Large-scale synthesis of silver nanowires and platinum nanotubes

Silver nanowires have been synthesized by ethylene glycol reduction of silver nitrate with the assistance of polyvinyl pyrrolidone and sodium sulfide in a large scale. By adjusting the reaction temperature and Na₂S content, silver nanowires with lengths up to 3?4 μm can be achieved in high yield. Scanning electron microscopy, transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected areas electron diffraction (SAED), and X-ray diffraction (XRD) have been employed to characterize silver nanowires. Platinum nanotubes with length about 3 μm can be prepared using as-prepared silver nanowires as sacrificial templates. Platinum nanotubes were characterized by TEM, SAED, and HRTEM.     

Self-catalyst growth of single-crystalline CaB6 nanostructures

Large-scale calcium hexaboride (CaB₆) nanostructures have been successfully fabricated with self-catalyst method using calcium (Ca) powders and boron trichloride (BCl₃) gas mixed with hydrogen and argon. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected-area electron diffraction (SAED) were used to characterize the compositions, morphologies, and structures of the samples. Our results show that the nanowires are highly single crystals elongated preferentially in the [1 1 0] direction. The growth mechanism based on the self-catalyst process is simply discussed.     

Solvothermal synthesis and characterization of uniform CdS nanowires in high yield

Large-scale CdS nanowires with uniform diameter and high aspect ratios were synthesized using a simple solvothermal route that employed CdCl₂ and S powder as starting materials, ethylenediamine (en) as the solvent. X-ray diffraction (XRD) pattern and transmission electron microscopy (TEM) images show that the products are hexagonal structure CdS nanowires with diameter of 40 nm and length up to 10 μm. Selected area electron diffraction (SAED) and high resolution TEM (HRTEM) studies indicate the single-crystalline nature of CdS nanowires with an oriented growth along the c-axis direction. The optical properties of the products were characterized by optical absorption spectra and photoluminescence spectra. Based on the results of contrastive experiments, it is found that the sulfur source and the solvent play significant roles in the formation of uniform nanowires. A possible formation mechanism of nanowires is discussed.     

One-step template-free solution route for Cu(OH)<Subscript>2</Subscript> nanowires

Cu(OH)₂ nanowires with a diameter of 8–10 nm and lengths of tens of micrometers were fabricated in the basic solution by dropping simply NaOH solution into CuCl₂ solution at ambient temperature. The formation mechanism of nanowires was discussed. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were used to characterize the samples. This article was submitted by the authors in English.     

A simple wet chemical route for large-scale synthesis of Cu(OH)2 nanowires

Polycrystalline Cu(OH)₂ nanowires with an average diameter of ca. 8 nm and lengths of up to hundreds of micrometers were synthesized by using a simple chemical route at ambient temperature. The crystallity, purity, morphology, and structure features of the as-prepared Cu(OH)₂ nanowires were investigated by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). The growth mechanism of the Cu(OH)₂ nanowires were studied in detail.     

Construction of strong alkaline hydrothermal environment for synthesis of copper telluride nanowires

Strong alkaline hydrothermal environment was constructed through adjusting the KOH concentration in solution for the synthesis of Cu_2−xTe nanocrystals. The Cu_2−xTe nanowires were successfully obtained by hydrothermal method without using any template or capping agent. The as-synthesized nanowires were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM). The Cu_2−xTe nanowires with lengths up to hundreds of micrometers have a single crystal hexagonal structure and grow along the [11], [12], [13], [14], [15], [16], [17], [18] , [19] and [20] direction. A growth mechanism was proposed based on the characterization results. The energy gap of as-synthesized Cu_2−xTe nanowires is ca.1.1 eV for direct band transition or 0.7 eV for indirect band transition. The structural phase transformations occur at 322, 353 and 477 °C. And the Cu_2−xTe nanowires exhibit the metal electrical conductivity.     

