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Nanowires
Kinds of Nanowires Terms modified by Nanowires Selected AbstractsNanowire-Based Electrochemical BiosensorsELECTROANALYSIS, Issue 6 2006Abstract We review recent advances in biosensors based on one-dimensional (1-D) nanostructure field-effect transistors (FET). Specifically, we address the fabrication, functionalization, assembly/alignment and sensing applications of FET based on carbon nanotubes, silicon nanowires and conducting polymer nanowires. The advantages and disadvantages of various fabrication, functionalization, and assembling procedures of these nanosensors are reviewed and discussed. We evaluate how they have been used for detection of various biological molecules and how such devices have enabled the achievement of high sensitivity and selectivity with low detection limits. Finally, we conclude by highlighting some of the challenges researchers face in the 1-D nanostructures research arena and also predict the direction toward which future research in this area might be directed. [source] Electrical Percolation Behavior in Silver Nanowire,Polystyrene Composites: Simulation and ExperimentADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Sadie I. White Abstract The design and preparation of isotropic silver nanowire-polystyrene composites is described, in which the nanowires have finite L/D (< 35) and narrow L/D distribution. These model composites allow the L/D dependence of the electrical percolation threshold, ,c, to be isolated for finite- L/D particles. Experimental ,c values decrease with increasing L/D, as predicted qualitatively by analytical percolation models. However, quantitative agreement between experimental data and both soft-core and core,shell analytical models is not achieved, because both models are strictly accurate only in the infinite- L/D limit. To address this analytical limitation, a soft-core simulation method to calculate ,c and network conductivity for cylinders with finite L/D are developed. Our simulated ,c results agree strongly with our experimental data, suggesting i) that the infinite-aspect-ratio assumption cannot safely be made for experimental networks of particles with L/D < 35 and ii) in predicting ,c, the soft-core model makes a less significant assumption than the infinite- L/D models do. The demonstrated capability of the simulations to predict ,c in the finite- L/D regime will allow researchers to optimize the electrical properties of polymer nanocomposites of finite- L/D particles. [source] Palladium Nanowire from Precursor Nanowire: Crystal-to-Crystal Transformation via In,Situ Reduction by Polymer Matrix,ADVANCED FUNCTIONAL MATERIALS, Issue 14 2007S. Porel Abstract Precursor nanowires of potassium palladium(II) chloride crystallized inside a poly(vinyl alcohol) film are reduced to palladium nanowires by the polymer itself under mild thermal annealing. The chemical reaction occurring in situ inside the polymer film, including byproduct formation, is investigated through electronic absorption and X-ray photoelectron spectroscopy together with atomic force and electron microscopy. The overall process can be described as a novel case of crystal-to-crystal transformation at the nanoscopic level. Optical limiting characteristics of the nanowire-embedded polymer film are explored. The fabrication procedure developed, involving chemistry inside a polymer matrix mediated by the polymer, opens up a convenient route to the fabrication of free-standing metal nanowire-embedded thin films. [source] Vertical Epitaxial Co5Ge7 Nanowire and Nanobelt Arrays on a Thin Graphitic Layer for Flexible Field Emission DisplaysADVANCED MATERIALS, Issue 48 2009Hana Yoon Vertically aligned single-crystalline Co5Ge7 nanowire (NW) and nanobelt arrays are grown on a very thin graphite layer as well as a curved graphite layer with a good epitaxial lattice match. Co5Ge7 NW arrays, thus grown, show very efficient field emission properties comparable to those of carbon nanotubes and may be used for flexible field emission displays in the future. [source] Photoconductivity of a Single Small-Molecule Organic Nanowire,ADVANCED MATERIALS, Issue 12 2008Xiujuan Zhang The photoconductivity of a methyl squarylium (MeSq) single-nanowire device shows a high light sensitivity, wavelength-dependent photoresponse, good response speed, and excellent stability and reproducibility. Nanodevices fabricated on flexible substrates (see figure) exhibit good mechanical bendability and no obvious change in performance after bending to a curvature of 0.5,cm,1. [source] Nanowire-Based High-Performance "Micro Fuel Cells": One Nanowire, One Fuel Cell,ADVANCED MATERIALS, Issue 9 2008Caofeng Pan A micrometer-sized fuel cell based on Nafion/poly(vinyl pyrrolidone) nanowires is presented. The high-performance micro fuel cell containing a single NPNW proved easy to fabricate and delivered reproducible results. Values for the open-circuit voltage, maximum current-density, and power density were orders of magnitude higher than those of traditional fuel cells (see figure). Micro fuel cell assemblies may have future applications in integrated self-powered nanodevices. [source] Large-Scale "Surface-Programmed Assembly" of Pristine Vanadium Oxide Nanowire-Based Devices,ADVANCED MATERIALS, Issue 19 2005S. Myung "Surface-programmed assembly" is presented as a technique (see Figure) to achieve high-precision assembly and alignment of a large number of pristine V2O5 nanowires on solid substrates. Positively charged surface molecular patterns guide the assembly and alignment of negatively charged V2O5 nanowires on solid substrates. Large-scale assembly of V2O5 nanowire-based transistors is demonstrated and their gating effects are confirmed. [source] Nanowire,quantum-dot,polymer solar cellPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 9 2008A. Nadarajah Abstract We report first results on a new solar cell structure which incorporates n-type ZnO nanowires, an undoped CdSe layer, obtained from quantum dot precursors, and a p-type polymer layer as the main components. In the fabrication process the quantum dot layer is converted to a conformal ,30 nm thick polycrystalline film. The fabrication of the cell occurs in lab air at temperatures below 100 °C. Several intermittent annealing steps raise the energy conversion efficiency to approximately 1%. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] ChemInform Abstract: Synthesis of Nanowire and Hollow LiFePO4 Cathodes for High-Performance Lithium Batteries.CHEMINFORM, Issue 43 2008Sunhye Lim Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Solid Contact Micropipette Ion Selective Electrode for Potentiometric SECMELECTROANALYSIS, Issue 10 2007Gergely Gyetvai Abstract New solid contact ammonium micropipette electrodes (ISE), well applicable in scanning electrochemical microscopy are reported. The solid contact was made of a PEDOT nanowire coated carbon fiber, lowered down close to the orifice, and dipped inside the cocktail being in the pipette tip. This configuration provided low electrical resistance and good potential stability. Submicron tip size, usual in case of micropipette ISE-s easily can be fabricated in this way. The applicability of the electrode in SECM has been proved in SG/TC mode imaging urease enzyme active spots in urea solutions. [source] Effect of Contact Mode on the Electrical Transport and Field-Emission Performance of Individual Boron NanowiresADVANCED FUNCTIONAL MATERIALS, Issue 12 2010Fei Liu Abstract Vapor,liquid,solid processing of boron nanowires (BNWs) can be carried out either using a bottom-up or top-down growth mode, which results in different contact modes between the nanowire and the substrate. The contact mode may strongly affect the electrical transport and field-emission performance of the individual boron nanowires grown on a Si substrate. The electrical transport and field-emission characteristics of individual boron nanowires of different contact modes are investigated in situ using a scanning electron microscope. The contact barriers are very distinct for the different contact modes. Moreover, the transition from a "contact-limited" to a "bulk-limited" field-emission (FE) process is demonstrated in nanoemitters for the first time, and the proposed improved metal,insulator,vacuum (MIV) model may better illustrate the nonlinear behavior of the Fowler-Nordheim (FN) plots in these nanoscale systems. Individual BNWs with different contact modes have a discrepancy in their emission stability and vacuum breakdown characteristics though they have similar aspect ratios, which suggests that their electrical transport and field-emission performance are closely related to their contact mode. Boron nanowires grown in the base-up mode have better field-emission performances and are more beneficial than those grown in the top-down mode for various device