Phase-controlled one-dimensional shape evolution of InSe nanocrystals

Cubic-phase InSe nanowires were synthesized. Obtaining an appropriate high reaction temperature for formation of nanocrystals using poor solubility of Se powder in oleylamine induced the generation of unusual cubic phase of InSe to form nanowires. In comparison, hexagonal-phase nanoplates were formed by dissolving Se powder in oleylamine before increase of reaction temperature. The diameter of highly monodisperse wires was controlled by varying the amount of Se.     

Ultrathin Au nanowires and their transport properties

This paper presents a facile synthesis of single-crystalline Au nanowires by reduction of HAuCl4 in oleic acid and oleylamine. The diameter of these micron-meter-long Au nanowires is controlled to be 3 and 9 nm by volume ratio of oleylamine and oleic acid. When linked between two gold electrodes, the 9 nm Au nanowire shows good electron conductivity with its breakdown current density reaching 3.5 x 10(12) A/m2. This demonstrates that the chemically made ultrathin Au nanowires can be used as a molecular-scale interconnect for nanoelectronic applications.     

The role of oxidative etching in the synthesis of ultrathin single-crystalline Au nanowires

The fabrication of ultrathin single-crystal Au nanowires with high aspect ratio and that are stable in air is challenging. Recently, a simple wet-chemical approach using oleylamine has been reported for the synthesis of Au nanowires with micrometer length and 2 nm in diameter. Despite efforts to understand the mechanism of the reaction, an ultimate question about the role of oxygen (O(2)) during the synthesis remained unclear. Here we report that the synthesis of ultrathin Au nanowires employing oleylamine is strongly affected by the amount of O(2) absorbed in the reaction solution. Saturating the solution with O(2) leads to both a high-yield production of nanowires and an increase in their length. Nanowires with diameters of about 2 nm and lengths of 8 μm, which corresponds to an aspect ratio of approximately 4000, were produced. The role of oxygen is attributed to the enhanced oxidation of twin defects on Au nanoparticles formed in the first stage of the reaction. Understanding the role of oxidative etching is crucial to significantly increasing the yield and the length of ultrathin Au nanowires.     

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.     

一步湿化学法合成超细金纳米线

以氯金酸(HAuCl₄)为前驱物, 油胺同时作为溶剂、表面稳定剂和还原剂, 通过简单的一步湿化学法合成超细金纳米线. 制备出的超细金纳米线不仅产量高、纯度高, 而且纵横比大, 纳米线平均直径~2 nm, 长度可达数十微米. 如果添加另一种还原剂油酸并调节油胺和油酸的体积比为1:1, 将生成直径为~9 nm的金纳米线. 通过改变反应温度和还原剂用量, 对该种超细金纳米结构的生长机制进行阐述说明: 以油胺为模板, 在油胺和一价金卤化物(AuCl)亲金键合形成的一维聚合链作用下, 被还原的金原子附着在已成核颗粒表面, 一维地生长成超细金纳米线.     

Solution synthesis of germanium nanowires using a Ge2+ alkoxide precursor

A simple solution synthesis of germanium (Ge0) nanowires under mild conditions (<400 degrees C and 1 atm) was demonstrated using germanium 2,6-dibutylphenoxide, Ge(DBP)2 (1), as the precursor where DBP = 2,6-OC6H3(C(CH3)3)2. Compound 1, synthesized from Ge(NR2)2 where R = SiMe3 and 2 equiv of DBP-H, was characterized as a mononuclear species by single-crystal X-ray diffraction. Dissolution of 1 in oleylamine, followed by rapid injection into a 1-octadecene solution heated to 300 degrees C under an atmosphere of Ar, led to the formation of Ge0 nanowires. The Ge0 nanowires were characterized by transmission electron microscopy (TEM), X-ray diffraction analysis, and Fourier transform infrared spectroscopy. These characterizations revealed that the nanowires are single crystalline in the cubic phase and coated with oleylamine surfactant. We also observed that the nanowire length (0.1-10 microm) increases with increasing temperature (285-315 degrees C) and time (5-60 min). Two growth mechanisms are proposed based on the TEM images intermittently taken during the growth process as a function of time: (1) self-seeding mechanism where one of two overlapping nanowires serves as a seed, while the other continues to grow as a wire; and (2) self-assembly mechanism where an aggregate of small rods (<50 nm in diameter) recrystallizes on the tip of a longer wire, extending its length.     

