Tungsten Oxide Nanorods Research Articles

Effect of a novel one-dimensional zinc tungsten oxide nanorods anchored two-dimensional graphitic carbon nitride nanosheets for improved solar-light-driven photocatalytic removal of toxic pollutants and photoelectrochemical water splitting

In this study, one-dimensional zinc tungsten oxide (ZnWO4) was prepared by a simple hydrothermal procedure, and two-dimensional graphitic carbon nitride (g-C3N4) was prepared by a solid-state reaction method. The g-C3N4/ZnWO4 (CZO) heterostructure was prepared by a hydrothermal approach. Further, TEM, HRTEM, XRD, DRS, and electrochemical investigations were used to describe the formation of CZO heterostructure. The photocatalytic performance of a CZO nanocomposite shows promising properties for the degradation of tetracycline (TC). Further, the CZO nanocomposite was also used for the photoelectrochemical (PEC) water oxidation. The morphology and structural analysis demonstrated the successful dispersion of ZnWO4 nanorods over the g-C3N4 nanosheets. The tuning of CZO nanocomposite bandgap confirms the establishment of heterostructure. From the photocatalytic investigations, the CZO nanocomposite degrades the antibiotic TC within 70 min under solar-light irradiation. The detailed PEC investigations notify the CZO nanocomposite has lesser charge-transfer resistance, high response of photocurrent with good stability. The CZO electrolyte shows improved photocurrent density of 0.162 mA/cm2 vs. Ag/AgCl in 0.1 M Na2SO3 electrolyte under solar-light illumination. The detailed mechanisms of photocatalytic degradation of TC and PEC water oxidation were discussed with possible graphical diagrams.

Magneli-type tungsten oxide nanorods as catalysts for the selective oxidation of organic sulfides.

Selective oxidation of thioethers is an important reaction to obtain sulfoxides as synthetic intermediates for applications in the chemical industry, medicinal chemistry and biology or the destruction of warfare agents. The reduced Magneli-type tungsten oxide WO3-x possesses a unique oxidase-like activity which facilitates the oxidation of thioethers to the corresponding sulfoxides. More than 90% of the model system methylphenylsulfide could be converted to the sulfoxide with a selectivity of 98% at room temperature within 30 minutes, whereas oxidation to the corresponding sulfone was on a time scale of days. The concentration of the catalyst had a significant impact on the reaction rate. Reasonable catalytic effects were also observed for the selective oxidation of various organic sulfides with different substituents. The WO3-x nanocatalysts could be recycled at least 5 times without decrease in activity. We propose a metal oxide-catalyzed route based on the clean oxidant hydrogen peroxide. Compared to other molecular or enzyme catalysts the WO3-x system is a more robust redox-nanocatalyst, which is not susceptible to decomposition or denaturation under standard conditions. The unique oxidase-like activity of WO3-x can be used for a wide range of applications in synthetic, environmental or medicinal chemistry.

Micro-wheels composed of self-assembled tungsten oxide nanorods supported platinum counter electrode for highly efficient liquid-junction photovoltaic devices

In this study, the synthesis of micro-wheels composed of self-assembled tungsten oxide nanorods supported platinum (WO3/Pt) by atmospheric plasma reduction and its application in a counter electrode (CE) for highly efficient dye-sensitized solar cells were discussed. To characterize the developed materials, we conducted SEM, TEM, EDS-TEM, XRD. Due to a large surface-active area of developed material and its support for Pt nanoparticles in diameters of 2–3 nm, the WO3/Pt electrode indicated as a greater electrochemical catalyst for the redox reaction than Pt and WO3 CEs. Thus, the power conversion efficiency for a device with WO3/Pt electrode is improved to 8.10%, compared to 4.36% for a device with WO3 electrode and 7.61% for a cell with a Pt electrode. This study also supplies a procedure for fabricating highly catalytic and low-price catalyst materials for CEs, which has a tremendous meaning for various applications of micro-wheels consisted of self-assembled WO3 nanorods integrated with platinum.

