO4 heterojunction. Remarkably enhanced photoresponse is observed on the CdS/CdWO4 heterostructure and the photocurrent intensity is about twice as much as that of the electrode made of the pure CdWO4 nanowire arrays. The photoelectric mechanism is also discussed by the crystal structure and morphology characterization, optical band gap and carrier mobility analysis. This work presents a new design of a photoelectrochemical device for possible applications in photoelectrolysis of water and solar cells or highly sensitive light detection.

  3. In-situ transmission electron microscopy imaging of formation and evolution of LixWO3 during lithiation of WO3 nanowires

    NASA Astrophysics Data System (ADS)

    Qi, Kuo; Li, Xiaomin; Sun, Muhua; Huang, Qianming; Wei, Jiake; Xu, Zhi; Wang, Wenlong; Bai, Xuedong; Wang, Enge

    2016-06-01

    The phase transition from monoclinic WO3 to cubic LixWO3 during lithiation of WO3 is one of the key features for tungsten oxide as the most used electrochromic material. Conventionally, the lithium intercalation of WO3 has been studied by building generic layered electrochromic device combining with structural characterization and electrochemistry measurement at macro scale. In-situ transmission electron microscopy (in-situ TEM) has been proposed as a method for revealing the detailed mechanism of structural, physical, and chemical properties. Here, we use in-situ TEM method to investigate the formation and evolution of LixWO3 in real-time during the electrochemical lithiation of WO3 nanowires. The dynamic lithiation process is recorded by TEM imaging, diffraction, and electron energy loss spectroscopy. The WO3-LixWO3 phase boundary of reaction front has been observed at high resolution. The timeliness of crystallinity of LixWO3 and the intercalation channels for Li ions are also identified. Moreover, the co-existence of both polycrystalline Li-poor area and amorphous Li-rich phases of LixWO3 was found. Our results provide an insight into the basic lithiation process of WO3, which is significantly important for understanding the electrochromic mechanism of tungsten oxide.

  4. 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.

  5. Lifetime of electrochromism of amorphous WO sub 3 -TiO sub 2 thin films

    SciTech Connect

    Hashimoto, S.; Matsuoka, H. )

    1991-08-01

    In this paper, the degradation of the electrochromism of amorphous WO{sub 3} and WO{sub 3}-TiO{sub 2} films prepared by electron-beam deposition are studied. The lifetime of the WO{sub 3}-TiO{sub 2} films is five times longer than that of the WO{sub 3} films. SIMS and XPS analyses have revealed that lithium accumulates as OLi in the WO{sub 3} films, but that it cannot accumulate in the WO{sub 3}-TiO{sub 2} film. Ols electron energy loss spectroscopy (EELS) spectra have indicated that the change of the electronic structure for the WO{sub 3}-TiO{sub 2} film by coloration is smaller than that for the WO{sub 3} film. The increase of plasmon energy has been obtained in low loss EELS spectrum and the increase of the bond length in the WO{sub 3}-TiO{sub 2} film has been measured by Raman spectrum. From these results, the number of the defect bonds as a trapping site of lithium is reduced and the bond length of W-O decreases in the WO{sub 3}-TiO{sub 2} films. The authors conclude that lithium cannot accumulate in the structure of the WO{sub 3}-TiO{sub 2} film and that the structure gives a prolonged lifetime to the electrochromism.

  6. 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. PMID:25549007

  7. Nanostructure-based WO3 photoanodes for photoelectrochemical water splitting.

    PubMed

    Liu, Xien; Wang, Fengying; Wang, Qing

    2012-06-14

    Nanostructured WO(3) has been developed as a promising water-splitting material due to its ability of capturing parts of the visible light and high stability in aqueous solutions under acidic conditions. In this review, the fabrication, photocatalytic performance and operating principles of photoelectrochemical cells (PECs) for water splitting based on WO(3) photoanodes, with an emphasis on the last decade, are discussed. The morphology, dimension, crystallinity, grain boundaries, defect and separation, transport of photogenerated charges will also be mentioned as the impact factors on photocatalytic performance. PMID:22534756

  8. 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.

  9. Development of WO3 Thin Films Using Nanoscale Silicon Particles

    NASA Astrophysics Data System (ADS)

    Aliev, Ali E.; Park, Chul

    2000-06-01

    The WO3-x-0.1TiO2-y thin films prepared by the sol-gel route exhibit increased lifetime and stability. A sol-gel solution mixed with nanoscopic silicon oxide particles (40 nm, 200 nm) was spin-coated onto an indium tin oxide (ITO)-covered glass substrate followed by further surface development by chemical etching. A significantly faster response time of the electrochromic cell due to the increase of the surface area of the WO3/electrolyte interface and enhancement of the lithium ion diffusion rate have been obtained. The coloration efficiency was found to be much higher in the areas surrounding incorporated nanoscale particles.

  10. Photo-Induced Unpinning of Fermi Level in WO3

    PubMed Central

    Malagù, Cesare; Carotta, Maria C.; Comini, Elisabetta; Faglia, Guido; Giberti, Alessio; Guidi, Vincenzo; Maffeis, Thierry G.G.; Martinelli, Giuliano; Sberveglieri, Giorgio; Wilks, Steve P.

    2005-01-01

    Atomic force and high resolution scanning tunneling analyses were carried out on nanostructured WO3 films. It turned out that the band gap measured by scanning tunneling spectroscopy at surface is lower than the band gap reported in the literature. This effect is attributed to the high density of surface states in this material, which allows tunneling into these states. Such a high density of surface states pins the Fermi level resulting in modest surface activity at room temperature. Photo activation of WO3 results in unpinning of the Fermi level and thereby in higher chemical activity at surface.

  11. Photocatalytic water treatment over WO 3 under visible light irradiation combined with ozonation

    NASA Astrophysics Data System (ADS)

    Nishimoto, Shunsuke; Mano, Takayuki; Kameshima, Yoshikazu; Miyake, Michihiro

    2010-11-01

    Photocatalytic water treatment over bare WO 3 under visible light irradiation combined with ozonation (O 3/vis/WO 3) was investigated using an aqueous phenol solution as model wastewater. The O 3/vis/WO 3 treatment exhibited a much higher total organic carbon removal than ozonation alone. Bare WO 3 was found to function as an active visible-light-responsive photocatalyst for decomposition of organic compounds in the presence of ozone, which readily reacts with photoexcited electrons in the conduction band of WO 3.

  12. The WO3/WS2 nanostructures: Preparation, characterization and optical absorption properties

    NASA Astrophysics Data System (ADS)

    Cao, Shixiu; Zhao, Cong; Han, Tao; Peng, Lingling

    2016-07-01

    The WO3/WS2 nanostructures were successfully prepared using a two-step hydrothermal/gas phase method. The physical properties of the nanostructures were characterized using XRD, SEM, TEM, UV-visible spectroscopy. The WO3/WS2 nanostructures obtained were coexistence of WO3 and WS2 in the same particle. The WO3/WS2 nanostructures contained a wide and intensive absorption in the UV-visible light region of 245-750 nm, which showed that the WO3/WS2 nanostructures may have a potential application as an UV-visible photocatalyst.

  13. 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. PMID:26726834

  14. 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

  15. 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. PMID:26913026

  16. Tungsten Trioxide (WO3) Nanoparticles as a New Anode Material for Sodium-Ion Batteries.

    PubMed

    Santhosha, A L; Das, Shyamal K; Bhattacharyya, Aninda J

    2016-04-01

    Tungsten trioxide (WO3) is investigated for the first time as an anode material for sodium-ion batteries. Pristine WO3 displays a discharge potential plateau at 1 V and exhibits a 1st discharge cycle sodium storage capacity of 640 mAh g-1. Electronic wiring of WO3 with graphene oxide (GO, 1% by weight) led to a significant increase in the storage capacity and cyclability of WO3. As a result, the discharge capacity of 1% GO-WO3 is enhanced to 927 mAh g-1 in the 1st discharge cycle. The electrochemical intercalation of Na in to WO3 and (1%) GO-WO3 as obtained from galvanostatic charge/discharge cycling is also supported by cyclic voltammetry. PMID:27451776

  17. 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. PMID:22669278

  18. Electrochromic properties of electrodeposited tungsten oxide (WO3) thin film

    NASA Astrophysics Data System (ADS)

    Dalavi, D. S.; Kalagi, S. S.; Mali, S. S.; More, A. J.; Patil, R. S.; Patil, P. S.

    2012-06-01

    In this work, we report on a potentiostatic electrochemical procedure employing an ethanolic solution of peroxotungstic acid yielded tungsten oxide (WO3) films specifically for transmissive electrochromic devices (ECDs) such as "smart windows". WO3 film was confirmed from the binding energy determination by X-ray photoelectron spectroscopic studies. The diffusion coefficient during intercalation and deintercalation was found to be 2.59×10-10 and 2.40×10-10 cm2/C. Electrodeposited WO3 produce high color/bleach transmittance difference up to 74% at 630 nm. On reduction of WO3, the CIELAB 1931 2% color space coordinates show the transition from colorless to the deep blue state (L=95.18, a=2.12, b=0.3138, and L=57.78, a=-21.79, b=0.244) with steady decrease in relative luminance. The highest coloration efficiency (CE) of 92 cm2/C and good response time of 10.28 for coloration (reduction) and 3.2 s for bleaching (oxidation) was observed with an excellent reversibility of 89%.

  19. Ultrafine MnWO4 nanoparticles and their magnetic properties

    NASA Astrophysics Data System (ADS)

    Ungelenk, Jan; Roming, Sabine; Adler, Peter; Schnelle, Walter; Winterlik, Jürgen; Felser, Claudia; Feldmann, Claus

    2015-08-01

    Ultrafine nanoparticles of MnWO4, a compound showing low-temperature multiferroicity in the bulk, were synthesized by the polyol method. Studies using powder X-ray diffraction, scanning and transmission electron microscopy, dynamic light scattering, differential sedimentation and sorption techniques show the formation of a single-phase material, which is composed of MnWO4 nanoparticles with a prolate ellipsoidal shape (short axis of 4-5 nm, long axis of 11-12 nm) and an unprecedented high specific surface area of 166 m2 g-1. The as-prepared MnWO4 nanoparticles are readily crystalline after the liquid-phase synthesis. Temperature and field dependent magnetization measurements indicate antiferromagnetic behavior with a single magnetic phase transition near TN ≈ 6 K. In contrast, three successive transitions below 14 K were reported for multiferroic bulk-MnWO4. Above TN, the nanoparticles show Curie-Weiss-type paramagnetic behavior. Due to the large paramagnetic moment of Mn2+ (μeff ≈ 6.2 μB), the nanoparticles can be easily manipulated by a bar magnet at ambient temperature.

  20. Characterisation and application of WO3 films for electrochromic devices

    NASA Astrophysics Data System (ADS)

    Stapinski, Thomas; Marszalek, Konstanty; Swatowska, Barbara; Stanco, Agnieszka

    2013-07-01

    Electrochromic system is the one of the most popular devices using color memory effect under the influence of an applied voltage. The electrochromic system was produced based on the thin WO3 electrochromic films. Films were prepared by RF magnetron sputtering from tungsten targets in a reactive Ar+O2 gas atmosphere of various Ar/O2 ratios. The technological gas mixture pressure was 3 Pa and process temperature 30°C. Structural and optical properties of WO3 films were investigated for as-deposited and heat treated samples at temperature range from 350°C to 450°C in air. The material revealed the dependence of properties on preparation conditions and on post-deposition heat treatment. Main parameters of thin WO3 films: thickness d, refractive index n, extinction coefficient k and energy gap Eg were determined and optimized for application in electrochromic system. The main components of the system were glass plate with transparent conducting oxides, electrolyte, and glass plate with transparent conducting oxides and WO3 layer. The optical properties of the system were investigated when a voltage was applied across it. The electrochromic cell revealed the controllable transmittance depended on the operation voltage.

  1. 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.

  2. Microwave Intercalation Synthesis of WO3 Nanoplates and Their NO-Sensing Properties

    NASA Astrophysics Data System (ADS)

    Tu, Yue; Li, Qiang; Jiang, Danyu; Wang, Qi; Feng, Tao

    2015-01-01

    Tungsten(VI) oxide (WO3) nanoplates were successfully synthesized by microwave intercalation. Through microwave processing, an intermediate product H2W2O7· xH2O was prepared quickly to greatly decrease the time used to prepare WO3 nanoplates. The crystal structure and morphology of WO3 were characterized by x-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and selected-area electron diffraction. The morphology of WO3 changed with an increase in calcining temperature. A mixed-potential NO x sensor using planar yttria-stabilized zirconia and WO3 as the sensing electrode (SE) was fabricated, and its performance in NO x detection at high temperature was examined. It was determined that at 500 °C, the sensor with the WO3-nanoplate SE had higher sensitivity to NO than the sensor with a SE consisting of WO3 microparticles. The response of the NO sensor with a WO3-nanoplate SE was linear with the logarithm of NO concentration in the range of 100-1000 ppm. The electrochemical impedance measurements indicate that the electrode reaction that occurred at the triple-phase boundary (TPB) of the sensor with WO3-nanoplate SE was stronger than the reaction that occurred at the TPB of the sensor with WO3-microparticle sensing electrode.

  3. 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.

  4. 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.

  5. Does mesoporosity enhance thin film properties? A question of electrode material for electrochromism of WO3

    NASA Astrophysics Data System (ADS)

    Ostermann, Rainer; Smarsly, Bernd

    2009-11-01

    Replacing the commonly used indium tin oxide (ITO) with a thin metal layer as a quasi-transparent electrode leads to enhancement and acceleration of the electrochromic response of WO3, as otherwise there is an electronic activation barrier at the interface between WO3 and the ITO electrode, impeding fast electron transfer.Replacing the commonly used indium tin oxide (ITO) with a thin metal layer as a quasi-transparent electrode leads to enhancement and acceleration of the electrochromic response of WO3, as otherwise there is an electronic activation barrier at the interface between WO3 and the ITO electrode, impeding fast electron transfer. Electronic supplementary information (ESI) available: Comparison of the variation of absorbance and charge inserted/extracted for WO3 films on gold and ITO. Electrochromic response of WO3 films of different thickness. See DOI: 10.1039/b9nr00091g

  6. Tailoring surface states in WO3 photoanodes for efficient photoelectrochemical water splitting

    NASA Astrophysics Data System (ADS)

    Singh, Trilok; Müller, Ralf; Singh, Jai; Mathur, Sanjay

    2015-08-01

    The dynamics of photo-induced charge carriers are significantly influenced by the surface states of WO3 thin films, which were synthesized by reactive sputtering of tungsten substrates in oxygen plasma. Tailoring the surface properties by (i) hydrogen plasma treatment and (ii) anchoring plasmonic nanoparticles (Au and Ag) altered the light harvesting and charge separation/transport processes of WO3 photoanodes. Upon hydrogen plasma-treatment and coating of noble metal clusters, WO3 films showed enhanced visible light absorption and consequently higher photocurrent density (1.4 mA cm-2) compared to pristine WO3 (0.2 mA cm-2). Enhancement in hydrogen treated WO3 sample was found to be due to the reduction of W(VI) into W(V) centers, which produced substoichiometric WO3-x phases, whereas noble metal particles contributed towards both resonant and non-resonant scattering of incident light thereby increasing photon-to-current conversion efficiency.

  7. Room temperature NO2-sensing properties of WO3 nanoparticles/porous silicon

    NASA Astrophysics Data System (ADS)

    Yan, Wenjun; Hu, Ming; Zeng, Peng; Ma, Shuangyun; Li, Mingda

    2014-02-01

    WO3 nanoparticles were synthesized by sol-gel method with tungsten hexachloride (WCl6) as precursor and deposited onto porous silicon and alumina substrates by dip-coating. The morphology and crystal structure of samples were investigated by means of field emission scanning electron microscope and X-ray diffractometer. It is the experimental results demonstrated by gas sensing tests that WO3 nanoparticles combining with the substrate of porous silicon presented an improved NO2-sensing property at room temperature. Compared to WO3 deposited on alumina working above 100 °C, the WO3 nanoparticles/porous silicon exhibited higher properties upon exposure to sub-ppm concentrations of NO2 gas at room temperature. Additionally, the NO2-sensing performance of WO3 nanoparticles/porous silicon was enhanced markedly, in comparison to pure porous silicon. The mechanism of WO3/porous silicon composite structure on the NO2 sensing was explained in detail.

  8. 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.

  9. Photocatalytic removal of microcystin-LR by advanced WO3-based nanoparticles under simulated solar light.

    PubMed

    Zhao, Chao; Li, Dawei; Liu, Yonggang; 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

  10. 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

  11. Enhanced photoelectrochemical and photocatalytic activity of WO3-surface modified TiO2 thin film.

    PubMed

    Qamar, Mohammad; Drmosh, Qasem; Ahmed, Muhammad I; Qamaruddin, Muhammad; Yamani, Zain H

    2015-01-01

    Development of nanostructured photocatalysts for harnessing solar energy in energy-efficient and environmentally benign way remains an important area of research. Pure and WO3-surface modified thin films of TiO2 were prepared by magnetron sputtering on indium tin oxide glass, and photoelectrochemical and photocatalytic activities of these films were studied. TiO2 particles were <50 nm, while deposited WO3 particles were <20 nm in size. An enhancement in the photocurrent was observed when the TiO2 surface was modified WO3 nanoparticles. Effect of potential, WO3 amount, and radiations of different wavelengths on the photoelectrochemical activity of TiO2 electrodes was investigated. Photocatalytic activity of TiO2 and WO3-modified TiO2 for the decolorization of methyl orange was tested. Graphical abstractWO3-surface modified TiO2 film showing better photocatalytic and photoelectrocatalytic activity. PMID:25852351

  12. Efficient electrochemical reaction in hexagonal WO 3 forests with a hierarchical nanostructure

    NASA Astrophysics Data System (ADS)

    Shibuya, Masachika; Miyauchi, Masahiro

    2009-04-01

    Nanotree-like hexagonal tungsten oxide (WO 3) arrays were grown on metal tungsten substrates by a facile hydrothermal method. The WO 3 nanotrees, composed of 'trunks' and 'branches', were single crystals oriented in the <0 0 1> direction. Nanotree thin films exhibited efficient electrochromism due to their large tunnels in the crystal and nano-channels between the nanotrees. Moreover, their coloration efficiency and reversibility were superior to polycrystalline WO 3 films.

  13. Facile preparation of aqueous suspensions of WO3/sulfonated PEDOT hybrid nanoparticles for electrochromic applications.

    PubMed

    Ling, Han; Ding, Guoqiang; Mandler, Daniel; Lee, Pooi See; Xu, Jianwei; Lu, Xuehong

    2016-08-01

    An aqueous suspension of WO3/poly(4-(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl-methoxy)-1-butanesulfonic acid) (PEDTS) hybrid nanoparticles (NPs) is prepared by air-assisted oxidative polymerization and simultaneous attachment of PEDTS on WO3-NPs, and used for electrochromic (EC) film fabrication via air-brush spraying. The hybrid EC device exhibits enhanced EC properties compared to the ones based on WO3-NP or PEDTS alone. PMID:27375222

  14. Mechanism of electrochromism for amorphous WO sub 3 thin films

    SciTech Connect

    Hashimoto, S.; Matsuoka, H. )

    1991-01-15

    The mechanism of electrochromism for an amorphous WO{sub 3} film has been studied. The film was prepared by using vacuum evaporation. X-ray phototelectron spectroscopy analysis has revealed that a state appears below the Fermi level after coloration in a LiClO{sub 4}-propylene carbonate electrolyte and that the Fermi level increases in proportion to the amount of injected lithium. In addition, a decrease in the density of state of the conduction band has been observed in a colored film by using electron energy loss spectroscopy analysis in transmission electron microscopy. It has been concluded that the electrons injected occupy the conduction band after coloration and that electrochromism of amorphous WO{sub 3} film is due to an intraband transition between an electron injected in the conduction band and an empty state.

  15. Phage WO of Wolbachia: lambda of the endosymbiont world

    PubMed Central

    Kent, Bethany N.; Bordenstein, Seth R.

    2010-01-01

    The discovery of an extraordinarily high level of mobile elements in the genome of Wolbachia, a widespread arthropod and nematode endosymbiont, suggests that this bacterium could be an excellent model for assessing the evolution and function of mobile DNA in specialized bacteria. Here, we discuss how studies on the temperate bacteriophage WO of Wolbachia have revealed unexpected levels of genomic flux and are challenging previously held views about the clonality of obligate intracellular bacteria. We also discuss the roles that this phage might play in the Wolbachia-arthropod symbiosis, and infer how this research can be translated to combating human diseases vectored by arthropods. We expect that this temperate phage will be a preeminent model system to understand phage genetics, evolution, and ecology in obligate intracellular bacteria. In this sense, phage WO might be likened to phage λ of the endosymbiont world. PMID:20083406

  16. 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).

  17. 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. PMID:27348055

  18. Enhanced NO2 Gas Sensing Properties of WO3-Coated Multiwall Carbon Nanotube Sensors.

    PubMed

    Ko, Hyunsung; Park, Sunghoon; Park, Suyoung; Lee, Chongmu

    2015-07-01

    WO3-coated multiwall carbon nanotubes (MWCNTs) were fabricated by sputter-deposition of WO3 on MWCNT paste. The outer diameters of WO3-coated MWCNTs ranged from 20 to 40 nm and the lengths ranged up to a few tens of micrometers. The low-magnification TEM image of a typical WO3-coated CNT showed a CNT with an inner diameter of ~20 nm and a tube wall thickness of ~7 nm and WO3 shells with a thickness up to 10 nm at both edges of the tube. The WO3 shells were very nonuniform in thickness not only along the axis of the nanotube but also from one nanotube to the other. The sensing properties of multiple networked WO3-coated CNT sensors toward NO2 gas were examined. The WO3-coated MWCNT sensors showed responses of 120-221% over an NO2 concentration range of 1 to 5 ppm at room temperature. The responses were 1-2 fold higher than those of the pristine MWCNT sensor over the same NO2 concentration range. The origin of the enhancement of the MWCNTs in the response to NO2 by coating them with WO3 is discussed. PMID:26373127

  19. 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}.

  20. 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.

  1. 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.

  2. Spontaneous and stimulated Raman scattering in ZnWO{sub 4} crystals

    SciTech Connect

    Basiev, Tasoltan T; Karasik, Aleksandr Ya; Sobol, A A; Chunaev, D S; Shukshin, V E

    2011-04-30

    Spontaneous and stimulated Raman scattering (SRS) are studied in ZnWO{sub 4} crystals with a wolframite structure. The polarised Raman scattering spectra corresponding to all the six independent Raman tensor components are measured. The frequencies of the complete set of vibrational modes are identified. The threshold pump energies for SRS in ZnWO{sub 4} and KGd(WO{sub 4}){sub 2} crystals are measured upon excitation by picosecond 1047-nm pulses of a Nd:YLF laser. The SRS gains for ZnWO{sub 4} crystals are determined based on the measured thresholds and spectroscopic parameters of the crystals. (nonlinear optics phenomena)

  3. WO3 nanotubes prepared by a coaxial electrospinning method.

    PubMed

    Cao, Xingxing; Zhang, Xuebin; Hu, Jixiang; Wang, Yang; Liu, Jia; Wu, Haijun; Feng, Yi

    2014-08-01

    In this paper, WO3 nanotubes were prepared by a coaxial electrospinning method. Firstly, core-shell structured composite fibers were fabricated via coaxial electrospinning under the optimal electro-spinning parameters to get the best composite fibers with uniform diameters and smooth surface, which pure PVA being the core solution and PVA/AMT/alcohol being the shell one, respectively. Secondly, the composite fibers were calcined in air at 600 °C for 4 h to wipe out the pure PVA, leading to the formation of nanotubes. After sintering, the obtained WO3 nanotubes were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). The XRD show that the resultant materials consist of pure tungsten trioxide (WO3) with good crystallinity, while FESEM and HRTEM images indicate that the materials are nanotubes with rough surface and consist of nanoparticles. The inner diameter and the wall thickness of nanotubes were calculated to be around 100 and 50 nm, respectively. PMID:25936119

  4. Size analysis of nanoparticles extracted from W/O emulsions.

    PubMed

    Nagelreiter, C; Kotisch, H; Heuser, T; Valenta, C

    2015-07-01

    Nanosized particles are frequently used in many different applications, especially TiO2 nanoparticles as physical filters in sunscreens to protect the skin from UV radiation. However, concerns have arisen about possible health issues caused by nanoparticles and therefore, the assessment of the occurrence of nanoparticles is important in pharmaceutical and cosmetic formulations. In a previous work of our group, a method was presented to extract nanoparticles from O/W emulsions. But to respond to the needs of dry and sensitive skin, sunscreens of the water-in-oil emulsion type are available. In these, assessment of present nanoparticles is also an important issue, so the present study offers a method for extracting nanoparticles from W/O emulsions. Both methods emanate from the same starting point, which minimizes both effort and cost before the beginning of the assessment. By addition of NaOH pellets and centrifugation, particles were extracted from W/O emulsions and measured for their size and surface area by laser diffraction. With the simple equation Q=A/S a distinction between nanoparticles and microparticles was achieved in W/O emulsions, even in commercially available samples. The present method is quick and easy to implement, which makes it cost-effective. PMID:25907509

  5. Electrochromism in sputtered WO{sub 3} thin films

    SciTech Connect

    Batchelor, R.A.; Burdis, M.S.; Siddle, J.R.

    1996-03-01

    There are large variations in the properties of WO{sub 3} sputtered under different conditions and two samples sputtered from an oxide target and reactively sputtered from a metal target were compared in detail. The thin film sputtered from an oxide target was found to color and bleach rapidly in 1 M LiClO{sub 4} in propylene carbonate, while the thin film reactively sputtered from a metal target could be colored deeply, but bleached only slowly. By calculating the rate of change of optical density during cyclic voltammetry, it was possible to directly compare the coloration response with the current/voltage behavior of the electrodes. In both cases at least two lithium insertion reactions appear to occur. The distinction between the two reactions was especially clear in the sample sputtered from a metal target, in which an insertion of high electrochromic efficiency occurred up to Li{sub 0.2}WO{sub 3} and then an insertion of considerably lower electrochromic efficiency up to Li{sub 0.5}WO{sub 3}. Although a small amount of coloration and bleaching continued to occur after switching the reactively sputtered sample to open circuit during the coloration and bleaching cycles; transmission change was largely halted by disconnecting the external current supply. The slow end to the bleach of the reactively sputtered sample corresponded to a reaction of high electrochromic efficiency.

  6. Evaluation of WO2013125543, WO2013146963 and EP2634185: the first Tyk2 inhibitors from Takeda and Sareum.

    PubMed

    Norman, Peter

    2014-03-01

    Three patent applications, from two different companies, claim structurally novel Tyk2 inhibitors and their uses for the treatment of autoimmune diseases. In EP-2634185 Sareum claims 5-anilino-2-(2-halophenyl)-oxazole-4-carboxamide derivatives which are shown to be nanomolar potency Tyk2 inhibitors with 10 - 100-fold selectivity over JAK1, JAK2 and JAK3. Takeda's WO-2013125543 and WO-2013146963 claim two distinct structural classes of Tyk2 inhibitors. The first application claims inhibitors based on an unusual 1,5-dihydro-4H-pyrazolo[4,3-c]pyridine-4-one scaffold and the second claims 1-(2-arylaminopyrimidin-4-yl)-pyrrolidin-2-one derivatives. One example of the latter was shown to be orally active in an IL-23-induced inflammation model. PMID:24386992

  7. Magnetic and structural properties of NaLnMnWO{sub 6} and NaLnMgWO{sub 6} perovskites

    SciTech Connect

    King, Graham; Wayman, Lora M.; Woodward, Patrick M.

    2009-06-15

    We have prepared 14 new AA'BB'O{sub 6} perovskites which possess a rock salt ordering of the B-site cations and a layered ordering of the A-site cations. The compositions obtained are NaLnMnWO{sub 6} (Ln=Ce, Pr, Sm, Gd, Dy, and Ho) and NaLnMgWO{sub 6} (Ln=Ce, Pr, Sm, Eu, Gd, Tb, Dy, and Ho). The samples were structurally characterized by powder X-ray diffraction which has revealed metrically tetragonal lattice parameters for compositions with Ln=Ce, Pr and monoclinic symmetry for compositions with smaller lanthanides. Magnetic susceptibility vs. temperature measurements have found that all six NaLnMnWO{sub 6} compounds undergo antiferromagnetic ordering at temperatures between 10 and 13 K. Several compounds show signs of a second magnetic phase transition. One sample, NaPrMnWO{sub 6}, appears to pass through at least three magnetic phase transitions within a narrow temperature range. All eight NaLnMgWO{sub 6} compounds remain paramagnetic down to 2 K revealing that the ordering of the Ln{sup 3+} cations in the NaLnMnWO{sub 6} compounds is induced by the ordering of the Mn{sup 2+} sub-lattice. - Graphical abstract: Evidence for multiple magnetic phase transitions in the A and B-site ordered perovskite NaPrMnWO{sub 6}.

  8. Novel WO3/Sb2S3 Heterojunction Photocatalyst Based on WO3 of Different Morphologies for Enhanced Efficiency in Photoelectrochemical Water Splitting.

    PubMed

    Zhang, Jing; Liu, Zhihua; Liu, Zhifeng

    2016-04-20

    We report the fabrication of tungsten trioxide (WO3) with different morphologies applied in photoelectrochemical (PEC) water splitting. The antimony sulfide (Sb2S3) was incorporated onto WO3 for the first time with the aim of improving its photoelectrocatalytic activity under visible-light illumination. In the present work, WO3 of different morphologies were fabricated on FTO glass via adjusting the pH value via a facile hydrothermal method and the morphological effect on the photoelectrocatalytic activity of the obtained samples has been discussed. WO3/Sb2S3 heterojunction photoelectrocatalysts were subsequently synthesized successfully to further improve the photoelectrocatalytic activity. Among them, WO3/Sb2S3 heterojunction photoelectrocatalyst based on WO3 micro crystals achieved an enhanced photocurrent of 1.79 mA/cm(2) at 0.8 V versus RHE under simulated sunlight, compared to 0.45 mA/cm(2) of pristine WO3 micro crystals. This excellent PEC performance benefits from the enhanced light absorbance, construction of suitable energy band gap, the improved photogenerated electron-hole pairs separation and transfer efficiency, which potentially provides new insights into PEC water splitting systems. PMID:27032422

  9. 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.

  10. 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.

  11. CdWO{sub 4} polymorphs: Selective preparation, electronic structures, and photocatalytic activities

    SciTech Connect

    Yan, Tingjiang; Li, Liping; Tong, Wenming; Zheng, Jing; Wang, Yunjian; Li, Guangshe

    2011-02-15

    This work explored the selective synthesis of polymorphs of CdWO{sub 4} in either tetragonal or monoclinic phase by optimizing the experimental parameters. Systematic characterization indicated that both polymorphs possessed similar spherical morphologies but different structural building blocks. Electronic structures calculations for both polymorphs demonstrated the same constructions of conduction band or valence band, while the conduction band widths of both polymorphs were quite different. Both CdWO{sub 4} polymorphs exhibited good photocatalytic activity for degradation of methyl orange under UV light irradiation. When comparing to some other well-known tungstate oxide materials, the photocatalytic activity was found to follow such a consequence, monoclinic CdWO{sub 4{approx}}monoclinic ZnWO{sub 4}>tetragonal CdWO{sub 4}>tetragonal CaWO{sub 4}. The specific photocatalytic activity of monoclinic CdWO{sub 4} was even higher than that of commercial TiO{sub 2} photocatalyst (Degussa P25). The increased activity from the tetragonal CdWO{sub 4} to the monoclinic was consistent with the trend of the decreased symmetry, and this could be explained in terms of the geometric structures and electronic structures for both polymorphs. -- Graphical abstract: Monoclinic CdWO{sub 4} exhibited a much higher photocatalytic activity than the tetragonal form owing to the lower symmetry, more distorted geometric structure, and the dispersive band configuration. Display Omitted Research highlights: > Polymorphs of CdWO{sub 4} in either tetragonal or monoclinic phase were selectively synthesized. > Both polymorphs possessed similar spherical morphologies, while the relevant structural building blocks were different. > Photocatalytic activities of CdWO{sub 4} polymorphs depended strongly on the symmetry, geometric structure, as well as band configuration.

  12. 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.

  13. Lithium-titanate-nanotube-supported WO3 for enhancing transmittance contrast in electrochromics.

    PubMed

    Dong, Yunbing; Xiong, Chunrong; Zhang, Yilu; Xing, Shuai; Jiang, Hong

    2016-03-11

    Lithium titanate nanotubes (Li-TNTs) have been successfully synthesized. The inner and outer diameters of the nanotubes are 5 nm and 8 nm with an interlayer spacing of 0.83 nm. The nanotubes were in accordance with the Li1.81H0.19Ti2O5 · xH2O phase. The chemical component was Li0.9H1.1Ti2O5 · H2O as determined by ICP-AES. The Li-TNT-supported WO3 nanoparticle (WO3/Li-TNTs) thin film was prepared onto ITO glass via spin-coating and then fabricated with an electrochromic device. The Li ion diffusion coefficient in the WO3/Li-TNT film was 6.1 × 10(-10) cm(2) s(-1), which is eight times higher than that for the pure WO3 film. The transmittance contrast of the pure WO3-based ECD was 53.3% at 600 nm. However, this increased to 74.1% for the WO3/Li-TNT-based ECD. Meanwhile, the color-switching times of the WO3/Li-TNT-based ECD were apparently shorter than the ones for the WO3-based ECD. PMID:26866352

  14. 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.

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

    PubMed

    Vemuri, R S; Engelhard, M H; Ramana, C V

    2012-03-01

    Nanocrystalline WO(3) 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 WO(3) 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 ultramicrostructure was significant on the optical properties of WO(3) films. The XPS analyses indicate the formation of stoichiometric WO(3) with tungsten existing in fully oxidized valence state (W(6+)). However, WO(3) films grown at high oxygen concentration (>60%) in the sputtering gas mixture were over stoichiometric with excess oxygen. XRR simulations based on isotropic WO(3) film-SiO(2) interface-Si substrate modeling indicate that the density of WO(3) films is sensitive to the oxygen content in the sputtering gas. The spectral transmission of the films increased with increasing oxygen. The band gap of these films increases from 2.78 to 3.25 eV with increasing oxygen. A direct correlation between the film density and band gap in nanocrystalline WO(3) films is established on the basis of the observed results. PMID:22332637

  16. 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.

  17. Lithium-titanate-nanotube-supported WO3 for enhancing transmittance contrast in electrochromics

    NASA Astrophysics Data System (ADS)

    Dong, Yunbing; Xiong, Chunrong; Zhang, Yilu; Xing, Shuai; Jiang, Hong

    2016-03-01

    Lithium titanate nanotubes (Li-TNTs) have been successfully synthesized. The inner and outer diameters of the nanotubes are 5 nm and 8 nm with an interlayer spacing of 0.83 nm. The nanotubes were in accordance with the Li1.81H0.19Ti2O5 · xH2O phase. The chemical component was Li0.9H1.1Ti2O5 · H2O as determined by ICP-AES. The Li-TNT-supported WO3 nanoparticle (WO3/Li-TNTs) thin film was prepared onto ITO glass via spin-coating and then fabricated with an electrochromic device. The Li ion diffusion coefficient in the WO3/Li-TNT film was 6.1 × 10-10 cm2 s-1, which is eight times higher than that for the pure WO3 film. The transmittance contrast of the pure WO3-based ECD was 53.3% at 600 nm. However, this increased to 74.1% for the WO3/Li-TNT-based ECD. Meanwhile, the color-switching times of the WO3/Li-TNT-based ECD were apparently shorter than the ones for the WO3-based ECD.

  18. 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…

  19. Influence of peculiarities of electronic excitation relaxation on luminescent properties of MgWO4

    NASA Astrophysics Data System (ADS)

    Krutyak, N. R.; Spassky, D. A.; Tupitsyna, I. A.; Dubovik, A. M.

    2016-07-01

    Luminescent properties of magnesium tungstate monocrystals grown by two different methods are studied. Only the exciton luminescence of these crystals themselves is observed. Temperature dependence of the low-energy range in the luminescence excitation spectra is described by the Urbach rule. Slope coefficient σ0 = 0.74 obtained from this dependence implies autolocalization of the excitons in MgWO4. The processes of electronic excitations relaxation are considered depending on the structure of valence band in MgWO4 and in other wolframites, ZnWO4 and CdWO4. In contrast to ZnWO4 and CdWO4, the d-states of the cation do not participate in formation of the MgWO4 valence band. Using the excitation spectra measured in the range of the fundamental absorption (4-20 eV), it is shown that this difference manifests itself in relaxation of electronic excitations and may be the cause of the relatively low light yield of MgWO4.

  20. Effect of Bisphenol A on invasion ability of human trophoblastic cell line BeWo

    PubMed Central

    Wang, Zi-Yi; Lu, Jing; Zhang, Yuan-Zhen; Zhang, Ming; Liu, Teng; Qu, Xin-Lan

    2015-01-01

    Bisphenol A (BPA) is a kind of environmental endocrine disruptors (EEDs) that interfere embryo implantation. Trophoblast invasion plays a crucial role during embryo implantation. In this study, the effects of BPA on invasion ability of human trophoblastic cell line BeWo and its possible mechanism were investigated. BeWo cells were exposed to BPA and co-cultured with human endometrial cells to mimic embryo implantation in transwell model. The proliferation and invasion capability of BeWo cells were detected. The expression of E-cadherin, DNMT1, MMP-2, MMP-9, TIMP-1 and TIMP-2 were also analyzed. The results showed that the invasion capability of BeWo was reduced after daily exposure to BPA. BPA had biphasic effect on E-cadherin expression level in BeWo cells and expression level of DNMT1 was decreased when treated with BPA. Moreover, BPA treatment also changed the balance of MMPs/TIMPs in BeWo cells by down-regulating MMP-2, MMP-9 and up-regulating TIMP-1, TIMP-2 with increasing BPA concentration. Taken together, these results showed that BPA treatment could reduce the invasion ability of BeWo cells and alter the expression level of E-cadherin, DNMT1, TIMP-1, TIMP-2, MMP-2, and MMP-9. Our study would help us to understand the possible mechanism of BPA effect on invasion ability of human trophoblastic cell line BeWo. PMID:26823751

  1. 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.

  2. 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.

  3. Enhanced photoelectrochemical and photocatalytic activity of WO3-surface modified TiO2 thin film

    NASA Astrophysics Data System (ADS)

    Qamar, Mohammad; Drmosh, Qasem; Ahmed, Muhammad I.; Qamaruddin, Muhammad; Yamani, Zain H.

    2015-02-01

    Development of nanostructured photocatalysts for harnessing solar energy in energy-efficient and environmentally benign way remains an important area of research. Pure and WO3-surface modified thin films of TiO2 were prepared by magnetron sputtering on indium tin oxide glass, and photoelectrochemical and photocatalytic activities of these films were studied. TiO2 particles were <50 nm, while deposited WO3 particles were <20 nm in size. An enhancement in the photocurrent was observed when the TiO2 surface was modified WO3 nanoparticles. Effect of potential, WO3 amount, and radiations of different wavelengths on the photoelectrochemical activity of TiO2 electrodes was investigated. Photocatalytic activity of TiO2 and WO3-modified TiO2 for the decolorization of methyl orange was tested.

  4. Ethanol sensing of SnO2-WO3 core/shell nanowires

    NASA Astrophysics Data System (ADS)

    Park, Sunghoon; Kim, Soohyun; Sun, Gun-Joo; Choi, Seung-Bok; Lee, Sangmin; Lee, Chongmu

    2015-09-01

    SnO2-WO3 core/shell nanowires were synthesized by the thermal evaporation of Sn powders in an oxidizing ambient followed by the thermal evaporation of WO3 powders. Their C2H5OH gas sensing properties were then examined. The C2H5OH gas sensing properties were improved remarkably by formation of the SnO2-WO3 heterostructures. The SnO2-WO3 core/shell nanowire sensors showed a much stronger and faster response to C2H5OH gas than the pristine SnO2-nanowire sensors. The enhanced sensing performance of the SnO2-WO3 core/shell nanowires towards C2H5OH gas can be accounted for by the potential barrier-controlled carrier-transport mechanism combined with the surface-depletion mechanism. [Figure not available: see fulltext.

  5. Electrochromic properties of WO3 thin film onto gold nanoparticles modified indium tin oxide electrodes

    NASA Astrophysics Data System (ADS)

    Deng, Jiajia; Gu, Ming; Di, Junwei

    2011-04-01

    Gold nanoparticles (GNPs) thin films, electrochemically deposited from hydrogen tetrachloroaurate onto transparent indium tin oxide (ITO) thin film coated glass, have different color prepared by variation of the deposition condition. The color of GNP film can vary from pale red to blue due to different particle size and their interaction. The characteristic of GNPs modified ITO electrodes was studied by UV-vis spectroscopy, scanning electron microscope (SEM) images and cyclic voltammetry. WO3 thin films were fabricated by sol-gel method onto the surface of GNPs modified electrode to form the WO3/GNPs composite films. The electrochromic properties of WO3/GNPs composite modified ITO electrode were investigated by UV-vis spectroscopy and cyclic voltammetry. It was found that the electrochromic performance of WO3/GNPs composite films was improved in comparison with a single component system of WO3.

