Preparation and Use of Photocatalytically Active Segmented Ag|ZnO and Coaxial TiO2-Ag Nanowires Made by Templated Electrodeposition

PubMed Central

Maijenburg, A. Wouter; Rodijk, Eddy J.B.; Maas, Michiel G.; ten Elshof, Johan E.

2014-01-01

Photocatalytically active nanostructures require a large specific surface area with the presence of many catalytically active sites for the oxidation and reduction half reactions, and fast electron (hole) diffusion and charge separation. Nanowires present suitable architectures to meet these requirements. Axially segmented Ag|ZnO and radially segmented (coaxial) TiO2-Ag nanowires with a diameter of 200 nm and a length of 6-20 µm were made by templated electrodeposition within the pores of polycarbonate track-etched (PCTE) or anodized aluminum oxide (AAO) membranes, respectively. In the photocatalytic experiments, the ZnO and TiO2 phases acted as photoanodes, and Ag as cathode. No external circuit is needed to connect both electrodes, which is a key advantage over conventional photo-electrochemical cells. For making segmented Ag|ZnO nanowires, the Ag salt electrolyte was replaced after formation of the Ag segment to form a ZnO segment attached to the Ag segment. For making coaxial TiO2-Ag nanowires, a TiO2 gel was first formed by the electrochemically induced sol-gel method. Drying and thermal annealing of the as-formed TiO2 gel resulted in the formation of crystalline TiO2 nanotubes. A subsequent Ag electrodeposition step inside the TiO2 nanotubes resulted in formation of coaxial TiO2-Ag nanowires. Due to the combination of an n-type semiconductor (ZnO or TiO2) and a metal (Ag) within the same nanowire, a Schottky barrier was created at the interface between the phases. To demonstrate the photocatalytic activity of these nanowires, the Ag|ZnO nanowires were used in a photocatalytic experiment in which H2 gas was detected upon UV illumination of the nanowires dispersed in a methanol/water mixture. After 17 min of illumination, approximately 0.2 vol% H2 gas was detected from a suspension of ~0.1 g of Ag|ZnO nanowires in a 50 ml 80 vol% aqueous methanol solution. PMID:24837535

Comparative study of absorption in tilted silicon nanowire arrays for photovoltaics

PubMed Central

2014-01-01

Silicon nanowire arrays have been shown to demonstrate light trapping properties and promising potential for next-generation photovoltaics. In this paper, we show that the absorption enhancement in vertical nanowire arrays on a perfectly electric conductor can be further improved through tilting. Vertical nanowire arrays have a 66.2% improvement in ultimate efficiency over an ideal double-pass thin film of the equivalent amount of material. Tilted nanowire arrays, with the same amount of material, exhibit improved performance over vertical nanowire arrays across a broad range of tilt angles (from 38° to 72°). The optimum tilt of 53° has an improvement of 8.6% over that of vertical nanowire arrays and 80.4% over that of the ideal double-pass thin film. Tilted nanowire arrays exhibit improved absorption over the solar spectrum compared with vertical nanowires since the tilt allows for the excitation of additional modes besides the HE 1m modes that are excited at normal incidence. We also observed that tilted nanowire arrays have improved performance over vertical nanowire arrays for a large range of incidence angles (under about 60°). PMID:25435833

Comparative study of absorption in tilted silicon nanowire arrays for photovoltaics.

PubMed

Kayes, Md Imrul; Leu, Paul W

2014-01-01

Silicon nanowire arrays have been shown to demonstrate light trapping properties and promising potential for next-generation photovoltaics. In this paper, we show that the absorption enhancement in vertical nanowire arrays on a perfectly electric conductor can be further improved through tilting. Vertical nanowire arrays have a 66.2% improvement in ultimate efficiency over an ideal double-pass thin film of the equivalent amount of material. Tilted nanowire arrays, with the same amount of material, exhibit improved performance over vertical nanowire arrays across a broad range of tilt angles (from 38° to 72°). The optimum tilt of 53° has an improvement of 8.6% over that of vertical nanowire arrays and 80.4% over that of the ideal double-pass thin film. Tilted nanowire arrays exhibit improved absorption over the solar spectrum compared with vertical nanowires since the tilt allows for the excitation of additional modes besides the HE 1m modes that are excited at normal incidence. We also observed that tilted nanowire arrays have improved performance over vertical nanowire arrays for a large range of incidence angles (under about 60°).

MBE growth of nanowires using colloidal Ag nanoparticles

NASA Astrophysics Data System (ADS)

Bouravleuv, A. D.; Ilkiv, I. V.; Reznik, R. R.; Shtrom, I. V.; Khrebtov, A. I.; Samsonenko, Yu B.; Soshnikov, I. P.; Cirlin, G. E.; Lipsanen, H.

2017-06-01

Ag colloidal nanoparticles are used as a catalyst for growth of GaAs nanowires by the molecular beam epitaxy on the Si(111) and GaAs(111)B substrate surfaces. The scanning electron microscopy measurements revealed that the nanowire formation occurs in different ways on different substrates, but the parameters of the synthesized nanowires open great prospects for their further use.

Directed branch growth in aligned nanowire arrays.

PubMed

Beaudry, Allan L; LaForge, Joshua M; Tucker, Ryan T; Sorge, Jason B; Adamski, Nicholas L; Li, Peng; Taschuk, Michael T; Brett, Michael J

2014-01-01

Branch growth is directed along two, three, or four in-plane directions in vertically aligned nanowire arrays using vapor-liquid-solid glancing angle deposition (VLS-GLAD) flux engineering. In this work, a dynamically controlled collimated vapor flux guides branch placement during the self-catalyzed epitaxial growth of branched indium tin oxide nanowire arrays. The flux is positioned to grow branches on select nanowire facets, enabling fabrication of aligned nanotree arrays with L-, T-, or X-branching. In addition, a flux motion algorithm is designed to selectively elongate branches along one in-plane axis. Nanotrees are found to be aligned across large areas by X-ray diffraction pole figure analysis and through branch length and orientation measurements collected over 140 μm(2) from scanning electron microscopy images for each array. The pathway to guided assembly of nanowire architectures with controlled interconnectivity in three-dimensions using VLS-GLAD is discussed.

Electrodeposited highly-ordered manganese oxide nanowire arrays for supercapacitors

NASA Astrophysics Data System (ADS)

Liu, Haifeng; Lu, Bingqiang; Wei, Shuiqiang; Bao, Mi; Wen, Yanxuan; Wang, Fan

2012-07-01

Large arrays of well-aligned Mn oxide nanowires were prepared by electrodeposition using anodic aluminum oxide templates. The sizes of nanowires were tuned by varying the electrotype solution involved and the MnO2 nanowires with 10 μm in length were obtained in a neutral KMnO4 bath for 1 h. MnO2 nanowire arrays grown on conductor substance save the tedious electrode-making process, and electrochemical characterization demonstrates that the MnO2 nanowire arrays electrode has good capacitive behavior. Due to the limited mass transportation in narrow spacing, the spacing effects between the neighbor nanowires have show great influence to the electrochemical performance.

Enhanced photovoltaic performance of an inclined nanowire array solar cell.

PubMed

Wu, Yao; Yan, Xin; Zhang, Xia; Ren, Xiaomin

2015-11-30

An innovative solar cell based on inclined p-i-n nanowire array is designed and analyzed. The results show that the inclined geometry can sufficiently increase the conversion efficiency of solar cells by enhancing the absorption of light in the active region. By tuning the nanowire array density, nanowire diameter, nanowire length, as well as the proportion of intrinsic region of the inclined nanowire solar cell, a remarkable efficiency in excess of 16% can be obtained in GaAs. Similar results have been obtained in InP and Si nanowire solar cells, demonstrating the universality of the performance enhancement of inclined nanowire arrays.

Fabrication and surface enhanced Raman scattering effect of centimeter level AgCuAu composite nanowires

NASA Astrophysics Data System (ADS)

Xu, Dapeng; Zhang, Song; Yang, Wei; Chen, Jian

2017-10-01

Centimeter level AgCuAu composite nanowires were prepared by a solid-state ionics method under a direct current electric field (DCEF) using fast ionic conductor RbAg4I5 films and vacuum thermal evaporation method. The surface morphology and chemical composition of the AuAgCu composite nanowires were characterized by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), respectively. Raman enhancement performance of the AgCuAu composite nanowires substrates was detected by Rhodamine 6G (R6G) aqueous solutions as probe molecules. Long-range order and short-range order AgCuAu composite nanowires with the length of 1 cm were prepared. The nanowires were bamboo-shaped with high surface roughness and the diameters of nanowires ranged from 60 to 100 nm. The molar ratio of Ag:Cu:Au in composite nanowires is 15:2:1. The intrinsic Raman peaks of 10-16 mol/L R6G at 612, 773, 1125, 1182, 1307, 1361, 1418, 1506, 1545, 1575, 1597, 1650 cm-1 are all present when AgCuAu composite nanowires were used as the SERS substrates.

Fluorinion transfer in silver-assisted chemical etching for silicon nanowires arrays

NASA Astrophysics Data System (ADS)

Feng, Tianyu; Xu, Youlong; Zhang, Zhengwei; Mao, Shengchun

2015-08-01

Uniform silicon nanowires arrays (SiNWAs) were fabricated on unpolished rough silicon wafers through KOH pretreatment followed by silver-assisted chemical etching (SACE). Density functional theory (DFT) calculations were used to investigate the function of silver (Ag) at atomic scale in the etching process. Among three adsorption sites of Ag atom on Si(1 0 0) surface, Ag(T4) above the fourth-layer surface Si atoms could transfer fluorinion (F-) to adjacent Si successfully due to its stronger electrostatic attraction force between Ag(T4) and F-, smaller azimuth angle of Fsbnd Ag(T4)sbnd Si, shorter bond length of Fsbnd Si compared with Fsbnd Ag. As F- was transferred to adjacent Si by Ag(T4) one by one, the Si got away from the wafer in the form of SiF4 when it bonded with enough F- while Ag(T4) was still attached onto the Si wafer ready for next transfer. Cyclic voltammetry tests confirmed that Ag can improve the etching rate by transferring F- to Si.

Different growth regimes in InP nanowire growth mediated by Ag nanoparticles.

PubMed

Oliveira, D S; Zavarize, M; Tizei, L H G; Walls, M; Ospina, C A; Iikawa, F; Ugarte, D; Cotta, M A

2017-12-15

We report on the existence of two different regimes in one-step Ag-seeded InP nanowire growth. The vapor-liquid-solid-mechanism is present at larger In precursor flows and temperatures, ∼500 °C, yielding high aspect ratio and pure wurtzite InP nanowires with a semi-spherical metal particle at the thin apex. Periodic diameter oscillations can be achieved under extreme In supersaturations at this temperature range, showing the presence of a liquid catalyst. However, under lower temperatures and In precursor flows, large diameter InP nanowires with mixed wurtzite/zincblende segments are obtained, similarly to In-assisted growth. Chemical composition analysis suggest that In-rich droplet formation is catalyzed at the substrate surface via Ag nanoparticles; this process might be facilitated by the sulfur contamination detected in these nanoparticles. Furthermore, part of the original Ag nanoparticle remains solid and is embedded inside the actual catalyst, providing an in situ method to switch growth mechanisms upon changing In precursor flow. Nevertheless, our Ag-seeded InP nanowires exhibit overall optical emission spectra consistent with the observed structural properties and similar to Au-catalyzed InP nanowires. We thus show that Ag nanoparticles may be a suitable replacement for Au in InP nanowire growth.

Strong polarization-dependent terahertz modulation of aligned Ag nanowires on Si substrate.

PubMed

Lee, Gyuseok; Maeng, Inhee; Kang, Chul; Oh, Myoung-Kyu; Kee, Chul-Sik

2018-05-14

Optically tunable, strong polarization-dependent transmission of terahertz pulses through aligned Ag nanowires on a Si substrate is demonstrated. Terahertz pulses primarily pass through the Ag nanowires and the transmittance is weakly dependent on the angle between the direction of polarization of the terahertz pulse and the direction of nanowire alignment. However, the transmission of a terahertz pulse through optically excited materials strongly depends on the polarization direction. The extinction ratio increases as the power of the pumping laser increases. The enhanced polarization dependency is explained by the redistribution of photocarriers, which accelerates the sintering effect along the direction of alignment of the Ag nanowires. The photocarrier redistribution effect is examined by the enhancement of terahertz emission from the sample. Oblique metal nanowires on Si could be utilized for designing optically tunable terahertz polarization modulators.

Nanowire sensor, sensor array, and method for making the same

NASA Technical Reports Server (NTRS)

Homer, Margie (Inventor); Fleurial, Jean-Pierre (Inventor); Bugga, Ratnakumar (Inventor); Vasquez, Richard (Inventor); Yun, Minhee (Inventor); Myung, Nosang (Inventor); Choi, Daniel (Inventor); Goddard, William (Inventor); Ryan, Margaret (Inventor); Yen, Shiao-Pin (Inventor)

2012-01-01

The present invention relates to a nanowire sensor and method for forming the same. More specifically, the nanowire sensor comprises at least one nanowire formed on a substrate, with a sensor receptor disposed on a surface of the nanowire, thereby forming a receptor-coated nanowire. The nanowire sensor can be arranged as a sensor sub-unit comprising a plurality of homogeneously receptor-coated nanowires. A plurality of sensor subunits can be formed to collectively comprise a nanowire sensor array. Each sensor subunit in the nanowire sensor array can be formed to sense a different stimulus, allowing a user to sense a plurality of stimuli. Additionally, each sensor subunit can be formed to sense the same stimuli through different aspects of the stimulus. The sensor array is fabricated through a variety of techniques, such as by creating nanopores on a substrate and electrodepositing nanowires within the nanopores.

