Ultrahigh-density nanowire lattices and circuits

We describe a general method for producing ultrahigh-density arrays of aligned metal and semiconductor nanowires and nanowire circuits. The technique is based on translating thin film growth thickness control into planar wire arrays. Nanowires were fabricated with diameters and pitches (center-to-center distances) as small as 8 nanometers and 16 nanometers, respectively. The nanowires have high aspect ratios (up to 10(6)), and the process can be carried out multiple times to produce simple circuits of crossed nanowires with a nanowire junction density in excess of 10(11) per square centimeter. The nanowires can also be used in nanomechanical devices; a high-frequency nanomechanical resonator is demonstrated.     

Metallic colloids in molten salts

Gold, silver, and silver iodide sols were prepared in mixed nitrate melts. Electron micographs of the gold and silver sols show particles smaller than 1 micron. The gold sols exhibit conventional absorption and scattering spectra. Both gold amid silver sols show unusual stability.     

Germanium nanowire growth below the eutectic temperature

Nanowires are conventionally assumed to grow via the vapor-liquid-solid process, in which material from the vapor is incorporated into the growing nanowire via a liquid catalyst, commonly a low-melting point eutectic alloy. However, nanowires have been observed to grow below the eutectic temperature, and the state of the catalyst remains controversial. Using in situ microscopy, we showed that, for the classic Ge/Au system, nanowire growth can occur below the eutectic temperature with either liquid or solid catalysts at the same temperature. We found, unexpectedly, that the catalyst state depends on the growth pressure and thermal history. We suggest that these phenomena may be due to kinetic enrichment of the eutectic alloy composition and expect these results to be relevant for other nanowire systems.     

基于动力学的钢丝绳断丝数检测方法初探

钢丝绳是由许多优质碳素钢丝捻制成股,再由若干股围绕绳芯捻制成绳。由于钢丝绳结构的特殊性决定了它具有较好的力学性能,同时在工作可靠性和结构多样性等方面也表现出独特的优点,被广泛应用于众多工程领域。钢丝绳的设计、制造、使用和维护等方面还存在着相当多的技术难题,甚至还不能给出钢丝绳在使用过程中真正意义上的安全系数．以至于钢丝绳工程结构时常出现意外安全事故。针对钢丝绳无损检测问题展开了研究．用弦振动方程建立钢丝绳断丝数检测方程。利用该方程对悬索钢丝绳的断丝数进行了探索性试验研究。结果表明,钢丝绳断丝数较少．负载较小时,对基频的影响较小;当钢丝绳断丝数较多,负载较大时,对基频的影响较为明显。因此。该方法为钢丝绳无损检测技术提供了一种的新的检测手段．具备一定的可行性。图4表1参11     

Silver-intensified gold and peroxidase as dual ultrastructural immunolabels for pre- and postsynaptic neurotransmitters

An ultrastructural immunostaining method that uses silver-intensified gold was combined with another procedure that uses biotin peroxidase conjugates to allow simultaneous identification of two neurotransmitter-related antigens in the central nervous system. Tyrosine hydroxylase-immunoreactive neurons labeled with silver-intensified gold could be differentiated at both light and electron microscopic levels from glutamate decarboxylase-immunoreactive neurons labeled with peroxidase. Cross reactivity of the second group of immunoreagents with the first group was reduced by the heavy metal silver shell formed around the colloidal gold immunoglobulin complex. With this dual pre-embedding method, peroxidase-stained axons containing the inhibitory neurotransmitter gamma-aminobutyric acid were found to synapse directly on silver-stained dopamine neurons in the rat dorsomedial hypothalamus. This approach can be used in combination with a post-embedding immunocytochemical colloidal gold procedure, allowing ultrastructural identification of three neurotransmitter-related antigens in the same tissue section.     

Packing C60 in boron nitride nanotubes

We have created insulated C60 nanowire by packing C60 molecules into the interior of insulating boron nitride nanotubes (BNNTs). For small-diameter BNNTs, the wire consists of a linear chain of C60 molecules.With increasing BNNT inner diameter, unusual C60 stacking configurations are obtained (including helical, hollow core, and incommensurate) that are unknown for bulk or thin-film forms of C60.C60 in BNNTs thus presents a model system for studying the properties of dimensionally constrained "silo" crystal structures. For the linear-chain case, we have fused the C60 molecules to form a single-walled carbon nanotube inside the insulating BNNT.     

