Morphology Tailored Synthesis of C-WO<Subscript>3</Subscript> nanostructures and its Photocatalytic Application

Photocatalytic degradation is an ambitious and cost effective technique used for decontamination and sanitization of the waste polluted water of environment. Hydrothermal method is used to synthesis the carbon coupled WO₃ nanoparticles with different concentrations of carbon (0.0, 0.2, 0.5, 1.0 and 2.0%) from precursor Na₂WO₄·2H₂O with glucose and nitric acid. Synthesized nanoparticles were characterized by SEM, EDX, XRD, UV–Vis, and PL to study morphology, and particle size, composition, structural and optical properties, respectively. SEM revealed that morphology of the carbon coupled WO₃ nanoparticles becomes spherical by increasing amount of coupled carbon atoms. The average grain size of the carbon doped nanoparticles is found to be 15–20 nm. Furthermore, size of nanoparticles affect the band gap of synthesized nanoparticles as well. It has also been observed that carbon coupled WO₃ nanoparticles effectively take part in photo degradation due to reduction of electron–hole recombination rate.     

AC susceptibility and Mossbauer study of Ce3+ ion substituted SrFe12O19 nanohexaferrites

Ce³⁺ ion substituted SrFe₁₂O₁₉, SrFe_12-xCe_xO₁₉ (0.0?≤?x?≤?0.5), nanohexaferrites were fabricated by citrate sol-gel combustion approach. X–ray diffractometry (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscope (EDX), EDX Elemental mapping, Fourier transform infrared spectroscopy (FT-IR) were used to study the structure and morphology of the samples. AC magnetic susceptibility and ⁵⁷Fe Mossbauer spectroscopy have been operated to examine the hyperfine structure, static and dynamic magnetic properties. The values of variations in line width, quadrupole splitting, hyperfine magnetic field, and isomer shift have been estimated. The impact of Ce-ion substitution on AC magnetic susceptibility properties of Sr-hexaferrite were explored. The AC-susceptibility measurements reveal the frequency dependence of the magnetic responses, indicating strong magnetic interactions among the nanoparticles of the various products. In addition, it is determined that the magnetic interaction between the nanoparticles is weakened in the substituted products, due to the substitution of Fe³⁺ ions by Ce³⁺ ions.     

Effects of HoMnO3 nanoparticles addition on microstructural,superconducting and dielectric properties of YBa2Cu3O7–δ

(YBa₂Cu₃O_7–δ)_1-x(HoMnO₃)_x (x = 0.0, 0.0025, 0.005, 0.01, 0.03 and 0.05) ceramics were fabricated by introducing co-precipitation synthesized HoMnO₃ (HMO) nanoparticles during solid state reaction process of YBa₂Cu₃O_7–δ (Y-123) superconductors. (Y-123)_1-x(HMO)_x samples were characterized using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) attached with energy Dispersive X-ray spectrometer (EDX), four-point probe measurement, AC susceptometer and impedance analyzer. Majority of XRD patterns were indexed to orthorhombic Y-123 phase. Besides, YBaMn₂O₅ (1.5–3.6%) and YBaMn₂O₆ (2.4–7.4%) phases were detected. FESEM images and EDX analysis showed the presence of agglomerated particulates related to Mn and Ho based phases residing in between the Y-123 grains. The superconducting behavior was significantly enhanced at x = 0.0025 while there was no major depression noticed in critical temperature (T_c-R=0) as the addition increased till x = 0.03 (T_c-R=0 = 88 K). AC susceptibility curves of composites samples manifested sharp transitions for samples with x = 0.0025 and 0.005. Dielectric parameters ε_r′ and ε_r′ʹ decreased as the frequency increased for all samples. The ε_r versus frequency measurements showed increment in ε_r′ and ε_r′ʹ values for all added samples as compared to Y-123 sample. The highest values for ε_r′ and ε_r′ʹ were obtained for sample x = 0.05 with the highest loss at lower frequency. The Nyquist plots of complex impedance were analyzed where two semi-arc circulars represent grain and grain boundary effect were deduced.     

