Synthesis of tungsten carbide nanopowder via submerged discharge method

Tungsten carbide nanopowder was prepared via pulsed discharge of bulk tungsten and graphite rods immersed in pure ethanol. The effect of discharge parameters on the characteristics of final products was investigated. Structural and morphological characterization of nanopowder was performed by means of X-ray diffraction analysis and transmission electron microscopy. In order to determine the feasibility of using synthesized material as an electrocatalyst, tungsten carbide nanopowder was tested for hydrogen evolution. A correlation was found between morphology of nanoparticles, their phase composition and electrocatalytic activity.     

The lithiation studies of nanostructured tungsten oxide film prepared via electrochemical precipitation

In this work, nanostructured tungsten oxide was electrodeposited by cyclic voltammetric technique onto a stainless steel surface. The structure and surface morphology of the resulting oxide film were characterized by means of X-ray diffraction, scanning probe microscopy, and scanning electron microscopy. The electrochemical intercalation of lithium into the nanostructured tungsten oxide was studied using cyclic voltammetry, galvanostatic charge–discharge curves, and electrochemical impedance spectroscopy in a liquid electrolyte consisting of 1 M LiClO₄ in propylene carbonate. The as-deposited tungsten oxide indicated the capacity for electrochemical lithium insertion. The specific capacitance of 108.05 F?g^?1 was obtained at the constant discharge density of 0.07 mA?cm^?2.     

Preparation of nanostructured and nanosheets of MoS2 oxide using oxidation method

Molybdenum disulfide (MoS₂), a two-dimensional transition metal has a 2D layered structure and has recently attracted attention due to its novel catalytic properties. In this study, MoS₂ has been successfully intercalated using chemical and physical intercalation techniques, while enhancing its surface properties. The final intercalated MoS₂ is of many interests because of its low-dimensional and potential properties in in-situ catalysis. In this research, we report different methods to intercalate the layers of MoS₂ successfully using acid-treatment, ultrasonication, oxidation and thermal shocking. The other goal of this study is to form SO bonds mainly because of expected enhanced in-situ catalytic operations. The intercalated MoS₂ is further characterized using analyses such as Fourier Transform Infrared Spectroscopy (FTIR), Raman, Contact Angle, X-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-Ray Microanalysis (EDAX), Transmission electron microscopy (TEM), and BET.     

A facile route to synthesize titanium oxide nanowires via water-assisted chemical vapor deposition

Single crystalline rutile titanium oxide nanowires have been synthesized in bulk yield based on commercial metal titanium by a facile water-assisted chemical vapor deposition method. The morphology, crystallinity, and phase structure of the nanowires have been characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and X-ray diffraction (XRD). This growth strategy is applicable for commercial metal titanium substrate with different spatial dimensions, such as powder, network mesh, and flat foil. The as-synthesized nanowires are found to be mainly composed of single crystalline rutile TiO₂ nanowires in spiral shape with a small amount of hexagonal Ti₂O nanowires with zigzag form. A growth mechanism has been proposed to explain the novel spiral and zigzag types of titanium oxide nanowires under moderate temperature (850 °C). This method promises an alternative way for industrialization of titanium oxide nanowires which may serve as a good candidate for various industrial applications such as optoelectronic, electronic, and electrochemical nanodevices.     

Synthesis of hierarchical MoS<Subscript>2</Subscript> microspheres composed of nanosheets assembled via facile hydrothermal method as anode material for lithium-ion batteries