彩色免疫金银染色法检测猪繁殖与呼吸综合征病毒的研究

试验首次建立了固相载体上的彩色免疫金银染色法(CIGSS)检测猪繁殖与呼吸综合征病毒(PRRSV),并获得成功。用提纯的PRRSV高免兔制备高免血清,按常规方法提取兔抗PRRSVIgG,建立了检测PRRSV抗原的彩色免疫金银染色法。经方阵试验确定最佳兔抗PRRSV IgG工作浓度为1∶400,金标羊抗兔IgG的工作浓度为1∶1 000,银染色的时间为15 min,彩染的时间为2 min。用该法对提纯的PRRSV病毒抗原的最低检出量为1.469μg/ml,其敏感性为DIGFA的5倍。以CIGSS法检测了52份疑似PRRSV感染的猪样本,阳性率为53.84%,而检测猪细小病毒、猪瘟病毒、猪伪狂犬病毒、猪巴氏杆菌以及正常的Marc-145细胞培养物,均为阴性反应。表明该法具有快速、准确、操作简便、敏感性高、易于判断、特异性强、重复性好等优点,可用于大量PRRSV抗原样本的检测。     

Electrochemical defect-mediated thin-film growth

An electrodeposition technique is described that produces atomically flat epitaxial metal overlayers of quality similar to that obtained by ultrahigh vacuum techniques at elevated temperature. In this approach, a metal of interest such as silver is co-deposited with a reversibly deposited mediator metal. The mediator is periodically deposited and stripped from the surface, and this serves to significantly increase the density of two-dimensional islands of silver atoms, promoting a layer-by-layer thin-film growth mode. In situ scanning tunneling microscopy was used to demonstrate the growth process for the heteroepitaxial system silver/gold (111) with either lead or copper as the mediator.     

芒果皮提取物合成纳米银及抑菌性研究

以芒果皮提取物作为还原剂,采用生物法合成纳米银粒子。研究了合成过程中pH值、芒果皮提取物添加量和硝酸银浓度对合成粒径和形貌的影响,研究结果通过紫外可见分光光度法、X射线衍射和透射电镜进行了表征。通过表征,分析得到合成的纳米银的粒径介于7～27nm之间,其结晶为立体对称晶体,pH值为11,芒果皮提取物的添加量为0.1mL,硝酸银溶液浓度为0.5mM,反应条件为80℃,水浴15min时,合成的纳米银粒径最小。试验结果表明,生物合成的纳米银粒子的抗菌性良好。     

从篮球文化视角下洞悉历届奥运会美国篮球成绩

通过文献资料、逻辑分析等研究方法,得出,美国男篮参加了17届奥运会的男子篮球比赛,获得14 次金牌、1次银牌和2次铜牌;美国女篮参加了9届奥运会篮球比赛,取得7金1银1铜;美国篮球文化具有鲜 明的“民族性”特点;美国篮球层层衔接的竞赛训练体系是美国篮球取得辉煌成绩的基石。     

Nanoparticles with Raman spectroscopic fingerprints for DNA and RNA detection

Multiplexed detection of oligonucleotide targets has been performed with gold nanoparticle probes labeled with oligonucleotides and Raman-active dyes. The gold nanoparticles facilitate the formation of a silver coating that acts as a surface-enhanced Raman scattering promoter for the dye-labeled particles that have been captured by target molecules and an underlying chip in microarray format. The strategy provides the high-sensitivity and high-selectivity attributes of gray-scale scanometric detection but adds multiplexing and ratioing capabilities because a very large number of probes can be designed based on the concept of using a Raman tag as a narrow-band spectroscopic fingerprint. Six dissimilar DNA targets with six Raman-labeled nanoparticle probes were distinguished, as well as two RNA targets with single nucleotide polymorphisms. The current unoptimized detection limit of this method is 20 femtomolar.     

Shape-controlled synthesis of gold and silver nanoparticles

Monodisperse samples of silver nanocubes were synthesized in large quantities by reducing silver nitrate with ethylene glycol in the presence of poly(vinyl pyrrolidone) (PVP). These cubes were single crystals and were characterized by a slightly truncated shape bounded by [100], [110], and [111] facets. The presence of PVP and its molar ratio (in terms of repeating unit) relative to silver nitrate both played important roles in determining the geometric shape and size of the product. The silver cubes could serve as sacrificial templates to generate single-crystalline nanoboxes of gold: hollow polyhedra bounded by six [100] and eight [111] facets. Controlling the size, shape, and structure of metal nanoparticles is technologically important because of the strong correlation between these parameters and optical, electrical, and catalytic properties.     