Enhanced solar-light-driven photocatalytic and photoelectrochemical properties of zinc tungsten oxide nanorods anchored on bismuth tungsten oxide nanoflakes

At present, sustainable water supply and energy generation are the most important challenges faced by humankind globally. Thus, it is crucial to progress ecological techniques for sustainable removal of organic pollutants from wastewater and generation of hydrogen as an alternative to fossil fuels. In this study, zinc tungsten oxide (ZnWO4) nanorods, bismuth tungsten oxide (Bi2WO6) nanoflakes, and Bi2WO6/ZnWO4 (BO–ZO) nanocomposites were prepared via a simple hydrothermal approach. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, diffuse reflectance spectroscopy, and electrochemical analyses were conducted to confirm the formation of the BO–ZO heterostructure. The structural and morphological analyses revealed that the ZnWO4 nanorods were moderately dispersed on the Bi2WO6 nanoflakes. The bandgap tuning of BO–ZO nanocomposite confirmed the establishment of the heterostructure with band bending properties. The BO–ZO nanocomposite could degrade 99.52% of methylene blue (MB) within 60 min upon solar-light illumination. The photoelectrochemical (PEC) measurement results showed that the BO–ZO nanocomposite showed low charge-transfer resistance and high photocurrent response with good stability. The BO–ZO photoanode showed a low charge-transfer resistance of 35.33 Ω and high photocurrent density of 0.1779 mA/cm2 in comparison with Ag/AgCl in a 0.1 M Na2SO3 electrolyte under solar-light illumination. The MB photocatalytic degradation and PEC water oxidation mechanisms of the nanocomposite were investigated.

(Invited) Development of Interfaces for Photoelectrochemical Water Splitting and Electrocatalytic Carbon Dioxide Reduction in Acid Medium

The problem of continuously rising levels of carbon dioxide (CO2), a greenhouse gas released through burning of fossil fuels, in the atmosphere becomes a critical environmental issue and concern over climate change. Consequently, there has been growing recent interest in the development of approaches to effectively sequester, capture, or convert carbon dioxide to useful chemical feedstocks that include syngas (CO + H2), an intermediate for further Fisher-Tropsh processes, carbon-based simple organic fuels, or utility chemicals.Our interest is in the PEM electrolyzers utilizing the proton exchange polymer electrolyte membranes (as separators between anode and cathode compartments) allowing electrolysis at low pH’s and, in principle, capable of yielding higher current densities than alkaline electrolyzers. Nevertheless, under such conditions, the parasitic hydrogen evolution reaction is likely to become predominant and complicate formation of any CO2-reduction products. Our preliminary results with the copper or ruthenium containing tungsten oxide nanorods as catalytic materials are promising with respect to the investigations in acid media.Recent advances (including our studies) in photoelectrochemical water splitting are based on semiconducting photoanodes (typically n-type semiconducting metal oxides) combined either with a metallic cathode (e.g. Pt) or with a p-type semiconductor as a photocathode should be mentioned here in a context of the development of the CO2-electrolyzers exploring photoelectrocatalytic properties and operating under illumination. Among representative examples of metal oxides with n-type semiconducting and promising photoelectrocatalytic properties, tungsten oxide (WO3) should be mentioned. The WO3-based semiconductors are highly stable in acid media, and they are characterized by an energy band gap of 2.5-2.7 eV thus allowing absorption of a reasonable fraction of the solar spectrum up to ca. 500 nm. It comes from our research that, upon illumination, the onset potential for photooxidation of water (in acid medium) is as low as 0.45 V (vs. RHE) what is of practical importance to the energy efficient photoelectrolysis. Further improvement of performance of photoactive metal oxides, e.g. through doping with certain anions or oxo-species will be discussed. Utilization of such systems in the CO2-electrolyzers would require, however, development of practical cathodes (CO2-reduction) operating in acid media that will be addressed during presentation. In our work, the solar energy will be absorbed by a suitable semiconductor to drive water oxidation to oxygen and protons, whereas the reduction of CO2 will be achieved electrochemically with use of a proper (selective) catalyst. By utilizing the aqueous acidic medium, no external hydrogen is required for the CO2-reduction process because the H+ ions not only exist at sufficiently large population but they are generated in situ during the anodic reaction. Coupling of the two processes in a single unit leading to one-step photoelectrochemical/electrocatalytic approach should be possible (e.g. with use of a tandem cell) but, in practice, physical separation of the two reactions in photoanodic (photoelectrochemical water oxidation) and cathodic (carbon dioxide electroreduction) compartments is necessary to increase efficiency and to limit charge recombination. Conversion of CO2 to CO (accompanied by H2-evolution) is an attractive target because syngas (CO + H2) can be utilized for manufacturing of many useful chemicals including synthetic fuels via the Fischer-Tropsch type process.