Ultrathin gold nanowires can be obtained by reducing polymeric strands of oleylamine-AuCl complexes formed via aurophilic interaction

This Communication describes a facile route to the preparation of ultrathin gold nanowires using linear chains formed from [(oleylamine)AuCl] complex via aurophilic interaction. The linear chains, with AuI...AuI bonds as the backbone and surrounded by oleylamines, can group together to form bundles of polymeric strands. When the AuI was reduced to Au0 by reacting with Ag nanoparticles in hexane, the polymeric strands functioned as both the source of Au and the template to mediate the nucleation and growth of Au nanowires. Using this method, we were able to produce Au nanowires with an average diameter of approximately 1.8 nm and an aspect ratio of >1000 in high yields (approximately 70%).     

Catalytic epoxidation of stilbene with FePt@Cu nanowires and molecular oxygen

A novel FePt@Cu nanowire catalyst was prepared by the reduction of Cu(acac)(2) on the surface of FePt nanowires, in oleylamine (OAm). This nanowire catalyst efficiently epoxidised stilbene in the presence of molecular oxygen, and the conversion and selectivity were maintained with repeated use of the catalyst, compared with recycled catalyst.     

Ternary cobalt-iron phosphide nanocrystals with controlled compositions, properties, and morphologies from nanorods and nanorice to split nanostructures

Structural phase-controlled formation of binary Co(2)P and CoP nanocrystals is achieved by reacting cobalt(II) oleate with trioctylphosphine. In the absence of oleylamine, Co(2)P nanowires are formed at both 290 and 320 °C. In the presence of oleylamine, Co(2)P nanorods are formed at 290 °C, and CoP nanorods are formed at 320 °C. With the simultaneous reaction of iron(III) oleate and cobalt(II) oleate with trioctylphosphine in the presence of oleylamine, ternary Co(2)P-type cobalt-iron phosphide nanostructures are produced at both 290 and 320 °C, corresponding to rice-shaped Co(1.5)Fe(0.5)P nanorods and split Co(1.7)Fe(0.3)P nanostructures, respectively. The controlled incorporation of iron into cobalt phosphide can alter the magnetic properties from paramagnetic binary Co(2)P to ferromagnetic Co(2)P-type ternary cobalt-iron phosphide nanostructures. Meanwhile, the time-dependent morphological evolution from small nanodots/nanorods, through seeded growth to unique split nanostructures is demonstrated in one-pot reaction at 320 °C.     

Co‐doped Pt Nanowire Networks with Clean Surfaces for Enhanced Oxygen Reduction Reactions

Surfactants or capping agents are usually employed to control the shapes and sizes of metal nanowires (NWs). Polyvinylpyrrolidone (PVP) and oleylamine (OAm) are the most common capping agents used in the synthesis of metal nanowires. However, these capping agents bind strongly onto the surface of the nanowires and severely prevent the reactant molecules from entering the active sites. In the present research, a facile acetic acid/NaBH₄ treatment technology is reported to effectively remove PVP and OAm from the surface of the co‐doped Pt NWs. Interestingly, the morphology of poor crystalline platinum nanowires treated with NaBH₄ solution is transformed into nanowire networks (NWNs) with higher crystallinity. Furthermore, in comparison with the commercial Pt/C catalyst, the catalytic activity of co‐doped Pt NWNs with clean surfaces shows improvements of up to 4.1 times for mass activity and 5.1 times for specific activity, respectively.     

