Large-scale synthesis of single-crystalline RE2O3 (RE=Y, Dy, Ho, Er) nanobelts by a solid-liquid-phase chemical route

Yttrium-group heavy rare-earth sesquioxide (RE(2)O(3), RE=Y, Dy, Ho, Er) nanobelts were successfully fabricated by thermolysis of solid RE(NO(3))(3)x H(2)O in a dodecylamine/1-octadecene mixed solvent system. The synthetic principle is based on separating the nucleation and growth processes by utilizing the poor solubility of RE(NO(3))(3)chi H(2)O in the solvent mixture and the heat-transportation difference between the liquid and solid. By using dodecylamine, RE(2)O(3) nanobelts can be readily obtained. X-ray diffraction (XRD) analysis shows that the synthesized RE(2)O(3) nanobelts are body-centered cubic and crystalline. Field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), selective-area electron diffraction (SAED), and high-resolution transmission electron microscopy (HR-TEM) demonstrate that the synthesized RE(2)O(3) compounds possess regular geometric structure (beltlike) with perfect crystallinity. Preliminary experimental results prove that the dodecylamine plays a key role in the formation of RE(2)O(3) nanobelts and cannot be replaced by other surfactants. Furthermore, this method can be extended to the synthesis of RE(2)O(3) nanobelt/metal nanocrystal nanocomposites and ABO(3) (A=Y, Dy, Ho, Er; B=Al) and A(3)B(5)O(12) (A=Y, Dy, Ho, Er; B=Al)-type ternary oxide nanobelts, using mixed-metal nitrate salts in the correct stoichiometry instead of single rare-earth nitrates.     

Color-tunable photoluminescence of alloyed CdS(x)Se(1-x) nanobelts

High-quality CdSxSe1-x nanobelts of variable composition (0 相似文献   

High ethanol sensitivity of Palladium/TiO2 nanobelt surface heterostructures dominated by enlarged surface area and nano-Schottky junctions

TiO₂ nanobelts were prepared by the hydrothermal growth method. The surface of the nanobelts was coarsened by selective acid corrosion and functionalized with Pd catalyst particles. Three nanobelt samples (TiO₂ nanobelts, surface-coarsened TiO₂ nanobelts and Pd nanoparticle/TiO₂ nanobelt surface heterostructures) were configured as gas sensors and their sensing ability was measured. Both the surface-coarsened nanobelts and the Pd nanoparticle-decorated TiO₂ nanobelts exhibited dramatically improved sensitivity to ethanol vapor. Pd nanoparticle-decorated TiO₂ nanobelts with surface heterostructures exhibited the best sensitivity, selectivity, working temperature, response/recovery time, and reproducibility. The excellent ethanol sensing performance is attributed to the large surface area and enhancement by Schottky barrier-type junctions between the Pd nanoparticles and TiO₂ nanobelts.     

硼酸镁纳米带的制备、结构和生长机理

以晶态B和纳米MgO粉末为原料, 在1100 ℃含水的气氛下反应制备了新型准一维纳米材料硼酸镁纳米带. 采用多种表征方法, 如X射线衍射(XRD), 扫描电镜(SEM), 透射电镜(TEM), 能量色散谱仪(EDS)和傅立叶红外(FT-IR)等, 研究了产物的形貌和结构. 结果表明, 除了部分附着的Mg₂B₂O₅颗粒外, 产物主要为单晶的Mg₃B₂O₆纳米带. 其宽度在100～200 nm, 长度达到几十微米, 生长方向大致为[010]方向. 简要讨论了硼酸镁纳米带的生长机理和反应温度对产物的影响.     

Large-scale growth of millimeter-long single-crystalline ZnS nanobelts

Millimeter-long single-crystalline hexagonal ZnS nanobelts were grown on specific locations on a wafer scale. This is the first time that the millimeter-scale ZnS nanobelt has been synthesized. The longest nanobelts are about 3 mm. The as-grown nanobelts were characterized by means of field emission scanning electron microscopy, X-ray powder diffraction, high-resolution transmission electron microscopy, and selected area electron diffraction. The results indicate that the ultra-long nanobelts are pure single-crystalline hexagonal ZnS. There are two kinds of ZnS nanobelts existing in the products. One is the nanobelts that have two smooth sides and grow along the [0 0 1] longitudinal direction, and the other is the nanobelts that have one smooth side and one saw-teeth-like side, namely nanosaws, and grow along the [2 1 0] longitudinal direction. A vapor-liquid-solid mechanism is suggested for the lengthwise growth of the ZnS nanobelts (nanosaws) and a vapor-solid mechanism for the side direction growth of the saw-teeth of the nanosaws.     