applications. [source] A CdSe Nanowire/Quantum Dot Hybrid Architecture for Improving Solar Cell PerformanceADVANCED FUNCTIONAL MATERIALS, Issue 9 2010Yanghai Yu Abstract Incorporating colloidal CdSe quantum dots (QDs) into CdSe nanowire (NW)-based photoelectrochemical solar cells increases their incident-photon-to-carrier conversion efficiencies (IPCE) from 13% to 25% at 500,nm. While the effect could, in principle, stem from direct absorption and subsequent carrier generation by QDs, the overall IPCE increase occurs across the entire visible spectrum, even at wavelengths where the dots do not absorb light. This beneficial effect originates from an interplay between NWs and QDs where the latter fill voids between interconnected NWs, providing electrically accessible conduits, in turn, enabling better carrier transport to electrodes. The presence of QDs furthermore reduces the residual polarization anisotropy of random NW networks. Introducing QDs therefore addresses an important limiting constraint of NW photoelectrochemical solar cells. The effect appears to be general and may aid the future design and implementation of other NW-based photovoltaics. [source] Growth and Transfer of Monolithic Horizontal ZnO Nanowire Superstructures onto Flexible SubstratesADVANCED FUNCTIONAL MATERIALS, Issue 9 2010Sheng Xu A method of fabricating horizontally aligned ZnO nanowire (NW) arrays with full control over the width and length is demonstrated. A cross-sectional view of the NWs by transmission electron microscopy shows a "mushroom-like" structure. Novel monolithic multisegment superstructures are fabricated by making use of the lateral overgrowth. Ultralong horizontal ZnO NWs of an aspect ratio on the order of ten thousand are also demonstrated. These horizontal NWs are lifted off and transferred onto a flexible polymer substrate, which may have many great applications in horizontal ZnO NW-based nanosensor arrays, light-emitting diodes, optical gratings, integrated circuit interconnects, and high-output-power alternating-current nanogenerators. [source] Self-Organization of a Highly Integrated Silicon Nanowire Network on a Si(110),16,×,2 Surface by Controlling Domain GrowthADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Ie-Hong Hong Abstract Here, bottom-up nanofabrication for the two-dimensional self-organization of a highly integrated, well-defined silicon nanowire (SiNW) mesh on a naturally-patterned Si(110),16,×,2 surface by controlling the lateral growths of two non-orthogonal 16,×,2 domains is reported. This self-ordered nanomesh consists of two crossed arrays of parallel-aligned SiNWs with nearly identical widths of 1.8,2.5,nm and pitches of 5.0,5.9,nm, and is formed over a mesoscopic area of 300,×,270,nm2 so as to show a high integration density in excess of 104,µm,2. These crossed SiNWs exhibit semiconducting character with an equal band gap of ,0.95,eV as well as unique quantum confinement effect. Such an ultrahigh-density SiNW network can serve as a versatile nanotemplate for nanofabrication and nanointegration of the highly-integrated metal-silicide or molecular crossbar nanomesh on Si(110) surface for a broad range of device applications. Also, the multi-layer, vertically-stacked SiNW networks can be self-assembled through hierarchical growth, which opens the possibility for creating three-dimensionally interconnected crossbar circuits. The ability to self-organize an ultrahigh-density, functional SiNW network on a Si(110) surface represents a simple step toward the fabrication of highly-integrated crossbar nanocircuits in a very straightforward, fast, cost-effective, and high throughput process. [source] Wet and Dry Adhesion Properties of Self-Selective Nanowire ConnectorsADVANCED FUNCTIONAL MATERIALS, Issue 19 2009Hyunhyub Ko Abstract Here, the wet and dry adhesion properties of hybrid Ge/parylene nanowire (NW) connectors are examined. The ability of the NW connectors to bind strongly even under lubricating conditions, such as mineral oil, sheds light on the dominant role of van der Waals interactions in the observed adhesion. The superhydrophobic surface of the NW connectors enables the wet, self-cleaning of contaminant particles from the surface, similar to the lotus effect. In addition, the effect of NW length on the shear adhesion strength, repeated usability, and robustness of the connectors, all critical properties for applications that require reversible binding of components, is