Room-temperature solution synthesis of Ag nanoparticle functionalized molybdenum oxide nanowires and their catalytic applications.

PubMed

Dong, Wenjun; Huang, Huandi; Zhu, Yanjun; Li, Xiaoyun; Wang, Xuebin; Li, Chaorong; Chen, Benyong; Wang, Ge; Shi, Zhan

2012-10-26

A simple chemical solution route for the synthesis of large-scale high-quality Ag nanoparticle functionalized molybdenum oxide nanowire at room temperature has been developed. In the synthesis, the protonated amine was intercalated into the molybdenum bronze layers to reduce the electrostatic force of the lamellar structures, and then the Ag nanoparticle functionalized long nanowires could be easily induced by a redox reaction between a molybdenum oxide-amine intermediate and Ag(+) at room temperature. The intercalation lamellar structures improved the nucleation and growth of the Ag nanoparticles, with the result that uniform Ag nanoparticles occurred on the surface of the MoO(3) nanowire. In this way Ag nanoparticles with average sizes of around 6 nm, and high-purity nanowires with mean diameter of around 50 nm and with typical lengths of several tens to hundreds of micrometers were produced. The heteronanostructured nanowires were intricately and inseparably connected to each other with hydrogen bonds and/or bridge oxygen atoms and packed together, forming a paper-like porous network film. The Ag-MoO(3) nanowire film performs a promoted catalytic property for the epoxidation of cis-cyclooctene, and the heteronanostructured nanowire film sensor shows excellent sensing performance to hydrogen and oxygen at room temperature.

Highly Stretchable and Transparent Supercapacitor by Ag-Au Core-Shell Nanowire Network with High Electrochemical Stability.

PubMed

Lee, Habeom; Hong, Sukjoon; Lee, Jinhwan; Suh, Young Duk; Kwon, Jinhyeong; Moon, Hyunjin; Kim, Hyeonseok; Yeo, Junyeob; Ko, Seung Hwan

2016-06-22

Stretchable and transparent electronics have steadily attracted huge attention in wearable devices. Although Ag nanowire is the one of the most promising candidates for transparent and stretchable electronics, its electrochemical instability has forbidden its application to the development of electrochemical energy devices such as supercapacitors. Here, we introduce a highly stretchable and transparent supercapacitor based on electrochemically stable Ag-Au core-shell nanowire percolation network electrode. We developed a simple solution process to synthesize the Ag-Au core-shell nanowire with excellent electrical conductivity as well as greatly enhanced chemical and electrochemical stabilities compared to pristine Ag nanowire. The proposed core-shell nanowire-based supercapacitor still possesses fine optical transmittance and outstanding mechanical stability up to 60% strain. The Ag-Au core-shell nanowire can be a strong candidate for future wearable electrochemical energy devices.

Conducting polymer nanowire arrays for high performance supercapacitors.

PubMed

Wang, Kai; Wu, Haiping; Meng, Yuena; Wei, Zhixiang

2014-01-15

This Review provides a brief summary of the most recent research developments in the fabrication and application of one-dimensional ordered conducting polymers nanostructure (especially nanowire arrays) and their composites as electrodes for supercapacitors. By controlling the nucleation and growth process of polymerization, aligned conducting polymer nanowire arrays and their composites with nano-carbon materials can be prepared by employing in situ chemical polymerization or electrochemical polymerization without a template. This kind of nanostructure (such as polypyrrole and polyaniline nanowire arrays) possesses high capacitance, superior rate capability ascribed to large electrochemical surface, and an optimal ion diffusion path in the ordered nanowire structure, which is proved to be an ideal electrode material for high performance supercapacitors. Furthermore, flexible, micro-scale, threadlike, and multifunctional supercapacitors are introduced based on conducting polyaniline nanowire arrays and their composites. These prototypes of supercapacitors utilize the high flexibility, good processability, and large capacitance of conducting polymers, which efficiently extend the usage of supercapacitors in various situations, and even for a complicated integration system of different electronic devices. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Recrystallized arrays of bismuth nanowires with trigonal orientation.

PubMed

Limmer, Steven J; Yelton, W Graham; Erickson, Kristopher J; Medlin, Douglas L; Siegal, Michael P

2014-01-01

We demonstrate methods to improve the crystalline-quality of free-standing Bi nanowires arrays on a Si substrate and enhance the preferred trigonal orientation for thermoelectric performance by annealing the arrays above the 271.4 °C Bi melting point. The nanowires maintain their geometry during melting due to the formation of a thin Bi-oxide protective shell that contains the molten Bi. Recrystallizing nanowires from the melt improves crystallinity; those cooled rapidly demonstrate a strong trigonal orientation preference.

High-quality metal oxide core/shell nanowire arrays on conductive substrates for electrochemical energy storage.

PubMed

Xia, Xinhui; Tu, Jiangping; Zhang, Yongqi; Wang, Xiuli; Gu, Changdong; Zhao, Xin-Bing; Fan, Hong Jin

2012-06-26

The high performance of a pseudocapacitor electrode relies largely on a scrupulous design of nanoarchitectures and smart hybridization of bespoke active materials. We present a powerful two-step solution-based method for the fabrication of transition metal oxide core/shell nanostructure arrays on various conductive substrates. Demonstrated examples include Co(3)O(4) or ZnO nanowire core and NiO nanoflake shells with a hierarchical and porous morphology. The "oriented attachment" and "self-assembly" crystal growth mechanisms are proposed to explain the formation of the NiO nanoflake shell. Supercapacitor electrodes based on the Co(3)O(4)/NiO nanowire arrays on 3D macroporous nickel foam are thoroughly characterized. The electrodes exhibit a high specific capacitance of 853 F/g at 2 A/g after 6000 cycles and an excellent cycling stability, owing to the unique porous core/shell nanowire array architecture, and a rational combination of two electrochemically active materials. Our growth approach offers a new technique for the design and synthesis of transition metal oxide or hydroxide hierarchical nanoarrays that are promising for electrochemical energy storage, catalysis, and gas sensing applications.

1-D Metal Nanobead Arrays within Encapsulated Nanowires via a Red-Ox-Induced Dewetting: Mechanism Study by Atom-Probe Tomography.

PubMed

Sun, Zhiyuan; Tzaguy, Avra; Hazut, Ori; Lauhon, Lincoln J; Yerushalmi, Roie; Seidman, David N

2017-12-13

Metal nanoparticle arrays are excellent candidates for a variety of applications due to the versatility of their morphology and structure at the nanoscale. Bottom-up self-assembly of metal nanoparticles provides an important complementary alternative to the traditional top-down lithography method and makes it possible to assemble structures with higher-order complexity, for example, nanospheres, nanocubes, and core-shell nanostructures. Here we present a mechanism study of the self-assembly process of 1-D noble metal nanoparticles arrays, composed of Au, Ag, and AuAg alloy nanoparticles. These are prepared within an encapsulated germanium nanowire, obtained by the oxidation of a metal-germanium nanowire hybrid structure. The resulting structure is a 1-D array of equidistant metal nanoparticles with the same diameter, the so-called nanobead (NB) array structure. Atom-probe tomography and transmission electron microscopy were utilized to investigate the details of the morphological and chemical evolution during the oxidation of the encapsulated metal-germanium nanowire hybrid-structures. The self-assembly of nanoparticles relies on the formation of a metal-germanium liquid alloy and the migration of the liquid alloy into the nanowire, followed by dewetting of the liquid during shape-confined oxidation where the liquid column breaks-up into nanoparticles due to the Plateau-Rayleigh instability. Our results demonstrate that the encapsulating oxide layer serves as a structural scaffold, retaining the overall shape during the eutectic liquid formation and demonstrates the relationship between the oxide mechanical properties and the final structural characteristics of the 1-D arrays. The mechanistic details revealed here provide a versatile tool-box for the bottom-up fabrication of 1-D arrays nanopatterning that can be modified for multiple applications according to the RedOx properties of the material system components.

Solar-Light-Driven Renewable Butanol Separation by Core-Shell Ag@ZIF-8 Nanowires.

PubMed

Liu, Xu; He, Liangcan; Zheng, Jianzhong; Guo, Jun; Bi, Feng; Ma, Xiang; Zhao, Kun; Liu, Yaling; Song, Rui; Tang, Zhiyong

2015-06-03

Core-shell Ag@ZIF-8 nanowires, where single Ag nanowires are coated with uniform zeolitic-imidazolate-framework-8 (ZIF-8) shells, successfully realize renewable adsorptive separation of low concentrations of butanol from an aqueous medium under solar light irradiation by taking advantage of the exceptional adsorption capability of the ZIF-8 shells toward butanol and the unique plasmonic photothermal effect of the Ag nanowire cores. Impressively, the high separation efficiency is maintained as almost unchanged, even after 10 adsorption/desorption cycles. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Large-scale fabrication of vertically aligned ZnO nanowire arrays

DOEpatents

Wang, Zhong L; Das, Suman; Xu, Sheng; Yuan, Dajun; Guo, Rui; Wei, Yaguang; Wu, Wenzhuo

2013-02-05

In a method for growing a nanowire array, a photoresist layer is placed onto a nanowire growth layer configured for growing nanowires therefrom. The photoresist layer is exposed to a coherent light interference pattern that includes periodically alternately spaced dark bands and light bands along a first orientation. The photoresist layer exposed to the coherent light interference pattern along a second orientation, transverse to the first orientation. The photoresist layer developed so as to remove photoresist from areas corresponding to areas of intersection of the dark bands of the interference pattern along the first orientation and the dark bands of the interference pattern along the second orientation, thereby leaving an ordered array of holes passing through the photoresist layer. The photoresist layer and the nanowire growth layer are placed into a nanowire growth environment, thereby growing nanowires from the nanowire growth layer through the array of holes.

Ultrafast Dynamics of Plasmon-Exciton Interaction of Ag Nanowire- Graphene Hybrids for Surface Catalytic Reactions

PubMed Central

Ding, Qianqian; Shi, Ying; Chen, Maodu; Li, Hui; Yang, Xianzhong; Qu, Yingqi; Liang, Wenjie; Sun, Mengtao

2016-01-01

Using the ultrafast pump-probe transient absorption spectroscopy, the femtosecond-resolved plasmon-exciton interaction of graphene-Ag nanowire hybrids is experimentally investigated, in the VIS-NIR region. The plasmonic lifetime of Ag nanowire is about 150 ± 7 femtosecond (fs). For a single layer of graphene, the fast dynamic process at 275 ± 77 fs is due to the excitation of graphene excitons, and the slow process at 1.4 ± 0.3 picosecond (ps) is due to the plasmonic hot electron interaction with phonons of graphene. For the graphene-Ag nanowire hybrids, the time scale of the plasmon-induced hot electron transferring to graphene is 534 ± 108 fs, and the metal plasmon enhanced graphene plasmon is about 3.2 ± 0.8 ps in the VIS region. The graphene-Ag nanowire hybrids can be used for plasmon-driven chemical reactions. This graphene-mediated surface-enhanced Raman scattering substrate significantly increases the probability and efficiency of surface catalytic reactions co-driven by graphene-Ag nanowire hybridization, in comparison with reactions individually driven by monolayer graphene or single Ag nanowire. This implies that the graphene-Ag nanowire hybrids can not only lead to a significant accumulation of high-density hot electrons, but also significantly increase the plasmon-to-electron conversion efficiency, due to strong plasmon-exciton coupling. PMID:27601199

Novel gradient-diameter magnetic nanowire arrays with unconventional magnetic anisotropy behaviors.

PubMed

Wang, Jing; Zuo, Zhili; Huang, Liang; Warsi, Muhammad Asif; Xiao, John Q; Hu, Jun

2018-06-21

Fe-Co-Ni gradient-diameter magnetic nanowire arrays were fabricated via direct-current electrodeposition into a tapered anodic aluminium oxide template. In contrast to the magnetic behaviors of uniform-diameter nanowire arrays, these arrays exhibited tailorable magnetic anisotropy that can be used to switch magnetic nanowires easily and unconventional temperature-dependent coercivity with much better thermal stability.

Nanowire sensors and arrays for chemical/biomolecule detection

NASA Technical Reports Server (NTRS)

Yun, Minhee; Lee, Choonsup; Vasquez, Richard P.; Ramanathan, K.; Bangar, M. A.; Chen, W.; Mulchandan, A.; Myung, N. V.

2005-01-01

We report electrochemical growth of single nanowire based sensors using e-beam patterned electrolyte channels, potentially enabling the controlled fabrication of individually addressable high density arrays. The electrodeposition technique results in nanowires with controlled dimensions, positions, alignments, and chemical compositions. Using this technique, we have fabricated single palladium nanowires with diameters ranging between 75 nm and 300 nm and conducting polymer nanowires (polypyrrole and polyaniline) with diameters between 100 nm and 200 nm. Using these single nanowires, we have successfully demonstrated gas sensing with Pd nanowires and pH sensing with polypirrole nanowires.

