Controllable synthesis of Zn0.95Co0.05O nanowires and nanotubes by electrophoretic deposition method

Zn_0.95Co_0.05O nanotubes, as well as nanowires, were controllably synthesized by electrophoretic deposition method using anodic aluminum oxide (AAO) as template, and the mechanism of electrophoretic deposition was discussed. Careful characterization indicates that the prepared nanotubes and nanowires are of poly-crystal wurtzite structure and composed with 8–15 nm nano-crystals. The doped Co²⁺ occupied the Zn²⁺ sites in the ZnO lattice. Magnetic investigation indicates that the obtained nanotubes and nanowires are of room-temperature ferromagnetic. The magnetism of the nanotubes is much higher than that of the nanowires for the surface-preferential Co distribution.     

Electrochemical characteristics of single crystalline nanowires and their driven mechanism

The electrochemical characteristics of single crystalline SnO₂, ZnO and Si nanowires and their driven mechanism are reported as nanostructural anode materials. As intercalation and deintercalation of Li, Si nanowires are converted to amorphous phases of shorter wire shapes caused by the lattice expansion of the single crystalline Si, resulting in the fading of discharge capacity, although the reversible capacity (2500 mAh/g) in the first cycle is very high. However, oxide nanowries (SnO₂ and ZnO) are transformed from a single crystalline structure into a polycrystalline form consisting of nano-sized metallic particles and Li₂O crystals within the wires, which maintain their discharge capacity. The results of this study imply that the large surface area and high electrochemical activity of nanowires and nano-sized polycrystalline particles can provide a method to develop a new class of one-dimensional anode nanostructures in lithium-ion rechargeable batteries.     

Zn0.95Co0.05O纳米线和纳米管的电泳沉积法可控合成（英文）

以阳极氧化铝为模板通过电泳沉积法制备Zn0.95Co0.05O纳米线和纳米管,并对电泳沉积法制备纳米线(管)的机理进行研究。系统的结构表征表明所得的纳米管和纳米线是由8～15nm的纤锌矿纳米晶构成的多晶结构,Co2+离子以代位掺杂形式掺入晶格,取代了晶格中的Zn2+离子。磁性表征显示制备的纳米线和纳米管具有室温铁磁性。由于Co在纳米线(管)中表面择优分布,纳米管的磁性明显高于纳米线。     

Annealing-induced enhancement of ferromagnetism in SnO2-core/Cu-shell coaxial nanowires

In this study, we have coated tin oxide (SnO₂) nanowires with a Cu shell layer via the sputtering method and subsequently investigated the effects of thermal annealing. The annealing-induced changes in morphologies, microstructures, and compositions of the resulting core-shell nanowires were characterized by using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and energydispersive X-ray spectroscopy (EDX). The Cu shell layers were agglomerated to form clusters, which were mainly comprised of the Cu₂O phase. For the first time, a hysteresis loop indicating weak ferromagnetism was observed from the pure SnO₂ nanowires. Both the coercivity and the retentivity in the hysteresis loop were slightly increased by Cu-sputtering, indicating a very slight enhancement of ferromagnetism. Also, the ferromagnetic behavior was significantly enhanced by thermal annealing. We discuss the possible mechanisms of annealing-induced enhancement of ferromagnetism in the SiO₂/Cu core-shell nanowires, which include the generation of Cu₂O phase, Cu-doping into the SnO₂ lattice, and the generation of oxygen vacancies in SnO₂ core nanowires.     

A facile synthesis of polythiophene nanowires

Polythiophene nanowires have been synthesized by the gamma radiation-induced chemical oxidative polymerization method. The resultant fiber-like polymer structures were identified by the field-emission scanning electron microscopy with diameter of the order of 50–100 nm and a length of up to several millimeters. Different characterizations, e.g. elemental analysis, Fourier transform infrared, Raman spectroscopy, and X-ray photoelectron microscopy were utilized to prove that conducting polythiophene was synthesized successfully by this facile method.     

Structure and magnetic properties of iron nanowires encased in multiwalled carbon nanotubes

By using X-ray diffraction, transmission electron microscopy, ferromagnetic and electron paramagnetic resonances, Fe-filled multiwalled carbon nanotubes were studied. The iron within the nanotubes was found to be in three phases: the austenite γ-Fe is located at the top of the nanotubes, while the ferrite α-Fe and cementite θ-Fe₃C are found close to the substrate. The morphology of the α + θ mixture suggests that the eutectoid reaction γ → α + θ occurs. Two ferromagnetic signals were observed and identified as those belonging to ferrite and cementite. Ferromagnetic signals revealed a surprising temperature dependence: with decreasing temperature, their integral intensity decreases nearly linearly, and the signals disappear at temperatures below 70 K. Possible reasons for this behaviour are discussed. Two paramagnetic signals appear at low temperatures. Based on their temperature behaviour and on the values of the g-factors, the first signal is related to localized spin moments and the second one to free electrons.     

