Highly efficient photocatalytic degradation of methylene blue using carbonaceous WO<Subscript>3</Subscript>/TiO<Subscript>2</Subscript> composites

Recent improvements in the performance of photocatalysts made it possible to tackle pollution through environment friendly methods. This study investigates the modification of the photocatalytic activity of TiO₂ by employing WO₃ and conductive polymers, namely, polyaniline (Pani) and polypyrrole (Ppy). Basing on our previous improvement of TiO₂ using a conductive polymer and activated carbon (AC), this study determines the activated carbon forms of TiO₂. The prepared composites are characterized using X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared, thermogravimetric analysis, Brunauer–Emmet–Teller, and UV–Vis spectroscopy. The specific surface area of the mesoporous composites is as follows: WO₃/TiO₂·AC (Pani) > WO₃/TiO₂·AC (Ppy) > WO₃/TiO₂·Pani > WO₃/TiO₂·Ppy (127 > 98 > 68 > 44 m² g^?1), which exhibited a similar trend to the photocatalytic performances (100 > 95 > 91 > 72 % conversion rate). This result could be attributed to higher porosity, surge of charge separation, and photo-responding range extension induced by the synergistic effect of WO₃, conducting polymers, and TiO₂ in the samples.     

Nanocasting Synthesis of Ultrafine WO<Subscript>3</Subscript> Nanoparticles for Gas Sensing Applications

Ultrafine WO₃ nanoparticles were synthesized by nanocasting route, using mesoporous SiO₂ as a template. BET measurements showed a specific surface area of 700 m²/gr for synthesized SiO_2, while after impregnation and template removal, this area was reduced to 43 m²/gr for WO3 nanoparticles. HRTEM results showed single crystalline nanoparticles with average particle size of about 5 nm possessing a monoclinic structure, which is the favorite crystal structure for gas sensing applications. Gas sensor was fabricated by deposition of WO₃ nanoparticles between electrodes via low frequency AC electrophoretic deposition. Gas sensing measurements showed that this material has a high sensitivity to very low concentrations of NO₂ at 250°C and 300°C.     

The Structural,Optical and Electrical Properties of Spin Coated WO<Subscript><Emphasis Type="Bold">3</Emphasis></Subscript> Thin Films Using Organic Acids

Tungsten trioxide (WO₃) thin films were prepared incorporating various organic acid additives by the sol-gel spin coating technique. They were characterized by X-ray diffraction (XRD), UV-Visible analysis, scanning electron microscopy (SEM) and dc electrical conductivity. From XRD, the crystal phase, average grain size and structural parameters of WO₃ thin films were found to vary owing to different water dissolved organic acid additives. The variation of optical conductivity and band gap energy was calculated from the UV-Visible analysis. The SEM studies revealed that the organic acids influenced the surface morphology of the microsized plates of tungsten oxides. The electrical conductivity at various temperatures correlated with the average grain size of the nanocrystallites of WO₃ thin films.     

A novel approach for solution combustion synthesis of tungsten oxide nanoparticles for photocatalytic and electrochromic applications

Tungsten oxide (WO₃) and tungsten oxide hydrate (WO₃.H₂O) nanoparticles were synthesized via a novel solution combustion synthesis (SCS) method. Various organic fuels (i.e. oxalic acid, glycine, and citric acid) and heat sources were used to obtain different morphologies of nanoparticles. Combustion thermodynamic relations were explained based on propellant chemistry. Adiabatic temperature (T_ad) and specific impulse (I_sp) were also obtained. The synthesized nanoparticles were investigated by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and UV–Visible spectrophotometer. XRD patterns indicated that the structures were transformed from orthorhombic and amorphous structures to monoclinic and tetragonal ones, respectively, upon combustion on the hot plate. Fourier-transform infrared (FTIR) spectra provided evidence of WO₆ octahedral. SEM images showed different microstructures from sponge or rock-like to fine spherical particles with up to 100 nm size. The obtained band gap of all samples was higher than 2.6 eV which is the band gap of bulk tungsten oxide. The synthesized WO₃ nanoparticles showed over 50% photocatalytic efficiency for the degradation of azo dye. The results exhibited that the nanoparticles can be used to make the electroactive layer for electrochromic applications.     