  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. The enhanced alcohol-sensing response of ultrathin WO3 nanoplates

    NASA Astrophysics Data System (ADS)

    Chen, Deliang; Hou, Xianxiang; Wen, Hejing; Wang, Yu; Wang, Hailong; Li, Xinjian; Zhang, Rui; Lu, Hongxia; Xu, Hongliang; Guan, Shaokang; Sun, Jing; Gao, Lian

    2010-01-01

    Chemical sensors based on semiconducting metal oxide nanocrystals are of academic and practical significance in industrial processing and environment-related applications. Novel alcohol response sensors using two-dimensional WO3 nanoplates as active elements have been investigated in this paper. Single-crystalline WO3 nanoplates were synthesized through a topochemical approach on the basis of intercalation chemistry (Chen et al 2008 Small 4 1813). The as-obtained WO3 nanoplate pastes were coated on the surface of an Al2O3 ceramic microtube with four Pt electrodes to measure their alcohol-sensing properties. The results show that the WO3 nanoplate sensors are highly sensitive to alcohols (e.g., methanol, ethanol, isopropanol and butanol) at moderate operating temperatures (260-360 °C). For butanol, the WO3 nanoplate sensors have a sensitivity of 31 at 2 ppm and 161 at 100 ppm, operating at 300 °C. For other alcohols, WO3 nanoplate sensors also show high sensitivities: 33 for methanol at 300 ppm, 70 for ethanol at 200 ppm, and 75 for isopropanol at 200 ppm. The response and recovery times of the WO3 nanoplate sensors are less than 15 s for all the test alcohols. A good linear relationship between the sensitivity and alcohol concentrations has been observed in the range of 2-300 ppm, whereas the WO3 nanoparticle sensors have not shown such a linear relationship. The sensitivities of the WO3 nanoplate sensors decrease and their response times become short when the operating temperatures increase. The enhanced alcohol-sensing performance could be attributed to the ultrathin platelike morphology, the high crystallinity and the loosely assembling structure of the WO3 nanoplates, due to the advantages of the effective adsorption and rapid diffusion of the alcohol molecules.

  8. Catalytic activities of noble metal atoms on WO3 (001): nitric oxide adsorption.

    PubMed

    Ren, Xiaoyan; Zhang, Shuai; Li, Chong; Li, Shunfang; Jia, Yu; Cho, Jun-Hyung

    2015-01-01

    Using first-principles density functional theory calculations within the generalized gradient approximation, we investigate the adsorption of NO molecule on a clean WO3(001) surface as well as on the noble metal atom (Cu, Ag, and Au)-deposited WO3(001) surfaces. We find that on a clean WO3 (001) surface, the NO molecule binds to the W atom with an adsorption energy (E ads) of -0.48 eV. On the Cu- and Ag-deposited WO3(001) surface where such noble metal atoms prefer to adsorb on the hollow site, the NO molecule also binds to the W atom with E ads = -1.69 and -1.41 eV, respectively. This relatively stronger bonding of NO to the W atom is found to be associated with the larger charge transfer of 0.43 e (Cu) and 0.33 e (Ag) from the surface to adsorbed NO. However, unlike the cases of Cu-WO3(001) and Ag-WO3(001), Au atoms prefer to adsorb on the top of W atom. On such an Au-WO3(001) complex, the NO molecule is found to form a bond to the Au atom with E ads = -1.32 eV. Because of a large electronegativity of Au atom, the adsorbed NO molecule captures the less electrons (0.04 e) from the surface compared to the Cu and Ag catalysts. Our findings not only provide useful information about the NO adsorption on a clean WO3(001) surface as well as on the noble metal atoms deposited WO3(001) surfaces but also shed light on a higher sensitive WO3 sensor for NO detection employing noble metal catalysts. PMID:25852357

  9. Epitaxial growth of high quality WO3 thin films

    NASA Astrophysics Data System (ADS)

    Leng, X.; Pereiro, J.; Strle, J.; Bollinger, A. T.; Božović, I.

    2015-09-01

    We have grown epitaxial WO3 films on various single-crystal substrates using radio frequency magnetron sputtering. While pronounced surface roughness is observed in films grown on LaSrAlO4 substrates, films grown on Y AlO3 substrates show atomically flat surfaces, as demonstrated by atomic force microscopy and X-ray diffraction (XRD) measurements. The crystalline structure has been confirmed to be monoclinic by symmetric and skew-symmetric XRD. The dependence of the growth modes and the surface morphology on the lattice mismatch are discussed.

  10. Revival of "dead" memristive devices: case of WO3-x.

    PubMed

    Tan, Zheng-Hua; Yang, Rui; Terabe, Kazuya; Yin, Xue-Bing; Guo, Xin

    2016-01-21

    Inappropriate operation could make a memristive device "dead" and cause the loss of resistive switching performance. In this study, the revival of "dead" devices was investigated in the case of WO3-x-based memristive devices. It is believed that inappropriate operation with a high-voltage pulse creates an ordered structure of oxygen vacancies and such an ordered structure makes the normal reset process fail. By precisely controlled voltage sweeping at certain compliance currents, a "dead" device can be revived. The revival operation disrupts the ordered structure by Joule heating and recovers Schottky-like barrier modulation-based switching. PMID:26685986

  11. Electrochromism with colloidal WO3 and IrO2

    NASA Astrophysics Data System (ADS)

    Michalak, Franck; Rault, L.; Aldebert, Pierre

    1992-11-01

    Colloidal particles of WO3 and IrO2 are synthesized and dispersed within a gelatinous perfluorinated ionomer matrix. Experimental procedures are established in order to obtain percolation between the electrochromic particles. Colloidal particle sizes are measured by quasi elastic light scattering. Electrochemical properties of the mixed colloid electrodes are determined by cyclic voltammetry and impedance spectroscopy. Preliminary optical tests are performed in order to measure transmission and contrast of electrochromic half cells with a mixed colloid electrode, and also a sputtered oxide electrode.

  12. Epitaxial growth of high quality WO3 thin films

    DOE PAGESBeta

    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.

  13. 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.

  14. 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. PMID:27450332

  15. 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

  16. 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. PMID:18992799

  17. Tungsten oxide (WO{sub 3}) thin films for application in advanced energy systems

    SciTech Connect

    Gullapalli, S. K.; Vemuri, R. S.; Manciu, F. S.; Enriquez, J. L.; Ramana, C. V.

    2010-07-15

    Inherent processes in coal gasification plants produce hazardous hydrogen sulfide (H{sub 2}S), which must be continuously and efficiently detected and removed before the fuel is used for power generation. An attempt has been made in this work to fabricate tungsten oxide (WO{sub 3}) thin films by radio-frequency reactive magnetron-sputter deposition. The impetus being the use of WO{sub 3} films for H{sub 2}S sensors in coal gasification plants. The effect of growth temperature, which is varied in the range of 30-500 deg. C, on the growth and microstructure of WO{sub 3} thin films is investigated. Characterizations made using scanning electron microscopy (SEM) and x-ray diffraction (XRD) indicate that the effect of temperature is significant on the microstructure of WO{sub 3} films. XRD and SEM results indicate that the WO{sub 3} films grown at room temperature are amorphous, whereas films grown at higher temperatures are nanocrystalline. The average grain-size increases with increasing temperature. WO{sub 3} films exhibit smooth morphology at growth temperatures {<=}300 deg. C while relatively rough at >300 deg. C. The analyses indicate that the nanocrystalline WO{sub 3} films grown at 100-300 deg. C could be the potential candidates for H{sub 2}S sensor development for application in coal gasification systems.

  18. Investigation of the optical property and structure of WO3 thin films with different sputtering depositions

    NASA Astrophysics Data System (ADS)

    Chen, Hsi-Chao; Jan, Der-Jun; Chen, Chien-Han; Huang, Kuo-Ting; Lo, Yen-Ming; Chen, Sheng-Hui

    2011-09-01

    The purpose of this research was to compare the optical properties and structure of tungsten oxide (WO3) thin films that was deposited by different sputtering depositions. WO3 thin films deposited by two different depositions of direct current (DC) magnetron sputtering and pulsed DC sputtering. A 99.95% WO3 target was used as the starting material for these depositions. These WO3 thin films were deposited on the ITO glass, PET and silicon substrate by different ratios of oxygen and argon. A shadow moiré interferometer would be introduced to measure the residual stress for PET substrate. RF magnetron sputtering had the large residual stress than the other's depositions. A Raman spectrum could exhibit the phase of oxidation of WO3 thin film by different depositions. At the ratio of oxygen and argon was about 1:1, and the WO3 thin films had the best oxidation. However, it was important at the change of the transmittance (ΔT = Tbleached - Tcolored) between the coloring and bleaching for the smart window. Therefore, we also found the WO3 thin films had the large variation of transmittance between the coloring and bleaching at the gas ratios of oxygen and argon of 1:1.

  19. High-Tc superconductivity in nanostructured NaxWO3-y: Sol-gel route

    NASA Astrophysics Data System (ADS)

    Aliev, Ali

    2009-03-01

    Tungsten trioxide, WO3-y infiltrated into various nanoporous matrix structures such as carbon inverse opal, carbon nanotubes paper, or platinum sponge and then intercalated with alkaline ions (Li^+, Na^+) exhibits a pronounced diamagnetic onset in ZFC magnetization in a wide range of temperatures, 125-132 K. Resistivity measurements show non zero jump and intensive fluctuations of electrical resistance below observed transition points. The observed magnetic and electrical anomalies in nanostructured tungsten bronzes (LixWO3-y, NaxWO3-y) suggest the possibility of localized non-percolated superconductivity. The direct evidence of polaron formation from temperature dependence of EPR and photoemission spectra and formation of bipolarons in weakly reduced to WO3-y, with 3-y typically in the order of 2.95 suggest bipolarons mechanism of a Bose-Einstein condensation of trapped electron pairs in doped WO3-y. On the other hand the strong lattice instabilities in 2D systems like layered cuprates and tungsten bronzes place the upper limit on Tc. Than, the percolative self-organized mechanism on the metal/insulator interface like Na/WO3 and NaWO3/nanostructured matrix can facilitate the high Tc obtained in sodium bronzes infiltrated into inverted carbon opal or carbon nanotube matricies.

  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. A poly(3,4-ethylenedioxypyrrole)-Au@WO3 -based electrochromic pseudocapacitor.

    PubMed

    Reddy, B Narsimha; Kumar, P Naresh; Deepa, Melepurath

    2015-02-01

    A poly(3,4-ethylenedioxypyrrole)-gold nanoparticle (Au)-tungsten oxide (PEDOP-Au@WO3 ) electrochromic supercapacitor electrode capable of optically modulating solar energy while simultaneously storing/releasing energy (in the form of charge) was fabricated for the first time. WO3 fibers, 50 to 200 nm long and 20 to 60 nm wide, were synthesized by a hydrothermal route and were electrophoretically deposited on a conducting substrate. Au nanoparticles and PEDOP were coated over WO3 to yield the PEDOP-Au@WO3 hybrid electrode. The inclusion of Au in the hybrid was confirmed by X-ray diffraction, Raman spectroscopy, and energy-dispersive X-ray analyses. The nanoscale electronic conductivity, coloration efficiency, and transmission contrast of the hybrid were found to be significantly greater than those of pristine WO3 and PEDOP. The hybrid showed a high specific discharge capacitance of 130 F g(-1) during coloration, which was four and ten times greater than the capacitance achieved in WO3 or PEDOP, respectively. We also demonstrate the ability of the PEDOP-Au@WO3 hybrid, relative to pristine PEDOP, to perform as a superior counter electrode in a solar cell, which is attributed to a higher work function. The capacitance and redox switching capability of the hybrid decreases insignificantly with cycling, thus establishing the viability of this multifunction hybrid for next-generation sustainable devices such as electrochromic psuedocapacitors because it can concurrently conserve and store energy. PMID:25371375

  2. Highly active WO3-Ag-ZnO photocatalyst driven by day light illumination

    NASA Astrophysics Data System (ADS)

    Subash, B.; Krishnakumar, B.; Sreedhar, B.; Swaminathan, M.; Shanthi, M.

    2013-02-01

    The WO3 loaded Ag-ZnO (WO3-Ag-ZnO) was successfully synthesized by precipitation-decomposition method. The catalyst was characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) images, energy dispersive spectrum (EDS), transmission electron microscope (TEM), diffuse reflectance spectra (DRS), photoluminescence spectra (PL), cyclic voltammetry (CV) and BET surface area measurements. The photocatalytic activity of WO3-Ag-ZnO was investigated for the degradation of Naphthol Blue Black (NBB) in aqueous solution using solar light. WO3-Ag-ZnO is found to be more efficient than Ag-ZnO, WO3-ZnO, Ag-WO3, WO3, commercial ZnO, bare ZnO, TiO2-P25 and TiO2 (Merck) at pH 9 for the mineralization of NBB dye. The effects of operational parameters such as the amount of photocatalyst, dye concentration, initial pH on photo mineralization of NBB dye have been analyzed. The mineralization of NBB has been confirmed by Chemical Oxygen Demand (COD) measurements. A degradation mechanism is proposed for the degradation of NBB under solar light. This catalyst is found to be reusable.

  3. WO3 nanorolls self-assembled as thin films by hydrothermal synthesis

    NASA Astrophysics Data System (ADS)

    Vankova, S.; Zanarini, S.; Amici, J.; Cámara, F.; Arletti, R.; Bodoardo, S.; Penazzi, N.

    2015-04-01

    We report a novel type of WO3 nanostructure, i.e. nanorolls obtained as a self-assembled thin film on a transparent conductive substrate. The mild conditions of preparation, avoiding the use of HCl, result in an eco-friendly hydrothermal method with reduced crystallization time. FESEM and HR-TEM show that WO3 nanocrystals are made of rolled nanoflakes with a telescope-like appearance at their tip. For their nano-porosity, electrochemical accessibility, good adhesion to substrates and the envisaged presence of nanocavities between the WO3 layers, these materials hold tremendous promise in nano-electronics, electrochromic devices, water photo-splitting cells, Li-ion batteries and nano-templated filters for UV radiation.We report a novel type of WO3 nanostructure, i.e. nanorolls obtained as a self-assembled thin film on a transparent conductive substrate. The mild conditions of preparation, avoiding the use of HCl, result in an eco-friendly hydrothermal method with reduced crystallization time. FESEM and HR-TEM show that WO3 nanocrystals are made of rolled nanoflakes with a telescope-like appearance at their tip. For their nano-porosity, electrochemical accessibility, good adhesion to substrates and the envisaged presence of nanocavities between the WO3 layers, these materials hold tremendous promise in nano-electronics, electrochromic devices, water photo-splitting cells, Li-ion batteries and nano-templated filters for UV radiation. Electronic supplementary information (ESI) available: Characterization techniques; additional FESEM micrographs; typical XRD pattern of WO3 nanoroll thin film; typical Nyquist plots at ambient temperature; indicative diameter and length of WO3 NR by varying the PVA chain length; effect of 2000 cycles of electrochemical switching on the STB, STC and ΔT% coloration efficiency of the WO3 NR. See DOI: 10.1039/c4nr07290a

  4. Facile synthesis of porous Bi2WO6 nanosheets with high photocatalytic performance.

    PubMed

    Sun, Qi; Jia, Xiangrui; Wang, Xuefei; Yu, Huogen; Yu, Jiaguo

    2015-08-28

    Compared with the well-known three-dimensional Bi2WO6 nanosheet-assembled nanostructures, the free-standing two-dimensional porous Bi2WO6 nanosheets have seldom been reported. The possible reason is that Bi2WO6 nanosheets with a high surface-to-volume ratio usually tend to self-assemble or aggregate to form microspheres to reduce their surface energy. To prevent their aggregation, in this study, a new and facile self-assembled route, which includes the in situ ion-exchange reaction of Na2WO4 solution with the Bi(NO3)3 solid powder and the following high-temperature calcination, has been successfully developed to prepare the free-standing porous Bi2WO6 nanosheets. The ion-exchange reaction between the Bi(NO3)3 solid and Na2WO4 solution can in situ produce amorphous Bi2WO6 nanosheets, while the high-temperature calcination (500 °C) causes the formation of homogeneously porous structures in individual nanosheets during their phase transformation from amorphous to crystalline. The resultant porous nanosheets are composed of one-layer Bi2WO6 nanoparticles with a size of 30-50 nm, and there is a strong coupling interface among these nanoparticles. Photocatalytic experimental results suggest that the resultant porous Pt/Bi2WO6 nanosheets show a high photocatalytic performance for the decomposition of phenol solution. Considering their facile preparation, the present synthetic route may provide new insights for the design and fabrication of other nanostructured materials with various potential applications. PMID:26212384

  5. 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.

  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. 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.

  8. Electrochemical lithium insertion in the solid solution Bi{sub 2}WO{sub 6}-Sb{sub 2}WO{sub 6} with Aurivillius framework

    SciTech Connect

    Martinez-de la Cruz, A. Longoria Rodriguez, F.E.

    2007-10-02

    Following the structural evolution of the Aurivillius crystalline framework in the solid solution Bi{sub 2}WO{sub 6}-Sb{sub 2}WO{sub 6} we have carried out an electrochemical lithium insertion study in this system. A slight loss of the specific capacity of the electrochemical cell was observed as amount of Sb was increased. In general, the different compositions within solid solution Bi{sub 2-x}Sb{sub x}WO{sub 6} (0.25 {<=} x {<=} 0.75) exhibited a similar behaviour featured mainly by two semiconstant potential regions located at 1.7 and 0.8 V versus Li{sup +}/Li{sup o}. The oxide Sb{sub 2}WO{sub 6} with Autivillius structure but without Bi was tested as cathode too. The maximum amount of lithium inserted, 13.5 lithium atoms per formula, is the same amount inserted in its homologous bismuth oxide Bi{sub 2}WO{sub 6}.

  9. Magnetic structure of Sr2CuWO6.

    PubMed

    Vasala, S; Avdeev, M; Danilkin, S; Chmaissem, O; Karppinen, M

    2014-12-10

    Magnetic structure of the double perovskite Sr2CuWO6 was determined from neutron powder diffraction data. At 3 K the material is magnetically long-range ordered into a collinear antiferromagnetic structure described by a propagation vector k = (0, 1/2, 1/2) with the Cu(II) moments of 0.57(1) μB parallel to the a-axis. The result is in agreement with our previous prediction (Vasala et al 2014 Phys. Rev. B 89 134419) based on electronic structure calculations, showing that the three-dimensional magnetic long-range order is caused by relatively strong antiferromagnetic next-nearest-neighbor interactions. PMID:25390820

  10. Characterization of Nanoporous WO3 Films Grown via Ballistic Deposition

    SciTech Connect

    Smid, Bretislav; Li, Zhenjun; Dohnalkova, Alice; Arey, Bruce W.; Smith, R. Scott; Matolin, Vladimir; Kay, Bruce D.; Dohnalek, Zdenek

    2012-05-17

    We report on the preparation and characterization of high surface area, supported nanoporous tungsten oxide films prepared under different conditions on polished polycrystalline Ta and Pt(111) substrates via direct sublimation of monodispersed gas phase of cyclic (WO3)3 clusters. Scanning Electron Microscopy and Transmission Electron Microscopy were used to investigate the film morphology on a nanometer scale. The films consist of arrays of separated filaments that are amorphous. The chemical composition and the thermal stability of the films were investigated by means of X-ray Photoelectron Spectroscopy. The surface area and the distribution of binding sites on the films are measured as functions of growth temperature, deposition angle, and annealing conditions using temperature programmed desorption of Kr. Films deposited at 20 K and at an incident angle of 65{sup o} from substrate normal display the greatest specific surface area of {approx}560 m2/g.

  11. Bi-functional Mo-doped WO3 nanowire array electrochromism-plus electrochemical energy storage.

    PubMed

    Zhou, D; Shi, F; Xie, D; Wang, D H; Xia, X H; Wang, X L; Gu, C D; Tu, J P

    2016-03-01

    Metal-doping is considered to be an effective way for construction of advanced semiconducting metal oxides with tailored physicochemical properties. Herein, Mo-doped WO3 nanowire arrays are rationally fabricated by a sulfate-assisted hydrothermal method. Compared to the pure WO3, the optimized Mo-doped WO3 nanowire arrays exhibit improved electrochromic properties with fast switching speed (3.2s and 2.6s for coloration and bleaching, respectively), significant optical modulation (56.7% at 750nm, 83.0% at 1600nm and 48.5% at 10μm), high coloration efficiency (123.5cm(2)C(-1)) and excellent cycling stability. In addition, as a proof of concept, the Mo-doped WO3 nanowire arrays are demonstrated with electrochemical energy storage monitored by the electrochromism. This electrode design protocol can provide an alternative way for developing high-performance active materials for bi-functional electrochromic batteries. PMID:26669497

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

    PubMed

    Reyes-Gil, Karla R; Stephens, Zachary D; Stavila, Vitalie; Robinson, David B

    2015-02-01

    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. 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. PMID:25562778

  13. Electrochemical properties of magnetron sputtered WO{sub 3} thin films

    SciTech Connect

    Madhavi, V.; Kondaiah, P.; Hussain, O. M.; Uthanna, S.

    2013-02-05

    Thin films of tungsten oxide (WO{sub 3}) were deposited on ITO substrates by using RF magnetron sputtering at oxygen and argon atmospheres of 6 Multiplication-Sign 10{sup -2}Pa and 4 Pa respectively. The chemical composition and surface morphology of the WO{sub 3} thin films have been studied by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) respectively. The results indicate that the deposited WO{sub 3} thin films are nearly stoichiometric. The electrochemical performances of the WO{sub 3} thin films have been evaluated by galvonostatic charging/discharging method. The discharge capacity was 15{mu}Ah/cm{sup 2}{mu}m at the initial cycle and faded rapidly in the first few cycles and stabilized at a lesser stage.

  14. Eliminating degradation and uncovering ion-trapping dynamics in electrochromic WO3 thin films

    NASA Astrophysics Data System (ADS)

    Wen, Rui-Tao; Granqvist, Claes G.; Niklasson, Gunnar A.

    2015-10-01

    There is keen interest in the use of amorphous WO3 thin films as cathodic electrodes in transmittance-modulating electrochromic devices. However, these films suffer from ion-trapping-induced degradation of optical modulation and reversibility on extended Li+-ion exchange. Here, we demonstrate that ion-trapping-induced degradation, which is commonly believed to be irreversible, can be successfully eliminated by constant-current-driven de-trapping; that is, WO3 films can be rejuvenated and regain their initial highly reversible electrochromic performance. Pronounced ion trapping occurs when x exceeds ~0.65 in LixWO3 during ion insertion. We find two main kinds of Li+-ion-trapping site (intermediate and deep) in WO3, where the intermediate ones are most prevalent. Li+ ions can be completely removed from intermediate traps but are irreversibly bound in deep traps. Our results provide a general framework for developing and designing superior electrochromic materials and devices.

  15. Synchrotron and laser excitation of luminescence in PbWO4:Tb crystals at different temperatures

    NASA Astrophysics Data System (ADS)

    Novosad, S. S.; Kostyk, L. V.; Novosad, I. S.

    2011-09-01

    The effect of temperature on the spectral luminescence characteristics of PbWO4:Tb3+ crystals with synchrotron and laser excitation is studied. If PbWO4:Tb3+ is excited by synchrotron radiation with λ = 88 nm at 300 K, a faint recombination luminescence of the impurity terbium is observed against the matrix luminescence. When the temperature is reduced to 8 K, the luminescence intensity of PbWO4:Tb3+ increases by roughly an order of magnitude and the characteristic luminescence of the unactivated crystal is observed. Excitation of PbWO4:Tb3+ by a nitrogen laser at 300 K leads to the appearance of emission from Tb3+ ions. At 90 K, a faint matrix luminescence is observed in addition to the activator emission. The formation of the luminescence excitation spectra for wavelengths of 60-320 nm is analyzed and the nature of the emission bands is discussed.

  16. Eliminating degradation and uncovering ion-trapping dynamics in electrochromic WO3 thin films

    PubMed Central

    Wen, Rui-Tao; Granqvist, Claes G.; Niklasson, Gunnar A.

    2015-01-01

    Amorphous WO3 thin films are of keen interest as cathodic electrodes in transmittance-modulating electrochromic devices. However, these films suffer from ion-trapping-induced degradation of optical modulation and reversibility upon extended Li+-ion exchange. Here, we demonstrate that ion-trapping-induced degradation, which is commonly believed to be irreversible, can be successfully eliminated by constant-current-driven de-trapping, i.e., WO3 films can be rejuvenated and regain their initial highly reversible electrochromic performance. Pronounced ion-trapping occurs when x exceeds ~0.65 in LixWO3 during ion insertion. We find two main kinds of Li+-ion trapping sites (intermediate and deep) in WO3, where the intermediate ones are most prevalent. Li+-ions can be completely removed from intermediate traps but are irreversibly bound in deep traps. Our results provide a general framework for developing and designing superior electrochromic materials and devices. PMID:26259104

  17. SUPERCRITICAL SOLVOTHERMAL SYNTHESIS AND NEAR-INFRARED ABSORBING PROPERTIES OF CsxWO3

    NASA Astrophysics Data System (ADS)

    Guo, Chongshen; Yin, Shu; Huang, Yunfang; Dong, Qiang; Li, Huihui; Sato, Tsugio

    2012-06-01

    CsxWO3 nanoparticles in the range of 20-50 nm have been successfully synthesized by the supercritical solvothermal approach, where after dissolving WCl6 and CsOH in a mixed solution of water, ethanol and oleic acid, the solution was heated at 300°C. The products were characterized by X-ray diffraction, TEM, HR-TEM, EDS, laser particle size analysis and thermographic measurements. CsxWO3 nanoparticles showed the high transparency in the visible region, excellent shielding performance of the near-infrared light and limited reflectance of light in the range of 200-2700 nm, indicating the strong absorption of NIR light on the nanosized CsxWO3. CsxWO3 nanoparticles also exhibited quick conversion of photo-energy to local heat.

  18. Strong aggregation adsorption of methylene blue from water using amorphous WO3 nanosheets

    NASA Astrophysics Data System (ADS)

    Luo, Jian Yi; Cao, Zhi; Chen, Feng; Li, Li; Lin, Yu Rong; Liang, Bao Wen; Zeng, Qing Guang; Zhang, Mei; He, Xin; Li, Chen

    2013-12-01

    In this paper, authors demonstrate the high performance of the amorphous WO3 nanosheets in the removal of methylene blue (MB) from water. The saturated MB adsorbed amount by using WO3 nanosheets as an adsorbent can reach to 600 mg/g, exceeding the ones of the normal activated carbon powders. Results indicate that the aggregation of adsorbed MB molecules occurs in the porous micro-structures of the amorphous WO3 nanosheets, and a precipitation phenomenon begins to happen when the initial MB concentration reach to 20 mg/L or greater, attributed to the density increase of WO3 nanosheets after their porous micro-structures are adsorbed with enough MB molecules.

  19. Investigations On Stoichiometry And Melting Behavior Of NaY(WO{sub 4}){sub 2}

    SciTech Connect

    Salunke, R. G.; Gosavi, S. W.; Singh, S. G.; Singh, A. K.; Desai, D. G.; Chauhan, A. K.; Gadkari, S. C.

    2010-12-01

    Differential thermal analysis (DTA) and X-ray diffraction (XRD) studies were carried out to understand the melting behavior of the NaY(WO{sub 4}){sub 2}, an important functional material used for the laser production. It has been observed that the stoichiometric NaY(WO{sub 4}){sub 2} composition forms a solution with another phase of the Na{sub 2}WO{sub 4}-Y{sub 2}(WO{sub 4}){sub 3} pseudo-binary system. This is found to be detrimental for the growth of single crystals of the material. Therefore, molar fraction in the starting charge was suitably altered to successfully restrict the formation of the undesired phase in the melt. A composition is suggested for the favorable crystal growth of this material.

  20. 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.

  1. Enhancement of the photocatalytic efficiency of WO3 nanoparticles via hydrogen plasma treatment

    NASA Astrophysics Data System (ADS)

    Rahimnejad, Sara; He, Jing Hui; Pan, Feng; Lee, Xue'er; Chen, Wei; Wu, Kai; Xu, Guo Qin

    2014-12-01

    Surface defect engineering is able to effectively enhance the photocatalytic performance of WO3 nanoparticles. In this paper, radio frequency hydrogen plasma was employed to create surface defects on WO3 nanoparticles. X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) analysis confirmed that hydrogen plasma modification increases the density of oxygen vacancies on the surface of WO3. The broadening of characteristic WO3 peaks in Raman spectra indicates the increase of oxygen vacancies by increasing voltage in hydrogen plasma treatment. The sample treated with hydrogen plasma at 20 volts shows enhancement in photocurrent density by an order of magnitude, attributable to the band-gap narrowing and subsequent increase of quantum yield in the visible range. Consistent results were also obtained from photocatalytic O2 evolution from water oxidation.

  2. Composition control of InN/WO3 nanocomposite by in-situ reactive plasma annealing

    NASA Astrophysics Data System (ADS)

    Saroni, Azianty; Goh, Boon Tong; Alizadeh, Mahdi; Rahman, Saadah Abdul

    2016-05-01

    A composition control and formation of InN/WO3 nanocomposite on the as-grown In2O3 by in-situ reactive plasma annealing was investigated. The reactive plasma annealing changes the facets crystalline In2O3 structure to nanograin structure of InN/WO3 nanocomposite with the grain size of 100-200 nm. X-ray photoelectron spectroscopy (XPS) reveals the formation of In2O3, InN and WO3 nanostructures in the nanocomposite. In-situ reactive plasma annealing enhances the removing of In2O3 and facilitates the formation of InN/WO3 nanocomposite. Furthermore, the reduction of oxygen in In2O3 leads to a decreasing in optical energy gap from 2.91 to 2.63 eV.

  3. 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. PMID:18439012

  4. Effect of Trace Fe3+ on Luminescent Properties of CaWO4: Pr3+ Phosphors

    NASA Astrophysics Data System (ADS)

    Wang, Ke; Feng, Xu; Feng, Wenlin; Shi, Shasha; Li, Yao; Zhang, Chao

    2016-01-01

    Fe3+ undoped and doped CaWO4: Pr3+ phosphors have been successfully synthesised by using the solid-state reaction method. The products were characterised by powder X-ray diffraction (XRD), photoluminescence (PL) and fluorescence lifetime testing techniques, respectively. The mean crystallite size (50.7 nm) of CaWO4: Pr3+ is obtained from powder XRD data. PL spectra of both Fe3+ undoped and doped CaWO4: Pr3+ phosphors exhibit excitation peaks at 214, 449, 474, and 487 nm under monitor wavelength at 651 nm, and emission peaks at 532, 558, 605, 621, 651, 691, 712, and 736 nm under blue light (λem=487 nm) excitation. The effect of trace Fe3+ on luminescence properties of CaWO4: Pr3+ phosphor is studied by controlling the doping concentration of Fe3+. The results show that radioactive energy transfers from luminescence centre Pr3+ to quenching centre Fe3+ occurred in Fe3+ doped CaWO4: Pr3+ phosphors. With the increasing concentration of Fe3+, the energy transfer from Pr3+ to Fe3+ is enhanced, and the emission intensity of CaWO4: Pr3+ will be lower. The decay times (5.22 and 4.99 μs) are obtained for typical samples Ca0.995WO4: Pr3+0.005 and Ca0.99275WO4: Pr3+0.005, Fe3+0.00225, respectively. This work shows that nonferrous phosphors can improve the luminescent intensity of the phosphors.

  5. The novel phase transition of NaBi(WO{sub 4}){sub 2} under high pressure

    SciTech Connect

    Ma, Chunli; Cui, Hang; Li, Fangfei; Wang, Jingshu; Wu, Xiaoxin; Zhang, Jian; Zhou, Qiang; Liu, Jinghe; Cui, Qiliang

    2013-04-15

    The Raman and synchrotron angle-dispersive X-ray diffraction studies have been performed on NaBi(WO{sub 4}){sub 2} under high pressure up to 30.7 and 36.2 GPa, respectively, at room temperature. With pressure increases to ∼7.0 GPa, the structure of NaBi(WO{sub 4}){sub 2} begins to transform from tetragonal (I4{sub 1}/a) into monoclinic (P2/m), and the phase transition completes around 13 GPa. With pressure higher than 29.0 GPa, the NaBi(WO{sub 4}){sub 2} turns into amorphous state. The random arrangement of Na{sup +} and Bi{sup 3+} in short-range ordered scheelite NaBi(WO{sub 4}){sub 2} results in the tetragonal to monoclinic phase transition, which is different from that observed in AWO{sub 4} tungstates and AMoO{sub 4} molybdates (A=Ca, Sr, Ba, Pb, Eu, Cd). - Graphical abstract: The NaBi(WO{sub 4}){sub 2} transforms from tetragonal into monoclinic, which starts around 7 GPa and completes at about 13 GPa. With pressure higher than 29 GPa, the NaBi(WO{sub 4}){sub 2} turns into amorphous state. Highlights: ► Raman and X-ray diffraction studies performed on NaBi(WO{sub 4}){sub 2} up to 30.7 and 36.2 GPa, respectively. ► The tetragonal (I4{sub 1}/a) into monoclinic (P2/m) phase transition is determined. ► With pressure higher than 29 GPa, the NaBi(WO{sub 4}){sub 2} ultimately turns into amorphous state. ► The ambient pressure bulk modulus and volume of tetragonal and monoclinic phases are obtained.

  6. UV-VUV synchrotron radiation spectroscopy of NiWO4

    NASA Astrophysics Data System (ADS)

    Kuzmin, A.; Pankratov, V.; Kalinko, A.; Kotlov, A.; Shirmane, L.; Popov, A. I.

    2016-07-01

    Photoluminescence and excitation spectra of microcrystalline and nanocrystalline nickel tungstate (NiWO4) were measured using UV-VUV synchrotron radiation source. The origin of the bands is interpreted using comparative analysis with isostructural ZnWO4 tungstate and based on the results of recent first-principles band structure calculations. The influence of the local atomic structure relaxation and of Ni2+ intra-ion d-d transitions on the photoluminescence band intensity are discussed.

  7. 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.

  8. 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.

  9. 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

    2016-01-01

    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

  10. 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

  11. Memristive properties of hexagonal WO3 nanowires induced by oxygen vacancy migration.

    PubMed

    He, Xiongwu; Yin, Yanling; Guo, Jie; Yuan, Huajun; Peng, Yuehua; Zhou, Yong; Zhao, Ding; Hai, Kuo; Zhou, Weichang; Tang, Dongsheng

    2013-01-01

    Tungsten trioxide (WO3) is always oxygen-deficient or non-stoichiometric under atmospheric conditions. Positively charged oxygen vacancies prefer to drift as well as electrons when the electric field is strong enough, which will alter the distribution of oxygen vacancies and then endow WO3 with memristive properties. In Au/WO3 nanowire/Au sandwich structures with two ohmic contacts, the axial distribution of oxygen vacancies and then the electrical transport properties can be more easily modulated by bias voltage. The threshold electric field for oxygen vacancy drifting in single-crystal hexagonal WO3 nanowire is about 106 V/m, one order of magnitude less than that in its granular film. At elevated temperatures, the oxygen vacancy drifts and then the memristive effect can be enhanced remarkably. When the two metallic contacts are asymmetric, the WO3 nanowire devices even demonstrate good rectifying characteristic at elevated temperatures. Based on the drift of oxygen vacancies, nanoelectronic devices such as memristor, rectifier, and two-terminal resistive random access memory can be fabricated on individual WO3 nanowires. PMID:23347429

  12. Structural, optical and electrochromic properties of RF magnetron sputtered WO3 thin films

    NASA Astrophysics Data System (ADS)

    Madhavi, V.; Kondaiah, P.; Hussain, O. M.; Uthanna, S.

    2014-12-01

    Thin films of tungsten trioxide (WO3) have been prepared by RF reactive magnetron sputtering of tungsten target at different substrate temperatures in the range 303-673 K and at fixed oxygen partial pressure of 6×10-2 Pa and sputter pressure of 4 Pa. The effect of substrate temperature on the structural, morphological, optical and electrochromic properties of WO3 films was systematically studied. The films formed at 303 K were of X-ray amorphous, while those deposited at substrate temperatures ≥473 K were crystallized into orthorhombic phase WO3. The crystallite size of the films increased from 17 to 24 nm with increase of substrate temperature from 473 to 673 K. Raman studies confirmed that the presence of O-W-O and W=O bonds in WO3 films. The surface morphology of the films was significantly varied with substrate temperature. The optical transmittance data revealed that the optical band gap increased from 3.08 to 3.48 eV and refractive index increased from 2.18 to 2.26 with increase of substrate temperature from 303 to 673 K respectively. The WO3 films formed at substrate temperature of 473 K exhibited better optical transmittance modulation of 40% between colored and bleached state with a color efficiency of 33.8 cm2/C and diffusion coefficient of 1.85×10-11 cm2/s.

  13. Memristive properties of hexagonal WO3 nanowires induced by oxygen vacancy migration

    PubMed Central

    2013-01-01

    Tungsten trioxide (WO3) is always oxygen-deficient or non-stoichiometric under atmospheric conditions. Positively charged oxygen vacancies prefer to drift as well as electrons when the electric field is strong enough, which will alter the distribution of oxygen vacancies and then endow WO3 with memristive properties. In Au/WO3 nanowire/Au sandwich structures with two ohmic contacts, the axial distribution of oxygen vacancies and then the electrical transport properties can be more easily modulated by bias voltage. The threshold electric field for oxygen vacancy drifting in single-crystal hexagonal WO3 nanowire is about 106 V/m, one order of magnitude less than that in its granular film. At elevated temperatures, the oxygen vacancy drifts and then the memristive effect can be enhanced remarkably. When the two metallic contacts are asymmetric, the WO3 nanowire devices even demonstrate good rectifying characteristic at elevated temperatures. Based on the drift of oxygen vacancies, nanoelectronic devices such as memristor, rectifier, and two-terminal resistive random access memory can be fabricated on individual WO3 nanowires. PMID:23347429

  14. Study of electrochromism in Ti:WO3 films by sol-gel process

    NASA Astrophysics Data System (ADS)

    Ozer, Nilgun; Dogan, Nilgun

    1998-09-01

    Electrochromism in sol-gel deposited WO3 films containing TiO2 has been observed. The films are deposited by spin coating from peroxo-polytungstic acid and titanium isopropoxide precursors. The films were fabricated on quartz and SnO2:F coated glass substrates. Films were heat treated at 150 degree(s)C. Morphology of the films was examined by scanning electron microscopy, which indicated that the films were smooth and had a pore free surface. Results will be presented detailing the optical switching during electrochemical lithium intercalation. These results will be used to compare the performance of the Ti doped WO3 films with other electrochromics. The Ti:WO3 films all color cathodically, and the color state is a neutral grayish blue color, while the bleached state is transparent and colorless. Results of the cyclic stability will also be presented. The neutral color of the Ti:WO3 films means that electrochromic windows based on Ti:WO3 may have significant advantages over WO3-based windows. A detailed analysis of the optical properties of the bleached and colored states of the films will be presented. The dynamics of coloration for these films is also under investigation, and preliminary results will be presented.

  15. Functionalized biocompatible WO3 nanoparticles for triggered and targeted in vitro and in vivo photothermal therapy.

    PubMed

    Sharker, Shazid Md; Kim, Sung Min; Lee, Jung Eun; Choi, Kyung Ho; Shin, Gyojic; Lee, Sangkug; Lee, Kang Dae; Jeong, Ji Hoon; Lee, Haeshin; Park, Sung Young

    2015-11-10

    We report on dopamine-conjugated hyaluronic acid (HA-D), a mussel-inspired facile capping material that can modify tungsten oxide (WO3) nanoparticles to be both biocompatible and targetable, allowing precise delivery (WO3-HA) to a tumor site. Near-infrared (NIR) irradiated WO3-HA showed a rapid and substantial rise in photothermal heat to complete in vitro thermolysis of malignant MDAMB and A549 cancer cellsbut was found to be relatively less sensitive to normal MDCK cells. A long-term in vivo investigation of ~10 nm HA thickness on WO3 (WO3-HA) nanoparticles demonstrated efficient photo-thermal conversion with time-dependent tumor target accumulation. This long-termin vivo survival study ofWO3-HA showed promising biocompatibility, with a complete recovery from malignant tumor. Due to the importance of keeping simplicity in the design of therapeutic nanoparticles, we therefore expect that this facile scheme (HA-D) would contribute to the biocompatible development of versatile metallic nanoparticles for photothermal applications. PMID:26381897

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. Impact of proton diffusion and the hydrogen photospillover upon the photochromic sensitivity of the WO3 films and the WO3 double-layer structures

    NASA Astrophysics Data System (ADS)

    Gavrilyuk, A. I.

    2013-05-01

    It has been shown that the hydrogen photochromism, i.e., photochromism arising in WO3 films due to hydrogen atoms detached from hydrogen donor molecules under the action of light, is massively impacted by proton diffusion. The control of the diffusion can be established by the combined use of two types of hydrogen-containing molecules; one (organic) playing the role of the hydrogen donor, whereas the other (water) provides pathways for the proton diffusion. The film morphology highly influences formation of the proton conducting water wires in pores of the WO3 films. The spirit is that the hydrogen photospillover is used here: the hydrogen atoms detached from the hydrogen donor molecules adsorbed on the surface of the highly disordered WO3 films flow to the polycrystalline WO3 films along the special water pathways that are formed in the highly disordered films. The hydrogen spillover triggered by light makes it possible to create the photochromic systems with enhanced photochromic sensitivity and special optical characteristics of the photochromic state.