Synthesis, characteristics, and field emission of doped and de-doped polypyrrole, polyaniline, poly(3,4-ethylenedioxythiophene) nanotubes and nanowires

Doped and de-doped nanotubes and nanowires of polypyrrole, polyaniline, and poly(3,4-ethylenedioxythiophene) were synthesized by the electrochemical polymerization method, using Al₂O₃ nanoporous templates. The electrical and optical properties of the nanotubes and nanowires were controlled through various synthetic conditions, such as doping level, dopant, and template-dissolving solvents. The diameters and wall thicknesses of the nanotubes were 100–200 nm and 10–30 nm, respectively. To determine the electrical and optical properties of the nano-systems, I–V characteristic curves with gate bias, dc conductivity, and UV–vis spectra were measured. We observed that the nano-systems were transformed from a conducting state to a semiconducting (or insulating) state through the process of de-doping using the template-dissolving solvents. Possible applications of these nanotubes and nanowires in the construction of nanotip emitters in field emission displays and polymer-based transistors are presented.     

Fabrication and applications of metal-oxide nano-tubes

Metal-oxide nanotubes can be used for a wide range of applications, such as selective chemical and biological sensors, dye-sensitized solar cells and photo-catalysts. The fabrication methods can be categorized into a directed method using nanotemplates (sol-gel method and atomic layer deposition) and a non-directed method (anodization). This review article describes the recent progress made in the field of oxide nanotube synthesis and applications. We begin this review with a comprehensive study on the research activities in the oxide nanotube fabrication. We then focus on pristine metal oxide applications as well as surface-modified metal oxide nanotube applications. Finally, we summarize this article with future direction in the oxide nanotube applications.     

Transformation of metal nanowires into metal nanotubes by a sequential thermal process

The simple, low-cost and scalable transformation of metallic nanowires to metallic nanotubes was demonstrated by employing sequential thermal treatments.

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Electrochemical synthesis of polypyrrole nanowires on composite electrode

Polypyrrole nanowires growing with two-dimensional instantaneous nucleation and one-dimensional growth pattern were realized on graphite/paraffin composite electrode in phosphate buffer solution.     

Low-temperature synthesis of SiC nanowires with Ni catalyst

SiC nano wires were fabricated on the silicon substrate dipped with a layer of Ni catalyst at 900 ℃ by gas pressure annealing processing. The morphologies and crystal structures were determined by scanning electron microscopy(SEM), transmission electron microscopy(TEM)and X-ray diffraction(XRD). The results show that the assynthesized nanowires are β-SiC single crystalline with diameter range of 50-100 nm, and length of tens of micron by directly annealing at 900 ℃. The SiC nano wires grow along the [111] direction with highly uniform morphology. And the possible growth mechanism of SiC nano wires is proposed.The present work provides an efficient strategy for the production of high-quality SiC nano wires.     

镍纳米线的简易合成及其气敏性能(英文)

采用水热法,以聚乙二醇(PEG)作为辅助剂,通过先驱物NiC2O4·2H2O合成氧化镍纳米线,并通过SEM和XRD对样品的微观结构进行分析。实验结果显示:PEG对镍线的合成起重要作用,镍纳米线表现出良好的气敏性能。该形态使得氧化镍(NiO)可作为传感器的气敏材料得到应用。     

Facile synthesis of NiO nanowires and their gas sensing performance

The NiO nanowires were prepared by a facile PEG assisted hydrothermal method using NiC₂O₄·2H₂O as a precursor compound. The microstructure of the samples was characterized by SEM and XRD. The gas sensing properties of the NiO nanowires toward ethanol was also investigated. The results show that PEG plays a key role in the synthesis of wire-like NiO. The NiO nanowires show excellent sensing performances to ethanol gas. This morphology holds substantial promise for applying NiO as a potential gas sensing material for future sensor application.     