Impact of the air gap in nanowire array transistors

NASA Astrophysics Data System (ADS)

Mativetsky, Jeffrey; Yang, Tong; Mehta, Jeremy

Organic and inorganic semiconducting nanowires are promising for flexible electronic, energy harvesting, and sensing applications. Nanowire arrays processed from solution are particularly attractive for their ease of processing coupled with their potential for high performance. Random stacking has been observed, however, to hinder the collective electrical performance of such nanowire arrays. Here, we employ solution-processed organic semiconducting nanowires as a model system to assess the impact of the air gap that exists under a large portion of the active material in nanowire array transistors. Confocal Raman spectroscopy is used to non-invasively quantify the average air gap thickness which is found to be unexpectedly large - two to three times the nanowire diameter. This substantial air gap acts as an additional dielectric layer that diminishes the buildup of charge carriers, and can affect the measured charge carrier mobility and current on/off ratio by more than one order of magnitude. These results establish the importance of taking the air gap into account when fabricating and analyzing the performance of transistors based on one-dimensional nanostructures, such as organic and inorganic nanowires, or carbon nanotubes. NSF CAREER award DMR-1555028, NSF CMMI-1537648 , NSF MRI CMMI-1429176.

Nanowire array and nanowire solar cells and methods for forming the same

DOEpatents

Yang, Peidong [Berkeley, CA; Greene, Lori [Berkeley, CA; Law, Matthew [Berkeley, CA

2007-09-04

Homogeneous and dense arrays of nanowires are described. The nanowires can be formed in solution and can have average diameters of 40-300 nm and lengths of 1-3 .mu.m. They can be formed on any suitable substrate. Photovoltaic devices are also described.

Nanowire array and nanowire solar cells and methods for forming the same

DOEpatents

Yang, Peidong; Greene, Lori E.; Law, Matthew

2009-06-09

Homogeneous and dense arrays of nanowires are described. The nanowires can be formed in solution and can have average diameters of 40-300 nm and lengths of 1-3 .mu.m. They can be formed on any suitable substrate. Photovoltaic devices are also described.

Twin-mediated epitaxial growth of highly lattice-mismatched Cu/Ag core-shell nanowires.

PubMed

Weng, Wei-Lun; Hsu, Chin-Yu; Lee, Jheng-Syun; Fan, Hsin-Hsin; Liao, Chien-Neng

2018-05-31

Lattice-mismatch is an important factor for the heteroepitaxial growth of core-shell nanostructures. A large lattice-mismatch usually leads to a non-coherent interface or a polycrystalline shell layer. In this study, a conformal Ag layer is coated on Cu nanowires with dense nanoscale twin boundaries through a galvanic replacement reaction. Despite a large lattice mismatch between Ag and Cu (∼12.6%), the Ag shell replicates the twinning structure in Cu nanowires and grows epitaxially on the nanotwinned Cu nanowire. A twin-mediated growth mechanism is proposed to explain the epitaxy of high lattice-mismatch bimetallic systems in which the misfit dislocations are accommodated by coherent twin boundaries.

Photovoltaic Performance of a Nanowire/Quantum Dot Hybrid Nanostructure Array Solar Cell.

PubMed

Wu, Yao; Yan, Xin; Zhang, Xia; Ren, Xiaomin

2018-02-23

An innovative solar cell based on a nanowire/quantum dot hybrid nanostructure array is designed and analyzed. By growing multilayer InAs quantum dots on the sidewalls of GaAs nanowires, not only the absorption spectrum of GaAs nanowires is extended by quantum dots but also the light absorption of quantum dots is dramatically enhanced due to the light-trapping effect of the nanowire array. By incorporating five layers of InAs quantum dots into a 500-nm high-GaAs nanowire array, the power conversion efficiency enhancement induced by the quantum dots is six times higher than the power conversion efficiency enhancement in thin-film solar cells which contain the same amount of quantum dots, indicating that the nanowire array structure can benefit the photovoltaic performance of quantum dot solar cells.

Photovoltaic Performance of a Nanowire/Quantum Dot Hybrid Nanostructure Array Solar Cell

NASA Astrophysics Data System (ADS)

Wu, Yao; Yan, Xin; Zhang, Xia; Ren, Xiaomin

2018-02-01

An innovative solar cell based on a nanowire/quantum dot hybrid nanostructure array is designed and analyzed. By growing multilayer InAs quantum dots on the sidewalls of GaAs nanowires, not only the absorption spectrum of GaAs nanowires is extended by quantum dots but also the light absorption of quantum dots is dramatically enhanced due to the light-trapping effect of the nanowire array. By incorporating five layers of InAs quantum dots into a 500-nm high-GaAs nanowire array, the power conversion efficiency enhancement induced by the quantum dots is six times higher than the power conversion efficiency enhancement in thin-film solar cells which contain the same amount of quantum dots, indicating that the nanowire array structure can benefit the photovoltaic performance of quantum dot solar cells.

Facile synthesis of Ag@ZIF-8 core-shell heterostructure nanowires for improved antibacterial activities

NASA Astrophysics Data System (ADS)

Guo, Yu-Feng; Fang, Wei-Jun; Fu, Jie-Ru; Wu, Yun; Zheng, Jun; Gao, Gui-Qi; Chen, Cheng; Yan, Rui-Wen; Huang, Shou-Guo; Wang, Chun-Chang

2018-03-01

Compared with pure MOFs, core-shell heterostructures of noble-metal@MOFs have attracted tremendous interest due to their unique structure and extensive applications. In the present study, we have successfully synthesized well-defined core-shell Ag@ZIF-8 nanowires. The products growth process has been investigated by examining the products obtained at different intervals and the thickness of ZIF-8 shell ranging from 30 to 100 nm can be technically obtained by tuning the quantity of Ag nanowires. Ag@ZIF-8 has been proven to possess large specific surfaces and high thermal stability. Additionally, the antibacterial activity of Ag@ZIF-8 is further tested against Bacillus subtilis and Escherichia coli BL21. The results reveal that Ag@ZIF-8 core-shell heterostructure nanowires have effective activities against the two types of bacterial strains.

Geometrical optics, electrostatics, and nanophotonic resonances in absorbing nanowire arrays.

PubMed

Anttu, Nicklas

2013-03-01

Semiconductor nanowire arrays have shown promise for next-generation photovoltaics and photodetection, but enhanced understanding of the light-nanowire interaction is still needed. Here, we study theoretically the absorption of light in an array of vertical InP nanowires by moving continuously, first from the electrostatic limit to the nanophotonic regime and then to the geometrical optics limit. We show how the absorption per volume of semiconductor material in the array can be varied by a factor of 200, ranging from 10 times weaker to 20 times stronger than in a bulk semiconductor sample.

Three-dimensional electrodes for dye-sensitized solar cells: synthesis of indium-tin-oxide nanowire arrays and ITO/TiO2 core-shell nanowire arrays by electrophoretic deposition

NASA Astrophysics Data System (ADS)

Wang, Hong-Wen; Ting, Chi-Feng; Hung, Miao-Ken; Chiou, Chwei-Huann; Liu, Ying-Ling; Liu, Zongwen; Ratinac, Kyle R.; Ringer, Simon P.

2009-02-01

Dye-sensitized solar cells (DSSCs) show promise as a cheaper alternative to silicon-based photovoltaics for specialized applications, provided conversion efficiency can be maximized and production costs minimized. This study demonstrates that arrays of nanowires can be formed by wet-chemical methods for use as three-dimensional (3D) electrodes in DSSCs, thereby improving photoelectric conversion efficiency. Two approaches were employed to create the arrays of ITO (indium-tin-oxide) nanowires or arrays of ITO/TiO2 core-shell nanowires; both methods were based on electrophoretic deposition (EPD) within a polycarbonate template. The 3D electrodes for solar cells were constructed by using a doctor-blade for coating TiO2 layers onto the ITO or ITO/TiO2 nanowire arrays. A photoelectric conversion efficiency as high as 4.3% was achieved in the DSSCs made from ITO nanowires; this performance was better than that of ITO/TiO2 core-shell nanowires or pristine TiO2 films. Cyclic voltammetry confirmed that the reaction current was significantly enhanced when a 3D ITO-nanowire electrode was used. Better separation of charge carriers and improved charge transport, due to the enlarged interfacial area, are thought to be the major advantages of using 3D nanowire electrodes for the optimization of DSSCs.

Angle-dependent photodegradation over ZnO nanowire arrays on flexible paper substrates

PubMed Central

2014-01-01

In this study, we grew zinc oxide (ZnO) nanowire arrays on paper substrates using a two-step growth strategy. In the first step, we formed single-crystalline ZnO nanoparticles of uniform size distribution (ca. 4 nm) as seeds for the hydrothermal growth of the ZnO nanowire arrays. After spin-coating of these seeds onto paper, we grew ZnO nanowire arrays conformally on these substrates. The crystal structure of a ZnO nanowire revealed that the nanowires were single-crystalline and had grown along the c axis. Further visualization through annular bright field scanning transmission electron microscopy revealed that the hydrothermally grown ZnO nanowires possessed Zn polarity. From photocatalytic activity measurements of the ZnO nanowire (NW) arrays on paper substrate, we extracted rate constants of 0.415, 0.244, 0.195, and 0.08 s-1 for the degradation of methylene blue at incident angles of 0°, 30°, 60°, and 75°, respectively; that is, the photocatalytic activity of these ZnO nanowire arrays was related to the cosine of the incident angle of the UV light. Accordingly, these materials have promising applications in the design of sterilization systems and light-harvesting devices. PMID:25593556

Manipulation and Investigation of Uniformly-Spaced Nanowire Array on a Substrate via Dielectrophoresis and Electrostatic Interaction.

PubMed

Choi, U Hyeok; Park, Ji Hun; Kim, Jaekyun

2018-06-21

Directed-assembly of nanowires on the dielectrics-covered parallel electrode structure is capable of producing uniformly-spaced nanowire array at the electrode gap due to dielectrophoretic nanowire attraction and electrostatic nanowire repulsion. Beyond uniformly-spaced nanowire array formation, the control of spacing in the array is beneficial in that it should be the experimental basis of the precise positioning of functional nanowires on a circuit. Here, we investigate the material parameters and bias conditions to modulate the nanowire spacing in the ordered array, where the nanowire array formation is readily attained due to the electrostatic nanowire interaction. A theoretical model for the force calculation and the simulation of the induced charge in the assembled nanowire verifies that the longer nanowires on thicker dielectric layer tend to be assembled with a larger pitch due to the stronger nanowire-nanowire electrostatic repulsion, which is consistent with the experimental results. It was claimed that the stronger dielectrophoretic force is likely to attract more nanowires that are suspended in solution at the electrode gap, causing them to be less-spaced. Thus, we propose a generic mechanism, competition of dielectrophoretic and electrostatic force, to determine the nanowire pitch in an ordered array. Furthermore, this spacing-controlled nanowire array offers a way to fabricate the high-density nanodevice array without nanowire registration.

A force sensor using nanowire arrays to understand biofilm formation (Conference Presentation)

NASA Astrophysics Data System (ADS)

Sahoo, Prasana K.; Cavalli, Alessandro; Pelegati, Vitor B.; Murillo, Duber M.; Souza, Alessandra A.; Cesar, Carlos L.; Bakkers, Erik P. A. M.; Cotta, Monica A.

2016-03-01

Understanding the cellular signaling and function at the nano-bio interface can pave the way towards developing next-generation smart diagnostic tools. From this perspective, limited reports detail so far the cellular and subcellular forces exerted by bacterial cells during the interaction with abiotic materials. Nanowire arrays with high aspect ratio have been used to detect such small forces. In this regard, live force measurements were performed ex-vivo during the interaction of Xylella fastidiosa bacterial cells with InP nanowire arrays. The influence of nanowire array topography and surface chemistry on the response and motion of bacterial cells was studied in detail. The nanowire arrays were also functionalized with different cell adhesive promoters, such as amines and XadA1, an afimbrial protein of X.fastidiosa. By employing the well-defined InP nanowire arrays platform, and single cell confocal imaging system, we were able to trace the bacterial growth pattern, and show that their initial attachment locations are strongly influenced by the surface chemistry and nanoscale surface topography. In addition, we measure the cellular forces down to few nanonewton range using these nanowire arrays. In case of nanowire functionalized with XadA1, the force exerted by vertically and horizontally attached single bacteria on the nanowire is in average 14% and 26% higher than for the pristine array, respectively. These results provide an excellent basis for live-cell force measurements as well as unravel the range of forces involved during the early stages of bacterial adhesion and biofilm formation.

Assembly of Nanowire Arrays: Exploring Interparticle Interactions, Particle Orientation, and Mixed Particle Arrays

NASA Astrophysics Data System (ADS)

Kirby, David J.