Catalyst-assisted vapor-liquid-solid growth of single-crystal Ga2O3 nanobelts

Mass production of quasi-one-dimensional gallium oxide nanobelts is accomplished through graphite-thermal reduction of a mixture of gallium oxide powders and SnO2 nanopowders under controlled experimental conditions. Sn nanoparticles are located at or close to the tips of the nanobelts and served as the catalyst for the nanobelt growth by a vapor-liquid-solid mechanism. The morphology and microstructure of the nanobelts were characterized by scanning electron microscopy and high-resolution transmission electron microscopy. The Ga2O3 nanobelts grow along the [104] direction, the widths ranged from several tens to several hundreds of nanometers, and the lengths ranged from several tens to several hundreds of micrometers. The growth of Ga2O3 nanobelts is initiated by Sn nanoparticles via a catalyst-assisted vapor-liquid-solid process, which makes it possible to control the sizes of Ga2O3 nanobelts.     

Growth of SnO nanobelts and dendrites by a self-catalytic VLS process

This article reports on the growth of SnO nanobelts and dendrites by a carbothermal reduction process. The materials were synthesized in a sealed tube furnace at 1210 degrees C and at 1260 degrees C for 2 h, in a dynamic nitrogen atmosphere of 40 sccm. After synthesis, gray-black materials were collected downstream in the tube and the samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX). The results showed that the gray-black materials were composed of nanobelts, which grew in the [110] direction of the orthorhombic structure of SnO. Some of the belts also presented dendritic growth. The dendrites grew in the (110) planes of the SnO structure, and no defects were observed at the junction between the nanobelts and the dendrites. A self-catalytic vapor-liquid-solid (VLS) process was proposed to explain the growth of the SnO nanobelts and dendrites.     

Single-crystalline CuO nanobelts fabricated by a convenient route

A reverse micelle-assisted route for preparing CuO nanobelts from precursor Cu(OH)2- 4 is reported. The reverse micelles were used as microreactors, which led to anisotropic growth crystals during a simple solvothermal process. The formation conditions of the CuO nanobelts were also studied.     

Structures of oxide nanobelts and nanowires.

We have recently reported the synthesis of one-dimensional nanobelt structures of ZnO, SnO2, In2O3, CdO, Ga2O3, and PbO2 by evaporating the desired commercial metal oxide powders at high temperatures (Science (2001), 291, 1947). The as-synthesized oxide nanobelts are pure, structurally uniform, single crystalline, and most of them free from dislocations. The beltlike morphology appears to be a unique and common structural characteristic for the family of semiconducting oxides. In the present article, we focus on the twin and stacking fault planar defects found in oxide nanobelts and nanowires although they are rarely observed. Some interesting and unique growth morphologies are presented to illustrate the roles played by surface energy and kinetics in growth. It is shown that the surfaces of the oxide nanobelts are enclosed by the low-index, low-energy crystallographic facets. The growth morphology is largely dominated by the growth kinetics.     

Novel Zn1-xMnxSe (x = 0.1-0.4) one-dimensional nanostructures: nanowires, zigzagged nanobelts, and toothed nanosaws

Novel Zn1-xMnxSe one-dimensional nanostructures-straight nanowires (x = 0.1 and 0.3), zigzagged nanobelts (x = 0.4), and toothed nanosaws (x = 0.4)-were synthesized using the chemical vapor deposition method. They all consisted of single-crystalline wurtzite ZnSe crystals, irrespective of the Mn content. In particular, the nanosaws have a unique structure in which double-sided teeth are rooted in the nanowire core and bent so as to align as two parallel rows. The long axis is parallel to the [010] direction, and all of the teeth have the [0001] growth direction. The X-ray diffraction pattern confirms the formation of wurtzite ZnSe crystal and the decrease of the lattice constant owing to Mn doping. The Mn2+ emission at 2.1 eV (appeared below 100 K), originating from the d-d (4T1 --> 6A1) transition, proves the effective substitution of Mn2+ ions at the tetrahedral coordinate sites.     