金银花叶红茶加工工艺初探

本文借鉴红茶加工工艺,对金银花叶试制红茶加工工艺进行初探,结果表明：感官审评方面,制得的金银花叶红茶产品,甜香持久,滋味甜醇,综合得分较高,为87.15,整体效果较好,说明金银花叶适合红茶类产品开发。通过内含成分检测分析,借鉴红茶工艺制的金银花叶红茶,水浸出物、多糖、黄铜等成分含量略低于花中含量,绿原酸略高于花蕾中含量;金银花叶红茶所含内含成分与花蕾中所含内含成分的种类相同,虽含量略有差异,但同样能说明其药用价值较大。由此可见,基于金银花叶潜在的药用价值,对其进行的开发应用意义较大。     

Direct-current nanogenerator driven by ultrasonic waves

We have developed a nanowire nanogenerator that is driven by an ultrasonic wave to produce continuous direct-current output. The nanogenerator was fabricated with vertically aligned zinc oxide nanowire arrays that were placed beneath a zigzag metal electrode with a small gap. The wave drives the electrode up and down to bend and/or vibrate the nanowires. A piezoelectric-semiconducting coupling process converts mechanical energy into electricity. The zigzag electrode acts as an array of parallel integrated metal tips that simultaneously and continuously create, collect, and output electricity from all of the nanowires. The approach presents an adaptable, mobile, and cost-effective technology for harvesting energy from the environment, and it offers a potential solution for powering nanodevices and nanosystems.     

MATERIALS SCIENCE: Weird Gold Nanowires

When the dimensions of matter are reduced to the nanometer scale and beyond, strange properties often emerge. In their Perspective, Tosatti and Prestipino discuss the weird gold nanowire structures reported by Kondo and Takayanagi. They explain why the wires may be helical and only form certain "magic" sizes. Other metals may form similarly strange structures with unusual properties.     

In situ observation of the electrochemical lithiation of a single SnO₂ nanowire electrode

We report the creation of a nanoscale electrochemical device inside a transmission electron microscope--consisting of a single tin dioxide (SnO(2)) nanowire anode, an ionic liquid electrolyte, and a bulk lithium cobalt dioxide (LiCoO(2)) cathode--and the in situ observation of the lithiation of the SnO(2) nanowire during electrochemical charging. Upon charging, a reaction front propagated progressively along the nanowire, causing the nanowire to swell, elongate, and spiral. The reaction front is a "Medusa zone" containing a high density of mobile dislocations, which are continuously nucleated and absorbed at the moving front. This dislocation cloud indicates large in-plane misfit stresses and is a structural precursor to electrochemically driven solid-state amorphization. Because lithiation-induced volume expansion, plasticity, and pulverization of electrode materials are the major mechanical effects that plague the performance and lifetime of high-capacity anodes in lithium-ion batteries, our observations provide important mechanistic insight for the design of advanced batteries.     

Nanoribbon waveguides for subwavelength photonics integration

Although the electrical integration of chemically synthesized nanowires has been achieved with lithography, optical integration, which promises high speeds and greater device versatility, remains unexplored. We describe the properties and functions of individual crystalline oxide nanoribbons that act as subwavelength optical waveguides and assess their applicability as nanoscale photonic elements. The length, flexibility, and strength of these structures enable their manipulation on surfaces, including the optical linking of nanoribbon waveguides and other nanowire elements to form networks and device components. We demonstrate the assembly of ribbon waveguides with nanowire light sources and detectors as a first step toward building nanowire photonic circuitry.     

Revealing magnetic interactions from single-atom magnetization curves

The miniaturization of magnetic devices toward the limit of single atoms calls for appropriate tools to study their magnetic properties. We demonstrate the ability to measure magnetization curves of individual magnetic atoms adsorbed on a nonmagnetic metallic substrate with use of a scanning tunneling microscope with a spin-polarized tip. We can map out low-energy magnetic interactions on the atomic scale as evidenced by the oscillating indirect exchange between a Co adatom and a nanowire on Pt(111). These results are important for the understanding of variations that are found in the magnetic properties of apparently identical adatoms because of different local environments.     

Directed assembly of one-dimensional nanostructures into functional networks

One-dimensional nanostructures, such as nanowires and nanotubes, represent the smallest dimension for efficient transport of electrons and excitons and thus are ideal building blocks for hierarchical assembly of functional nanoscale electronic and photonic structures. We report an approach for the hierarchical assembly of one-dimensional nanostructures into well-defined functional networks. We show that nanowires can be assembled into parallel arrays with control of the average separation and, by combining fluidic alignment with surface-patterning techniques, that it is also possible to control periodicity. In addition, complex crossed nanowire arrays can be prepared with layer-by-layer assembly with different flow directions for sequential steps. Transport studies show that the crossed nanowire arrays form electrically conducting networks, with individually addressable device function at each cross point.     

金包银围堰三维非线性应力应变分析

“金包银”围堰是一种新型的围堰型式,其具有工程量小、施工快速、稳定性、防渗性好等特点。本文结合土谷塘航电枢纽工程二期 “金包银”纵向围堰的工程实际情况,建立了 “金包银”围堰的三维数值模型,对其进行了三维非线性应力应变分析,分析其在施工工况和正常运行工况下围堰堰体的应力应变规律,并指出薄弱部位,并对混凝土面板配筋的必要性进行了探讨。