Studies on the Structural,Morphological, Optical,Electro Chemical and Antimicrobial Activity of Bare,Cu and Ag @ WO<Subscript>3</Subscript> Nanoplates by Hydrothermal Method

Hydrothermal synthesis eases the lopsided growth of monoclinic bare, Cu and Ag @ WO₃ nanoplates that exhibit good physic-chemical, optical and electro chemical properties. The powder X-ray diffraction patterns reveals that the synthesized samples WO₃ samples are in monoclinic structure. The 2 mol% of Cu and Ag dopants were increases the crystallinity and the predominant peaks are shifted to higher glancing angles. The variations observed in lattice parameter values indicate the incorporation of dopants in the WO₃ crystal lattice. The FESEM and HRTEM images revealed nanoplate morphology with the particle size range 100–200 nm of diameter and 200–300 nm of thickness. The prominent absorption peak of bare, Cu and Ag @ WO₃ nanoplates were observed in visible region at 332, 326 and 323 nm respectively. The strong continuous from luminescence emission peaks were observed in blue to yellow region with optimal intensity. The electro chemical property was studied using cyclic voltammetry which reveals quick electron transfer accessed in Cu and Ag doped materials. The antimicrobial activity of synthesized bare, Cu and Ag @ WO₃ was investigated on the gram positive, gram negative and fungus strains and observed efficiency of inhibition is exclusively explained.     

Synthesis of nickel catalysts supported on Zr-doped ordered mesoporous Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and their catalytic performance for low-temperature CO<Subscript>2</Subscript> reforming of CH<Subscript>4</Subscript>

A series of Zr-doped ordered mesoporous Al₂O₃ with various Zr contents were synthesized by evaporation-induced self-assembly strategy and the Ni-based catalysts supported on these Al₂O₃ materials were prepared by impregnation method. These catalysts with large specific surface area, big pore volume, uniform pore size possess excellent catalytic performance for the low-temperature carbon dioxide reforming of methane. The activities of these catalysts were tested in carbon dioxide reforming of methane reaction with temperature increasing from 500 to 650?°C and the stabilities of these catalysts were evaluated for long time reaction at 650?°C. It was found that when Zr/(Zr?+?Al) molar ratio?=?0.5%, the Ni/0.5ZrO₂–Al₂O₃ catalyst showed the highest activity, and exhibited superior stabilization compared to the Ni-based catalyst supported on traditional ordered mesoporous Al₂O₃. The “confinement effect” from mesoporous channels of alumina matrix is helpful to stabilize the Ni nanoparticles. As a promoter, Zr could stabilize the ordered mesoporous framework by reacting with Al₂O₃ to form ZrO₂–Al₂O₃ solid solution. Since ZrO₂ enhances the dissociation of carbon dioxide, more oxygen intermediates are given to remove the carbon formed during the reaction.     

Preparing and studying Pt/WO<Subscript>3</Subscript>/ZrO<Subscript>2</Subscript> catalysts for the isomerization of <Emphasis Type="Italic">n</Emphasis>-heptane

The effect of the temperature of WO₃/ZrO₂ support calcination in the range of 700–1000°C on the phase composition, acid, and catalytic properties of Pt/WO₃/ZrO₂ catalysts is studied. Using ammonia TPD, it is found that calcination in the temperature range of 850–950°C results in the formation of strong acid sites that increase the yield of the target products of the reaction of n-heptane isomerization: high octane di- and trimethylsubstituted isomers. DRIFT is used to determine the role of catalyst calcination in an air flow plays in the formation of charged platinum atoms, which results in higher catalyst activity.     

