Preparation and characterization of Bi2Se3 nanowires by electrodeposition

The electrodeposition of Bi₂Se₃ nanowires on an anodic aluminum oxide template was investigated by cyclic voltammetry in a tartaric acid aqueous solution. The electrochemical behavior of the Bi₂Se₃ nanowires in the electrolytic solution was also investigated using cyclic voltammetry, and the underpotential deposition mechanism of the Bi₂Se₃ nanowires was determined. According to the cyclic voltammetric curves, −0.20 V vs. SCE (saturated calomel electrode) was chosen as the deposition potential of the Bi₂Se₃ nanowires. The ratio of Bi to Se is nearly 2:3, verified by energy-dispersive X-ray spectroscopy and with the addition of surfactant. X-ray diffraction, scanning electron microscopy, selected-area electron diffraction and high-resolution transmission electron microscopy indicate that annealing can improve the crystallinity and chemical composition of Bi₂Se₃ nanowires. Surfactant can also improve the surface morphology and composition of the Bi₂Se₃ nanowires.     

Single-step synthesis of germanium nanowires encapsulated within multi-walled carbon nanotubes

We report the single-step synthesis of Ge nanowires encapsulated within multi-walled carbon nanotubes (MWCNTs) from a phenyltrimethylgermane (C₆H₅Ge(CH₃)₃) precursor, using a simple chemical vapor deposition (CVD) method. The MWCNT/germanium nanowires were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) measurements. TEM analysis reveals that the nanowires consist of well crystallized Ge cores which are completely encapsulated by the sheath-like MWCNTs, the latter corresponding to a layer thickness of 5-10 nm. SEM images, corresponding to various stages of nanowire growth, indicate that MWCNT growth occurs at Ge nanoparticles and that the growing MWCNTs carry Ge as nanowires away from the nanoparticles. By optimizing the CVD parameters, nanowires can be produced with uniform length and diameter in the range 6-10 μm and 200-300 nm, respectively.     

Growth of multi-morphology amorphous silicon oxycarbide nanowires during the laser ablation of polymer-derived silicon carbonitride

Multi-morphology amorphous SiOC nanowires were successfully prepared within the interfacial interstices between the unaffected SiCN ceramic and the bracket during the laser ablation of polymer-derived SiCN ceramic in a low-pressure argon atmosphere. Laser irradiation experiments were performed using a continuous-wave CO₂ laser, and the gas source for the growth of amorphous SiOC nanowires was provided by the laser ablation of the SiCN ceramic. X-ray photoelectron spectroscopy shows that the amorphous SiOC nanowires possess a SiO₂ dominated nanostructure, and the formation of amorphous SiOC nanowires is attributed to the good diffusivity of CO in SiO₂. The morphologies of the amorphous SiOC nanowires include straight nanowires, beaded nanowires, helical nanowires, and branched nanowires, and these are determined by the flowing state of the reactant gases, the laser power, and the surface morphology of the SiCN ceramics. Each amorphous SiOC nanowire with specific morphology can be uniformly distributed in separate regions, which makes it possible to control the growth of amorphous SiOC nanowires in different morphologies.     

Carbothermal Synthesis of the Nanostructures of Al2O3 and ZnO

Nanostructures of Al₂O₃ and ZnO have been synthesized by a carbothermal route involving the reaction of the metal or the metal oxide with carbon. In the case of Al₂O₃, nanowires and nanotubes are obtained starting with Al metal and active carbon or graphite. ZnO nanowires are obtained by the reaction of zinc oxalate or ZnO with active carbon or multiwalled carbon nanotubes. The Al₂O₃ and ZnO nanostructures obtained have been characterized by X-ray diffraction, electron microscopy and photoluminescence spectroscopy. These nanostructures are likely to be of use as catalyst supports and in other technological applications.     

In-situ generation Cu2O/CuO core-shell heterostructure based on copper oxide nanowires with enhanced visible-light photocatalytic antibacterial activity