A hierarchical MoS₂ architecture composed of nanosheet-assembled microspheres with an expanded interplanar spacing of the (002) planes was successfully prepared via a simple hydrothermal reaction. Electron microscopy studies revealed formation of the MoS₂ microspheres with an average diameter of 230 nm. It was shown that the hierarchical structure of MoS₂ microspheres possesses both the merits of nanometer-sized building blocks and micrometer-sized assemblies, which offer high surface area for fast kinetics and buffers the volume expansion during lithium insertion/deinsertion, respectively. The micrometer-sized assemblies were found to contribute to the enhanced electrochemical stabilities of the electrode materials. The mentioned advantages of the MoS₂ electrode prepared in this work allowed enhanced cyclability and high rate capability of the material. Along with this, the material delivered a high initial discharge capacity of 1206 mAh g^?1 and a reversible discharge capacity of 653 mAh g^?1 after 100 cycles at a current density of 100 mA g^?1. Furthermore, the material delivered a high reversible capacity of 480 mAh g^?1 at a high current density of 1000 mA g^?1.     

Fabrication of superhydrophobic coating via a facile and versatile method based on nanoparticle aggregates

Herein, we report a facile and low cost method for the fabrication of superhydrophobic surface via spin coating the mixture of polydimethylsiloxane precursor (PDMS) and silicon dioxide (SiO₂) nanoparticles. The surface hydrophobicity can be well tuned by adjusting the weight percent of PDMS and SiO₂. The water contact angle (WCA) can increase from 106.8 ± 1.2° on PDMS film to 165.2 ± 2.3° on PDMS/SiO₂ coating, companying with a change from adhering to rolling which was observed from tilting angle (TA) characterization. Multi-scale physical structures with SiO₂ nanoparticle aggregates and networks of SiO₂ nanoparticle aggregates are characterized by scanning electron microscopy (SEM) and atomic force microscope (AFM), and they can be observed more clearly from the AFM images treated with software (WSxM). Then the relationship between surface hydrophobicity and structures is further discussed based on Wenzel and Cassie models, indicating that the appearance of networks of nanoparticle aggregates is important in the Cassie state. The superhydrophobic coating can keep the superhydrophobicity at least for one month under environment conditions and readily regenerate after mechanical damage. Additionally, the superhydrophobic coating can be fabricated using other methods including dip coating, spray coating and casting. Thus, a large area of superhydrophobic coatings can be easily fabricated. Therefore the range of possible applications for these facile and versatile methods can be expanded to various actual conditions.     

Hierarchical structured tungsten oxide nanocrystals via hydrothermal route: microstructure, formation mechanism and humidity sensing

Hierarchical structured tungsten oxide nanocrystals were synthesized via the hydrothermal route assisted by a capping agent of ammonium benzoate (AB). The products were characterized using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The experimental results show that the crystal microstructures could be changed from flower-shape to star-shape by changing the mole ratio of ammonium benzoate to sodium tungstate (AB/ST). The crystal phases were changed from orthorhombic WO₃?0.33H₂O to hexagonal WO₃ with the increase in the concentration of AB. Based on the results from Fourier transform infrared spectroscopy and time-dependent growth analysis, a self-assembly growth mechanism has been proposed for the formation of flower, spherical, and star-netted microstructures at different mole ratios of the AB/ST. The star-netted WO₃ nanocrystals were applied as a sensitive layer for humidity sensing performed using a Love-mode ZnO/36^° Y-cut LiTaO₃ surface acoustic wave device, and a stable and sensitive response to the change of relative humidity was obtained.     

One-pot synthesis of one-dimensional array Pt nanoparticles on carbon nanotubes via a facile microwave polyol method

High-density attachment and one-dimensional array Pt nanoparticles (NPs) on carbon nanotubes (CNTs) to generate Pt/CNTs heterostructures are obtained via one-pot microwave polyol method. The morphology, composition of as-obtained Pt/CNTs heterostructures is characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD). The Raman spectrum and Fourier transform infrared (FTIR) spectrum show the introduction of defects or functional groups on CNTs surface, which are crucial factors to assist the nucleation and growth of Pt NPs along the skeleton of CNTs.     