  3. Temperature-dependent Raman scattering study of the defect pyrochlores RbNbWO6 and CsTaWO6.

    PubMed

    Mączka, M; Knyazev, A V; Majchrowski, A; Hanuza, J; Kojima, S

    2012-05-16

    Lattice dynamics calculations and temperature-dependent Raman scattering experiments were performed on RbNbWO(6) and CsTaWO(6) pyrochlore oxides. The observed bands were assigned to the respective motions of atoms in the unit cell. The spectra showed the presence of additional Raman bands not allowed for by the [Formula: see text] cubic structure. We have shown that these bands appear due to both substitutional disorder in the 16c sites and displacive disorder of the A ions. Raman studies also revealed the presence of an additional 80 cm(-1) band at room temperature for RbNbWO(6), not observed for CsTaWO(6). The presence of this band has been attributed to off-center displacement of the Nb and W ions due to structural phase transition into a tetragonal ferroelectric phase. The temperature evolution of the 80 cm(-1) band intensity revealed that it disappeared at a much higher temperature (about 650 K) than the reported phase transition temperature (about 360 K). This behavior is reminiscent of chemically disordered perovskite ferroelectrics, including relaxor ferroelectrics, and was attributed to the presence of small polar regions with local tetragonal distortion embedded in the paraelectric matrix of the [Formula: see text] structure. PMID:22517168

  4. 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.

  5. Synthesis and characterization of MnWO4 nanoparticles encapsulated in mesoporous silica SBA-15 by fast microwave-assisted method

    NASA Astrophysics Data System (ADS)

    Hoang, Luc Huy; Hanh, Pham Van; Phu, Nguyen Dang; Chen, Xiang-Bai; Chou, Wu Ching

    2015-02-01

    The MnWO4 nanoparticles encapsulated in mesoporous silica (MnWO4/SBA-15) was successfully synthesized by a fast microwave-assisted method. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen absorption-desorption isotherm, and Fourier transform infrared spectroscopy (FTIR). Our results showed that the MnWO4/SBA-15 nanocomposites have the ordered hexagonal meso-structure of SBA-15, indicating MnWO4 nanoparticles were successfully distributed into the channels of SBA-15. The size of MnWO4 nanoparticles in SBA-15 is significantly smaller than the size of MnWO4 nanoparticles prepared without SBA-15, indicating that the MnWO4/SBA15 nanocomposites would be very promising for improving photocatalytic activity of MnWO4 nanoparticles.

  6. Harnessing and storing visible light using a heterojunction of WO3 and CdS for sunlight-free catalysis.

    PubMed

    Kim, Seonghun; Park, Yiseul; Kim, Wooyul; Park, Hyunwoong

    2016-08-01

    CdS and WO3 (CdS/WO3) bilayer film electrodes are fabricated to harness solar visible light (λ > 420 nm) and store photogenerated electrons for possible use during periods of unavailable sunlight. The overall film thickness is approximately 50-60 μm, while the CdS underlayer is slightly thinner than WO3 owing to a packing effect. The energetics of CdS and WO3 determined by optical and electrochemical analyses enables cascaded electron transfer from CdS to WO3. The open circuit potential (EOCP) of CdS/WO3 under visible light (approximately -0.35 V vs. SCE) is nearly maintained even in the absence of light, with a marginal decrease (∼0.15 V) in ∼20 h of darkness. Neither CdS nor WO3 alone exhibits such behavior. The electron lifetimes (τ) of CdS and WO3 are each less than 100 s, whereas coupling of the two increases τ to ∼2500 s at the EOCP. In the absence of dissolved O2, τ further increases, suggesting that O2 is the primary electron acceptor. In spite of oxic conditions, CdS/WO3 is capable of continuously reducing Cr(6+) to Cr(3+) and Ag(+) to Ag(0) after removal of visible light. The number of utilized (i.e., stored) electrons in the reductions of Cr(6+) and Ag(+) are estimated to be ∼1.08 × 10(17) and ∼0.87 × 10(17), respectively. The primary role of CdS is to be a visible-light absorber in the 420-565 nm wavelength range, transferring the photogenerated electrons to WO3. The electrons stored in WO3 are gradually released to electron acceptors with suitable redox potentials. PMID:27411566

  7. Chromic mechanism in amorphous WO{sub 3} films

    SciTech Connect

    Zhang, J.G.; Benson, D.K.; Tracy, C.E.; Deb, S.K.; Czanderna, A.W.; Bechinger, C.

    1997-06-01

    The authors propose a new model for the chromic mechanism in amorphous tungsten oxide films (WO{sub 3{minus}y}{center_dot}nH{sub 2}O). This model not only explains a variety of seemingly conflicting experimental results reported in the literature that cannot be explained by existing models, it also has practical implications with respect to improving the coloring efficiency and durability of electrochromic devices. According to this model, a typical as-deposited tungsten oxide film has tungsten mainly in W{sup 6{minus}} and W{sup 4{minus}} states and can be represented as W{sub 1{minus}y}{sup 6+} W{sub y}{sup 4+}O{sub 3{minus}y}{center_dot}nH{sub 2}O. The proposed chromic mechanism is based on the small polars transition between the charge-induced W{sup 5+} state and the original W{sup 4+} state instead of the W{sup 5+} and W{sup 6+} states as suggested in previous models. The correlation between the electrochromic and photochromic behavior in amorphous tungsten oxide films is also discussed.

  8. Chromic mechanism in amorphous WO{sub 3} films

    SciTech Connect

    Zhang, J G; Benson, D K; Tracy, C E; Deb, S K; Czanderna, A W; Bechinger, C

    1996-11-01

    The authors propose a new model for the chromic mechanism in amorphous tungsten oxide films (WO{sub 3{minus}y}{center_dot}nH{sub 2}O). This model not only explains a variety of seemingly conflicting experimental results reported in the literature that cannot be explained by existing models, it also has practical implications with respect to improving the coloring efficiency and durability of electrochromic devices. According to this model, a typical as-deposited tungsten oxide film has tungsten mainly in W{sup 6+} and W{sup 4+} states and can be represented as W{sub 1{minus}y}{sup 6+} W{sub y}{sup 4+}O{sub 3{minus}y}{center_dot}nH{sub 2}O. The proposed chromic mechanism is based on the small polaron transition between the charge-induced W{sup 5+} state and the original W{sup 4+} state instead of the W{sup 5+} and W{sup 6+} states as suggested in previous models. The correlation between the electrochromic and photochromic behavior in amorphous tungsten oxide films is also discussed.

  9. A study of Ti-doped WO3 thin films using comparative theoretical and experimental approach

    NASA Astrophysics Data System (ADS)

    Paez, Aurelio

    Metal oxides like Tungsten Oxide (WO3) are well documented and characterized in the literature, with uses in darkening windows and mirrors, flat computer displays, solar panel cooling, and sensors (of interest in this study). Ti doping of WO3 is less documented and the focus of this study. Sample thin films of pure WO3 and varyingly Ti doped WO3 were prepared using Radio Frequency magnetron sputtering (RF) (13.56 MHz) to grow thin films on a silicon substrate. This study aims to compare multiple Ti doping percentages in WO3 theoretically and then compare with experimental data taken from thin films of various Ti doping levels grown at temperatures ranging from room temperature to 400 0°C. Characterization of the materials was to be conducted using Fourier Transform Infrared Spectroscopy, Raman Spectroscopy, X-ray diffraction, and other theoretical and simulated approaches. Theoretical calculations optimized Ti doping at somewhere between 6.25% and 12%. Experimental data indicates that under the given growing conditions optimal Ti doping is 5%. The percentage of Ti may be able to be increased and the material retain desired characteristics with an increased growth temperature above 400 0°C as annealing samples post-growth has no positive impact on the thin film structure.

  10. Facile synthesis of decorated graphene oxide sheets with WO3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Adineh, Ensieh; Rasuli, Reza

    2015-09-01

    Potential applications of graphene oxide (GO) nanocomposites have attracted remarkable attention to modify its properties by functionalizing and decorating with nanoparticles. In this work, after synthesis of GO sheets by oxidation and exfoliation of natural graphite, they were decorated with tungsten oxide nanoparticles using arc discharge in GO solution. Transmission electron microscopy shows that the chain of WO3 nanoparticles decorates the GO sheets. Fourier transform infrared spectroscopy and Raman spectroscopy show that WO3 nanoparticles are attached to GO sheets by bond formation between the tungsten and oxygen of functional groups, especially with epoxides on the GO sheets. Nanocomposite production in different arc currents shows that the greater the electrical current, the stronger the bond is formed between WO3 and GO. X-ray diffraction confirms that the WO3 nanoparticles on the GO are highly crystalline in monoclinic phase. Moreover, by increasing the arc current from 20 to 40 A, the band gap energy of GO + WO3 decreases to ~2.6 eV.

  11. Facile Fabrication of Sandwich Structured WO3 Nanoplate Arrays for Efficient Photoelectrochemical Water Splitting.

    PubMed

    Feng, Xiaoyang; Chen, Yubin; Qin, Zhixiao; Wang, Menglong; Guo, Liejin

    2016-07-20

    Herein, sandwich structured tungsten trioxide (WO3) nanoplate arrays were first synthesized for photoelectrochemical (PEC) water splitting via a facile hydrothermal method followed by an annealing treatment. It was demonstrated that the annealing temperature played an important role in determining the morphology and crystal phase of the WO3 film. Only when the hydrothermally prepared precursor was annealed at 500 °C could the sandwich structured WO3 nanoplates be achieved, probably due to the crystalline phase transition and increased thermal stress during the annealing process. The sandwich structured WO3 photoanode exhibited a photocurrent density of 1.88 mA cm(-2) and an incident photon-to-current conversion efficiency (IPCE) as high as 65% at 400 nm in neutral Na2SO4 solution under AM 1.5G illumination. To our knowledge, this value is one of the best PEC performances for WO3 photoanodes. Meanwhile, simultaneous hydrogen and oxygen evolution was demonstrated for the PEC water splitting. It was concluded that the high PEC performance should be attributed to the large electrochemically active surface area and active monoclinic phase. The present study can provide guidance to develop highly efficient nanostructured photoelectrodes with the favorable morphology. PMID:27347739

  12. Fabrication and photoelectrochemical properties of porous ZnWO 4 film

    NASA Astrophysics Data System (ADS)

    Zhao, Xu; Yao, Wenqing; Wu, Yan; Zhang, Shicheng; Yang, Haipeng; Zhu, Yongfa

    2006-08-01

    Porous ZnWO 4 films have been fabricated on Indium-tin oxide (ITO) glass and its photoelectrochemical properties and high photocatalytic activities towards degradation of rhodamine B (RhB) has been investigated. Using amorphous heteronuclear complex as precursor and with the addition of polyethylene glycol (PEG, molecular weight=400), the porous ZnWO 4 films have been achieved at the temperature of 500 °C via dip-coating method. It is composed of approximately 70 nm-sized particles and exhibits substantial porosity. The textures and porosity of ZnWO 4 films are dependent on preparation factors, such as the ratio of precursor/PEG and the annealing conditions. The formation mechanism of porous ZnWO 4 films was proposed. The porous ZnWO 4 films exhibited high photocatalytic activities towards degrading RhB. The top of valence band and the bottom of the conduction band was estimated to be -0.56 and 3.45 eV (vs. saturated calomel electrode (SCE)), respectively.

  13. Design of a highly photocatalytically active ZnO/CuWO4 nanocomposite.

    PubMed

    Mavrič, T; Valant, M; Forster, M; Cowan, A J; Lavrenčič, U; Emin, S

    2016-12-01

    Here we report the synthesis, photocatalytic activity and mechanistic study of a novel charge separation heterostructure (HTS). A ZnO/CuWO4 HTS material is reported for the first time. The nanocomposite (NC) consist of CuWO4 nanoparticles (ca. 200-400nm) decorated with ZnO nanorods (ca. 30nm, 100nm length) and is shown to be a highly active photocatalyst for the decomposition of model contaminants including methyl orange (MO) and terephthalic acid (TPA). The ZnO/CuWO4 interface is shown to be key in controlling the enhanced activity of the composite material. Transient absorption (TA) spectroscopy studies demonstrate that photoinduced charge transfer across the ZnO/CuWO4 interface increases electron-hole lifetimes by 3 orders of magnitude, from <20μs in ZnO to 30ms in the ZnO/CuWO4 NC sample. Our findings show that through interface design efficient HTS materials can be prepared for a wide range of photocatalytic applications. PMID:27552417

  14. 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

  15. 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.

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

    PubMed Central

    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. PMID:22221563

  18. Structural, electrical and optical properties of TiO 2 doped WO 3 thin films

    NASA Astrophysics Data System (ADS)

    Patil, P. S.; Mujawar, S. H.; Inamdar, A. I.; Shinde, P. S.; Deshmukh, H. P.; Sadale, S. B.

    2005-12-01

    TiO 2 doped WO 3 thin films were deposited onto glass substrates and fluorine doped tin oxide (FTO) coated conducting glass substrates, maintained at 500 °C by pyrolytic decomposition of adequate precursor solution. Equimolar ammonium tungstate ((NH 4) 2WO 4) and titanyl acetyl acetonate (TiAcAc) solutions were mixed together at pH 9 in volume proportions and used as a precursor solution for the deposition of TiO 2 doped WO 3 thin films. Doping concentrations were varied between 4 and 38%. The effect of TiO 2 doping concentration on structural, electrical and optical properties of TiO 2 doped WO 3 thin films were studied. Values of room temperature electrical resistivity, thermoelectric power and band gap energy ( Eg) were estimated. The films with 38% TiO 2 doping in WO 3 exhibited lowest resistivity, n-type electrical conductivity and improved electrochromic performance among all the samples. The values of thermoelectric power (TEP) were in the range of 23-56 μV/K and the direct band gap energy varied between 2.72 and 2.86 eV.

  19. 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.

  20. 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.

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

    DOEpatents

    Liu, Ping; Tracy, C. Edwin; Pitts, J. Roland; Lee, Se-Hee

    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.

  2. Preparation of α-SnWO4/SnO2 heterostructure with enhanced visible-light-driven photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Yao, Shiyue; Zhang, Min; Di, Junwei; Wang, Zuoshan; Long, Yumei; Li, Weifeng

    2015-12-01

    In this work, a novel α-SnWO4/SnO2 heterostructure was synthesized via a facile two-step hydrothermal method. The as-prepared products were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scan electron microscopy (SEM) and transmission electron microscopy (TEM), which confirmed the typical orthorhombic α-SnWO4 phase, plate-like morphology and α-SnWO4/SnO2 heterostructure. The photocatalytic studies revealed that the attachment of SnO2 nanoparticles on the surface of α-SnWO4 plates can remarkably improve their photocatalytic activities and the α-SnWO4/SnO2 heterostructure exhibited the best photocatalytic properties in the degradation of methyl orange (MO) under visible light irradiation. The degradation rate of MO on α-SnWO4/SnO2 plate was 97% within 40 min and the photocatalytic degradation reaction followed the pseudo-first-order kinetics. The enhanced photocatalytic property was ascribed to the large surface area and the heterojuction between α-SnWO4 and SnO2, which can facilitate efficient charge separation of photogenerated electron-hole pairs. Furthermore, α-SnWO4/SnO2 nanocomposite demonstrated good recyclability, which is useful for its practical application.

  3. Influences of porous structurization and Pt addition on the improvement of photocatalytic performance of WO3 particles.

    PubMed

    Arutanti, Osi; Nandiyanto, Asep Bayu Dani; Ogi, Takashi; Kim, Tae Oh; Okuyama, Kikuo

    2015-02-11

    Tungsten trioxide (WO3) displays excellent performance in solar-related material applications. However, this material is rare and expensive. Therefore, developing efficient materials using smaller amounts of WO3 is inevitable. In this study, we investigated how to create high photocatalytic performance of WO3 particles containing platinum (Pt, as a co-catalyst) and homogeneously spherical macropores (as a medium to enable access of large molecules and light penetration into the remote internal regions of the catalyst). The present particles were prepared by spray drying of a precursor solution containing WO3 nanoparticles, Pt solution, and polystyrene (PS) spheres (as a colloidal template). Photocatalytic studies showed that changes in particle morphology (from dense with smooth surfaces, to dense with rough surfaces, to porous structures) and added Pt effectively improved the photocatalytic performance over WO3 nanoparticles. Our results showed that the best precursor (prepared using a PS/WO3 mass ratio of 0.32 and containing Pt co-catalyst) provided WO3 particles with a photocatalytic rate of more than 5 times that of pure 10 nm WO3 nanoparticles. Moreover, the catalyst can be effectively recycled without an apparent decrease in its photocatalytic activity. The experimental results were also supported by a proposal mechanism of the photocatalytic reaction phenomenon. PMID:25608579

  4. Catalyst-loaded porous WO3 nanofibers using catalyst-decorated polystyrene colloid templates for detection of biomarker molecules.

    PubMed

    Choi, Seon-Jin; Kim, Sang-Joon; Koo, Won-Tae; Cho, Hee-Jin; Kim, Il-Doo

    2015-02-14

    Pore-loaded WO3 nanofibers (NFs) functionalized with spherical catalyst films were achieved via electrospinning combined by the sacrificial templating route using layer-by-layer (LbL) catalyst assembled polystyrene (PS) colloids. The catalyst-loaded porous WO3 NFs exhibited significantly improved toluene and acetone detection capability for potential application in exhaled breath analysis. PMID:25572467

  5. 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). PMID:20614790

  6. 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.

  7. 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. PMID:23553445

  8. Alternating current impedance and Raman spectroscopic study on electrochromic a-WO{sub 3} films

    SciTech Connect

    Lee, Se-Hee; Cheong, Hyeonsik M.; Tracy, C. Edwin; Mascarenhas, Angelo; Pitts, J. Roland; Jorgensen, Gary; Deb, Satyen K.

    2000-06-26

    The chemical diffusion of lithium ions in a-Li{sub x}WO{sub 3} films is investigated using alternating current impedance spectroscopy and Raman scattering measurements. The diffusion coefficients increase with increasing x in a-Li{sub x}WO{sub 3} up to x=0.072 and then decrease. Raman measurements show that the W{sup 6+}=O/O-W{sup 6+}-O ratio also increases at the early stage of lithium insertion and then decreases with further lithium insertion. We conclude that the diffusion kinetics of lithium ions in a-Li{sub x}WO{sub 3} films is very closely related to the W{sup 6+}=O/O-W{sup 6+}-O ratio. (c) 2000 American Institute of Physics.

  9. Nitrogen-incorporation induced changes in the microstructure of nanocrystalline WO3 thin films

    SciTech Connect

    Vemuri, Venkata Rama Sesha R.; Noor-A-Alam, M.; Gullapalli, Satya K.; Engelhard, Mark H.; Ramana, C.V.

    2011-12-30

    Nitrogen doped tungsten oxide (WO3) films were grown by reactive magnetron sputter-deposition by varying the nitrogen content in the reactive gas mixture keeping the deposition temperature fixed at 400 C. The crystal structure, surface morphology, chemical composition, and electrical resistivity of nitrogen doped WO3 films were evaluated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and electrical conductivity measurements. The results indicate that the nitrogen-doping induced changes in the microstructure and electrical properties of WO3 films are significant. XRD measurements coupled with SEM analysis indicates that the increasing nitrogen content decreases the grain size and crystal quality. The nitrogen concentration increases from 0 at.% to 1.35 at.% with increasing nitrogen flow rate from 0 to 20 sccm. The corresponding dc electrical conductivity of the films had shown a decreasing trend with increasing nitrogen content.

  10. Effect of Pt nanoparticles on the optical gas sensing properties of WO3 thin films.

    PubMed

    Qadri, Muhammad U; Diaz, Alex Fabian Diaz; 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

  11. Low-Temperature H2S Detection with Hierarchical Cr-Doped WO3 Microspheres.

    PubMed

    Wang, Yanrong; Liu, Bin; Xiao, Songhua; Wang, Xinghui; Sun, Leimeng; Li, Han; Xie, Wuyuan; Li, Qiuhong; Zhang, Qing; Wang, Taihong

    2016-04-20

    Hierarchical Cr-doped WO3 microspheres have been successfully synthesized for efficient sensing of H2S gas at low temperatures. The hierarchical structures provide an effective gas diffusion path via well-aligned micro-, meso-, and macroporous architectures, resulting in significant enhancement in sensing response to H2S. The temperature and gas concentration dependence on the sensing properties elucidate that Cr dopants remarkably improve the response and lower the sensor' operating temperature down to 80 °C. Under 0.1 vol % H2S, the response of Cr-doped WO3 sensor is 6 times larger than pristine WO3 sensor at 80 °C. We suggest the increasing number of oxygen vacancies created by Cr dopants to be the underlying reason for enhancement of charge carrier density and accelerated reactions with H2S. PMID:27008435

  12. Solid-base loaded WO3 photocatalyst for decomposition of harmful organics under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Kako, Tetsuya; Meng, Xianguang; Ye, Jinhua

    2015-10-01

    Composite of NaBiO3-loaded WO3 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 NaBiO3 can be estimated, respectively, as +2.5 V and -0.1 to 0 V. Furthermore, WO3, NaBiO3, 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 CO2 than individual WO3 or NaBiO3 because of charge separation promotion and the base effect of NaBiO3.

  13. 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}.

  14. 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.

  15. Time-resolved luminescence spectroscopy of structurally disordered K3WO3F3 crystals

    NASA Astrophysics Data System (ADS)

    Omelkov, S. I.; Spassky, D. A.; Pustovarov, V. A.; Kozlov, A. V.; Isaenko, L. I.

    2016-08-01

    Three emission centers of exciton-like origin, with distinct relaxation time, emission and excitation spectra were revealed in K3WO3F3 and described taking into account its structural disordering. Low-temperature monoclinic phase of K3WO3F3 features few anion sites with mixed oxygen/fluorine occupancy per [WO3F3] octahedron. Therefore, different kinds of distorted octahedra form, providing different luminescence centers. The time-resolved luminescence spectroscopy technique was applied to distinguish these centers. The simultaneous thermal quenching of them above ∼200 K was qualitatively explained involving dynamic structural disorder of the compound. The energy transfer mechanism between centers was found and tentatively described by the diffusion of excitons. Apart from intrinsic luminescence, the PL of defect-related centers was discovered and the role of shallow charge carrier traps in the low-temperature persistent luminescence was revealed.

  16. Understanding the synergistic effect of WO3-BiVO4 heterostructures by impedance spectroscopy.

    PubMed

    Shi, Xinjian; Herraiz-Cardona, Isaac; Bertoluzzi, Luca; Lopez-Varo, Pilar; Bisquert, Juan; Park, Jong Hyeok; Gimenez, Sixto

    2016-04-01

    WO3-BiVO4 n-n heterostructures have demonstrated remarkable performance in photoelectrochemical water splitting due to the synergistic effect between the individual components. Although the enhanced functional capabilities of this system have been widely reported, in-depth mechanistic studies explaining the carrier dynamics of this heterostructure are limited. The main goal is to provide rational design strategies for further optimization as well as to extend these strategies to different candidate systems for solar fuel production. In the present study, we perform systematic optoelectronic and photoelectrochemical characterization to understand the carrier dynamics of the system and develop a simple physical model to highlight the importance of the selective contacts to minimize bulk recombination in this heterostructure. Our results collectively indicate that while BiVO4 is responsible for the enhanced optical properties, WO3 controls the transport properties of the heterostructured WO3-BiVO4 system, leading to reduced bulk recombination. PMID:26975634

  17. Fabrication of ion doped WO3 photocatalysts through bulk and surface doping.

    PubMed

    Wang, Xiaoying; Pang, Laixue; Hu, Xiuying; Han, Nianfeng

    2015-09-01

    Na(+) doped WO3 nanowire photocatalysts were prepared by using post-treatment (surface doping) and in situ (bulk doping) doping methods. Photocatalytic degradation of Methyl Blue was tested under visible light irradiation, the results showed that 1wt.% Na(+) bulk-doped WO3 performed better, with higher photoactivity than surface-doped WO3. Photoelectrochemical characterization revealed the differences in the photocatalytic process for surface doping and bulk doping. Uniform bulk doping could generate more electron-hole pairs, while minimizing the chance of electron-hole recombination. Some bulk properties such as the bandgap, Fermi level and band position could also be adjusted by bulk doping, but not by surface doping. PMID:26354695

  18. Flux growth and characterization of Sr2NiWO6 single crystals

    NASA Astrophysics Data System (ADS)

    Blum, C. G. F.; Holcombe, A.; Gellesch, M.; Sturza, M. I.; Rodan, S.; Morrow, R.; Maljuk, A.; Woodward, P.; Morris, P.; Wolter, A. U. B.; Büchner, B.; Wurmehl, S.

    2015-07-01

    Single crystals of the double perovskite Sr2NiWO6 were synthesized via SrCl2 flux growth using high quality, phase-pure polycrystalline Sr2NiWO6 as precursor material. This high quality precursor enabled us to grow large and phase pure crystals with sizes up to 1 mm ×1 mm in the basal plane and octahedral morphology. We measured the temperature dependence of the magnetization along the c-axis and along the ab plane. The analysis of the data allows a precise determination of the effective magnetic moment and the Curie-Weiss temperature. Sr2NiWO6 orders antiferromagnetically at TN=54 K as revealed by magnetization and specific heat data.

  19. Giant Persistent Photoconductivity of the WO3 Nanowires in Vacuum Condition

    PubMed Central

    2011-01-01

    A giant persistent photoconductivity (PPC) phenomenon has been observed in vacuum condition based on a single WO3 nanowire and presents some interesting results in the experiments. With the decay time lasting for 1 × 104 s, no obvious current change can be found in vacuum, and a decreasing current can be only observed in air condition. When the WO3 nanowires were coated with 200 nm SiO2 layer, the photoresponse almost disappeared. And the high bias and high electric field effect could not reduce the current in vacuum condition. These results show that the photoconductivity of WO3 nanowires is mainly related to the oxygen adsorption and desorption, and the semiconductor photoconductivity properties are very weak. The giant PPC effect in vacuum condition was caused by the absence of oxygen molecular. And the thermal effect combining with oxygen re-adsorption can reduce the intensity of PPC.

  20. Anomalous spin state of Fe in double perovskite oxide Sr 2FeWO 6

    NASA Astrophysics Data System (ADS)

    Kawanaka, H.; Hase, I.; Toyama, S.; Nishihara, Y.

    2000-07-01

    In the series of Sr 2FeTO 6 (T=4d or 5d), the valence of Fe is 3+ in most of the compounds. However, recently we have found that the Sr 2FeWO 6 has Fe 2+ state. Sr 2FeWO 6 is an insulator with an antiferromagnetic transition temperature of 37 K. From the Mössbauer experiment, below ∼20 K, a center shift of +1.2 mm/ s relative to metallic iron and a quadrupole splitting of 1.9 mm/ s are obtained. The quadrupole splitting has strong temperature dependence. The hyperfine field is ∼110 kOe which seems to be quite small. We concluded that the iron ground state of Sr 2FeWO 6 is Fe 2+ high-spin ( S=2) state.

  1. Electrochromic properties of spray deposited TiO 2-doped WO 3 thin films

    NASA Astrophysics Data System (ADS)

    Patil, P. S.; Mujawar, S. H.; Inamdar, A. I.; Sadale, S. B.

    2005-08-01

    TiO 2-doped WO 3 thin films were deposited onto fluorine-doped tin oxide coated conducting glass substrates using spray pyrolysis technique at 525 °C. The volume percentage of TiO 2 dopant was varied from 13% to 38%. The thin film samples were transparent, uniform and strongly adherent to the substrates. Electrochromical properties of TiO 2-doped WO 3 thin films were studied with the help of cyclic voltammetry (CV), chronoamperometry (CA) and chronocoulometry (CC) techniques. It has been found that TiO 2 doping in WO 3 enhances its electrochromic performance. Colouration efficiency becomes almost double and samples exhibit increasingly high reversibility with TiO 2 doping concentrations, in the studied range.

  2. 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

  3. Synthesis and photoluminescence of novel red-emitting ZnWO4: Pr3 +, Li+ phosphors

    NASA Astrophysics Data System (ADS)

    Wang, Ke; Feng, Wenlin; Feng, Xu; Li, Yao; Mi, Peng; Shi, Shasha

    2016-02-01

    Zn0.997WO4: Pr3 +0.003 and different concentrations (0.1 mol% to 0.9 mol%) of Pr, Li co-doped ZnWO4 red phosphors were prepared by means of solid-state reaction process. The crystalline, surface morphology and luminescent properties of Zn0.997WO4: Pr3 +0.003 and Zn1 - x - yWO4: xPr3 +, yLi+ phosphors were investigated by the X-ray diffraction patterns (XRD), scanning electron microscope (SEM) and fluorescent measurements. From powder XRD analysis, the formation of monoclinic structure with C2/h point-group symmetry and P2/c space group of the as-synthesized samples is confirmed. The SEM image showed that surface morphology of the phosphor powder is irregular cylindricality. The luminescent spectra are dominated by the red emission peaks at 607, 621 and 643 nm, respectively, radiated from the 1D2 → 3H4, 3P0 → 3H6 and 3P0 → 3F2 transitions of Pr3 + ions. The concentrations of the highest luminescent intensity is determined at 0.3 mol% Pr3 + and 0.3 mol% Li co-doped ZnWO4 powder crystal, and the peak intensity is improved more than 3 times in comparison with that of 0.3 mol% Pr3 + single-doped ZnWO4. The enhanced luminescence comes from the improved crystalline and from the charge compensation of Li+ ions. The decay curve and CIE chromaticity coordinates of as-prepared samples are also studied in detail.

  4. Fabrication and photoelectrochemical properties of porous ZnWO{sub 4} film

    SciTech Connect

    Zhao Xu; Yao Wenqing; Wu Yan; Zhang Shicheng; Yang Haipeng; Zhu Yongfa . E-mail: zhuyf@mail.tsinghua.edu.cn

    2006-08-15

    Porous ZnWO{sub 4} films have been fabricated on Indium-tin oxide (ITO) glass and its photoelectrochemical properties and high photocatalytic activities towards degradation of rhodamine B (RhB) has been investigated. Using amorphous heteronuclear complex as precursor and with the addition of polyethylene glycol (PEG, molecular weight=400), the porous ZnWO{sub 4} films have been achieved at the temperature of 500 deg. C via dip-coating method. It is composed of approximately 70 nm-sized particles and exhibits substantial porosity. The textures and porosity of ZnWO{sub 4} films are dependent on preparation factors, such as the ratio of precursor/PEG and the annealing conditions. The formation mechanism of porous ZnWO{sub 4} films was proposed. The porous ZnWO{sub 4} films exhibited high photocatalytic activities towards degrading RhB. The top of valence band and the bottom of the conduction band was estimated to be -0.56 and 3.45 eV (vs. saturated calomel electrode (SCE)), respectively. -- Graphical abstract: Current vs. potential curves for ZnWO{sub 4} film treated at various temperatures: ((a) photo 500 deg. C; (b) photo 550 deg. C; (c) photo TiO{sub 2}; (d) dark 500 deg. C; (e) dark 550 deg. C; (f) dark TiO{sub 2}) in (B) in 0.5 M Na{sub 2}SO{sub 4} solution pH 6.0, scan rate=10 mV s{sup -1}.

  5. Temperature Affects the Tripartite Interactions between Bacteriophage WO, Wolbachia, and Cytoplasmic Incompatibility

    PubMed Central

    Bordenstein, Sarah R.; Bordenstein, Seth R.

    2011-01-01

    Wolbachia infections are a model for understanding intracellular, bacterial symbioses. While the symbiosis is often studied from a binary perspective of host and bacteria, it is increasingly apparent that additional trophic levels can influence the symbiosis. For example, Wolbachia in arthropods harbor a widespread temperate bacteriophage, termed WO, that forms virions and rampantly transfers between coinfections. Here we test the hypothesis that temperatures at the extreme edges of an insect's habitable range alter bacteriophage WO inducibility and in turn, Wolbachia densities and the penetrance of cytoplasmic incompatibility. We report four key findings using the model wasp, Nasonia vitripennis: First, both cold treatment at 18 C and heat treatment at 30 C reduce Wolbachia densities by as much as 74% relative to wasps reared at 25 C. Second, in all cases where Wolbachia densities decline due to temperature changes, phage WO densities increase and inversely associate with Wolbachia densities. Heat has a marked effect on phage WO, yielding phage densities that are 552% higher than the room temperature control. Third, there is a significant affect of insect family on phage WO and endoysmbiont densities. Fourth, at extreme temperatures, there was a temperature-mediated adjustment to the density threshold at which Wolbachia cause complete cytoplasmic incompatibility. Taken together, these results demonstrate that temperature simultaneously affects phage WO densities, endosymbiont densities, and the penetrance of cytoplasmic incompatibility. While temperature shock enhances bacteriophage inducibility and the ensuing bacterial mortality in a wide range of medically and industrially-important bacteria, this is the first investigation of the associations in an obligate intracellular bacteria. Implications to a SOS global sensing feedback mechanism in Wolbachia are discussed. PMID:22194999

  6. Aqueous solution synthesis and photoluminescence properties of two-dimensional dendritic PbWO{sub 4} nanostructures

    SciTech Connect

    Wang, W.S.; Zhen, L.; Xu, C.Y.; Yang, L.; Shao, W.Z.; Chen, Z.L.

    2014-08-15

    Graphical abstract: PbWO{sub 4} two-dimensional dendritic nanostructures (2DDNs) were prepared at room temperature through a facile aqueous solution route using only Pb(NO{sub 3}){sub 2} and Na{sub 2}WO{sub 4} as reaction reagents and distilled water as solvent. - Highlights: • Two-dimensional dendritic PbWO4 nanostructures were prepared through a facile aqueous solution route at room temperature. • A “two-step” growth mechanism was proposed for the formation of two-dimensional dendritic PbWO4 nanostructures. • The two-dimensional dendritic PbWO4 nanostructures exhibit good photoluminescence properties. - Abstract: PbWO{sub 4} two-dimensional dendritic nanostructures (2DDNs) were prepared at room temperature through a facile aqueous solution route. X-ray diffraction, scanning electron microscope, transmission electron microscope and X-ray energy dispersive spectrometer were used to characterize the obtained samples. The PbWO{sub 4} 2DDN was in one plane, with a nearly circular shape and sizes of ∼10 μm. The PbWO{sub 4} 2DDNs were composed of curved nanowires around 200 nm in diameters, which were connected together to form a network nanostructure. The effects of reaction conditions including the concentration of react reagents, the reaction temperature, and the reaction time were systematically investigated and a possible formation mechanism for the formation of 2DDNs was proposed. The optical properties, such as UV–vis spectra and photoluminescence spectra of PbWO{sub 4}, were studied. The advantages of this synthetic route include the first synthesis of PbWO{sub 4} 2DDNs, simple synthetic procedure, room reaction temperature, and high reproducibility of the process.

  7. Electrospinning-derived Tb2(WO4)3:Eu3+nanowires: energy transfer and tunable luminescence properties

    NASA Astrophysics Data System (ADS)

    Hou, Zhiyao; Cheng, Ziyong; Li, Guogang; Wang, Wenxin; Peng, Chong; Li, Chunxia; Ma, Ping'an; Yang, Dongmei; Kang, Xiaojiao; Lin, Jun

    2011-04-01

    One-dimensional Tb2(WO4)3 and Tb2(WO4)3:Eu3+nanowires have been prepared by a combination method of sol-gel process and electrospinning. X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL), low voltage cathodoluminescence (CL) and time-resolved emission spectra as well as kinetic decays were used to characterize the resulting samples. The as-obtained precursor samples present fiber-like morphology with uniform size, and Tb2(WO4)3 and Tb2(WO4)3:Eu3+nanowires were formed after annealing. Under ultraviolet excitation and low-voltage electron beams excitation into WO42-and the f-f transition of Tb3+, the Tb2(WO4)3 samples show the characteristic emission of Tb3+ corresponding to 5D4-7F6, 5, 4, 3 transitions due to an efficient energy transfer from WO42- to Tb3+, while Tb2(WO4)3:Eu3+ samples mainly exhibit the characteristic emission of Eu3+ corresponding to 5D0-7F0, 1, 2 transitions due to an energy transfer occurs from WO42- and Tb3+ to Eu3+. The increase of Eu3+ concentration leads to the increase of the energy transfer efficiency from Tb3+ to Eu3+. The PL color of Tb2(WO4)3:x mol% Eu3+ phosphors can be tuned from green to red easily by changing the doping concentration (x) of Eu3+, making the materials have potential applications in fluorescent lamps and color display fields.

  8. 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.

  9. 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}.

  10. 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.

  11. Preparation and photoelectrocatalytic activity of a nano-structured WO{sub 3} platelet film

    SciTech Connect

    Yagi, Masayuki Maruyama, Syou; Sone, Koji; Nagai, Keiji; Norimatsu, Takayoshi

    2008-01-15

    A tungsten trioxide (WO{sub 3}) film was prepared by calcination from a precursor paste including suspended ammonium tungstate and polyethylene glycol (PEG). The ammonium tungstate suspension was yielded by an acid-base reaction of tungstic acid and an ammonium solution followed by deposition with ethanol addition. Thermogravimetric (TG) analysis showed that the TG profile of PEG is significantly influenced by deposited ammonium tungstate, suggesting that PEG is interacting strongly with deposited ammonium tungstate in the suspension paste. X-ray diffraction (XRD) data indicated that the WO{sub 3} film is crystallized by sintering over 400 deg. C. The scanning electron microscopic (SEM) measurement showed that the film is composed of the nano-structured WO{sub 3} platelets. The semiconductor properties of the film were examined by Mott-Schottky analysis to give flat band potential E{sub FB}=0.30 V vs. saturated calomel reference electrode (SCE) and donor carrier density N{sub D}=2.5x10{sup 22} cm{sup -3}, latter of which is higher than previous WO{sub 3} films by two orders of magnitude. The higher N{sub D} was explained by the large interfacial heterojunction area caused by the nano-platelet structure, which apparently increases capacitance per a unit electrode area. The WO{sub 3} film sintered at 550 deg. C produced 3.7 mA cm{sup -2} of a photoanodic current at 1.2 V vs. SCE under illumination with a 500 W xenon lamp due to catalytic water oxidation. This photocurrent was 4.5-12.8 times higher than those for the other control WO{sub 3} films prepared by similar but different procedures. The high catalytic activity could be explained by the nano-platelet structure. The photocurrent was generated on illumination of UV and visible light below 470 nm, and the maximum incident photon-to-current conversion efficiency (IPCE) was 47% at 320 nm at 1.2 V. Technically important procedures for preparation of nano-structured platelets were discussed. - Graphical abstract: A

  12. Alcohol Dehydration on Monooxo W=O and Dioxo O=W=O Species

    SciTech Connect

    Li, Zhenjun; Smid, Bretislav; Kim, Yu Kwon; Matolin, Vladimir; Kay, Bruce D.; Rousseau, Roger J.; Dohnalek, Zdenek

    2012-08-16

    The dehydration of 1-propanol on nanoporous WO3 films prepared via ballistic deposition at ~20 K has been investigated using temperature programmed desorption, infrared reflection absorption spectroscopy and density functional theory. The as deposited films are extremely efficient in 1-propanol dehydration to propene. This activity is correlated with the presence of dioxo O=W=O groups while monooxo W=O species are shown to be inactive. Annealing of the film induces densification that results in the loss of catalytic activity due to annihilation O=W=O species.

  13. 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.

  14. 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

  15. Distinctions in the Raman Spectroscopy Features of WO3 Materials with Increasing Temperature

    NASA Astrophysics Data System (ADS)

    Garcia-Sanchez, Raul F.; Misra, Prabhakar

    2014-06-01

    Metal oxides are widely used in gas sensor applications due to their low cost, easy production and selectivity. Tungsten Oxide (WO3) is one of the most used metal oxides in the detection of Nitrogen gases (NOx). The purpose of this research is to determine if the Raman features of a metal oxide gas sensor can serve as tools to make estimates regarding the sensor capabilities related to the target gases. This research will be used for gas sensing of oxidizing/reducing toxic gases (i.e. H2S, NOx, SO2, etc.) and finding the effect that temperature, gas concentration, type of gas, exposure time and other variables have on the Raman spectra of metal oxides. In this experiment, the temperature was increased from 30-160 °C and the Raman data was taken using a 780 nm infrared laser. In two of the samples, WO3 on Silicon substrate and WO3 nanopowder, we found vibrational modes at 807, 716 and 271 cm-1, which are indicators of a monoclinic WO3 structure. The WO3 nanowires samples exhibit the O-W-O bond stretching feature is present and asymmetric stretching of the W-O bonds occurs, resulting in a 750 cm-1 band. The intensity of Raman features such as 750 cm-1 for nanowires and 492 and 670 cm-1 for WO3 on Silicon substrate begins to decay as temperature increases. Additionally, the vibrational modes related to O-H and W-OH become more pronounced as temperature increases due to those bonds reacting more strongly to the temperature change than the normal W-O bonds related to the original lattice structure. Finally, all samples have low-frequency phonon mode markers associated with temperature change, and in most cases these change as temperature increases. The understanding of the thermal effects will help develop theoretical models for the identification of specific metal oxide-gas relationships and provide a supplemental way of observing gas adsorption in addition to current conductivity measurements.

  16. Effects of surface properties of (010), (001) and (100) of MnWO4 and FeWO4 on absorption of collector

    NASA Astrophysics Data System (ADS)

    Qiu, X. Y.; Huang, H. W.; Gao, Y. D.

