Tungsten Trioxide Nanoparticles Research Articles

Structure and Morphologic Influence of WO3 Nanoparticles on the Electrochromic Performance of Dual‐Phase a‐WO3/WO3 Inkjet Printed Films

The optimization of tungsten trioxide (WO3) nanoparticles produced via hydrothermal synthesis for application in electrochromic (EC) devices is reported. The structure and morphology of the nanoparticles are controlled by changing the acidity of the aqueous solvent added to the sol‐gel precursor (peroxopolytungstic acid) during synthesis. Orthorhombic hydrated WO3 nanorods or monoclinic WO3 nanoslabs are obtained when HCl is added, while synthesis only in aqueous medium results in a mixture of both types of polymorphs. Dual‐phase thin films are processed by inkjet printing deposition of the nanoparticles in flexible polyethylene terephthalate substrate with indium tin oxide coating (ITO PET) followed by the deposition of the precursor solution. When compared with purely amorphous tungsten oxide films, the dual phase ones present higher optical densities and improved capacity, and cyclability stability. The best results, obtained for orthorhombic hydrated nanoparticles (ortho‐WO3·0.33H2O), are due to its high surface area and improved conductivity. Additionally, the ex situ X‐ray diffraction (XRD) lithiation studies show evidence of a higher distortion of the monoclinic when compared with the orthorhombic crystallographic structure, which contribute to the inferior EC performance. These results validate the use of inkjet printing deposition with low processing temperatures for EC dual‐phase thin films containing optimized nanoparticles which are compatible with low‐cost substrates.

Dodecyl ethyl dimethyl ammonium bromide capped WO3nanoparticles: efficient scaffolds for chemical sensing and environmental remediation

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.

Utilization of tungsten trioxide nanoparticles and nickel oxide pillared montmorillonite nanocomposites for the adsorption of the drug dexamethasone from aqueous solutions

The present study was undertaken to expand an impressive adsorbent and to study the adsorption process captivated in the adsorption of the drug dexamethasone from aqueous solution using the WO3 nanoparticles and nickel oxide pillared montmorillonite nanocomposites.

Photocatalytic properties of tungsten trioxide (WO3) nanoparticles for degradation of Lidocaine under visible and sunlight irradiation

Lidocaine (LDC) is a prevalent positional drug of anesthetic and found in aqueous environments as a pollutant due to its widespread use. The indiscriminate use of the chemicals leads to its release into the environment and it is a crucial ecological problem. The removal of pharmaceutical pollutants from industrial effluent is a difficult task. Many biological and physical techniques are being routinely used for removal of these pharmaceutical pollutants. The present study reports on the use of tungsten trioxide (WO3) nanoparticles for the degradation of LDC by making use of the photocatalytic property of NPs. WO3 NPs was synthesized and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), UV–Visible (UV–Vis) spectroscopy and Brunauer–Emmett–Teller (BET) techniques. WO3 NPs showed a maximum photocatalytic effect at pH 6 and it degraded 95.48% and 97.5% of LDC within 1h under visible and sunlight, respectively.

Dissimilar mechanism of executing hole transfer by WO3 and MoO3 nanoparticles in organic solar cells

We investigated the effect of metal oxide nanoparticles (NPs) in poly (3,4 ethylenedioxythiophence):poly (styrene-sulfonate) layer for the light harvestation in poly (3-hexylthiophene):[6,6]-pheny-C61-butyric acid methyl ester organic solar cells. The role of tungsten trioxide nanoparticles (WO3) and molybdenum trioxide nanoparticles (MoO3) in enhancing the efficiency of solar cells was compared. Due to the difference in the energy band structure of the two nanoparticles, the WO3 NPs acted as a hole blocking layer, whereas MoO3 NPs helped in the hole transfer. The solar cell with WO3 NPs at 1.5wt% concentration showed a power conversion efficiency of 4.22% under AM 1.5G illumination and the device blended with 2wt% of MoO3 NPs showed a power conversion efficiency of 4.40%. We measured various electrical properties including, electrochemical impedance spectroscopy and recombination mechanisms using the light intensity dependent current–voltage measurement of organic solar cell.

Characterization and optical properties of spherical WO3 nanoparticles synthesized via the reverse microemulsion process and their photocatalytic behavior

In this study, orthorhombic WO3 (tungsten trioxide) nanoparticles with light absorption properties in the visible region were successfully synthesized via reverse microemulsion at room temperature. The morphology, size, phase composition, structure, and optical properties of these particles were characterized. Through this method, highly crystalline and well-dispersed WO3 nanoparticles with a phase-pure were successfully obtained. The photocatalytic activities of tungsten trioxide nanoparticles were evaluated by the degradation of methylene blue (MB, used as a probe) dye under visible light irradiation, which exhibits a high photocatalytic MB dye degradation activity as compared to bulk WO3 and the commercial P-25 TiO2 powder.