Hydrothermal synthesis and characterization of hexagonal and monoclinic neodymium orthophosphate single-crystal nanowires

Hexagonal and monoclinic NdPO₄ nanowires about 5-50 nm in diameter and up to several micrometers long were prepared through hydrothermal reaction in 100°C and 220°C, respectively. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), and high-resolution transmission electron microscopy (HRTEM). Furthermore, both the temperature and the pH value influence on the products were investigated.     

Template induced sol-gel synthesis of highly ordered LaNiO3 nanowires

The highly ordered LaNiO₃ nanowires of the rare-earth perovskite-type composite oxide were controlled synthesized within a porous anodic aluminum oxide (AAO) template by means of sol-gel method using nitrate as raw materials and citric acid as chelating agent. The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that the obtained LaNiO₃ nanowires had a uniform length and diameter, which were determined by the thickness and the pore diameter of the applied AAO template. The results of X-ray diffraction (XRD) and the selected-area electron diffraction (SAED) indicated that the LaNiO₃ nanowires were perovskite-type crystalline structures. Furthermore, X-ray photoelectron spectroscopy (XPS) and the energy dispersive X-ray (EDX) spectroscopy demonstrated that the stoichiometric LaNiO₃ was formed.     

Simple synthesis of ultra-long Ag2Te nanowires through solvothermal co-reduction method

Ultra-long single crystal β-Ag₂Te nanowires with the diameter of about 300 nm were fabricated through a solvothermal route in ethylene glycol (EG) system without any template. The long single crystal wires were curves, with high purity, well-crystallized, and dislocation-free and characterized by using X-ray powder diffraction (XRD), Differential scanning calorimetry (DSC) analysis, X-ray photoelectron spectroscope (XPS), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and high-resolution transmission microscopy (HRTEM). The detailed topotactic transformation process from particles into single crystal wires was studied. Furthermore, the electrical conductivity and Seebeck coefficient have been systematically studied between 300 and 600 K.     

A simple method of fabricating large-area α-MnO2 nanowires and nanorods

α-MnO₂ nanowires or nanorods have been selectively synthesized via the hydrothermal method in nitric acid condition. The α-MnO₂ nanowires hold with average diameter of 50 nm and lengths ranging between 10 and 40 μm, using MnSO₄·H₂O as manganese source; meanwhile, α-MnO₂ bifurcate nanorods with average diameter of 100 nm were obtained by adopting MnCO₃ as starting material. The morphology of α-MnO₂ bifurcate nanorods is the first one to be reported in this paper. X-ray powder diffraction (XRD), field scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) were used to characterize the products. Experimental results indicate that the concentrated nitric acid plays a crucial role in the phase purity and morphologies of the products. The possible formation mechanism of α-MnO₂ nanowires and nanorods has been discussed.     

Densely packed single-crystal Bi2Fe4O9 nanowires fabricated from a template-induced sol-gel route

Densely packed single-crystal Bi₂Fe₄O₉ nanowires were successfully synthesized by a template-induced citrate-based sol-gel process. The structural properties of the nanowires were characterized using many techniques. The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that Bi₂Fe₄O₉ nanowires possessed a uniform length and diameter, which were controlled by the thickness and the pore diameter of the applied porous anodic aluminum oxide (AAO) template, respectively. The results of X-ray diffraction (XRD) and the selected area electron diffraction (SAED) indicated that Bi₂Fe₄O₉ nanowires had an orthorhombic single-crystal structure. Furthermore, the energy-dispersive X-ray (EDX) spectroscopy demonstrated that the stoichiometric Bi₂Fe₄O₉ was formed. The possible formation mechanism of nanowires was also discussed.     