Synthesis of polyaniline/mesoporous carbon nanocomposites and their application for CO<Subscript>2</Subscript> sorption

Ordered mesoporous carbons (OMC), were synthesized by nanocasting using ordered mesoporous silica as hard templates. Ordered mesoporous carbons CMK-1 and CMK-3 were prepared from MCM-48 and SBA-15 materials with pore diameters of 3.4 nm and 4.2 nm, respectively. Mesoporous carbons can be effectively modified for CO₂ adsorption with amine functional groups due to their high affinity for CO₂. Polyaniline (PANI)/mesoporous carbon nanocomposites were synthesized from in-situ polymerization by dissolving OMC in aniline monomer. The polymerization of aniline molecules inside the mesochannels of mesoporous carbons has been performed by ammonium persulfate. The nanocomposition, morphology, and structure of the nanocomposite were investigated by nitrogen adsorption-desorption isotherms, Fourier Transform Infrared (FT–IR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and thermo gravimetric analysis (TGA). CO₂ uptake capacity of the mesoporous carbon materials was obtained by a gravimetric adsorption apparatus for the pressure range from 1 to 5 bar and in the temperature range of 298 to 348 K. CMK-3/PANI exhibited higher CO₂ capture capacity than CMK-1/PANI owing to its larger pore size that accommodates more amine groups inside the pore structure, and the mesoporosity also can facilitate dispersion of PANI molecules inside the pore channels. Moreover, the mechanism of CO₂ adsorption involving amine groups is investigated. The results show that at elevated temperature, PANI/mesoporous carbon nanocomposites have a negligible CO₂ adsorption capacity due to weak chemical interactions with the carbon nanocomposite surface.     

Effect of carbon doping on WO3/TiO2 coupled oxide and its photocatalytic activity on diclofenac degradation

The improved photocatalyst carbon-doped WO₃/TiO₂ mixed oxide was synthesized in this study using the sol–gel method. The catalyst was thoroughly characterized by X-ray diffraction (XRD), diffuse reflectance UV–vis spectroscopy, N₂ adsorption desorption analysis, scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM/EDX), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The photocatalytic efficiency of the prepared materials was evaluated with respect to the degradation of sodium diclofenac (DCF) in a batch reactor irradiated under simulated solar light. The progress of the degradation process of the drug was evaluated by high-performance liquid chromatography (HPLC), whereas mineralization was monitored by total organic carbon analysis (TOC) and ion chromatography (IC). The results of the photocatalytic evaluation indicated that the modified catalyst with tungsten and carbon (TWC) exhibited higher photocatalytic activity than TiO₂ (T) and WO₃/TiO₂ (TW) in the degradation and mineralization of diclofenac (TWC>TW>T). Complete degradation of diclofenac occurred at 250 kJ m⁻² of accumulated energy, whereas 82.4% mineralization at 400 kJ m⁻² was achieved using the photocatalytic system WO₃/TiO₂-C. The improvement in the photocatalytic activity was attributed to the synergistic effect between carbon and WO₃ incorporated into the TiO₂ structure.     

The Influence of the Temperature on the Optical Absorption Properties and Morphologies of WO<Subscript>3</Subscript> Nanorods Synthesized by the Hydrothermal Method

Crystalline WO₃ nanorods of less than 100 nm in diameter have been successfully synthesized at 240 °C for 48 h at pH 1.5 by the hydrothermal method with sodium tungstate as a tungsten source and potassium sulphate as a subsidiary salt. The morphologies and structures of WO₃ rods were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and selected-area electron diffraction (SAED). SEM analysis confirms that the slenderness ratio of the WO₃ rods is enlarged with the increase of the reaction temperature at pH 1.5. SAED analysis shows that the synthesized WO₃ nanorods are crystalline. Ultraviolet–visible (UV-VIS) absorption spectroscopy shows that absorbent power of UV light for WO₃ nanorods enhances with an increase of the slenderness ratio.     

