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Control of 1-dimensionally structured tungsten oxide thin films by precursor feed rate modulation in flame vapor deposition
摘要： With the constant tungsten wire feed rate of 4 μm/s, the diameter of nanostructures increases with time and the multi-shell nanostructure and/or branched nanostructure eventually appears and grows. As the diameter and length of 1-D nanostructures increase with time, 1-D nanostructures are easily converted into multi-shell and/or branched nanostructures. The tungsten oxide vapor concentration and flame temperature also affect significantly this conversion of 1-D nanostructures. The increase of tungsten wire feed rate with time accelerated the appearance and growth of multi-shell and/or branched nanostructure, while the decrease of tungsten wire feed rate with time could help prepare the 1-D nanostructured WOX thin film without the growth of multi-shell and/or branched nanostructure. By the modulation of tungsten wire feed rate with time, the thin film thicker than 5μm with single shell nanotube structure could be prepared with almost no increase of nanotube diameter. For the preparation of longer 1-D nanostructured WOX thin film, it is found that the smooth decrease of wire feed rate with time, not the abrupt decrease of feed rate, is required in FVD process to prevent the multi-shell structure growth. We demonstrated that various attractive nanostructures can be prepared quickly by just changing precursor feed rate in FVD process for the first time. The results of this study can provide the basis for many practical applications of FVD process to fast fabrication of several interesting nanostructures.
关键词： nanostructure control,tungsten oxide thin film,precursor feed rate,preparation of 1-D nanostructure,flame vapor deposition
更新于2025-09-23 15:22:29
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Structure and electrochromism of two-dimensional octahedral molecular sieve h’-WO3
摘要： Octahedral molecular sieves (OMS) are built of transition metal-oxygen octahedra that delimit sub-nanoscale cavities. Compared to other microporous solids, OMS exhibit larger versatility in properties, provided by various redox states and magnetic behaviors of transition metals. Hence, OMS offer opportunities in electrochemical energy harnessing devices, including batteries, electrochemical capacitors and electrochromic systems, provided two conditions are met: fast exchange of ions in the micropores and stability upon exchange. Here we unveil a novel OMS hexagonal polymorph of tungsten oxide called h’-WO3, built of (WO6)6 tunnel cavities. h’-WO3 is prepared by a one-step soft chemistry aqueous route leading to the hydrogen bronze h’-H0.07WO3. Gentle heating results in h’-WO3 with framework retention. The material exhibits an unusual combination of 1-dimensional crystal structure and 2-dimensional nanostructure that enhances and fastens proton (de)insertion for stable electrochromic devices. This discovery paves the way to a new family of mixed valence functional materials with tunable behaviors.
关键词： Tungsten oxide,Electrochromism,Octahedral molecular sieves,Proton insertion,Nanostructure
更新于2025-09-23 15:22:29
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Flexible electrochromic tungsten/iron mixed oxide films synthesized by an atmospheric pressure plasma jet
摘要： Flexible electrochromic organo-tungsten- iron oxide (WFexOyCz) films are rapidly deposited onto flexible (60 Ω/□ polyethylene terephthalate/indium tin oxide; PET/ITO) substrates by a low temperature-atmospheric pressure-plasma polymerization method with an atmospheric pressure plasma jet (APPJ) for a short exposed duration of 48 s. The precursor vapors of tungsten hexacarbonyl [W(CO)6] and biscyclopentadienyl iron [ferrocene; Fe(C5H5)2] are mixed with O2 gases at various gas flow rates, injected into air plasma jet and sprayed onto PET/ITO substrates at room temperature (~23oC) and at atmospheric pressure (1.013 × 105 Pa). Flexible electrochromic WFexOyCz films are synthesized with a specific addition of oxygen gases with superior lithium electrochromic properties as demonstrated by a potential sweep alternating between -1 V and 2 V at a scan rate of 40 mV/s in a 1 M LiClO4-propylene carbonate electrolyte. With amorphous WFexOyCz films produced with an APPJ by adding oxygen gases at a specific flow rate of 0.5 sccm, a high value in oxygen deficiency up to 0.189 allows more Li+ ions to intercalate into and deintercalate out of the film. Significant coloration and bleaching are proven by the high values in optical transmittance modulation (ΔT) of up to 70.3%, optical density (ΔOD) up to 0.77 and color efficiency (η) up to 61.3 cm2/C, at a wavelength of 800 nm, respectively.