This dissertation explores the fundamental interparticle and particle-substrate forces that contribute to nanowire assembly. Nanowires have a large aspect ratio which has made them favorable materials for applications in energy and sensing technologies. However, this anisotropy means that nanowires must be positioned and oriented during an assembly process. Within this work, the roles of gravity, van der Waals (VDW) attractions, and electrostatic repulsions are explored when different nanowire assemblies are created. Particles were synthesized by the template electrodeposition process so that stripes of different materials and therefore different VDW interactions could be patterned along the particle length. Electrostatic repulsions were provided by a small molecule coating or a porous silica shell to prevent aggregation during the assembly process. Chapters 2, 3, 5, 6, and 8 all used particles whose asymmetry was further adjusted by removal of a sacrificial segment to leave a partially etched nanowire (PEN), a rigid silica shell partially filled with a metal core. For these particles, the role of gravity was amplified due to the drastic density differences between the two segments. Topographic and high VDW surface interactions were patterned onto assembly substrates using photolithographic processing. These forces served as a passive template to direct nanowire assembly. The segment anisotropy of PENs allowed gravity to drive their sedimentation with the long axis perpendicular to the surface. The density difference between the two ends allowed them to convert between the horizontal and vertical orientation as they diffused on the substrate. Vertical arrays formed as particle concentrations increased while VDW attractions from neighboring PENs or the physical barrier of a microwell wall supported this structure. While vertical arrays were typically PENs, microwell walls were also able to enforce a vertical orientation on solid Au nanowires. These particles

Magnetic-optical bifunctional CoPt3/Co multilayered nanowire arrays

NASA Astrophysics Data System (ADS)

Su, Yi-Kun; Yan, Zhi-Long; Wu, Xi-Ming; Liu, Huan; Ren, Xiao; Yang, Hai-Tao

2015-10-01

CoPt3/Co multilayered nanowire (NW) arrays are synthesized by pulsed electrodeposition into nanoporous anodic aluminum oxide (AAO) templates. The electrochemistry deposition parameters are determined by cyclic voltammetry to realize the well control of the ratio of Co to Pt and the length of every segment. The x-ray diffraction (XRD) patterns show that both Co and CoPt3 NWs exhibit face-centered cubic (fcc) structures. In the UV-visible absorption spectra, CoPt3/Co NW arrays show a red-shift with respect to pure CoPt3NWs. Compared with the pure Co nanowire arrays, the CoPt3/Co multilayered nanowire arrays show a weak shape anisotropy and well-modulated magnetic properties. CoPt3/Co multilayered nanowires are highly encouraging that new families of bimetallic nanosystems may be developed to meet the needs of nanomaterials in emerging multifunctional nanotechnologies. Project supported by the National Natural Science Foundation of China (Grant Nos. 51472165, 51471185, and 11274370).

Silicon nanowire arrays as thermoelectric material for a power microgenerator

NASA Astrophysics Data System (ADS)

Dávila, D.; Tarancón, A.; Fernández-Regúlez, M.; Calaza, C.; Salleras, M.; San Paulo, A.; Fonseca, L.

2011-10-01

A novel design of a silicon-based thermoelectric power microgenerator is presented in this work. Arrays of silicon nanowires, working as thermoelectric material, have been integrated in planar uni-leg thermocouple microstructures to convert waste heat into electrical energy. Homogeneous, uniformly dense, well-oriented and size-controlled arrays of silicon nanowires have been grown by chemical vapor deposition using the vapor-liquid-solid mechanism. Compatibility issues between the nanowire growth method and microfabrication techniques, such as electrical contact patterning, are discussed. Electrical measurements of the nanowire array electrical conductivity and the Seebeck voltage induced by a controlled thermal gradient or under harvesting operation mode have been carried out to demonstrate the feasibility of the microdevice. A resistance of 240 Ω at room temperature was measured for an array of silicon nanowires 10 µm -long, generating a Seebeck voltage of 80 mV under an imposed thermal gradient of 450 °C, whereas only 4.5 mV were generated under a harvesting operation mode. From the results presented, a Seebeck coefficient of about 150-190 µV K-1 was estimated, which corresponds to typical values for bulk silicon.

A general melt-injection-decomposition route to oriented metal oxide nanowire arrays

NASA Astrophysics Data System (ADS)

Han, Dongqiang; Zhang, Xinwei; Hua, Zhenghe; Yang, Shaoguang

2016-12-01

In this manuscript, a general melt-injection-decomposition (MID) route has been proposed and realized for the fabrication of oriented metal oxide nanowire arrays. Nitrate was used as the starting materials, which was injected into the nanopores of the anodic aluminum oxide (AAO) membrane through the capillarity action in its liquid state. At higher temperature, the nitrate decomposed into corresponding metal oxide within the nanopores of the AAO membrane. Oriented metal oxide nanowire arrays were formed within the AAO membrane as a result of the confinement of the nanopores. Four kinds of metal oxide (CuO, Mn2O3, Co3O4 and Cr2O3) nanowire arrays are presented here as examples fabricated by this newly developed process. X-ray diffraction, scanning electron microscopy and transmission electron microscopy studies showed clear evidence of the formations of the oriented metal oxide nanowire arrays. Formation mechanism of the metal oxide nanowire arrays is discussed based on the Thermogravimetry and Differential Thermal Analysis measurement results.

A Preliminary Study on the Synthesis and Characterization of Multilayered Ag/Co Magnetic Nanowires Fabricated via the Electrodeposition Method

PubMed Central

Peng, Cheng-Hsiung; Wu, Tsung-Yung; Hwang, Chyi-Ching

2013-01-01

A single-bath electrodeposition method was developed to integrate multilayer Ag/Co nanowires with a commercial anodic alumina oxide (AAO) template with a pore diameter of 100–200 nm. An electrolyte system containing silver nitride and cobalt sulfide was studied using cyclic voltammetry, and the electrodeposition rate was varied to optimize the electrodeposition conditions. A constant stepwise potential and a variable cation ratio of [Co2+]/[Ag+] were used during electrodeposition. After the dissolution of the template in aqueous NaOH solution, multilayered Ag/Co nanowires were obtained with a composition of [Co]/[Ag80Co20], as identified by XRD and TEM, when [Co2+]/[Ag+] = 150. By annealing at 200°C for 1 h, uniformly structured (Co99.57/Ag100) nanowires were obtained. Compared with pure Co nanowires, the magnetic hysteresis loops showed a greater magnetic anisotropy for (Co99.57/Ag100) nanowires than for pure Co nanowires, corresponding to a change in the easy axis upon magnetization. PMID:24072985

Ferromagnetic resonance in low interacting permalloy nanowire arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raposo, V.; Zazo, M.; Flores, A. G.

2016-04-14

Dipolar interactions on magnetic nanowire arrays have been investigated by various techniques. One of the most powerful techniques is the ferromagnetic resonance spectroscopy, because the resonance field depends directly on the anisotropy field strength and its frequency dependence. In order to evaluate the influence of magnetostatic dipolar interactions among ferromagnetic nanowire arrays, several densely packed hexagonal arrays of NiFe nanowires have been prepared by electrochemical deposition filling self-ordered nanopores of alumina membranes with different pore sizes but keeping the same interpore distance. Nanowires’ diameter was changed from 90 to 160 nm, while the lattice parameter was fixed to 300 nm, which wasmore » achieved by carefully reducing the pore diameter by means of Atomic Layer Deposition of conformal Al{sub 2}O{sub 3} layers on the nanoporous alumina templates. Field and frequency dependence of ferromagnetic resonance have been studied in order to obtain the dispersion diagram which gives information about anisotropy, damping factor, and gyromagnetic ratio. The relationship between resonance frequency and magnetic field can be explained by the roles played by the shape anisotropy and dipolar interactions among the ferromagnetic nanowires.« less

A High-Efficiency Si Nanowire Array/Perovskite Hybrid Solar Cell.

PubMed

Yan, Xin; Zhang, Chen; Wang, Jiamin; Zhang, Xia; Ren, Xiaomin

2017-12-01

A low-cost Si nanowire array/perovskite hybrid solar cell is proposed and simulated. The solar cell consists of a Si p-i-n nanowire array filled with CH 3 NH 3 PbI 3 , in which both the nanowires and perovskite absorb the incident light while the nanowires act as the channels for transporting photo-generated electrons and holes. The hybrid structure has a high absorption efficiency in a broad wavelength range of 300~800 nm. A large short-circuit current density of 28.8 mA/cm 2 and remarkable conversion efficiency of 13.3% are obtained at a thin absorber thickness of 1.6 μm, which are comparable to the best results of III-V nanowire solar cells.

MnO 2 nanotube and nanowire arrays by electrochemical deposition for supercapacitors

NASA Astrophysics Data System (ADS)

Xia, Hui; Feng, Jinkui; Wang, Hailong; Lai, Man On; Lu, Li

Highly ordered MnO 2 nanotube and nanowire arrays are successfully synthesized via a electrochemical deposition technique using porous alumina templates. The morphologies and microstructures of the MnO 2 nanotube and nanowire arrays are investigated by field emission scanning electron microscopy and transmission electron microscopy. Electrochemical characterization demonstrates that the MnO 2 nanotube array electrode has superior capacitive behaviour to that of the MnO 2 nanowire array electrode. In addition to high specific capacitance, the MnO 2 nanotube array electrode also exhibits good rate capability and good cycling stability, which makes it promising candidate for supercapacitors.

Electronic transport properties of single-crystal bismuth nanowire arrays

NASA Astrophysics Data System (ADS)

Zhang, Zhibo; Sun, Xiangzhong; Dresselhaus, M. S.; Ying, Jackie Y.; Heremans, J.

2000-02-01

We present here a detailed study of the electrical transport properties of single-crystal bismuth nanowire arrays embedded in a dielectric matrix. Measurements of the resistance of Bi nanowire arrays with different wire diameters (60-110 nm) have been carried out over a wide range of temperatures (2.0-300 K) and magnetic fields (0-5.4 T). The transport properties of a heavily Te-doped Bi nanowire array have also been studied. At low temperatures, we show that the wire boundary scattering is the dominant scattering process for carriers in the undoped single-crystal Bi nanowires, while boundary scattering is less important for a heavily Te-doped sample, consistent with general theoretical considerations. The temperature dependences of the zero-field resistivity and of the longitudinal magneto-coefficient of the Bi nanowires were also studied and were found to be sensitive to the wire diameter. The quantum confinement of carriers is believed to play an important role in determining the overall temperature dependence of the zero-field resistivity. Theoretical considerations of the quantum confinement effects on the electronic band structure and on the transport properties of Bi nanowires are discussed. Despite the evidence for localization effects and diffusive electron interactions at low temperatures (T<=4.0 K), localization effects are not the dominant mechanisms affecting the resistivity or the magnetoresistance in the temperature range of this study.

Quantum dots coupled ZnO nanowire-array panels and their photocatalytic activities.

PubMed

Liao, Yulong; Que, Wenxiu; Zhang, Jin; Zhong, Peng; Yuan, Yuan; Qiu, Xinku; Shen, Fengyu

2013-02-01

Fabrication and characterization of a heterojunction structured by CdS quantum dots@ZnO nanowire-array panels were presented. Firstly, ZnO nanowire-array panels were prepared by using a chemical bath deposition approach where wurtzite ZnO nanowires with a diameter of about 100 nm and 3 microm in length grew perpendicularly to glass substrate. Secondly, CdS quantum dots were deposited onto the surface of the ZnO nanowire-arrays by using successive ion layer absorption and reaction method, and the CdS shell/ZnO core heterojunction were thus obtained. Field emission scanning electron microscopy and transmission electron microscope were employed to characterize the morphological properties of the as-obtained CdS quantum dots@ZnO nanowire-array panels. X-ray diffraction was adopted to characterize the crystalline properties of the as-obtained CdS quantum dots@ZnO nanowire-array panels. Methyl orange was taken as a model compound to confirm the photocatalytic activities of the CdS shell/ZnO core heterojunction. Results indicate that CdS with narrow band gap not only acts as a visible-light sensitizer but also is responsible for an effective charge separation.

Study of spin dynamics and damping on the magnetic nanowire arrays with various nanowire widths

NASA Astrophysics Data System (ADS)

Cho, Jaehun; Fujii, Yuya; Konioshi, Katsunori; Yoon, Jungbum; Kim, Nam-Hui; Jung, Jinyong; Miwa, Shinji; Jung, Myung-Hwa; Suzuki, Yoshishige; You, Chun-Yeol

2016-07-01

We investigate the spin dynamics including Gilbert damping in the ferromagnetic nanowire arrays. We have measured the ferromagnetic resonance of ferromagnetic nanowire arrays using vector-network analyzer ferromagnetic resonance (VNA-FMR) and analyzed the results with the micromagnetic simulations. We find excellent agreement between the experimental VNA-FMR spectra and micromagnetic simulations result for various applied magnetic fields. We find that the same tendency of the demagnetization factor for longitudinal and transverse conditions, Nz (Ny) increases (decreases) as increasing the nanowire width in the micromagnetic simulations while Nx is almost zero value in transverse case. We also find that the Gilbert damping constant increases from 0.018 to 0.051 as the increasing nanowire width for the transverse case, while it is almost constant as 0.021 for the longitudinal case.

High energy density in PVDF nanocomposites using an optimized nanowire array.

PubMed

Guo, Ru; Luo, Hang; Liu, Weiwei; Zhou, Xuefan; Tang, Lin; Zhou, Kechao; Zhang, Dou

2018-06-22

TiO2 nanowire arrays are often utilized to prepare high performance polymer nanocomposites, however, the contribution to the energy density is limited due to their non-ferroelectric characteristics. A nanocomposite with an optimized nanowire array combining the ferroelectric properties of lead zirconate titanate (PZT) with TiO2, readily forming nanowires (denoted as a TiO2-P nanowire array), is prepared to enhance the permittivity. Poly(vinylidene fluoride) (PVDF) is used as the polymer matrix due to its high breakdown strength, e.g. 600-700 kV mm-1. As a result, the permittivity and breakdown electric field reach 53 at 1 kHz and 550 kV mm-1, respectively. Therefore, the nanocomposites achieve a higher discharge energy density of 12.4 J cm-3 with excellent cycle stability, which is the highest among nanocomposites based on a nanowire array as a filler in a PVDF matrix. This work provides not only a feasible approach to obtain high performance dielectric nanocomposites, but also a wide range of potential applications in the energy storage and energy harvesting fields.