Effect of hydrogen spillover on the surface of tungsten oxide on hydrogenation of cyclohexene and N-propylcarbazole

The tungsten oxide nanorods loaded with ruthenium nanoparticles (Ru-WO3) nanocomposite were synthesized by hydrothermal method and impregnation method. The properties of Ru-WO3 catalysts were characterized by various methods, such as BET, XRD, SEM, TEM, EDS and XPS. The results show that hydrogen spillover occurs on the surface of WO3 and the catalytic activity of Ru-WO3 in hydrogenation of cyclohexene increases with the increase of reaction time. Subsequently, the Ru-WO3 catalysts was used to hydrogenate N-propylcarbazole (NPCZ). Compare with commercial 0.5 wt% Ru–Al2O3 catalyst, Ru-WO3 can realize the rapid hydrogen uptake of NPCZ at a lower metal loading (0.34 wt%) and lower temperature (150 °C), which is attributed to the increase of reactive sites caused by hydrogen spillover.

A novel sensor based on WO3·0.33H2O nanorods modified electrode for the detection and degradation of herbicide, carbendazim

In the present-day scenario, it is necessary to establish more flexible, effective and selective analytical methods that are easy to operate and less expensive. Cyclic voltammetry (CV) can be a useful technique to assess minute quantity of pollutants and in this work, an effort has been made to detect the trace quantification from the environmental samples. Herein, electrochemical sensor was fabricated using tungsten oxide nanorod (WO3·0.33H2O) for sensitive detection of fungicide, carbendazim (CBZ). Under optimal conditions, while studying the effect of pH on peak current, the highest peak current was observed at pH 4.2. The degradation of CBZ followed the mixed diffusion-adsorption controlled and quasi-reversible processess at the WO3·0.33H2O/GC electrode surface. Using WO3·0.33H2O/GCE sensor in SWV provided the lowest limit of detection (LOD) and limit of quantification (LOQ) values of 2.21 × 10−8 M and 7.37 × 10−8 M, respectively over the concentration ranges of 1.0 × 10−7 M to 2.5 × 10−4 M. The proposed method demonstrates potential applicability of the fabricated sensor for soil and water samples analysis in the management of creating a benign environment.

Au nanoparticle decorated WO3 nanorods with enhanced optical limiting activity

We report a simple route to assembling gold (Au) nanoparticles (NPs) on the surface of one-dimensional tungsten oxide (WO3) nanorods (NRs) through electrostatic interactions. Transmission electron microscope (TEM) imaging, X-ray diffraction (XRD), X-ray photoelectron spectroscopy, ultraviolet-visible (UV-Vis) and diffuse reflectance UV-vis absorption spectroscopy were used to investigate the morphology, structure, surface characteristics, and linear optical properties of the Au NP/WO3 NR heterostructures. TEM images, XRD, and UV/Vis spectroscopy results confirmed the successful decoration of Au NPs on the WO3 NRs. The structure and elemental chemical states of the WO3 NRs were retained during the self-assembly process. The bandgap of the WO3 NRs became wider after attachment of the Au NPs owing to the interaction of the dipole moments of the WO3 NRs and Au NPs under the induction of light. The optical limiting (OL) and nonlinear optical (NLO) properties of the resulting Au NP/WO3 NR heterostructures were studied using an open-aperture Z-scan technique in the nanosecond regime with a 532-nm laser. The introduction of Au NPs strongly influenced the competition of the saturable absorption and nonlinear scattering (NLS) in the WO3 NRs. The Au NP/WO3 NR heterostructure had superior NLO activity to that of un-decorated WO3 NRs. The main factor contributing to the enhanced NLO effect of the Au NP/WO3 NR heterostructures was a combination of free carrier absorption, NLS, and efficient charge/energy transfer at the Au NP/WO3 interface. Our findings show that Au NP/WO3 NR heterostructures are promising candidates for optical limiters to protect sensitive instruments and human eyes from damage caused by high power lasers.