    2016-03-01

    The atom distribution and electronic properties of (010), (001) and (100) planes of MnWO4 and FeWO4 were studied based on a DFT calculation. The surface stabilities of the three planes were compared according to their surface energies. The most stable one is (010) plane, followed by (001) and (100). (010) and (001) are the main planes for absorption of anion collector ions, which is supported by their bonding relationship and charge density distribution of surface atoms and finally proved by the results of flotation test and stereomicroscope analysis. In addition, the tungsten atoms can be viewed as the absorption site for collectors in (001) plane but not in (010) plane, which can explain the phenomenon in flotation test that the recovery of wolframite can hardly be further boosted even with a high dosage of BHA.

  17. 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.

  18. 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

  19. Novel coupled structures of FeWO4/TiO2 and FeWO4/TiO2/CdS designed for highly efficient visible-light photocatalysis.

    PubMed

    Bera, Sandipan; Rawal, Sher Bahadur; Kim, Hark Jin; Lee, Wan In

    2014-06-25

    A quadrilateral disk-shaped FeWO4 nanocrystal (NC) with an average size of ∼35 nm was prepared via hydrothermal reaction. The obtained dark brown FeWO4 NC with a bandgap (Eg) of 1.98 eV was then coupled with TiO2 to form FeWO4/TiO2 composites. The valence band (VB) of FeWO4 (+2.8 eV vs NHE) was more positive than that of TiO2 (+2.7 eV); thus this system could be classified as a Type-B heterojunction. Under visible-light irradiation, 5/95 FeWO4/TiO2 (by wt %) exhibited remarkable photocatalytic activity: the amount of CO2 evolved from gaseous 2-propanol (IP) and the decomposition rate of aqueous salicylic acid (SA) were, respectively, 1.7 and 2.5 times greater than those of typical nitrogen-doped TiO2 (N-TiO2). This unique catalytic property was deduced to arise from the intersemiconductor hole transfer between the VBs of FeWO4 and TiO2. Herein, several experimental evidence were also provided to confirm the hole-transfer mechanism. To further enhance the catalytic efficiency, double-heterojunctioned FeWO4/TiO2/CdS composites were prepared by loading CdS quantum dots (QDs) onto the FeWO4/TiO2 surface. Surprisingly, the catalytic activity for evolving CO2 from IP was 2.6 times greater than that of bare FeWO4/TiO2 and 4.4 times greater than that of N-TiO2, suggesting that both holes and electrons were essential species in decomposing organic compounds. PMID:24847976

  20. Controlled synthesis of three-dimensional hierarchical Bi{sub 2}WO{sub 6} microspheres with optimum photocatalytic activity

    SciTech Connect

    Wang, Hong; Song, Jimei; Zhang, Hui; Gao, Fei; Zhao, Shaojuan; Hu, Haiqin

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer The synthesized method is very simple. It can be widely used in the production. Black-Right-Pointing-Pointer The morphology is novel and the property is fine. Black-Right-Pointing-Pointer The formation of 3D hierarchical microsphere can be induced by changing the concentration of KNO{sub 3}. -- Abstract: Three-dimensional (3D) hierarchical Bi{sub 2}WO{sub 6} microsphere and octahedral Bi{sub 2}WO{sub 6} have been synthesized by a facile hydrothermal method using KNO{sub 3} solution and distilled water as solvent, respectively. The obtained products were characterized by X-ray diffraction, scanning electron microscopy, N{sub 2} adsorption/desorption, and UV-vis diffuse reflectance spectroscopy in detail. The concentration of KNO{sub 3} played a key role in the formation of 3D hierarchical Bi{sub 2}WO{sub 6} microspheres. A possible formation mechanism of Bi{sub 2}WO{sub 6} microsphere was proposed. The photocatalytic activity of the as-synthesized products was evaluated by monitoring the degradation of MB solution under sunlight irradiation. It was found that the photocatalytic activity of the 3D hierarchical Bi{sub 2}WO{sub 6} microsphere was superior to the octahedral Bi{sub 2}WO{sub 6}, which was attributed to the larger surface area and special hierarchical structure of Bi{sub 2}WO{sub 6} microsphere.

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

    PubMed

    Hariharan, V; Radhakrishnan, S; Parthibavarman, M; Dhilipkumar, R; Sekar, C

    2011-09-30

    Nanocrystalline tungsten oxides (WO(3-δ)) are currently receiving a lot of attention because of their interesting electrical, magnetic, optical and mechanical properties. In this report, we present the synthesis of PEG assisted tungsten oxide (WO(3)) nanoparticles by simple household microwave irradiation (2.45 GHz) method. The samples were characterized using powder X-ray diffraction (XRD), thermal analysis (TG/DTA), transmission electron microscopy (TEM), UV-visible diffusion reflectance spectroscopy (UV-VIS-DRS), cyclic voltammetry and electrochemical impedance spectroscopy. Powder XRD results revealed that both the samples prepared with and without surfactant crystallize in the orthorhombic structure corresponding to WO(3) · H(2)O phase. Subsequent annealing under identical conditions (600°C/air/6h) led to significantly different products i.e. monoclinic W(17)O(47) from surfactant free sample and orthorhombic WO(3) from PEG assisted sample. Blue emission was observed through UV-VIS-DRS with blue shift and the band gap energy was estimated as 2.7 and 3.28 eV for PEG assisted as prepared (WO(3) · H(2)O) and annealed samples (WO(3)) respectively. Electrochemical measurements have been performed on all the samples deposited on the surface of glassy carbon (GC) electrode which showed high sensitivity and good selectivity for PEG assisted sample (WO(3) · H(2)O) for the direct detection of L-dopa. PMID:21872074

  2. Controlled Growth of WO3Nanostructures with Three Different Morphologies and Their Structural, Optical, and Photodecomposition Studies

    PubMed Central

    2009-01-01

    Tungsten trioxide (WO3) nanostructures were synthesized by hydrothermal method using sodium tungstate (Na2WO4·2H2O) alone as starting material, and sodium tungstate in presence of ferrous ammonium sulfate [(NH4)2Fe(SO4)2·6H2O] or cobalt chloride (CoCl2·6H2O) as structure-directing agents. Orthorhombic WO3having a rectangular slab-like morphology was obtained when Na2WO4·2H2O was used alone. When ferrous ammonium sulfate and cobalt chloride were added to sodium tungstate, hexagonal WO3nanowire clusters and hexagonal WO3nanorods were obtained, respectively. The crystal structure and orientation of the synthesized products were studied by X-ray diffraction (XRD), micro-Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM), and their chemical composition was analyzed by X-ray photoelectron spectroscopy (XPS). The optical properties of the synthesized products were verified by UV–Vis and photoluminescence studies. A photodegradation study on Procion Red MX 5B was also carried out, showing that the hexagonal WO3nanowire clusters had the highest photodegradation efficiency. PMID:20628456

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

    PubMed

    Tian, Yue; Chen, Baojiu; Yu, Hongquan; Hua, Ruinian; Li, Xiangping; Sun, Jiashi; Cheng, Lihong; Zhong, Haiyang; Zhang, Jinsu; Zheng, Yanfeng; Yu, Tingting; Huang, Libo

    2011-08-15

    Three-dimensional (3D) nanostructured CaWO(4):Tb(3+)microspheres assembled by submicrospindles were synthesized via a mild sonochemical route from an aqueous solution of CaCl(2), TbCl(3) and Na(2)WO(4) with the aid of surfactant Polyglycol 600 (PEG-600). The crystal structure and morphology of the as-prepared products were characterized by using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). Rietveld refinement was carried out on the XRD data. The results showed that the CaWO(4):Tb(3+)nanoparticles can be formed without ultrasonic irradiation or addition of PEG-600. With continuously increasing irradiation time the submicrospindles and microspheres could be self-assembled. The central diameter and length of the submicrospindles are around 190 and 500 nm, respectively. The 3D CaWO(4):Tb(3+)nanostructured microspheres with diameter of 2-4 μm were assembled by the submicrospindles. A possible formation mechanism for the 3D-structured CaWO(4):Tb(3+)microspheres was proposed. The Photoluminescent (PL) properties of Tb(3+) ions in the nanostructured CaWO(4) microspheres were studied. The energy transfer processes in CaWO(4):Tb(3+)microspheres were analyzed. The electric dipole-dipole energy transfers related to (5)D(3) level were studied by inspecting the fluorescence decay of (5)D(3) level. The energy transfer critical distance was estimated. PMID:21621217

  4. Synthesis, luminescence properties, and energy transfer of novel CaWO4:Eu3+, Mn2+ red phosphor

    NASA Astrophysics Data System (ADS)

    Cao, Renping; Xu, Haidong; Peng, Dedong; Jiang, Shenhua; Luo, Zhiyang; Li, Wensheng; Yu, Xiaoguang

    2015-12-01

    Novel CaWO4:Eu3+, Mn2+ red phosphor is synthesized by solid-state reaction method in air. CaWO4:Eu3+, Mn2+ phosphor with excitation 268 and 394 nm emits red light with chromaticity coordinates (x = 0.6403, y = 0.3593). The strongest emission bands peaking at ∼615 nm is attributed to 5D0 → 7F2 of Eu3+ ion. Strong excitation band peaking at ∼394 nm indicates that the phosphor may be excited by near UV (∼394 nm) chip. Emission intensity of CaWO4:Eu3+, Mn2+ phosphor with excitation 268 nm is ∼2 times stronger than that of CaWO4:Eu3+ phosphor owing to energy transfer between Eu3+ ion and Mn2+ ion. Energy transfer from WO4 2 - group and Eu3+ ion to Mn2+ ion in CaWO4:Eu3+, Mn2+ phosphor may be explained via luminescence properties. Luminous mechanism is analyzed by energy level diagrams of WO4 2 - group, Mn2+ and Eu3+ ion. The paper content is helpful to develop and research other novel phosphors.

  5. 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

    2016-02-01

    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. PMID:26781181

  6. Monodisperse spindle-like FeWO{sub 4} nanoparticles: Controlled hydrothermal synthesis and enhanced optical properties

    SciTech Connect

    Guo, Jinxue; Zhou, Xiaoyu; Lu, Yibin; Zhang, Xiao; Kuang, Shaoping; Hou, Wanguo

    2012-12-15

    Monodisperse FeWO{sub 4} nanoparticles with specific spindle-like morphology have been synthesized in the presence of citric acid through hydrothermal process. In the synthesis route, citric acid played four roles such as the reducing agent, chelating regents, structure-directing agent and stabilizing agents. In addition, the morphology of FeWO{sub 4} was dramatically tuned by the pH value of the precursor medium. The optical properties of FeWO{sub 4} were investigated with UV-Vis spectra and photoluminescence spectroscopy. The photocatalytic experiments demonstrated that the decomposition efficiency of the monodisperse spindle-like FeWO{sub 4} nanoparticles is 74% after 30 min of UV irradiation, which displayed remarkable enhanced photodegradation activity compared with ordinary FeWO{sub 4} sample (57%) and normal TiO{sub 2} photocatalysts P-25 (56%). - Monodisperse spindle-like FeWO{sub 4} nanoparticles with enhanced photocatalytic activities. Highlights: Black-Right-Pointing-Pointer Monodisperse spindle-like FeWO{sub 4} were synthesized with hydrothermal method. Black-Right-Pointing-Pointer Citric acid plays key roles in the hydrothermal synthesis. Black-Right-Pointing-Pointer Their morphology can be tuned with pH value of the precursor medium. Black-Right-Pointing-Pointer They show enhanced photocatalytic activities with irradiation of UV light.

  7. An UV photochromic memory effect in proton-based WO{sub 3} electrochromic devices

    SciTech Connect

    Zhang Yong; Lee, S.-H.; Mascarenhas, A.; Deb, S. K.

    2008-11-17

    We report an UV photochromic memory effect on a standard proton-based WO{sub 3} electrochromic device. It exhibits two memory states, associated with the colored and bleached states of the device, respectively. Such an effect can be used to enhance device performance (increasing the dynamic range), re-energize commercial electrochromic devices, and develop memory devices.

  8. Flame Synthesized Single Crystal Nanocolumn-Structured WO3 Thin Films for Photoelectrochemical Water Splitting.

    PubMed

    Ding, Jin-Rui; Kim, Kyo-Seon

    2016-02-01

    Tungsten oxide thin films have been found as an active visible light driven photoanode material for photoelectrochemical water splitting due to its good stability in aqueous solution and energetically favorable valence band position for water oxidation. Morphology control, which determines the performance of WO3 photoanode, is one of most focuses of recent research interests. In this work, we successfully prepared monoclinic WO3 thin films on ITO glass at low range of substrate temperature with a fabrication rate around 100 nm per minute by using aerosol flame deposition process. Single crystal nanocolumns with both triangular pyramid-like and triangular prism-like structure were obtained at certain process conditions. Photoelectrochemical properties of photoelectrodes assembled with both structured WO3 thin films were investigated. The prism-like nanocolumn-structured thin film generated the current density of 1.58 mAcm(-2) at potential of 1.0 V versus Ag/AgCl in 0.5 M H2SO4 solution under illumination of AM 1.5 simulated solar light (100 mVcm(-2)). It presented superior photoelectrochemical performance to pyramid-like nanocolumn-structured WO3 thin film. PMID:27433624

  9. 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.

  10. Marine and freshwater concentration ratios (CR(wo-water)): review of Japanese data.

    PubMed

    Tagami, K; Uchida, S

    2013-12-01

    The water-to-organism (whole body) concentration ratio (CR(wo-water)), which is defined as the ratio of the concentration of a radionuclide in the biota (Bq kg(-1) fresh weight) to that in water (Bq L(-1)), has been used in mathematical models for environmental radiation protection. In the present paper, published global fallout (90)Sr, (137)Cs, (106)Ru, (144)Ce and (239+240)Pu activity concentration data and stable element concentration data for Na, K, Ca, Mg, Fe, Cu and Mn for organisms living in freshwater or seawater areas in Japan were collated. The data suitable for obtaining CR(wo-water) values were identified. CR(wo-water) values of (137)Cs were similar for pelagic fish, benthic fish and whitebait (immature, small fish) with respective geometric means of 30 (range: 4.4-69), 32 (range: 15-54) and 33 (range: 13-84). The calculated CR(wo-water) values of the other radionuclides and stable elements were generally similar to other previously reported values; with the exception that those for Ce were lower for marine biota and those of Cu were higher for freshwater fish. PMID:22770770

  11. Effects of pressure on the emission of CaWO4:Eu3+ phosphor

    NASA Astrophysics Data System (ADS)

    Cheng, Xuerui; Yuan, Chaosheng; Su, Lei; Wang, Yongqiang; Zhu, Xiang

    2014-11-01

    CaWO4:Eu3+ (Ca0.925Eu0.05WO4) and CaWO4 phosphors were synthesized by solid state method. Here, the pressure effect on the photoluminescence of CaWO4:Eu3+ has been investigated with a diamond anvil cell up to 20 GPa at room temperature. It is observed that pressure has a great influence on the fluorescence intensity and the energy levels. With increasing pressure, the spectral features shift towards lower energies, and the 7F1 multiplet will split into three Stark levels due to the removal of the degeneracy by the crystal-field interaction. In addition, the emission intensity of the 5D0 → 7F1 transition decreases significantly. Raman experiments further confirm the scheelite to wolframite structure transformation presents at around 10 GPa. Upon release of pressure, this high-pressure phase transforms back to the original scheelite phase, and continuously remains stable to ambient conditions.

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

    DOE PAGESBeta

    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 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

  13. Ultrasmall Biocompatible WO3- x Nanodots for Multi-Modality Imaging and Combined Therapy of Cancers.

    PubMed

    Wen, Ling; Chen, Ling; Zheng, Shimin; Zeng, Jianfeng; Duan, Guangxin; Wang, Yong; Wang, Guanglin; Chai, Zhifang; Li, Zhen; Gao, Mingyuan

    2016-07-01

    Ultrasmall biocompatible WO3 - x nanodots with an outstanding X-ray radiation sensitization effect are prepared, and demonstrated to be applicable for multi-modality tumor imaging through computed tomography and photoacoustic imaging (PAI), and effective cancer treatment combining both photothermal therapy and radiation therapy. PMID:27136070

  14. Composite WO3/TiO2 nanostructures for high electrochromic activity

    DOE PAGESBeta

    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 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

  15. UV Photochromic Memory Effect in Proton-Based WO3 Electrochromic Devices

    SciTech Connect

    Zhang, Y.; Lee, S. H.; Mascarenhas, A.; Deb, S. K.

    2008-12-01

    We report an UV photochromic memory effect on a standard proton-based WO{sub 3} electrochromic device. It exhibits two memory states, associated with the colored and bleached states of the device, respectively. Such an effect can be used to enhance device performance (increasing the dynamic range), re-energize commercial electrochromic devices, and develop memory devices.

  16. Adiponectin promotes syncytialisation of BeWo cell line and primary trophoblast cells

    PubMed Central

    2010-01-01

    Background In human pregnancy, a correct placentation depends on trophoblast proliferation, differentiation, migration and invasion. These processes are highly regulated by placental hormones, growth factors and cytokines. Recently, we have shown that adiponectin, an adipokine, has anti-proliferative effects on trophoblastic cells. Here, we complete this study by demonstrating that adiponectin modulates BeWo and human villous cytotrophoblast cell differentiation. Results We showed that hCG secretion was up-regulated by adiponectin treatment in both BeWo cells and human cytotrophoblasts from very early placentas (5-6 weeks). The expression of two trophoblast differentiation markers, leptin and syncytin 2, was also up-regulated by adiponectin in BeWo cells. Moreover, adiponectin treatment induced a loss of E-cadherin staining in these cells. In parallel, we demonstrated that AdipoR1 and AdipoR2 are up-regulated during forskolin induced BeWo cell differentiation, reinforcing the role of adiponectin in trophoblast syncytialization. SiRNA mediated down-regulation of AdipoR1 and AdipoR2 was used to demonstrate that adiponectin effects on differentiation were essentially mediated by these receptors. Finally, using a specific inhibitor, we demonstrated that the PKA signalling pathway could be one pathway involved in adiponectin effects on trophoblast differentiation. Conclusion Adiponectin enhances the differentiation process of trophoblast cells and could thus be involved in functional syncytiotrophoblast formation. PMID:21034435

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

    PubMed

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

    2012-06-01

    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. PMID:22543744

  18. Photoluminescence in CaWO4:Bi3+, Eu3+ Material

    NASA Astrophysics Data System (ADS)

    Pode, R. B.; Dhoble, S. J.

    1997-10-01

    Luminescence of Bi3+ and Bi3+ + Eu3+ in calcium tungstate powder prepared by the solid state diffusion method has been reported. The excitation and emission bands in CaWO4 and CaWO4:Bi3+ coincide and appear at 256 and 430.5 nm, respectively. The 430.5 nm emission band is ten times stronger in the latter case (for 1 mol% Bi3+) than in the former case. The Eu3+ emission was observed at 619 nm in CaWO4:Eu3+<$> (1 mol%). The Eu3+ emission intensity increased significantly (about 37 times) with the addition of a small amount of Bi3+. The emission band of Bi3+ overlaps with the excitation band of Eu3+, resulting in a very efficient energy transfer from Bi3+ to Eu3+. The energy transfer probability is strongly dependent upon the Bi3+ concentration, with a maximum for 0.5 mol% of Bi3+ and drastically decreases for higher concentration. The mechanism of the energy transfer from Bi3+ to Eu3+ has been discussed. The CaWO4:(Bi3+, Eu3+) material is proposed as an efficient red phosphor.

  19. Synthesis of stable hollow silica microspheres with mesoporous shell in nonionic W/O emulsion.

    PubMed

    Li, Wenjiang; Sha, Xiaoxiang; Dong, Wenjun; Wang, Zichen

    2002-10-21

    Stable hollow silica microspheres were synthesized by a solgel method in nonionic W/O emulsion; the mesoporous shell wall of the spheres could have potential applications as controlled release capsules for drugs, dyes, cosmetics and inks, artificial cells, catalysts, and fillers. PMID:12430477

  20. Anodic WO3 mesosponge @ carbon: a novel binder-less electrode for advanced energy storage devices.

    PubMed

    Pervez, Syed Atif; Kim, Doohun; Doh, Chil-Hoon; Farooq, Umer; Choi, Hae-Young; Choi, Jung-Hee

    2015-04-15

    A novel design for an anodic WO3 mesosponge @ carbon has been introduced as a highly stable and long cyclic life Li-ion battery electrode. The nanocomposite was successfully synthesized via single-step electrochemical anodization and subsequent heat treatment in an acetylene and argon gas environment. Morphological and compositional characterization of the resultant materials revealed that the composite consisted of a three-dimensional interconnected network of WO3 mesosponge layers conformally coated with a 5 nm thick carbon layer and grown directly on top of tungsten metal. The results demonstrated that the carbon-coated mesosponge WO3 layers exhibit a capacity retention of 87% after completion of 100 charge/discharge cycles, which is significantly higher than the values of 25% for the crystalline (without carbon coating) or 40% for the as-prepared mesosponge WO3 layers. The improved electrochemical response was attributed to the higher stability and enhanced electrical conductivity offered by the carbon coating layer. PMID:25794310

  1. Facile solvothermal synthesis of NIR absorbing CsxWO3 nanorods by benzyl alcohol route

    NASA Astrophysics Data System (ADS)

    Eyassu, Tsehaye; Hsaio, Tun-Jen; Lin, Chhiu-Tsu

    2015-01-01

    Near infrared absorbing CsxWO3 nanoparticles with uniform particle size distribution were synthesized in two hours by solvothermal method. Benzyl alcohol was used as a main solvent and a reactant to facilitate a controlled reaction and stabilization in the presence of oleic acid as a capping agent. Different reaction conditions such as reaction time, reaction temperature, and oleic acid amount were studied and reported. Hexagonal CsxWO3 nanorods with average size of 80 nm were obtained in 2 h reaction time, at 240 °C reaction temperature, and 10% vol. oleic acid. Aqueous dispersion of the nanorods showed high transparency (about 80-90%) in visible light with strong near infrared (NIR) light shielding (80-90%). This indicates that CsxWO3 is an attractive material to employ in heat-shielding transparent coatings for windows of buildings and automobiles. Using this simple process, it is possible to synthesize homogenous CsxWO3 nanorods with low temperature and short reaction time. Moreover, the process offers an opportunity for large-scale synthesis of NIR absorbing nanorods.

  2. Effect of iron loading on the photocatalytic performance of Bi2WO6 photocatalyst

    NASA Astrophysics Data System (ADS)

    Sriwichai, Surassa; Ranwongsa, Hataikarn; Wetchakun, Khatcharin; Phanichphant, Sukon; Wetchakun, Natda

    2014-12-01

    Pure Bi2WO6 and nominal 0.1-2.0 mol% Fe-loaded Bi2WO6 samples were synthesized by hydrothermal method. All samples were characterized in order to obtain the correlation between structure and photocatalytic properties by X-ray diffraction, UV-vis diffuse reflectance spectrophotometry, Brunauer, Emmett and Teller-specific surface area, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy and inductively coupled plasma-optical emission spectroscopy. Photocatalytic activities of all photocatalyst samples were examined by studying the degradation of methylene blue under visible light irradiation. The 0.5 mol% Fe-loaded Bi2WO6 had the best activity in photodegradation of MB in aqueous solution under visible light irradiation. The high performance of Fe-loaded Bi2WO6 could be attributed to the fact that the Fe ions could act as electron traps promoting the electron-hole separation then enhancing the photocatalytic reaction.

  3. 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.

  4. Fabrication and capacitive characteristics of conjugated polymer composite p-polyaniline/n-WO3 heterojunction

    NASA Astrophysics Data System (ADS)

    Amaechi, C. I.; Asogwa, P. U.; Ekwealor, A. B. C.; Osuji, R. U.; Maaza, M.; Ezema, F. I.

    2014-07-01

    A nanocrystalline and porous p-polyaniline/n-WO3 dissimilar heterojunction at ambient temperature is reported. The high-quality and well-reproducible conjugated polymer composite films have been fabricated by oxidative polymerization of anilinium ion on predeposited WO3 thin film by chemical bath deposition followed by thermal annealing at 573 K for 1 h. Atomic force microscopy (AFM) analyses reveal a homogenous but irregular cluster of faceted spherically shaped grains with pores. The scanning electron microscopy confirms the porous network of grains, which is in good agreement with the AFM result. The optical absorption analysis of polyaniline/WO3 hybrid films showed that direct optical transition exist in the photon energy range 3.50-4.00 eV with bandgap of 3.70 eV. The refractive index developed peak at 445 nm in the dispersion region while the high-frequency dielectric constant, ɛ ∞, and the carrier concentration to effective mass ratio, N/m*, was found to be 1.58 and 1.10 × 1039 cm-3, respectively. The temperature dependence of electrical resistivity of the deposited films follows the semiconductor behavior while the C-V characteristics (Mott-Schottky plots) show that the flat band potential was -791 and 830 meV/SCE for WO3 and polyaniline.

  5. An UV photochromic memory effect in proton-based WO3 electrochromic devices

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Lee, S.-H.; Mascarenhas, A.; Deb, S. K.

    2008-11-01

    We report an UV photochromic memory effect on a standard proton-based WO3 electrochromic device. It exhibits two memory states, associated with the colored and bleached states of the device, respectively. Such an effect can be used to enhance device performance (increasing the dynamic range), re-energize commercial electrochromic devices, and develop memory devices.

  6. A graphene-coupled Bi2WO6 nanocomposite with enhanced photocatalytic performance: a first-principles study.

    PubMed

    Ren, Fengzhu; Zhang, Jihua; Wang, Yuanxu; Yao, Wenzhi

    2016-05-18

    An experimentally synthesized graphene/Bi2WO6 composite showed an enhancement of the visible-light photocatalytic activity, while the underlying mechanism is not known. Here, first-principles calculations based on density functional theory were performed to explore the various properties of the graphene/Bi2WO6(010) composite aiming at gaining insights into the mechanism of its photocatalytic activity. The stability, electronic properties, charge transfer, and visible-light response were investigated in detail on the Bi2WO6(010) surface coupled with graphene. An analysis of charge distribution and Bader charge shows that there is a strong covalent bonding between graphene and the Bi2WO6(010) surface. The covalent interaction induces a small bandgap in graphene. The interband transition of graphene and the surface states of the Bi2WO6(010) surface would cause the absorption spectrum of graphene/Bi2WO6(010) to cover the entire visible-light region and even the infrared-light region. The photogenerated electrons flow to graphene from the conduction band of Bi2WO6 under the built-in electric field and band edge potential well. Thus, graphene serves as a photogenerated electron collector and transporter which significantly reduces the probability of electron-hole recombination and increases catalytic reaction sites not only on the surface of graphene but on also the surface of Bi2WO6. The decrease of charge recombination is possibly responsible for the enhancement of the visible-light photocatalytic activity of the graphene/Bi2WO6(010) nanocomposite. PMID:27156737

  7. 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. PMID:23993423

  8. Recent genome reduction of Wolbachia in Drosophila recens targets phage WO and narrows candidates for reproductive parasitism

    PubMed Central

    Metcalf, Jason A.; Jo, Minhee; Bordenstein, Sarah R.; Jaenike, John

    2014-01-01

    Wolbachia are maternally transmitted endosymbionts that often alter their arthropod hosts’ biology to favor the success of infected females, and they may also serve as a speciation microbe driving reproductive isolation. Two of these host manipulations include killing males outright and reducing offspring survival when infected males mate with uninfected females, a phenomenon known as cytoplasmic incompatibility. Little is known about the mechanisms behind these phenotypes, but interestingly either effect can be caused by the same Wolbachia strain when infecting different hosts. For instance, wRec causes cytoplasmic incompatibility in its native host Drosophila recens and male killing in D. subquinaria. The discovery of prophage WO elements in most arthropod Wolbachia has generated the hypothesis that WO may encode genes involved in these reproductive manipulations. However, PCR screens for the WO minor capsid gene indicated that wRec lacks phage WO. Thus, wRec seemed to provide an example where phage WO is not needed for Wolbachia-induced reproductive manipulation. To enable investigation of the mechanism of phenotype switching in different host backgrounds, and to examine the unexpected absence of phage WO, we sequenced the genome of wRec. Analyses reveal that wRec diverged from wMel approximately 350,000 years ago, mainly by genome reduction in the phage regions. While it lost the minor capsid gene used in standard PCR screens for phage WO, it retained two regions encompassing 33 genes, several of which have previously been associated with reproductive parasitism. Thus, WO gene involvement in reproductive manipulation cannot be excluded and reliance on single gene PCR should not be used to rule out the presence of phage WO in Wolbachia. Additionally, the genome sequence for wRec will enable transcriptomic and proteomic studies that may help elucidate the Wolbachia mechanisms of altered reproductive manipulations associated with host switching, perhaps among

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. Structural, Electrical and Magnetic Properties of Pb2Mg1-xCoxWO6 Solid Solutions

    NASA Astrophysics Data System (ADS)

    Ardelean, I.; Barbur, I.; Timar, V.; Borodi, Gh.

    X-ray diffraction, electrical and magnetic measurements performed on Pb2Mg1-xCoxWO6 solid solutions with 0≤x≤1 are reported. By cobalt substitution for magnesium the diffraction patterns indicate the transition from orthorhombic structure characteristics for Pb2MgWO6 to the cubic structure specific for Pb2CoWO6. The Curie temperature decreases with cobalt content from 38°C to 32°C. The magnetic data indicate that the cobalt ions are in a bivalent state and, for x>0.1, experience negative magnetic interactions.

  15. 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.

  16. Magnetron Sputtering of Gold Nanoparticles onto WO3 and Activated Carbon

    SciTech Connect

    Veith, Gabriel M; Lupini, Andrew R; Pennycook, Stephen J; Villa, Alberto; Prati, Laura; Dudney, Nancy J

    2007-01-01

    In this paper we describe the production and investigation of two supported gold catalyst systems prepared by magnetron sputtering: Au on WO3 and Au on activated carbon. The magnetron sputtering technique entails the sputtering of a high purity gold metal target, with an argon plasma, to produce a flux of gold atoms onto a constantly tumbling support material. This technique offers a number of advantages over conventional chemical preparation methods including the flexibility to create gold nanoparticles (diameters < 3 nm) on unusual support materials, such as WO3 and carbon, which are generally not accessible using the ubiquitous deposition-precipitation technique. We present data demonstrating the formation of catalytic gold nanoparticles with average diameters of 1.7 nm (Au/C) and 2.1 nm (Au/WO3) as well as a substantial number of single atom species on the Au/C sample. Prototypical carbon monoxide oxidation (Au/WO3) and glycerol oxidation (Au/C) reactions were performed in order to gauge the activity of these catalysts. The WO3 supported catalyst exhibits substantial catalytic activity from room temperature to 135oC (0.0018 - 0.082 mole CO/mole Au sec) with an apparent transition around 75oC to a more active catalyst. The activity 1 of the Au/C catalysts was compared to a Au/C catalysts prepared from a PVA sol. The smaller catalysts prepared by sputtering are more active than the large gold particles prepared using the PVA sol. However, the larger gold catalyst are substaintially more selective towards the production of intermediate products from the oxidation of glycerol.

  17. 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.

  18. 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.

  19. Synthesis and characterization of F-doped Cs0.33WO3-xFx particles with improved near infrared shielding ability

    NASA Astrophysics Data System (ADS)

    Liu, Jingxiao; Luo, Jiayu; Shi, Fei; Liu, Suhua; Fan, Chuanyan; Xu, Qiang; Shao, Guolin

    2015-01-01

    F-doped Cs0.33WO3-xFx 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 Cs0.33WO3-xFx nanoparticles in polyvinyl alcohol (PVA) aqueous solution. The effects of F doping on the crystal structure and morphology of Cs0.33WO3-xFx particles as well as the near-infrared (NIR) shielding ability and heat insulation properties of Cs0.33WO3-xFx films were investigated. The results indicated that HF acid addition could promote the formation of rod-like Cs0.33WO3-xFx particles during hydrothermal synthesis and increase the yield of Cs0.33WO3-xFx powders. Moreover, the as-prepared films from dispersion solution of Cs0.33WO3-xFx particles exhibited higher near-infrared (NIR) shielding ability and heat insulating properties than that of the undoped Cs0.33WO3 film. Particularly, the as-prepared Cs0.33WO3-xFx 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 Cs0.33WO3-xFx products were discussed.

  20. 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

  1. A CsxWO3/ZnO nanocomposite as a smart coating for photocatalytic environmental cleanup and heat insulation

    NASA Astrophysics Data System (ADS)

    Wu, Xiaoyong; Yin, Shu; Xue, Dongfeng; Komarneni, Sridhar; Sato, Tsugio

    2015-10-01

    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.

  2. THE DISCOVERY OF A RARE WO-TYPE WOLF-RAYET STAR IN THE LARGE MAGELLANIC CLOUD

    SciTech Connect

    Neugent, Kathryn F.; Massey, Philip; Morrell, Nidia E-mail: phil.massey@lowell.edu

    2012-12-01

    While observing OB stars within the most crowded regions of the Large Magellanic Cloud, we happened upon a new Wolf-Rayet (WR) star in Lucke-Hodge 41, the rich OB association that contains S Doradus and numerous other massive stars. At first glance the spectrum resembled that of a WC4 star, but closer examination showed strong O VI {lambda}{lambda}3811, 34 lines, leading us to classify it as a WO4. This is only the second known WO in the LMC, and the first known WO4 (the other being a WO3). This rarity is to be expected due to these stars' short lifespans as they represent the most advanced evolutionary stage in a massive star's lifetime before exploding as supernovae. This discovery shows that while the majority of WRs within the LMC have been discovered, there may be a few WRs left to be found.

  3. Crystal quality and optical property of MnWO4 nanoparticles synthesized by microwave-assisted method

    NASA Astrophysics Data System (ADS)

    Van Hanh, Pham; Huy Hoang, Luc; Van Hai, Pham; Van Minh, Nguyen; Chen, Xiang-Bai; Yang, In-Sang

    2013-03-01

    MnWO4 nanoparticles were prepared using a microwave-assisted method followed by low-temperature treatment. The crystal quality and optical property of the MnWO4 nanoparticles were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and ultraviolet-visible (UV-vis) absorption spectroscopy. Our results show that good crystal quality MnWO4 nanoparticles can be prepared by the microwave-assisted method, and best crystal quality nanoparticles can be obtained with synthesizing pH value of 7. Furthermore, by calcination treatments, crystal quality can be further improved with less defect states and the particle size increases when the calcining temperature increases from 150 to 600 °C. In addition, our study shows that the MnWO4 nanoparticles have strong absorption in the visible light region, suggesting that these nanoparticles are promising for photocatalytic applications.

  4. 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.

  5. Study on luminescent properties of Eu3+ doped Gd2WO6, Gd2W2O9 and Gd2(WO4)3 nanophosphors prepared by co-precipitation.

    PubMed

    Meng, Qingyu; Hua, Ruinian; Chen, Baojiu; Tian, Yue; Lu, Shuchen; Sun, Linan

    2011-01-01

    Eu3+ doped Gd2WO6, Gd2W2O9 and Gd2(WO4)3 nanophosphors with different concentrations have been prepared by co-precipitation. XRD (X-ray diffraction) and SEM (scanning electron microscopy) were used to investigate the structure and morphology. The emission spectra, excitation spectra and fluorescence decay curves were measured, and partial J-O parameters and quantum efficiencies of Eu3+ 5D0 energy level were calculated. Furthermore, concentration quenching curves of Eu3+ in different hosts were drawn. The photoluminescent properties of Eu3+ doped Gd2WO6, Gd2W2O9 and Gd2(WO4)3 nanophosphors have been studied. The results indicate that Eu3+ 5D0-7F2 red luminescence can be effectively excited by 395 nm and 465 nm in Gd2WO6 and Gd2W2O9 hosts, similar to the familiar Gd2(WO4)3:Eu. Especially Gd2W2O9:Eu has strong red emission and high quenching concentration, so it has potential applications for trichromatic white LED as red fluorescent materials. PMID:21446424

  6. 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.

  7. 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.

  8. Understanding the conductive channel evolution in Na:WO3-x-based planar devices

    NASA Astrophysics Data System (ADS)

    Shang, Dashan; Li, Peining; Wang, Tao; Carria, Egidio; Sun, Jirong; Shen, Baogen; Taubner, Thomas; Valov, Ilia; Waser, Rainer; Wuttig, Matthias

    2015-03-01

    An ion migration process in a solid electrolyte is important for ion-based functional devices, such as fuel cells, batteries, electrochromics, gas sensors, and resistive switching systems. In this study, a planar sandwich structure is prepared by depositing tungsten oxide (WO3-x) films on a soda-lime glass substrate, from which Na+ diffuses into the WO3-x films during the deposition. The entire process of Na+ migration driven by an alternating electric field is visualized in the Na-doped WO3-x films in the form of conductive channel by in situ optical imaging combined with infrared spectroscopy and near-field imaging techniques. A reversible change of geometry between a parabolic and a bar channel is observed with the resistance change of the devices. The peculiar channel evolution is interpreted by a thermal-stress-induced mechanical deformation of the films and an asymmetric Na+ mobility between the parabolic and the bar channels. These results exemplify a typical ion migration process driven by an alternating electric field in a solid electrolyte with a low ion mobility and are expected to be beneficial to improve the controllability of the ion migration in ion-based functional devices, such as resistive switching devices.An ion migration process in a solid electrolyte is important for ion-based functional devices, such as fuel cells, batteries, electrochromics, gas sensors, and resistive switching systems. In this study, a planar sandwich structure is prepared by depositing tungsten oxide (WO3-x) films on a soda-lime glass substrate, from which Na+ diffuses into the WO3-x films during the deposition. The entire process of Na+ migration driven by an alternating electric field is visualized in the Na-doped WO3-x films in the form of conductive channel by in situ optical imaging combined with infrared spectroscopy and near-field imaging techniques. A reversible change of geometry between a parabolic and a bar channel is observed with the resistance change of the

  9. Discovery of a new Wolbachia supergroup in cave spider species and the lateral transfer of phage WO among distant hosts.

    PubMed

    Wang, Guan-Hong; Jia, Ling-Yi; Xiao, Jin-Hua; Huang, Da-Wei

    2016-07-01

    Wolbachia are widespread intracellular bacteria infecting the major classes of arthropods and some filarial nematodes. In arthropods, Wolbachia have evolved various intriguing reproductive manipulations, including cytoplasmic incompatibility, parthenogenesis, feminization, and male killing. Sixteen supergroups of Wolbachia have been identified, named A-Q (except G). Though Wolbachia present great diversity in arthropods, spiders, especially cave spiders, are still a poorly surveyed group of Wolbachia hosts. Here, we report a novel Wolbachia supergroup from nine Telema cave spiders (Araneae: Telemidae) based on five molecular markers (16S rRNA, ftsZ, gltA, groEL, and coxA). In addition, phage WO, which was previously reported only in Wolbachia supergroups A, B, and F, infects this new Wolbachia supergroup. We detected a 100% infection rate for phage WO and Wolbachia in Telema species. The phylogenetic trees of phage WO and Wolbachia are not congruent, which suggests that horizontal transfer of phage WO has occurred in these secluded species. Additionally, these data indicate Telema-Wolbachia-phage WO may be a good model for exploring the horizontal transfer history of WO among different host species. PMID:26997548

  10. Rapid sonochemical synthesis of irregular nanolaminar-like Bi2WO6 as efficient visible-light-active photocatalysts.

    PubMed

    Zhang, Feng-Jun; Xie, Fa-Zhi; Liu, Jin; Zhao, Wei; Zhang, Kan

    2013-01-01

    Irregular Bi(2)WO(6) nanolaminars have been successfully synthesized via a rapid sonochemical approach using bismuth nitrate and tungstic acid as precursors in an aqueous solution. The characteristics of them were investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N(2) adsorption, pore value, PL spectroscopy and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). These irregular nanolaminars are of geometric shapes of orthorhombic Bi(2)WO(6) with their basal plane being (001). They possess high crystallinity, lager surface area and pore value, which means fewer traps and stronger photocatalytic activity. The growth mechanism of such special nanolaminar was related to the sonochemical synthesis route, which played a key role in the formation of Bi(2)WO(6) nanolaminar. Simultaneously, it was found that the formation of Bi(2)WO(6) nanolaminar is a time dependent process. The Bi(2)WO(6) nanolaminar has higher photocatalytic activity than bulk Bi(2)WO(6) nanoparticle obtained by refluxing method for rhodamine B (Rh.B) degradation under visible light irradiation (λ>400 nm). PMID:22925548

  11. 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.

  12. 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.

  13. Tuning of crystal phase structure in hydrated WO3 nanoparticles under wet chemical conditions and studies on their photochromic properties

    NASA Astrophysics Data System (ADS)

    Songara, Sandhya; Gupta, Vatsana; Kumar Patra, Manoj; Singh, Jitendra; Saini, Lokesh; Siddaramana Gowd, Genekehal; Raj Vadera, Sampat; Kumar, Narendra

    2012-07-01

    Hydrated tungsten oxide nanoparticles have been synthesized using a simple wet chemical method while varying the concentration of HCl. XRD studies show that the variation in HCl concentration from 1 M to 6 M in the reaction results into gradual change in crystal structure of hydrated WO3 from hexagonal (WO3·0.33H2O) to pure orthorhombic (WO3·H2O), through a series of samples with mixed phase of the two indifferent ratios. The similar variations in the degree of hydration and phase variations have also been observed from Raman, FTIR and TGA studies. The average crystallite size of the hydrated WO3 particles was estimated to be ∼26 nm from XRD line broadening and AFM studies showed the formation of spherical shaped particles for all the samples. The photochromic studies were carried out on the composite films of these materials in the polymeric matrix of polyvinyl alcohol (PVA) while exposing to UV light. The composite films show interesting variations in the photochromic behavior depending on the crystal structure of hydrated WO3 filler. The photochromic behavior has been explained on the basis of EPR spectra of hydrated WO3.