一维CdTe@C@TiO2-Au异质结纳米线的制备及其光催化性能

先利用一步水热法制备了具有核壳结构的CdTe@C纳米线,然后以钛酸异丙酯（TIP）作为钛源对CdTe@C纳米线进行二氧化钛包覆,最后通过原位还原HAuCl4的方法将Au纳米粒子组装到CdTe@C@TiO₂表面形成CdTe@C@TiO₂-Au一维异质结纳米复合材料。用扫描电镜（SEM）,X射线能谱（EDX）,透射电镜（TEM）,X射线衍射（XRD）,X射线光电子能谱（XPS）和紫外-可见漫反射光谱（UV-Vis DRS）等对材料进行表征。探究了CdTe@C@TiO₂-Au催化剂在模拟可见光下降解罗丹明B（RhB）的光催化性能。实验结果表明：不同催化剂对RhB的光降解率不一样,其效果依次为CdTe@C@TiO₂-Au > CdTe@C@TiO₂ > pure TiO₂,其中CdTe@C@TiO₂-Au能在270 min的模拟太阳光下对RhB的光降解率达95.3%,这主要得益于CdTe、碳层、TiO₂和具有表面等离子效应的纳米Au的共同作用。     

Synthesis of ordered Al nanowire arrays

Ordered Al nanowire arrays with the same nanowire density but the diameters decrease radially embedded in one piece of anodic alumina membranes were successfully fabricated by two-step synthesis: electrodeposition of Zn and replacement in AlCl₃ solution. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected-area electron diffraction techniques were used to characterize the Al nanowires obtained. SEM and TEM images taken from the different areas of Al nanowire arrays show that we can control the growth of aligned Al nanowires with different diameters in a single process at the same time. The investigation results not only have potential applications in photoelectric devices but also open up a new method for fabricating nano-scale materials.     

Field emission of vertically aligned V2O5 nanowires on an ITO surface prepared with gaseous transport

Growing V₂O₅ nanowires (NWs) on a conducting glass substrate combines gaseous transport and pyrolytic deposition of vanadium polyoxometalate anions, and yields vertically aligned vanadium-oxide nanowires. Scanning electron and transmission electron microscopy, selected-area electron diffraction, Raman spectra and powder X-ray analyses indicate that V₂O₅ nanowires as synthesized were single-crystalline and grew anisotropically among direction [010]. NH₂OH·HCl served not only as a reducing agent to produce vanadium polyoxometalate clusters but also as a source of NH₃ gas to facilitate the vapor pyrolysis and deposition. The optical properties of V₂O₅ nanowires exhibit a character dependent on structure. Field emission (FE) measurements show a small turn-on field voltage ~8.3 V/μm, maximum current density 1.8 mA/cm², and a linear Fowler–Nordheim behavior.     

Zinc nanowires synthesized on a large scale by a simple carbothermal process

Metallic Zn nanowires have been synthesized by a new carbothermal reduction route in which ZnO and Eucalyptus sp. tar pitch were used as source materials. This simple practical procedure was capable of producing Zn nanowires in large quantities without reoxidation. This process was carried out in inert atmosphere, without vacuum or catalyst, at temperatures (800–900 °C) lower than those required in the carbothermal reduction of ZnO with graphite. A comparative study was performed using graphite that is traditionally used as a ZnO reducer, under the same experimental conditions, however, no reaction was observed. The new process involves the pyrolysis of biopitch to obtain a highly reactive coke and the reduction of ZnO with the release of Zn_(v) for the growth of Zn_(s) nanowires. The resulting Zn nanowires were characterized by X-ray diffractometry, energy-dispersive spectroscopy and scanning electron microscopy. Differential thermal analysis and thermogravimetric analysis coupled with infrared analysis techniques were used in an effort to understand the underlying mechanism and establish the best ratio biopitch/ZnO to be used. This paper presents the characterization of the as-synthesized nanowires and discusses the main reactions involved in their production.     

Synthesis and electrochemical study of novel Pt-decorated Ti nanowires

We report on a facile approach to fabricate free-standing Ti nanowires and Pt-decorated Ti nanowires via a one-step environment-friendly and template-free process. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) spectroscopy were employed to characterize the synthesized nanowires, showing that highly dense Ti nanowires with diameters of ～45 nm were directly grown on the Ti substrate and that the Pt nanoparticles coated onto the surface of Ti nanowires were uniform and ultrafine (～3 nm). Our electrochemical studies reveal that the active surface area of the Pt-decorated Ti nanowires is over 265 times larger than that of a polycrystalline Pt electrode and that the Pt-decorated Ti nanowires exhibit much higher activity for electrochemical oxidation of methanol compared to the polycrystalline Pt electrode.     