Broad Beam-Induced Fragmentation and Joining of Tungsten Oxide Nanorods: Implications for Nanodevice Fabrication and the Development of Fusion Reactors

In this work, for the first time, fragmentation and joining of tungsten oxide (WO3) nanorods induced by a broad ion beam are reported. Although at low energy (5 keV) and moderate ion fluence, nanorods fragment into smaller pieces along the length, at higher ion energies (50–100 keV), a contrary process occurs, which leads to the joining of the nanorods. A state-of-the-art ion–solid interaction simulation, namely, TRI3DYN, has been invoked to explore the possible mechanisms that reveal subtle contributions of surface defects, ion-beam mixing, and sputtering. High-resolution electron microscopy, photoluminescence study, and X-ray photoelectron spectroscopy support the observed results and proposed mechanisms. Such modifications have interesting effects on the electrical conductivity of the nanorod assembly. The change in sample color upon ion irradiation from initial white to yellow, light blue, deep blue, light green, and cyan shows an excellent and reversible chromatic response of tungsten oxide nanorods to irradiation. Such a property can be exploited to fabricate radiation sensors. The fragmentation and joining at different energy scales have essential implications in nanodevice fabrication through the bottom-up approach as well as for the development of fusion reactors.

(Invited) Hybrid and Functionalized Heterocatalysts for Photoelectrochemical Water Splitting and Electrochemical Carbon Dioxide Reduction

The reduction of carbon dioxide is a very inert process that requires breaking the double C=O bond in the stable CO2 molecule. There is a need for conversion of carbon dioxide, a potent greenhouse gas and a contributor to the global climate change, to useful carbon-based fuels or useful chemicals. Our contribution addresses the low-temperature CO2-conversion processes based on electrocatalytic and photoelectrochemical approaches. In the realistic electrolysis cells, the reduction of CO2 (at cathode or photocathode) would have to be accompanied by water oxidation (at anode or photoanode).Our interest is in the PEM electrolyzers utilizing the proton exchange polymer electrolyte membranes (as separators between anode and cathode compartments) allowing electrolysis at low pH’s and, in principle, capable of yielding higher current densities than alkaline electrolyzers. Nevertheless, under such conditions, the parasitic hydrogen evolution reaction is likely to become predominant and complicate formation of any CO2-reduction products. Our preliminary results with the copper or ruthenium containing tungsten oxide nanorods as catalytic materials are promising with respect to the investigations in acid media.Recent advances (including our studies) in photoelectrochemical water splitting are based on semiconducting photoanodes (typically n-type semiconducting metal oxides) combined either with a metallic cathode (e.g. Pt) or with a p-type semiconductor as a photocathode should be mentioned here in a context of the development of the CO2-electrolyzers exploring photoelectrocatalytic properties and operating under illumination. Among representative examples of metal oxides with n-type semiconducting and promising photoelectrocatalytic properties, tungsten oxide (WO3) should be mentioned. The WO3-based semiconductors are highly stable in acid media, and they are characterized by an energy band gap of 2.5-2.7 eV thus allowing absorption of a reasonable fraction of the solar spectrum up to ca. 500 nm. It comes from our research that, upon illumination, the onset potential for photooxidation of water (in acid medium) is as low as 0.45 V (vs. RHE) what is of practical importance to the energy efficient photoelectrolysis. Further improvement of performance of photoactive metal oxides, e.g. through doping with certain anions or oxo-species will be discussed. Utilization of such systems in the CO2-electrolyzers would require, however, development of practical cathodes (CO2-reduction) operating in acid media that will be addressed during presentation. In our work, the solar energy will be absorbed by a suitable semiconductor to drive water oxidation to oxygen and protons, whereas the reduction of CO2 will be achieved electrochemically with use of a proper (selective) catalyst. By utilizing the aqueous acidic medium, no external hydrogen is required for the CO2-reduction process because the H+ ions not only exist at sufficiently large population but they are generated in situ during the anodic reaction. Coupling of the two processes in a single unit leading to one-step photoelectrochemical/electrocatalytic approach should be possible (e.g. with use of a tandem cell) but, in practice, physical separation of the two reactions in photoanodic (photoelectrochemical water oxidation) and cathodic (carbon dioxide electroreduction) compartments is necessary to increase efficiency and to limit charge recombination. Conversion of CO2 to CO (accompanied by H2-evolution) is an attractive target because syngas (CO + H2) can be utilized for manufacturing of many useful chemicals including synthetic fuels via the Fischer-Tropsch type process.

