[en] The feasibility of preparing amorphous Ni₅₇Zr₂₀Ti₂₀Si₃ composite powders by mechanical alloying of pure Ni, Zr, Ti, Si, and ceramic powder mixture after 5 h milling was investigated. The as-milled powders were examined by X-ray diffraction, scanning electron microscopy, and differential thermal analysis. Amorphous Ni₅₇Zr₂₀Ti₂₀Si₃ composite powders were prepared successfully at the end of milling for all the compositions studied. The thermal stability of the amorphous matrix is not significantly affected by the presence of the ceramic particles. It is suggested a partial dissolution of the atoms constituting the ceramic species in the amorphous phase can result change of matrix composition and lead to the variation of the glass transition and crystallization behaviors

[en] In the present study, high-yield W₁₈O₄₉-TiO₂ core–shell nanoparticles were prepared by modified plasma arc gas condensation without any catalysts or substrates. All the as-prepared samples were characterized by FEG-SEM, XRD, FEG-STEM, and HAADF analytic techniques. The results of the structural analysis show that the as-prepared nanoparticles presenting a core–shell morphology with an average diameter of 43.5 ± 8.0 nm were composed of non-stoichiometric tungsten oxide (W₁₈O₄₉ phase) as the core (20–40 nm) and rutile-phase TiO₂ as the shell with non-uniform thickness (10–20 nm). For the optical properties of the as-prepared W₁₈O₄₉-TiO₂ core–shell nanoparticles, Raman spectroscopy and photoluminescence (PL) spectra were used. Compared with pure TiO₂ and W₁₈O₄₉ nanocrystals, the experimental results reveal that the defects in the lattice between the core and shell layers induced the board and shifted peaks in Raman spectra. Also, W₁₈O₄₉-TiO₂ core–shell nanoparticles exhibited green emission at 483 nm wavelength observed in PL spectrum. Thermal gravimetric analyzer (TGA) results indicate that the TiO₂ shell served a stable layer and prevented further oxidation from the atmosphere of the W₁₈O₄₉ core, thereby improving the thermal stability of W₁₈O₄₉ nanoparticles.

[en] With the use of a modified plasma arc gas condensation technique and control of the processing parameters, namely, plasma current and chamber pressure, we synthesized tungsten oxide nanomaterials with aspect ratios ranging from 1.1 (for equiaxed particles with the length and width of 48 nm and 44 nm, respectively) to 12.7 (for rods with the length and width of 266 nm and 21 nm, respectively). The plasma current and chamber pressure, respectively, ranged from 70 to 90 A and from 200 to 600 Torr. We then characterized the tungsten oxide nanomaterials by means of X-ray diffraction, high-resolution transmission electron microscope, UV-visible spectroscope, and photoluminescence (PL) spectroscope. Experimental results show that equiaxed tungsten oxide nanoparticles were produced at a relatively low plasma current of 70 A, whereas nanorods were produced when plasma currents or chamber pressures were increased. All of the as-prepared tungsten oxide nanomaterials exhibited a WO_2.8 phase. Compared to the nanoparticles, the nanorods exhibited unique properties, such as a redshift in the UV-visible spectrum, a blue emission in PL spectrum, and a good performance in field emission. With respect to the field emission, the turn-on voltage for WO_2.8 nanorods was found to be as low as 1.7 V/μm.

[en] Hierarchical thin-film photocatalysts exhibiting surface roughness at two length scales were prepared by the consecutive formation of ZnO microstripes and ZnO nanorod-array. ZnO stripes with microscale roughness were fabricated after removing the ink-jet printed ribs. Then, nanoscale roughness was achieved by the growth of ZnO nanorods on the surface. The surface morphology and structural and optical properties were characterized by FESEM, X-ray diffraction, XPS, photoluminescence and UV–vis spectroscopy. The photocurrents of selectively grown ZnO nanorods under UV or visible light irradiation were investigated by scanning electrochemical microscopy with a scanning optical fiber. The surface comprising hierarchical microstructures and nanostructures not only increases the surface area of the photocatalyst but also helps the diffusion of organic dye during the photodegradation test. The photodegradation efficiency of the hierarchical thin-film photocatalyst was improved compared with the ZnO nanorod photocatalyst. Photocatalytic performance was further enhanced when Ag nanoparticles were deposited on the hierarchical photocatalyst. - Highlights: ► Hierarchical photocatalyst made by ink-jet printing and hydrothermal process ► Immobilized hierarchical photocatalyst with microscale and nanoscale roughness ► Increased active surface area and improved diffusion of dye ► Improved photocatalysis by changing surface texture and depositing Ag nanoparticle

[en] In this study, tungsten oxide films were prepared by sol–gel technique. Various amounts of multiwalled carbon nanotubes (MWCNTs) were added during sol–gel process to obtain hybrid WO₃/MWCNT films. The original and hybrid films were characterized by thermogravimetric analysis, X-ray diffraction analysis, and scanning electron microscopy analysis, whereas the electrochromic performance was evaluated by measuring changes in the optical transmittance caused by potentiostatic charge–discharge intercalation. The influence on the structure and properties of tungsten oxide film due to MWCNT addition was also investigated. The results showed that all of the films were amorphous and exhibited porous microstructure. The electrochromic performance of pristine WO₃ film was improved by adding MWCNTs that served as a template for the growth of WO₃ and resulted in more porous microstructure. The hybrid tungsten oxide films with 0.1 wt.% MWCNT addition exhibited the best electrochromic performance.