表面活性剂辅助合成CdWO4纳米棒和纳米线

以Na₂WO₄•2H₂O和CdCl₂ 为主要原料, 分别在十六烷基三甲基溴化铵(CTAB)和十二烷基苯磺酸钠(SDBS)表面活性剂中, 在180 ℃反应16 h, 水热制备了CdWO₄纳米棒和纳米线. 利用X射线粉末衍射(XRD)、透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)等手段对产物进行了表征, 并对其在室温下的发光特性进行了测定. 实验结果表明: 产物均为具有单斜结构的单相CdWO₄. 其中CdWO₄纳米棒具有单晶属性, 平均粒径约为63 nm, 长度近1 µm; 而CdWO₄纳米线具有多晶特性, 平均粒径约为12 nm, 长度达十几微米. 当激发波长为253 nm时均有460 nm强的发射峰, 其中CdWO₄单晶纳米棒的发光强度大于CdWO₄多晶纳米线. 分别对CdWO₄纳米棒和纳米线形成的可能机理进行了初步分析.     

ZnxCd1-xS纳米线的可控合成及其可调的光学性质

采用简单的气相沉积法,合成了不同组成的Zn_xCd_1-xS (0< x <1)纳米线. 利用扫描电子显微镜、透射电子显微镜和电子能谱研究了所制得的纳米线的表面形貌和组成. 该方法以Au为催化剂,简单控制起始物质的相对用量和沉积温度,可以获得可控的Zn/Cd 比例. X射线衍射结果表明所制得的Zn_xCd_1-xS纳米线具有纤维锌矿的单晶结构. 根据制得纳米线的表面形貌讨论了纳米线可能的生长机理为“底部生长”机理. 利用拉曼光谱和光致发光光谱研究了Zn_xCd_1-xS纳米线的光学性质,其纵向光学(LO)声子的拉曼位移频率随着组成的变化在ZnS和CdS的拉曼位移频率之间连续变化. 光致发光光谱中同时存在带边发光和缺陷发光. Zn_xCd_1-xS纳米线的带间跃迁的频率可随着组成的调节而调节,纳米线的禁带宽度介于ZnS (3.63 eV)和CdS (2.41 eV)的禁带宽度之间.     

化学气相沉积法合成高结晶度的三元系Cd1-xZnxS纳米线

以硫化锌、硫化镉和活性碳粉作为反应物,利用化学气相沉积方法成功合成了单晶Cd1-xZnxS纳米线.为了解产物的结构、形貌、组分、微结构以及声子振动模式,对样品进行了扫描电镜、透射电镜、X射线衍射、能谱分析以及拉曼光谱分析.分析显示合成的纳米线为六方铅锌矿结构,生长方向沿着[210]方向,长度均为10μm,直径在80-100 nm之间,x的值约为0.2.拉曼光谱分析显示产物的拉曼峰位与纯CdS相比发生了蓝移.     

化学气相沉积法合成高结晶度的三元系Cd1-xZnxS纳米线

以硫化锌、硫化镉和活性碳粉作为反应物, 利用化学气相沉积方法成功合成了单晶Cd1-xZnxS纳米线. 为了解产物的结构、形貌、组分、微结构以及声子振动模式, 对样品进行了扫描电镜、透射电镜、X射线衍射、能谱分析以及拉曼光谱分析. 分析显示合成的纳米线为六方铅锌矿结构, 生长方向沿着[210]方向, 长度均为10 μm, 直径在80-100 nm之间, x的值约为0.2. 拉曼光谱分析显示产物的拉曼峰位与纯CdS相比发生了蓝移.