Seedless growth of free-standing copper nanowires by chemical vapor deposition

Free-standing copper nanowires were synthesized by a chemical vapor deposition process at low substrate temperatures using Cu(etac)[P(OEt)3]2 as a precursor. The process requires neither templates nor catalysts to produce copper nanowires of 70-100 nm in diameter, which exhibited high purity and crystallinity with [111] orientation. The grain structures of the films deposited from a series of Cu(I) alkyl 3-oxobutanoate complexes indicated that the high precursor stability was responsible for the columnar growth of the grains, which was evolved to the nanowires eventually.     

Copper nanowire arrays surface wettability control using atomic layer deposition of TiO<Subscript>2</Subscript>

Template two step electrodeposition method and atomic layer deposition were used to synthesize copper nanowires of varied length (1.2 to 26.2 μm) and copper nanowires coated with titanium dioxide. As a result of the atomic layer deposition of TiO₂, coated nanowires demonstrated an up to 10-fold decrease in the wetting angle, compared with uncoated nanowires. It was found the dissipation rate is substantially higher for nanowires coated by the atomic layer deposition method (100 s) as compared with the uncoated copper nanowires (400 s), which assumes the positive properties of water propagation along the surface, necessary for improving the heat transfer. It was also found that the water contact angle for uncoated nanowires and those coated with TiO₂ by the atomic layer deposition (ALD) gradually increases as the samples are kept in air. A gradual increase in wettability was also observed for smooth silicon wafers coated by ALD of TiO₂, which were exposed to air. On the coated silicon substrates, the wetting angle gradually increased from 10° to approximately 56° in the course of four days. In addition, it was shown that copper nanowires coated with TiO₂ by the atomic layer deposition method have an excellent corrosion resistance, compared with uncoated nanowires, when brought in contact with air and water.     

A vapor-solid strategy to silica sheathed metal nanostructures and microstructures via reactions of metal chlorides with silicon

A facile vapor-solid strategy has been developed to prepare silica-sheathed metal micro/nanostructures with controllable shapes. As examples, silica-sheathed nickel nanowires (diameter approximately 50 nm), microcubes (edge length 1-3 microm), nanocubes (edge length approximately 200 nm) with an epitaxial tail (diameter<100 nm), and 1D assembly structures of nanoparticles (particle diameter<100 nm) as well as silica-sheathed cobalt and copper micro/nanostructures are synthesized. The possible reaction and growth mechanisms of Ni/SiO2 structures are discussed. The method is expected to be applied to a wider range of metals.     

Molten gallium as a catalyst for the large-scale growth of highly aligned silica nanowires

The vapor-liquid-solid (VLS) process is a fundamental mechanism for the growth of nanowires, in which a small size (5-100 nm in diameter), high melting point metal (such as gold and iron) catalyst particle directs the nanowire's growth direction and defines the diameter of the crystalline nanowire. In this article, we show that the large size (5-50 microm in diameter), low melting point gallium droplets can be used as an effective catalyst for the large-scale growth of highly aligned, closely packed silica nanowire bunches. Unlike any previously observed results using gold or iron as catalyst, the gallium-catalyzed VLS growth exhibits many amazing growth phenomena. The silica nanowires tend to grow batch by batch. For each batch, numerous nanowires simultaneously nucleate, grow at nearly the same rate and direction, and simultaneously stop growing. The force between the batches periodically lifts the gallium catalyst upward, forming two different kinds of products on a silicon wafer and alumina substrate. On the silicon wafer, carrot-shaped tubes whose walls are composed of highly aligned silica nanowires with diameters of 15-30 nm and length of 10-40 microm were obtained. On the alumina substrate, cometlike structures composed of highly oriented silica nanowires with diameters of 50-100 nm and length of 10-50 microm were formed. A growth model was proposed. The experimental results expand the VLS mechanism to a broader range.     

铜纳米线的液相制备及其表面修饰研究进展

在现代纳米科学技术领域中,铜纳米线由于具有独特的光学、电学、力学和热学性质而成为制备透明柔性导电电极的优良材料。铜价格低廉,自然存储量较大,是实际应用中替代贵金属的理想材料。然而,将铜离子还原为单质铜比较困难,且单质铜非常容易被氧化,这成为应用中亟需解决的关键问题。如何制备单分散、稳定且具有抗氧化性的铜纳米线也成为该领域的研究热点。在各种制备铜纳米线的方法中,液相还原法不仅可以解决以上问题,且该方法具有制备条件限制少、成本低、简单易行等优点而被广泛应用于铜纳米线的大量合成。本文从铜纳米线的研究背景和研究价值入手,首先综述了不同（光滑或粗糙、单晶或孪晶）铜纳米线的液相制备方法及其生长机制。讨论了铜纳米线的氧化及其抗氧化表面包覆问题。最后对铜纳米线的研究意义和应用前景做出展望。     