A facile method to the cube-like MnSe2 microcrystallines via a hydrothermal process

A convenient hydrothermal process was applied to prepare the cube-like MnSe₂ microcrystallines through the reaction of MnSO₄·H₂O with Se and NaH₂PO₂·H₂O in aqueous solution at 160 °C for 12 h. Powder X-ray diffraction (XRD) analysis confirmed that the product was the cubic phase of MnSe₂ with cell parameter a=6.440 Å. The chemical composition of the MnSe₂ was determined by XPS. The Raman spectrum of MnSe₂ presented the peaks of the Se-Se stretching mode at 232.44 and 266.58 cm⁻¹. The images of scanning electron microscope (SEM) and transmission electron microscope (TEM) showed the cube-like morphology of the product with the edge length ranging from 20 to 30 μm. The formation mechanism of the MnSe₂ microcrystallines was discussed as well.     

A new aluminum iron oxide Schottky photodiode designed via sol–gel coating method

A novel aluminum iron oxide(Al/AlFe2O4/p-Si) Schottky photodiode was successfully fabricated via the sol–gel coating process. The microstructure of the spinel ferrite(AlFe2O4) was examined by atomic force microscopy. The current–voltage characteristics of the fabricated photodiode were studied under dark and different illumination conditions at room temperature. By using the thermionic emission theory, the forward bias I–V characteristics of the photodiode are analyzed to determine the main electrical parameters such as the ideality factor(n) and barrier height(ΦB0) of the photodiode. The values of n and ΦB0 for all conditions are found to be about 7.00 and 0.76 eV, respectively. In addition,the values of series resistance(Rs) are determined using Cheung's method and Ohm's law. The values of Rs and shunt resistance(Rsh) are decreased with the increase of illumination intensity. These new spinel ferrites will open a new avenue to other spinel structure materials for optoelectronic devices in the near future.     

One-pot synthesis of Ag+ doped BiVO4 microspheres with enhanced photocatalytic activity via a facile hydrothermal method

The Ag⁺/BiVO₄ photocatalyst was fabricated through a facile hydrothermal method by using K₆V₁₀O₂₈·9H₂O as the vanadium source. The impact of Ag⁺ on the product's structure and morphology was studied. It was shown that the amount of Ag⁺ has no effect on the product’s crystal phases but plays an important role on the morphology of the nanoparticles that construct the shell of BiVO₄ microspheres. In addition, the Ag⁺-doped photocatalysts have much higher photocatalytic activities in removing RhB and MB under the UV light illumination than the pure BiVO₄. A possible photocatalytic mechanism was proposed in photoexcitation of the BiVO₄ electrons which subsequently captured by the dopant. The present work may offer a novel route to reach higher photocatalytic activity by doping the Ag⁺ in the semiconductor catalysts.     

One-step preparation of hierarchical superparamagnetic iron oxide/graphene composites via hydrothermal method

In this paper, graphene/magnetite composites with hierarchical Fe₃O₄ structures were synthesized via a one-step hydrothermal method. The size of Fe₃O₄ nanocrystals and nanocrystal clusters can easily be controlled by altering reaction time and the starting mixed solvent ratio, respectively. Raman measurements evidenced that graphene oxide was simultaneously reduced to graphene during the deposition of magnetite particles. The deposition of Fe₃O₄ nanocrystals and nanocrystal clusters impedes graphene to restore the graphite structure. The composites showed a high crystallinity of magnetite and a considerable saturation magnetization. Furthermore, the acrylate modified Fe₃O₄ makes the composites water-dispersible and can effectively load polyfluorene polyelectrolyte via electrostatic force. The high magnetism, excellent water dispersibility and strong photoluminescence make these composites ideal candidates for various important applications such as magnetic resonance imaging, bioseparation, bioimaging, and optical devices fabrication.     

