Tungsten Oxide Nanorods Array and Nanobundle Prepared by Using Chemical Vapor Deposition Technique

Tungsten oxide (WO₃) nanorods array prepared using chemical vapor deposition techniques was studied. The influence of oxygen gas concentration on the nanoscale tungsten oxide structure was observed; it was responsible for the stoichiometric and morphology variation from nanoscale particle to nanorods array. Experimental results also indicated that the deposition temperature was highly related to the morphology; the chemical structure, however, was stable. The evolution of the crystalline structure and surface morphology was analyzed by scanning electron microscopy, Raman spectra and X-ray diffraction approaches. The stoichiometric variation was indicated by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy.     

Epitaxial growth of WOx nanorod array on W(001)

Nanorods of substoichiometric tungsten oxide (WO_x) were grown on W(001) substrates. Two methods for the growth of nanorods were used: oxidation of the substrate under appropriate conditions and the deposition of tungsten oxide from a tungsten foil heated in the presence of oxygen. The grown nanorods were observed using a scanning electron microscope and an atomic force microscope. The diameters of the nanorods were 5–20 nm. The nanorods were slightly inclined from the directions parallel or normal to the surface. The inclination of nanorods was explained in terms of the epitaxial relationship between WO₃ crystals and the W(001) substrate. The WO₃ crystals formed at the initial stage of growth act as the nuclei of WO_x nanorods. We observed selective enhancement of the growth in a certain epitaxial direction depending on the method of growth, and an array of WO_x nanorods was produced on the W(001) substrate.     

NiFe2O4–Ni3S2 nanorod array/Ni foam composite catalyst indirectly controlled by Fe3+ immersion for an efficient oxygen evolution reaction

A NiFe alloy was designed on nickel foam (NF) as a precursor using cathodic electrodeposition. NiFe₂O₄–Ni₃S₂ nanorods (NRs) composite catalysts were prepared by Fe³⁺ impregnation and further hydrothermal sulfuration methods. NiFe₂O₄–Ni₃S₂ nanosheets (NSs) were also prepared by direct hydrothermal sulfuration of the NiFe alloy for comparison. Compared to the dense NS structure of the NiFe₂O₄–Ni₃S₂ NSs/NF, the NiFe₂O₄–Ni₃S₂ NRs/NF showed better oxygen evolution performance due to its unique weed-like NR array structure composed of additional oxygen evolution reaction (OER) active sites, with a strong electron interaction for Ni and Fe and the active sulfide synergistic effect with oxides. Therefore, Driving a current density of 10 mA cm^?2 only requires an overpotential of 189 mV and the catalyst could provide 100 mA cm^?2 continuously and be constant for more than 80 h in 1.0 M KOH. This experiment indicated that Fe³⁺ immersion had an indirect regulating effect on the morphological growth of the catalyst, which provided a novel concept for designing better OER catalysts.     

Effect of seed layer on the growth of rutile TiO2 nanorod arrays and their performance in dye-sensitized solar cells

In order to improve the performance of TiO₂ photoanode-based dye sensitized solar cells (DSSCs), rutile TiO₂ nanorod arrays (NRAs) were grown on SnO₂:F (FTO) conductive glass coated with TiO₂ seed layer by a hydrothermal method. The TiO₂ seed layer was obtained by spin-coating titanium tetraisopropoxide (TTIP) isopropanol solution with concentration in the range of 0~0.075 M. Then the effect of the thin TiO₂ seed layer on the crystal structure and surface morphology of TiO₂ NRAs and the photoelectric conversion properties of the corresponding DSSCs were investigated. It is found that TiO₂ NRAs are vertically oriented, about 1.7 μm long and the average diameter is about 35 nm for the samples derived from TTIP in the range of 0.005~0.05 M, which are more uniform and better separated from each other than those without TiO₂ seed layer (average diameter 35~85 nm). The photoelectric conversion efficiency of DSSCs based on TiO₂ NRAs with TiO₂ seed layer is larger than that without TiO₂ seed layer. Typically, the energy efficiency of DSSCs obtained from the seed solution of 0.025 M TTIP is 1.47%, about 1.8 times greater than that without TiO₂ seed layer. The performance improvement is attributed to the thinner, denser and better oriented NRAs grown on seeded-FTO substrate absorbing more dye and suppressing charge recombination at the FTO substrate/electrolyte interface.     