The microstructure and magnetic properties of Cu/CuO/Ni core/multi-shell nanowire arrays

NASA Astrophysics Data System (ADS)

Yang, Feng; Shi, Jie; Zhang, Xiaofeng; Hao, Shijie; Liu, Yinong; Feng, Chun; Cui, Lishan

2018-04-01

Multifunctional metal/oxide/metal core/multi-shell nanowire arrays were prepared mostly by physical or chemical vapor deposition. In our study, the Cu/CuO/Ni core/multi-shell nanowire arrays were prepared by AAO template-electrodeposition and oxidation processes. The Cu/Ni core/shell nanowire arrays were prepared by AAO template-electrodeposition method. The microstructure and chemical compositions of the core/multi-shell nanowires and core/shell nanowires have been characterized using transmission electron microscopy with HADDF-STEM and X-ray diffraction. Magnetization measurements revealed that the Cu/CuO/Ni and Cu/Ni nanowire arrays have high coercivity and remanence ratio.

Synthesis and characterization of axial heterojunction inorganic-organic semiconductor nanowire arrays.

PubMed

Chen, Nan; Qian, Xuemin; Lin, Haowei; Liu, Huibiao; Li, Yongjun; Li, Yuliang

2011-11-07

The end-to-end P-N heterojunction nanowire arrays combined organic (poly[1,4-bis(pyrrol-2-yl)benzene], BPB) and inorganic (CdS) molecules have been successfully designed and fabricated. The electrical properties of P-N heterojunctions of organic-inorganic nanowire arrays were investigated. The diode nature and rectifying feature of P-N heterojunction nanowire arrays were observed. The rectification ratio of the diode increased from 29.9 to 129.7 as the illumination intensity increased. The material exhibits a new property, which is an improvement in the integration of the physical and chemical properties of the two independent components.

High conductive and scalable Ag nanowires flexible transparent electrode by nanowelding with physical methods

NASA Astrophysics Data System (ADS)

He, W. W.; Yan, X. H.; Long, Y. F.; Liang, Y. M.; Pan, C.; Zhao, J. L.; Liu, Q. X.

2017-09-01

Transparent electrodes (TEs) are very important for electronic devices. At present, ITO is gaining the largest market share but will be reduced. Ag nanowires (AgNWs) TEs is acknowledged as one of the most potential alternative to ITO. However, AgNWs TEs still have electrical problems because of the low contact between the AgNWs. In this paper, we report three physics methods to increase the conductivity of AgNWs TEs by nanowelding the contact of nanowires. For heat-resistant materials, 200 °C heat-nanowelding can help to reduce the sheet resistance by 96.7%. For pressure resistant materials, 20MPa pressure-nanowelding can help to increase the conductivity by 98.7%. And the transmittance (>90%) remains constant during the above process. Yet, both of these methods cannot improve the adhesion between nanowires and the substrates. Luckily, tight adhesion can be obtained by overcoating a PEDOT: PSS lalyer on AgNWs film which can reduce the sheet resistance by 87.8%. This means that things are usually not perfect, and they have their own advantages and lay the foundation for the popularization and application of AgNWs TEs. In a word, these three nano-welding methods are all suit for manufacture on a large scale for high conductive AgNWs TEs.

Stretchable Conductive Composites from Cu-Ag Nanowire Felt.

PubMed

Catenacci, Matthew J; Reyes, Christopher; Cruz, Mutya A; Wiley, Benjamin J

2018-04-24

Materials that retain a high conductivity under strain are essential for wearable electronics. This article describes a conductive, stretchable composite consisting of a Cu-Ag core-shell nanowire felt infiltrated with a silicone elastomer. This composite exhibits a retention of conductivity under strain that is superior to any composite with a conductivity greater than 1000 S cm -1 . This work also shows how the mechanical properties, conductivity, and deformation mechanism of the composite changes as a function of the stiffness of the silicone matrix. The retention of conductivity under strain was found to decrease as the Young's modulus of the matrix increased. This was attributed to void formation as a result of debonding between the nanowire felt and the elastomer. The nanowire composite was also patterned to create serpentine circuits with a stretchability of 300%.

Speedy fabrication of diameter-controlled Ag nanowires using glycerolunder microwave irradiation conditions

EPA Science Inventory

Diameter-controlled Ag nanowires were rapidly fabricated (1 min) using inexpensive, abundant, and environmentally-friendly glycerol as both reductant and solvent under non-stirred microwave irradiation conditions; no Ag particles were formed using conventional heating methods. Th...

Fully Tunable Silicon Nanowire Arrays Fabricated by Soft Nanoparticle Templating.

PubMed

Rey, By Marcel; Elnathan, Roey; Ditcovski, Ran; Geisel, Karen; Zanini, Michele; Fernandez-Rodriguez, Miguel-Angel; Naik, Vikrant V; Frutiger, Andreas; Richtering, Walter; Ellenbogen, Tal; Voelcker, Nicolas H; Isa, Lucio

2016-01-13

We demonstrate a fabrication breakthrough to produce large-area arrays of vertically aligned silicon nanowires (VA-SiNWs) with full tunability of the geometry of the single nanowires and of the whole array, paving the way toward advanced programmable designs of nanowire platforms. At the core of our fabrication route, termed "Soft Nanoparticle Templating", is the conversion of gradually compressed self-assembled monolayers of soft nanoparticles (microgels) at a water-oil interface into customized lithographical masks to create VA-SiNW arrays by means of metal-assisted chemical etching (MACE). This combination of bottom-up and top-down techniques affords excellent control of nanowire etching site locations, enabling independent control of nanowire spacing, diameter and height in a single fabrication route. We demonstrate the fabrication of centimeter-scale two-dimensional gradient photonic crystals exhibiting continuously varying structural colors across the entire visible spectrum on a single silicon substrate, and the formation of tunable optical cavities supported by the VA-SiNWs, as unambiguously demonstrated through numerical simulations. Finally, Soft Nanoparticle Templating is combined with optical lithography to create hierarchical and programmable VA-SiNW patterns.

Construction of 3D Metallic Nanowire Arrays on Arbitrarily-Shaped Substrate.

NASA Astrophysics Data System (ADS)

Chen, Fei; Li, Jingning; Yu, Fangfang; Peng, Ru-Wen; Wang, Mu; Mu Wang Team

Formation of three-dimensional (3D) nanostructures is an important step of advanced manufacture for new concept devices with novel functionality. Despite of great achievements in fabricating nanostructures with state of the art lithography approaches, these nanostructures are normally limited on flat substrates. Up to now it remains challenging to build metallic nanostructures directly on a rough and bumpy surface. Here we demonstrate a unique approach to fabricate metallic nanowire arrays on an arbitrarily-shaped surface by electrodeposition, which is unknown before 2016. Counterintuitively here the growth direction of the nanowires is perpendicular to their longitudinal axis, and the specific geometry of nanowires can be achieved by introducing specially designed shaped substrate. The spatial separation and the width of the nanowires can be tuned by voltage, electrolyte concentration and temperature in electrodeposition. By taking cobalt nanowire array as an example, we demonstrate that head-to-head and tail-to-tail magnetic domain walls can be easily introduced and modulated in the nanowire arrays, which is enlightening to construct new devices such as domain wall racetrack memory. We acknowledge the foundation from MOST and NSF(China).

MBE growth of GaAs and InAs nanowires using colloidal Ag nanoparticles

NASA Astrophysics Data System (ADS)

Ilkiv, I. V.; Reznik, R. R.; Kotlyar, K. P.; Bouravleuv, A. D.; Cirlin, G. E.

2017-11-01

Ag colloidal nanoparticles were used as a catalyst for molecular beam epitaxy of GaAs and InAs nanowires on the Si(111) substrates. The scanning electron microscopy measurements revealed that nanowires obtained are uniform and have small size distribution.

Enhanced ionic conductivity of AgI nanowires/AAO composites fabricated by a simple approach.

PubMed

Liu, Li-Feng; Lee, Seung-Woo; Li, Jing-Bo; Alexe, Marin; Rao, Guang-Hui; Zhou, Wei-Ya; Lee, Jae-Jong; Lee, Woo; Gösele, Ulrich

2008-12-10

AgI nanowires/anodic aluminum oxide (AgI NWs/AAO) composites have been fabricated by a simple approach, which involves the thermal melting of AgI powders on the surface of the AAO membrane, followed by the infiltration of the molten AgI inside the nanochannels. As-prepared AgI nanowires have corrugated outer surfaces and are polycrystalline according to scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. X-ray diffraction (XRD) shows that a considerable amount of 7H polytype AgI exists in the composites, which is supposed to arise from the interfacial interactions between the embedded AgI and the alumina. AC conductivity measurements for the AgI nanowires/AAO composites exhibit a notable conductivity enhancement by three orders of magnitude at room temperature compared with that of pristine bulk AgI. Furthermore, a large conductivity hysteresis and abnormal conductivity transitions were observed in the temperature-dependent conductivity measurements, from which an ionic conductivity as high as 8.0 × 10(2) Ω(-1) cm(-1) was obtained at around 70 °C upon cooling. The differential scanning calorimetry (DSC) result demonstrates a similar phase transition behavior as that found in the AC conductivity measurements. The enhanced ionic conductivity, as well as the abnormal phase transitions, can be explained in terms of the existence of the highly conducting 7H polytype AgI and the formation of well-defined conduction paths in the composites.

Electrodeposition of bismuth:tellurium nanowire arrays into porous alumina templates for thermoelectric applications

NASA Astrophysics Data System (ADS)

Trahey, Lynn

Bismuth telluride is a well-known thermoelectric material for refrigeration applications. Thermoelectrics possess several advantages over conventional refrigeration and power generation devices, yet are not widely-used due to low efficiencies. It has been predicted and shown experimentally that the efficiency of thermoelectric devices increases when the semiconducting materials have reduced dimensions. Therefore, the aim of this research was to show enhanced thermoelectric efficiency in one-dimensional nanowires. The nanowires were synthesized via electrochemical deposition into porous alumina templates. Electrodeposition is a versatile technique that ensures electrical continuity in the deposited material. The nanowire templates, porous alumina, were made by the double anodization of high-purity aluminum foil in oxalic acid solutions. This technique produces parallel, hexagonally packed, and nanometer-range diameter pores that can reach high aspect ratios (greater than 2000:1). The main anodization variables (electrolyte concentration, applied potential, 2nd anodization time, and temperature) were studied systematically in order to deconvolute their effects on the resulting pores and to obtain high aspect ratio pores. The porous alumina is of great importance because the pore dimensions determine the dimensions of the electrodeposited nanowires, which influence the thermoelectric performance of the nanowire arrays. Nanowire arrays were characterized in several ways. Powder X-ray diffraction was used to assess crystallinity and preferred orientation of the nanowires, revealing that the nanowires are highly crystalline and grow with strong preferred orientation such that the material is suited for optimal thermoelectric performance. Scanning electron microscopy was used to evaluate the nanowire nucleation percentage and growth-front uniformity, both of which were enhanced by pulsed-potential electrodeposition. Compositional analysis via electron microprobe indicates

Toward optimized light utilization in nanowire arrays using scalable nanosphere lithography and selected area growth.

PubMed

Madaria, Anuj R; Yao, Maoqing; Chi, Chunyung; Huang, Ningfeng; Lin, Chenxi; Li, Ruijuan; Povinelli, Michelle L; Dapkus, P Daniel; Zhou, Chongwu

2012-06-13

Vertically aligned, catalyst-free semiconducting nanowires hold great potential for photovoltaic applications, in which achieving scalable synthesis and optimized optical absorption simultaneously is critical. Here, we report combining nanosphere lithography (NSL) and selected area metal-organic chemical vapor deposition (SA-MOCVD) for the first time for scalable synthesis of vertically aligned gallium arsenide nanowire arrays, and surprisingly, we show that such nanowire arrays with patterning defects due to NSL can be as good as highly ordered nanowire arrays in terms of optical absorption and reflection. Wafer-scale patterning for nanowire synthesis was done using a polystyrene nanosphere template as a mask. Nanowires grown from substrates patterned by NSL show similar structural features to those patterned using electron beam lithography (EBL). Reflection of photons from the NSL-patterned nanowire array was used as a measure of the effect of defects present in the structure. Experimentally, we show that GaAs nanowires as short as 130 nm show reflection of <10% over the visible range of the solar spectrum. Our results indicate that a highly ordered nanowire structure is not necessary: despite the "defects" present in NSL-patterned nanowire arrays, their optical performance is similar to "defect-free" structures patterned by more costly, time-consuming EBL methods. Our scalable approach for synthesis of vertical semiconducting nanowires can have application in high-throughput and low-cost optoelectronic devices, including solar cells.