  14. Enhancement of gas-sensing abilities in p-type ZnWO4 by local modification of Pt nanoparticles.

    PubMed

    Li, Cong; Liang, Yanqin; Mao, Jing; Ling, Lan; Cui, Zhenduo; Yang, Xianjin; Zhu, Shengli; Li, Zhaoyang

    2016-07-13

    Semiconducting ZnWO4 nanorods and nanoparticles are synthesized by adjusting the composition of the reaction solvent. The effect of Pt nanoparticles on the sensing property of ZnWO4 nanostructures were evaluated and investigated systemically in the first time. Pure ZnWO4 nanostructures exhibited the highest sensitivity towards ethanol against Volatile Organic Compounds (methanol, acetone). Their lower limit of detection can reach 100 ppm for ethanol at temperature of about 23 °C. Pt nanoparticles play a positive effect in improving the sensitivity of ZnWO4 towards H2. After loading of Pt nanoparticles, the response of ZnWO4 nanorods towards 1.5% H2 increased from 1.4 to 12.5 at room temperature. In addition, the structure exhibits more significant promoting effect than nanoparticle structure because of their different microstructure and exposed crystallographic planes. Furthermore, Pt nanoparticles could eliminate the effect of ambient humidity to avoid the baseline shift. The gas sensing mechanism of PtZnWO4 nanocomposites is discussed detailedly at the same time. The generation of Schottky barrier at the interface between metal and semiconductor, as well as the formation of PtO on the surface of Pt nanoparticles contribute to the enhanced sensing response. PMID:27237843

  15. CuWO4 Nanoflake Array-Based Single-Junction and Heterojunction Photoanodes for Photoelectrochemical Water Oxidation.

    PubMed

    Ye, Wen; Chen, Fengjiao; Zhao, Feipeng; Han, Na; Li, Yanguang

    2016-04-13

    Over recent years, tremendous efforts have been invested in the search and development of active and durable semiconductor materials for photoelectrochemical (PEC) water splitting, particularly for photoanodes operating under a highly oxidizing environment. CuWO4 is an emerging candidate with suitable band gap and high chemical stability. Nevertheless, its overall solar-to-electricity remains low because of the inefficient charge separation process. In this work, we demonstrate that this problem can be partly alleviated through designing three-dimensional hierarchical nanostructures. CuWO4 nanoflake arrays on conducting glass are prepared from the chemical conversion of WO3 templates. Resulting electrode materials possess large surface areas, abundant porosity and small thickness. Under illumination, our CuWO4 nanoflake array photoanodes exhibit an anodic current density of ∼0.4 mA/cm(2) at the thermodynamic potential of water splitting in pH 9.5 potassium borate buffer - the largest value among all available CuWO4-based photoanodes. In addition, we demonstrate that their performance can be further boosted to >2 mA/cm(2) by coupling with a solution-cast BiVO4 film in a heterojunction configuration. Our study unveils the great potential of nanostructured CuWO4 as the photoanode material for PEC water oxidation. PMID:27011376

  16. Gas-sensing properties and complex impedance analysis of Ce-added WO 3 nanoparticles to VOC gases

    NASA Astrophysics Data System (ADS)

    Luo, Shijun; Fu, Gang; Chen, Huan; Liu, Zhiyu; Hong, Qiusan

    2007-06-01

    Nano-scaled tungsten-trioxide (WO 3) powder has been synthesized by sol-gel process using tungsten powders. The effect of cerium oxide (CeO 2) additive on the gas response of the samples was investigated, especially to the volatile organic compound (VOC) gases, and significant enhancement was achieved. The highest gas response of Ce-added WO 3 samples was found to shift to lower temperatures, compared to the pure WO 3 ones. The analysis with field-emission SEM reveals that grain boundary is pinned due to adding CeO 2, which results in decrease in the average grain size of Ce-added WO 3 and increase in the surface area, compared with the pure WO 3 ones. Complex impedance spectroscopy analysis indicates that grain boundary resistance increases and grain boundary capacitance decreases with the increasing concentration of CeO 2. It means that the Ce ions exist mainly in the WO 3 grain boundaries and helps to improve the microstructure.

  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. PMID:26728087

  18. 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.

  19. Surface modification of TiO₂ nanocrystals by WO(x) coating or wrapping: solvothermal synthesis and enhanced surface chemistry.

    PubMed

    Epifani, Mauro; Díaz, Raül; Force, Carmen; Comini, Elisabetta; Manzanares, Marta; Andreu, Teresa; Genç, Aziz; Arbiol, Jordi; Siciliano, Pietro; Faglia, Guido; Morante, Joan R

    2015-04-01

    TiO2 anatase nanocrystals were prepared by solvothermal processing of Ti chloroalkoxide in oleic acid, in the presence of W chloroalkoxide, with W/Ti nominal atomic concentration (R(w)) ranging from 0.16 to 0.64. The as-prepared materials were heat-treated up to 500 °C for thermal stabilization and sensing device processing. For R(0.16), the as-prepared materials were constituted by an anatase core surface-modified by WO(x) monolayers. This structure persisted up to 500 °C, without any WO3 phase segregation. For R(w) up to R(0.64), the anatase core was initially wrapped by an amorphous WO(x) gel. Upon heat treatment, the WO(x) phase underwent structural reorganization, remaining amorphous up to 400 °C and forming tiny WO3 nanocrystals dispersed into the TiO2 host after heating at 500 °C, when part of tungsten also migrated into the TiO2 structure, resulting in structural and electrical modification of the anatase host. The ethanol sensing properties of the various materials were tested and compared with pure TiO2 and WO3 analogously prepared. They showed that even the simple surface modification of the TiO2 host resulted in a 3 orders of magnitude response improvement with respect to pure TiO2. PMID:25775118

  20. The interface transport of V 2O 5 and WO 3 into CaMo(W)O 4 stimulated by an electric field

    NASA Astrophysics Data System (ADS)

    Guseva, A.; Neiman, A.; Konisheva, E.; Trifonova, M.; Gorbunova, E.

    2002-06-01

    An electric field applied to the CaWO 4/V 2O 5, CaMoO 4/V 2O 5 and CaMoO 4/WO 3 systems causes grain boundary and surface transports of oxides having a low surface energy (V 2O 5 and WO 3) and their segregation on the grain surface. It was found that V 2O 5 penetrates to the inner surface of CaWO 4 much more intensively when the V 2O 5 briquette bears a negative potential: (-)V 2O 5|CaWO 4(+). The penetration of V 2O 5 and WO 3 to the inner surface of the CaMoO 4 ceramic is accompanied by a chemical interaction.

  1. 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. PMID:26218199

  2. 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. PMID:26576930

  3. G0W0 band structure of CdWO4.

    PubMed

    Laasner, Raul

    2014-03-26

    The full quasiparticle band structure of CdWO4 is calculated within the single-shot GW (G0W0) approximation using maximally localized Wannier functions, which allows one to assess the validity of the commonly used scissor operator. Calculations are performed using the Godby-Needs plasmon pole model and the accurate contour deformation technique. It is shown that while the two methods yield identical band gap energies, the low-lying states are given inaccurately by the plasmon pole model. We report a band gap energy of 4.94 eV, including spin-orbit interaction at the DFT-LDA (density functional theory-local density approximation) level. Quasiparticle renormalization in CdWO4 is shown to be correlated with localization distance. Electron and hole effective masses are calculated at the DFT and G0W0 levels. PMID:24599225

  4. Influence of MoO3 addition on the gasochromism of WO3 thin films

    NASA Astrophysics Data System (ADS)

    Zhang, Zenghai; Wu, Guangming; Gao, Guohua; Wu, Jiandong; Feng, Wei

    2011-02-01

    Pure tungsten oxide thin films apparently show gasochromic performance, based on PdCl2 catalyst. In this paper, adulteration of MoO3 into WO3 sol has been achieved via sol-gel method. FT-IR, Differential Scanning Calorimeter (DSC-TG) and Uv-visible Spectroscopy have been used to analysis the compound sols, films and optical properties for the use of this material as smart windows. FT-IR shows that for the compound, new characteristic absorption bands arise, which is different from pure WO3 or MoO3. DSC-TG shows the phase change during the temperature ascending from 50 to 800°C. The compound thin films performs relatively well in coloring response time, colored extent, coloring-bleaching recycling and gasochromic effect with non-unicity color.

  5. Influence of MoO3 addition on the gasochromism of WO3 thin films

    NASA Astrophysics Data System (ADS)

    Zhang, Zenghai; Wu, Guangming; Gao, Guohua; Wu, Jiandong; Feng, Wei

    2010-10-01

    Pure tungsten oxide thin films apparently show gasochromic performance, based on PdCl2 catalyst. In this paper, adulteration of MoO3 into WO3 sol has been achieved via sol-gel method. FT-IR, Differential Scanning Calorimeter (DSC-TG) and Uv-visible Spectroscopy have been used to analysis the compound sols, films and optical properties for the use of this material as smart windows. FT-IR shows that for the compound, new characteristic absorption bands arise, which is different from pure WO3 or MoO3. DSC-TG shows the phase change during the temperature ascending from 50 to 800°C. The compound thin films performs relatively well in coloring response time, colored extent, coloring-bleaching recycling and gasochromic effect with non-unicity color.

  6. Formation of W/O microemulsion based on natural glycolipid biosurfactant, mannosylerythritol lipid-a.

    PubMed

    Worakitkanchanakul, Wannasiri; Imura, Tomohiro; Morita, Tomotake; Fukuoka, Tokuma; Sakai, Hideki; Abe, Masahiko; Rujiravanit, Ratana; Chavadej, Sumaeth; Kitamoto, Dai

    2008-01-01

    Mannosylerythritol lipid-A (MEL-A) is a glycolipid biosurfactant abundantly produced from soybean oil by microorganisms at a yield of up to 100 g/L. In this study, the formation of water-in-oil (W/O) microemulsion based on the single component of MEL-A was confirmed using dynamic light scattering (DLS) and freeze fracture electron microscopy (FF-EM). DLS and FF-EM measurements revealed that the diameter of the microemulsion increases with an increase in water-to-surfactant mole ratio (W(0)) ranging from 20 to 60 nm, and the maximum W(0) value was found to be 20, which is as high as that of soybean lecithin. Glycolipid biosurfactant has a great potential for the formation of W/O microemulsion without using any cosurfactants. PMID:18075224

  7. Precipitation Synthesis, Characterization, Morphological Control, and Photocatalyst Application of ZnWO4 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Hosseinpour-Mashkani, S. Mostafa; Maddahfar, Mahnaz; Sobhani-Nasab, Ali

    2016-04-01

    Zinc tungstate nanoparticles have been successfully synthesized by a precipitation method in the presence of different polymeric surfactants. This study aimed to investigate the effect of different solvents and polymeric surfactants such as carboxymethyl cellulose, polyethylene glycol, and polyvinyl alcohol on the morphology, particle size, and crystal structure of the final product. The as-synthesized products were characterized by powder x-ray diffraction analysis, scanning electron microscopy, ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, transmission electron microscopy, and energy-dispersive x-ray spectroscopy techniques. Furthermore, the hysteresis loop of the zinc tungstate nanoparticles at room temperature revealed paramagnetic behavior. Photocatalysis results revealed that maximum methyl orange decolorization of 85% was achieved with ZnWO4 nanoparticles in 240 min under visible-light irradiation. The saturation magnetization, remanent magnetization, and coercivity of the ZnWO4 nanoparticles were 0.003 emu/g, 0.0005 emu/g, and 110 Oe, respectively.

  8. Surfactant-assistant solvothermal synthesis of CaWO4:Eu3+ phosphors and luminescence

    NASA Astrophysics Data System (ADS)

    Xu, Huanzhi; Ying, Dongming; Lu, Ading; Wang, Xiaoyan; Hu, Jiankun

    2015-07-01

    CaWO4:Eu3+ phosphors with different morphologies were synthesized by the surfactant-assistant solvothermal process. The structure and luminescent properties were characterized by XRD, SEM, TEM, IR, XPS, and spectrophotometer. The XRD and IR results show that the samples have the scheelite phase. The XPS result shows that Eu3+ ions have doped into CaWO4 hosts successfully. PEG-400, En, and EDTA play the key roles in the formation of microspheres with smooth surface, microspheres with rough surface, and microoctahedrons, respectively. All samples show emission bands originating from the 5D0 → 7Fj (j = 1, 2, 3, 4) transitions of Eu3+ ions. The morphology has obvious influence on the emission intensity. The microspheres with smooth surface have the highest emission intensity, and the microoctahedrons have the lowest emission intensity.

  9. Precipitation Synthesis, Characterization, Morphological Control, and Photocatalyst Application of ZnWO4 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Hosseinpour-Mashkani, S. Mostafa; Maddahfar, Mahnaz; Sobhani-Nasab, Ali

    2016-07-01

    Zinc tungstate nanoparticles have been successfully synthesized by a precipitation method in the presence of different polymeric surfactants. This study aimed to investigate the effect of different solvents and polymeric surfactants such as carboxymethyl cellulose, polyethylene glycol, and polyvinyl alcohol on the morphology, particle size, and crystal structure of the final product. The as-synthesized products were characterized by powder x-ray diffraction analysis, scanning electron microscopy, ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, transmission electron microscopy, and energy-dispersive x-ray spectroscopy techniques. Furthermore, the hysteresis loop of the zinc tungstate nanoparticles at room temperature revealed paramagnetic behavior. Photocatalysis results revealed that maximum methyl orange decolorization of 85% was achieved with ZnWO4 nanoparticles in 240 min under visible-light irradiation. The saturation magnetization, remanent magnetization, and coercivity of the ZnWO4 nanoparticles were 0.003 emu/g, 0.0005 emu/g, and 110 Oe, respectively.

  10. Phonon properties of nanosized MnWO 4 with different size and morphology

    NASA Astrophysics Data System (ADS)

    Mączka, MirosŁaw; Ptak, Maciej; Kurnatowska, Michalina; Kępiński, Leszek; Tomaszewski, PaweŁ; Hanuza, Jerzy

    2011-09-01

    Highly hierarchical barlike and flowerlike MnWO 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 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.

  11. Segmented CdWO4 detector for low background experiments at DUSEL

    NASA Astrophysics Data System (ADS)

    Mei, Dongming; Sun, Yongchen; Day, Alyssa; Thomas, Keenan; Perevozchikov, Oleg

    2010-11-01

    We propose to develop a segmented CdWO4 scintillator array for detecting geo-neutrinos, neutrinoless double-beta, and dark matter. The detection of geo-neutrinos can shed light on the sources of the terrestrial heat flow, on the present composition, and on the origins of the Earth. The development of a new technique to detect geo-neutrinos through charge current antineutrino capture processes on ^106Cd is very interesting. This target allows us to detect all of geo-neutrinos from uranium, thorium, and potassium decays. When it is built, the detector can be also used to detect neutrinoless double-beta decay with ^116Cd. Both enriched ^106Cd and ^116Cd can be used to search for dark matter from the Universe. This paper will present RD results on the energy response of gamma-rays and neutrons from three small CdWO4 detectors.

  12. Phase modification and surface plasmon resonance of Au/WO3 system

    NASA Astrophysics Data System (ADS)

    Bose, R. Jolly; Kavitha, V. S.; Sudarsanakumar, C.; Pillai, V. P. Mahadevan

    2016-08-01

    We report the action of gold as catalyst for the modification of phase from triclinic WO3 to monoclinic W18O49 and nucleation centre for the formation of W18O49 phase, in gold incorporated tungsten oxide films prepared by RF magnetron sputtering technique. A new band is observed near 925 cm-1 in the Raman spectra of gold incorporated tungsten oxide films which is not observed in the pure tungsten oxide film. The intensity of this band enhances with gold content. A localized surface plasmon resonance (LSPR) band is observed near the wavelength 604 nm in gold incorporated tungsten oxide films. The integrated intensities of LSPR band and Raman band (∼925 cm-1) can be used for sensing the quantity of gold in the Au/WO3 matrix.

  13. Hierarchical nanostructured WO3-SnO2 for selective sensing of volatile organic compounds

    NASA Astrophysics Data System (ADS)

    Nayak, Arpan Kumar; Ghosh, Ruma; Santra, Sumita; Guha, Prasanta Kumar; Pradhan, Debabrata

    2015-07-01

    It remains a challenge to find a suitable gas sensing material that shows a high response and shows selectivity towards various gases simultaneously. Here, we report a mixed metal oxide WO3-SnO2 nanostructured material synthesized in situ by a simple, single-step, one-pot hydrothermal method at 200 °C in 12 h, and demonstrate its superior sensing behavior towards volatile organic compounds (VOCs) such as ammonia, ethanol and acetone. SnO2 nanoparticles with controlled size and density were uniformly grown on WO3 nanoplates by varying the tin precursor. The density of the SnO2 nanoparticles on the WO3 nanoplates plays a crucial role in the VOC selectivity. The responses of the present mixed metal oxides are found to be much higher than the previously reported results based on single/mixed oxides and noble metal-doped oxides. In addition, the VOC selectivity is found to be highly temperature-dependent, with optimum performance obtained at 200 °C, 300 °C and 350 °C for ammonia, ethanol and acetone, respectively. The present results on the cost-effective noble metal-free WO3-SnO2 sensor could find potential application in human breath analysis by non-invasive detection.It remains a challenge to find a suitable gas sensing material that shows a high response and shows selectivity towards various gases simultaneously. Here, we report a mixed metal oxide WO3-SnO2 nanostructured material synthesized in situ by a simple, single-step, one-pot hydrothermal method at 200 °C in 12 h, and demonstrate its superior sensing behavior towards volatile organic compounds (VOCs) such as ammonia, ethanol and acetone. SnO2 nanoparticles with controlled size and density were uniformly grown on WO3 nanoplates by varying the tin precursor. The density of the SnO2 nanoparticles on the WO3 nanoplates plays a crucial role in the VOC selectivity. The responses of the present mixed metal oxides are found to be much higher than the previously reported results based on single/mixed oxides and

  14. In situ microscopy of rapidly heated nano-Al and nano-Al/WO3 thermites

    NASA Astrophysics Data System (ADS)

    Sullivan, Kyle T.; Chiou, Wen-An; Fiore, Richard; Zachariah, Michael R.

    2010-09-01

    The initiation and reaction mechanism of nano-Al and nano-Al thermites in rapid heating environments is investigated in this work. A semiconductor-based grid/stage was used, capable of in situ heating of a sample from room temperature to 1473 K, and at a rate of 106 K/s, inside an electron microscope. Nano-Al was rapidly heated in a transmission electron microscope, and before and after images indicate that the aluminum migrates through the shell, consistent with a diffusion-based mechanism. A nano-Al/WO3 composite was then heated in a scanning electron microscope. The results indicate that a reactive sintering mechanism is occurring for the nano-Al/WO3 thermite, as the products are found to be in surface contact and significantly deformed after the heating pulse.

  15. First principles study of the photo-oxidation of water on tungsten trioxide (WO3).

    PubMed

    Valdés, A; Kroes, G-J

    2009-03-21

    The photo-oxidation of water on the monoclinic P2(1)/nWO(3) (200, 020, and 002) surfaces is investigated using density functional theory calculations, employing the PW91-generalized gradient approximation, and the method developed by Norskov et al. [J. Phys. Chem. B 108, 17886 (2004)] based on the free energy differences between the reaction intermediates. We first relax the bulk material unit cell and then investigate the relative stability of different surface terminations of WO(3) and analyze the overpotential needed for the photoelectrolysis of water. We found that the rate limiting step is the transfer of a proton from the surface adsorbed OH to the electrolyte, and that the computed overpotential for O(2) evolution (1.04 V) is available upon illumination of the surface with visible light. PMID:19317549

  16. 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.

  17. Radiation damage of PbWO 4 crystals due to irradiation by 60Co gamma rays

    NASA Astrophysics Data System (ADS)

    Kozma, Peter; Bajgar, Robert; Kozma, Petr

    2002-09-01

    Radiation resistivity of large tungstate crystals PbWO 4 from three suppliers has been studied for doses 10 4 Gy (10 6 rad) and 10 5 Gy (10 7 rad). Radiation resistivity was examined by the measurement of optical transmission through tungstate crystals before and after 60Co gamma-ray irradiations. The absolute degradation of transmission for 10 4 and 10 5 Gy doses at 480 nm wavelength of the peak emission of PbWO 4 doped with La 2+, was found to be lower than 12.3% and 14.2%, respectively. The results have been also compared with radiation hardness measurements for a large volume CeF 3 scintillation crystal. Complete recovery of radiation damage was observed between 10 and 15 days after irradiations.

  18. 'Pseudo-proper' ferroelectric phase transitions in oxyfluoride K3WO3F3

    NASA Astrophysics Data System (ADS)

    Ivliev, M. P.; Misyul, S. V.; Molokeev, M. S.; Sakhnenko, V. P.

    2014-06-01

    Based on the structural data on the phases of cryolite (ordered perovskite) K3WO3F3, we develop a statistical model, which allows to describe the sequence of phase transitions observed in this compound using a unified approach. According to the model, the crystal possesses two structural subsystems: the K cations located in the octahedral positions and the WO3F3 octahedra in positions alternating with K cations. In the symmetric (cubic) phase, each subsystem can be found in one of the eight states. At decreasing temperature, an orientational phase transition in the subsystem of octahedra occurs first, followed by a phase transition to the low-temperature phase, caused by the loss of stability with respect to the ordering in the K cation subsystem. We find that the electric polarization occurs as pseudoproper and discuss the mechanisms of formation of the phase states.

  19. Structural and optical properties of WO3 electrochromic layers prepared by the sol-gel method

    NASA Astrophysics Data System (ADS)

    Novinrooz, Abdoljavad; Sharbatdaran, Masoomeh; Noorkojouri, Hassan

    2005-09-01

    Thin layers of tungsten trioxide have been prepared from an aqueous solution of peroxotungstic acid (PTA) using the sol-gel method. Compositional, structural and optical characteristics of WO3 coated on indium tin oxide (ITO) conductive glass substrates were studied using X-ray diffractometery (XRD), cyclic voltammetery (CV), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Monoclinic and triclinic crystalline structures for thin film and powdered WO3 were confirmed by XRD analysis. SEM micrograph of annealed samples revealed micro cracks due to a decrease in density and a contraction of layers. EDX analysis showed that 1∶2 ratio of oxygen and tungsten atoms in the prepared films is obtained at heat treatment temperatures higher than 200 °C. Furthermore, the annealed samples showed very good electrochromic behavior in cyclic voltammetery studies. Refractive index "n" and extinction coefficient "k" values were found to be reduced by increasing the wavelength and decreasing the temperature.

  20. 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. PMID:27244429

  1. Highly transparent Bi2MoO6- and Bi2WO6-polymer nanocomposites.

    PubMed

    Wollmann, P; Grothe, J; Ziegler, C; Kaskel, S

    2011-04-01

    A combined method of precipitation, phase transfer into organic solvent, solvothermal treatment and subsequent in situ polymerization was used to integrate nanocrystalline Bi2MoO6- and Bi2WO6-particles into a polymer matrix of poly-laurylacrylate. The presented method offers a new and gentle way to produce highly transparent bulk nanocomposites containing evenly distributed Bi2MoO6- and Bi2WO6-nanoparticles. Characterization results of DLS-, XRD-, REM- and TEM-measurements are presented as well as solid state UV/VIS-measurements of the particles. The transparent nanocomposites were characterized using UV/VIS-spectroscopy and ellipsometry. All composites show a good transmission in the range from 800-400 nm. The particle content of the nanocomposites was measured with TG-measurements. PMID:21776724

  2. Intense ultraviolet emission from needle-like WO3 nanostructures synthesized by noncatalytic thermal evaporation

    PubMed Central

    2011-01-01

    Photoluminescence measurements showed that needle-like tungsten oxide nanostructures synthesized at 590°C to 750°C by the thermal evaporation of WO3 nanopowders without the use of a catalyst had an intense near-ultraviolet (NUV) emission band that was different from that of the tungsten oxide nanostructures obtained in other temperature ranges. The intense NUV emission might be due to the localized states associated with oxygen vacancies and surface states. PMID:21752275

  3. 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.

  4. Enhanced long-wavelength transient photoresponsiveness of WO3 induced by tellurium doping.

    PubMed

    Yang, Bin; Luca, Vittorio

    2008-10-01

    Tungsten trioxide (WO3) films doped with 0.25 atom% tellurium synthesised by a sol-gel route, show strong transient photocurrents under chopped sub-bandgap illumination (hnu=1.8 eV

  5. 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. PMID:27107232

  6. 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.

  7. Formaldehyde Polymerization on (WO3)3/TiO2(110) Model Catalyst

    SciTech Connect

    Kim, Jooho; Kay, Bruce D.; Dohnalek, Zdenek

    2010-10-14

    Polymerization of formaldehyde, H2CO, was studied under ultrahigh vacuum conditions on a model catalyst consisting of monodispersed (WO3)3 clusters anchored on TiO2(110. Formaldehyde oligomers, (H2CO)n, desorbing from the polymer that formed on the catalyst surface are detected between 250 and 325 K in temperature programmed desorption experiments. At least two monolayers (ML) of H2CO are required on the surface to observe (H2CO)n desorption and the amount saturates for H2CO coverages in excess of ~30 ML. The presence of H2CO multilayers is required for the polymerization to take place indicating that it had to occur below 100 K. The saturation amount increases with increasing coverage of (WO3)3 clusters with the highest amount of ~13 ML observed on 1.2 (WO3)3/nm2 . No (H2CO)n desorption was observed on the bare TiO2(110) surface.

  8. WO3-x Nanoplates Grown on Carbon Nanofibers for an Efficient Electrocatalytic Hydrogen Evolution Reaction.

    PubMed

    Chen, JiaDong; Yu, DanNi; Liao, WeiSha; Zheng, MengDan; Xiao, LongFei; Zhu, Han; Zhang, Ming; Du, MingLiang; Yao, JuMing

    2016-07-20

    The search for non-noble metal catalysts with high activity for the hydrogen evolution reaction (HER) is crucial for efficient hydrogen production at low cost and on a large scale. Herein, we report a novel WO3-x catalyst synthesized on carbon nanofiber mats (CFMs) by electrospinning and followed by a carbonization process in a tubal furnace. The morphology and composition of the catalysts were tailored via a simple method, and the hybrid catalyst mats were used directly as cathodes to investigate their HER performance. Notably, the as-prepared catalysts exhibit substantially enhanced activity for the HER, demonstrating a small overpotential, a high exchange current density, and a large cathodic current density. The remarkable electrocatalytic performances result from the poor crystallinity of WO3-x, the high electrical conductivity of WO3-x, and the use of electrospun CNFs. The present work outlines a straightforward approach for the synthesis of transition metal oxide (TMO)-based carbon nanofiber mats with promising applications for the HER. PMID:27356101

  9. Upconversion emission properties and tunable morphologies of Y6WO12:Yb3+/Er3+ phosphor

    NASA Astrophysics Data System (ADS)

    Xue, Bing; Sun, Jiayue

    2014-01-01

    Yb3+/Er3+ co-doped Y6WO12 phosphors are prepared by hydrothermal method and subsequently calcination. According to tuning the EDTA usage, the phosphors present four morphologies (cylinder, short-cylinder, flower-like and triangle shape). It is found that the usage of EDTA play crucial role in the formation of morphology. Based on the DSC-TG curves, the pure Y6WO12 are obtained by annealing the precursors at a wide range of temperatures. After annealing, strong red emissions and weak green emissions are observed under 980 nm excitation, which is different from the uncalcined products (green emissions are stronger than red emissions). Then we studied the changing tendency of the upconversion (UC) luminescence properties of the calcined and uncalcined products. At last, the pumping power on the UC luminescence properties and the level diagram mechanism of Y6WO12:Yb3+/Er3+ phosphor have also been discussed. We think this work may have the guiding function for obtaining different morphologies by adjusting EDTA and provide new channel of changing the green to red ratio in these kinds of host.

  10. 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).

  11. 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

    2013-03-01

    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. PMID:23348367

  12. 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.

  13. Understanding the conductive channel evolution in Na:WO(3-x)-based planar devices.

    PubMed

    Shang, Dashan; Li, Peining; Wang, Tao; Carria, Egidio; Sun, Jirong; Shen, Baogen; Taubner, Thomas; Valov, Ilia; Waser, Rainer; Wuttig, Matthias

    2015-04-14

    An ion migration process in a solid electrolyte is important for ion-based functional devices, such as fuel cells, batteries, electrochromics, gas sensors, and resistive switching systems. In this study, a planar sandwich structure is prepared by depositing tungsten oxide (WO(3-x)) films on a soda-lime glass substrate, from which Na(+) diffuses into the WO(3-x) films during the deposition. The entire process of Na(+) migration driven by an alternating electric field is visualized in the Na-doped WO(3-x) films in the form of conductive channel by in situ optical imaging combined with infrared spectroscopy and near-field imaging techniques. A reversible change of geometry between a parabolic and a bar channel is observed with the resistance change of the devices. The peculiar channel evolution is interpreted by a thermal-stress-induced mechanical deformation of the films and an asymmetric Na(+) mobility between the parabolic and the bar channels. These results exemplify a typical ion migration process driven by an alternating electric field in a solid electrolyte with a low ion mobility and are expected to be beneficial to improve the controllability of the ion migration in ion-based functional devices, such as resistive switching devices. PMID:25766380

  14. 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.

  15. 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.

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

    PubMed

    Clark, Andrea J; Petty, Howard R

    2016-02-19

    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. PMID:26788907

  17. 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.

  18. Competitive Oxidation and Reduction of Aliphatic Alcohols over (WO3)3 Clusters

    SciTech Connect

    Kim, Yu K.; Dohnalek, Zdenek; Kay, Bruce D.; Rousseau, Roger J.

    2009-06-04

    The reactions of C1 to C4 aliphatic alcohols over (WO3)3 clusters were studied experimentally and theoretically using temperature-programmed desorption, infrared reflection-absorption spectroscopy and density functional theory. The results reveal that all C1 to C4 aliphatic alcohols readily react with (WO3)3 clusters by heterolytic cleavage of the RO-H bond to give alkoxy (RO ) bound to W(VI) centers and a proton (H+) attached to the terminal oxygen atom of a tungstyl group (W=O). Two protons adsorbed onto the cluster readily react with the doubly-bonded oxygen to from a water molecule that desorbs at 200-300 K and the alkoxy that undergoes decomposition at higher temperatures into the corresponding alkene, aldehyde, and/or ether. Our theory predicts that all three channels proceed over the W(VI) Lewis acid site with energy barriers of 30-40 kcal/mol, where dehydration is favored over the others. We also present further analysis of the yield and reaction temperature as a function of the alkyl substituents and discuss the origin of the reaction selectivity among the three reaction channels.

  19. 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)

  20. 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. PMID:27262854

  1. 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.

  2. 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.

  3. Generation of WO{sub 3}-ZrO{sub 2} catalysts from solid solutions of tungsten in zirconia

    SciTech Connect

    Cortes-Jacome, Maria A.; Angeles-Chavez, Carlos; Bokhimi, Xim; Toledo-Antonio, J.A. . E-mail: jtoledo@imp.mx

    2006-08-15

    WO{sub 3}-ZrO{sub 2} samples were obtained by precipitating zirconium oxynitrate in presence of WO{sub 4} {sup =} species in solution from ammonium metatungstate at pH=10.0. Samples were characterized by atomic absorption spectroscopy, thermal analysis, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy and energy filtered-TEM. The ammonia retained in the dried sample produced a reductive atmosphere to generate W{sup 5+} ions coexisting with W{sup 6+} ions to produce a solid solution of tungsten in the zirconia lattice to stabilize the zirconia tetragonal phase when the sample was annealed at 560 deg. C. When the sample was annealed at 800 deg. C, the W atoms near crystallite surface were oxidized to W{sup 6+}, producing patches of WO{sub 3} on the zirconia crystallite. The HR-TEM analysis confirmed the existence of the solid solution when the sample was annealed at 560 deg. C, and two types of crystalline regions were identified: One with nearly spherical morphology, an average diameter of 8 nm and the atomic distribution of tetragonal zirconia. The second one had a non-spherical morphology with well-faceted faces and dimensions larger than 30 nm, and the atom distribution of tetragonal zirconia. When samples were annealed at 800 deg. C two different zirconia crystallites were formed: Those where only part of the dissolved tungsten atoms segregated to crystallite surface producing patches of nanocrystalline WO{sub 3} on the crystallite surface of tetragonal zirconia stabilized with tungsten. The second type corresponded to monoclinic zirconia crystallites with patches of nanocrystalline WO{sub 3} on their surface. The tungsten segregation gave rise to the WO{sub 3}-ZrO{sub 2} catalysts. - Graphical abstract: WO {sub x} -ZrO{sub 2} catalysts were obtained by precipitating zirconium oxynitrate in presence of WO{sub 4} {sup =}species. Initially, the W atoms remained inside the crystallite after

  4. Improvement of Performance and Stability of Polymer Photovoltaic Cells by WO3/CUPC as Anode Buffer Layers

    NASA Astrophysics Data System (ADS)

    Varnamkhasti, M. G.; Shahriaria, E.

    2015-05-01

    In this work, bulk-hetrojunction polymer photovoltaic cells based on poly-(3-hexylthiophene) (P3HT): [6,6]-phenyl C61 butyric acid methyl ester (PCBM) were fabricated with tungsten oxide (WO3) and copper phthalocyanine (CuPc) as anodic buffer layers. The WO3 plays an important role in reducing the interfacial resistance, efficiently extracting holes and good band structure matching between the work function of the anode and the highest occupied molecular orbital of the organic material. The insertion of CuPc improves the device In this work, bulk-hetrojunction polymer photovoltaic cells based on poly-(3-hexylthiophene) (P3HT): [6, 6]-phenyl C61 butyric acid methylester (PCBM) were fabricated with tungsten oxide (WO3) and copper phthalocyanine (CuPc) as anodic buffer layers. The WO3 plays animportant role in reducing the interfacial resistance, efficiently extracting holes and good band structure matching between the workfunction of the anode and the highest occupied molecular orbital of the organic material. The insertion of CuPc improves the device performance and expands the absorption spectra range of the photovoltaic devices. The effects of WO3 and CuPc thickness on the performance of the photovoltaic devices were investigated. The optimum thicknesses of WO3 and CuPc were 10 nm and 8 nm, respectively. The obtained power conversion efficiency of optimized cell was about 4.21%. Also, the device performance was analyzed based on thesurface roughness of bare ITO and ITO that was covered with poly (3, 4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT:PSS) or WO3/CuPc. The device stability in an ambient atmosphere without encapsulation under continuous light irradiation was also investigated.For the cell with PEDOT:PSS, the power conversion efficiency reduced down to 50% of the maximum value (half-life) after light irradiation for 12 h, while the half-life of device for WO3/CuPc was about 120 h. Therefore, the lifetime of unpackaged devices was improved with

  5. Electrochromic coloration efficiency of a-WO[sub 3[minus]y] thin films as a function of oxygen deficiency

    SciTech Connect

    Lee, S.; Cheong, H.M.; Tracy, C.E.; Mascarenhas, A.; Czanderna, A.W.; Deb, S.K. )

    1999-09-01

    We report on how electrochromic coloration is affected by oxygen deficient stoichiometries in sputtered amorphous tungsten oxide (a-WO[sub 3[minus]y]) films. The electrochromic coloration efficiency increases with increasing oxygen deficiency in (a-WO[sub 3[minus]y]) films. No coloration is observed in nearly stoichiometric WO[sub 3] films. Raman spectroscopic studies reveal that the number of W[sup 5+] states generated with lithium insertion increases with the oxygen deficiency. Furthermore, there are no Raman peaks resulting from W[sup 5+] states in lithiated a-WO[sub 3[minus]y] films with near perfect stoichiometry, which is consistent with the absence of electrochromic coloration in those films. We conclude that the coloration efficiency of a-WO[sub 3[minus]y] films depends on the number of the W[sup 5+] states generated by lithium insertion and that the oxygen deficiency plays an important role in generating the W[sup 5+] states with lithium insertion. [copyright] [ital 1999 American Institute of Physics.

  6. Kinetics Study on Reduction of CaWO4 by Si from 1423 K to 1523 K

    NASA Astrophysics Data System (ADS)

    Shu, Qifeng; Wu, Jing; Chou, Kuochih

    2015-12-01

    Investigation on reduction kinetics of scheelite(CaWO4) provides important fundamental knowledge to control and optimize process of Ferrotungsten manufacturing and direct reduction of scheelite in steelmaking. In this work, the isothermal reduction kinetics of CaWO4 powder by Si powder at 1,423 K, 1,473 K and 1,523 K, where all reactants and products are in solid state, was investigated by using X-ray diffraction quantitative analysis. Scanning electronic microscopy (SEM) attached with energy dispersive spectra (EDS) was also employed to investigate the microstructure of reaction interface. Both Jander model and Ginstling-Brounshtein model could describe kinetics of reduction of CaWO4 well, whereas 3D interfacial reaction model could not describe the kinetics of reduction of CaWO4. The rate determining step for reduction of CaWO4 could be diffusion of Si across product layer. The values of activation energies obtained by fitting kinetic data using Jander and Ginstling-Brounshtein model are as great as 379.93 kJ/mol and 387.16 kJ/mol respectively. The oxygen partial pressure during reduction has impact on the kinetics of reduction. The reduction was retarded by increase of oxygen partial pressure.

  7. 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

  8. 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.

  9. 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.

  10. Hydrogen sensing properties of nanostructured Pd/WO3 thin films: role of hydrophobicity during recovery process

    NASA Astrophysics Data System (ADS)

    Jain, S.; Sanger, A.; Chauhan, S.; Chandra, R.

    2014-09-01

    In the present work the structural, optical and hydrogen sensing properties of Pd-capped tungsten oxide (Pd/WO3) thin films have been investigated. The nanostructured Pd/WO3 thin films have been prepared using DC magnetron sputtering on glass and Si(100) substrates at various oxygen partial pressures. The samples were hydrogenated at 2 bar hydrogen pressure in an operating temperature range 300-423 K. Optical transmittance spectra confirms fully transparent WO3 thin films deposited at oxygen partial pressure of 0.5 Pa while the transmittance drastically decreases to 50% for hydrogenated Pd/WO3 thin films. The influence of surface roughness and hydrophobicity of the Pd/WO3 thin films on the hydrogen sensing performance have been studied. Fast response time (1 sec) and an optimum recovery time (˜8 min) have been observed at a moderate temperature of 323 K for the samples having roughness ˜4.5 nm and contact angle ˜96°. Hydrophobicity of the surface provides short recovery time by opposing the existence of water-vapour on the surface.

  11. 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. PMID:27109698

  12. Synergistic WO3·2H2O Nanoplates/WS2 Hybrid Catalysts for High-Efficiency Hydrogen Evolution.

    PubMed

    Yang, Lun; Zhu, Xiaobin; Xiong, Shijie; Wu, Xinglong; Shan, Yun; Chu, Paul K

    2016-06-01

    Tungsten trioxide dihydrate (WO3·2H2O) nanoplates are prepared by in situ anodic oxidation of tungsten disulfide (WS2) film on carbon fiber paper (CFP). The WO3·2H2O/WS2 hybrid catalyst exhibits excellent synergistic effects which facilitate the kinetics of the hydrogen evolution reaction (HER). The electrochromatic effect takes place via hydrogen intercalation into WO3·2H2O. This process is accelerated by the desirable proton diffusion coefficient in the layered WO3·2H2O. Hydrogen spillover from WO3·2H2O to WS2 occurs via atomic polarization caused by the electric field of the charges on the planar defect or edge active sites of WS2. The optimized hybrid catalyst presents a geometrical current density of 100 mA cm(-2) at 152 mV overpotential with a Tafel slope of ∼54 mV per decade, making the materials one of the most active nonprecious metal HER catalysts. PMID:27211828

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

    PubMed

    Vuong, Nguyen Minh; 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

  14. 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.

  15. Photoelectrochemical properties and the detection mechanism of Bi2WO6 nanosheet modified TiO2 nanotube arrays.

    PubMed

    Pang, Yajun; Xu, Guangqing; Zhang, Xu; Lv, Jun; Shi, Kai; Zhai, Pengbo; Xue, Qianyun; Wang, Xuedong; Wu, Yucheng

    2015-10-28

    Bi2WO6 nanosheet modified TiO2 nanotube arrays were synthesized by an anodization method combined with sequential chemical bath deposition for enhancement of the photoelectrochemical detection performance. The structures, morphologies and elemental compositions of the nanotube arrays were characterized with X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectrometry. Bi2WO6 nanosheets were successfully deposited on the tube walls of TiO2 nanotubes. The photoelectrochemical property of Bi2WO6/TiO2 NTAs was determined with chronoamperometry and cyclic voltammetry using an electrochemical workstation equipped with a UV LED light (365 nm). The optimum detection sensitivity of glucose in water was determined to be 0.244 μA mM(-1) in the linear range from 0 to 2500 μM. Bi2WO6 modification on TiO2 NTAs simultaneously decreased the background photocurrent and increased the current response to organics, resulting in the enhancement of photoelectrochemical detection properties. Mechanisms of the Bi2WO6 modification are discussed by analyzing the photoelectrochemical processes, including optical absorption, charges transfer and surface electrochemical reactions. Direct oxidation by holes rather than indirect oxidation by ˙OH radicals is believed to be a key role in this enhancement. PMID:26400480

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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.

  17. Iron-doping-enhanced photoelectrochemical water splitting performance of nanostructured WO3: a combined experimental and theoretical study.