Au Nanowires-MWCNTs修饰电极对葡萄糖的催化氧化

通过油胺(Oleylamine)还原法制备了金纳米线(Au nanowires),将其与酸化处理的多壁碳纳米管(MWCNTs)通过层层组装制备了Au nanowires-MWCNTs复合结构修饰的玻碳电极(Au nanowires-MWCNTs/GCE).电化学研究结果表明,与单纯Au nanowires或MWCNTs修饰电极相比,Au nanowires-MWCNTs/GCE对葡萄糖表现出更优良的电催化性能.以Au nanowires-MWCNTs/GCE为阳极,电沉积Pt膜电极(Pt/GCE)为阴极,构建了葡萄糖/O2燃料电池.测试结果表明,构建的燃料电池的开路电位(OCP)为0.57 V,在0.44 V下最大功率密度(Pmax)为0.28 m W/cm2.     

Synthesis of oleylamine capped copper nanocrystals via thermal reduction of a new precursor

The present investigation reports the novel synthesis of copper nanocrystals using thermal reduction, and their physicochemical characterization. The copper nanocrystal powder has been prepared using [bis(2-hydroxyacetophenato)copper(II)] as a precursor. The effect of oleylamine and triphenylphosphine on the particle morphology has been investigated. Transmission electron microscopy (TEM) analysis has demonstrated that the copper nanocrystals have an average diameter of about 3 nm. The as-prepared copper nanocrystals were characterized by XRD, SEM, TEM, EDX, UV–Vis and FTIR.     

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.     

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。     

基于AuCl(油胺)复合物合成形貌可控的金纳米结构

简要综述了使用一价金复合物AuCl(油胺)作为前驱物合成形貌可控的金纳米结构的相关工作. 通过改变有机溶剂、添加异质金属纳米粒子及控制反应温度等手段, 成功合成出球形的金纳米粒子(平均直径12.7 nm)、超细金纳米线(平均直径1.8 nm)及超细金纳米棒(平均直径2 nm); 并通过牺牲磁性纳米粒子模板的方法合成出枝状金纳米结构. 除了对合成方法和过程的介绍, 还简要讨论了每种纳米结构的形成机制.     

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.     

Vertically Aligned CuO Nanowires Based Electrode for Amperometric Detection of Hydrogen Peroxide

Vertically aligned copper oxide (CuO) nanowires were synthesized by directly heating copper foil on a hotplate under ambient conditions. The as‐grown CuO nanowires film is mechanically stable and was facilely attached to a glassy carbon (GC) electrode, offering an excellent electrochemical sensing platform. The CuO nanowires electrode shows excellent electrocatalytic response to H₂O₂ with significantly lower overpotentials for its oxidation and reduction and also exhibits a fast response and high sensitivity for the amperometric detection of H₂O₂. The novel vertically aligned CuO nanowires electrode is readily applicable to other analytes and has great potential applications in the electrochemical detection.     

Preparation and characterization of copper/silver bimetallic nanowires with core‐shell structure

Core‐shell copper/silver bimetallic nanowires were prepared by replacement reaction with citric acid and polyvinylpyrollidone at room temperature. A uniform silver coating was obtained by strictly controlling the molar ratio of Ag/Cu. The copper/silver composite was characterized by X‐ray diffraction, scanning electron microscopy, electron probe microanalysis and X‐ray photoelectron spectroscopy. Microscopic analysis shows that a well‐copper/silver core‐shell structure was formed. Thermo‐gravimetry and differential thermal analysis to the composite nanowires show that the silver coatings efficiently inhibit the oxidation of Cu. Copyright © 2015 John Wiley & Sons, Ltd.     

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.     

Field emission properties of large-area nanowires of organic charge-transfer complexes

In this contribution, large-area organic charge-transfer complex (AgTCNQ and CuTCNQ) nanowires were synthesized by organic vapor-solid-phase reaction at mild experimental conditions. These nanowires were facilitated on the surface of Cu and Ag foils or different kinds of substrates coated with a layer of silver and copper on a large scale. The excellent field emission properties were observed in the as-grown AgTCNQ and CuTCNQ nanowires. They should have great potential in vacuum device applications.