Uniform Nanowires Containing a Heterogeneousπ-Conjugated Core of Controlled Length,Composition and Morphology

In this work, it is demonstrated for the first time that heterojunction nanowires, consisting of a gradient and segmented-like heterogeneous π-conjugated core with controllable length, composition and morphology, can be generated by co-self-seeding of oligo(p-phenylene vinylene) (OPV)- and oligo(p-phenylene ethynylene) (OPE)-containing block copolymers in spite of different chain lengths and molecular conformation for OPE and OPV. More importantly, based on the understanding of the formation of heterogeneous core by the co-self-seeding approach, a “heating/cooling” seeded growth route was developed, by which linear and branched heterojunction nanowires containing a segmented heterogeneous π-conjugated core of controlled length, composition and morphology can be obtained. This work provides a versatile platform to generate heterojunction nanowires with excellent controllability in length, composition, and morphology.     

Aqueous‐Phase Synthesis of Size‐Tunable Copper Nanocubes for Efficient Aryl Alkyne Hydroboration

Copper nanocubes with average sizes of 82, 95, and 108 nm have been synthesized in an aqueous mixture of cetyltrimethylammonium chloride (CTAC) surfactant, copper acetate, and sodium ascorbate reductant heated at 100 °C for 40 min. Copper nanowires with an average length of 25 μm can also be prepared this way by simply increasing the volume of sodium ascorbate introduced. Small shifts in the plasmonic absorption band positions with tunable particle sizes have been observed. The copper nanocubes were employed to catalyze hydroboration of phenylacetylene and various substituted aryl alkynes with 100 % (E )‐product selectivity and 82–95 % product yields. The copper nanocubes are cheap to make and should catalyze a broad scope of organic coupling reactions.     

Effect of O5+ ion implantation on the electrical and structural properties of Cu nanowires

Ion beam creates changes in the material along their track, not only embody the excellent properties but also tailor new materials. When the ions are implanted into the nanomaterials, they collide with the target atoms and interact through three different phenomena; electron collision, nuclear collision and charge exchange. In the present study, 1 MeV O⁵⁺ ions were implanted in copper nanowires of diameter 80 nm synthesized using template synthesis approach. Electrical and structural properties were recorded using Keithley 2400 series source meter and Rigaku X-ray diffractometer respectively, before and after the implantation. I–V characteristics showed the ohmic behavior with enhancement in conductivity of copper nanowires after implantation. No structural damage in the nanowires was revealed by XRD spectra. The work done can be viewed as a positive aspect of implantation in metallic nanowires especially in 80 nm diameter Cu nanowires and may be utilized to fabricate nanodevices.     

Disproportionation for growing copper nanowires and their controlled self-assembly facilitated by ligand exchange

The coating makes the wire bundle: High-quality free-standing copper nanowires have been successfully produced by disproportionation of Cu(+) in oleylamine. This provides an effective way to prepare high-quality copper nanowires, but also enriches synthetic routes to other nanostructures. These copper nanowires can self-assemble by surface ligand exchange of oleylamine with trioctylphosphine.     

One-step preparation of porous copper nanowires electrode for highly sensitive and stable amperometric detection of glyphosate

A simple and sensitive amperometric method for the detection of glyphosate based on a porous copper nanowire electrode is presented. The porous nanowires were fabricated simply by a one-step electrodeposition using hydrogen bubbles generated during the deposition to produce pores. These porous nanowires provided a 1.4 times larger surface area than a porous copper film. After the fabrication process the porous copper nanowires can be applied directly as a working electrode with the same custom-built flow cell. The detection was carried out by measuring the oxidation signal of copper; this increased with the concentration of glyphosate due to dissolution of the copper from the electrode. Under optimal conditions, the responses of the sensor were linear between 0.010–5.0 µmiol L^?1, with a limit of detection of 10.0 nmol L^?1 (S/N = 3). The large surface area of the electrode minimised the corrosion effect, as observed by the remarkably stable response (95 injections of 0.20 µmol L^?1 of glyphosate were possible). When applied in order to detect glyphosate in fresh fruit and vegetable samples, the concentrations were found in the range of non-detectable to (0.104 ± 0.005) µmiol L^?1. These results indicated that the fabrication process can be used to produce a new form of working electrode for glyphosate detection.     