Functional Blocking Layer of Twisted Tungsten Oxide Nanorod Grown by Electrochemical Anodization for Photoelectrochemical Water Splitting

Using electrochemical anodization of tungsten foil in a fluorinated-based electrolyte, the twisted WO3 nanorods (T-WO3 NRs) were grown, and the film properties were controlled by post-annealing conditions. The anodized WO3 material was composed of two distinct layers; the T-WO3 NRs which functions as an active layer for the PEC reaction and another compact WO3 (C-WO3) barrier which acts as a blocking layer for the charge transport. From more resistance of thicker C-WO3 layer, to minimize the formation of the C-WO3 layer under constant applied voltage, we performed rapid-thermal annealing under air ambient as a post-thermal treatment. As the post-annealing time increased, the thickness of T-WO3 NRs layer remained at approximately 680 nm, but the C-WO3 thickness gradually increased from about 91 nm at 1 min to 633 nm at 120 min. Unexpectedly, the anodic WO3 film having a compact layer thickness of about 475 nm exhibited the highest PEC performance, corresponding to a photocurrent density of 0.75 mA cm−2 at 1.23 V vs reversible hydrogen electrode, subsequently followed by anodic WO3 films with less thick compact layers. This suggests that the C-WO3 layer promotes the charge separation/transfer events by formation of cascading band alignments between the T-WO3 NR and C-WO3 layers.

Enhanced Coloration Efficiency of Electrochromic Tungsten Oxide Nanorods by Site Selective Occupation of Sodium Ions.

Coloration efficiency is an important figure of merit in electrochromic windows. Though it is thought to be an intrinsic material property, we tune optical modulation by effective utilization of ion intercalation sites. Specifically, we enhance the coloration efficiency of m-WO2.72 nanocrystal films by selectively intercalating sodium ions into optically active hexagonal sites. To accurately measure coloration efficiencies, significant degradation during cycling is mitigated by introducing atomic-layer-deposited Al2O3 layers. Galvanostatic spectroscopic measurement shows that the site-selective intercalation of sodium ions in hexagonal tunnels enhances the coloration efficiency compared to a nonselective lithium ion-based electrolyte. Electrochemical rate analysis shows insertion of sodium ions to be capacitive-like, another indication of occupying hexagonal sites. Our results emphasize the importance of different site occupation on spectroelectrochemical properties, which can be used for designing materials and selecting electrolytes for enhanced electrochromic performance. In this context, we suggest sodium ion-based electrolytes hold unrealized potential for tungsten oxide electrochromic applications.

Electrochromic properties of ITO/WO3/LiClO4-PC-PMMA-ACN/NiO/ITO framework

The development of the preparation of tungsten oxide (WO 3 ) nanorods (NRs) using hydrothermal method is still underway. This study demonstrated the growth of WO 3 NRs on indium tin oxide (ITO) coated glass substrates in aqueous solution using single synthesis step hydrothermal synthesis. The surface area and size of the NRs which should be tunable for electrochromic(EC) applications were controlled by adjusting the concentration of surfactants such as propylene glycol (PG). The synthesized WO 3 NRs exhibited fast switching speed and high contrast ratio implying superior EC properties for smart window application. Furthermore, an EC device with the dimensions of 2×4 cm 2 was assembled using the synthesizedWO 3 NRswith the ITO/WO 3 /Lithium perchlorate-propylene carbonate-poly(methyl methacrylate)-acetonitrile/nickel oxide/ITO configuration. The device had an average optical modulation in the visible region, a fast EC response time (1.2s for coloration and 1.5s for decoloration), excellent coloration efficiency (243 cm 2 C ­1 ) anda superior EC stability (over 20000 color/decolor cycles)

High-performance electrochromo-supercapacitors based on the synergetic effect between aqueous Al3+ and ordered hexagonal tungsten oxide nanorod arrays

An electrochromo-supercapacitor, due to the synergetic effect between aqueous Al3+ and ordered hexagonal WO3 nanorod arrays, showed excellent electrochromic–capacitive dual-performance.