Directed electrochemical synthesis of ZnO/PDMcT core/shell nanorod arrays with enhanced photoelectrochemical properties

In this paper, we demonstrate a simple two-step electrochemical deposition strategy for synthesizing ZnO/Poly(2,5-dimercapto-1,3,4-thiadiazole) (PDMcT) core/shell nanorod arrays. The as-synthesized ZnO/PDMcT samples are characterized by Fourier-transform infrared (FTIR), Raman spectroscopy, power X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The ZnO/PDMcT nanorod arrays are found to exhibit significantly enhanced photocurrent density in photoelectrochemical cell applications as compared to the prinstine ZnO nanorod arrays.     

垂直生长于锌基底的Co掺杂ZnO纳米棒阵列显著室温铁磁性能

通过简单的水热合成法在锌片基底上一步制备了Co掺杂的ZnO纳米棒阵列。纳米棒在基底上均匀分布,取向一致,垂直于基底大面积生长。样品结构均为六方纤锌矿结构,具有高结晶质量,不含其它杂相。随着Co掺杂浓度的增加,紫外发射峰强度逐渐下降,近带隙发射峰的半峰宽也较纯ZnO变宽。拉曼光谱显示Co的掺杂使纳米棒出现了氧空位和锌填隙本征缺陷。随着Co浓度的增加这些缺陷也随之增加。掺杂纳米棒阵列的磁滞回线表明样品具有明显的铁磁特征,并有较大的矫顽力Hc~660 Oe。这种ZnO基稀磁半导体纳米棒阵列是一种在自旋电子器件中具有应用潜力的纳米材料。     

Synthesis of Nanocrystalline Hydroxyapatite Nanorods via Hydrothermal Conditions

The effect of Ca(NO₃)₂·4H₂O and (NH₄)₂HPO₄ primary solutions as the starting materials in the synthesis of a calcium phosphate phase was examined. Therefore, wet chemical reactions were investigated in solution at different temperatures by hydrothermal conditions aimed at hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HAp) synthesis. The powders were investigated by XRD, SEM, FE‐TEM, HRTEM, EDAX, SAED, and FTIR. It is found that the HAp have diameters of 25–50 nm and lengths of 120�30 nm with different morphologies. As a matter of fact, the hydrothermal method guarantees the production of HAp for different applications.     

Growth of ZnO nanorod forests and characterization of ZnO-coated nylon fibers

ZnO nanorod forests were grown wrapping nylon fibers using a two-step process. In the first step, the formation of ZnO seeds at nylon fiber surfaces was induced by the dip coating of ZnO nanosols; in the second step, the growth of the ZnO seeds into nanorod forests was carried out via a wet chemical route in a bath containing an equimolar solution of zinc nitrate hexahydrate and hexamethylenetetramine. The as-obtained ZnO-coated nylon fibers were characterized by scanning electron microscopy, Energy dispersive X-ray spectrum imaging, and X-ray diffraction, respectively. Thermal gravimetric analysis of the pristine and the ZnO-coated nylon fibers was also conducted.     

The dynamic behaviors of diblock copolymer/nanorod mixtures under equilibrium and nonequilibrium conditions

Cylindrical diblock copolymer/anisotropic nanorod composites under equilibrium and nonquilibrium conditions, have been modeled and simulated using dissipative particle dynamics. The aim of our present study is to understand how the anisotropic NRs affect the equilibrium self-assembled structure of diblock copolymers (DBCPs) melts and how the shear flow induces the dynamic behaviors of DBCPs/NRs composites, especially the orientation and distribution of NRs in diblock matrix. We consider two different shear directions categorized with respect to the flow velocity parallel or perpendicular to the orientation of initial structures, which are defined as z-axis shear flow and x-axis shear flow, respectively. Our results show the shear flow not only aligns the orientation of DBCPs template and the dispersed NRs toward the flow direction, but also regulates the orientational and positional order of NRs. The final self-assembly behaviors of DBCPs/NRs nanocomposites is determined by the interplay between shear-induced polymer thinning and NRs dispersion. This work provides us a viable strategy for creating polymer nanocomposites with tunable and enhanced processing properties.     

Cooperative surface-induced self-assembly of symmetric diblock copolymers confined films with embedded nanorods

The self-assembly of symmetric diblock copolymers confined films with embedded nanorods is investigated by the self-consistent field (SCF) theory. We obtain some phase diagrams as a function of film thickness H and nanorod diameter D. The increase in preferential nanorod diameter D can promote the formation of incomplete cylindrical and spherical structures near the film surfaces, and can also induce complete lamellar, cylindrical and spherical structures in the interior. The formation of these induced self-assembled structures is due to the competition between inner surface confinement (two parallel surfaces) and outer surface confinement (nanorods). This investigation can provide some insights into the self-assembly of diblock copolymers with complex confinements.