Self-organized hierarchical ZnS/SiO(2) nanowire heterostructures

Novel hierarchical heterostructures formed by wrapping ZnS nanowires with highly dense SiO(2) nanowires were successfully synthesized by a vapor-liquid-solid process. The as-synthesized products were characterized using X-ray diffraction, scanning electron microscopy and transmission electron microscopy equipped with an energy-dispersive X-ray spectrometer. Studies indicate that a typical hierarchical ZnS/SiO(2) heterostructure consists of a single-crystalline ZnS nanowire (core) with diameter gradually decreasing from several hundred nanometers to 20 nm and adjacent amorphous SiO(2) nanowires (branches) with diameters of about 20 nm. A possible growth mechanism was also proposed for the growth of the hierarchical heterostructures.     

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.     

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.     

Synthesis of vanadium oxide nanotubes via an ultrasonic method

Vanadium oxide nanotubes were synthesized using V₂O₅ powder as the precursor and hexadecylamine as the structure-directing template using a sol-gel reaction method followed by a one-step hydrothermal treatment. The effect of ultrasonics on the formation of nanotubes is reported. The structure and morphology of the nanotubes were investigated by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The inner and outer diameters of the nanotubes varied from 20 to 40 nm and 80 to 100 nm, respectively. The nanotubes measured several micrometers in length.     

Synthesis and characterization of Mn2P2S6 single-crystal nanorods and nanotubes

Mn2P2S6 single-crystal nanorods with diameters 20-40 nm and lengths up to 1 microm and nanotubes with diameters 40-50 nm and lengths ranging between 110 and 170 nm have been prepared through a low-temperature solvothermal method. They have been characterized by X-ray diffraction, transmission electron microscopy (TEM), high-resolution (HR) TEM, electron diffraction, energy-dispersive spectrometry analysis, X-ray photoelectron spectroscopy, and Raman spectroscopy.     

Synthesis and characterization of silicon nanowires on mesophase carbon microbead substrates by chemical vapor deposition

Silicon nanowires (SiNWs) have been fabricated by chemical vapor deposition at ambient pressure using SiCl(4) as a silicon source and mesophase carbon microbead powder as a substrate without any templates and/or metal catalysts. The SiNWs have a crystalline core with a very thin amorphous SiO(x) sheath. The obtained SiNWs are homogeneous with average diameters below 50 nm and lengths up to micrometers. Temperature and time effects on the growth of SiNWs were systematically studied. Higher reaction temperatures and longer reaction times resulted in larger diameters and higher yields of SiNWs. SiNWs with a better crystallinity can be obtained at higher temperatures and longer reaction times. The obtained SiNWs were characterized by field-emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and transmission electron microscopy.     

The solventless syntheses of unique PbS nanowires of X-shaped cross sections and the cooperative effects of ethylenediamine and a second salt

Unique PbS nanowires with x-shaped cross sections, with diameters in the range of 300-800 nm with an average of 598 nm (sigma = +/-21.7% ), and lengths of up to several tens of micrometers, have been made by a solventless method. Such nanowires show high adsorptivities of the PbS nanooctahedra, which can be washed off by ultrasound. The suitable precursor is obtained from a Pb(NO3)2/octanoate/ethylenediamine/dodecanethiol molar ratio of 1:2:1:1.6, and the PbS nanowires are produced by the thermolysis of such precursors at 280 degrees C for 1 hour. The X-ray diffraction, scanning electron microscopy, and transmission electron microscopy characterizations of the products and the keys of the morphological control have been reported. For the formation of such products, two cooperative effects are found to be crucial, the roles of ethylenediamine and a second salt, lead octanonate.     

Synthesis and evolution of PbS nanocrystals through a surfactant-assisted solvothermal route

We present a surfactant-assisted solvothermal approach for the controllable synthesis of a PbS nanocrystal at low temperature (85 degrees C). Nanotubes (400 nm in length with an outer diameter of 30 nm), bundle-like long nanorods (about 5-15 mum long and an average diameter of 100 nm), nanowires (5-20 mum in length and with a diameter of 20-50 nm), short nanorods (100-300 nm in length and an axial ratio of 5-10), nanoparticles (25 nm in width with an aspect ratio of 2), and nanocubes (a short axis length of 10 nm and a long axis length of 15 nm) were successfully prepared and characterized by transmission electron microscopy, scanning electron microscopy, and powder X-ray diffraction pattern. A series of experimental results indicated that several experimental factors, such as AOT concentration, ratio of [water]/[surfactant], reaction time, and ratio of the reagents, play key roles in the final morphologies of PbS. Possible formation mechanisms of PbS nanorods and nanotubes were proposed.     