    PubMed

    Zhang, Teng; Zhu, Zonglong; Chen, Haining; Bai, Yang; Xiao, Shuang; Zheng, Xiaoli; Xue, Qingzhong; Yang, Shihe

    2015-02-21

    In this paper, we have studied Fe-doping of nanostructured tungsten trioxide (WO3) and its pronounced effect in promoting the photoelectrochemical (PEC) water splitting performance. Vertically aligned Fe-doped WO3 nanoflakes on fluorine-doped tin oxide (FTO) were synthesized via the hydrothermal method. An X-ray photoelectron spectroscopy (XPS) analysis confirmed the Fe(3+) substitution at the W(6+) site in the prepared films. Broadened visible light absorption was observed in doped films, likely due to the formation of extra band states through doping. The Fe-doping was shown to greatly improve the PEC water splitting performance of WO3. More specifically, the 2 mol% Fe-doped WO3 achieved a photocurrent density of 0.88 mA cm(-2) at 1.23 V versus RHE, approximately 30% higher than that of the undoped WO3 (0.69 mA cm(-2) at 1.23 V versus RHE). This enhancement was attributed to the reduced band gap and the doping-enhanced charge carrier density as confirmed by the absorption spectra and the Mott-Schottky plots, respectively. Finally, first-principles density functional theory (DFT) calculations confirmed that the formation of oxygen vacancies was favored after Fe-doping, contributing to the increased charge carrier density in slightly doped films. PMID:25587830

  18. Enhancement of the photoelectrochemical performance of CuWO4 films for water splitting by hydrogen treatment

    NASA Astrophysics Data System (ADS)

    Tang, Yulin; Rong, Nannan; Liu, Feila; Chu, Mengsha; Dong, Hongmei; Zhang, Yunhuai; Xiao, Peng

    2016-01-01

    CuWO4 films with feature particle sizes of 100-200 nm and thickness up to 700-900 nm on fluorine-doped tin oxide (FTO) substrates were prepared by hydrothermal synthesis. The prepared CuWO4 films were treated in hydrogen atmosphere at constant temperature 300 °C for different annealing time and used for photoelectrochemical (PEC) water oxidation. Compared with pristine CuWO4 film, the optimized hydrogen-treated CuWO4 film presented three times enhanced photocurrent density of 0.75 mA/cm2 at 1.2 V vs. Ag/AgCl in 0.1 M Na2SO4 solution under the illumination. The donor density of hydrogenated CuWO4 film determined by Mott-Schottky analysis was improved one order of magnitude as well. The enhanced photoelectrochemical activity could be attributed to the formation of oxygen vacancies after hydrogen treatment, which facilitated the charge transport and collection.

  19. Coaxial electrospinning of WO3 nanotubes functionalized with bio-inspired Pd catalysts and their superior hydrogen sensing performance.

    PubMed

    Choi, Seon-Jin; Chattopadhyay, Saptarshi; Kim, Jae Jin; Kim, Sang-Joon; Tuller, Harry L; Rutledge, Gregory C; Kim, Il-Doo

    2016-04-28

    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. PMID:26691720

  20. 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.

  1. Dispersion of Cs0.33WO3 particles for preparing its coatings with higher near infrared shielding properties

    NASA Astrophysics Data System (ADS)

    Liu, Jingxiao; Xu, Qiang; Shi, Fei; Liu, Suhua; Luo, Jiayu; Bao, Lei; Feng, Xiang

    2014-08-01

    In order to achieve good dispersion of Cs0.33WO3 particles and improve their near-infrared (NIR) shielding efficiency, the influences of ball-milling and dispersant on the dispersion stability of Cs0.33WO3 particles and its near infrared shielding properties were investigated. The microstructure, morphology, particle size distribution and Zeta potential of the particle samples were characterized by XRD, SEM and laser particle size analyzer. The results indicate that adding appropriate dispersant after ball-milling is conducive to dispersion of Cs0.33WO3 powders. Polyvinyl alcohol and titanate coupling agent have better effects on the dispersion of Cs0.33WO3 colloidal solution than poly-carboxylic salt dispersant. Particularly, the as-prepared Cs0.33WO3 coatings prepared from colloidal dispersion solution using titanate coupling agent at pH = 7 showed best visible light transmittance and near-infrared shielding properties, and have great potential applications as thermal insulation coatings for building and automotive glasses.

  2. 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.

  3. Enhanced photoelectrocatalytic performance of Zn-doped WO(3) photocatalysts for nitrite ions degradation under visible light.

    PubMed

    Cheng, X F; Leng, W H; Liu, D P; Zhang, J Q; Cao, C N

    2007-08-01

    WO(3) and Zn-doped WO(3) thin films were prepared on indium-tin oxide glass by a dip-coating. The composite films were characterized by UV-Vis absorption spectra, X-ray diffraction and scanning electron microscope. The effect of preparation conditions (concentration of Zn, annealing temperature, number of layers) on the photocurrent was studied. It was found that the photocurrent under visible light displayed the highest value for 2% Zn-WO(3) films annealed at 400 degrees C. The photocatalytic activity of the Zn-doped WO(3) was evaluated in terms of decay rate of nitrite ions under visible light. The influence of applied potential, initial pH and nitrite concentration on the reaction rate was studied. The experiments demonstrated that NO(2)(-) could be efficiently degraded on the doped photoanode that showed a higher activity than the undoped WO(3) especially under high anodic potential (>0.7 V). The rate of degradation was enhanced in aqueous NaCl solutions. Furthermore, it was demonstrated that the photodegradation mechanism of NO(2)(-) proceeded mainly indirectly via OH radicals. The possible reason of enhancement of reaction rate was also discussed. PMID:17482660

  4. 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

  5. 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).

  6. High-Quality Draft Genome Sequence of Arthrobacter sp. OY3WO11, a Strain That Inhibits the Growth of Phytophthora infestans

    PubMed Central

    Town, Jennifer; Audy, Patrice; Boyetchko, Susan M.

    2016-01-01

    Arthrobacter sp. strain OY3WO11 inhibits the growth of the potato pathogen Phytophthora infestans in in vivo growth challenge assays. We determined the draft genome sequence of this strain, assembling it into 3 scaffolds of 4.2 Mbp total length. OY3WO11 may represent a novel species of Arthrobacter. PMID:27340067

  7. 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. PMID:24819429

  8. 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.

  9. A novel approach to electrochromism in WO{sub 3} thin film using piezoelectric ceramics for power supply

    SciTech Connect

    Xu, C.N.; Akiyama, M.; Sun, P.; Watanabe, T.

    1997-03-01

    Electrochromism was newly realized in a WO{sub 3}{endash}Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} (PZT) system which utilized the piezoelectric property of PZT ceramics for power supply. The electric power produced by Mn-doped PZT ceramics enabled the WO{sub 3} film to color blue. High piezoelectricity with a peak voltage of 35 V and peak current of 1.2 mA on a 30 k{Omega} circuit was observed at a pressure of 30 MPa for the present system. This study shows the possibility to actuate the electrochromic WO{sub 3} film with PZT ceramics. {copyright} {ital 1997 American Institute of Physics.}

  10. Synthesis and photocatalytic properties of ZnWO4 nanocrystals via a fast microwave-assisted method.

    PubMed

    Yan, Jing; Shen, Yanhua; Li, Feng; Li, Taohai

    2013-01-01

    High crystallinity of ZnWO4 nanoparticles has been successfully synthesized via a highly effective and environmentally friendly microwave route by controlling the reaction time and temperature. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and Fourier infrared spectrum (FT-IR). The crystallinity was enhanced with the increase of the reaction temperature and time. The photocatalytic activities of ZnWO4 nanocrystals were evaluated by testing the photodegradation of rhodamine B (RhB) dye under ultraviolet (UV) light irradiation. The results indicated that as-prepared ZnWO4 was highly effective for the degradation of RhB. The degradation rate of RhB reached 98.01% after 6 h of UV illumination. PMID:23818822

  11. NO and NO2 sensing properties of WO3 and Co3O4 based gas sensors.

    PubMed

    Akamatsu, Takafumi; Itoh, Toshio; Izu, Noriya; Shin, Woosuck

    2013-01-01

    Semiconductor-based gas sensors that use n-type WO3 or p-type Co3O4 powder were fabricated and their gas sensing properties toward NO2 or NO (0.5-5 ppm in air) were investigated at 100 °C or 200 °C. The resistance of the WO3-based sensor increased on exposure to NO2 and NO. On the other hand, the resistance of the Co3O4-based sensor varied depending on the operating temperature and the gas species. The chemical states of the surface of WO3 or those of the Co3O4 powder on exposure to 1 ppm NO2 and NO were investigated by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. No clear differences between the chemical states of the metal oxide surface exposed to NO2 or NO could be detected from the DRIFT spectra. PMID:24048338

  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. 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

    2009-01-01

    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

  14. Execution of energy efficient detection of hydrogen using Pt/WO x /SiC semiconductor structure

    NASA Astrophysics Data System (ADS)

    Zuev, V. V.; Demin, M. V.; Fominskii, V. Yu.; Romanov, R. I.; Grigor'ev, V. V.; Nevolin, V. N.

    2015-09-01

    It has been shown that, at elevated temperatures (˜350°C), the most distinct response to H2 from the thin film structure Pt/WO x /SiC is achieved at registration of change in voltage for the reverse branch of a current-voltage characteristic. Comparative studies of electric current conduction through the structure and over its surface (with deposited Pt film) have led to the conclusion that a change in properties of the Pt/WO x and WO x /SiC interfaces under action of H2 mostly determines efficiency of response of the structure in the case of "transverse" measuring geometry. In the case of a 2% concentration of H2 in air the voltage shift for the reverse branch at a current of ˜10 μA reached 5 V against 2 V on the forward branch and "planar" geometry of measurements.

  15. 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.

  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. Ultraviolet to near-infrared downconversion in Yb3+-Na+ codoped Sr2CaWO6

    NASA Astrophysics Data System (ADS)

    Li, Yong; Li, XuZhi; Wei, XianTao; Li, ZhongYuan; Chen, Hongmei; Wang, WenMing; Zhao, Wei; Ji, Yuexia

    2016-07-01

    This study investigated photoluminescent properties of Sr2CaWO6:Yb3+, Na+ phosphor. The samples were successfully synthesized via a solid-state reaction method with various doping concentrations. The phosphor can efficiently absorb ultraviolet photons of 250-350 nm and transfer its absorbed photon energy to Yb3+ ions. Then subsequent quantum cutting between WO6 groups and Yb3+ ions takes place, down-converting an absorbed ultraviolet photon into two photons of 1007 nm radiations. Analyses of decay curves of different samples reveal an efficient energy transfer from WO6 groups to Yb3+ ions. Cooperative energy transfer from host to Yb3+ ions is responsible for downconversion via lifetime analysis. Quantum efficiencies were calculated, and estimated maximum efficiency reached 190%. These phosphors combine wide wavelength absorption in the ultraviolet range with high quantum efficiency, enabling potential application of efficiency enhancement of Si solar cell.

  18. 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.

  19. Influence of chemical substitution on the photoluminescence of Sr(1-x)PbxWO4 solid solution

    NASA Astrophysics Data System (ADS)

    Hallaoui, A.; Taoufyq, A.; Arab, M.; Bakiz, B.; Benlhachemi, A.; Bazzi, L.; Villain, S.; Valmalette, J.-C.; Guinneton, F.; Gavarri, J.-R.

    2015-07-01

    The solid solution Sr1-xPbxWO4 based on luminescent tungstates SrWO4 and PbWO4 has been synthesized by solid-state reaction for all compositions 0≤x≤1. Using Rietveld method, the structural data of all polycrystalline samples have been refined and crystal cell parameters exhibited a linear behavior as a function of x. All substituted structures are of scheelite type. Scanning electron microscopy showed that a high level of crystallization characterized the samples, with modifications in sizes and shapes depending on composition x. Infrared and Raman spectroscopy have been performed to characterize the evolution of vibrational modes with substitution rate. Finally, a systematic study of luminescence under X-ray excitation has been performed: in the composition range x=0.2 to 0.4, intensities of emission exhibited increased values. The luminescence profiles have been interpreted in terms of four Gaussian components, two of them depending on substitution rate.

  20. 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.

  1. A green route for microwave synthesis of sodium tungsten bronzes Na xWO 3 (0< x<1)

    NASA Astrophysics Data System (ADS)

    Guo, Juan; Dong, Cheng; Yang, Lihong; Fu, Guangcai

    2005-01-01

    A green route has been developed for microwave synthesis of sodium tungsten bronzes Na xWO 3 (0< x<1) from Na 2WO 4, WO 3 and tungsten powder. The hybrid microwave synthesis was carried out in argon atmosphere using CuO powder as the heating medium. Tungsten powder is used as the reducing agent instead of the alkali metal iodides previously used for the microwave synthesis of oxide bronzes. The prepared samples were characterized by powder X-ray diffraction, energy-dispersive X-ray analysis and scanning electron microscopy, and their phase constitutions, crystal structures and morphologies are in consistence with that in the literature. This synthesis method is simple, green and atom economic, and promising for preparation of other oxide bronzes and related compounds.

  2. NO and NO2 Sensing Properties of WO3 and Co3O4 Based Gas Sensors

    PubMed Central

    Akamatsu, Takafumi; Itoh, Toshio; Izu, Noriya; Shin, Woosuck

    2013-01-01

    Semiconductor-based gas sensors that use n-type WO3 or p-type Co3O4 powder were fabricated and their gas sensing properties toward NO2 or NO (0.5–5 ppm in air) were investigated at 100 °C or 200 °C. The resistance of the WO3-based sensor increased on exposure to NO2 and NO. On the other hand, the resistance of the Co3O4-based sensor varied depending on the operating temperature and the gas species. The chemical states of the surface of WO3 or those of the Co3O4 powder on exposure to 1 ppm NO2 and NO were investigated by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. No clear differences between the chemical states of the metal oxide surface exposed to NO2 or NO could be detected from the DRIFT spectra. PMID:24048338

  3. Diode-pumped 2 μm vibronic (Tm3+, Yb3+):KLu(WO4)2 laser.

    PubMed

    Segura, Martha; Mateos, Xavier; Pujol, Maria Cinta; Carvajal, Joan Josep; Aguiló, Magdalena; Díaz, Francesc; Griebner, Uwe; Petrov, Valentin

    2012-05-10

    We report on laser operation in a (6 at. % Tm, 5 at. % Yb):KLu(WO4)2 codoped crystal. The vibrational frequencies of KLu(WO4)2 are coupled to the electronic transitions of Tm3+ at 1946 nm, creating virtual final laser levels at higher energy than the ground level 3H6 of Tm3+. The longest recorded laser wavelength was 2039 nm, which is longer than permitted by a pure electronic transition in Tm3+ ions in KLu(WO4)2. We show that every laser wavelength can be explained with the electron-phonon coupling effect, where the vibration frequencies were determined through Raman spectroscopy. PMID:22614492

  4. Synthesis and vibrational characterization of KLa(WO4)2 crystalline powders by modified pechini method

    NASA Astrophysics Data System (ADS)

    Rasu, K. Kavi; Durairajan, A.; Balaji, D.; Babu, S. Moorthy

    2013-06-01

    KLa(WO4)2 crystalline powders were synthesized by modified Pechini method using metal nitrates as starting materials, citric acid and ethylene glycol were used as chelating and binding agents respectively. Synthesized gel was pre-fired at 250°C and calcined at 700°C using resistive furnace in air. The properties of the high temperature calcined powders were characterized by powder XRD, FT-IR, and Raman analysis to understand the crystalline nature, organic liberation, and tungstate ribbon formation respectively. Powder XRD confirms the tetragonal structure of the synthesized KLa(WO4)2 powders. Organic liberation from the samples was analyzed using FT-IR. Different vibrational modes of W-O bonds in higher frequency region were observed in Raman spectrum.

  5. 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+). PMID:27549400

  6. Upconversion of SrWO4:Er3+/Yb3+: Improvement by Yb3+ codoping and temperature sensitivity for optical temperature sensors

    NASA Astrophysics Data System (ADS)

    Wei, Zhen; Zheng, Wei; Zhu, Zhiyong; Guo, Xiongfei

    2016-05-01

    SrWO4:Er3+/Yb3+ phosphors are synthesized by a solid state reaction. The XRD patterns indicate that the doping ions will not change the phase of SrWO4. Under the excitation at 980 nm, SrWO4:Er3+/Yb3+ phosphors show emission bands in green and red regions. The temperature-dependence of upconversion efficiency and temperature-sensing properties of SrWO4:Er3+/Yb3+ phosphors have been discussed according to the fluorescence intensity ratio of green emissions from 2H11/2/4S3/2 → 4I15/2 transitions of Er3+ in the range of 95-775 K under the excitation at 980 nm. The maximum sensitivity of SrWO4:1%Er3+/6%Yb3+ phosphor is found to be 0.01282 K-1 at 489 K.

  7. 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.

  8. Fabrication and properties of a branched (NH₄)xWO₃ nanowire array film and a porous WO3 nanorod array film.

    PubMed

    Liu, Ya; Zhao, Liang; Su, Jinzhan; Li, Mingtao; Guo, Liejin

    2015-02-18

    We describe the successful fabrication of a three-dimensional branched (NH4)xWO3 nanowire array film on fluorine-doped tin oxide coated glass by a facile one-step hydrothermal method. The porous WO3 nanorod array film formed after heat treatment and recrystallization. Specifically, the branched (NH4)xWO3 nanowire array film has very thin nanowires that were about 10 nm in diameter. The results of an optical and photoelectrochemical test show that the branched (NH4)xWO3 nanowire array film could be used as a near-infrared shielder, while the porous WO3 nanorod array film can be used as a photoanode for water splitting. Moreover, the morphology, structure, and composition of the as-prepared films are revealed, and the related changes caused by heat treatment are discussed in detail. PMID:25623076

  9. 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).

  10. Progesterone Inhibits Leptin-Induced Invasiveness of BeWo Cells

    PubMed Central

    Jo, Yun Sung; Lee, Gui Se Ra; Nam, Sun Young; Kim, Sa Jin

    2015-01-01

    Background: This study investigated the roles of progesterone and leptin in placenta invasion, which is closely related to pregnancy prognosis. We examined the effects of leptin and progesterone on the invasion of BeWo cells, a human trophoblastic cell line, and the effect of concurrent treatment. Methods: Cells were treated with leptin (0, 5, 50, or 500 ng/mL) or progesterone (0, 2, 20, or 200 µM) and cultured in an invasion assay. Cells treated with 500 ng/mL leptin were also treated with progesterone (0, 2, 20, or 200 µM) in the invasion assay for 48 h. The number of cells that invaded the lower surface was counted in five randomly chosen fields using a light microscope with a 200× objective. The mRNA expression levels of MMP-9, TIMP1, TIMP2, and E-cadherin were detected by semi-quantitative PCR. Results: Invasion of BeWo cells was promoted by leptin and influenced by both leptin concentration and treatment duration. Invasion was most effective at 500 ng/mL leptin and 48 h culture. Leptin-induced invasiveness was suppressed by progesterone in a dose-dependent manner. Leptin significantly decreased the expression levels of TIMP1 and E-cadherin, whereas progesterone significantly decreased expression of MMP-9 and significantly increased levels of TIMP1, TIMP2, and E-cadherin. Conclusions: Leptin promotes invasion of BeWo cells, and progesterone suppresses leptin-induced invasion by regulating the expressions of MMP-9, TIMP1, TIMP2, and E-cadherin. The balance between leptin and progesterone may play an important role in human placenta formation during early pregnancy. PMID:26516305

  11. White light emission in host-sensitized Dy3+-single-doped NaIn(WO4)2 phosphors

    NASA Astrophysics Data System (ADS)

    Xiong, F. B.; Lin, H. F.; Wang, L. J.; Meng, X. G.; Zhu, W. Z.

    2015-02-01

    A novel white NaIn1-x(WO4)2: xDy3+ (x=0, 0.02, 0.04, 0.06 and 0.08) phosphors in pure phase were prepared via high temperature solid-state reaction, and luminescent properties of the phosphors were investigated. The crystal structure of the phosphor was characterized by powder X-ray diffraction, and the spectroscopic properties of Dy3+-doped NaIn(WO4)2 were investigated by diffuse reflectance spectra, photoluminescence emission and photoluminescence excitation spectroscopy. Those spectra illustrated that the Dy3+-doped NaIn(WO4)2 phosphors could be efficiently excited by the host-sensitized excitation in the spectral range of 280-350 nm, and the host-sensitized excitation is more efficient than the Dy3+ excitation. The 6 mol% Dy3+ doping concentration in NaIn(WO4)2 is optimum, and the luminescence concentration quenching occurs beyond the 6 mol% concentration. The concentration quenching mechanism could be attributed to the dipole-dipole interaction between the Dy3+ ions. The CIE color coordinate of the 6 mol% Dy3+-doped NaIn(WO4)2 is (0.319, 0.325). The present work suggests that Dy3+-doped NaIn(WO4)2 could be a promising host-sensitized phosphor applied in white LEDs, and white emission can be obtained by combining the blue host emission with the yellow Dy3+ emission.

  12. 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.

  13. 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.

  14. Low Thermal Gradient Czochralski growth of large CdWO4 crystals and electronic properties of (010) cleaved surface

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    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 CdWO4(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 CdWO4 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 CdWO4 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 CdWO4 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 CdWO4 tungstate is a non-direct semiconductor.

  15. Influence of Morphology and Common Oxidants on the Photocatalytic Property of β-SnWO4 Nanoparticles.

    PubMed

    Raj, Arguine Tes; Thangavel, Sakthivel; Rose, Aleena; Jipsa, C V; Jose, Meera; Nallamuthu, Gouthami; Kim, Sang-Jae; Venugopal, Gunasekaran

    2016-03-01

    In this paper, we report a simple, cost effective and surfactant-free method for synthesizing different morphology of β-SnWO4 with irregular, spherical, flake-like and leaf-like structures by using sonochemical method followed by calcination. A well dispersed and highly crystalline β-SnWO4 crystallites with various sizes have been prepared. The samples were characterized by using X-ray diffraction (XRD), scanning electron microscope (SEM), UV-vis spectroscopy, particle size and Zeta potential analyser. The SEM images reveal the successful preparation of an irregular, spherical, flake-like and leaf-like structure of β-SnWO4. The absorption maximum of as-prepared different structures of β-SnWO4 was observed in visible region. The degradation efficiency was found to be increased in leaf-like structures compared to irregular, spherical and flake-like structures of β-SnWO4. Further, an enhanced photocatalytic effect was observed in leaf-like β-SnWO4 nanoparticles while the common oxidants such as peroxomonosulphate (PMS), peroxodisulphate (PDS) and hydrogen peroxide (H2O2) were added. The degradation efficiency of these oxidants was found in the order of PMS > H2O2 > PDS. Generally these oxidants act as electron scavengers. From our experimental results, it is found that maximum efficiency of 93% was achieved when PMS was added. This shows the vital role of common oxidants in photocatalytic characteristics and their future applications in waste-water treatment. PMID:27455667

  16. 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

    Li, Dong; Chandra, Debraj; Saito, Kenji; Yui, Tatsuto; Yagi, Masayuki

    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 m(2) 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

  17. 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

  18. Highly effective and stable Ag3PO4-WO3/MWCNTs photocatalysts for simultaneous Cr(VI) reduction and orange II degradation under visible light irradiation

    NASA Astrophysics Data System (ADS)

    Cai, Li; Xiong, Xiaoli; Liang, Ninggang; Long, Qiyi

    2015-10-01

    A series of high-performance photocatalysts of Ag3PO4-WO3/multi-walled carbon nanotubes (MWCNTs) were fabricated through a deposition-precipitation method. Their structures and physical properties were characterized by means of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscope (TEM), specific surface analyzer, X-ray diffraction (XRD), UV-vis absorption spectra, photoluminescence spectra (PL) and X-ray photo-electron spectroscopy (XPS). SEM, EDS and TEM analyses verified that Ag3PO4-WO3/MWCNTs composites have been successfully prepared. PL analysis illustrated that Ag3PO4-WO3/MWCNTs have the lower emission peak intensities, compared with Ag3PO4 and WO3. By using simultaneous decontaminations of Cr(VI) and orange II as model reactions, the photocatalytic efficiencies of Ag3PO4, WO3 and Ag3PO4-WO3/MWCNTs were evaluated. The reaction results showed that Ag3PO4-WO3/MWCNTs have strong photocatalytic activities. The effect of Ag3PO4:WO3 ratio on the photocatalytic activity was systemically studied. The catalyst AWM7/3 was found to exhibit the highest photocatalytic activity and excellent chemical stability in repeated and long-term applications. The improvement of photocatalytic activity and stability was mainly attributed to the highly effective separation of photo-generated electron-hole pairs and special transfer pathway of electrons and holes in Ag3PO4-WO3/MWCNTs composites. Therefore, the prepared Ag3PO4-WO3/MWCNTs could act as a high-performance catalyst for the simultaneous decontaminations of Cr(VI) and orange II, and also suggested the promising applications.

  19. Preparation of novel Sb{sub 2}O{sub 3}/WO{sub 3} photocatalysts and their activities under visible light irradiation

    SciTech Connect

    He, Guo-Hua; Liang, Can-Jian; Ou, Yu-Da; Liu, Dan-Ni; Fang, Yue-Ping; Xu, Yue-Hua

    2013-06-01

    Highlights: ► Visible-light-driven Sb{sub 2}O{sub 3}/WO{sub 3} photocatalysts were synthesized. ► Results showed that RhB can be decomposed using a 4 W LED lamp as visible light. ► The coupling of Sb{sub 2}O{sub 3} and WO{sub 3} enhanced the photocatalytic activity of WO{sub 3}. - Abstract: Novel visible-light-driven Sb{sub 2}O{sub 3}/WO{sub 3} photocatalysts were prepared by a hydrothermal synthesis followed by heat treatment, and characterized by transmission electron microscopy (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), BET surface area, Fourier transform infrared spectroscopy (FT-IR) and photoluminescence spectra (PL). The photocatalytic activities of Sb{sub 2}O{sub 3}/WO{sub 3} photocatalysts were evaluated by the rhodamine B degradation using a LED lamp as visible light irradiation. Compared with pure WO{sub 3} and Sb{sub 2}O{sub 3}, the significantly enhanced photocatalytic activities of the Sb{sub 2}O{sub 3}/WO{sub 3} composite particles are attributed to the decrease of the recombination rate of photoinduced electron–hole pairs due to the coupling of Sb{sub 2}O{sub 3} and WO{sub 3} within the composite nanoparticles. Studies of Sb{sub 2}O{sub 3}/WO{sub 3} composites indicate that one approach to design composite materials with enhanced photocatalytic performance is through coupling Sb{sub 2}O{sub 3} with WO{sub 3}, which the lowest energy states for electrons and holes are in different semiconductors.

  20. Fibronectin-based scaffold domain proteins that bind myostatin: a patent evaluation of WO2014043344.

    PubMed

    Walker, Ryan G; Thompson, Thomas B

    2015-05-01

    Muscular dystrophies (MD) are commonly characterized by progressive loss of muscle mass and function. It is hypothesized that therapeutic blockade of the TGF-β ligand myostatin, a negative regulator of muscle mass, will stimulate muscle growth and restore muscle function. Although many anti-myostatin targets are currently being pursued in the clinical setting, the efficacies of the tested molecules have shown mixed results. The patent WO2014043344 describes a novel approach for myostatin inhibition using a modified fibronectin type III domain that could potentially be used to treat MD and other muscle-related pathologies. PMID:25632990

  1. Optical characterization of WO3 -VOx thin films for application in electrochromic devices—'smart windows'

    NASA Astrophysics Data System (ADS)

    Bodurov, G.; Ivanova, T.; Aleksandrova, M.; Gesheva, K. A.

    2012-03-01

    WO3-VOx thin films were deposited by atmospheric pressure chemical vapor deposition (APCVD). A typical electrochromic device is a sandwichlike structure with two conductive glasses and an electrolyte layer. An electrochromic transition metal oxide film is deposited over one of the glass substrates thus forming the working electrode. The counter electrodes in the devices are bare conductive glasses, and the polymeric electrolyte is used to laminate the two glass substrates and to supply the devices with Li ions. The working electrode material is investigated related to its initial transmittance, vibrational properties, and structure.

  2. High-pressure structural phase transition in MnWO4

    NASA Astrophysics Data System (ADS)

    Ruiz-Fuertes, J.; Friedrich, A.; Gomis, O.; Errandonea, D.; Morgenroth, W.; Sans, J. A.; Santamaría-Pérez, D.

    2015-03-01

    The pressure-induced phase transition of the multiferroic manganese tungstate MnWO4 is studied on single crystals using synchrotron x-ray diffraction and Raman spectroscopy. We observe the monoclinic P 2 /c to triclinic P 1 ¯ phase transition at 20.1 GPa and get insight on the phase transition mechanism from the appearance of tilted triclinic domains. Selective Raman spectroscopy experiments with single crystals have shown that the onset of the phase transition occurs 5 GPa below the previously reported pressure obtained from experiments performed with powder samples.

  3. High pressure polymorphs and amorphization of upconversion host material NaY(WO4)2

    NASA Astrophysics Data System (ADS)

    Hong, Fang; Yue, Binbin; Cheng, Zhenxiang; Kunz, Martin; Chen, Bin; Mao, Ho-Kwang

    2016-07-01

    The pressure effect on the structural change of upconversion host material NaY(WO4)2 was studied by using in-situ synchrotron X-ray diffraction. A transition from the initial scheelite phase to the M-fergusonite phase occurs near 10 GPa, and another phase transition is found near 27.5 GPa, which could be an isostructural transition without symmetry change. The sample becomes amorphous when the pressure is fully released from high pressure. This work demonstrates the possibility of synthesizing various polymorph structures for non-linear optical applications with a high pressure, chemical doping, or strained thin-film nanostructure process.

  4. Epitaxial growth of high quality WO{sub 3} thin films

    SciTech Connect

    Leng, X.; Pereiro, J.; Bollinger, A. T.; Strle, J.; Božović, I.

    2015-09-01

    We have grown epitaxial WO{sub 3} films on various single-crystal substrates using radio frequency magnetron sputtering. While pronounced surface roughness is observed in films grown on LaSrAlO{sub 4} substrates, films grown on Y AlO{sub 3} substrates show atomically flat surfaces, as demonstrated by atomic force microscopy and X-ray diffraction (XRD) measurements. The crystalline structure has been confirmed to be monoclinic by symmetric and skew-symmetric XRD. The dependence of the growth modes and the surface morphology on the lattice mismatch are discussed.

  5. 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.

  6. 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.

  7. Substituted indoles as HIV-1 non-nucleoside reverse transcriptase inhibitors: a patent evaluation (WO2015044928).

    PubMed

    Li, Xiao; Gao, Ping; Zhan, Peng; Liu, Xinyong

    2016-05-01

    The invention described in this patent (WO2015044928) is related to compounds based on the substituted indole scaffold, their synthetic process and application to inhibit HIV-1 replication as non-nucleoside reverse transcriptase inhibitors (NNRTIs). Some of the newly claimed compounds presented improved potency against wild-type (WT) HIV-1 strain in comparison to previously disclosed indole-based NNRTIs and were also shown to be effective against common resistant HIV-1 strains. In light of their novel structural characteristics, simple synthetic route and improved anti-HIV activity, these compounds deserve further study as promising NNRTIs. PMID:26742549

  8. 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.

  9. 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. PMID:27223824

  10. 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. PMID:16712121

  11. Reflection high-energy electron diffraction beam-induced structural and property changes on WO{sub 3} thin films

    SciTech Connect

    Du, Y. Varga, T.; Zhang, K. H. L.; Chambers, S. A.

    2014-08-04

    Reduction of transition metal oxides can greatly change their physical and chemical properties. Using deposition of WO{sub 3} as a case study, we demonstrate that reflection high-energy electron diffraction (RHEED), a surface-sensitive tool widely used to monitor thin-film deposition processes, can significantly affect the cation valence and physical properties of the films through electron-beam induced sample reduction. The RHEED beam is found to increase film smoothness during epitaxial growth of WO{sub 3}, as well as change the electronic properties of the film through preferential removal of surface oxygen.

  12. Synthesis and luminescent properties of spindle-like CaWO{sub 4}:Sm{sup 3+} phosphors

    SciTech Connect

    Tian, Yue; Liu, Yu; Hua, Ruinian; Na, Liyan; Chen, Baojiu

    2012-01-15

    Graphical abstract: In this paper, spindle-like CaWO{sub 4}:Sm{sup 3+} phosphors were prepared via a polyvinylpyrrolidone (PVP)-assisted sonochemical process. Dependence of emission intensity on Sm{sup 3+} ions concentration in the CaWO{sub 4}:Sm{sup 3+} phosphor were also calculated via a nonlinear fitting by using the formula y = ax/(1 + bx{sup c}). Highlights: Black-Right-Pointing-Pointer The samples were prepared via a PVP assisted sonochemical process. Black-Right-Pointing-Pointer The color coordinates for 1 mol% Sm{sup 3+} doped CaWO{sub 4} phosphor were calculated. Black-Right-Pointing-Pointer The D-D interaction is responsible for concentration quenching between Sm{sup 3+} ions. Black-Right-Pointing-Pointer The critical energy transfer distances (R{sub c}) were obtained. -- Abstract: Spindle-like CaWO{sub 4}:Sm{sup 3+} phosphors were prepared via a Polyvinylpyrrolidone (PVP)-assisted sonochemical process, and characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and photoluminescence spectroscopy (PL). The XRD results suggested that the prepared samples are single-phase. The FE-SEM images indicated that the prepared CaWO{sub 4}:Sm{sup 3+} phosphors are composed of many spindles with maximum average diameter of 150 nm and maximum average length of 500 nm. Under 404 nm excitation, the characteristic emissions corresponding to {sup 4}G{sub 5/2} {yields} {sup 6}H{sub J} (J = 5/2, 7/2, 9/2 and 11/2) transitions of Sm{sup 3+} in CaWO{sub 4} phosphors were observed. The color coordinates for 1 mol% Sm{sup 3+} doped CaWO{sub 4} phosphor were calculated to be (0.595, 0.404). The fluorescent concentration quenching of Sm{sup 3+} doped spindle-like phosphors was studied based on the Van Uitert's model, and it was found that the electric dipole-dipole (D-D) interaction is the dominant energy transfer mechanism between Sm{sup 3+} ions in the CaWO{sub 4}:Sm{sup 3+} phosphors. The critical energy transfer distance was

  13. 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.

  14. Reflection High-Energy Electron Diffraction Beam-Induced Structural and Property Changes on WO3 Thin Films

    SciTech Connect

    Du, Yingge; Zhang, Hongliang; Varga, Tamas; Chambers, Scott A.

    2014-08-08

    Reduction of transition metal oxides can greatly change their physical and chemical properties. Using deposition of WO3 as a case study, we demonstrate that reflection high-energy electron diffraction (RHEED), a surface-sensitive tool widely used to monitor thin-film deposition processes, can significantly affect the cation valence and physical properties of the films through electron-beam induced sample reduction. The RHEED beam is found to increase film smoothness during epitaxial growth of WO3, as well as change the electronic properties of the film through preferential removal of surface oxygen.

  15. Photo-electron double regulated resistive switching memory behaviors of Ag/CuWO4/FTO device

    NASA Astrophysics Data System (ADS)

    Sun, B.; Jia, X. J.; Wu, J. H.; Chen, P.

    2015-12-01

    In this work, the CuWO4 film based resistive switching memory capacitors were fabricated with hydrothermal and spin-coating approaches. The device exhibits excellent photo-electron double controlled resistive switching memory characteristics with OFF/ON resistance ratio of ~103. It is believed that the interface of CuWO4 and FTO is responsible for such a switching behavior and it can be described by the Schottky-like barriers model. This study is useful for exploring the multifunctional materials and their applications in photo-electron double controlled nonvolatile memory devices.

  16. 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

  17. 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.

  18. 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.

  19. 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

  20. Photothermal ablation cancer therapy using homogeneous CsxWO3 nanorods with broad near-infra-red absorption

    NASA Astrophysics Data System (ADS)

    Guo, Chongshen; Yin, Shu; Yu, Haijun; Liu, Shaoqin; Dong, Qiang; Goto, Takehiro; Zhang, Zhiwen; Li, Yaping; Sato, Tsugio

    2013-06-01

    Recently, photothermal ablation therapy (PTA) employing near-infrared radiation (NIR) has been extensively investigated as an emerging modality for cancer management. However, the clinical translation of this promising approach is limited by the lack of PTA agents with broad NIR absorption, low cost and high photothermal conversion efficiency. Herein, we have developed PEGylated homogeneous CsxWO3 nanorods (a mean size ~69.3 nm × 12.8 nm) with broad photo-absorption (780-2500 nm) as a novel NIR absorbent for PTA treatment of human cancer. The prepared CsxWO3 nanocrystals displayed strong near-infrared optical absorption with a high molar extinction coefficient (e.g. 4.8 × 1010 M-1 cm-1 at 980 nm), thus generated significant amounts of heat upon excitation with near-infrared light. The PTA study in two human carcinoma cell lines (i.e. A549 lung cancer cells and HeLa ovarian cancer cells) demonstrated that CsxWO3 nanorods can efficiently cause cell death via hyperthermia induced lysosome destruction, cytoskeleton protein degradation, DNA damage and thereafter cellular necrosis or apoptosis. Our study also confirmed the migration of healthy cells migrated from unirradiated areas to dead cell cycle, which is essential for tissue reconstruction and wound healing after photodestruction of tumor tissue. The prompted results reported in the current study imply the promising potential of CsxWO3 nanorods for application in PTA cancer therapy.Recently, photothermal ablation therapy (PTA) employing near-infrared radiation (NIR) has been extensively investigated as an emerging modality for cancer management. However, the clinical translation of this promising approach is limited by the lack of PTA agents with broad NIR absorption, low cost and high photothermal conversion efficiency. Herein, we have developed PEGylated homogeneous CsxWO3 nanorods (a mean size ~69.3 nm × 12.8 nm) with broad photo-absorption (780-2500 nm) as a novel NIR absorbent for PTA treatment of human

  1. 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

  2. Grafting mechanism of electrochromic PAA-WO{sub 3} composite film

    SciTech Connect

    Choy, J.H.; Kim, Y.I.; Kim, B.W.; Campet, G.; Portier, J.; Huong, P.V.

    1999-02-01

    A micro-Raman spectroscopic study has been carried out to investigate the electrochromic process in a porous and nanocrystalline tungsten oxide film. The film was prepared by dipping the tin-doped indium oxide glass into an aqueous mixture solution of PAA (polyacrylic acid) and WO{sub 3}-NH{sub 4}OH. After heating at low temperature, around 100 C, the film was treated in 1 N HCl in order to achieve polycondensation, where the ammonium ion was replaced with a proton. In the micro-Raman spectra for the bleached and colored PAA-WO{sub 3} films, it was evident that the coloration accompanies a peak reduction at {approximately}960 cm{sup {minus}1} and a peak enhancement at {approximately}810 cm{sup {minus}1}. Based upon the present Raman observation, the authors can confirm that the electrochromism of the nanocrystalline tungsten oxide is dominated by the grafting process, i.e., the surface modification of {single_bond}W{sup VI}{double_bond}O bonds into {single_bond}W{sup V}{double_bond}O{sup (1{minus}{delta})+}{emdash}M{sup {delta}+} (M = H, Li) ones.

  3. Effects of surface porosity on tungsten trioxide (WO{sub 3}) films' electrochromic performance

    SciTech Connect

    Lee, W.J.; Fang, Y.K.; Ho, J.J.; Hsieh, W.T.; Ting, S.F.; Huang, Daoyang; Ho, F.C.

    2000-02-01

    In this paper, the correlation between the electrochromic performance and the surface morphology of the tungsten trioxide (WO{sub 3}) thin films sputtered by dc reactive magnetron sputtering with widely varying target-substrate distances was investigated. It is found that the optical density change ({Delta}OD) of films is strongly affected by the target-substrate distance. The coloration efficiency (CE) at 633 nm was also found to be sensitive to the target-substrate distance, with 16 cm{sup 2}/C of film sputtered at 6 cm and 50 cm{sup 2}/C at 18 cm. X-ray diffraction showed that the crystal structure of films was amorphous. By using atomic force microscope to identify the surface porosity of the sputtered WO{sub 3} films, the authors found that the film at longer target-substrate distance was rough, porous, and having a cone-shaped columns morphology, this offering a good electrochromic performance for opto-switching applications.

  4. Tuning ferroelectric polarization in AA' MnWO6 double perovskites through A cation substitution

    NASA Astrophysics Data System (ADS)

    Young, Joshua; Rondinelli, James

    2015-03-01

    Magnetic ferroelectric materials, which exhibit simultaneous magnetic and electric polarizations, have generated significant interest for application in novel electronic devices. Recent experimental work has shown that the double perovskite NaLaMnWO6 exhibits anti-ferromagnetic order, while computational studies predict it to also exhibit a spontaneous polarization of 16 μC/cm2 owing to an octahedral rotation induced improper mechanism. Using first principles density functional theory calculations, we investigate nine iso-structural AA' MnWO6 compounds through chemical substitution of alkali metal (A=Na, K, Rb) and rare earth cations (A'=La, Nd, Y), and find that the ferroelectric polarization can be enhanced by up to 150% by maximizing the difference in ionic size of the A and A' cations. We then identify the microscopic features responsible for this polarization through an examination of the tolerance factors, bond valences, and atomic displacement patterns. We anticipate that the crystal-chemistry criteria and analysis presented here can be extended to additional members of this family as well as guide the targeted design of novel multiferroics.

  5. 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.