WO3 Modification by Synthesis of Nanocomposites

This study presents the preparation of tungsten trioxide (WO3) nanoparticles by acidic precipitation using sodium tungstate as a precursor. Composite synthesis was selected among various modification methods to investigate catalytic activity improvement. WO3:polyaniline (PANI) nanocomposites with different weight ratios were prepared. The synthesized nanocomposites were characterized by field emission scanning electron microscopy, X-ray diffraction, thermogravimetric analysis–differential thermal analysis, and Fourier transform infrared spectroscopy. Results revealed the successful preparation of WO3: PANI nanocomposites. These nanocomposites exhibit higher thermal stability compared with PANI, indicating a satisfactory interaction between WO3 and PANI. The synthesized nanocomposites are being evaluated for their catalytic activity.

Tungsten trioxide nanostructured electrodes for organic dye sensitised solar cells

Tungsten trioxide (WO 3 ) nanospheres with diameter ranging from 10 nm to 500 nm were synthesised by a facile thermal oxidation process. By resistively heating metallic tungsten in oxygen atmosphere, WO 3 nanoparticles were produced in high yield. Optical, compositional, morphological and structural studies were performed by UV-VIS-NIR spectrophotometry, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies. XPS studies revealed the formation of tungsten trioxide with oxygen deficiency. Analysis of the particle size (diameter) distribution of the as-deposited samples obtained from SEM micrograph exhibited a Gaussian-type distribution centred around 178 nm and characterised by a half width of 98.3 nm. As deduced from XRD analysis, the as-prepared tungsten trioxide (WO 3 ) nanoparticles were polycrystalline in nature and crystallised in the monoclinic phase. Electrophoretic deposition (EPD) was applied in coating the synthesised tungsten oxide nanoparticles onto fluorine doped tin oxide (FTO) coated quartz substrates for the fabrication of dye-sensitised solar cells (DSSC), with henna ( Lawsonia inermis ) as the natural organic dye. Nanoparticle suspension in double distilled water was used in the EPD process with an optimal electric field of 20 Vcm –1 at a current density of 1 mA/cm 2 . DSSCs developed using these films were tested through the measurement of their current density–voltage (J–V) and spectral photocurrent characteristics. A maximum IPCE of about 32% was obtained at around 450 nm.

Large-scale production of tungsten trioxide nanoparticles for electrochromic application

Large-scale, high yield production of tungsten trioxide (WO3) particles was successfully realized by using a facile, high-temperature, catalyst-free, solid evaporation route with ammonium paratungstate tetrahydrate as raw material. The crystalline structure, size, and morphology of the as-synthesized WO3 particles were systematically investigated by combined techniques of X-ray diffraction and electron microscopy, as a function of reaction temperature, deposition temperature, carrier gas flow rate, and size of the quartz tube. With low carrier gas flow rate (1–2 L min−1), the WO3 products collected from different deposition regions were found to exhibit a diversity of forms, such as thick rods, irregular, polyhedral, and octahedral particles, depending on the reaction temperature. At a reaction temperature of 1350 °C, increasing the carrier gas flow rate led to the formation of semi-spherical or quasi-spherical WO3 particles with decreased size and improved size distribution. A reaction temperature of 1350 °C and an Ar flow rate of 6 L min−1 yielded optimized quasi-spherical WO3 nanoparticles with high size uniformity, which have been found to exhibit stable electrochromic performance with high colour contrast and H+ insertion ability. The WO3 nanoparticles that can be effectively produced in high quantity are promising electrochromic candidates for potential applications in large-area smart windows.

Magnetoresistive conductive polymer-tungsten trioxide nanocomposites with ultrahigh sensitivity at low magnetic field

The effect of conductive polymer matrix including polyaniline (PANI) and polypyrrole (PPy) on the magnetoresistance (MR) behaviors in the variable range hopping (VRH) regime has been investigated in the disordered polymer nanocomposites containing tungsten trioxide (WO3) nanoparticles. These nanocomposites have demonstrated ultrahigh MR sensitivity at low magnetic field regime. The observed positive MR has been well explained by the wave-function shrinkage model. The conductive polymer matrix has shown different effects on the MR behaviors of the nanocomposites. The WO3/PANI nanocomposites have a lower localization length (a0) and density of states at the Fermi level (N(EF)), and higher average hopping distance (Rhop) and average hopping energy (W) compared with those of the WO3/PPy nanocomposites.