低温湿化学法可控制备一维Te纳米线/棒

采用低温湿化学法制备了形貌可调的Te纳米线/棒. 考察了反应温度和还原剂滴加速率对产物的物相和微观结构的影响规律. 研究结果表明, 随着反应温度的升高, Te纳米线的长度逐渐变小, 直径逐渐增大; 随着还原剂滴加速率减慢, 产物Te纳米线长度增加, 直径增大. 通过考察不同反应阶段产物的形貌和结构, 可推测Te纳米线/棒的生长模式为: 反应初期, 溶解在乙二醇内的TeO₂被还原为亚稳态的活性α-Te和稳态的τ-Te, 随着反应的进行, 亚稳态的活性α-Te将重新溶解, 并被还原为稳态的τ-Te析出. τ-Te沿[001]方向轴向生长的特性应归因于其晶体的各向异性.     

Synthesis and Characterization of Iron Nanowires

The iron nanowires can be fabricated via the process in which sodium borohydride reduces iron salts in external magnetic field. The iron nanowires are found to be covered by passivated layers of iron oxide which prevent the oxidation of iron nanowires. In this process, the boron will include in iron nanowires. The average length and diameter of iron nanowires is around 1.2 micrometers and 60 nanometers, respectively. According to ICP results, the contents of B and Fe are about 1.98 wt% and 87.04 wt%, respectively, in iron nanowires. A wide variety of equipment is used to investigate the morphological, microchemical, and structural characteristics of the newly synthesized iron nanowires ––– e.g., XRD, FE‐SEM, HR‐TEM, VSM and XANES. XANES analysis indicates the boron in iron nanowires exists in the form of B₂O₃. The saturation magnetization and the coercive force of iron nanowires are 157.93 emu/g and 9.74 Oe, respectively. In‐situ images of synthesized iron nanowires during reduction process in magnetic field are observed by NSRRC transmission X‐ray microscope. Thus, this study develop a novel process to produce iron nanowires with large quantitates and can control its length and diameter by various the concentration of precursors for various applications.     

Size controlled growth of germanium nanorods and nanowires by solution pyrolysis directly on a substrate

Herein, we describe the controlled growth of 1 dimensional germanium nanostructures from high aspect ratio nanowires (>10 microns in length) to shorter aspect nanorods (100 nm in length) via a simple pyrolysis method. The synthetic route involves the thermal decomposition of selected germanium precursors by dropping a solution in a high boiling point solvent directly onto a pre-heated Si wafer in the presence of a copper source under inert conditions.     

A simple approach to the synthesis of silver nanowires by hydrothermal process in the presence of gemini surfactant

Silver nanowires were synthesized by the hydrothermal route in aqueous solution of gemini surfactant 1,3-bis(cetyldimethylammonium) propane dibromide (16-3-16) at a relatively low temperature. The as-prepared silver nanowires were characterized by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), transmission electron microscope (TEM), electron diffraction (ED), and UV-vis absorption spectrum. The obtained silver nanowires are of high aspect ratios with an average diameter of approximately 30 nm and length ranging from several to tens of micrometers.     

Controllable Synthesis and Study on Morphology of Copper Nanowires

High‐purity, large‐aspect‐ratio, and well‐dispersed copper nanowires (CuNWs) with an average diameter of 45 nm and length >100 μm were successfully synthesized by reducing a Cu(II) salt with glucose, with oleylamine (OM) and oleic acid (OA) serving as dual capping agents, through hydrothermal reduction. A systematic study of the effects of the copper salt, capping agents, reductant, and temperature on the morphology of CuNWs has been conducted. Our results indicate that CuNWs with different diameters can be obtained using different copper salts. The diameter of the as‐prepared CuNWs decreases with increasing amounts of OM/OA and glucose but increases with the increasing temperature of the reaction. By adjusting the experimental parameters, we could achieve controlled synthesis of CuNWs and obtain high‐quality CuNWs with different diameters of 45, 76, 85, 90, 100, 112, 135, and 175 nm.     