Xanthate sensing properties of Pt-functionalized WO3 microspheres synthesized by one-pot hydrothermal method

WO₃ microspheres in a hierarchical nanorod-assembled architecture were prepared by using a facile one-pot hydrothermal method. The morphology and structure of pure, and 1, 3, and 5 mol% Pt-functionalized WO₃ microspheres were characterized by means of SEM, TEM, XRD, XPS and FTIR measurements. Structural characterizations demonstrated that these WO₃ microspheres assembled by numerous one-dimensional WO₃ nanorods were approximately 2–5 µm in diameter. The nanorods with their diameters in the range of 70–90 nm showed a single crystal hexagonal structure. Gas sensors based on pure and Pt-functionalized WO₃ microspheres showed reversible response and outstanding selectivity to xanthate gas at the operating temperature range of 75–175 °C. The sensor response increased with the increase of xanthate gas concentration. The highest response of 102.7 was obtained for the sensor based on 3 mol% Pt-functionalized WO₃ microspheres to 100 ppm xanthate gas at an operating temperature of 100 °C, which could be ascribed to the large effective surface area and high porosity of WO₃ microspheres as well as the catalytic effect of Pt nanoparticles.     

Effect of Laser Fluence on the Structural,Morphological and Optical Properties of 2H-PbI<Subscript>2</Subscript> Nanoparticles Prepared by Laser Ablation in Ethanol

The effect of laser fluence on the optical, structural and morphological properties of PbI₂ nanoparticles NPs synthesized by pulsed laser ablation in ethanol was studied. The direct optical energy gap of PbI₂ NPs prepared at various laser fluences was in the range of (3–3.3 eV) at room temperature. Three absorption peaks related to surface plasmon resonance at 337, 435 and 507 nm are observed. XRD results show that all the grown PbI₂ NPs are polycrystalline in nature and the formation of hexagonal structure 2H-polytype was observed at laser fluence of 3.6 J/cm². The surface morphology of PbI₂ NPs investigated by SEM revealed formation of hexagonal, platelet-like and spherical NPs morphologies. TEM images showed formation of spherical particles with size varied from 10 to 75 nm depending on the laser fluence. PL measurement shows emission of broad peak centered at 350 nm and increasing the laser fluence results in red shift. The Raman spectra of PbI₂ NPs revealed existence of five vibration modes situated at 74, 96,106, 169 and 213 per cm. FT-IR investigation showed a broad band at 3383 per cm indexed to symmetric stretching vibration of Pb–I clusters and band at 725 per cm related to bending mode of O–H.     

BiVO4 nanoparticle-modified WO3 nanosheet arrays via a stepwise spin-coating process for improved photoelectrochemical performance

A photoelectrode of WO₃ nanosheet@BiVO₄ nanoparticle heterostructured arrays (WO₃@BiVO₄ HAs) on a transparent F-doped SnO₂ glass substrate was designed and manufactured using a hydrothermal and subsequent stepwise spin-coating process. The size and the distribution of BiVO₄ nanoparticles on the surface of WO₃ NSs can be regulated by the number of the stepwise spin-coating cycles. SEM, UV–vis, TEM, and XPS were used to characterize the obtained samples. The PEC performance can be optimized by controlling the number of the stepwise spin-coating cycles. The results of the photoelectrochemical (PEC) measurements display that the WO₃@BiVO₄ HA photoelectrodes obtained at 8 cycles showed a higher photocurrent density (about 3.5 times higher than that of the bare WO₃ nanosheet array (NSA) photoelectrodes), lower charge transfer resistance (from 4019 to 904 Ω cm²), improved electron-hole pair life (from 1 to 50.36 ms), and higher monochromatic photon-to-electron conversion efficiency (from 9 to 38.8%). The remarkable enhancement of the PEC performance may be due to the enhanced light capture, the large contact area with the electrolyte, and the improvement of charge transfer and separation by synergizing the band structure, morphology of photoelectrode, and the reasonable modification of BiVO₄ nanoparticles using a stepwise spin-coating process.     