A self-seeded, surfactant-directed hydrothermal growth of single crystalline lithium manganese oxide nanobelts from the commercial bulky particles

Single crystalline lithium manganese oxide nanobelts were obtained through a self-seeded, surfactant-directed growth process from the commercial bulky particles under hydrothermal treatment. A possible mechanism was proposed to explain the growth of the nanobelts. This new process could be extended to prepare other one-dimensional nanomaterials such as Se nanorods, Te nanotubes, and MnO2 nanowires.     

Chloride Assisted Growth of Aluminum Nitride Nanobelts and Their Enhanced Dielectric Responses

Aluminum nitride (AlN) nanobelts were successfully synthesized in high yield through a chloride assisted vapor-solid process. X-ray diffraction, transmission electron microscopy, and selected area electronic diffraction demonstrate that the as-prepared nanobelts are pure, structurally uniform and single crystalline, and can be indexed to hexagonal wurtzite structure. The micro observations show that there exist no defects in the obtained nanobelts. The growth direction of the nanobelts is along 0001. The frequency spectra of the relative dielectric constant and of the dielectric loss were measured in the frequency range of 50 Hz to 5 MHz. Analysis of these spectra indicates that the interface in samples has great influence on the dielectric behavior of samples. As compared with AlN micropowders, AlN nanobelts have much higher relative dielectric constant, especially at low frequencies at room temperature.     

高分子自组装Mn2O3花瓣状纳米带、纳米线的研究

通过控制热处理工艺条件, 利用Mn(CH3COO)2和具有特殊空间构型的聚乙烯醇(PVA), 在600 ℃合成了类花瓣状Mn2O3纳米带和纳米线结构. SEM, XRD表征分析证明Mn2O3纳米带结构为方铁锰矿晶型结构, 沿(222)方向择优生长. 分析了热处理工艺对一维纳米结构的影响机制. 初步探讨了Mn2O3一维纳米结构的生长机理.     

Mn掺杂SnO_2一维纳米结构的制备、形貌及光学性质

用化学气相沉积(CVD)法制备了Mn掺杂的SnO2一维纳米结构(纳米线及纳米带),X射线衍射(XRD)显示样品为金红石型SnO2晶体,其生长机理可分别归结为气-液-固(VLS)和气-固(VS)机理,生长温度和气态原料浓度的差别是造成样品形貌及生长机理不同的主要原因.样品的拉曼谱出现了500、543、694和720cm-1四个新拉曼谱峰,分别是由活性的红外模和表面模引起的.纳米线及纳米带发光峰位于520nm处,发光强度随样品中氧空位的增减出现由强到弱的变化.     

Controlled growth of large-area, uniform, vertically aligned arrays of alpha-Fe2O3 nanobelts and nanowires

Vertically aligned iron oxide nanobelt and nanowire arrays have been synthesized on a large-area surface by direct thermal oxidation of iron substrates under the flow of O(2). The effects of reactive gas pressure, composition, and temperature have been systematically studied. It was found that nanobelts (width, tens of nanometers; thickness, a few nanometers) are produced in the low-temperature region (approximately 700 degrees C) whereas cylindrical nanowires tens of nanometers thick are formed at relatively higher temperatures (approximately 800 degrees C). Both nanobelts and nanowires are mostly bicrystallites with a length of tens of micrometers which grow uniquely along the [110] direction. The growth habits of the nanobelts and nanowires in the two temperature regions indicate the role of growth rate anisotropy and surface energy in dictating the ultimate nanomorphologies.     

Single crystal SnO2 zigzag nanobelts

Zigzag SnO2 nanobelts have been synthesized by evaporating tin grain in air. XRD, SEM, and TEM were employed to characterize the prepared samples. SEM images showed large amounts of zigzag nanobelts with periodic morphology. XRD result showed a pure tetragonal SnO2 phase. HRTEM and SAED revealed a single crystal structure with [010] zone axis on the whole zigzag zone. The zigzag structure is deduced to be formed by shifting the growth direction from [101] to [10] or vice versa. Growing nanobelts along different equivalent directions opens a new avenue for the preparation of novel nanostructured materials.     