Stability of nanocomposites of poly(ε-caprolactone) with tungsten trioxide

Nanocomposites of poly(ε-caprolactone) (PCL) and tungsten trioxide (WO₃) were prepared by solvent casting using 5 and 10% of WO₃ nanoparticles. The nanocomposites were characterized using several analytical techniques such as XRD, SEM, thermal analysis (TGA and DSC), spectroscopic methods (FTIR and UV/Vis) to gather information on the modifications introduced by WO₃. Photodegradation of PCL/WO₃ nanocomposites was studied exposing the samples to a Xenon lamp, which simulates the UV spectrum of the sun. The results obtained showed that due to the incorporation of WO₃ nanoparticles, the nanocomposites exhibit higher thermal stability together with higher photodegradation efficiency.     

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.     

Efficient and selective oxidation of olefins and alcohols using nanoparticles of WO3-supported manganese oxides (W1−x Mn x O3)

Nanoparticles of manganese oxide supported on tungsten oxide (WO₃) were synthesized by an impregnation method using Mn(NO₃)₂ and Na₂WO₄ as a source of manganese and tungsten. Atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the physicochemical properties of compounds. Due to a highly dispersed state of manganese or insertion of manganese ions into the WO₃ lattice, no manganese oxide peak was observed in the XRD patterns of the W_1?x Mn _x O₃ nanoparticles. Investigation of W_1?x Mn _x O₃ by AAS and EDX showed that the relative atomic abundance of Mn present in the bulk and on the surface of WO₃ was 3.68% and 4.8% respectively. For the first time, the catalytic oxidation of olefins and alcohols, in the presence of these materials and hydrogen peroxide (H₂O₂) as a green oxidant at room temperature was studied. The recoverability and catalyst leaching of the W_1?x Mn _x O₃ nanoparticles in epoxidation of styrene as a model reaction were also investigated.     

Au anchored to (α-Fe2O3)-MCM-41-HS as a novel magnetic nanocatalyst for water-medium and solvent-free alkyne hydration

A novel catalytic system based on Au nanoparticle functionalized magnetic mesoporous silica was prepared as (α-Fe₂O₃)-MCM-41-HS-Au. This material was obtained through the reaction of ordered mesoporous silica-coated magnetic nanoparticles (α-Fe₂O₃)-MCM-41, (3-mercaptopropyl) trimethoxysilane (MPTMS) and HAuCl₄. This catalyst was extensively characterized by various techniques such as SEM, TEM, XRD, EDX, IR and N₂-sorption isotherm. Very uniform dispersion and ordered mesopores of (α-Fe₂O₃)-MCM-41-SH (about 2–3 nm) causes Au nanoparticles to be distributed very finely on the pore surfaces, resulting in a very useful and robust magnetically recyclable catalyst for water-medium and solvent-free alkyne hydration.     

High crystalline tungsten trioxide thin layer obtained by SPD technique

A nanostructured layer of tungsten oxide, WO₃, was prepared by a spray pyrolysis deposition (SPD) method using (NH₄)₂WO₄ precursor. The films were investigated in order to determine the electrical behaviour (impedance, Mott–Schottky and I–V) and the morphological characteristics (SEM). The XRD analysis reveals that tungsten oxide is present in monoclinic phase but the orthorhombic phase is also expected to be present in the structure of WO₃ crystals. Changes in conductivity of the WO₃ films have been observed after immersion in water.     

Synthesis and structural,morphological, compositional,optical and electrical properties of DBSA-doped PPy–WO3 nanocomposites

Synthesis of DBSA-doped PPy–WO₃ (organic–inorganic) nanocomposites, using a novel approach, has been proposed, and further envisaged for their structural, compositional, morphological, optical and electrical properties. DBSA-doped PPy–WO₃ nanocomposites demonstrate superior above mentioned properties than their counterparts i.e. either PPy or WO₃. The XRD spectra of nanocomposites supported to conclude that both i.e. PPy and DBSA have no impact on the crystallinity of WO₃ nanoparticles. The chemical structure of DBSA-doped PPy–WO₃ nanocomposites have been elucidated using FTIR spectra. The morphologies and surface roughnesses of the DBSA-doped PPy–WO₃ nanocomposites were confirmed using scanning electron microscope and atomic force microscope images, respectively. Interconnected type morphology and 13 nm average surface roughness were confirmed for DBSA doped PPy–WO₃ hybrid nanocomposites. The EDX and XPS analyses evidence that, the formation of DBSA doped PPy–WO₃ hybrid nanocomposites without any elemental impurities. The absorption peak of DBSA-doped PPy–WO₃ nanocomposites shift towards the lower wavelength side as compared to the PPy–WO₃ (50%) hybrid nanocomposites. Anionically charged sulfonate group which is supposed to stabilize doped state of the DBSA-PPy–WO₃ nanocomposites, may be responsible for this shift. The dc electrical conductivity of DBSA-doped PPy–WO₃ nanocomposites increases as the content of DBSA is increased from 10 to 50% this could be accounted for by the generation of conduction path through the PPy–WO₃ nanocomposites as DBSA has anionic surfactant nature by preventing an agglomeration of functional material.     

