The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Giorgio Sberveglieri - One of the best experts on this subject based on the ideXlab platform.
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Detection of landfill gases by chemoresistive sensors based on titanium, molybdenum, Tungsten Oxides
IEEE Sensors Journal, 2005Co-Authors: Elisabetta Comini, Vincenzo Guidi, Matteo Ferroni, Giorgio SberveglieriAbstract:Monitoring of the gases produced in landfills is a major task nowadays for the environmental safety of the areas neighboring garbage dumps. We approached the problem via solid-state chemoresistive gas sensors to detect typical complex organic gases produced by landfills, i.e., carbon sulfide, methyl sulfide, and xylene. We have tested Ti, W, and Mo mixed-oxide thin films deposited by reactive sputtering and processed through the selective sublimation technique. We recorded a remarkable response toward carbon disulfide and xylene below the attention level for these gases.
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sub ppm no2 sensors based on nanosized thin films of titanium Tungsten Oxides
Sensors and Actuators B-chemical, 1996Co-Authors: P Nelli, Giorgio Sberveglieri, Laura E Depero, M Ferroni, S Groppelli, V Guidi, F Ronconi, L SangalettiAbstract:Abstract We describe the preparation of thin films of TiWO 3 obtained by means of r.f. sputtering deposition followed by a thermal oxidation. The sensing characteristics of these thin films were obtained by measuring the response towards NO 2 in the interval 0.5–20 ppm and to other interfering gases like ethyl alcohol, CH 4 and CO; the influence of water vapour to the response towards NO 2 was also investigated. The material seems to be a promising detector of NO 2 for environmental monitoring.
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iii inorganic materials for sensorssub ppm no2 sensors based on nanosized thin films of titanium Tungsten Oxides
Sensors and Actuators B-chemical, 1996Co-Authors: P Nelli, Laura E Depero, M Ferroni, S Groppelli, V Guidi, F Ronconi, L Sangaletti, Giorgio SberveglieriAbstract:We describe the preparation of thin films of TiWO3 obtained by means of r.f. sputtering deposition followed by a thermal oxidation. The sensing characteristics of these thin films were obtained by measuring the response towards NO2 in the interval 0.5–20 ppm and to other interfering gases like ethyl alcohol, CH4 and CO; the influence of water vapour to the response towards NO2 was also investigated. The material seems to be a promising detector of NO2 for environmental monitoring.
Enrique Iglesia - One of the best experts on this subject based on the ideXlab platform.
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kinetics and mechanism of oxidative dehydrogenation of propane on vanadium molybdenum and Tungsten Oxides
Journal of Physical Chemistry B, 2000Co-Authors: Kaidong Chen, And Alexis T Bell, Enrique IglesiaAbstract:The effect of cation identity on oxidative dehydrogenation (ODH) pathways was examined using two-dimensional VOx, MoOx, and WOx structures supported on ZrO2. The similar kinetic rate expressions obtained on MoOx and VOx catalysts confirmed that oxidative dehydrogenation of propane occurs via similar pathways, which involve rate-determining C−H bond activation steps using lattice oxygen atoms. The activation energies for propane dehydrogenation and for propene combustion increase in the sequence VOx/ZrO2 < MoOx/ZrO2 < WOx/ZrO2; the corresponding reaction rates decrease in this sequence, suggesting that turnover rates reflect C−H bond cleavage activation energies, which are in turn influenced by the reducibility of these metal Oxides. Propane ODH activation energies are higher than for propene combustion. This leads to an increase in maximum alkene yields and in the ratio of rate constants for propane ODH and propene combustion as temperature increases. This difference in activation energy (48−61 kJ/mol) be...
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solid acid catalysts based on supported Tungsten Oxides
Topics in Catalysis, 1998Co-Authors: David G Barton, Stuart L Soled, Enrique IglesiaAbstract:Supported WO x clusters are active and stable catalysts for isomerization, dehydration, and cracking reactions. Bronsted acid sites form on WO x clusters when a lower valent element replaces W6 + or when W6 + centers reduce slightly during catalytic reactions. WO x clusters of intermediate size provide the balance between reducibility and accessibility required to maximize the number of surface H+ species in WO x –ZrO2, zirconium tungstate, and oxygen-modified WC catalysts. H2 is involved in the generation and maintenance of Bronsted acid sites during catalytic reactions on WO x clusters.