As visible light-driven photocatalysts in wastewater treatment, Cu₂O/CuO composites have garnered considerable attention. Herein, Cu₂O/CuO core–shell nanowires were fabricated directly on a Cu mesh using a simple two-step synthesis process involving a wet chemical method and rapid annealing. Unlike conventional composite nanowires, controllable core–shell nanowires exhibit high photoelectrochemical properties and overcome the problems associated with the recovery of powder-based photocatalysts. The presence and structural distribution of the Cu₂O/CuO core–shell nanowires were confirmed using X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. Among the samples subjected to different rapid annealing temperatures for 180 s, the sample exposed to rapid annealing at 350 °C achieved the highest photocurrent density of ?6.96 mA cm^?2. In the core–shell nanowires fabricated on the samples, the ratio of Cu₂O/CuO was 1:1. The photocatalytic activity of the Cu₂O/CuO nanowire samples was also determined by measuring methyl blue degradation to determine their applicability in wastewater treatment. A remarkable photocatalytic degradation rate of 91.6% was achieved at a loading bias voltage of ?0.5 V. The Cu₂O/CuO heterojunction enhanced the photodegradation of the samples because the different bandgaps improved the dissociation of the photogenerated electron–hole pairs. Furthermore, the antibacterial activity of the Cu₂O/CuO nanowires exhibited considerable resistance against Escherichia coli and photocatalytic antibacterial treatment for only 20 min under visible light killed 10⁶ CFU/mL of E. coli. Therefore, the Cu₂O/CuO controllable core–shell nanowires with a high photodegradation performance and excellent antibacterial activity under general illumination show diverse applications in water treatment.     

Surface chemistry of SnO2 nanowires on Ag-catalyst-covered Si substrate studied using XPS and TDS methods

In this paper we investigate the surface chemistry, including surface contaminations, of SnO₂ nanowires deposited on Ag-covered Si substrate by vapor phase deposition (VPD), thanks to x-ray photoelectron spectroscopy (XPS) in combination with thermal desorption spectroscopy (TDS). Air-exposed SnO₂ nanowires are slightly non-stoichiometric, and a huge amount of C contaminations is observed at their surface. After the thermal physical desorption (TPD) process, SnO₂ nanowires become almost stoichiometric without any surface C contaminations. This is probably related to the fact that C contaminations, as well as residual gases from air, are weakly bounded to the crystalline SnO₂ nanowires and can be easily removed from their surface. The obtained results gave us insight on the interpretation of the aging effect of SnO₂ nanowires that is of great importance for their potential application in the development of novel chemical nanosensor devices.     

Electrochemical synthesis of silver oxide nanowires,microplatelets and application as SERS substrate precursors

We describe the electrochemical synthesis of silver oxide nanowires and nanowire bundles, filled platelets and hollow microplatelets in either basic or acidic N,N-dimethylformamide solution. We propose that these nanostructures are formed at the electrode surface via two competing reactions namely, silver dissolution off the electrode in the presence of NH₃ or HF during the anodization of silver, and silver oxide precipitation. Results show that the precipitated silver oxide nanoparticles aggregate into nanowires as well as into filled and hollow microscale platelets, depending upon the nuclei concentration and the anodization current density. X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX) and Raman scattering spectroscopy show that the nanowires and microplatelets are mainly composed of Ag₂O. Nanowire bundles are used as substrates for surface-enhanced Raman scattering (SERS) where single molecule detection is achieved and evidenced using a bianalyte Raman technique.     

Growth and optical properties of ZnO–In2O3 heterostructure nanowires

ZnO–In₂O₃ heterostructure nanowires were grown on a Si (111) substrate using the thermal evaporation method. Scanning electron microscopy results showed that the ZnO nanowires had spherical caps. The X-ray diffraction (XRD) pattern and energy-dispersive X-ray (EDX) spectrum indicated that these caps were In₂O₃. An analysis of the early growth process revealed that indium oxide might have played a self-catalytic role. Therefore, it was plausible that the vapor–liquid–solid mechanism (VLS) was responsible for the growth of the ZnO–In₂O₃ heterostructure nanowires. The optical properties of the products were characterized using a photoluminescence (PL) technique. The PL results for the ZnO–In₂O₃ heterostructure nanowires showed a strong peak in the ultraviolet region as a result of the near band emission and a negligible peak for the visible emissions that occurred as a result of the defects. Based on these PL results, it was found that the In₂O₃ nanostructures not only introduced the caps at the tips of the ZnO nanowires but also partially passivated the nanowire surfaces, leading to an improved near band edge emission and the suppression of the defect luminescence.     

The MoS2 Nanotubes with Defect-Controlled Electric Properties

We describe a two-step synthesis of pure multiwall MoS₂ nanotubes with a high degree of homogeneity in size. The Mo₆S₄I₆ nanowires grown directly from elements under temperature gradient conditions in hedgehog-like assemblies were used as precursor material. Transformation in argon-H₂S/H₂ mixture leads to the MoS₂ nanotubes still grouped in hedgehog-like morphology. The described method enables a large-scale production of MoS₂ nanotubes and their size control. X-ray diffraction, optical absorption and Raman spectroscopy, scanning electron microscopy with wave dispersive analysis, and transmission electron microscopy were used to characterize the starting Mo₆S₄I₆ nanowires and the MoS₂ nanotubes. The unit cell parameters of the Mo₆S₄I₆ phase are proposed. Blue shift in optical absorbance and metallic behavior of MoS₂ nanotubes in two-probe measurement are explained by a high defect concentration.     