Visible light induced decomposition of organic compounds on WO3 loaded PtPb co-catalysts

Tungsten oxide (WO₃)-supported ordered intermetallic PtPb nanoparticles (PtPb NPs/WO₃) were prepared through a co-reduction of Pt and Pb precursors with sodium borohydride in anhydrous methanol containing WO₃. The PtPb NPs/WO₃ were characterized based on the crystal structure obtained through powder X-ray diffraction (pXRD) as well as X-ray photoemission spectroscopy (XPS) and transmission electron microscopy (TEM). The formation of an ordered PtPb intermetallic phase on the WO₃ surface was confirmed. The PtPb NPs/WO₃ were more efficient when decomposing acetic acid (AcOH) and acetaldehyde (AcH) with visible light irradiation compared to the same process over WO₃ loaded with Pt nanoparticles (Pt NPs/WO₃).     

Laser-Induced Silver Nanoparticles on Titanium Oxide for Photocatalytic Degradation of Methylene Blue

Silver nanoparticles doped on titanium oxide (TiO₂) were produced by laser-liquid interaction of silver nitrate (AgNO₃) in isopropanol. Characteristics of Ag/TiO₂ (Ag doped TiO₂) nanoparticles produced by the methods presented in this article were investigated by XRD, TEM, SEM, EDX, and UV-Vis. From the UV-Vis measurements, the absorption of visible light of the Ag/TiO₂ photocatalysts was improved (additional absorption at longer wavelength in visible light region) obviously. The photocatalytic efficiency of Ag/TiO₂ was tested by the degradation of methylene blue (MB) in aqueous solution. A maximum of 82.3% MB degradation is achieved by 2.0 wt% Ag/TiO₂ photocatalyst under 2 h illumination with a halogen lamp.     

Intergranular properties of polycrystalline YBa2Cu3O7−δ superconductor added with nanoparticles of WO3 and BaTiO3 as artificial pinning centers

Pure (x = 0.0 wt%) superconducting YBa₂Cu₃O_7−δ (YBCO) sample and added YBCO sample with 0.1 wt% artificial barium titanate (BTO) and 0.1 wt% tungsten trioxide (WO₃) nanoparticles were prepared using the solid-state reaction route. Phase purity was analyzed via the X-rays diffraction technique. Scanning electron microscopy showed a high density of isolated W-rich secondary phases embedded within the YBCO added sample. Furthermore, both WO₃ and BTO nanoparticles tend to reside at the grain boundaries and play the role of bridges connecting the YBCO superconducting granules. Quantitative analysis performed on the areas where nanosized entities induced by BTO and WO₃ phases was evidenced by EDX analysis equipped with SEM instrument. The values of H_c2 increased from 1.6 T for pristine to 3.4 T for BTO/WO₃ added samples. The superconducting parameters determined by AC susceptibility measurements also showed an improvement with WO₃ and BTO nanoparticles co-addition. The value of J_cinter(0) increases from 1.18 kA/cm² for the pristine sample to 5.10 kA/cm² for BTO/WO₃ co-added sample. Hence, the incorporation of artificial BTO and WO₃ nanoparticles into the YBCO superconducting phase could be a useful way to make such compounds available in practical applications.     