Microwave-Assisted Heating Method for the Decoration of Carbon Nanotubes with Zinc Sulfide Nanoparticles

This study focuses on in situ synthesis of ZnS nanoparticles on the surface of multiwalled carbon nanotubes. By microwave-assisted chemical reaction of Zn(Ac)₂·2H₂O and NaS·9H₂O in glycol solution with carbon nanotubes, which were pretreated by oxidization in concentrated HNO₃. Zinc sulfide crystallite densely supported on carbon nanotubes with the diameter about 1 nm. The carbon nanotubes decorated by ZnS were characterized using transmission electron microscopy and x-ray diffraction. It is found that the multi-walled carbon nanotubes can not only act as a substrate but also change the crystal structures of ZnS in the reaction.     

Artificial lamellar mesostructures to WS(2) nanotubes

A direct pyrolysis method from artificial lamellar mesostructures to nanotubes was developed for the synthesis of tungsten disulfide (WS(2)) nanotubes. In this process, a tungsten sulfide artificial lamellar mesostructure composite with intercalated cetyltrimethylammonium cations (WS-L) was prepared on the basis of the recently developed template self-assembly of anionic tungstates (WS(4)(2-)) and cationic surfactant molecules (CTA(+)) in solution under appropriate conditions. After heating of this inorganic-surfactant lamellar composite material in an argon atmosphere to 850 degrees C, bulk quantities of uniform WS(2) nanotubes with diameters of 5-37.5 nm and lengths ranging from 0.2 to 5 microm were produced, which revealed a general rolling mechanism of layered sheets for tubule formation. The observations of transmission electron microscopy are in good agreement with the proposed rolling mechanism.     

Epitaxial heterostructures: side-to-side Si-ZnS, Si-ZnSe biaxial nanowires, and sandwichlike ZnS-Si-ZnS triaxial nanowires

Epitaxial semiconducting heterostructures: side-to-side Si-ZnS, Si-ZnSe biaxial nanowires, and sandwichlike ZnS-Si-ZnS triaxial nanowires were grown via a simple two-stage thermal evaporation of mixed SiO and ZnS or SiO and ZnSe powders under a precise temperature control. Each nanowire had a uniform diameter of 40-120 nm and length ranging from several to several tens of micrometers. Subnanowires of Si, ZnS, and ZnSe within them had a diameter of 20-50, 40-60, and 20-50 nm, respectively. The optical property (nanoscale cathodoluminescence) was also investigated from these new structures. It is proposed that the Si nanowires formed through disproportionation of SiO to Si in the first evaporation stage and then served as one-dimensional nanoscale substrates (or templates) for an epitaxial growth of ZnS or ZnSe nanowires in the following thermal evaporation of ZnS or ZnSe powders. The present results suggest that the simple method might be useful for the synthesis of many other heterostructures containing Si and II-VI or III-V semiconducting composite nanowires to meet the growing demands of nanoscale science and technology.     

Mild benzene-thermal route to GaP nanorods and nanospheres

GaP nanorods and nanospheres were synthesized from a mild benzene-thermal route at 240 and 300 degrees C, respectively, using Na, P, and GaCl(3) as the starting materials. The structure of the products was identified as zinc blende phase by X-ray powder diffraction (XRD). Transmission electron microscopy (TEM) images showed that, when the reaction temperature was 240 degrees C, the products were nanorods with widths of 20-40 nm and lengths of 200-500 nm and nanospheres with diameters of 20-40 nm. However, when the reaction temperature was increased to 300 degrees C, the products were only nanospheres, and the diameters increased to 40-60 nm. The reaction proceeded through a metallic gallium intermediate, and a solution-liquid-solid (SLS) mechanism was proposed for the one-dimensional growth. The products were also investigated by UV-vis absorption and X-ray photoelectron spectroscopy.     

One-pot synthesis of ZnS/polymer composites in supercritical CO2-ethanol solution and their applications in degradation of dyes

A facile method to decorate the polymeric hollow spheres with ZnS nanoparticles has been presented. In this method, the precursors, Zn(Ac)(2)H(2)O and CH(3)CSNH(2), were first adsorbed by the polymer substrate in supercritical CO(2)-ethanol solution at 35 degrees C. Followed by heating the mixture at 100 degrees C for 2 h, ZnS/polymer composites were obtained. The as-produced ZnS/polymer composites were characterized by means of IR spectra, X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy. It was demonstrated that crystalline ZnS nanoparticles with size of 3-5 nm were uniformly decorated on the polymer spheres under suitable conditions. The resultant ZnS/polymer composites exhibited high efficiency for degrading eosin B, methyl orange and methylene blue under UV light irradiation.     