examined. [source] Light-Emitting Rubrene Nanowire Arrays: A Comparison with Rubrene Single CrystalsADVANCED FUNCTIONAL MATERIALS, Issue 5 2009Jin Woo Lee Abstract This is a report on a new method of growth of a light-emitting rubrene nanowires array with diameters of 200,±,10,nm by using organic vapor transport through Al2O3 nanoporous templates. Nanometer-scale laser confocal microscope (LCM) photoluminescence (PL) spectra and crystalline structures of the rubrene nanowires are compared with those of rubrene single crystals prepared with the same experimental conditions without the template. In the LCM PL spectra it is observed that the PL spectra and intensity varies with the detecting positions because of the crystal growth characteristics of the rubrene molecules. A single rubrene nanowire has a wider LCM PL band width than that of the rubrene single crystal. This may originate from the light emissions of the mixed polarized bands due to additional new crystallinity in the formation of the nanowires. From the current,voltage characteristic curves, the semiconducting nature of both the rubrene nanowires and single crystals is observed. [source] High Purity GaAs Nanowires Free of Planar Defects: Growth and Characterization,ADVANCED FUNCTIONAL MATERIALS, Issue 23 2008Hannah J. Joyce Abstract We investigate how to tailor the structural, crystallographic and optical properties of GaAs nanowires. Nanowires were grown by Au nanoparticle-catalyzed metalorganic chemical vapor deposition. A high arsine flow rate, that is, a high ratio of group V to group III precursors, imparts significant advantages. It dramatically reduces planar crystallographic defects and reduces intrinsic carbon dopant incorporation. Increasing V/III ratio further, however, instigates nanowire kinking and increases nanowire tapering. By choosing an intermediate V/III ratio we achieve uniform, vertically aligned GaAs nanowires, free of planar crystallographic defects, with excellent optical properties and high purity. These findings will greatly assist the development of future GaAs nanowire-based electronic and optoelectronic devices, and are expected to be more broadly relevant to the rational synthesis of other III,V nanowires. [source] Hierarchical Shelled ZnO Structures Made of Bunched Nanowire Arrays,ADVANCED FUNCTIONAL MATERIALS, Issue 8 2007P. Jiang Abstract The size- and morphology-controlled growth of ZnO nanowire (NW) arrays is potentially of interest for the design of advanced catalysts and nanodevices. By adjusting the reaction temperature, shelled structures of ZnO made of bunched ZnO NW arrays are prepared, grown out of metallic Zn microspheres through a wet-chemical route in a closed Teflon reactor. In this process, ZnO NWs are nucleated and subsequently grown into NWs on the surfaces of the microspheres as well as in strong alkali solution under the condition of the pre-existence of zincate (ZnO22,) ions. At a higher temperature (200,°C), three different types of bunched ZnO NW or sub-micrometer rodlike (SMR) aggregates are observed. At room temperature, however, the bunched ZnO NW arrays are found only to occur on the Zn microsphere surface, while double-pyramid-shaped or rhombus-shaped ZnO particles are formed in solution. The ZnO NWs exhibit an ultrathin structure with a length of ca.,,500,nm and a diameter of ca.,10,nm. The phenomenon may be well understood by the temperature-dependent growth process involved in different nucleation sources. A growth mechanism has been proposed in which the degree of ZnO22,saturation in the reaction solution plays a key role in controlling the nucleation and growth of the ZnO NWs or SMRs as well as in oxidizing the metallic Zn microspheres. Based on this consideration, ultrathin ZnO NW cluster arrays on the Zn microspheres are successfully obtained. Raman spectroscopy and photoluminescence measurements of the ultrathin ZnO NW cluster arrays have also been performed. [source] From Molecular Machines to Microscale Motility of Objects: Application as "Smart Materials", Sensors, and NanodevicesADVANCED FUNCTIONAL MATERIALS, Issue 5 2007I. Willner Abstract Machinelike operations are common functions in biological systems, and substantial recent research efforts are directed to mimic such processes at the molecular or nanoscale dimensions. The present Feature Article presents three complementary approaches to design machinelike operations: by the signal-triggered mechanical shuttling of molecular