Sonochemical synthesis of mass single-crystal PbS nanobelts

Based on sonochemical technique, large-scale PbS nanobelts are successfully synthesized in the mixed solution of PbCl₂ and Na₂S₂O₃. These nanobelts are characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), selected area electronic diffraction, energy dispersive X-ray spectroscopy, and high-resolution TEM. The as-synthesized PbS nanobelts have width of about 80 nm, length up to several millimeters, and width-to-thickness ratio of about 5. In addition, the growth mechanism of PbS nanobelts is suggested.     

简易、可控制备硫化铅纳米带

以硝酸铅和硫代乙酰胺为前体,十二烷基苯磺酸钠（SDBS）扮演了前体和表面活性剂的双重角色,制备出硫化铅纳米带。 采用透射电子显微镜、X射线衍射和光致发光对所制备的纳米带进行了表征。 结果表明,中间产物PbSO4在水热条件下对PbS纳米带的进一步形成主要起到模板作用。 进一步考察了纳米带形成机理,结果表明,中间产物PbSO4对表面活性剂是有制约性的,而当改变中间产物保持条件不变的情况下,模板效应失控,只能得到不规则的微晶体。 实验结果表明,制备硫化铅纳米带反应速度较为缓慢,易于控制,为制备不同形貌纳米带提供了一种有效方法。     

Synthesis, field-emission and electric properties of metastable phase VO2 (A) ultra-long nanobelts

High quality single crystalline metastable phase VO(2) (A) ultra-long nanobelts were synthesized by hydrothermal method using inorganic V(2)O(5) sol as precursor and polyethylene glycol (PEG) as both surfactant and reducing agent. It was found that the oriented attach growth mechanism is responsible for the formation of VO(2) (A) nanobelts. In addition to an endothermic peak, an unusual exothermic peak was detected in DSC curve of the nanobelts. The temperature dependence of the lattice parameters have been studied, and it was found that the a-axis expands while the c-axis contracts in the high-temperature XRD test. The VO(2) (A) nanobelt has a low turn-on field of 3.8 V μm(-1) and a high field enhancement factor of 1739 in the field emission measurement. Electrical transport measurement of a single VO(2) (A) nanobelt gives a relative low hoping activation energy of 0.28 eV.     

Controlled synthesis of gold nanobelts and nanocombs in aqueous mixed surfactant solutions

Well-defined gold nanobelts as well as unique gold nanocombs made of nanobelts were readily synthesized by the reduction of HAuCl4 with ascorbic acid in aqueous mixed solutions of the cationic surfactant cetyltrimethylammonium bromide (CTAB) and the anionic surfactant sodium dodecylsulfonate (SDSn). Single-crystalline gold nanobelts grown along the <110> and <211> directions were prepared in mixed CTAB-SDSn solutions at 4 and 27 degrees C, respectively. Furthermore, single-crystalline gold nanocombs consisting of a <110>-oriented stem nanobelt and numerous <211>-oriented nanobelts grown perpendicularly on one side of the stem were fabricated by a two-step process with temperature changing from 4 to 27 degrees C. It was proposed that the mixed cationic-anionic surfactants exerted a subtle control on the growth of gold nanocrystals in solution due to the cooperative effect of mixed surfactants. This synthetic strategy may open a new route for the mild fabrication and hierarchical assembly of metal nanobelts in solution. The obtained gold nanobelts showed good electrocatalytic activity toward the oxidation of methanol in alkaline solution; in particular, the electrode modified with the nanobelts obtained at 27 degrees C exhibited an electrocatalytic activity considerably higher than normal polycrystalline gold electrode. Moreover, the gold nanobelts were used as the surface-enhanced Raman scattering (SERS) substrate for detecting the enhanced Raman spectra of p-aminothiophenol (PATP) molecules, and the gold nanobelts obtained at 4 degrees C exhibited an unusual larger enhancement of the b2 modes relative to the a1 modes for the adsorbed PATP molecules.