Electrochemical Response for Spherical and Rod Shaped WO3 Nanoparticles

A rapid and new technique describes synthesis technique of spherical and rod shaped tungsten trioxide (WO3) nanoparticles with similar band gap at visible wavelength. Acid catalyzed exothermic reaction and structure directing reagent follows the formation of two different morphologies and monoclinic WO3 phase. Rod shaped WO3 nanoparticle coated ITO glass electrode exhibits high current density at identical low voltage and scan rate due to its better adherence and coating uniformity in comparison with spherical nanoparticles. WO3-ITO electrode alters to blue tungsten bronze in color at low voltage, and further the color restores after removing the same applied voltage.

Room temperature synthesis of tungsten (VI) tri-oxide nanoparticles with one-pot multi-component reaction in emulsion nanoreactors stabilized by aerosol-OT

Tungsten (VI) tri-oxide (WO3) nanoparticles (NPs) are prepared by emulsion route using dioctyl sulfosuccinate sodium salt (aerosol-OT) supermolecular template at room temperature. This study shows that the aerosol-OT emulsions are suitable for synthesizing WO3 NPs in the absence of any co-surfactant. The field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive X-ray (EDAX) analyses have been used to characterize the surface morphology, size, structure, phase composition, and proof of the formation of the prepared present NPs, respectively. The physicochemical characterizations showed that the phase-pure nano-sized WO3 particles with the aerosol-OT emulsions solution have approximately uniform morphologies with particles mainly in the range of 5–30nm and with a monoclinic phase without any impurities. The proposed method has the advantage of one pot multicomponent preparation of quite monodispersed WO3 NPs.

Synthesis of tungsten trioxide nanoparticles by microwave plasma in liquid and analysis of physical properties

Tungsten trioxide nanoparticles were synthesized from a tungsten wire by plasma generated in water by 2.45GHz microwaves. The effect of synthesis pressure, power and wire diameter on the formation of nanoparticles and the production rate was investigated. The character of the produced nanoparticles was determined by XRD, absorption spectrum, TEM and particle size distribution. The method proposed in this paper allows control of the nanoparticle size and shape and the optical properties through pressure alone without any additives. In one specific experiment, spherical nanoparticles with a peak diameter of 7nm were synthesized from a tungsten wire with a diameter of 1mm by 200W at 20kPa at a high production rate of 4mg/s. Whereas, rhombic cylindrical nanoparticles together with spherical nanoparticles were synthesized with a peak diameter of 13nm at 101kPa. In addition, plasma and bubble behavior was observed by high-speed camera. Use of a plate to control the updraft of the bubbles caused the gap between the plate and the coaxial electrode to remain consistently filled with bubbles, and plasma generation continued without pause.

High energy-resolution electron energy-loss spectroscopy study on the near-infrared scattering mechanism of Cs0.33WO3 crystals and nanoparticles

The optical and dielectric properties of cesium-doped hexagonal tungsten trioxide (Cs0.33WO3) bulk crystal and nanoparticles, which are employed in solar heat-shielding filter, were investigated by high energy-resolution electron energy-loss spectroscopy (HR-EELS). The EELS spectrum of a Cs0.33WO3 crystal showed a prominent peak at 1.2 eV and a subpeak at 1.7 eV. On the basis of the dielectric function derived from the EELS spectrum, the peaks at 1.2 eV and 1.7 eV were assigned to the volume plasmon excitation of the carrier electrons and electronic excitation, respectively. The EELS spectra of the edge region of individual Cs0.33WO3 nanoparticles exhibited a surface dipole plasmon peak at 0.88 eV and a shoulder structure at 1.4 eV, which corresponded with the optical scattering spectrum. Therefore, it was confirmed that the optical scattering of the filter in the near-infrared region resulted from a surface dipole mode of the plasmon oscillation of the nanoparticles. The peak energies in the experimental spectra of the nanoparticle could not be reproduced by the derived dielectric function of the Cs0.33WO3 crystal. On the basis of the EELS and annular dark-field scanning transmission electron microscopy observations, this inconsistent result was attributed to Cs atom deficiency in the surface region of the nanoparticles.

Inverted structure organic photovoltaic devices employing a low temperature solution processed WO3 anode buffer layer

Solution processing is a convenient method and also the guarantee for low cost and large-scale organic photovoltaic (OPV) production. It was recently suggested that the absorption of OPV devices can be spectrally extended by introducing ternary semiconductor blends, where a second donor with a complementary absorption spectrum is added into the active layer. In this manuscript we demonstrate the successful replacement of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) by low temperature solution processed tungsten trioxide (WO3) nanoparticles for inverted OPV devices based on either poly(3-hexylthiophene) (P3HT): phenyl-C61-butyric acid methyl ester (PCBM) or P3HT: poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-diyl]] (Si-PCPDTBT):PCBM active layers. These WO3 nanoparticles can serve as fully functional anode buffer layers in inverted OPV devices without further treatment, while showing comparable functionality as PEDOT:PSS layers.