High-Throughput Single-Nanoparticle-Level Imaging of Electrochemical Ion Insertion Reactions.

Nanoparticle electrodes are attractive for electrochemical energy storage applications because their nanoscale dimensions decrease ion transport distances and generally increase ion insertion/extraction efficiency. However, nanoparticles vary in size, shape, defect density, and surface composition, which warrants their investigation at the single-nanoparticle level. Here we demonstrate a nondestructive high-throughput electro-optical imaging approach to quantitatively measure electrochemical ion insertion reactions at the single-nanoparticle level. Electro-optical measurements relate the optical density change of a nanoparticle to redox changes of elements in the particle under working electrochemical conditions. We benchmarked this technique by studying Li-ion insertion in hexagonal tungsten oxide (h-WO3) nanorods during chronoamperometry and cyclic voltammetry. Interestingly, the optically detected current response revealed underlying processes that are hidden in the conventional electrochemical current measurements. This imaging technique may be applied to 13 nm particles and a wide range of electrochemical systems such as electrochromic smart windows, batteries, solid oxide fuel cells, and sensors.

Hybrid and Functionalized Interfaces for Photoelectrochemical Water Splitting and Electrocatalytic Carbon Dioxide Reduction

The reduction of carbon dioxide is a very inert process that requires breaking the double C=O bond in the stable CO2 molecule. There is a need for conversion of carbon dioxide, a potent greenhouse gas and a contributor to the global climate change, to useful carbon-based fuels or useful chemicals. Our contribution addresses the low-temperature CO2-conversion processes based on electrocatalytic and photoelectrochemical approaches. In the realistic electrolysis cells, the reduction of CO2 (at cathode or photocathode) would have to be accompanied by water oxidation (at anode or photoanode). Our interest is in the PEM electrolyzers utilizing the proton exchange polymer electrolyte membranes (as separators between anode and cathode compartments) allowing electrolysis at low pH’s and, in principle, capable of yielding higher current densities than alkaline electrolyzers. Nevertheless, under such conditions, the parasitic hydrogen evolution reaction is likely to become predominant and complicate formation of any CO2-reduction products. Our preliminary results with the copper or ruthenium containing tungsten oxide nanorods as catalytic materials are promising with respect to the investigations in acid media. Recent advances (including our studies) in photoelectrochemical water splitting are based on semiconducting photoanodes (typically n-type semiconducting metal oxides) combined either with a metallic cathode (e.g. Pt) or with a p-type semiconductor as a photocathode should be mentioned here in a context of the development of the CO2-electrolyzers exploring photoelectrocatalytic properties and operating under illumination. Among representative examples of metal oxides with n-type semiconducting and promising photoelectrocatalytic properties, tungsten oxide (WO3) should be mentioned. The WO3-based semiconductors are highly stable in acid media, and they are characterized by an energy band gap of 2.5-2.7 eV thus allowing absorption of a reasonable fraction of the solar spectrum up to ca. 500 nm. It comes from our research that, upon illumination, the onset potential for photooxidation of water (in acid medium) is as low as 0.45 V (vs. RHE) what is of practical importance to the energy efficient photoelectrolysis. Further improvement of performance of photoactive metal oxides, e.g. through doping with certain anions or oxo-species will be discussed. Utilization of such systems in the CO2-electrolyzers would require, however, development of practical cathodes (CO2-reduction) operating in acid media that will be addressed during presentation. In our work, the solar energy will be absorbed by a suitable semiconductor to drive water oxidation to oxygen and protons, whereas the reduction of CO2 will be achieved electrochemically with use of a proper (selective) catalyst. By utilizing the aqueous acidic medium, no external hydrogen is required for the CO2-reduction process because the H+ ions not only exist at sufficiently large population but they are generated in situ during the anodic reaction. Coupling of the two processes in a single unit leading to one-step photoelectrochemical/electrocatalytic approach should be possible (e.g. with use of a tandem cell) but, in practice, physical separation of the two reactions in photoanodic (photoelectrochemical water oxidation) and cathodic (carbon dioxide electroreduction) compartments is necessary to increase efficiency and to limit charge recombination. Conversion of CO2 to CO (accompanied by H2-evolution) is an attractive target because syngas (CO + H2) can be utilized for manufacturing of many useful chemicals including synthetic fuels via the Fischer-Tropsch type process.