  6. Optical phonon modes and infrared dielectric properties of monoclinic CoWO4 microcrystals

    NASA Astrophysics Data System (ADS)

    Moreira, Roberto L.; Almeida, Rafael M.; Siqueira, Kisla P. F.; Abreu, Cintia G.; Dias, Anderson

    2016-02-01

    The phonon characteristics of CoWO4 microcrystals with monoclinic Wolframite structure were investigated by far-infrared (IR) and Raman spectroscopies. Near-normal spectra were taken for IR light polarization along the principal b-axis (A u modes) and along several angles within the ac-plane (B u modes). The IR spectra were analyzed with a generalized Drude-Lorentz model, and all predicted polar phonon modes were fully determined, including their symmetries, the dielectric Lorentz parameters and the non-orthogonal phonon polarizations for the B u modes. Anomalous dispersion and negative values for the real and imaginary parts of the off-diagonal components of the dielectric tensor functions were identified and discussed under the light of the varying phonon polarization directions (spread out in the ac-plane). The obtained static and background dielectric tensors gave an average permittivity of 16.1 (at microwave region), refractive indices along the principal dielectric axes of 2.22, 2.33 and 2.44 (at 1 μm), the optical axes, and an estimated value for the biaxial angle of the crystal. Polarized Raman spectra on appropriate scattering configurations revealed the 18 non-polar gerade phonons of CoWO4 crystals, with their correct symmetries attributed.

  7. CdWO4-Boron FY 2000 Task 4 Completion Report

    SciTech Connect

    Z. W. Bell; M. W. Moyer

    2001-02-01

    The fabrication of boron-covered crystal scintillation detectors is described. Bulk boron-loaded epoxy material was cast and cut into 0.5 mm-thick wafers that were mounted on CdWO{sub 4} and CsI(Tl) crystals. The crystals were mounted on miniature photomultiplier tubes and gamma spectra were obtained with the detectors. The ability of these small detectors to produce spectra that can be analyzed to provide isotopic identification has been demonstrated. In addition, the detector can produce a signature indicating the presence of neutrons. The same miniature size of these detectors that makes them attractive for hand-held portable use, may be a limiting factor in their efficiency. The small size of the scintillation crystals makes them not as efficient as larger NaI(Tl) crystals simply by virtue of significantly decreased sensitive volume and surface area. It may be worthwhile to consider slightly larger crystals (approximately 15 mm cubic CdWO{sub 4}) mounted on rectangular photomultipliers in a detecting head connected to the electronics package by a signal cable.

  8. 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.

  9. 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

    2016-07-01

    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. PMID:27308777

  10. 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.

  11. 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

  12. 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.

  13. Experimental study on electron transport in high intensity laser solid interaction w/o cone

    NASA Astrophysics Data System (ADS)

    Baton, Sophie; Guillou, P.; Batani, D.; Rousseaux, C.; Kodama, R.; Aglitskiy, Y.

    2005-10-01

    New electron transport results have been obtained in the interaction of a high intensity laser with planar solid target w/o gold cone. The experiment has been performed at the LULI Laboratory with the 100 TW laser facility. The interaction took place either at 1.057 μm or at 0.53 μm wavelength. The targets consist of three layers planar targets molecularly bonded w/o gold cone glued on the front side. The target thickness and the surface size, the target holder, the ASE of the laser and its focalisation point have been varied in order to study their influence on the electron transport. Several diagnostics were implemented: visible rear side imaging, HISAC, X-ray-Kα imaging and spectroscopy and the angular distribution of the emitted protons. In our conditions, no significant cone effect was observed. Nevertheless these results seem to indicate that the behaviour of the fast electrons is highly influenced by the target mass.

  14. 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

  15. 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.

  16. Measurement of nuclear recoil quenching factors in CaWO 4

    NASA Astrophysics Data System (ADS)

    Jagemann, Th.; Feilitzsch, F. v.; Hagn, H.; Jochum, J.; Potzel, W.; Rau, W.; Stark, M.; Westphal, W.

    2006-11-01

    The CRESST experiment, aiming at the direct detection of WIMPs via nuclear recoils, is currently using scintillating CaWO4 crystals. The WIMP-nucleus cross section for elastic scattering as well as the scintillation efficiency differ considerably for recoils from Ca, W and O in these crystals. Therefore a discriminating detector calibration is essential in order to improve WIMP parameter claims. At the tandem accelerator of the Maier-Leibnitz-Laboratory (MLL) in Garching, Germany, a neutron scattering facility is operated for the determination of the individual quenching factors (QF) in the bulk of a CaWO4 crystal to better understand the detector response to neutron background and a possible WIMP signal. First measurements at room temperature reveal QF(O) = 7.8 ± 0.3% (recoil energy 1.0-2.2 MeV), QF(Ca) = 6.3 ± 1.6% (recoil energy 0.4-1 MeV), QF(W) < 3.0% (2σ, recoil energy 0.1 MeV).

  17. Structural and optical properties of WO3 electrochromic layers prepared by the sol-gel method

    NASA Astrophysics Data System (ADS)

    Novinrooz, Abdoljavad; Sharbatdaran, Masoomeh; Noorkojouri, Hassan

    2005-09-01

    Thin layers of tungsten trioxide have been prepared from an aqueous solution of peroxotungstic acid (PTA) using the sol-gel method. Compositional, structural and optical characteristics of WO3 coated on indium tin oxide (ITO) conductive glass substrates were studied using X-ray diffractometery (XRD), cyclic voltammetery (CV), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Monoclinic and triclinic crystalline structures for thin film and powdered WO3 were confirmed by XRD analysis. SEM micrograph of annealed samples revealed micro cracks due to a decrease in density and a contraction of layers. EDX analysis showed that 1∶2 ratio of oxygen and tungsten atoms in the prepared films is obtained at heat treatment temperatures higher than 200 °C. Furthermore, the annealed samples showed very good electrochromic behavior in cyclic voltammetery studies. Refractive index “n” and extinction coefficient “k” values were found to be reduced by increasing the wavelength and decreasing the temperature.

  18. Electronic State of Fe in Double Perovskite Oxide Sr 2FeWO 6

    NASA Astrophysics Data System (ADS)

    Kawanaka, Hirofumi; Hase, Izumi; Toyama, Shunichiro; Nishihara, Yoshikazu

    1999-09-01

    The magnetic properties of double perovskite oxide Sr2FeWO6 have been reported. The magnetic susceptibility and Mössbauer effect of 57Fe show that this compound is an antiferromagnet with T N=37 K. The Mössbauer parameters below ˜20 K are the center shift of +1.2 mm/s relative to metallic iron, the quadrupole splitting of 1.9 mm/s and the hyperfine field of ˜110 kOe. The quadrupole splitting has a strong temperature dependence. From these data, we conclude that Fe in Sr2FeWO6 is in the Fe2+ high-spin state, while the hyperfine field seems to be quite small. The cell volume shows a large increase compared to other Sr2FeTO6 ( T= Mo, Re, etc.), which is in the Fe3+ high-spin state. These results suggest that these compounds have a strongly coupled charge and lattice systems.

  19. Tm,Ho:KY(WO4)2 planar waveguide laser

    NASA Astrophysics Data System (ADS)

    Ruiz Madroñero, C. V.; Mateos, X.; Loiko, P.; Yumashev, K.; Petrov, V.; Griebner, U.; Aguiló, M.; Díaz, F.

    2016-09-01

    A lattice-matched, 5 at.% Tm, 0.5 at.% Ho-codoped, 5.77 µm-thick KY0.58Gd0.22Lu0.20(WO4)2 active layer with optimized refractive index contrast is grown by liquid phase epitaxy on the (3 1 0) face of pure KY(WO4)2 substrate. Laser operation at 2051 nm (5I7  →  5I8 transition of the Ho3+ ion) is demonstrated with this waveguide pumped at 794 nm. The maximum continuous wave output power amounts to 1.9 mW at 2051 nm corresponding to a slope efficiency of 10.5%. The laser threshold is as low as 1.5 mW of absorbed pump power. The developed structure is promising for single-transverse-mode channel holmium waveguide lasers. Laser operation in 3 at.% Tm-singly doped 4.41 µm thick layer grown on the (3 1 0)-oriented substrate is also demonstrated at 1841 nm with a slope efficiency of 31%.

  20. 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.

  1. Fabrication of the heterostructured CsTaWO6/Au/g-C3N4 hybrid photocatalyst with enhanced performance of photocatalytic hydrogen production from water

    NASA Astrophysics Data System (ADS)

    Lang, Junyu; Liu, Mengqing; Su, Yiguo; Yan, Lijuan; Wang, Xiaojing

    2015-12-01

    In this work, a novel CsTaWO6/Au/g-C3N4 hybrid photocatalyst is successfully fabricated. The photocatalytic performance of the heterostructured CsTaWO6/Au/g-C3N4 composite was investigated. Au nanoparticles were photo-deposited as the interlayer between g-C3N4 and the surface of CsTaWO6, which can facilitate the photoinduced electrons migration as an electron-conduction bridge as well as increase visible-light absorption via the surface plasmon resonance. This heterostructured interface bridging by Au particles may significantly retard the recombination of electron-holes, which is beneficial to promote the photocatalytic activity under visible-light irradiation. It is found the CsTaWO6/Au/g-C3N4 sample showed excellent photocatalytic activity of water splitting, even higher than the sum of g-C3N4 and Au/CsTaWO6 samples, or the sum of CsTaWO6 and Au/g-C3N4 samples. It indicates that the heterostructured combination of g-C3N4 and CsTaWO6 bridging by Au particles provided the synergistic photocatalytic activity driving by solar light through an efficient electron transfer process.

  2. {010}-Oriented micro-flower-like hierarchical Bi2WO6 with high adsorptivity and visible-light-driven photoactivity: experimental studies and first-principles modeling

    NASA Astrophysics Data System (ADS)

    Wang, Jiawei; Li, Jiajun; Zhao, Naiqin; Sha, Junwei; Hao, Shuang; Liu, Enzuo; Shi, Chunsheng; He, Chunnian; Wang, Defa

    2015-01-01

    {010}-Oriented flower-like Bi2WO6 with high adsorptivity and photoactivity was prepared via a hydrothermal method without any additives under neutral environment. The anisotropic flower-like Bi2WO6 shows greatly enhanced adsorptivity and photoactivity compared with isotropic particle Bi2WO6 as well as most of other forms of Bi2WO6. The superior adsorptivity shows potential in suitability for majority of dyes. Detailed study on microstructure and morphology indicates that mesoporous structure and large surface area mainly contribute to the superior properties. Especially, {010} crystal planes of flower-like Bi2WO6 terminated with [Bi2O2]2+ layers provide more adsorption sites for dyes than other facets. In combination with first-principles calculations, it is initially revealed that {010}-oriented facets preference benefits hole distribution at surface and provides the most reactive sites, thus enhances the photoactivity of the flower-like Bi2WO6. Moreover, the anisotropic flower-like Bi2WO6 shows excellent recyclability and cycling stability with great potential in environmental applications.

  3. 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.

  4. 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.

  5. Crystallographic shear in the Nb/sub 2/O/sub 5/-WO/sub 3/ and Ta/sub 2/O/sub 5/-WO/sub 3/ systems

    SciTech Connect

    England, P.J.; Booth, J.; Tilley, R.J.D.; Ekstrom, T.

    1982-08-01

    Crystallographic shear (CS) phases occurring in the Nb/sub 2/O/sub 5/-WO/sub 3/ and Ta/sub 2/O/sub 5/-WO/sub 3/ systems near to WO/sub 3/ were characterized by X-ray diffraction and high-resolution transmission electron microscopy. The Nb/sub 2/O/sub 5/-WO/sub 3/ samples were heated at 1600K. They contained ordered )104) and )001) CS planes and wavy CS which were composed of intergrowths of )104) and )001) CS segments. The compsition range over which the )104) CS series extended was from (Nb, W)O/sub 2.954/ i.e., (Nb,W)/sub 65/O/sub 192/, i.e., (Nb,W)/sub 52/O/sub 153/. The composition range over which the )001)CS series extended was from (Nb,W)O/sub 2.9375/, i.e., (Nb,W)/sub 16/O/sub 47/ to (Nb,W)O/sub 2.875/, i.e., (Nb,W)/sub 8/O/sub 23/.The Ta/sub 2/O/sub 5/-WO/sub 3/ samples were prepared at 1593, 1623, and 1672K. At lower temperatures ordered )103) CS phases were found, with a composition range extending between (Ta,W)O/sub 2.960/, i.e., (Ta,W)/sub 50/O/sub 148/, to (Ta,W)O/sub 2.944/, i.e., (Ta,W)/sub 36/O/sub 106/. At 1673K ordered )103) CS phases occurred, as did wavy CS composed of intergrowths of )103) and )104) CS segments.

  6. Fabrication of Wide-Range-Visible Photocatalyst Bi2WO6-x nanoplates via Surface Oxygen Vacancies

    NASA Astrophysics Data System (ADS)

    Lv, Yanhui; Yao, Wenqing; Zong, Ruilong; Zhu, Yongfa

    2016-01-01

    Bi2WO6 as a high visible-light-driven catalyst has been aroused broad interest. However, it can only be excitated by the light with λ < 450 nm and the solar energy utilization need to be improved. Here, the wide-range-visible photoresponse Bi2WO6-x nanoplates were fabricated by introducing surface oxygen vacancies through the controllable hydrogen reduction method. The visible photoresponse wavelength range is extended from 450 nm to more than 600 nm. In addition, the photocatalytic activity of Bi2WO6-x is also increased and is 2.1 times as high as that of pristine Bi2WO6. The extending of the photoresponse range and the enhancement of the photoactivity both can be attributed to the surface-oxygen-vacancy states. This is because surface-oxygen-vacancy states generated above and partly overlapping of with the valence band (VB) will result in the rising of valence band maximum (VBM), thus broadening the VB width. This approach is proposed to develop many types of wide-range-visible optical materials and to be applicable to many narrow and wide bandgap materials.

  7. 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

  8. Photothermal ablation cancer therapy using homogeneous CsxWO3 nanorods with broad near-infra-red absorption.

    PubMed

    Guo, Chongshen; Yin, Shu; Yu, Haijun; Liu, Shaoqin; Dong, Qiang; Goto, Takehiro; Zhang, Zhiwen; Li, Yaping; Sato, Tsugio

    2013-07-21

    Recently, photothermal ablation therapy (PTA) employing near-infrared radiation (NIR) has been extensively investigated as an emerging modality for cancer management. However, the clinical translation of this promising approach is limited by the lack of PTA agents with broad NIR absorption, low cost and high photothermal conversion efficiency. Herein, we have developed PEGylated homogeneous CsxWO3 nanorods (a mean size ∼69.3 nm × 12.8 nm) with broad photo-absorption (780-2500 nm) as a novel NIR absorbent for PTA treatment of human cancer. The prepared CsxWO3 nanocrystals displayed strong near-infrared optical absorption with a high molar extinction coefficient (e.g. 4.8 × 10(10) M(-1) cm(-1) at 980 nm), thus generated significant amounts of heat upon excitation with near-infrared light. The PTA study in two human carcinoma cell lines (i.e. A549 lung cancer cells and HeLa ovarian cancer cells) demonstrated that CsxWO3 nanorods can efficiently cause cell death via hyperthermia induced lysosome destruction, cytoskeleton protein degradation, DNA damage and thereafter cellular necrosis or apoptosis. Our study also confirmed the migration of healthy cells migrated from unirradiated areas to dead cell cycle, which is essential for tissue reconstruction and wound healing after photodestruction of tumor tissue. The prompted results reported in the current study imply the promising potential of CsxWO3 nanorods for application in PTA cancer therapy. PMID:23743996

  9. In situ growth of Ag nanoparticles on α-Ag2WO4 under electron irradiation: probing the physical principles.

    PubMed

    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. PMID:27114472

  10. Electronic structure and magnetic properties of FeWO{sub 4} nanocrystals synthesized by the microwave-hydrothermal method

    SciTech Connect

    Almeida, M.A.P.; Cavalcante, L.S.; Morilla-Santos, C.; Filho, P.N. Lisboa; Beltran, A.; Andres, J.; Gracia, L.; Longo, E.

    2012-11-15

    This communication reports that FeWO{sub 4} nanocrystals were successfully synthesized by the microwave-hydrothermal method at 443 K for 1 h. The structure and shape of these nanocrystals were characterized by X-ray diffraction, Rietveld refinement, and transmission electron microscopy. The experimental results and first principles calculations were combined to explain the electronic structure and magnetic properties. Experimental data were obtained by magnetization measurements for different applied magnetic fields. Theoretical calculations revealed that magnetic properties of FeWO{sub 4} nanocrystals can be assigned to two magnetic orderings with parallel or antiparallel spins in adjacent chains. These factors are crucial to understanding of competition between ferro- and antiferromagnetic behavior. Highlights: Black-Right-Pointing-Pointer Monophasic FeWO{sub 4} nanocrystals were synthesized by the microwave-hydrothermal method. Black-Right-Pointing-Pointer Rietveld refinement and clusters model for monoclinic structure Black-Right-Pointing-Pointer Magnetic properties of FeWO{sub 4} nanocrystals at different temperatures.

  11. Ultrasonic synthesis of high fluorescent C-dots and modified with CuWO4 nanocomposite for effective photocatalytic activity

    NASA Astrophysics Data System (ADS)

    ReddyPrasad, Puthalapattu; Naidoo, Eliazer Bobby

    2015-10-01

    High fluorescent C-dots were synthesized from dextrose via facile ultrasonic wave assisted reaction. Carbon dots (C-dots)/Copper tungstate (CuWO4) heterostructure has been prepared via a facile reflux approach. The novel C-dots/CuWO4 photocatalyst were characterized by using transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, UV-vis, photoluminescence and X-ray photoelectron spectroscopy. The photocatalytic property of heterostructure nanocomposite has also been investigated by using rhodamine B as a model organic pollutant. The obtained results revealed that as prepared C-dots are predominately multilayer graphene oxide with luminance properties. After incorporation of C-dots onto the CuWO4, it contributes to the improvement of charge separation and reduction of charge recombination and thereby enhancing the photocatalytic property, respectively. The C-dots in the nanocomposites can efficiently trap electrons, thus hindering the recombination of photogenerated electrons and holes. The heterostructure nanocomposite with 5.0 wt% C-dots shows the highest photocatalytic activity, which is about three times as that of pure CuWO4.

  12. Fabrication of Wide–Range–Visible Photocatalyst Bi2WO6−x nanoplates via Surface Oxygen Vacancies

    PubMed Central

    Lv, Yanhui; Yao, Wenqing; Zong, Ruilong; Zhu, Yongfa

    2016-01-01

    Bi2WO6 as a high visible-light-driven catalyst has been aroused broad interest. However, it can only be excitated by the light with λ < 450 nm and the solar energy utilization need to be improved. Here, the wide–range–visible photoresponse Bi2WO6−x nanoplates were fabricated by introducing surface oxygen vacancies through the controllable hydrogen reduction method. The visible photoresponse wavelength range is extended from 450 nm to more than 600 nm. In addition, the photocatalytic activity of Bi2WO6−x is also increased and is 2.1 times as high as that of pristine Bi2WO6. The extending of the photoresponse range and the enhancement of the photoactivity both can be attributed to the surface-oxygen-vacancy states. This is because surface-oxygen–vacancy states generated above and partly overlapping of with the valence band (VB) will result in the rising of valence band maximum (VBM), thus broadening the VB width. This approach is proposed to develop many types of wide–range–visible optical materials and to be applicable to many narrow and wide bandgap materials. PMID:26777609

  13. Red, green and blue low-voltage cathodoluminescence of rare-earth doped BaWO4 phosphors

    NASA Astrophysics Data System (ADS)

    Li, H. L.; Wang, Z. L.; Hao, J. H.

    2009-02-01

    Spherical phosphors BaWO4 doped with rare-earth ions (RE = Eu, Tb, Tm) were prepared by the polyol method. The crystal structure and morphology of the powders were investigated using X-ray diffraction, field emission scanning electron microscopy and Fourier transform spectroscopy. The as-prepared BaWO4-based phosphors processed as low as 160 °C show mono-dispersive and highly crystalline nanostructure. The optical characteristics of the phosphors were investigated using low-voltage cathodoluminescence. Efficient energy transfer between the host and RE ions were revealed in the spectra. Red, green and blue cathodoluminescence were observed corresponding to sharp dominant emission peaks located at 616 nm, 545 nm and 473 nm for Eu3+, Tb3+ and Tm3+ doped phosphors, respectively. Those peaks are attributed to the characteristic emission from Eu3+ (5D0 - 7FJ transitions), Tb3+ (5D3 - 7FJ and 5D4 - 7FJ transitions) and Tm3+ (1D2 - 3F4 and 1D2 - 3H4 transitions) under low-voltage (<=5 kV) excitation of electron beam. Luminescent intensities in the annealed BaWO4-based phosphors were significantly enhanced. The characteristics of the phosphors are investigated in terms of luminance, chromaticity and color purity. Fundamental mechanisms responsible for the low-voltage cathodoluminescence of BaWO4-based phosphors are discussed.

  14. Dodecyl ethyl dimethyl ammonium bromide capped WO3 nanoparticles: efficient scaffolds for chemical sensing and environmental remediation.

    PubMed

    Shukla, Sheifali; Chaudhary, Savita; Umar, Ahmad; Chaudhary, Ganga Ram; Mehta, S K

    2015-10-21

    The current work revealed the comparative analysis of bare and surface functionalized tungsten trioxide (WO3) nanoparticles that can be successfully utilized as competent photocatalysts for the degradation of organic dyes and as efficient electron transporters for the fabrication of highly sensitive electrochemical sensors in aqueous medium. The room temperature synthesis of WO3 nanoparticles with good crystallinity was carried out in the presence of dodecylethyldimethyl ammonium bromide (DEDMAB) as the template by a wet chemical process. The surface functionalized nanoparticles possess a controllable band gap and act as an effectual substrate for electrochemical sensing of hydrazine. The sensitivity values of the fabricated sensor range from 9.39 μA μM(-1) cm(-2) with the limits of detection ranging from 28.8 μM. Furthermore, surface modulated particles also exhibited enhanced photocatalytic performance in the photodegradation of Congo red dye with an efficiency of 98.67% compared to bare WO3 nanoparticles without any modification. The comparison of the current responses and photodegradation activity of the bare and capped WO3 particles illustrates an excellent sensitivity, selectivity and operational stability of the as-functionalized nanoparticles. PMID:26373254

  15. Sulfur Nanoparticles Synthesis and Characterization from H2S Gas, Using Novel Biodegradable Iron Chelates in W/O Microemulsion

    NASA Astrophysics Data System (ADS)

    Deshpande, Aniruddha S.; Khomane, Ramdas B.; Vaidya, Bhalchandra K.; Joshi, Renuka M.; Harle, Arti S.; Kulkarni, Bhaskar D.

    2008-06-01

    Sulfur nanoparticles were synthesized from hazardous H2S gas using novel biodegradable iron chelates in w/o microemulsion system. Fe3+ malic acid chelate (0.05 M aqueous solution) was studied in w/o microemulsion containing cyclohexane, Triton X-100 and n-hexanol as oil phase, surfactant, co-surfactant, respectively, for catalytic oxidation of H2S gas at ambient conditions of temperature, pressure, and neutral pH. The structural features of sulfur nanoparticles have been characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), diffused reflectance infra-red Fourier transform technique, and BET surface area measurements. XRD analysis indicates the presence of α-sulfur. TEM analysis shows that the morphology of sulfur nanoparticles synthesized in w/o microemulsion system is nearly uniform in size (average particle size 10 nm) and narrow particle size distribution (in range of 5 15 nm) as compared to that in aqueous surfactant systems. The EDS analysis indicated high purity of sulfur (>99%). Moreover, sulfur nanoparticles synthesized in w/o microemulsion system exhibit higher antimicrobial activity (against bacteria, yeast, and fungi) than that of colloidal sulfur.

  16. 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. PMID:25476324

  17. 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.

  18. 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

    2015-03-01

    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. PMID:26262648

  19. 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.

  20. 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. PMID:27054739

  1. 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

  2. Synthesis and characterization of WO 3 nanoparticles prepared by the precipitation method: Evaluation of photocatalytic activity under vis-irradiation

    NASA Astrophysics Data System (ADS)

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

    2010-01-01

    WO 3 nanoparticles were synthesized by the precipitation method varying the time employed in the formation of their precursor in aqueous media and the calcination temperature. The WO 3 crystallization process and morphology of the synthesized samples were followed by the XRD, TEM and SEM techniques. The effects of the calcination temperature on the surface area and optical properties of the WO 3 nanoparticles were also investigated. Nanoparticles with morphologies such as square and rectangular plates and ovoid forms were observed for the different experimental conditions. WO 3 nanoparticles with different morphologies were tested for the photocatalytic degradation of organic dyes. In general, the photocatalysts showed a capacity to bleach the dye solution in the following sequence: indigo carmine (IC) > rhodamine B (rhB) > congo red (CR). The extent of mineralization was determined by means of total organic carbon (TOC) measurements, which showed a satisfactory TOC reduction (93%, within 75 h) only for IC. This value was even better than the one concerning the P-25 Degussa reference.

  3. 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.

  4. Facile Fabrication of Bi2WO6/Ag2S Heterostructure with Enhanced Visible-Light-Driven Photocatalytic Performances.

    PubMed

    Tang, Rongfeng; Su, Huaifen; Sun, Yuanwei; Zhang, Xianxi; Li, Lei; Liu, Caihua; Wang, Bingquan; Zeng, Suyuan; Sun, Dezhi

    2016-12-01

    In this report, a novel photocatalyst based on Bi2WO6/Ag2S heterostructures was prepared by a 3-mercaptopropionic acid (MPA)-assisted route at room temperature. Compared to bare Bi2WO6 and Ag2S nanoparticles, the as-formed Bi2WO6/Ag2S heterostructures exhibit enhanced photocatalytic activity for the degradation of rhodamine B (Rh B) under visible-light irradiation. This kind of enhancement in the photocatalytic activity is considered to be the synergistic effects of both the effective electron-hole separation and expansion of the light-absorption range. The pH of the solution is of vital importance to the photocatalytic activity of the as-formed Bi2WO6/Ag2S heterostructures. Under low pH value, the photosensitization process is suppressed, while under higher pH value, the photosensitization process is favored. The mechanism of the photocatalytic process was proposed by the active-species-trapping experiments, indicating that the photogenerated holes (h(+)) play a crucial role in the degradation of Rh B under visible light. The enhanced photocatalytic performance of this heterostructure makes it a promising material for the treatment of dye-containing wastewater. PMID:26951126

  5. Optical and electrochemical properties of Ni doped WO 3-MoO 3 films prepared by sol-gel process

    NASA Astrophysics Data System (ADS)

    Li, Zhuying; Zhang, Minliang; Zhang, Yan

    2007-12-01

    The electrochromic effect, change of optical transmittance with respect to the applied DC voltage,is a well-known phenomenon. The electrochromic film can be fabricated with various methods such as rf and dc sputtering, chemical vapour deposition, electron, thermal and ion cluster beams and several other methods. Sol-gel process offeres several advantages over conventional deposition method for the control of stoichiometry and film structure. It was known that WO 3 thin film doped with niobium and with Lithium exhibits a well bleaching process as compared with pure tungsten oxide film [1-4]. The presence of Li, Ta, Ti and Nb in WO 3 film improves the spectroelectrochemical response of these materials. So in this paper, we presented a mixed-metal oxide sol-gel synthesis, deposition, optical and electrochromic performances of Nickel (II) acetate doped tungsten molybdenum oxide film WO 3-MoO 3--Ni(CH 3COO) II. The range of dopant concentration was 0.75ml-7.5ml V%. Film made from WO 3-MoO 3 precursor solutions was also used for comparison. The film has been studied and characterized by ultraviolet-visible spectroscopy, X-ray diffractometry (XRD), scanning electron microscopy (SEM) and electrochemistric station. The good coloring and bleaching behaviors of doped Ni film mean that they are suitable for electrochromic material.

  6. Magnetic order and spin-flop transitions in the cobalt-doped multiferroic Mn1-xCoxWO4

    NASA Astrophysics Data System (ADS)

    Ye, Feng; Chi, Songxue; Fernandez-Baca, Jaime A.; Cao, Huibo; Liang, K.-C.; Wang, Yaqi; Lorenz, Bernd; Chu, C. W.

    2012-09-01

    We present a comprehensive single-crystal neutron diffraction investigation of the Mn1-xCoxWO4 with 0.02≤x≤0.30. At lower concentration x≤0.05, the system is quickly driven into the multiferroic phase with spin structure forming an elliptical spiral order similar to the parent compound. The reduction of electric polarization is ascribed to the tilting of the spiral plane. For x˜0.075, the magnetic structure undergoes a spin-flop transition that is characterized by a sudden rotation of the spin helix envelope into the ac plane. This spin structure persists for concentration up to x=0.15, where additional competing magnetic orders appear at low temperature. For 0.17≤x≤0.30, the system experiences another spin-flop transition and recovers the low-x spiral spin configuration. A simple commensurate spin structure with q⃗=(0.5,0,0) is found to coexist with the incommensurate spiral order. The complex evolution of magnetic structure in Co doped MnWO4 contrasts sharply with other transition metal ion doped Mn1-xAxWO4 (A=Zn, Mg, Fe) where the chemical substitutions stabilize only one type of magnetic structure. The rich phase diagram of Mn1-xCoxWO4 results from the interplay between magnetic frustration and spin anisotropy of the Co ions.

  7. Proton intercalated two-dimensional WO3 nano-flakes with enhanced charge-carrier mobility at room temperature.

    PubMed

    Zhuiykov, Serge; Kats, Eugene; Carey, Benjamin; Balendhran, Sivacarendran

    2014-12-21

    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 WO(3-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 WO(3) FETs, made of Q2D nano-flakes, with enhanced charge-carrier mobility exceeding 319 cm(2) V(-1) s(-1) comparable with the charge-carrier mobility of Q2D dichalcogenides MoS(2) and WSe(2). Analyses indicate that the enhanced electrical properties of the sub-stoichiometric WO(3-x) depend on the oxygen vacancies in the intercalated nano-flakes. These findings confirmed that Q2D sub-stoichiometric WO(3-x) is a promising material for various functional FET devices. PMID:25367432

  8. Ultrathin HNbWO6 nanosheets: facile synthesis and enhanced hydrogen evolution performance from photocatalytic water splitting.

    PubMed

    Liu, Yuhao; Xiong, Jinhua; Luo, Shuiguang; Liang, Ruowen; Qin, Na; Liang, Shijing; Wu, Ling

    2015-10-21

    Ultrathin monolayer HNbWO6 nanosheets have been successfully prepared through a simple and ultrafast ion intercalation assisted exfoliation method. These obtained highly dispersed nanosheets present enhanced photocatalytic hydrogen evolution activity compared to the nanosheets prepared by the traditionally time-consuming process. PMID:26323325

  9. 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. PMID:26775101

  10. 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. PMID:26846790

  11. 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)

  12. Oxalic acid mediated synthesis of WO{sub 3}.H{sub 2}O nanoplates and self-assembled nanoflowers under mild conditions

    SciTech Connect

    Li Linzhi; Zhao Jingzhe; Wang Yi; Li Yunling; Ma Dechong; Zhao Yan; Hou Shengnan; Hao Xinli

    2011-07-15

    Tungsten oxide hydrate (WO{sub 3}.H{sub 2}O) nanoplates and flower-like assemblies were successfully synthesized via a simple aqueous method. The effects of reaction parameters in solution on the preparation were studied. Nanoplates and nanoflowers can be selectively prepared by changing the amount of H{sub 2}C{sub 2}O{sub 4}. In-situ assembly of nanoplates to nanoflowers was also proposed for the formation of assembled nanostructures. In addition, the reaction time and temperature have important effects on the sizes of the as-obtained samples. Crystal structure, morphology, and composition of final nanostructures were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Optical properties of the synthesized samples and the growth mechanism were studied by UV-vis detection. Degradation experiments of Rhodamine B (RhB) were also performed on samples of nanoplates and nanoflowers under visible light illumination. Nanoflower sample exhibited preferable photocatalytic property to nanoplate sample. - Graphical abstract: The oxalic acid has a key role for the structure of WO{sub 3}.H{sub 2}O evolution from plates to flowers and the dehydration process of WO{sub 3}.2H{sub 2}O to WO{sub 3}.H{sub 2}O. Highlights: > Tungsten oxides hydrate was synthesized via a simple aqueous method. > The size of WO{sub 3}.H{sub 2}O was controlled by the reaction time and temperature. > The assembly of WO{sub 3}.H{sub 2}O nanoplates to nanoflowers was achieved with higher H{sub 2}C{sub 2}O{sub 4}/Na{sub 2}WO{sub 4} ratio. > Oxalic acid has a key role in the dehydration process of WO{sub 3}.2H{sub 2}O to WO{sub 3}.H{sub 2}O.

  13. Global coordination and standardisation in marine biodiversity through the World Register of Marine Species (WoRMS) and related databases.

    PubMed

    Costello, Mark J; 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; Appeltans, Ward

    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

  14. 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

  15. Iron-doping-enhanced photoelectrochemical water splitting performance of nanostructured WO3: a combined experimental and theoretical study

    NASA Astrophysics Data System (ADS)

    Zhang, Teng; Zhu, Zonglong; Chen, Haining; Bai, Yang; Xiao, Shuang; Zheng, Xiaoli; Xue, Qingzhong; Yang, Shihe

    2015-02-01

    In this paper, we have studied Fe-doping of nanostructured tungsten trioxide (WO3) and its pronounced effect in promoting the photoelectrochemical (PEC) water splitting performance. Vertically aligned Fe-doped WO3 nanoflakes on fluorine-doped tin oxide (FTO) were synthesized via the hydrothermal method. An X-ray photoelectron spectroscopy (XPS) analysis confirmed the Fe3+ substitution at the W6+ site in the prepared films. Broadened visible light absorption was observed in doped films, likely due to the formation of extra band states through doping. The Fe-doping was shown to greatly improve the PEC water splitting performance of WO3. More specifically, the 2 mol% Fe-doped WO3 achieved a photocurrent density of 0.88 mA cm-2 at 1.23 V versus RHE, approximately 30% higher than that of the undoped WO3 (0.69 mA cm-2 at 1.23 V versus RHE). This enhancement was attributed to the reduced band gap and the doping-enhanced charge carrier density as confirmed by the absorption spectra and the Mott-Schottky plots, respectively. Finally, first-principles density functional theory (DFT) calculations confirmed that the formation of oxygen vacancies was favored after Fe-doping, contributing to the increased charge carrier density in slightly doped films.In this paper, we have studied Fe-doping of nanostructured tungsten trioxide (WO3) and its pronounced effect in promoting the photoelectrochemical (PEC) water splitting performance. Vertically aligned Fe-doped WO3 nanoflakes on fluorine-doped tin oxide (FTO) were synthesized via the hydrothermal method. An X-ray photoelectron spectroscopy (XPS) analysis confirmed the Fe3+ substitution at the W6+ site in the prepared films. Broadened visible light absorption was observed in doped films, likely due to the formation of extra band states through doping. The Fe-doping was shown to greatly improve the PEC water splitting performance of WO3. More specifically, the 2 mol% Fe-doped WO3 achieved a photocurrent density of 0.88 mA cm-2 at 1

  16. 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.

  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. Nanoscale Heterostructures Based on Fe2O3@WO3-x Nanoneedles and Their Direct Integration into Flexible Transducing Platforms for Toluene Sensing.

    PubMed

    Vallejos, Stella; Gràcia, Isabel; Figueras, Eduardo; Cané, Carles

    2015-08-26

    Nanoscale heterostructures based on WO3-x nanoneedles functionalized with Fe2O3 nanoparticles are integrated directly into flexible polymer-based transducing platforms via aerosol-assisted chemical vapor deposition. Results demonstrate that the incorporation of Fe2O3 nanoparticles at the surface of WO3-x nanoneedles enhances the electronic and sensing properties of WO3-x, providing a 6-fold increase in sensitivity to toluene and low cross-sensitivity to hydrogen and ethanol. These enhanced-sensing properties are comparable to those obtained via functionalization with precious metal (Pt) nanoparticles, which are commonly used to enhance sensor performance. PMID:26251867

  19. 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.

  20. Rattle-type hollow CaWO4:Tb(3+)@SiO2 nanocapsules as carriers for drug delivery.

    PubMed

    Zhai, Xuefeng; Yu, Min; Cheng, Ziyong; Hou, Zhiyao; Ma, Ping'an; Yang, Dongmei; Kang, Xiaojiao; Dai, Yunlu; Wang, Dong; Lin, Jun

    2011-12-28

    Rattle-type hollow nanocapsules are among of the most promising candidates as drug carriers owing to their huge inner space and multifunctional material combination. In this paper, rattle-type hollow CaWO(4):Tb(3+)@SiO(2) nanocapsules with a diameter of 100-110 nm and a wall thickness around 10 nm were fabricated. The hollow silica nanospheres were used as nano-reactors and the luminescent core of CaWO(4):Tb(3+) was post-filled into the nano-reactors by a vacuum nano-casting route combined with a Pechini-type sol-gel method. Subsequently, doxorubicin hydrochloride (DOX), a model of an anti-cancer drug, is loaded into the CaWO(4):Tb(3+)@SiO(2) nanocapsules and their cell cytotoxicity, cancer cell uptake and drug release behavior are investigated in vitro. The prepared multifunctional inorganic nanocapsules show a loading capacity for DOX as high as 124 mg g(-1) and sustained-release properties. The release profile of the drug from DOX-loaded nanocapsules can last over five days. Besides, the blank CaWO(4):Tb(3+)@SiO(2) shows very low cytotoxicity against cancer cell lines (HeLa cell) while the DOX-loaded nanocapsules exhibit relatively high efficiency for killing of HeLa cells. The rapid cancer cell uptake process is observed by confocal laser scanning microscopy. The results indicate that a rattle-type hollow CaWO(4):Tb(3+)@SiO(2) nanocapsule has the potential to be used as drug carrier in therapy. Moreover, it is possible to extend the synthetic strategy in this study to other rattle-type multifunctional composites to meet various demands. PMID:21879092

  1. Investigation of the optical and structural properties of WO3 thin films with different sputtering power supplies

    NASA Astrophysics Data System (ADS)

    Chen, Hsi-Chao; Jan, Der-Jun; Chen, Chien-Han; Huang, Kuo-Ting; Luo, Yu-Siang; Chen, Jia-Min

    2012-10-01

    The purpose of this research was to investigate the optical and structural properties of tungsten oxide (WO3) thin films deposited with three different sputtering power supplies: direct current (DC), DC pulse and radio frequency (RF). These WO3 thin films were deposited on ITO glass and silicon substrate with different gas ratios of oxygen and argon (O2/Ar ratio). WO3 thin film is the role of the electrochromic window was resulted from the advantages of large variation in optical density, high response efficiency, no toxicity and low cost. The experimental results showed that optical intensity increased with the increasing of O2/Ar ratio and all films have the 950cm-1 peak which the bonding of W+6=O in Raman spectra. Hence, the O2/Ar ratio was changed from 0.4 to 0.8 to study the ability of coloring and bleaching for the three different power supplies. Anyways, the WO3 thin films had the best electrochromic property at the O2/Ar ratio of 0.7, 0.6 and 0.6 for DC, DC pulse, and RF, respectively. The transmittances could be over 75% for all films at as-deposited and the deposition rates were between 0.8 and 0.1 Ås-1. Simultaneously, the transmittance variations (ΔT) were 51%, 57% and 53% for DC, DC pulse, and RF power sources at wavelength of 550 nm, respectively. The coloration ability of WO3 thin film deposition with power supply of DC pulse was better than that of the DC and RF.

  2. 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

    2014-10-01

    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. PMID:25216058

  3. Synthesis, vibrational and luminescence studies on Eu3+:KY(WO4)2 red phosphors

    NASA Astrophysics Data System (ADS)

    Rasu, K. Kavi; Durairajan, A.; Balaji, D.; Babu, S. Moorthy

    2015-06-01

    Eu3+:KY(WO4)2 (Eu3+:KYW) phosphors were synthesized by sol-gel method using citric acid as a chelator and ethylene glycol as a binder. The crystallinity, organic liberation and tungstate bridge formation and excitation and emission properties of the synthesized phosphors were characterized by powder XRD, FT-IR, Raman and fluorescence analysis respectively. Powder XRD confirms the formation of monoclinic crystalline structure with space group C2/c. Organic liberation with respect to thermal treatments was analyzed in FT-IR. Raman results indicate different vibration mode related to monoclinic structure. The strong red emission at 615 nm (5D0→ 7F2) of the phosphors under the near UV excitation was examined by the fluorescence studies.

  4. 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.

  5. Photoresponse in thin films of WO{sub 3} grown by pulsed laser deposition

    SciTech Connect

    Roy Moulik, Samik; Samanta, Sudeshna; Ghosh, Barnali

    2014-06-09

    We report, the photoresponse behaviour of Tungsten trioxide (WO{sub 3}) films of different surface morphology, grown by using pulsed laser deposition (PLD). The Growth parameters for PLD were changed for two substrates SiO{sub 2}/Si (SO) and SrTiO{sub 3} (STO), such a way which, result nanocrystalline film on SO and needle like structured film on STO. The photoresponse is greatly modified in these two films because of two different surface morphologies. The nanocrystalline film (film on SO) shows distinct photocurrent (PC) ON/OFF states when light was turned on/off, the enhancement of PC is ∼27%. Whereas, the film with needle like structure (film on STO) exhibits significantly enhanced persistent photocurrent even in light off condition, in this case, the enhancement of PC ∼ 50% at room temperature at lowest wavelength (λ = 360 nm) at a nominal bias voltage of 0.1 V.