[en] In the present study, titania-doped (Ti-doped) W₁₈O₄₉ nanorods have been prepared using a modified plasma arc gas condensation technique. Characterizations by field-emission gun scanning electron microscopy, X-ray powder diffraction, high-resolution transmission electron microscopy and high-resolution X-ray photoelectron spectroscopy indicate that the as-prepared nanorods with a single-crystalline monoclinic W₁₈O₄₉ phase are of 20–100 nm in diameter and several micrometers in length. The Raman peaks of the Ti-doped W₁₈O₄₉ nanorods show a red-shift Raman peaks, and an additional green-emission peak at 497 nm is observed in the photoluminescence (PL) spectrum compared to pure W₁₈O₄₉ nanorods. Field-emission (FE) measurements reveal that the turn-on (E_to) and threshold (E_thr) voltages of the Ti-doped W₁₈O₄₉ nanorods are 2.2 and 3.4 V/μm, respectively. A vapor–solid process that does not involve the use of catalyst is proposed for the nanorod growth mechanism. Experimental results show that the additional defects resulting from titania doping are responsible for the enhancement of the optical and FE properties of the pure W₁₈O₄₉ nanorods.

[en] Despite the fact that polystyrene (PS) spheres have been developed as polymeric carriers or matrices for various biomedical applications, the synthesis of PS spheres is time-consuming. This work describes the fabrication of a uniform PS sphere, coated with silver nanoparticles (Ag–PS), by simultaneous photoinduced polymerization and reduction fabricated using x-rays in aqueous solution without any initiator. The solution contains only styrene, silver ions (Ag⁺), and poly(vinyl pyrrolidone) (PVP) as a stabilizer. The proposed mechanism of the formation of the Ag–PS nanocomposite spheres involves the generation of radicals in the aqueous solution to induce PS polymerization and the reduction of Ag. The distribution of the sizes of the core PS spheres in the Ag–PS nanocomposite spheres was systematically examined as a function of irradiation time, concentration of styrene, and amount of PVP. Ag–PS nanocomposite spheres exhibit antimicrobial activity against bacteria (Escherichia coli and Staphylococcus aureus). Additionally, the cationic (vinylbenzyl)trimethylammonium (TMA) monomer was photopolymerized to form positively charged TMA–PS spheres as gene carriers with uniquely low cytotoxicity. Given these design advantages, the method proposed herein is simpler than typical approaches for synthesizing PS spheres with functionalized groups and PS spheres coated with Ag nanoparticles. (paper)

[en] Transparent semiconductor thin films of Zn_1-xTi_xO (0 ≤ x ≤ 0.12) were deposited on alkali-free glass substrates by the sol-gel method. The effects of Ti addition on the crystallization, microstructure, optical properties and resistivity of ZnO thin films were investigated. The as-coated films were preheated at 300 ^oC, and then annealed at 500 ^oC in air ambiance. X-ray diffraction results showed all polycrystalline Zn_1-xTi_xO thin films with preferred orientation along the (002) plane. Ti incorporated within the ZnO thin films not only decreased surface roughness but also increased optical transmittance and electrical resistivity. In the present study, the Zn_0.88Ti_0.12O film exhibited the best properties, namely an average transmittance of 91.0% (an increase of ∼ 12% over the pure ZnO film) and an RMS roughness value of 1.04 nm.

[en] Highlights: ► Na-doped vanadium oxide is successfully prepared by an electrodeposition technique. ► Microstructure and Na content of the oxide are controlled by deposition potential. ► A lower deposition potential leads to a higher porosity of the prepared oxide. ► Na doping significantly increases the oxide capacitance. ► The nanostructured Na-doped oxide shows an ideal supercapacitor performance. - Abstract: Vanadium-based oxides are prepared on graphite substrates by an anodic deposition technique. The plating bath is 0.2 M VOSO₄ solution with NaCH₃COO addition. A scanning electron microscope and an X-ray diffractometer are used to characterize the deposits; the analyses indicate that the porous Na-doped V₂O₅ electrodes with a nano-crystalline nature are obtained. Supercapacitor properties of the oxide electrodes are studied using cyclic voltammetry in KCl aqueous electrolyte. The data show that the deposited oxides can exhibit ideal capacitive behavior over a potential range of 1 V; the optimum specific capacitance is ∼180 F/g. A lower deposition potential leads to a higher porosity of the oxide, resulting in a better high-rate supercapacitor performance of the electrode.

[en] Electrochromic WO₃ films are prepared by the electron-beam evaporation method. The as-deposited films are amorphous in structure. The optical transmittance spectra show 13.4% decay of optical modulation after 20 electrochemical cycles. The degradation behaviour of the WO₃ films is also observed in electrochemical step potential measurements. X-ray absorption spectroscopy indicates that the absorption energy of the W L_III-edge shifts towards lower energy with the insertion of Li⁺ ions and electrons. The results of radial distribution functions reveal that the increase in the distance of the W-O bonds is caused by the reduction in W ions. Li_xWO₃ and Li₂WO₄ are formed at -0.5 V and -1.0 V, respectively, during electrochemical insertion, as observed by transmission electron microscopy. The Raman scattering analysis indicates that only two ionic states, W⁴⁺ and W⁶⁺, exist in the WO₃ films, due to excess injection of electrons and Li⁺ ions. We suggest that the degradation of the electrochromic properties of the WO₃ films during electrochemical cycles is related to the formation of different W ionic states. (paper)