Preparation of WO3-reduced graphene oxide nanocomposites with enhanced photocatalytic property

In this work, WO₃-reduced graphene oxide (RGO) nanocomposite was synthesized via a simple one-pot hydrothermal method. The synthesized nanocomposite was characterized by SEM, XRD, EDX, UV–vis spectroscopy, N₂ adsorption/desorption, photocurrent response, electrochemical impedance spectroscopy and Raman spectroscopy. The superior contact between WO₃ and RGO sheets in the nanocomposite facilitates the photocatalytic degradation of methylene blue and evolution of oxygen. The cause of the enhanced photocatalytic performance could ascribe to the highly facilitated electron transport by the synergistic effect between WO₃ and RGO sheets, as well as suppressing the electron hole pair recombination in the nanocomposite.     

The impact of the addition of Bi2Te3 nanoparticles on the structural and the magnetic properties of the Bi-2223 high-Tc superconductor

The polycrystalline granular BSCCO high T_c superconductors (HTSC) have limitations in various applications. These limitations appear due to the flux pinning's weakness and the weak links between the grains comparatively in high temperatures and high applied magnetic fields. Bi₂Te₃ nanoparticles are artificially introduced into the Bi-2223 HTCS matrix to be employed as effective flux pinning centers to enhance the flux pinning capability and the critical current density. The effect of the additive of Bi₂Te₃ nanoparticles on the structural and physical properties of Bi-2223 were investigated for the polycrystalline (Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10+δ)_1-x/(Bi₂Te₃)_x where (x = 0.00,0.01,0.02& 0.03). The phase structure/formation, volume fraction, the lattice constants were described by X-ray powder diffraction (XRD) measurements. Diamagnetic signal has been investigated with two onset temperatures (T_c1&T_c2) for the common BSCCO phases (Bi-2223 and Bi-2212) which confirm the XRD obtained data without any indication for unwanted impurities. The magnetic interactions between Bi₂Te₃ nanoparticles addition and the superconductor matrix are discussed at 5 and 50 K. The relation between the microstructure, BSCCO phase's contents, the hysteresis loops, the calculated critical current densities, and the flux densities were also reported for the samples. Nano-Bi₂Te₃ shows a great impact on the BSCCO superconducting properties and influences its flux densities and the flux pinning mechanisms as reported experimentally and theoretically. Consequently, the additive of Bi₂Te₃ nanoparticles must be carefully controlled to balance the microstructure and superconducting parameters of the BSCCO HTSC.     

Synthesis,characterization, and properties of cashew gum graft poly(acrylamide)/magnetite nanocomposites

Graft copolymer nanocomposites based on cashew gum and poly(acrylamide) with different concentrations of nano‐iron‐oxide particles (Fe₃O₄) have been prepared by an in situ polymerization method. The characterization of graft copolymer composite was carried out by FTIR, UV, XRD, SEM, DSC, and TGA, electrical conductivity, and magnetic property [vibrational sample magnetometer (VSM)] measurements. The shift in the spectrum of UV and FTIR peaks shows the intermolecular interaction between metal oxide nanoparticles and the graft copolymer system. The spherically shaped particles observed from the SEM images clearly indicating the uniform dispersion of nanoparticles within the graft copolymer chain. The XRD studies revealed that the amorphous nature of the graft copolymer decreases by the addition of Fe₃O₄ nanoparticles. The glass transition temperature studied from DSC increases with increase in concentration of metal oxide nanoparticles. Thermal stability of composite was higher than the pure graft copolymer and thermal stability increases with increase in content of nanoparticles. Electrical properties such as AC conductivity and dielectric properties of the composites increased with increase in concentration of metal oxide nanoparticles. The magnetic property of graft copolymer nanocomposites shows ferromagnetic and supermagnetism and the saturation of magnetism linearly increased with increasing the Fe₃O₄ content in the polymer composite. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43496.     