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bifunctional reactions of alkanes on Tungsten carbides modified by chemisorbed oxygen
Journal of Catalysis, 1991Co-Authors: Enrique Iglesia, F H Ribeiro, Joseph E Baumgartner, M BoudartAbstract:Abstract Tungsten carbides modified by chemisorbed oxygen catalyze n-heptane isomerization with high selectivity. Kinetic, isotopic tracer, and deuterium-exchange measurements show that the reaction proceeds via sequential n-heptane dehydrogenation and heptene isomerization steps. At low temperatures, isomerization rates are limited by heptene rearrangements but dehydrogenation steps become increasingly rate-limiting as temperature increases. The isomer distribution in n-heptane and 3,3-dimethylpentane reaction products and the 13C distribution in isoheptanes formed from n-heptane-1-13C show that isomerization occurs predominantly by methyl migration steps typical of carbenium-ion rearrangements on acid sites. WOx species on carbide surfaces appear to introduce acid sites similar to those present in supported Tungsten Oxides. n-Heptane dehydrocyclization and hydrogenolysis reactions also require heptene intermediates. Dehydrocyclization occurs predominantly by (1, 6) ring closure while hydrogenolysis leads to random cleavage of carbon-carbon bonds in n-heptane.
Kourosh Kalantarzadeh - One of the best experts on this subject based on the ideXlab platform.
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nanostructured Tungsten oxide properties synthesis and applications
Advanced Functional Materials, 2011Co-Authors: Haidong Zheng, Jian Zhen Ou, Michael S Strano, Richard B Kaner, Arnan Mitchell, Kourosh KalantarzadehAbstract:Metal Oxides are the key ingredients for the development of many advanced functional materials and smart devices. Nanostructuring has emerged as one of the best tools to unlock their full potential. Tungsten Oxides (WOx) are unique materials that have been rigorously studied for their chromism, photocatalysis, and sensing capabilities. However, they exhibit further important properties and functionalities that have received relatively little attention in the past. This Feature Article presents a general review of nanostructured WOx, their properties, methods of synthesis, and a description of how they can be used in unique ways for different applications. Tungsten Oxides (WOx) are unique functional materials that can be obtained in a vast variety of nanostructured forms. This Feature Article presents a comprehensive review on the properties of WOx that goes beyond chromism and photocatalysis, for which they are usually investigated for. This is followed by a survey of their synthesis methods and implementations for different applications.
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synthesis of nanostructured Tungsten oxide thin films a simple controllable inexpensive aqueous sol gel method
Crystal Growth & Design, 2010Co-Authors: Michael Breedon, P Spizzirri, M B Taylor, Johan Du Plessis, D G Mcculloch, Leshu Yu, Zheng Hu, W Wlodarski, Kourosh KalantarzadehAbstract:Among the available metal oxide nanostructures, Tungsten oxide has remained, at times, troublesome to fabricate, with many synthetic methods often requiring exotic equipment and or reagents. In this work, we present a systematic investigation demonstrating a new method for the deposition of anhydrous and hydrated nanostructured Tungsten oxide thin films via spin coating. The attributes of these materials include the following: high surface area, controllable deposition, and compatibility with existing semiconductor fabrication infrastructure making this method a suitable candidate for application in the manufacture of gas sensors and dye sensitized solar cells. We will show that it is possible to form micrometer thick highly crystalline nanostructured thin films and, using Raman, SEM, XRD, XPS, and TEM analysis, will prove that these nanostructures can be rendered into anhydrous or partially or fully hydrated Tungsten Oxides. We further demonstrate the application of these materials in the fabrication of ...
Wolfgang Tremel - One of the best experts on this subject based on the ideXlab platform.