关键词： Electrochromic materials,Iron oxide,Tungsten oxide,Flexible electrochromic film,Atmospheric pressure plasmas,Plasma polymerization
更新于2025-09-23 15:21:21
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Fabrication of hierarchical sheet-on-sheet WO3/g-C3N4 composites with enhanced photocatalytic activity
摘要： Novel hierarchical sheet-on-sheet WO3/g-C3N4 (WOCN) composites were successfully fabricated by simple calcination method using acid-treated SrWO4/g-C3N4 as precursors. The morphological observation showed that WO3 nanosheets were closely anchored on the surface of g-C3N4 nanosheets to construct a hierarchical nanostructure. The as-synthesized WOCN composites exhibited a significantly higher photocatalytic activity towards the photocatalytic degradation of rhodamine B (RhB) compared to pristine g-C3N4 and WO3 under simulated sunlight irradiation. The optimum photocatalytic activity of the WOCN at a WO3 mass content of 34.6% was 6.5 and 3.0 times higher than that of pristine WO3 and g-C3N4, respectively. The enhanced photocatalytic activities of WOCN composites were attributed to the formation of hierarchical heterostructure, which provided larger specific surface area, better visible-light absorption capability, reduced the recombination of photogenerated electron-hole pairs and enhanced separation efficiency of charge carriers. A Z-scheme photocatalytic mechanism was proposed according to active species trapping experiments.
关键词： Graphitic carbon nitride,Photocatalytic degradation,Tungsten oxide,Hierarchical heterostructure,Strontium tungstate
更新于2025-09-23 15:21:21
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Transparent Electrodes Consisting of a Surface-Treated Buffer Layer Based on Tungsten Oxide for Semitransparent Perovskite Solar Cells and Four-Terminal Tandem Applications
摘要： For semitransparent devices with n-i-p structures, a metal oxide buffer material is commonly used to protect the organic hole transporting layer from damage due to sputtering of the transparent conducting oxide. Here, a surface treatment approach is addressed for tungsten oxide-based transparent electrodes through slight modification of the tungsten oxide surface with niobium oxide. Incorporation of this transparent electrode technique to the protective buffer layer significantly recovers the fill factor from 70.4% to 80.3%, approaching fill factor values of conventional opaque devices, which results in power conversion efficiencies over 18% for the semitransparent perovskite solar cells. Application of this approach to a four-terminal tandem configuration with a silicon bottom cell is demonstrated.
关键词： semitransparent solar cells,perovskite-silicon tandem,niobium oxide,tungsten oxide,perovskite solar cells
更新于2025-09-23 15:21:01
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1D tungsten oxide nanostructures on a Cu(1?1?0) surface
摘要： Thin epitaxial layers of tungsten oxide on metal substrates are suitable as model systems for investigation of chemical reactivity and catalytic properties. However, the ability to prepare epitaxial tungsten oxide model system in situ is quite rare. Here we present a method to prepare highly ordered tungsten oxide thin film on a Cu(1 1 0) single crystal substrate using physical vapor deposition in a reactive atmosphere of atomic oxygen. The oxygen induced reconstruction of the copper substrate gives rise to unique self-organized 1D structures of tungsten oxide parallel with the Cu[1 ?1 0] crystallographic direction. Utilizing a combination of photoemission spectroscopy and density functional theory calculations we reveal emergent physicochemical properties related to the low-dimensionality of the system. Specifically, we observe a support mediated charge redistribution at the interface and a momentum dependent modulation of the valence-band electronic structure. The unusual character of the 1D oxide nanostructures on Cu(1 1 0) surface opens up a unique avenue for preparation of tungsten oxide-based functionalized nanostructures and provides options for further investigation of the fundamental properties of tungsten oxide.
关键词： 1D structures,model system,tungsten oxide
更新于2025-09-23 15:21:01
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Application of Nanostructured Tungsten Fabricated by Helium Plasma Irradiation for Photoinduced Decolorization of Methylene Blue
摘要： The dendritic nanostructure was fabricated on a surface of tungsten plate by helium plasma irradiation. The nanostructure consisting of W metal was partially oxidized to form WO3 on exposure to air, and the resulting surface exhibited a broad photoabsorption in the range from 1 to 5 eV. We examined photoinduced reaction of methylene blue (MB) on the material. It was found that the partially and fully oxidized surface nanostructures were able to promote a decolorization of MB under photoirradiation even with the near-infrared light (< 1:55 eV), whose energy is lower than the band gap of WO3. The reaction rate was varied with the fraction of W and WO3 on the surface layers, that is, the partially oxidized sample promoted the reaction at a higher rate than the fully oxidized one. It is also found that the reaction rate decreased with time, which would be caused by the products accumulation on the surface and the surface oxidation.