Template-assisted fabrication of tin and antimony based nanowire arrays

NASA Astrophysics Data System (ADS)

Zaraska, Leszek; Kurowska, Elżbieta; Sulka, Grzegorz D.; Jaskuła, Marian

2012-10-01

Antimony nanowires with diameters ranging from 35 nm to 320 nm were successfully prepared by simple, galvanostatic electrodeposition inside the pores of anodic alumina membranes from a citrate based electrolyte. The use of the potassium antimonyl tartrate electrolyte for electrodeposition results in the formation of Sb/Sb2O3 nanowires. The structural features of the nanowire arrays were investigated by FE-SEM, and the nanowire composition was confirmed by EDS and XRD measurements. A distinct peak at about 27.5° in the XRD pattern recorded for nanowires formed in the tartrate electrolyte was attributed to the presence of co-deposited Sb2O3. Three types of dense arrays of Sn-SnSb nanowires with diameters ranging from 82 nm to 325 nm were also synthesized by DC galvanostatic electrodeposition into the anodic aluminum oxide (AAO) membranes for the first time. Only Sn and SnSb peaks appeared in the XRD pattern and both phases seem to have a relatively high degree of crystallinity. The influence of current density applied during electrodeposition on the composition of nanowires was investigated. It was found that the Sb content in fabricated nanowires decreases with increasing current density. The diameters of all synthesized nanowires roughly correspond to the dimensions of the nanochannels of AAO templates used for electrodeposition.

Crystallographic alignment of high-density gallium nitride nanowire arrays.

PubMed

Kuykendall, Tevye; Pauzauskie, Peter J; Zhang, Yanfeng; Goldberger, Joshua; Sirbuly, Donald; Denlinger, Jonathan; Yang, Peidong

2004-08-01

Single-crystalline, one-dimensional semiconductor nanostructures are considered to be one of the critical building blocks for nanoscale optoelectronics. Elucidation of the vapour-liquid-solid growth mechanism has already enabled precise control over nanowire position and size, yet to date, no reports have demonstrated the ability to choose from different crystallographic growth directions of a nanowire array. Control over the nanowire growth direction is extremely desirable, in that anisotropic parameters such as thermal and electrical conductivity, index of refraction, piezoelectric polarization, and bandgap may be used to tune the physical properties of nanowires made from a given material. Here we demonstrate the use of metal-organic chemical vapour deposition (MOCVD) and appropriate substrate selection to control the crystallographic growth directions of high-density arrays of gallium nitride nanowires with distinct geometric and physical properties. Epitaxial growth of wurtzite gallium nitride on (100) gamma-LiAlO(2) and (111) MgO single-crystal substrates resulted in the selective growth of nanowires in the orthogonal [1\\[Evec]0] and [001] directions, exhibiting triangular and hexagonal cross-sections and drastically different optical emission. The MOCVD process is entirely compatible with the current GaN thin-film technology, which would lead to easy scale-up and device integration.

Uniaxial Magnetization Performance of Textured Fe Nanowire Arrays Electrodeposited by a Pulsed Potential Deposition Technique

NASA Astrophysics Data System (ADS)

Neetzel, C.; Ohgai, T.; Yanai, T.; Nakano, M.; Fukunaga, H.

2017-11-01

Textured ferromagnetic Fe nanowire arrays were electrodeposited using a rectangular-pulsed potential deposition technique into anodized aluminum oxide nanochannels. During the electrodeposition of Fe nanowire arrays at a cathodic potential of - 1.2 V, the growth rate of the nanowires was ca. 200 nm s-1. The aspect ratio of Fe nanowires with a diameter of 30 ± 5 nm reached ca. 2000. The long axis of Fe nanowires corresponded with the <200> direction when a large overpotential during the on-time pulse was applied, whereas it orientated to the <110> direction under the potentiostatic condition with a small overpotential. By shifting the on-time cathode potential up to - 1.8 V, the texture coefficient for the (200) plane, TC200, reached up to 1.94. Perpendicular magnetization performance was observed in Fe nanowire arrays. With increasing TC200, the squareness of Fe nanowire arrays increased up to 0.95 with the coercivity maintained at 1.4 kOe at room temperature. This research result has opened a novel possibility of Fe nanowire arrays that can be applied for a new permanent magnetic material without rare-earth metals.

Si/InGaN core/shell hierarchical nanowire arrays and their photoelectrochemical properties.

PubMed

Hwang, Yun Jeong; Wu, Cheng Hao; Hahn, Chris; Jeong, Hoon Eui; Yang, Peidong

2012-03-14

Three-dimensional hierarchical nanostructures were synthesized by the halide chemical vapor deposition of InGaN nanowires on Si wire arrays. Single phase InGaN nanowires grew vertically on the sidewalls of Si wires and acted as a high surface area photoanode for solar water splitting. Electrochemical measurements showed that the photocurrent density with hierarchical Si/InGaN nanowire arrays increased by 5 times compared to the photocurrent density with InGaN nanowire arrays grown on planar Si (1.23 V vs RHE). High-resolution transmission electron microscopy showed that InGaN nanowires are stable after 15 h of illumination. These measurements show that Si/InGaN hierarchical nanostructures are a viable high surface area electrode geometry for solar water splitting. © 2012 American Chemical Society

Ag/Au/Polypyrrole Core-shell Nanowire Network for Transparent, Stretchable and Flexible Supercapacitor in Wearable Energy Devices

NASA Astrophysics Data System (ADS)

Moon, Hyunjin; Lee, Habeom; Kwon, Jinhyeong; Suh, Young Duk; Kim, Dong Kwan; Ha, Inho; Yeo, Junyeob; Hong, Sukjoon; Ko, Seung Hwan

2017-02-01

Transparent and stretchable energy storage devices have attracted significant interest due to their potential to be applied to biocompatible and wearable electronics. Supercapacitors that use the reversible faradaic redox reaction of conducting polymer have a higher specific capacitance as compared with electrical double-layer capacitors. Typically, the conducting polymer electrode is fabricated through direct electropolymerization on the current collector. However, no research have been conducted on metal nanowires as current collectors for the direct electropolymerization, even though the metal nanowire network structure has proven to be superior as a transparent, flexible, and stretchable electrode platform because the conducting polymer’s redox potential for polymerization is higher than that of widely studied metal nanowires such as silver and copper. In this study, we demonstrated a highly transparent and stretchable supercapacitor by developing Ag/Au/Polypyrrole core-shell nanowire networks as electrode by coating the surface of Ag NWs with a thin layer of gold, which provide higher redox potential than the electropolymerizable monomer. The Ag/Au/Polypyrrole core-shell nanowire networks demonstrated superior mechanical stability under various mechanical bending and stretching. In addition, proposed supercapacitors showed fine optical transmittance together with fivefold improved areal capacitance compared to pristine Ag/Au core-shell nanowire mesh-based supercapacitors.

Ag/Au/Polypyrrole Core-shell Nanowire Network for Transparent, Stretchable and Flexible Supercapacitor in Wearable Energy Devices

PubMed Central

Moon, Hyunjin; Lee, Habeom; Kwon, Jinhyeong; Suh, Young Duk; Kim, Dong Kwan; Ha, Inho; Yeo, Junyeob; Hong, Sukjoon; Ko, Seung Hwan

2017-01-01

Transparent and stretchable energy storage devices have attracted significant interest due to their potential to be applied to biocompatible and wearable electronics. Supercapacitors that use the reversible faradaic redox reaction of conducting polymer have a higher specific capacitance as compared with electrical double-layer capacitors. Typically, the conducting polymer electrode is fabricated through direct electropolymerization on the current collector. However, no research have been conducted on metal nanowires as current collectors for the direct electropolymerization, even though the metal nanowire network structure has proven to be superior as a transparent, flexible, and stretchable electrode platform because the conducting polymer’s redox potential for polymerization is higher than that of widely studied metal nanowires such as silver and copper. In this study, we demonstrated a highly transparent and stretchable supercapacitor by developing Ag/Au/Polypyrrole core-shell nanowire networks as electrode by coating the surface of Ag NWs with a thin layer of gold, which provide higher redox potential than the electropolymerizable monomer. The Ag/Au/Polypyrrole core-shell nanowire networks demonstrated superior mechanical stability under various mechanical bending and stretching. In addition, proposed supercapacitors showed fine optical transmittance together with fivefold improved areal capacitance compared to pristine Ag/Au core-shell nanowire mesh-based supercapacitors. PMID:28155913

Plasmonic Properties of Vertically Aligned Nanowire Arrays

DTIC Science & Technology

2012-01-01

scattering (SERS) applications. In this investigation, two types of vertical NW arrays were studied; those of ZnO NWs grown on nanosphere lithography...plasmonic nanowires to investigate this SERS effect. Here we used two types of vertical NWs, ZnO NWs, and Si NWs, respectively, to investigate SERS...successfully grow vertically aligned ZnO nanowires by the well-known VLS process. In this way, the ZnO NWs can be arranged in a repeatable hexagonal pattern

Vertical Si nanowire arrays fabricated by magnetically guided metal-assisted chemical etching

NASA Astrophysics Data System (ADS)

Chun, Dong Won; Kim, Tae Kyoung; Choi, Duyoung; Caldwell, Elizabeth; Kim, Young Jin; Paik, Jae Cheol; Jin, Sungho; Chen, Renkun

2016-11-01

In this work, vertically aligned Si nanowire arrays were fabricated by magnetically guided metal-assisted directional chemical etching. Using an anodized aluminum oxide template as a shadow mask, nanoscale Ni dot arrays were fabricated on an Si wafer to serve as a mask to protect the Si during the etching. For the magnetically guided chemical etching, we deposited a tri-layer metal catalyst (Au/Fe/Au) in a Swiss-cheese configuration and etched the sample under the magnetic field to improve the directionality of the Si nanowire etching and increase the etching rate along the vertical direction. After the etching, the nanowires were dried with minimal surface-tension-induced aggregation by utilizing a supercritical CO2 drying procedure. High-resolution transmission electron microscopy (HR-TEM) analysis confirmed the formation of single-crystal Si nanowires. The method developed here for producing vertically aligned Si nanowire arrays could find a wide range of applications in electrochemical and electronic devices.

Multiscale Study of Plasmonic Scattering and Light Trapping Effect in Silicon Nanowire Array Solar Cells.

PubMed

Meng, Lingyi; Zhang, Yu; Yam, ChiYung

2017-02-02

Nanometallic structures that support surface plasmons provide new ways to confine light at deep-subwavelength scales. The effect of light scattering in nanowire array solar cells is studied by a multiscale approach combining classical electromagnetic (EM) and quantum mechanical simulations. A photovoltaic device is constructed by integrating a silicon nanowire array with a plasmonic silver nanosphere. The light scatterings by plasmonic element and nanowire array are obtained via classical EM simulations, while current-voltage characteristics and optical properties of the nanowire cells are evaluated quantum mechanically. We found that the power conversion efficiency (PCE) of photovoltaic device is substantially improved due to the local field enhancement of the plasmonic effect and light trapping by the nanowire array. In addition, we showed that there exists an optimal nanowire number density in terms of optical confinement and solar cell PCE.

Large-scale fabrication of single crystalline tin nanowire arrays

NASA Astrophysics Data System (ADS)

Luo, Bin; Yang, Dachi; Liang, Minghui; Zhi, Linjie

2010-09-01

Large-scale single crystalline tin nanowire arrays with preferred lattice orientation along the [100] direction were fabricated in porous anodic aluminium oxide (AAO) membranes by the electrodeposition method using copper nanorod as a second electrode.Large-scale single crystalline tin nanowire arrays with preferred lattice orientation along the [100] direction were fabricated in porous anodic aluminium oxide (AAO) membranes by the electrodeposition method using copper nanorod as a second electrode. Electronic supplementary information (ESI) available: Experimental details and the information for single crystalline copper nanorods. See DOI: 10.1039/c0nr00206b

Synthesis and high catalytic properties of mesoporous Pt nanowire array by novel conjunct template method

NASA Astrophysics Data System (ADS)

Zhong, Yi; Xu, Cai-Ling; Kong, Ling-Bin; Li, Hu-Lin

2008-12-01

A novel conjunct template method for fabricating mesoporous Pt nanowire array through direct current (DC) electrodeposition of Pt into the pores of anodic aluminum oxide (AAO) template on Ti/Si substrate from hexagonal structured lyotropic liquid crystalline phase is demonstrated in this paper. The morphology and structure of as-prepared Pt nanowire array are characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrocatalytic properties of Pt nanowire array for methanol are also investigated in detail. The results indicate that Pt nanowire array has the unique mesoporous structure of approximate 40-50 nm in diameter, which resulted in the high surface area and greatly improved electrocatalytic activity for methanol. The mesoporous Pt nanowire array synthesized by the new conjunct template method has a very promising application in portable fuel cell power sources.

Plasmon resonant cavities in vertical nanowire arrays

DOEpatents

Bora, Mihail; Bond, Tiziana C.; Fasenfest, Benjamin J.; Behymer, Elaine M.

2014-07-15

Tunable plasmon resonant cavity arrays in paired parallel nanowire waveguides are presented. Resonances can be observed when the waveguide length is an odd multiple of quarter plasmon wavelengths, consistent with boundary conditions of node and antinode at the ends. Two nanowire waveguides can satisfy the dispersion relation of a planar metal-dielectric-metal waveguide of equivalent width equal to the square field average weighted gap. Confinement factors of over 10.sup.3 are possible due to plasmon focusing in the inter-wire space.