Effect of WO3 Nanoparticles on Congo Red and Rhodamine B Photo Degradation

Tungsten trioxide nanoparticles with two different sizes (average particle sizes about 50 and 80 nm) were prepared by the spray pyrolysis method. Photo degradation of Congo Red (azo dye) showed that photo catalytic property of the as-prepared WO3 nanoparticles with average size about 80 nm is higher than the sample with average size about 50 nm. Photo degradation of Rhodamine B (cationic triarylmethane dye) showed that photo catalytic property of the as-prepared WO3 nanoparticles with average size about 50 nm is higher than the sample with average size about 80 nm. The samples were characterized with X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), EDX analysis and UV-visible spectrum. Different interactions between dyes and the photo catalyst surface, probably causes the inverse behavior of WO3 nanoparticles with two different sizes in Congo Red and Rhodamine B photo degradation reactions.

Preparation of Different WO3 Nanostructures and Comparison of Their Ability for Congo Red Photo Degradation

Tungsten trioxide nanoparticles with monoclinic structure and average particle size about 80 nm were prepared by the spray pyrolysis method. WO3 nanorods with hexagonal structure and average dimension about 15 × 100 nm were synthesized in gram quantities by modified hydrothermal method at lower temperature and shorter reaction time in comparison to the previous research. Photo degradation of Congo Red showed that the as-prepared WO3 nanoparticles is more effective than nanorod structure. WO3 nanorods actually had no effect in Congo Red photo degradation. Therefore in this reaction, spherical morphology is superior to column morphology. The samples were characterized with X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), EDX analysis, UV-visible spectrum and Transmission Electron Microscopy (TEM).

Interaction of guided light in rib polymer waveguides with dielectrophoretically controlled nanoparticles

This work demonstrates an optofluidic system, where dielectrophoretically controlled suspended nanoparticles are used to manipulate the properties of an optical waveguide. This optofluidic device is composed of a multimode polymeric rib waveguide and a microfluidic channel as its upper cladding. This channel integrates dielectrophoretic (DEP) microelectrodes and is infiltrated with suspended silica and tungsten trioxide nanoparticles. By applying electrical signals with various intensities and frequencies to the DEP microelectrodes, the nanoparticles can be concentrated close to the waveguide surface significantly altering the optical properties in this region. Depending on the particle refractive indices, concentrations, positions and dimensions, the light remains confined or is scattered into the surrounding media in the microfluidic channel.

Tungsten trioxide (WO 3 − x) nanoparticles prepared by pulsed laser ablation in water

Tungsten trioxide (WO 2.9) nanoparticles were prepared, to our knowledge for the first time, by pulsed laser ablation in distilled water. The experiments were performed irradiating a tungsten target with a second harmonic (532 nm) Nd:YAG laser beam varying the operative fluence between 1 and 7 J cm −2 and the ablation time up to 120 min. As evidenced by means of transmission electron microscopy (TEM), at all investigated fluences, small nanostructures of 2–6 nm were accompanied by larger particles with a diameter of about 10–20 nm and aggregates of about 80–100 nm. A plasma shielding effect was evidenced upon increasing the laser fluence, while if the ablation time is increased the amount of particles increases as well, supporting the scalability of the production technique. The deposited nanoparticles stoichiometry has been verified by X-ray photoelectron spectroscopy (XPS), while the optical bandgap values were determined by UV–vis optical absorption measurements.

Deposition of WO 3 doped amorphous hydrogenated carbon film by using liquid phase electrodeposition technique and its mechanical properties

Tungsten trioxide nanoparticles doped amorphous hydrogenated carbon (WO 3/a-C:H) films were successfully fabricated on silicon substrates by electrochemical deposition technique under atmospheric pressure. The as-deposited films were characterized by X-ray photoelectron spectroscopy, Transmission electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy, respectively. Results showed that nanocrystalline tungsten trioxide particles with a grain size in the range of 8–12 nm were homogeneously embedded in the amorphous carbon matrix, and the sp 3-hybridized carbon content in the a-C:H films increased. Compared with pure amorphous carbon film, the hardness and elastic recovery were significantly improved due to the doping of WO 3. At the end, an understandable model was proposed to interpret the growth mechanism of the WO 3/a-C:H composite films.