Infrared Signature of Novel Super-Thermite (Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>/Mg) Fluorocarbon Nanocomposite for Effective Countermeasures of Infrared Seekers

Infrared (IR) guided missiles are real threat; they caused 90% of aircraft damage. Fluorocarbon polymer nanocomposite based on super-thermites can offer superior thermal signature to countermeasure IR guided missile seekers. This study reports on the sustainable fabrication of mono-dispersed colloidal Fe₂O₃ nanoparticles with 3 nm average particle size. Fe₂O₃ nanoparticles were dispersed in acetone for subsequent integration in fluorocarbon polymer. The impact of Fe₂O₃ content on thermal signature was evaluated using (FT-MIR 2–6 μm) spectrophotometer. Nanocomposite polymer with 8 wt% Fe₂O₃ offered an increase in the average intensity of α (2–3 μm) and β (4–5 μm) bands by 50 and 85% respectively to that of reference formulation. Quantification of stimulated emitting species in the combustion flame was conducted using ICT thermodynamic code. The developed nanothermite particles extended the primary reaction zone by 183%. Full discussions about combustion zones with associated exothermic chemical reactions have been represented.     

Controllable Synthesis of NiSe<Subscript>2</Subscript> Nanostructures via Hydrothermal Process for Photocatalytic and Solar Cell Applications

This paper reports on the synthesis of rice-like NiSe₂ nanoparticles via a simple hydrothermal method by employing [bis(2-hydoxyacetophenato)nickle(II)], [Ni(HAP)₂], as a novel nickel precursor. Effect of nickel source on morphology and size of nanostructures was also investigated. Moreover, the as-synthesized NiSe₂ nanostructures were utilized as the photocatalyst for the degradation of methylene blue (MB) and as the counter electrode in dye-sensitized solar cells. The results showed that structures size and morphology have salient effect on solar cells and using rice-like NiSe₂ nanoparticles leads to an increase in DSSCs efficiency compared to agglomerated sphere-like particles from 6.04 to 8.99?% (~49?% improvement).     

Facile Preparation of LaFeO<Subscript>3</Subscript>/rGO Nanocomposites with Enhanced Visible Light Photocatalytic Activity

The present work demonstrates a facile route for preparing LaFeO₃/rGO nanocomposites comprising of metal oxide nanoparticles and graphene. Structural, morphology, optical and photocatalytic studies of the samples were characterized using powder X-ray diffraction (XRD), FT-IR, Raman, high resolution scanning electron microscopy (HRSEM), high resolution transmission electron microscope (HRTEM), atomic force microscopy (AFM), thermogravimetry (TGA), X-ray photoelectron spectroscopy, UV–visible and photocatalytic. LaFeO₃/rGO nanocomposites believed as an effective photocatalyst for the degradation of methyl orange (MO) dye under visible light irradiation. The inclusion of carbon enhances the light absorption of LaFeO₃, resulting in the enhanced photocatalytic activity of the nanocomposite. The degradation of MO dye under visible light source was completely achieved using LaFeO₃/rGO as a catalyst.     

Preparation of hydrophobic SiO<Subscript>2</Subscript>@(TiO<Subscript>2</Subscript>/MoS<Subscript>2</Subscript>) composite film and its self-cleaning properties

TiO₂/MoS₂ composite was encapsulated by hydrophobic SiO₂ nanoparticles using a sol–gel hydrothermal method with methyltriethoxysilane (MTES), titanium tetrachloride (TiCl₄), and molybdenum disulfide (MoS₂) as raw materials. Then, a novel dual functional composite film with hydrophobicity and photocatalytic activity was fabricated on a glass substrates via the combination of polydimethylsiloxane adhesives and hydrophobic SiO₂@(TiO₂/MoS₂) composite particles. The influence of the mole ratios of MTES to TiO₂/MoS₂ (M:T) on the wettability and photocatalytic activity of the composite film was discussed. The surface morphology, chemical compositions, and hydrophobicity of the composite film on the glass substrate were investigated by scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and water contact angle (water CA) measurements. The results indicated that the composite film exhibited stable superhydrophobicity and excellent photocatalytic activity for degradation of methyl orange (MO) even after five continuous cycles of photocatalytic reaction when M/T was 7:1. The water CA and degradation efficiency for MO remained at 154° and 94%, respectively. Further, the composite film showed a good non-sticking characteristic with the water sliding angle (SA) at about 4°. The SiO₂@(TiO₂/MoS₂) composite consisting of hydrophobic SiO₂ nanoparticles and TiO₂/MoS₂ heterostructure could provide synergistic effects for maintaining long-term self-cleaning performance.     