Hydrothermal synthesis of Y3NbO7 nanowires for the photocatalytic degradation of omeprazole sodium

Novel Y₃NbO₇ nanowires were successfully synthesized by a facile hydrothermal method using Y(NO₃)₃·6H₂O and Nb₂O₅ as raw materials. X-ray power diffraction (XRD), High resolution transmission electron microscopy (HR-TEM), UV–vis diffuse reflectance spectroscopy (UV–vis-DRS), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) techniques were employed to determine the structure, morphology, specific surface area and optical properties of the as-prepared samples. Photocatalytic examination of the samples was carried out using aqueous solution of omeprazole sodium under visible light irradiation. The effects of initial omeprazole sodium concentration and catalyst amount on the photocatalytic degradation were also investigated. Detailed characterization demonstrated that Y₃NbO₇ nanowires have cubic fluorite crystal structure with a diameter of about 20 nm and a length up to several micrometers. Photocatalytic activity tests revealed that omeprazole sodium photocatalytic reactions followed pseudo-first-order kinetics and Y₃NbO₇ nanowires exhibited greater photocatalytic activity than its bulk counterparts.     

Yb2O3 nanowires,nanorods and nano-square plates

Developing a new morphology and revealing new physicochemical properties are very important steps in industrial applications. In this study, ytterbium oxide (Yb₂O₃) nanowires, nanorods and nano-square plates were first synthesized by a facial hydrothermal method and a post-thermal treatment, and characterized by X-ray diffraction crystallography, Fourier transform-infrared, UV–visible-NIR absorption, photoluminescence, and X-ray photoelectron spectroscopy. The morphology and the microstructures were examined by scanning electron microscopy and high resolution transmission electron microscopy. As-prepared samples with different morphologies showed different crystal phases but changed to the same cubic Yb₂O₃ phase upon thermal treatment. Eu(III) and Tb(III) activator ions were also doped into Yb₂O₃ host materials and discussed.     

Paramagnetic Ho2O3 nanowires,nano-square sheets,and nanoplates

The morphology control of holmium oxide (Ho₂O₃) nanostructures has rarely been reported. In the present study, uniform Ho₂O₃ nanowires, nano-square sheets, and nanoplates were synthesized via the hydrothermal method and were characterized using scanning electron microscopy, high-resolution transmission electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, ultraviolet–visible–near-infrared absorption, and X-ray photoelectron spectroscopy. The morphology was observed to be composed of different crystal phases and Ho complexes, but it changed to the same cubic Ho₂O₃ crystal phase upon high-temperature thermal treatment. Paramagnetic properties were obtained and discussed for the three different morphologies mentioned above. The newly reported morphologies and the physicochemical properties reported herein will widen the application scope of Ho oxide materials.     

Stress enhanced TiO2 nanowire growth on Ti–6Al–4V particles by thermal oxidation

Titanium dioxide (TiO₂) nanowires were grown on Ti - 6wt% Al - 4wt% V (Ti64) particles by thermal oxidation. To investigate the effect of stress on nanowire growth, the particles were milled in a planetary ball mill prior to the thermal oxidation. Thermal oxidation of the Ti64 particles was carried out in a horizontal tube furnace in a controlled oxygen atmosphere in the temperature range of 700–900 °C. The oxygen concentration was varied from 20 ppm to 80 ppm in Ar atmosphere. Nanostructures were characterized by high resolution field emission scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. TiO₂ nanowires grew on the surface of Ti64 particles and exhibited a square/rectangular cross sectional shape with thicknesses of 20–40 nm and lengths of 2–3 μm. Residual stress was found to play a significant role in nanowire growth. This was confirmed by growing TiO₂ nanowires on Ti64 alloy sheet with an induced stress gradient along its length. An improvement in nanowire coverage was observed in regions of high residual stress. A stress-induced growth mechanism is suggested to explain the confinement of nanowire growth to one dimension during thermal oxidation.     

Synthesis of CuInTe2 nanowires: A polycrystalline‐to‐single‐crystalline transformation process

A facile solvothermal synthetic route has been developed to prepare CuInTe₂ nanowires with the template aiding of anodic aluminum oxide. Microstructure analysis reveals that the as‐prepared single crystalline CuInTe₂ nanowires have a [112] direction preferential growth. Oriented attachment mechanism has been proposed to explain the anisotropic growth of CuInTe₂ nanowires during a polycrystalline‐to‐single‐crystalline transformation process. CuInTe₂ nanowires have strong absorption in the visible region based on UV‐Vis absorption spectra measurement, confirming its suitability as a light absorbing material in solar cells.     