Synthesis of single crystalline CdS nanowires with polyethylene glycol 400 as inducing template

Solvothermal technique, an one-step soft solution-processing route was successfully employed to synthesize single crystalline CdS nanowires in ethylenediamine medium at lower temperature （170 □） for 1-8 d. In this route, polyethylene glycol 400 （PEG400） was used as surfactant, which played a crucial role in preferentially oriented growth of semiconductor nanowires. Characterizations of as-prepared CdS nanowires by X-ray powder diffraction（XRD）, transmission electron microscopy（TEM） indicate that the naonowires, with typical diameters of 20nm and lengths up to several micrometers, have preferential [001] orientation. Also, investigations into the physical properties of the CdS nanowires were conducted with UV-Vis absorption spectroscopy and photoluminescence emission spectroscopy. The excitonic photo-optical phenomena of the nanowires shows the potential in the practical applications.     

A simple route for the synthesis of copper nanowires

We have synthesized Cu nanowires via a simple process using both thermal evaporation and CuCl powders. In this method, complicated processes and special instruments are not required to synthesize Cu nanostructures. In addition, we have used commercial CuCl powders as a precursor. There have been no reports on the preparation of Cu nanostructures using simple instruments together with a commercial source material as in this study. Cu nanostructures of various morphologies were formed at relatively low temperature. The microstructure of the Cu nanostructures was investigated using HRTEM images and SAD pattern analysis.     

Bi2Te3纳米颗粒和纳米线的溶剂热合成及组织特征

分别以吡啶、无水乙醇为反应介质,以NaBH4为还原剂,采用溶剂热合成方法,在150℃下反应24 h制备了平均晶粒尺寸为15～20 nm的Bi2Te3纳米粒子.采用相同的合成方法,以去离子水为反应介质,合成了直径为30～80 nm,长径比大于100的Bi2Te3纳米线.XRD和TEM分析表明,随着溶剂介电常数和极性增加,所生成产物的物相纯度、结晶度增高,晶粒尺寸增大.     

Electrochemical synthesis of polypyrrole nanowires in the presence of gelatin

Biotemplating is an emerging, unique approach for the synthesis and organization of the organic or inorganic materials into well-defined nanostructures. In this article, conducting polymer polypyrrole (PPy) nanowires were electrochemically synthesized using a protein molecule, gelatin, as a template. The morphologies, microstructures, chemical compositions, and electrochemical performances of the obtained nanowires were investigated in detail. It was found that the gelatin played an important role in the formation of the PPy nanowires and the morphologies of the nanowires were closely related to the electrodes used. This work not only extended the application of gelatin to the synthesis of the conducting polymer nanowires, but also presented a simple and useful route to the fabrication of PPy nanowires with different length, from normal size to superlong size.     

The homogeneous dispersion of surfactantless,slightly disordered,crystalline, multiwalled carbon nanotubes in α-alumina ceramics for structural reinforcement

Surfactantless, hydrophilic, slightly disordered, crystalline, multiwalled carbon nanotubes (CNTs) were successfully prepared and then homogeneously and individually incorporated in an α-alumina ceramic by a recently established powder technology to investigate their load-carrying and reinforcing capabilities. As predicted, considerable structural reinforcement was obtained after spark plasma sintering, and microstructural characterizations can experimentally prove the effectiveness of the ability of these CNTs to reinforce the alumina ceramic matrix. Reinforcement mechanisms are thoroughly discussed in terms of microstructural characterizations.     

A simple catalyst-free route for large-scale synthesis of SiC nanowires

A large number of SiC nanowires were fabricated by a simple catalyst-free method using silicon powders and expandable graphite as raw materials. Digital camera, X-ray diffractometer, Fourier transform infrared spectrometer, field-emission scanning electron microscopy and transmission electron microscopy demonstrate that a large number of loose products were obtained in graphite crucible. The products are composed of single crystalline 3C-SiC nanowires with lengths up to several tens of micrometers and diameters of 20-60 nm. The vapor-solid mechanism was proposed to interpret the growth procedure of SiC nanowires. The expandable graphite as carbon source can provide enough growth space for nanowires, which is helpful to improve the yield of SiC nanowires. The simple method provides a promising candidate for industrial fabrication of SiC nanowires.     

In situ synthesis and photoluminescence of SiC nanowires by microwave-assisted pyrolysis of methane

A simple method was used to synthesize SiC nanowires directly on quartz plate by microwave pyrolysis of methane. The samples have been characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Raman spectroscopy techniques. The results showed that the nanowires are of cubic β-SiC structure with stacking faults. The diameters of SiC nanowires are in the range of 50–200 nm and their lengths up to several tens of microns. The effect of the reaction gas concentration and the reaction temperature on the morphologies of SiC nanowires was also investigated. Two broad photoluminescence peaks at the center wavelength of about 309 and 417 nm were observed at room temperature.