Directed growth of horizontally aligned gallium nitride nanowires for nanoelectromechanical resonator arrays.

PubMed

Henry, Tania; Kim, Kyungkon; Ren, Zaiyuan; Yerino, Christopher; Han, Jung; Tang, Hong X

2007-11-01

We report the growth of horizontally aligned arrays and networks of GaN nanowires (NWs) as resonant components in nanoelectromechanical systems (NEMS). A combination of top-down selective area growth (SAG) and bottom-up vapor-liquid-solid (VLS) synthesis enables flexible fabrication of highly ordered nanowire arrays in situ with no postgrowth dispersion. Mechanical resonance of free-standing nanowires are measured, with quality factors (Q) ranging from 400 to 1000. We obtained a Young's modulus (E) of approximately 338 GPa from an array of NWs with varying diameters and lengths. The measurement allows detection of nanowire motion with a rotating frame and reveals dual fundamental resonant modes in two orthogonal planes. A universal ratio between the resonant frequencies of these two fundamental modes, irrespective of their dimensions, is observed and attributed to an isosceles cross section of GaN NWs.

Simple Analytic Model for Nanowire Array Polarizers

NASA Astrophysics Data System (ADS)

Pelletier, Vincent; Asakawa, Koji; Wu, Mingshaw; Register, Richard; Chaikin, Paul

2006-03-01

Cylinder-forming diblock copolymers can be used to pattern nanowire arrays on a transparent substrate to be used as a polarizer, as described by Koji Asakawa in a complementary talk at this meeting. With a 33nm period, these wire arrays can polarize UV radiation, which is of great interest in lithography, astronomy and other areas. One can gain an analytical understanding of such an array made of non-perfectly conducting material of finite thickness using a model with an appropriately averaged complex dielectric function in an infinite wavelength approximation. This analysis predicts that the grid can go from an E-polarizer to an H-polarizer as the wavelength decreases below a cross-over wavelength, and experimental data confirm this cross-over. The overall response of the polarizing grid depends primarily on the plasma frequency of the metal used and the volume fraction of the nanowires, as well as the grid thickness. A numerical approach is also used to confirm the analytical model and assess departure from infinite wavelength effects. For our array dimensions, the polarization is only slightly different from this approximation for wavelengths down to 150nm.

High density group IV semiconductor nanowire arrays fabricated in nanoporous alumina templates

NASA Astrophysics Data System (ADS)

Redwing, Joan M.; Dilts, Sarah M.; Lew, Kok-Keong; Cranmer, Alexana E.; Mohney, Suzanne E.

2005-11-01

The fabrication of high density arrays of semiconductor nanowires is of interest for nanoscale electronics, chemical and biological sensing and energy conversion applications. We have investigated the synthesis, intentional doping and electrical characterization of Si and Ge nanowires grown by the vapor-liquid-solid (VLS) method in nanoporous alumina membranes. Nanoporous membranes provide a convenient platform for nanowire growth and processing, enabling control of wire diameter via pore size and the integration of contact metals for electrical testing. For VLS growth in nanoporous materials, reduced pressures and temperatures are required in order to promote the diffusion of reactants into the pore without premature decomposition on the membrane surface or pore walls. The effect of growth conditions on the growth rate of Si and Ge nanowires from SiH 4 and GeH 4 sources, respectively, was investigated and compared. In both cases, the measured activation energies for nanowire growth were substantially lower than activation energies typically reported for Si and Ge thin film deposition under similar growth conditions, suggesting that gold plays a catalytic role in the VLS growth process. Intentionally doped SiNW arrays were also prepared using trimethylboron (TMB) and phosphine (PH 3) as p-type and n-type dopant sources, respectively. Nanowire resistivities were calculated from plots of the array resistance as a function of nanowire length. A decrease in resistivity was observed for both n-type and p-type doped SiNW arrays compared to those grown without the addition of a dopant source.

Superconductivity of a Sn film controlled by an array of Co nanowires

NASA Astrophysics Data System (ADS)

Wei, Zhiyuan; Ye, Zuxin; Rathnayaka, Daya; Lyuksyutov, Igor; Wu, Wenhao; Naugle, Donald

2012-02-01

Superconducting properties of a hybrid structure composed of ferromagnetic Co nanowire arrays and a superconducting Sn film have been investigated. Ordered Co nanowires arrays with 60 nm, 150 nm and 200 nm diameter were electroplated into the pores of self organized anodic aluminum oxide (AAO) membranes. Hysteretic dependence of the Sn film superconducting properties on applied magnetic field and critical current enhancement at moderate fields has been observed. This behavior strongly depends on the ratio of the Sn film thickness to the Co nanowire diameter.

Superconductivity of a Sn film controlled by an array of Co nanowires

NASA Astrophysics Data System (ADS)

Wei, Z.; Ye, Z.; Rathnayaka, K. D. D.; Lyuksyutov, I. F.; Wu, W.; Naugle, D. G.

2012-09-01

Superconducting properties of a hybrid structure composed of ferromagnetic Co nanowire arrays and a superconducting Sn film have been investigated. Ordered Co nanowires arrays with 60 nm, 150 nm and 200 nm diameter were electroplated into the pores of self organized Anodic Aluminum Oxide (AAO) membranes. Hysteretic dependence of the Sn film superconducting properties on applied magnetic field and critical current enhancement at moderate fields has been observed. This behavior strongly depends on the ratio of the Sn film thickness to the Co nanowire diameter.

Development of nanowire arrays for neural probe

NASA Astrophysics Data System (ADS)

Abraham, Jose K.; Xie, Jining; Varadan, Vijay K.

2005-05-01

It is already established that functional electrical stimulation is an effective way to restore many functions of the brain in disabled individuals. The electrical stimulation can be done by using an array of electrodes. Neural probes stimulate or sense the biopotentials mainly through the exposed metal sites. These sites should be smaller relative to the spatial potential distribution so that any potential averaging in the sensing area can be avoided. At the same time, the decrease in size of these sensing sites is limited due to the increase in impedance levels and the thermal noise while decreasing its size. It is known that current density in a planar electrode is not uniform and a higher current density can be observer around the perimeter of the electrodes. Electrical measurements conducted on many nanotubes and nanowires have already proved that it could be possible to use for current density applications and the drawbacks of the present design in neural probes can be overcome by incorporating many nanotechnology solutions. In this paper we present the design and development of nanowire arrays for the neural probe for the multisite contact which has the ability to collect and analyze isolated single unit activity. An array of vertically grown nanowires is used as contact site and many of such arrays can be used for stimulating as well as recording sites. The nanolevel interaction and wireless communication solution can extend to applications involving the treatment of many neurological disorders including Parkinson"s disease, Alzheimer"s disease, spinal injuries and the treatment of blindness and paralyzed patients with minimal or no invasive surgical procedures.

Ultrahigh-density sub-10 nm nanowire array formation via surface-controlled phase separation.

PubMed

Tian, Yuan; Mukherjee, Pinaki; Jayaraman, Tanjore V; Xu, Zhanping; Yu, Yongsheng; Tan, Li; Sellmyer, David J; Shield, Jeffrey E

2014-08-13

We present simple, self-assembled, and robust fabrication of ultrahigh density cobalt nanowire arrays. The binary Co-Al and Co-Si systems phase-separate during physical vapor deposition, resulting in Co nanowire arrays with average diameter as small as 4.9 nm and nanowire density on the order of 10(16)/m(2). The nanowire diameters were controlled by moderating the surface diffusivity, which affected the lateral diffusion lengths. High resolution transmission electron microscopy reveals that the Co nanowires formed in the face-centered cubic structure. Elemental mapping showed that in both systems the nanowires consisted of Co with undetectable Al or Si and that the matrix consisted of Al with no distinguishable Co in the Co-Al system and a mixture of Si and Co in the Co-Si system. Magnetic measurements clearly indicate anisotropic behavior consistent with shape anisotropy. The dynamics of nanowire growth, simulated using an Ising model, is consistent with the experimental phase and geometry of the nanowires.

Welded-Ag-nanowires/FTO conducting film with high transmittance and its application in transparent supercapacitors

NASA Astrophysics Data System (ADS)

Qiao, Zhensong; Yang, Xiaopeng; Liu, Feng; Duan, Guangbin; Cao, Bingqiang

2017-03-01

Silver nanowires (AgNW) with a small diameter were synthesized by a facile and novel polyol reduction method. Ag nanowires ink was then spun on the surface of F-doped SnO2 (FTO) to form the AgNW/FTO conducting film. Welding treatment of the AgNW/FTO conducting film not only increased the optical transmittance from 71.9 % to 79.3 % at 550 nm and decreased the sheet resistance from 11.4 ohm sq-1 to 9.8 ohm sq-1, but also improved the adhesivity of AgNW network on FTO substrate. Furthermore, MnO2 nanosheets were directly deposited on welded-AgNW/FTO (wAF) substrate to prepare a transparent MnO2/weled-AgNW/FTO (MwAF) composite electrode. The MwAF electrode displayed excellent electrochemical performance, including high specific capacitance (375 F g-1 at 5 mV s-1) and superior cycle stability (173.3 % of the initial capacitance after 20000 GCD cycles).

Misfit-guided self-organization of anticorrelated Ge quantum dot arrays on Si nanowires.

PubMed

Kwon, Soonshin; Chen, Zack C Y; Kim, Ji-Hun; Xiang, Jie

2012-09-12

Misfit-strain guided growth of periodic quantum dot (QD) arrays in planar thin film epitaxy has been a popular nanostructure fabrication method. Engineering misfit-guided QD growth on a nanoscale substrate such as the small curvature surface of a nanowire represents a new approach to self-organized nanostructure preparation. Perhaps more profoundly, the periodic stress underlying each QD and the resulting modulation of electro-optical properties inside the nanowire backbone promise to provide a new platform for novel mechano-electronic, thermoelectronic, and optoelectronic devices. Herein, we report a first experimental demonstration of self-organized and self-limited growth of coherent, periodic Ge QDs on a one-dimensional Si nanowire substrate. Systematic characterizations reveal several distinctively different modes of Ge QD ordering on the Si nanowire substrate depending on the core diameter. In particular, Ge QD arrays on Si nanowires of around 20 nm diameter predominantly exhibit an anticorrelated pattern whose wavelength agrees with theoretical predictions. The correlated pattern can be attributed to propagation and correlation of misfit strain across the diameter of the thin nanowire substrate. The QD array growth is self-limited as the wavelength of the QDs remains unchanged even after prolonged Ge deposition. Furthermore, we demonstrate a direct kinetic transformation from a uniform Ge shell layer to discrete QD arrays by a postgrowth annealing process.

A simple and transparent well-aligned ZnO nanowire array ultraviolet photodetector with high responsivity

NASA Astrophysics Data System (ADS)

Yin, Lei; Ding, Hesheng; Yuan, Zhaolin; Huang, Wendeng; Shuai, Chunjiang; Xiong, Zhaoxin; Deng, Jianping; Lv, Tengbo

2018-06-01

Well-aligned zinc oxide (ZnO) nanowire arrays were grown on an interdigital patterned fluorine tin oxide (FTO)-coated glass substrate by a facile chemical bath deposition at low temperature. Morphology, crystalline structure, and optical properties of the ZnO nanowire arrays were analyzed in detail. The results revealed that the ZnO nanowires had wurtzite structure, typically ∼40-60 nm in diameter, and ∼700-800 nm in length, a great number of highly uniform and dense nanowires grew vertically on the substrate to form the well-aligned ZnO nanowire arrays, which had very high optical transmission (>86%) in the visible light region. In addition, the performance of ZnO nanowire arrays ultraviolet (UV) photodetector was systematically examined. The photosensitivity (S), responsivity (R), response and decay time of the photodetector were 703 at +0.2 V, 113 A/W at +5 V, 23 s and 73 s respectively. Also, the photoresponse mechanism of the UV photodetector was illuminated in terms of the oxygen adsorption-photodesorption process.

Vertical group III-V nanowires on si, heterostructures, flexible arrays and fabrication

DOEpatents

Wang, Deli; Soci, Cesare; Bao, Xinyu; Wei, Wei; Jing, Yi; Sun, Ke

2015-01-13

Embodiments of the invention provide a method for direct heteroepitaxial growth of vertical III-V semiconductor nanowires on a silicon substrate. The silicon substrate is etched to substantially completely remove native oxide. It is promptly placed in a reaction chamber. The substrate is heated and maintained at a growth temperature. Group III-V precursors are flowed for a growth time. Preferred embodiment vertical Group III-V nanowires on silicon have a core-shell structure, which provides a radial homojunction or heterojunction. A doped nanowire core is surrounded by a shell with complementary doping. Such can provide high optical absorption due to the long optical path in the axial direction of the vertical nanowires, while reducing considerably the distance over which carriers must diffuse before being collected in the radial direction. Alloy composition can also be varied. Radial and axial homojunctions and heterojunctions can be realized. Embodiments provide for flexible Group III-V nanowire structures. An array of Group III-V nanowire structures is embedded in polymer. A fabrication method forms the vertical nanowires on a substrate, e.g., a silicon substrate. Preferably, the nanowires are formed by the preferred methods for fabrication of Group III-V nanowires on silicon. Devices can be formed with core/shell and core/multi-shell nanowires and the devices are released from the substrate upon which the nanowires were formed to create a flexible structure that includes an array of vertical nanowires embedded in polymer.

Nanowire arrays restore vision in blind mice.