Synthesis of graphene oxide and graphene quantum dots from miscanthus via ultrasound-assisted mechano-chemical cracking method

Whilst graphene materials have become increasingly popular in recent years, the followed synthesis strategies face sustainability, environmental and quality challenges. This study proposes an effective, sustainable and scalable ultrasound-assisted mechano-chemical cracking method to produce graphene oxide (GO). A typical energy crop, miscanthus, was used as a carbon precursor and pyrolysed at 1200 °C before subjecting to edge-carboxylation via ball-milling in a CO₂-induced environment. The resultant functionalised biochar was ultrasonically exfoliated in N-Methyl-2-pyrrolidone (NMP) and water to form GOs. The intermediate and end-products were characterised via X-ray diffraction (XRD), Raman, high-resolution transmission electron microscopy (HR-TEM) and atomic force microscopy (AFM) analyses. Results show that the proposed synthesis route can produce good quality and uniform GOs (8–10% monolayer), with up to 96% of GOs having three layers or lesser when NMP is used. Ultrasonication proved to be effective in propagating the self-repulsion of negatively-charged functional groups. Moreover, small amounts of graphene quantum dots were observed, illustrating the potential of producing various graphene materials via a single-step method. Whilst this study has only investigated utilising miscanthus, the current findings are promising and could expand the potential of producing good quality graphene materials from renewable sources via green synthesis routes.     

Studies on nanocrystalline (Sr,Pb)TiO3 solid solutions prepared via a facile self-propagating combustion method

Macroporous nanocrystalline (Sr,Pb)TiO₃ solid solutions were prepared by a facile self-propagating combustion method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy dispersive X-ray spectrum (EDS) and X-ray photoelectron spectroscopy (XPS). (Sr,Pb)TiO₃ solid solutions showed enhanced photocatalytic activity for the degradation of methyl orange (MO) than pure SrTiO₃ and an optimum performance was observed for Sr_29/32Pb_3/32TiO₃. The possible mechanism for the enhanced photocatalytic activity on (Sr,Pb)TiO₃ solid solutions was proposed.     

Effect of barium doping on the physical properties of zinc oxide nanoparticles elaborated via sonochemical synthesis method

The aim of this work is to study the effect of barium (Ba) doping on the optical, morphological and structural properties of ZnO nanoparticles. Undoped and Ba-doped ZnO have been successfully synthesized via sonochemical method using zinc nitrate, hexamethylenetetramine (HMT) and barium chloride as starting materials. The structural characterization by XRD and FTIR shows that ZnO nanoparticles are polycrystalline with a standard hexagonal ZnO wurtzite crystal structure. Decrease in lattice parameters from diffraction data shows the presence of Ba²⁺ in the ZnO crystal lattice. The morphology of the ZnO nanoparticles has been determined by scanning electron microscopy (SEM). Incorporation of Ba was confirmed from the elemental analysis using EDX. Optical analysis depicted that all samples exhibit an average optical transparency over 80%, in the visible range. Room-temperature photoluminescence (PL) spectra detected a strong ultraviolet emission at 330 nm and two weak emission bands were observed near 417 and 560 nm. Raman spectroscopy analysis of Ba-doped samples reveals the successful doping of Ba ions in the host ZnO.     

Optimization of effective parameters in the synthesis of nanopore anodic aluminum oxide membrane and arsenic removal by prepared magnetic iron oxide nanoparicles in anodic aluminum oxide membrane via ultrasonic-hydrothermal method

In this study, a new anodized aluminum oxide (AAO) nanostructure membrane was synthesized by anodization process under a constant voltage, in oxalic acid solution that was improved with trace amounts of sulfuric acid at room temperature. The effect of various parameters on the morphology of the synthesized nanostructures such as voltage, electrolyte composition, anodization time and type of stripping solution were investigated. According to the results, corrosion of the walls, size regularity, diameter and number of the pores increased in the presence of sulfuric acid (0.018 mol.L⁻¹). Nitrogen adsorption-desorption analysis confirmed significant porosity, array and uniformity of the pore size in the synthesized nanoporous membrane. A new modification method was used based on ultrasonic-hydrothermal method to modify the synthesized AAO with Fe₃O₄/SiO₂ nanoparticles for metals and metalloids removal from aqueous solution. In this method, Fe₃O₄/SiO₂ nanoparticles were placed very regularly and uniformly on the surface and inside the pores. This modification was confirmed by characterization techniques. The modified AAO@Fe₃O₄/SiO₂ membrane showed excellent results for removing arsenic from aqueous media.     