Facile synthesis of size-controlled Ag supported on WO3 nanorods and their application as novel and active catalyst in oxidant-free dehydrogenation of benzyl alcohols

A new and simple strategy for the size-tunable synthesis of silver supported tungsten oxide nanoparticles (NPs) was reported. Polyethylene glycol (PEG) of molecular weights 400 and 4000 was used as surfactant to tune the size of nanoparticles. These as-synthesized Ag/WO3 nanomaterials were characterized by XRD, FT-IR, TGA, TEM, SEM, EDX, ICP-AES, XPS, and BET analysis. The material synthesized in the presence of PEG 4000 is ~10 nm metallic silver nanoparticles (Ag NPs) supported on tungsten oxide (WO3) nanorods with diameters between 20 and 40 nm. These nanomaterials are very effective catalysts in oxidant-free dehydrogenation of benzyl alcohols.

A novel heterostructure of oriented core/shell tungsten oxide nanorod arrays for electrochromo-pseudocapacitor

Good dual electrochromic-capacitive performances and long life are both important for an electrochromo-pseudocapacitor. In this paper, a novel heterostructure, which is fabricated using well-oriented hexagonal WO3 nanorod arrays as the core and amorphous WO3−x as the shell, has been proved to possess excellent electrochromic and pseudocapacitive properties. The annealing temperatures for coating the shell take great influence on its microstructure, especially the crystallinity, thus on the comprehensive properties of the heterostructure. Results show that the heterostructure reaches the optimal state at 250 °C with short response times (14, 10.5 s) and high specific capacitance (716.8 F·g−1) while maintaining good stability.

Lentinan in-situ coated tungsten oxide nanorods as a nanotherapeutic agent for low power density photothermal cancer therapy

Development of high photothermal performance and biocompatible nanotherapeutic agents is of great importance for photothermal cancer treatment. In this paper, we have developed lentinan decorated tungsten oxide nanorods (W18O49@LTN NRs) via a mild one-step solvothermal route. Owing to the numerous surface hydroxyl groups of polymer chains, the presence of lentinan layer in the surface of W18O49 NRs lead to good biocompatibility. The lentinan layer also affects the crystal structure of W18O49 and improves near-infrared absorption (~1.7 × 109 M−1 cm−1 at 980 nm), which is two orders of higher than previously reported PEGylated W18O49 nanowires. Even under near-infrared (NIR) laser irradiation at a very low power density of 0.4 W/cm2, the temperature of W18O49@LTN NRs aqueous dispersion (125 μg/mL) could increase by 15.1 °C. The photothermal conversion efficiency of W18O49@LTN NRs reaches 33.86%, which is higher than previously reported WO3−x hierarchical nanostructures (28.1%). Importantly, when cancer cells were treated with W18O49@LTN NRs (200 μg/mL) and 980 nm laser (0.4 W/cm2), a significant photo-induced cell killing behavior was observed. This work demonstrates that W18O49@LTN NRs have the potential for precise cancer treatment.

Influence of single-nanoparticle electrochromic dynamics on the durability and speed of smart windows

Nanomaterials have tremendous potential to increase electrochromic smart window efficiency, speed, and durability. However, nanoparticles vary in size, shape, and surface defects, and it is unknown how nanoparticle heterogeneity contributes to particle-dependent electrochromic properties. Here, we use single-nanoparticle-level electro-optical imaging to measure structure-function relationships in electrochromic tungsten oxide nanorods. Single nanorods exhibit a particle-dependent waiting time for tinting (from 100 ms to 10 s) due to Li-ion insertion at optically inactive surface sites. Longer nanorods tint darker than shorter nanorods and exhibit a Li-ion gradient that increases from the nanorod ends to the middle. The particle-dependent ion-insertion kinetics contribute to variable tinting rates and magnitudes across large-area smart windows. Next, we quantified how particle-particle interactions impact tinting dynamics and reversibility as the nanorod building blocks are assembled into a thin film. Interestingly, single particles tint 4 times faster and cycle 20 times more reversibly than thin films made of the same particles. These findings allow us to propose a nanostructured electrode architecture that optimizes optical modulation rates and reversibility across large-area smart windows.