Carbon nanotube hybrids with MoS2 and WS2 synthesized with control of crystal structure and morphology

Carbon nanotube hybrids with molybdenum and tungsten disulfides have attracted lots of attentions due to their unique electronic and photonic properties. MoS₂ and WS₂ with different layers and morphology have been produced from homogeneous ultra-fine MoO₃ and WO₃ nanoparticles (1–2 nm) with different densities on multi-walled carbon nanotubes (MWCNTs) in this work. The different MWCNT hybrid structures not only provide the investigation feasibility of exciton transfer but also give potential applications of catalysts and batteries. A facile method, ultra-sonication, has been adopted to produce MWCNT hybrids with homogeneous ultra-dense and ultra-fine MoO₃ and WO₃ nanoparticles. The as-produced molybdenum trioxide nanoparticles and free-standing molybdenum trioxide nanowires from the same method with different reaction time have been found to crystallize in different crystal lattices. The nanoparticle morphology leads to the detachment of H₂O from molybdenum trioxide lattices, which was confirmed by thermodynamic analysis based on density functional theory. MWCNT hybrids with layered MoS₂ and WS₂ are preferred after the sulfuration of MoO₃ and WO₃ nanoparticle-MWCNT hybrid structures. The layers and morphology of MoS₂ and WS₂ have been controlled by the densities of trioxide nanoparticle precursors on MWCNTs.     

A study on synthesis and properties of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles by solvothermal method

Magnetic nanoparticles (Fe₃O₄) were synthesized by the solvothermal method using FeCl₃ · 6H₂O and ethylene glycol as a reactant. Powder X-ray diffraction, FT-IR, TEM, SEM, and VSM were used to characterize the magnetic particles. The reacting factors, such as reacting time, the concentration of iron source and surfactant, especially the effect of NaAc · 3H₂O, were studied. The results indicated that NaAc · 3H₂O plays the role not only as a dispersant but also a structure-directing agent. The synthesized Fe₃O₄ particles showed excellent magnetic property, which made them have potential for application in magnetic nanodevices and biomedicine.     

The influence of the acidic scouring treatment on the wastewater treatment of TiO<Subscript>2</Subscript> loaded activated carbon electrode

Activated carbon (AC) electrodes were loaded with TiO₂ by using sol–gel method after a pretreatment process, the effect of the acidic pretreatment of the TiO₂ loaded electrode on its deionization efficiency of the wastewater containing NaCl solutions was studied; the physical, chemical and electrochemical properties of the electrode were characterized. The physical and chemical properties of the activated carbon before and after loaded with TiO₂ nanoparticles are characterized by using scanning electron microscopy, energy dispersion spectrum analyzer, Brunauer–Emmett–Teller gas adsorption method, thermal gravimetric analysis, Fourier transform infrared spectroscopy respectively. Electrochemical properties were characterized by employing electrochemical workstation and electrical adsorption deionization test. It was found that both the specific capacitance and the ions removal efficiency of the activated carbon loaded with TiO₂ had an increase of 16.4 and 49.8 % respectively in comparison with original activated carbon electrode. It was believed that this is due to the presence of crystal anatase TiO₂ nanoparticles (the mass content of titanium element in the TiO₂/AC complex is about 24.91 %) on the surface and pores in the activated carbon; while Ti–O–C bonds was found on the surface of the activated carbon, its surface wetting properties was significantly improved. However, it was also noticed that and the specific surface area of the activated carbon was decreased from 680.5 to 523.35 m² g^?1. This might lead to the decrease of the physical adsorption properties of the activated carbon electrodes, but its Electrical double-layer capacitance increases, electrical adsorption efficiency was improved.