Aqueous electrochemical insertion of Na into the tungsten oxide hybrid WO3(4,4′-bipyridyl)0.5

Aqueous electrochemical insertion of M⁺ (Na⁺ and H⁺) species into WO₃(4,4′-bipyridyl)_0.5 has been carried out. The chemical states and structure of the resulting product were analysed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). XPS showed the presence of W⁶⁺ as well as the usual reduced W species (W⁵⁺) which is responsible for a change in colour. Moreover, the presence of these intercalates correlates with the evolution of the reduced W species. The bulk structure of the layered hybrid, as determined by powder X-ray diffraction, showed no alteration after electrochemistry, in contrast to the same measurements on tungsten trioxide (WO₃). This however concurs with single-crystal X-ray studies, which show little change in lattice parameters with Na⁺ insertion. Four-probe resistance measurements of the layered hybrid coated film display a drop in resistance after electrochemistry, which can be attributed to the injection of charge-carriers into the conduction band.     

Investigation of the spontaneous emission rate of perylene dye molecules encapsulated into three-dimensional nanofibers via FLIM method

The decay dynamics of perylene dye molecules encapsulated in polymer nanofibers produced by electrospinning of polymethyl methacrylate are investigated using a confocal fluorescence lifetime imaging microscopy technique. Time-resolved experiments show that the fluorescence lifetime of perylene dye molecules is enhanced when the dye molecules are encapsulated in a three-dimensional photonic environment. It is hard to produce a sustainable host with exactly the same dimensions all the time during fabrication to accommodate dye molecules for enhancement of spontaneous emission rate. The electrospinning method allows us to have a control over fiber diameter. It is observed that the wavelength of monomer excitation of perylene dye molecules is too short to cause enhancement within nanofiber photonic environment of 330 nm diameters. However, when these nanofibers are doped with more concentrated perylene, in addition to monomer excitation, an excimer excitation is generated. This causes observation of the Purcell effect in the three-dimensional nanocylindrical photonic fiber geometry.     

A general method for preparing lanthanide oxide nanoparticles via thermal decomposition of lanthanide(III) complexes with 1-hydroxy-2-naphthoic acid and hydrazine ligands

Six new lanthanide(III) complexes (i.e., [Ln(L)₂(NA)_1.5]·3H₂O, where Ln=La(III), Pr(III), Nd(III), Sm(III), Gd(III), and Ce(III) and L and NA indicate N₂H₄ and C₁₀H₆(1-O)(2-COO), respectively) with 1-hydroxy-2-naphthoic acid [C₁₀H₆(1-O)(2-COOH)] and hydrazine (N₂H₄) as co-ligands were characterized by elemental, FTIR, UV-visible, and XRD techniques. In the FT-IR spectra, the N-N stretching frequency in the range of 981–949 cm⁻¹ demonstrates evidence of the presence of coordinated N₂H₄, indicating the bidentate bridging nature of hydrazine in the complexes. These complexes show symmetric and asymmetric COO⁻ stretching from 1444 to 1441 cm⁻¹ and 1582 to 1557 cm⁻¹, respectively, indicating bidentate coordination. TG-DTA studies revealed that the compounds underwent endothermic dehydration from 98 to 110 °C. This was followed by the exothermic decomposition of oxalate intermediates to yield the respective metal oxides as the end products. From SEM images, the average size of the metal oxide particles prepared by thermal decomposition of the complexes was determined to be 39–42 nm. The powder X-ray and SEM coupled with energy dispersive X-ray (EDX) studies revealed the presence of the respective nano-sized metal oxides. The kinetic parameters of the decomposition of the complexes were calculated using the Coats-Redfern equation.