关键词： Scanning electron microscopy (SEM),Tungsten oxide,Surface photochemistry,Plasma processing,Nano-wires, quantum wires, and nanotubes,Visible/ultraviolet absorption spectroscopy, X-ray photoelectron spectroscopy
更新于2025-09-23 15:21:01
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Properties, fabrication and applications of plasmonic semiconductor nanocrystals
摘要： In semiconductor nanocrystals (NCs), a new regime has been opened in the plasmonic field since the discovery of localized surface plasmon resonances (LSPRs). LSPRs that lead to near-field enhancement, scattering, and resonant absorption around the NC can be tuned in the range from the visible to the near-infrared (NIR) region across a wide optical spectrum by synthetically varying the doping level, and post synthetically via electrochemical control, photochemical control, and chemical oxidation and reduction. In this review, we will focus on the three widely explored and interrelated examples and their manipulation methods of LSPR of (1) hydrogen molybdenum bronze (HxMoO3?y) NCs, (2) hydrogen tungsten bronze (HxWO3?y) NCs, and (3) oxygen vacancy doped molybdenum tungsten oxide (MoxW1?xO3?y) NCs. Finally, a brief outlook on the applications of these plasmonic NCs is presented.
关键词： hydrogen molybdenum bronze,localized surface plasmon resonances,hydrogen tungsten bronze,plasmonic semiconductor nanocrystals,molybdenum tungsten oxide
更新于2025-09-23 15:19:57
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Ultrathin Plasmonic Tungsten Oxide Quantum Wells with Controllable Free Carrier Densities
摘要： We report the colloidal synthesis of ~3 tungsten-oxygen (W-O) layer thick (~1 nm), two-dimensional (2D) WO3-x nanoplatelets (NPLs) (x ~ 0.55 — 1.03), which display tunable near-infrared localized surface plasmon resonances (LSPR) spectra and high free electron density (Ne) that arises predominantly from their large shape factor. Importantly, the W to O composition ratios inferred from their LSPR measurements show much higher percentage of oxygen vacancies than those determined by X-ray diffraction analysis, suggesting that the aspect ratio of ultrathin WO3-x NPLs is the key to producing an unprecedentedly large Ne, although synthesis temperature is also an independent factor. We find that NPL formation is kinetically controlled, whereas thermodynamic parameter manipulation leads to Ne as high as 4.13 X 1022 cm-3, which is close to that of plasmonic noble metals, and thus our oxide-based nanostructures can be considered as quasi-metallic. The unique structural properties of 2D nanomaterials along with the high Ne of WO3-x NPLs provide an attractive alternative to plasmonic noble metal nanostructures for energy conversions.
关键词： Ultrathin Plasmonic Tungsten Oxide,Quantum Wells,Colloidal Synthesis,Localized Surface Plasmon Resonances,Free Carrier Densities
更新于2025-09-23 15:19:57
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Metal-Reduced WO3a??x Electrodes with Tunable Plasmonic Resonance for Enhanced Photoelectrochemical Water Splitting
摘要： Photoelectrochemical (PEC) water splitting is one of the most promising green technologies for producing renewable clean hydrogen energy. Developing plasmonic semiconductors with tunable plasmonic resonance to visible light has drawn increasing attention in view of utilizing abundant low-energy photons for solar-to-chemical conversion. Herein, we demonstrate for the first time that the WO3 electrode can be partly reduced by various metal foils in acid solution, showing strong localized surface plasmon resonance (LSPR) in the visible-to-near-infrared (Vis–NIR) region. The LSPR can be precisely tuned by using metal foils with different standard electrode potentials for different reaction times, and the LSPR peak position strongly depends on the concentration of W5+ in the WO3?x electrodes. A photocurrent density of 0.79 mA·cm?2 at 1.23 VRHE, which is twice that of pristine one, is obtained over an optimally reduced WO3?x electrode. The enhanced PEC water splitting performance is ascribed to the increased light absorption, conductivity and charge carrier concentration.
关键词： photoelectrochemical water splitting,semiconductor,plasmonic resonance,metal foil,tungsten oxide
更新于2025-09-23 15:19:57