  6. Mid-InfRAred Camera w/wo LEns (MIRACLE) for SPICA

    NASA Astrophysics Data System (ADS)

    Wada, Takehiko; Kataza, Hirokazu; Spica Pre-Project Team

    2009-12-01

    Mid-InfRAred Camera w/wo LEns (MIRACLE) is the focal plane instrument designed for wide field imaging (6' × 6') and low-resolution spectroscopic observations (R = 100) over a wide spectral range in the mid-infrared wavelength (5-38 μm). Thanks to the SPICA’s cooled telescope, MIRACLE has a better sensitivity than JWST/MIRI at wavelengths over 20 μm and its wider FOV provides a faster mapping speed in 5-26 μm. MIRACLE opens a new wavelength region of 26-38 μm. Contiguous wavelength coverage is considered in the choice of the filter bands from the experiences in the Spitzer and AKARI observations. MIRACLE is equipped with a field stop wheel, which provides optimal slits in the spectroscopic mode and a wide FOV in the imaging mode. The results of a conceptual design study including sensitivity analysis are presented.

  7. Hydrothermal synthesis of micrometer doping CaWO4 phosphors assisted by polymerization

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    CaWO4 crystals were prepared by hydrothermal method assisting with phenol-formaldehyde polymer. The morphology can be controlled by polymer, and X-ray diffraction patterns results present a scheelite-type tetragonal structure, characteristic infrared active modes for O-W-O in the range from 500 cm‑1 to 4000 cm‑1 by Fourier transform infrared spectroscopic techniques. Raman results indicate that the crystals possess seven Raman active modes in the range from 100 cm‑1 to 1000 cm‑1. A scanning electron microscopy study reveals that the particles exhibit uniform morphology. Luminescent properties were investigated by photoluminescence measurements, multicolor phosphors were obtained when Ca2+ was substituted partly by lanthanide ions.

  8. All-solid-state electrochromic device with NiO/WO3 complementary structure

    NASA Astrophysics Data System (ADS)

    Hu, Xingfang; Chen, Xiaofeng; Li, Zhiyong

    1997-10-01

    Based on our previous studies on the rf reactive sputtered nickel oxide films with nanostructure and its electrochromism which was supposed that electrochromic effect of the films is attributed to the reversible change of the non-stoichiometry in the nanocrystalline grain boundaries and interfaces due to the injection and ejection of Li+ ions, a prototype of all-solid-state NiO/WO3 complementary electrochromic device using LixTaOy thin film as inorganic electrolyte was designed and prepared. The results indicate that the solar reflectance of the device could be modulated from 0.15 in colored state to 0.60 in bleached state with excellent cyclic reversibility, durability and high response speed (less than 0.3 sec from colored state to bleached state).

  9. Structural, morphological and optical characteristics of KGd(WO4)2 crystals

    NASA Astrophysics Data System (ADS)

    Ananyeva, G. V.; Afanasyev, I. I.; Glazov, A. I.; Mamontov, I. Y.; Merkulyayeva, T. I.

    1984-02-01

    A KGd (WO sub 4) (sub 2) crystal, suitable as active laser material with Nd (sup + 3) doping, has a low-order symmetry which makes determination and normalization of its optical characteristics difficult. Its atomic structure is described by the P/2m group of spatial symmetry. A correspondence between the principal axes and the structure of this biaxial crystal was established by X-ray structural analyses with a URS-50IM X-ray diffractometer and a model F goniometer and optical measurements. Based on this study and plotting of the stereographic projection of such a crystal, its lattice parameters and optical indicatrix are found. Its optical orientation can be described as n sub g = b and n sub pc = 20 deg with the optical axes at an 86.5 deg angle to one another lying in the plane of the crystallographic b-axis zone.

  10. Spectrally resolved microprobe cathodoluminescence of intergrowth Bi5-xLaxTiNbWO15 ferroelectrics

    NASA Astrophysics Data System (ADS)

    Ge, Wanyin; Zhu, Wenliang; Higashino, Masayuki; Li, Yongxiang; Yi, Zhiguo; Pezzotti, Giuseppe

    2007-10-01

    Spectrally resolved cathodoluminescence measurements of Bi5-xLaxTiNbWO15 (x=0-1.50) ceramics at room temperature showed three distinct luminescence bands located at about 380, 502, and 660nm, respectively, which were tentatively assigned to F+ center, oxygen vacancy-related defect and octahedron structure-related luminescence center, respectively. These assignments could be made in light of electron irradiation experiments with different exposure times. Bands related to oxygen vacancies were clearly enhanced by lanthanum doping, indicating that charge compensation occurred by the substitution of Bi for La3+ in perovskitelike structured intergrowth ferroelectrics. We observed that, for contents of La3+ x >0.75, La3+ ions entered the [Bi2O2]2+ layer according to a doping mechanism which is briefly discussed in this letter.

  11. Disclinations in C60 molecular layers on WO2/W (110 ) surfaces

    NASA Astrophysics Data System (ADS)

    Bozhko, S. I.; Taupin, V.; Lebyodkin, M.; Fressengeas, C.; Levchenko, E. A.; Radikan, K.; Lübben, O.; Semenov, V. N.; Shvets, I. V.

    2014-12-01

    A scanning tunneling microscopy study of a planar close-packed C60 hexagonal molecular layer on a WO2/W (110 ) substrate reveals the existence of C60 domains exhibiting two preferred orientations at an angle with an underlying periodic groove structure in the substrate. An analysis of the van der Waals interactions between substrate and layer retrieves the observed misorientations as those corresponding to minima in the interaction energy of the substrate-layer system. The misorientation between two C60 domains is accommodated in a tilt boundary by a linear array of molecular structural units identified as disclination dipoles, i.e., rotational defects in the hexagonal structure of the layer. A field theory of disclinations and dislocations is used to construct maps of the elastic energy, strains, curvatures, and stresses induced by the lattice defects over the layer. The predicted regions of high compression are found to overlap with those where the fullerene molecules do not undergo rotation.

  12. 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.

  13. Targeting GLI proteins in human cancer by small molecules (WO2014116651 A1): a patent evaluation.

    PubMed

    Hadden, M Kyle

    2015-05-01

    The invention reviewed in this patent evaluation is the synthesis and application of small molecule inhibitors of Gli transcriptional activity as potential anticancer agents. The oncogenic nature of Gli proteins has been traditionally associated with the hedgehog (Hh) signaling pathway; however, the recent identification of aberrant Gli activation unrelated to Hh signaling has prompted drug discovery efforts directly targeting Gli proteins. The central core of the compounds described in this patent (WO2014116651 A1) is structurally analogous to the pyrazoline scaffold previously disclosed by these inventors. Data describing the inhibitory activity of these compounds against the Hh pathway in vitro and in Hh-dependent in vivo models of human cancer are not provided. For this patent disclosure, the inventors primarily focus on the anticancer properties of their compounds in lung and lung-related malignancies. The compounds are moderately active in these models, but they do not exhibit the overall preclinical profile generally required for advancement into clinical trials. PMID:25772316

  14. 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.

  15. Structural and electrical properties of sol-gel-deposited WO3 films

    NASA Astrophysics Data System (ADS)

    Agnihotry, S. A.; Sharma, Nidhi; Deepa, M.; Kishore, Ram; Sood, K. N.; Sharma, Sudhir K.

    1999-10-01

    Amongst various sol-gel routes to deposit large area WO3 films for electrochromic applications, the one using peroxotungstic acid based precursor solution gives superior electrochromic films. Further improvements in the properties are possible by chemical modification of the precursor material and by controlling the post deposition thermal treatment. Both these parameters affect physical, structural, electrical and as a result electrochromic properties of the films significantly. A detailed study of these properties of the films deposited with precursor solution modified with various organic additives and different thermal parameters was undertaken. X-ray diffraction, electron microscopy and resistance measurements were used to characterize and compare the films. These properties of the films correlated to their electrochromic behavior are reported in this paper.

  16. Topical composition for treating diabetic cataracts: a patent evaluation (WO2015026380A1).

    PubMed

    Hao, Xin; Han, Zhongfei; Zhu, Changjin

    2016-06-01

    Diabetes mellitus is a major threat to global public health that requires long-term medical attention. In view of the potentially devastating effects of diabetes on ocular health, it highlights the urgent need of therapeutic drugs for the prevention and treatment of the diabetic complications. The patent described in this evaluation (WO2015026380A1) claimed a topical composition for treating diabetic cataracts both in animals and human beings. The composition containing a therapeutic amount of the 2R-methyl sorbinil, one of aldose reductase inhibitors, delivered to the dog's eye can exert a preventive, inhibitory, or prophylactic effect on diabetic cataracts in a statistically significant portion of the population being studied. Thus methods and strategies using new formulations of known inhibitors are promising for future use in the treatment of diabetic complications. PMID:26967920

  17. 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. PMID:27071488

  18. Increase in the work function of W/WO3 by helium plasma irradiation

    NASA Astrophysics Data System (ADS)

    Kajita, Shin; Ohta, Akio; Ishida, Tomoya; Makihara, Katsunori; Yoshida, Tomoko; Ohno, Noriyasu

    2015-12-01

    Helium plasma irradiation to tungsten leads to formation of helium clusters, helium bubbles, and fiberform nanostructures near the surface. In this study, tungsten samples exposed to helium plasmas are analyzed by X-ray photoelectron spectroscopy in detail. The W 4f spectra and valence band spectra show chemical composition and electronic state of the surface. It was found that significant differences were not identified on the electronic state between the helium plasma irradiated and pristine samples when the degree of oxidization was the same level. From a low kinetic energy cut-off of X-ray photoelectron spectrum, the work function of the samples was measured. It was found that helium plasma irradiation increased the work function by approximately 0.5 eV when WO3/W was higher than unity. The possible mechanism to arise the difference in the work function is discussed.

  19. 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.

  20. Cosmic ray calibration of the PbWO4 crystal electromagnetic calorimeter of CMS

    SciTech Connect

    Franzoni, G.

    2006-10-27

    The Compact Muon Solenoid experiment at the CERN LHC features a high precision PbWO4 crystal electromagnetic calorimeter. Each crystal is first precalibrated with a radioactive source and by means of optical measurements. After the assembly, each supermodule (1700 crystals) is exposed to comics rays.The comparison between intercalibration obtained from cosmic muons and electrons from test beam was performed at the end of 2004 for an initial set of 130 channels and showed that a precalibration with a statistical precision of 1 to 2% can be achieved within approximately one week. An important aspect of the comics muons analysis is that it is entirely based on the calorimeter data, without using any external tracking device.We will present the setup and results from the 2004 test as well as recent data recorded on many supermodule.

  1. High-temperature anodized WO3 nanoplatelet films for photosensitive devices.

    PubMed

    Sadek, Abu Z; Zheng, Haidong; Breedon, Michael; Bansal, Vipul; Bhargava, Suresh K; Latham, Kay; Zhu, Jianmin; Yu, Leshu; Hu, Zheng; Spizzirri, Paul G; Wlodarski, Wojtek; Kalantar-zadeh, Kourosh

    2009-08-18

    Anodization at elevated temperatures in nitric acid has been used for the production of highly porous and thick tungsten trioxide nanostructured films for photosensitive device applications. The anodization process resulted in platelet crystals with thicknesses of 20-60 nm and lengths of 100-1000 nm. Maximum thicknesses of approximately 2.4 microm were obtained after 4 h of anodization at 20 V. X-ray diffraction analysis revealed that the as-prepared anodized samples contain predominantly hydrated tungstite phases depending on voltage, while films annealed at 400 degrees C for 4 h are predominantly orthorhombic WO3 phase. Photocurrent measurements revealed that the current density of the 2.4 microm nanostructured anodized film was 6 times larger than the nonanodized films. Dye-sensitized solar cells developed using these films produced 0.33 V and 0.65 mA/cm2 in open- and short-circuit conditions. PMID:19627158

  2. Enhanced electrical properties in sub-10-nm WO3 nanoflakes prepared via a two-step sol-gel-exfoliation method

    PubMed Central

    2014-01-01

    The morphology and electrical properties of orthorhombic β-WO3 nanoflakes with thickness of ~7 to 9 nm were investigated at the nanoscale with a combination of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), current sensing force spectroscopy atomic force microscopy (CSFS-AFM, or PeakForce TUNA™), Fourier transform infra-red absorption spectroscopy (FTIR), linear sweep voltammetry (LSV) and Raman spectroscopy techniques. CSFS-AFM analysis established good correlation between the topography of the developed nanostructures and various features of WO3 nanoflakes synthesized via a two-step sol-gel-exfoliation method. It was determined that β-WO3 nanoflakes annealed at 550°C possess distinguished and exceptional thickness-dependent properties in comparison with the bulk, micro and nanostructured WO3 synthesized at alternative temperatures. PMID:25221453

  3. Fe3O4@Bi2WO6 Core-Shell Structured Microspheres: Facile Construction and Magnetically Recyclable Photocatalytic Activity Under Visible-Light.

    PubMed

    Zhou, Yu-Xue; Tong, Ling; Zeng, Xiang-Hua; Chen, Xiao-Bing

    2015-12-01

    Core-shell structured Fe3O4@Bi2WO6 composite microspheres (Fe3O4 microspheres as core and Bi2WO6 nanoplates as shell) have been fabricated in a facile and cost effective reflux way. Such fabricated Fe3O4@Bi2WO6 composites show good visible-light driven photocatalytic performance on degradation of rhodamine B (RhB) from solution in presence of H2O2. More importantly, they can be easily harvested from aqueous system for recycle with small loss of their photocatalytic activity upon applying an external magnet. However, this combination of Bi2WO6 photocatalytic activity and Fe3O4 magnetic property endows such composite with a bright perspective in low cost waste water treatment by taking full advantage of solar energy. PMID:26682426

  4. Optimum Cycle Length and Discharge Burnup for Nuclear Fuel; Phase II: Results Achievable with Enrichments Greater than 5 w/o

    SciTech Connect

    J. Secker, et al

    2002-09-30

    The report evaluates increasing enrichment to achieve lower fuel cycle costs. Increasing enrichment 6 w/o does not reach the optimum point. Further increase is possible before the optimum will be reached.

  5. Structure, optical and phonon properties of bulk and nanocrystalline Al2-xScx(WO4)3 solid solutions doped with Cr3+

    NASA Astrophysics Data System (ADS)

    Mączka, M.; Hermanowicz, K.; Pietraszko, A.; Yordanova, A.; Koseva, I.

    2014-01-01

    Pure and Cr3+ doped nanosized Al2-xScx(WO4)3 solid solutions were prepared by co-precipitation method as well as Al2-xScx(WO4)3 single crystals were grown by high-temperature flux method. The obtained samples were characterized by X-ray, Raman, IR, absorption and luminescence methods. Single crystal X-ray diffraction showed that AlSc(WO4)3 is orthorhombic at room temperature with space group Pnca and trivalent cations are statistically distributed. Raman and IR studies showed that Al2-xScx(WO4)3 solid solutions show "two mode" behavior. They also showed that vibrational properties of nanosized samples have been weakly modified in comparison with the bulk materials. The luminescence and absorption spectra revealed that chromium ions occupy two sites of weak and strong crystal field strength.

  6. Polar Order and Frustrated Antiferromagnetism in Perovskite Pb2MnWO6 Single Crystals.

    PubMed

    Ivanov, Sergey A; Bush, Alexander A; Stash, Adam I; Kamentsev, Konstantin E; Shkuratov, Valerii Ya; Kvashnin, Yaroslav O; Autieri, Carmine; Di Marco, Igor; Sanyal, Biplab; Eriksson, Olle; Nordblad, Per; Mathieu, Roland

    2016-03-21

    Single crystals of the multiferroic double-perovskite Pb2MnWO6 have been synthesized and their structural, thermal, magnetic and dielectric properties studied in detail. Pure perovskite-phase formation and stoichiometric chemical composition of the as-grown crystals are confirmed by X-ray single-crystal and powder diffraction techniques as well as energy-dispersive X-ray and inductively coupled plasma mass spectrometry. Detailed structural analyses reveal that the crystals experience a structural phase transition from the cubic space group (s.g.) Fm3̅m to an orthorhombic structure in s.g. Pn21a at about 460 K. Dielectric data suggest that a ferrielectric phase transition takes place at that same temperature, in contrast to earlier results on polycrystalline samples, which reported a transition to s.g. Pnma and an antiferroelectric low-temperature phase. Magnetic susceptibility measurements indicate that a frustrated antiferromagnetic phase emerges below 8 K. Density functional theory based calculations confirm that the cationic order between Mn and W is favorable. The lowest total energy was found for an antiferromagnetically ordered state. However, analyses of the calculated exchange parameters revealed strongly competing antiferromagnetic interactions. The large distance between the magnetic atoms, together with magnetic frustration, is shown to be the main reason for the low value of the ordering temperature observed experimentally. We discuss the structure-property relationships in Pb2MnWO6 and compare these observations to reported results on related Pb2BWO6 perovskites with different B cations. PMID:26954581

  7. Tuning the ferroelectric polarization in AA'MnWO6 double perovskites through A cation substitution.

    PubMed

    Young, Joshua; Stroppa, Alessandro; Picozzi, Silvia; Rondinelli, James M

    2015-06-21

    Recent experimental and theoretical work has shown that the double perovskite NaLaMnWO(6) exhibits antiferromagnetic ordering owing to the Mn d states, and computational studies further predict it to exhibit a spontaneous electric polarization due to an improper mechanism for ferroelectricity [King et al., Phys. Rev. B: Condens. Matter, 2009, 79, 224428; Fukushima et al., Phys. Chem. Chem. Phys., 2011, 13, 12186], which make it a candidate multiferroic material. Using first-principles density functional calculations, we investigate nine isostructural and isovalent AA'MnWO(6) double perovskites (A = Na, K, and Rb; A' = La, Nd, and Y) with the aim of articulating crystal-chemistry guidelines describing how to enhance the magnitude of the electric polarization through chemical substitution of the A-site while retaining long-range magnetic order. We find that the electric polarization can be enhanced by up to 150% in compounds which maximize the difference in the ionic size of the A and A' cations. By examining the tolerance factors, bond valences, and structural distortions (described by symmetry-adapted modes) of the nine compounds, we identify the atomic scale features that are strongly correlated with the ionic and electronic contributions to the electric polarization. We also find that each compound exhibits a purely electronic remnant polarization, even in the absence of a displacive polar mode. The analysis and design strategies presented here can be further extended to additional members of this family (B = Fe, Co, etc.), and the improper ferroelectric nature of the mechanism allows for the decoupling of magnetic and ferroelectric properties and the targeted design of novel multiferroics. PMID:25579503

  8. 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.

  9. 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

  10. α-Fe{sub 2}O{sub 3} modified Bi{sub 2}WO{sub 6} flower-like mesostructures with enhanced photocatalytic performance

    SciTech Connect

    Wu, Qing-Song; Feng, Yan; Zhang, Guo-Ying Sun, Ya-Qiu; Xu, Yan-Yan; Gao, Dong-Zhao

    2014-01-01

    Graphical abstract: - Highlights: • α-Fe{sub 2}O{sub 3}/Bi{sub 2}WO{sub 6} heterostructures were facilely fabricated by an impregnation method. • The Bi{sub 2}WO{sub 6} matrix was modified by α-Fe{sub 2}O{sub 3} nanoparticles of 10–20 nm on the surface. • The visible-light absorption region of the composite was effectively red-shifted. • The composite exhibited enhanced photocatalytic activity to RhB below Fe-0.4%. • The band gap coupling effect between α-Fe{sub 2}O{sub 3} and Bi{sub 2}WO{sub 6} was interpreted. - Abstract: α-Fe{sub 2}O{sub 3} modified Bi{sub 2}WO{sub 6} mesostructures were facilely prepared by an impregnation method. The characterizations of phase structure, morphology, microstructure, UV–vis absorption, photoluminescence, BET and solar simulated photocatalytic behavior were systematically conducted. The Fe{sub 2}O{sub 3}/Bi{sub 2}WO{sub 6} heterostructure with a Fe mass percentage in 0.05–0.2% presented obviously enhanced photocatalytic activity for the degradation of Rhodamine B than pristine Bi{sub 2}WO{sub 6}. In particular, the apparent reaction rate constant with Fe-0.1% was 2.24-folds of that of pure Bi{sub 2}WO{sub 6}. UV–vis diffuse reflectance spectra showed that the modification of α-Fe{sub 2}O{sub 3} broadened the visible light absorption of Bi{sub 2}WO{sub 6}. The decreased photoluminescence indicated an effective suppression of the recombination of electron–hole pairs at Fe{sub 2}O{sub 3}/Bi{sub 2}WO{sub 6} interface. The band-gap coupling effect between Fe{sub 2}O{sub 3} and Bi{sub 2}WO{sub 6} was interpreted via comparison of relative valence and conductance potentials, which confirmed an irreversible flow of electrons and holes in the interface of Fe{sub 2}O{sub 3}/Bi{sub 2}WO{sub 6}. Moreover, the composite showed excellent circulation stability, suggesting potential application in dealing with environmental pollutions.

  11. Comparison of the acidities of WO/sub 3//Al/sub 2/O/sub 3/ and ultrastable faujasite catalysts

    SciTech Connect

    Soled, S.L.; McVicker, G.B.; Murrell, L.L.; Sherman, L.G.; Dispenziere, N.C. Jr.; Hsu, S.L.; Waldman, D.

    1988-06-01

    The acidity of WO/sub 3/ on ..gamma..-alumina is compared with that of ultrastable faujasite using both base adsorption techniques and model compound conversion studies. The addition of WO/sub 3/ to ..gamma..-alumina introduces Broensted acidity, and the density of Broensted sites is increased by high-temperature calcination. The acid sites displayed by the supported tungsten oxide catalyst are considerably weaker than those found in ultrastable faujasite.

  12. 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.

  13. 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.

  14. Solvent directed fabrication of Bi{sub 2}WO{sub 6} nanostructures with different morphologies: Synthesis and their shape-dependent photocatalytic properties

    SciTech Connect

    Mi, Yuwei; Zeng, Suyuan; Li, Lei; Zhang, Qingfu; Wang, Suna; Liu, Caihua; Sun, Dezhi

    2012-09-15

    Graphical abstract: The morphologies of the Bi{sub 2}WO{sub 6} nanostructures can be easily tuned by altering the solvent composition during the reaction, which will yield flower-like, pancake-like and tubular nanostructures, respectively. Highlights: ► The morphologies of Bi{sub 2}WO{sub 6} can be controlled by tuning the solvent composition. ► The effects of solvent on the morphologies of Bi{sub 2}WO{sub 6} were carefully investigated. ► The growth mechanisms for the as-prepared samples were investigated. ► The morphologies of the samples greatly affect their photocatalytic activities. -- Abstract: In this work, Bi{sub 2}WO{sub 6} with complex morphologies, namely, flower-like, pancake-like, and tubular shapes have been controllably synthesized by a facile solvothermal process. The as-obtained samples are systematically investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). The effects of solvents on the morphologies of Bi{sub 2}WO{sub 6} nanostructures are systematically investigated. According to the time-dependent experiments, a two-step growth mode basing on Ostwald ripening process and self-assembly has been proposed for the formation of the flower-like and pancake-like Bi{sub 2}WO{sub 6} nanostructures. The photocatalytic properties of Bi{sub 2}WO{sub 6} nanostructures are strongly dependent on their shapes, sizes, and structures for the degradation of rhodamine B (RhB) under visible-light irradiation. The deduced reasons for the differences in the photocatalytic activities of these Bi{sub 2}WO{sub 6} nanostructures are further discussed.

  15. Sonochemical degradation of methyl orange in the presence of Bi2WO6: Effect of operating parameters and the generated reactive oxygen species.

    PubMed

    He, Ling-Ling; Liu, Xian-Ping; Wang, Yong-Xia; Wang, Zhi-Xin; Yang, Yan-Jie; Gao, Yan-Ping; Liu, Bin; Wang, Xin

    2016-11-01

    The Bi2WO6 was prepared by the hydrothermal method and its sonocatalytic activity was studied in the degradation of methyl orange (MO) solutions. The effects of catalytic activity of Bi2WO6 on dye were inspected by the change in absorbance of dye with UV-vis spectrometer. The influences of operational parameters such as the addition amount of Bi2WO6, pH, the initial concentration of dyes, ultrasonic power and irradiation time on the degradation ratio were investigated. In addition, the obtained results indicated that the kinetics of sonochemical reactions of MO were consistent with the pseudo first-order kinetics and Bi2WO6 had excellent reusability and stability during the sonochemical degradation processes. The generation and kinds of reactive oxygen species (ROS) and their influence on the sonochemical degradation of MO were determined by the methods of oxidation-extraction spectrophotometry and ROS scavengers. The results indicate that the degradation of MO in the presence of Bi2WO6 under ultrasonic irradiation is related to the generation of ROS, in which both singlet molecular oxygen ((1)O2) and hydroxyl radical (OH) play important roles in the sonochemical degradation of MO. These experimental results provide a sound foundation for the further development of Bi2WO6 as a sonocatalyst in wastewater treatment. PMID:27245960

  16. 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.

  17. 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.

  18. A novel nitrite biosensor based on the direct electron transfer hemoglobin immobilized in the WO3 nanowires with high length-diameter ratio.

    PubMed

    Liu, Hui; Duan, Congyue; Yang, Chenhui; Chen, Xianjin; Shen, Wanqiu; Zhu, Zhenfeng

    2015-08-01

    WO3 nanowires (WO3NWs) with high length-diameter ratio have been synthesized through a simple synthetic route without any additive and then used to immobilize hemoglobin (Hb) to fabricate a mediator-free biosensor. The morphology and structure of WO3NWs were characterized by scanning electron microscopy, transmission electronic microscopy and X-ray diffraction. Spectroscopic and electrochemical results revealed that WO3NWs are an excellent immobilization matrix with biocompatibility for redox protein, affording good protein bioactivity and stability. Meanwhile, due to unique morphology and property of the WO3 nanowires, the direct electron transfer of Hb is facilitated and the prepared biosensors displayed good performance for the detection of nitrite with a wide linear range of 1 to 4200 μM, as well as an extremely low detection limit of 0.28 μM. The WO3 nanowires with high length-diameter ratio could be a promising matrix for the fabrication of mediator-free biosensors, and may find wide potential applications in environmental analysis and biomedical detection. PMID:26042689

  19. Investigation of the La2O3-Nb2O5-WO3 ternary phase diagram: Isolation and crystal structure determination of the original La3NbWO10 material

    NASA Astrophysics Data System (ADS)

    Vu, T. D.; Barre, M.; Adil, K.; Jouanneaux, A.; Suard, E.; Goutenoire, F.

    2015-09-01

    In the course of the exploration of the La2O3-WO3-Nb2O5 ternary phase diagram, a new compound with the formula La3NbWO10 was discovered. Its structure was determined from a combination of powder X-ray and neutron diffraction data. It crystallizes in the tetragonal space group P42/nmc (no. 137) with the lattice parameters: a=10.0807(1) Å; c=12.5540(1) Å. The structure is built up from infinite ribbons of octahedra (W/Nb)O5 which are perpendicular to each other, lanthanum ions being distributed around these ribbons. The electrical properties of this compound were investigated on sintered pellets by means of complex impedance spectroscopy.

  20. 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. PMID:26372831

  1. Sequence of phase transitions induced by chemical composition and high temperature in [Ba2CaWO6](1-x)[Sr2CaWO6]x double perovskite tungsten oxides

    NASA Astrophysics Data System (ADS)

    Mirinioui, F.; Manoun, Bouchaib; Tamraoui, Y.; Lazor, P.

    2015-12-01

    [Ba2CaWO6]1-x[Sr2CaWO6]x (0≤x≤1) materials were synthesized by the high temperature solid state reaction and firing methods, and characterized using techniques of X-ray diffraction and Raman spectroscopy. The crystal structures were determined by Rietveld refinements on the laboratory X-ray powder diffraction data. As a function of composition, upon increasing the strontium content, the samples exhibit a sequence of three phase transitions: from cubic (Fm 3 ̅m) to tetragonal (I4/m) to monoclinic structural phases (I2/m, P21/n). These transitions have been confirmed by Raman studies Fm 3 bar m x = 0 → I 4 / m 0.1 ≤ x ≤ 0.2 → I 2 / m 0.3 ≤ x ≤ 0.5 → P21 / n 0.6 ≤ x ≤ 1 Furthermore, increasing the temperature for the compositions [Ba2CaWO6]1-x[Sr2CaWO6]x (0.1≤x<1), manifests the P21/n to I2/m, the I2/m to I4/m and the I4/m to Fm 3 ̅m phase transitions. For the compositions (0.1≤x≤0.2) the tetragonal to cubic phase transition is well illustrated. For the room temperature I2/m monoclinic compositions, two phase transitions were observed for all the compositions with x ranging from 0.3 to 0.5: from the monoclinic (I2/m) to tetragonal (I4/m), and from I4/m to Fm 3 ̅m structures. Finally, for the room temperature P21/n monoclinic compositions, only two phase transitions are observed in the temperature range probed by Raman spectroscopy, the temperature was not high enough to reach the tetragonal-to-cubic phase transition.

  2. Catalysis on Pd/WO{sub 3} and Pd/WO{sub 2}: Effect of the modifications of the surface states due to redox treatments on the skeletal rearrangement of hydrocarbons. Part 1: Physical and chemical characterizations of catalysts by BET, TPR, XRD, XAS, and XPS

    SciTech Connect

    Bigey, C.; Hilaire, L.; Maire, G.

    1999-06-10

    Catalysts containing tungsten oxides have been investigated in various reactions: olefins metathesis, propene oxidation, butene isomerization, hydrodesulfurization, or NO{sub x} reduction. Bulk and surface properties of Pd/WO{sub 3} and Pd/WO{sub 2} catalysts were studied using temperature programmed reduction, X-ray diffraction, X-ray absorption, and X-ray photoelectron spectroscopies. Special attention was paid to the oxidation state of tungsten upon reduction under hydrogen at 350 and 600 C. The influence of oxidation treatments was also studied. Results showed that reduction at 350 C led to the transformation of bulk WO{sub 3} into the stable W{sub 20}O{sub 58} phase. At higher reduction temperature and also at 350 C, if the support WO{sub 3} was calcined before impregnation, metallic tungsten was detected and the authors postulated that this transformation starts with the formation of the metastable W{sub 3}O phase via W{sub 29}O{sub 58}. All these transformations concern the surface as well as the bulk for Pd/WO{sub 3} catalysts and the WO{sub 3} contamination layer only for Pd/WO{sub 2} catalyst. WO{sub 2} seems more difficult to reduce than WO{sub 3} even if the latter becomes less reducible after oxidation treatment. Autoreduction of the palladium salt was suggested on these catalysts, resulting both from the pretreatment of the supports and the nature of the Pd salt. Addition of a metal to bulk oxides facilitates their reducibility and allows one to obtain a stable surface state.

  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. PMID:21860074

  4. Mesoporous WO3 Nanofibers with Protein-Templated Nanoscale Catalysts for Detection of Trace Biomarkers in Exhaled Breath.

    PubMed

    Kim, Sang-Joon; Choi, Seon-Jin; Jang, Ji-Soo; Kim, Nam-Hoon; Hakim, Meggie; Tuller, Harry L; Kim, Il-Doo

    2016-06-28

    Highly selective detection, rapid response (<20 s), and superior sensitivity (Rair/Rgas> 50) against specific target gases, particularly at the 1 ppm level, still remain considerable challenges in gas sensor applications. We propose a rational design and facile synthesis concept for achieving exceptionally sensitive and selective detection of trace target biomarkers in exhaled human breath using a protein nanocage templating route for sensitizing electrospun nanofibers (NFs). The mesoporous WO3 NFs, functionalized with well-dispersed nanoscale Pt, Pd, and Rh catalytic nanoparticles (NPs), exhibit excellent sensing performance, even at parts per billion level concentrations of gases in a humid atmosphere. Functionalized WO3 NFs with nanoscale catalysts are demonstrated to show great promise for the reliable diagnosis of diseases. PMID:27166639

  5. In situ microscopy of rapidly heated nano-Al and nano-Al/WO{sub 3} thermites

    SciTech Connect

    Sullivan, Kyle T.; Zachariah, Michael R.; Chiou, Wen-An; Fiore, Richard

    2010-09-27

    The initiation and reaction mechanism of nano-Al and nano-Al thermites in rapid heating environments is investigated in this work. A semiconductor-based grid/stage was used, capable of in situ heating of a sample from room temperature to 1473 K, and at a rate of 10{sup 6} K/s, inside an electron microscope. Nano-Al was rapidly heated in a transmission electron microscope, and before and after images indicate that the aluminum migrates through the shell, consistent with a diffusion-based mechanism. A nano-Al/WO{sub 3} composite was then heated in a scanning electron microscope. The results indicate that a reactive sintering mechanism is occurring for the nano-Al/WO{sub 3} thermite, as the products are found to be in surface contact and significantly deformed after the heating pulse.

  6. 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.

  7. Preparation, characterization of C/Fe-Bi2WO6 nanosheet composite and degradation application of norfloxacin in water.

    PubMed

    Chen, Shijie; Li, Yingjie; Lü, Renjiang; Wang, Peng

    2013-08-01

    A novel C/Fe-Bi2WO6 nanosheet composite photocatalyst combining the properties of both semiconductor and Fenton like catalyst was prepared via a two-step method involving Resin carbonization and hydrothermal process. The samples were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS), Fourier transformed infrared spectroscopy (FT-IR) and nitrogen adsorption-desorption measurements. Structure analyses indicated that C/Fe-Bi2WO6 presented a nanosheet and macro-meso dual porosity structure. The as-prepared composite exhibited high efficiency in the photocatalytic decomposition of norfloxacin (NOR) by the assistance of H2O2. This method is promising due to its inexpensive starting materials and good photocatalyst for degradation of emerging micropollutants. PMID:23882806

  8. Single crystal growth of Yb doped NaGd(WO{sub 4}){sub 2} and structural and spectroscopic studies

    SciTech Connect

    Singh, S. G.; Singh, A. K.; Desai, D. G.; Tiwari, B.; Tyagi, M.

    2014-04-24

    High quality single crystals of NaGd(WO{sub 4}){sub 2} doped with 5 mol % Yb and oriented along <001> have been grown by the Czochralski technique in Ar atmosphere. The tetragonal space group I41/a accounts for all the reflections observed in the powder X-ray diffraction analysis. Polarized optical spectroscopy at room temperature revealed a direction dependence of absorption at different wavelength. As a novel uniaxial laser host for Yb{sup 3+}, NaGd(WO{sub 4}){sub 2} is characterized with respect to its transparency and band-edge. The emission spectrum of Yb{sup 3+} (excitation: 980-990 nm diode laser) was also recorded.

  9. Fabrication and morphology control of BaWO 4 thin films by microwave assisted chemical bath deposition

    NASA Astrophysics Data System (ADS)

    Wang, Rui; Liu, Chen; Zeng, Jia; Li, KunWei; Wang, Hao

    2009-04-01

    Highly crystallized barium tungstate (BaWO 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 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.

  10. Hydrothermal synthesis and photoluminescence of SrWO{sub 4}:Tb{sup 3+} novel green phosphor

    SciTech Connect

    Liao Jinsheng; Qiu Bao; Wen Herui; Chen Jinglin; You Weixiong

    2009-09-15

    Tb{sup 3+}-doped SrWO{sub 4} phosphors with a scheelite structure have been prepared by hydrothermal reaction. X-ray powder diffraction, field-emission scanning electron microscopy, photoluminescence excitation and emission spectra and decay curve were used to characterize the resulting samples. Scanning electron microscopy image showed that the obtained SrWO{sub 4}:Tb{sup 3+} phosphors appeared to be nearly spherical and their sizes ranged from 1 to 3 {mu}m. Photoluminescence spectra indicated the phosphors emitted strong green light centered at 545 nm under ultraviolet light excitation. Because 12 at.% SWO{sub 4}:Tb{sup 3+} phosphor exhibits intensive green emission under 254 nm excitation in comparison with the commercial green fluorescent lamp phosphor (LaPO{sub 4}:Ce,Tb), the excellent luminescence properties make it a new promising green phosphor for fluorescent lamps application.

  11. WO3-α-Fe2O3 composite photoelectrodes with low onset potential for solar water oxidation.

    PubMed

    Zhao, Peng; Kronawitter, Coleman X; Yang, Xiaofang; Fu, Jie; Koel, Bruce E

    2014-01-28

    The physical and photoelectrochemical properties of a composite oxide photoelectrode comprised of α-Fe2O3 and WO3 crystals is investigated. The composite films exhibit a water oxidation photocurrent onset potential as low as 0.43 V vs. RHE, a value considerably lower than that of pure α-Fe2O3 photoanodes prepared in comparable synthesis conditions. This result represents one of the lowest onset potentials measured for hematite-based PEC water oxidation systems. Compositional analysis by X-ray Photoelectron Spectroscopy and Energy Dispersive Spectroscopy indicates the composition of the films differs between the surfaces and bulk, with tungsten found to be concentrated in the surface region. Post-reaction Raman spectroscopy characterization demonstrates that water interacts with surface WO3 crystals, an event that is associated with the formation of a hydrated form of the oxide. PMID:24323202

  12. Synthesis and tuning orange to green up-conversion color in Y6WO12:Er/Yb phosphor

    NASA Astrophysics Data System (ADS)

    Xue, Bing; Sun, Jiayue

    2013-12-01

    Spherical Yb3+, Er3+ co-doped Y6WO12 upconversion luminescence (UC) phosphors are prepared by the co-precipitation method. It is found that the phosphors presented uniform spheres at a wide range of annealing the precursors from 600 °C to 900 °C. With increasing the temperature, the particle size has no significant change, but the surface changed from smooth to rough. Further, under 980 nm near infrared (NIR) excitation, the upconversion intensity enhanced with increasing heating temperature, attributing to the more Er3+ incorporated into the Y6WO12 host. Notably, the luminescent colors of the samples could be modulated by changing the annealing temperatures. On the process of increasing heat-treatment temperature from 600 °C to 900 °C, the upconversion emission was tunable from orange to green, which provides a new channel to achieve materials emitting different colors. At last, the possible mechanisms involved were discussed.

  13. Efficient diode-pumped Nd:KGd(WO4)2 laser grown by top nucleated floating crystal method

    NASA Astrophysics Data System (ADS)

    Boulon, Georges; Metrat, G.; Muhlstein, N.; Brenier, Alain; Kravchik, Leonid; Kalisky, Yehoshua Y.

    2003-04-01

    Diode pumping of a stress-free, Nd(5%at.):KGd(WO4)2, grown by top nucleated floating crystal (TNFC) method, is presented. The diode-pumped laser was operated both in the free-running and passively Q-switched operating modes. Under optimized conditions of resonator and optics, the disk (1.3 mm in thickness), produced at room temperature an efficient free-running, TEM00 output with maximum power of 0.4 W, with 75% slope efficiency and 51% total laser efficiency. The results presented here indicate the potential Nd:KGd(WO4)2 crystals grown by TNFC growth method, as candidates for concentrated, stress free diode pumped microlasers in a large variety of wavelengths, including the eye-safe range.

  14. 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. PMID:27038580

  15. 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.

  16. Effect of Sensors on the Reliability and Control Performance of Power Circuits in the Web of Things (WoT).

    PubMed

    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

  17. Nanoflower-Like Bi2 WO6 Encapsulated in ORMOSIL as a Novel Photocatalytic Antifouling and Foul-Release Coating.

    PubMed

    Scandura, Gabriele; Ciriminna, Rosaria; Xu, Yi-Jun; Pagliaro, Mario; Palmisano, Giovanni

    2016-05-17

    Herein, the first multi-purpose antifouling and foul-release photocatalytic coating based on ORMOSIL thin films doped with nanoflower-like Bi2 WO6 is described. Irradiation with visible light of the new films immersed in water produces significant amounts of H2 O2 by photocatalytic oxidation of water, and allows the degradation of (bio)organic pollutants at the outer surface of the xerogel film. PMID:26945837

  18. Sol-gel processed MoO3 and WO3 thin films for use as selective chemosensors

    NASA Astrophysics Data System (ADS)

    Gouma, Perena; Comini, Elisabetta; Sberveglieri, Giorgio

    2004-03-01

    Selective detection of small amounts of toxic gases, such as ammonia and CO is very important to environmental monitoring as well as for medical diagnoses. MoO3 and WO3 have been identified as suitable materials for detecting these gases with high sensitivity. Sol-gel processed thin films of MoO3, WO3 and their combination have been prepared at SUNY Stony Brook by the hydrolysis of metal alkoxide precursors followed by spin coating and were deposited on alumina heater/electrode containing substrates that were produced by the Brescia group. Sensing tests were carried out in the state-of-the-art gas sensor testing facilities available in Brescia, where the electrical resistance of sensor arrays was recorded as a function of gas concentration, for various combinations of gases (including ammonia, CO, NO2, Methanol, isoprene, etc) at 10% relative humidity and at temperatures ranging from 400-500°C. The MoO3-WO3 composite system showed the best stability at the highest testing temperature. The sensing results obtained are correlated with the structural characteristics of the sensing films. This work has been carried out as a joint collaboration between the Advanced Materials Characterization Laboratory of SUNY Stony Brook (USA; the Sensor Lab at the University of Brescia Italy; was funded by a NSF-AAAS (WISC) grant awarded to Perena Gouma.

  19. 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

    2015-02-01

    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. PMID:25448939

  20. 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.