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solvothermal synthesis of molybdenum Tungsten Oxides and their application for photoelectrochemical water splitting
ACS Sustainable Chemistry & Engineering, 2018Co-Authors: Dmitri Spetter, Jan Hilgert, Ibrahim Khan, Ahsan Ul Haq Qurashi, Tobias Weidner, Hao Lu, Muhammad Nawaz Tahir, Wolfgang TremelAbstract:Molybdenum and Tungsten Oxides are of interest as semiconductors for the production of clean and sustainable energy. Here we show that synergistic effects arising from a combination of noncrystallinity and plasmonic resonance in mixed molybdenum/Tungsten Oxides can lead to improved efficiency for the photoelectrochemical (PEC) splitting of water. The quasi-binary Mo/W Oxides were synthesized solvothermally on a gram scale. Size, structure, morphology, and electronic properties of the as-prepared microspheres were characterized by scanning and transmission electron microscopy (SEM, TEM), X-ray diffraction (XRD), Raman, optical absorption (UV–vis), and X-ray photoelectron spectroscopy (XPS). Molybdenum oxide benefits from W-substitution and the concomitant metal reduction. The increased number of charge carriers leads to higher photocurrents for Mo0.5W0.5O2.1 (5.25 mA cm–2), the most reduced phase compared to Mo0.89W0.11O2.7 (1.75 mA cm–2). Long-term photocurrent stability tests (2000 s) under photoillumina...
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solvothermal synthesis of molybdenum Tungsten Oxides and their application for photoelectrochemical water splitting
ACS Sustainable Chemistry & Engineering, 2018Co-Authors: Dmitri Spetter, Jan Hilgert, Ibrahim Khan, Ahsan Ul Haq Qurashi, Tobias Weidner, Muhammad Nawaz Tahir, Wolfgang TremelAbstract:Molybdenum and Tungsten Oxides are of interest as semiconductors for the production of clean and sustainable energy. Here we show that synergistic effects arising from a combination of noncrystalli...
Dmitri Spetter - One of the best experts on this subject based on the ideXlab platform.
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solvothermal synthesis of molybdenum Tungsten Oxides and their application for photoelectrochemical water splitting
ACS Sustainable Chemistry & Engineering, 2018Co-Authors: Dmitri Spetter, Jan Hilgert, Ibrahim Khan, Ahsan Ul Haq Qurashi, Tobias Weidner, Hao Lu, Muhammad Nawaz Tahir, Wolfgang TremelAbstract:Molybdenum and Tungsten Oxides are of interest as semiconductors for the production of clean and sustainable energy. Here we show that synergistic effects arising from a combination of noncrystallinity and plasmonic resonance in mixed molybdenum/Tungsten Oxides can lead to improved efficiency for the photoelectrochemical (PEC) splitting of water. The quasi-binary Mo/W Oxides were synthesized solvothermally on a gram scale. Size, structure, morphology, and electronic properties of the as-prepared microspheres were characterized by scanning and transmission electron microscopy (SEM, TEM), X-ray diffraction (XRD), Raman, optical absorption (UV–vis), and X-ray photoelectron spectroscopy (XPS). Molybdenum oxide benefits from W-substitution and the concomitant metal reduction. The increased number of charge carriers leads to higher photocurrents for Mo0.5W0.5O2.1 (5.25 mA cm–2), the most reduced phase compared to Mo0.89W0.11O2.7 (1.75 mA cm–2). Long-term photocurrent stability tests (2000 s) under photoillumina...
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solvothermal synthesis of molybdenum Tungsten Oxides and their application for photoelectrochemical water splitting
ACS Sustainable Chemistry & Engineering, 2018Co-Authors: Dmitri Spetter, Jan Hilgert, Ibrahim Khan, Ahsan Ul Haq Qurashi, Tobias Weidner, Muhammad Nawaz Tahir, Wolfgang TremelAbstract:Molybdenum and Tungsten Oxides are of interest as semiconductors for the production of clean and sustainable energy. Here we show that synergistic effects arising from a combination of noncrystalli...