High-quality luminescent tellurium nanowires of several nanometers in diameter and high aspect ratio synthesized by a poly (vinyl pyrrolidone)-assisted hydrothermal process

Large-scale selective synthesis of uniform single crystalline tellurium nanowires with a diameter of 4-9 nm, and microbelts with a width of 250-800 nm and tens of micrometers in length, can be realized by a poly (vinyl pyrrolidone) (PVP)-assisted hydrothermal process. The formation of tellurium nanowires and nanobelts in the presence of PVP is strongly dependent on the reaction conditions such as temperature, the amount of PVP, and reaction time. The results demonstrated that the keys for selective synthesis of Te nanobelts and nanowires are to modulate the growth rates of (100), (101), and (110) planes in the presence of PVP and to precisely control the reaction kinetics. High-quality luminescent ultrathin t-Te nanowires with a diameter of 4-9 nm display strong luminescent emission in the blue-violet region. This approach provides a facile route for the production of high-quality tellurium nanostructures with an interesting optical property. Furthermore, the synthesized ultrathin nanowires with deep blue color and nanobelts in gray color by this approach can be well dispersed in water or ethanol, making it possible for further engineering of their surfaces to prepare other hybrid core-shell nanostructures.     

Length-controlled synthesis of oriented single-crystal rutile TiO2 nanowire arrays

A free-standing, large area, oriented single-crystal rutile TiO(2) nanowire arrays with a controlled length in the range of 10-80 μm are prepared via a facile one-step synthesis. The growth process is studied systematically in an appropriate amount of H(2)O(2) and HCl solution under hydrothermal conditions. The length of the nanowires can be easily tuned by varying the experimental parameters, including reaction temperature and reaction time. High-resolution transmission electron microscopy demonstrated that the nanowires have single-crystal structure. Furthermore, the photoluminescence characteristics and photocatalytic properties of oriented single-crystal rutile TiO(2) nanowires was discussed in this paper, respectively. It is found that the increased reaction temperature is helpful to photocatalytic reactivity and photoluminescence properties.     

Molecular Template Assisted Growth of Ultrathin Silicon Carbide Nanowires with Strong Green Light Emission and Excellent Field‐Emission Properties

A novel molecule template assisted chemical co‐reduction method has been successfully developed for the controlled synthesis of ultrathin β‐SiC single‐crystalline nanowires on a large scale. The ultrathin β‐SiC single‐crystalline nanowires are about 8 nm in diameter and 200–800 nm in length. The resulting thin β‐SiC single‐crystalline nanowire is new in the family of β‐SiC one‐dimensional (1D) nanostructures. A synergistic action of π‐stacking and steric hindrance result from the 1,10‐phenanthroline molecule template are proposed to explain the growth mechanism of the ultrathin β‐SiC single‐crystalline nanowires based on the experimental observation. Importantly, such ultrathin β‐SiC nanowire has shown a strong structure‐induced enhancement of photoluminescence properties and has exhibited a very strong green light emission, which can be seen by naked eye. Furthermore, the unique β‐SiC ultrathin nanowire structure exhibits a low turn‐on field (3.57 V μm^?1) and a large field‐emission current density (20 mA cm^?2). These results suggest that the ultrathin β‐SiC nanowires can be expected to find promising applications as field emitters and photoelectronic devices.     

Synthesis of organic-metal hybrid nanowires by cooperative self-organization of tetrathiafulvalene and metallic gold via charge-transfer

Organic-metal hybrid nanowires were synthesized by cooperative self-organization of the one-dimensional stacking of tetrathiafulvalene (TTF) via charge-transfer interaction with metallic gold originating from the redox reaction between TTF and gold ions. The nanowires can be easily obtained as purple precipitates just by mixing TTF and HAuCl4 in a CH3CN solution at room temperature. The feed molar ratio of TTF to HAuCl4 was 4.4. The average diameter and length of the observed nanowires were 90 +/- 36 nm and 15 +/- 3 microm, respectively. The formation was facilitated by the arrangement of the neutral and oxidized TTF along the one direction in a mix-valence state, which was confirmed by a broad absorption that appeared in the region of 2000 nm and the composition of the nanowires of [(TTFCl(0.78))Au(0.12)].     

Synthesis of sub-20-nm-sized bismuth 1-D structures using gallium-bismuth systems

Bismuth (Bi) nanowires are interesting one-dimensional systems due to the significant quantum confinement effects exhibited as a function of the wire diameters, and synthesizing Bi nanowires with sizes below 20 nm is of fundamental importance in understanding quantum effects. Here, we report a bulk synthesis method to synthesize ultrafine Bi nanowires and a new morphology of bismuth nanostructures, tapered whiskers. These tapered whiskers are about 10-20 mum in length and have diameters of 5-10 nm at the tip and 250-500 nm at the base. The synthesis method is based upon the multiple nucleation and basal growth of nanometer scale nuclei from molten gallium (Ga) melts that result from the low solubility of Bi in Ga and the low eutectic temperature of the Ga-Bi binary system. Adopting different methods of supplying bismuth and using variations in simple heating and cooling, we have synthesized a variety of bismuth nanostructures.