components; by the signal-triggering of chemical processes on surfaces, resulting in mechanical motion of micro/nanoscale objects; and by the fuel-triggered motility of biomolecule,metal nanowire hybrid systems. The shuttling of molecular components on molecular wires assembled on surfaces in semirotaxane configurations using electrical or optical triggering signals is described. The control of the hydrophilic/hydrophobic surface properties through molecular shuttling or by molecular bending/stretching processes is presented. Stress generated on microelements, such as cantilevers, results in the mechanical deflection of the cantilever. The deposition of a redox-active polyaniline film on a cantilever allows the reversible electrochemically induced deflection and retraction of the cantilever by the electrochemical oxidation or reduction of the polymer film, respectively. A micro-robot consisting of the polypyrrole (PPy) polymer deposited on a multi-addressable configuration of electrodes is described. Au magnetic core/shell nanoparticles are incorporated into a polyaniline film, and the conductivity of the composite polymer is controlled by an external magnet. Finally, the synthesis of a hybrid nanostructure consisting of two actin filaments tethered to the two ends of a Au nanowire is described. The adenosine triphosphate (ATP)-fueled motility of the hybrid nanostructure on a myosin monolayer associated with a solid support is demonstrated. [source] Estimating error in measuring thermal conductivity using a T-type nanosensorHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2009Yohei Ito Abstract We discuss the measurement error caused by fabrication and measurement of a T-type nanosensor with a suspended sub-micrometer Pt hot film that was developed to measure the thermal properties of individual nanowire materials. Comparison of numerical simulation and one-dimensional analysis revealed that the thermal conductivity of nanowire material such as a carbon nanotube is calculated to be 17% lower. As an example, the thermal conductivity measurement result for a SiC nanowire is reported. The error caused by contact thermal resistance is found to depend on the contact length and can be as great as 20%. It can be said that future measuring can have higher reliability by correcting the estimated measurement error. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20228 [source] Well-Defined Fullerene Nanowire Arrays,ADVANCED FUNCTIONAL MATERIALS, Issue 8 2003Y.-G. Guo Abstract Fullerene nanowire arrays with well-defined size and length have been prepared by a controllable technique. Fullerene molecules such as C60 are introduced into the pores of anodic aluminum oxide (AAO) templates under a direct current (DC) electric field and polymerized in the pores. Structure analysis shows that the C60 nanowires are mainly polycrystalline, and a rhombohedral polymeric phase is observed in their vibration spectra. The electrical conductivity of so-prepared nanowire arrays show a semiconducting behavior. The ability to fabricate the fullerene nanowire arrays with controlled structures represents an important step toward the development of chemical sensors and nanoscale electronic devices based on fullerenes. [source] Formation of Thick Porous Anodic Alumina Films and Nanowire Arrays on Silicon Wafers and Glass,ADVANCED FUNCTIONAL MATERIALS, Issue 8 2003O. Rabin Abstract A method for the fabrication of thick films of porous anodic alumina on rigid substrates is described. The anodic alumina film was generated by the anodization of an aluminum film evaporated on the substrate. The morphology of the barrier layer between the porous film and the substrate was different from that of anodic films grown on aluminum substrates. The removal of the barrier layer and the electrochemical growth of nanowires within the ordered pores were accomplished without the need to remove the anodic film from the substrate. We fabricated porous anodic alumina samples over large areas (up to 70 cm2), and deposited in them nanowire arrays of various materials. Long nanowires were obtained with lengths of at least 9 ,m and aspect ratios as high as 300. Due to their mechanical robustness and the built-in contact between the conducting substrate and the nanowires, the structures were useful for electrical transport measurements on the arrays. The method was also demonstrated on patterned and non-planar substrates, further expanding the range