Characterization,conductivity studies,dielectric properties,and gas sensing performance of in situ polymerized polyindole/copper alumina nanocomposites

Conducting polymer composites of polyindole (PIN) and copper–alumina (Cu–Al₂O₃) nanocomposites were synthesized by in situ polymerization of indole with different contents of Cu–Al₂O₃ nanoparticles. The polymer nanocomposites were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), transmission electron microscope (TEM), differential scanning calorimetry, thermogravimetric analysis, and ammonia gas sensing performance was also analyzed. FTIR and XRD studies revealed the attachment of Cu–Al₂O₃ in the molecular chain of PIN. The presence of bright trapezoid channels and variation in morphology for different loading of nanoparticles were confirmed by SEM and TEM. The attachment of Cu–Al₂O₃ nanoparticles in the PIN matrix was confirmed through EDX spectroscopy. The glass transition temperature and thermal stability of the composites were greatly enhanced with the loading of Cu–Al₂O₃. Enhancement in alternating current conductivity, dielectric constant and the current–voltage characteristics of the prepared composite revealed the semiconducting nature of the system with an increase in the loading of nanoparticles. Also, nanocomposite exhibited an excellent sensitivity and fast response to ammonia gas. The evaluated result of the present study suggested that Cu–Al₂O₃ reinforced PIN hybrid is a good candidate for the fabrication of electrochemical devices.     

Zirconium substituted spinel nano-ferrite Mg0.2Co0.8Fe2O4 particles and their hybrids with reduced graphene oxide for photocatalytic and other potential applications

Zirconium substituted magnesium cobalt ferrite (Zr_xMg_0.2-xCo_0.8-xFe₂O₄) nanoparticles and their nano-heterostructures with graphene were synthesized by co-precipitation and ultra-sonication route respectively. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopic (SEM) analysis was done to study the effect of Zr⁴⁺ substitution on structural properties, surface morphology, dielectric and current-voltage properties of nanoparticles. The crystallite size of nanoparticles was found in the range of 23–28 nm. XRD pattern analysis confirmed the spinel structure of nanoparticles. Graphene synthesized by modified Hummer's method was utilized as substrate to prepare the heterostructures with ferrite particles. Dispersion of nanoparticles on the surface of rGO sheets was confirmed by SEM analysis. Enhanced photocatalytic activity of nanoparticles and graphene based nano-heterostructures was observed under visible light irradiation. During the current-voltage measurements, decrease in electrical resistivity of nanoparticles was observed. Dielectric measurements were performed within the frequency range 1 MHz–3 GHz. Electrochemical impedance spectroscopy was done to evaluate the kinetic parameters and charge-transfer resistance (R_ct) at electrode interface. Enhanced photocatalytic applications, suggested that Zr_xMg_0.2-xCo_0.8-xFe₂O₄ nanoparticles and graphene based nano-heterostructures can be used for degradation of various organic based pollutants in drinking water.     

New versatile synthesis for low dimension superparamagnetic YBa2Cu3O7−x nanoparticles

This paper describes the synthesis and characterization of YBa₂Cu₃O_7−x (YBCO) nanoparticles obtained through an environmentally friendly chemistry approach. Y-, Cu- acetates and Ba trifluoroacetate were used for the synthesis of the precursor gel. Moreover, sucrose and pectin reagents were added as chelating agents inducing the formation of small size oxide nanoparticles. The thermal decomposition process of the precursor powder was investigated by thermal analysis correlated with mass spectrometry. The chemical nature, structure and morphology of the particles were investigated by X-Ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Fourier Transform Infrared Spectroscopy. According to XRD analysis the nanoparticles have an orthorhombic structure and the average diameter between 18–30 nm, additionally confirmed by TEM measurements. The superparamagnetic behavior at room temperature of the YBCO nanoparticles has been clearly evidenced by magnetization measurements. Furthermore, the effect of the annealing atmosphere on the magnetic properties has been studied.     

Synthesis of flake-like bismuth tungstate (Bi2WO6) for photocatalytic degradation of coomassie brilliant blue (CBB)

Bismuth tungstate (Bi₂WO₆) flake-like nanostructures with zigzag periphery and 30–40 nm thickness in high yield were produced by facile and efficient modified hydrothermal technique. The as-synthesized nanostructures were characterized by X-ray diffraction (XRD), energy dispersive x-ray spectroscopy (EDX), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Bi₂WO₆ nanostructures were investigated as visible light photocatalyst to degrade model dye coomassie brilliant blue (CBB). The role of hydrogen peroxide (H₂O₂) used as initiator was also studied by varying concentrations during photocatalysis. It was observed that photocatalytic activity significantly enhanced for lower initiator concentrations. The growth mechanism for nanostructures was also discussed briefly.