Synthesis of sword-like CuSbS2 nanowires as an anode material for sodium-ion batteries

Sword-like CuSbS₂ nanowires with [001] preferential growth direction were prepared via a facile solvothermal chemical route. The sharp ends of the CuSbS₂ nanowires were induced by the rapid growth of (001) planes. We have investigated electrochemical performance of CuSbS₂ nanowires as an active material for anode in Na-ion batteries. CuSbS₂ nanowires electrode delivered an initial de-sodiation capacity of 520.5?mA?h/g at 30?mA/g and retained 286.7?mA?h/g after 50 cycles. A full cell based on CuSbS₂ anode and P2-Na_2/3Ni_1/3Mn_1/2Ti_1/6O₂ cathode was assembled and an energy density of 193?Wh/kg was obtained.     

Large-scale synthesis of hafnium carbide nanowires via a Ni-assisted polymer infiltration and pyrolysis

Hafnium carbide (HfC) nanowires were successfully synthesized on C/C composites via a Ni-assisted polymer infiltration and pyrolysis. Before synthesizing HfC nanowires, the composition and microstructure of the organic HfC precursor and its pyrolyzed products were characterized by Fourier transform infrared spectra, X-ray photoelectron spectroscopy, and X-ray diffraction. The effect of heat-treatment temperature on the morphology and microstructure of HfC nanowires were investigated by scanning electron microscopy and transmission electron microscopy. Results show that HfC nanowires exhibits three-layer core-shell structure, including HfC core, HfO₂ inner shell (~2 nm) and carbon nanosheet outer shell (~1 nm). The obtained HfC nanowire is typically grown along <01> with the diameters of ~100 nm and the length of several micrometers. The growth of HfC nanowire follows the combination of top-type vapor-liquid-solid and solid-liquid-solid mechanism.     

氧化亚铜纳米线的制备及其光电性能

摘要：通过电沉积法在阳极氧化铝模板中制备了Cu2O纳米线,利用X射线衍射(XRD)、扫描电子显微镜(SEM)对Cu2O纳米线的组成和形貌进行了表征,并测试了Cu2O/AAO阵列体系的光电压、交流阻抗性能。测试结果表明,制备的Cu2O纳米线的直径约120nm,长约2μm;Cu2O/AAO阵列体系在紫外灯(365nm)照射下,光电压约25mV, 阻抗值大大减小。     

A Novel Way for Synthesizing Phosphorus-Doped Zno Nanowires

We developed a novel approach to synthesize phosphorus (P)-doped ZnO nanowires by directly decomposing zinc phosphate powder. The samples were demonstrated to be P-doped ZnO nanowires by using scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction spectra, X-ray photoelectron spectroscopy, energy dispersive spectrum, Raman spectra and photoluminescence measurements. The chemical state of P was investigated by electron energy loss spectroscopy (EELS) analyses in individual ZnO nanowires. P was found to substitute at oxygen sites (P_O), with the presence of anti-site P on Zn sites (P_Zn). P-doped ZnO nanowires were high resistance and the related P-doping mechanism was discussed by combining EELS results with electrical measurements, structure characterization and photoluminescence measurements. Our method provides an efficient way of synthesizing P-doped ZnO nanowires and the results help to understand the P-doping mechanism.     

Tribological performances of Mo6S3I6 nanowires

A new nanowire-like material with the chemical formula Mo₆S₃I₆ was studied as an additive in a synthetic base oil, a polyalphaolefin (PAO). This material presents interesting friction reducing properties, friction coefficient reaching a value of 0.04 in boundary lubrication. Transmission and scanning electron microscopy, X-ray diffraction, and Raman spectroscopy were used to characterize nanowires before and after friction. The combination of these techniques gave evidence of MoS₂ formation in contact area during friction test. This structural evolution of nanowires explains their good friction reducing properties.     

Facile synthesis of single crystalline SnO2 nanowires

Single crystalline SnO₂ nanowires with diameter in the range of 10–100 nm and several micrometers in length have been successfully prepared by the combustion technique in air using Al, Cu₂O and SnO as the raw materials. FE–SEM and TEM images showed that the nanowires were single crystalline, growing along the [310] direction. The nanowires' growth mechanism was suggested to follow both VLS and VS mechanisms. The formation of SnO₂ nanowires underwent three steps: tin vapor generation via combustion synthesis, oxidation of the tin vapor and its nucleation and subsequent growth. At the same time, porous Al₂O₃ ceramic and Cu–Sn alloy were obtained during the combustion synthesis process.