of applications of these porous alumina and nanowire assemblies. [source] Single ZnO Nanowire/p-type GaN Heterojunctions for Photovoltaic Devices and UV Light-Emitting DiodesADVANCED MATERIALS, Issue 38 2010Ya-Qing Bie We fabricate heterojunctions consisting of a single n-type ZnO nanowire and a p-type GaN film. The photovoltaic effect of heterojunctions exhibits open-circuit voltages ranging from 2 to 2.7 V, and a maximum output power reaching 80 nW. Light-emitting diodes with UV electroluminescence based on the heterojunctions are demonstrated. [source] Single-InN-Nanowire Nanogenerator with Upto 1 V Output VoltageADVANCED MATERIALS, Issue 36 2010Chi-Te Huang Piezoelectric potential of a InN nanowire (NW) growing along [0110] can be positive, negative, and zero depending on the direction of the applied transverse force. By measuring the output voltage of a InN-NW-based nanogenerator, about 40% to 55% of output voltages are within the range of -1 and -20 mV, and 25% to 30% of output voltages would exceed -100 mV. Some output voltages could reach the magnitude of -1000 mV, showing its great potential for fabricating high-output nanogenerators. [source] Electronic and Mechanical Coupling in Bent ZnO NanowiresADVANCED MATERIALS, Issue 48 2009Xiaobing Han A red shift of the exciton of ZnO nanowires is efficiently produced by bending strain, as demonstrated by a low-temperature (81,K) cathodoluminescence (CL) study of ZnO nanowires bent into L- or S-shapes. The figure shows a nanowire (Fig. a) with the positions of CL measurements marked. The corresponding CL spectra,revealing a peak shift and broadening in the region of the bend,are shown in Figure b. [source] Schottky-Gated Probe-Free ZnO Nanowire BiosensorADVANCED MATERIALS, Issue 48 2009Ping-Hung Yeh A nanowire-based nanosensor for detecting biologically and chemically charged molecules that is probe-free and highly sensitive is demonstrated. The device relies on the nonsymmetrical Schottky contact under reverse bias (see figure), and is much more sensitive than the device based on the symmetric ohmic contact. This approach serves as a guideline for designing more practical chemical and biochemical sensors. [source] Vertical Epitaxial Co5Ge7 Nanowire and Nanobelt Arrays on a Thin Graphitic Layer for Flexible Field Emission DisplaysADVANCED MATERIALS, Issue 48 2009Hana Yoon Vertically aligned single-crystalline Co5Ge7 nanowire (NW) and nanobelt arrays are grown on a very thin graphite layer as well as a curved graphite layer with a good epitaxial lattice match. Co5Ge7 NW arrays, thus grown, show very efficient field emission properties comparable to those of carbon nanotubes and may be used for flexible field emission displays in the future. [source] Organic Nanowires: Connecting Organic Nanowires (Adv. Mater.ADVANCED MATERIALS, Issue 47 200947/2009) Single-crystal organic nanowires are destined to become essential components in near-future organic electronics, however, currently one of the main drawbacks preventing implementation is the difficulty of creating stable interconnections between the nanowires. On p. 4816, Ana Borras and co-workers present a universal and effective method of creating nanowire,nanowire and nanowire,metallic Ohmic connections. The inside cover image shows the connection of single-crystal metallo-phthalocyanine nanowires via silver nanoparticles. [source] Shielding Nanowires and Nanotubes with Imogolite: A Route to NanocablesADVANCED MATERIALS, Issue 43 2009Agnieszka Kuc The use of an imogolite (aluminosilicate) sheath to protect a conducting core consisting of a carbon nanotube (CNT) or nanowire from mechanical and chemical attacks is proposed. The cross-sectional structure of such a nanocable is shown in the figure. The most stable CNT@ imogolite nanocable is calculated to have a tube,tube distance of 2.8,Å and an insertion energy of ca. 60,meV per carbon atom. [source] A Characterization Study of a Nanowire-Network Transistor with Various Channel LayersADVANCED MATERIALS, Issue 41 2009Jae Eun Jang The performance of a ZnO network transistor is studied by means of the change in threshold slope with varying number of nanowire channel layers. The threshold slope broadens as the number of layers in the channel increases and, in the case of a two-layer channel, a double turn-on effect can be observed. The gate-field simulation shows gate-field distortion by the surface of the nanowire. [source] | |||||||||||||||||||||||||||||||