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.     

Facile Preparation of Mn_2O_3 Nanowires by Thermal Decomposition of MnCO_3

Mn2O3 nanowires with diameters of about 130 nm and lengths up to tens of micrometers were synthesized by the thermal decomposition of MnCO3 precursors. It was identified that the growth of the cubic Mn2O3 nanowires was preferential along the [001] direction. The intermediate stage containing melting state and the particles of manganese oxide played an important role for the formation of Mn2O3 with one-dimensional structure. X-ray diffraction, scanning electron microscopy, and transmission electron microscop...     

Ag负载TiO2纳米管微波辅助水热法制备及其光催化性能

以微波辅助水热法制备了二氧化钛纳米管,然后通过浸渍法在其表面负载了银纳米颗粒.所得样品用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、氮吸附、X射线光电子能谱(XPS)、紫外-可见漫反射等测试方法表征.微波加热处理可以大大缩短反应时间,产物为无定型纳米管,经高温焙烧后转变成锐钛矿型二氧化钛.所得纳米管的外径为7-8 nm,内径为5-6 nm,管长约200 nm,比表面积可达371 m2·g-1.负载的银分散在纳米管的表面,对纳米管的结构与晶型没有影响,但是拓宽了二氧化钛的光吸收范围,使吸收边红移至可见光区,并且有效抑制了光生电子空穴的复合.在可见光降解罗丹明B的实验过程中,与Ag负载的P25及纯二氧化钛纳米管相比,Ag负载二氧化钛纳米管具有更高的可见光催化活性,并且当Ag/Ti 物质的量的比为0.5%时,可见光催化性能最好.     

Mg掺杂GaN纳米线的结构及其特性

利用类似Delta掺杂技术在硅衬底上沉积Mg:Ga2O3薄膜, 然后在850 ℃下对薄膜进行氨化, 反应后制备出大量Mg掺杂GaN纳米线. 采用扫描电子显微镜(SEM)、X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱和高分辨透射电子显微镜(HRTEM)对样品进行分析.结果表明, Mg掺杂GaN纳米线具有六方纤锌矿单晶结构, 纳米线的直径在30-50 nm范围内, 长度为几十微米.     

三步升温法合成阵列碳纳米管

本文使用结构简单的单温炉设备, 以二茂铁/三聚氰胺混合物为原料, 采用独特的三步升温方法于光滑的SiO₂衬底上合成出了大面积的阵列碳纳米管, 并对碳纳米管的形貌和结构进行了研究.     

单晶CaSO4纳米管的制备——非片状结构化合物形成纳米管的新途径

以Ti-O-Ti油酸偶合体作为结构引导生长剂,采用溶剂热技术成功地制备了单晶无水硫酸钙纳米管,并通过XRD、X射线能谱(EDX)、TEM、选区电子衍射(CBED)对CaSO₄纳米管进行了表征.其晶格常数与JCPDS标准卡单斜相CaSO₄晶体数值一致,属P3m1(164)空间群.纳米管呈均匀的直管形,直径约为30nm,内径约为10nm,长度达到3.0μm.并对硫酸钙纳米管的形成机理进行了浅析,提出了非片状结构的离子晶体,通过结构引导生长剂诱导生长成为片状结构,在溶剂热条件下弯曲、旋转、卷拢形成纳米管的新方法.     

Chelating ligand-mediated synthesis of hollow ZnS microspheres and its optical properties

Monodispersed hollow ZnS microspheres have been successfully synthesized by a facile ethylenediamine tetraacetic acid (EDTA) mediated hydrothermal route. The sizes of the hollow spheres vary from 1.5 to 3.5 microm when the reaction temperature varied from 130 to 230 degrees C. The formation of these hollow spheres is attributed to the oriented aggregation of ZnS nanocrystals around the gas-liquid interface between H(2)S and water. EDTA plays important role as chelating ligand and capping reagent, which regulates the release of Zn(2+) ions for the formation of ZnS hollow spheres. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis spectroscopy, photoluminescence, and Raman spectroscopy. The obtained ZnS hollow spheres show a sharp and photostable UV emission approximately 370 nm, which is attributed to the recombination process associated with interstitial sulfur vacancy.