PubMed

Tang, Jing; Qin, Nan; Chong, Yan; Diao, Yupu; Yiliguma; Wang, Zhexuan; Xue, Tian; Jiang, Min; Zhang, Jiayi; Zheng, Gengfeng

2018-03-06

The restoration of light response with complex spatiotemporal features in retinal degenerative diseases towards retinal prosthesis has proven to be a considerable challenge over the past decades. Herein, inspired by the structure and function of photoreceptors in retinas, we develop artificial photoreceptors based on gold nanoparticle-decorated titania nanowire arrays, for restoration of visual responses in the blind mice with degenerated photoreceptors. Green, blue and near UV light responses in the retinal ganglion cells (RGCs) are restored with a spatial resolution better than 100 µm. ON responses in RGCs are blocked by glutamatergic antagonists, suggesting functional preservation of the remaining retinal circuits. Moreover, neurons in the primary visual cortex respond to light after subretinal implant of nanowire arrays. Improvement in pupillary light reflex suggests the behavioral recovery of light sensitivity. Our study will shed light on the development of a new generation of optoelectronic toolkits for subretinal prosthetic devices.

Study of Ag induced bimetallic (Au-Ag) nanowires on silicon (5 5 12) surfaces: Experiment and theoretical aspects

NASA Astrophysics Data System (ADS)

Bhukta, Anjan; Bagarti, Trilochan; Guha, Puspendu; Ravulapalli, Sathyavathi; Satpati, Biswarup; Rakshit, Bipul; Maiti, Paramita; Parlapalli, Venkata Satyam

2017-10-01

The reconstructed vicinal (high index) silicon surfaces, such as, Si (5 5 12) composes row-like structures that can be used as templates for growing aligned nanowires. By using a sub-monolayers of Ag, prior to Au deposition on reconstructed Si (5 512) surface, intermixing of Au and Ag, enhancement of aspect ratio of bimetallic Au-Ag nanowires with tunable morphology is reported. This is attributed to a combined effect of pre-grown Ag strips as nucleation centers for incoming Au ad-atoms and anisotropic Au-Ag intermixing. To achieve optimum conditions for the growth of larger aspect ratio Au-Ag nanostructures, the growth kinetics have been studied by varying growth and annealing temperatures. At ≈400 °C, the Ag diffused into silicon substrate and the inter-diffusion found to inhibit the formation of Au-Ag bimetallic nanostructures. Controlled experiments under ultra-high vacuum condition in a molecular beam epitaxy system and in-situ scanning tunneling microscopy measurements along with ex-situ scanning transmission and secondary electron microscopy measurements have been carried out to understand the bimetallic nanostructure growth. Kinetic Monte Carlo (KMC) simulations based on kinematics of ad-atoms on an anisotropic template with a solid on solid model in which the relative ratios of binding energies (that are obtained from the Density Functional Theory) have been used and the KMC simulations results agree with the experimental observations. Advantage of having bimetallic structures as effective substrates for Surface enhanced Raman spectroscopy application is demonstrated by detecting Rhodamine 6 G (R6G) molecule at the concentration of 10-7M.

Fabrication of Ni-silicide/Si heterostructured nanowire arrays by glancing angle deposition and solid state reaction.

PubMed

Hsu, Hsun-Feng; Huang, Wan-Ru; Chen, Ting-Hsuan; Wu, Hwang-Yuan; Chen, Chun-An

2013-05-10

This work develops a method for growing Ni-silicide/Si heterostructured nanowire arrays by glancing angle Ni deposition and solid state reaction on ordered Si nanowire arrays. Samples of ordered Si nanowire arrays were fabricated by nanosphere lithography and metal-induced catalytic etching. Glancing angle Ni deposition deposited Ni only on the top of Si nanowires. When the annealing temperature was 500°C, a Ni3Si2 phase was formed at the apex of the nanowires. The phase of silicide at the Ni-silicide/Si interface depended on the diameter of the Si nanowires, such that epitaxial NiSi2 with a {111} facet was formed at the Ni-silicide/Si interface in Si nanowires with large diameter, and NiSi was formed in Si nanowires with small diameter. A mechanism that is based on flux divergence and a nucleation-limited reaction is proposed to explain this phenomenon of size-dependent phase formation.

Fabrication of Ni-silicide/Si heterostructured nanowire arrays by glancing angle deposition and solid state reaction

PubMed Central

2013-01-01

This work develops a method for growing Ni-silicide/Si heterostructured nanowire arrays by glancing angle Ni deposition and solid state reaction on ordered Si nanowire arrays. Samples of ordered Si nanowire arrays were fabricated by nanosphere lithography and metal-induced catalytic etching. Glancing angle Ni deposition deposited Ni only on the top of Si nanowires. When the annealing temperature was 500°C, a Ni3Si2 phase was formed at the apex of the nanowires. The phase of silicide at the Ni-silicide/Si interface depended on the diameter of the Si nanowires, such that epitaxial NiSi2 with a {111} facet was formed at the Ni-silicide/Si interface in Si nanowires with large diameter, and NiSi was formed in Si nanowires with small diameter. A mechanism that is based on flux divergence and a nucleation-limited reaction is proposed to explain this phenomenon of size-dependent phase formation. PMID:23663726

Effects of Nanowire Length and Surface Roughness on the Electrochemical Sensor Properties of Nafion-Free, Vertically Aligned Pt Nanowire Array Electrodes

PubMed Central

Li, Zhiyang; Leung, Calvin; Gao, Fan; Gu, Zhiyong

2015-01-01

In this paper, vertically aligned Pt nanowire arrays (PtNWA) with different lengths and surface roughnesses were fabricated and their electrochemical performance toward hydrogen peroxide (H2O2) detection was studied. The nanowire arrays were synthesized by electroplating Pt in nanopores of anodic aluminum oxide (AAO) template. Different parameters, such as current density and deposition time, were precisely controlled to synthesize nanowires with different surface roughnesses and various lengths from 3 μm to 12 μm. The PtNWA electrodes showed better performance than the conventional electrodes modified by Pt nanowires randomly dispersed on the electrode surface. The results indicate that both the length and surface roughness can affect the sensing performance of vertically aligned Pt nanowire array electrodes. Generally, longer nanowires with rougher surfaces showed better electrochemical sensing performance. The 12 μm rough surface PtNWA presented the largest sensitivity (654 μA·mM−1·cm−2) among all the nanowires studied, and showed a limit of detection of 2.4 μM. The 12 μm rough surface PtNWA electrode also showed good anti-interference property from chemicals that are typically present in the biological samples such as ascorbic, uric acid, citric acid, and glucose. The sensing performance in real samples (river water) was tested and good recovery was observed. These Nafion-free, vertically aligned Pt nanowires with surface roughness control show great promise as versatile electrochemical sensors and biosensors. PMID:26404303

Hierarchically structured Co₃O₄@Pt@MnO₂ nanowire arrays for high-performance supercapacitors.

PubMed

Xia, Hui; Zhu, Dongdong; Luo, Zhentao; Yu, Yue; Shi, Xiaoqin; Yuan, Guoliang; Xie, Jianping

2013-10-17

Here we proposed a novel architectural design of a ternary MnO2-based electrode - a hierarchical Co3O4@Pt@MnO2 core-shell-shell structure, where the complemental features of the three key components (a well-defined Co3O4 nanowire array on the conductive Ti substrate, an ultrathin layer of small Pt nanoparticles, and a thin layer of MnO2 nanoflakes) are strategically combined into a single entity to synergize and construct a high-performance electrode for supercapacitors. Owing to the high conductivity of the well-defined Co3O4 nanowire arrays, in which the conductivity was further enhanced by a thin metal (Pt) coating layer, in combination with the large surface area provided by the small MnO2 nanoflakes, the as-fabricated Co3O4@Pt@MnO2 nanowire arrays have exhibited high specific capacitances, good rate capability, and excellent cycling stability. The architectural design demonstrated in this study provides a new approach to fabricate high-performance MnO2-based nanowire arrays for constructing next-generation supercapacitors.

3D hierarchical MnO2 nanorod/welded Ag-nanowire-network composites for high-performance supercapacitor electrodes.

PubMed

Qiao, Zhensong; Yang, Xiaopeng; Yang, Shuhua; Zhang, Liqiang; Cao, Bingqiang

2016-06-28

3D MnO2 nanorod/welded Ag-nanowire-network supercapacitor electrodes were prepared. Welding treatment of the Ag nanowire-network leads to low resistance and long lifetime. Galvanostatic charge/discharge (GCD) induces an ever-lasting morphology changing from flower-like to honeycomb-like for MnO2, which manifests as increasing specific capacitance to 663.4 F g(-1) after 7000 GCD cycles.

Field emission from in situ-grown vertically aligned SnO2 nanowire arrays

PubMed Central

2012-01-01

Vertically aligned SnO2 nanowire arrays have been in situ fabricated on a silicon substrate via thermal evaporation method in the presence of a Pt catalyst. The field emission properties of the SnO2 nanowire arrays have been investigated. Low turn-on fields of 1.6 to 2.8 V/μm were obtained at anode-cathode separations of 100 to 200 μm. The current density fluctuation was lower than 5% during a 120-min stability test measured at a fixed applied electric field of 5 V/μm. The favorable field-emission performance indicates that the fabricated SnO2 nanowire arrays are promising candidates as field emitters. PMID:22330800

Ultrahigh-Density Nanowire Arrays Grown in Self-Assembled Diblock Copolymer Templates

NASA Astrophysics Data System (ADS)

Thurn-Albrecht, T.; Schotter, J.; Kästle, G. A.; Emley, N.; Shibauchi, T.; Krusin-Elbaum, L.; Guarini, K.; Black, C. T.; Tuominen, M. T.; Russell, T. P.

2000-12-01

We show a simple, robust, chemical route to the fabrication of ultrahigh-density arrays of nanopores with high aspect ratios using the equilibrium self-assembled morphology of asymmetric diblock copolymers. The dimensions and lateral density of the array are determined by segmental interactions and the copolymer molecular weight. Through direct current electrodeposition, we fabricated vertical arrays of nanowires with densities in excess of 1.9 × 1011 wires per square centimeter. We found markedly enhanced coercivities with ferromagnetic cobalt nanowires that point toward a route to ultrahigh-density storage media. The copolymer approach described is practical, parallel, compatible with current lithographic processes, and amenable to multilayered device fabrication.

Ultrahigh-density nanowire arrays grown in self-assembled diblock copolymer templates.

PubMed

Thurn-Albrecht, T; Schotter, J; Kästle, G A; Emley, N; Shibauchi, T; Krusin-Elbaum, L; Guarini, K; Black, C T; Tuominen, M T; Russell, T P

2000-12-15

We show a simple, robust, chemical route to the fabrication of ultrahigh-density arrays of nanopores with high aspect ratios using the equilibrium self-assembled morphology of asymmetric diblock copolymers. The dimensions and lateral density of the array are determined by segmental interactions and the copolymer molecular weight. Through direct current electrodeposition, we fabricated vertical arrays of nanowires with densities in excess of 1.9 x 10(11) wires per square centimeter. We found markedly enhanced coercivities with ferromagnetic cobalt nanowires that point toward a route to ultrahigh-density storage media. The copolymer approach described is practical, parallel, compatible with current lithographic processes, and amenable to multilayered device fabrication.

Magnetic hysteresis in small-grained CoxPd1-x nanowire arrays

NASA Astrophysics Data System (ADS)

Viqueira, M. S.; Pozo-López, G.; Urreta, S. E.; Condó, A. M.; Cornejo, D. R.; Fabietti, L. M.

2015-11-01

Co-Pd nanowires with small grain size are fabricated by AC electrodeposition into hexagonally ordered alumina pores, 20-35 nm in diameter and about 1 μm long. The effects of the alloy composition, the nanowire diameter and the grain size on the hysteresis properties are considered. X-ray diffraction indicates that the nanowires are single phase, a fcc Co-Pd solid solution; electron microscopy results show that they are polycrystalline, with randomly oriented grains (7-12 nm), smaller than the wire diameter. Nanowire arrays are ferromagnetic, with an easy magnetization axis parallel to the nanowire long axis. Both, the coercive field and the loop squareness monotonously increase with the Co content and with the grain size, but no clear correlation with the wire diameter is found. The Co and Co-rich nanowire arrays exhibit coercive fields and reduced remanence values quite insensitive to temperature in the range 4 K-300 K; on the contrary, in Pd-rich nanowires both magnitudes are smaller and they largely increase during cooling below 100 K. These behaviors are systematized by considering the strong dependences displayed by the magneto-crystalline anisotropy and the saturation magnetostriction on composition and temperature. At low temperatures the effective anisotropy value and the domain-wall width to grain size ratio drastically change, promoting less cooperative and harder nucleation modes.

High Efficiency, Transparent, Reusable, and Active PM2.5 Filters by Hierarchical Ag Nanowire Percolation Network.

PubMed

Jeong, Seongmin; Cho, Hyunmin; Han, Seonggeun; Won, Phillip; Lee, Habeom; Hong, Sukjoon; Yeo, Junyeob; Kwon, Jinhyeong; Ko, Seung Hwan

2017-07-12

Air quality has become a major public health issue in Asia including China, Korea, and India. Particulate matters are the major concern in air quality. We present the first environmental application demonstration of Ag nanowire percolation network for a novel, electrical type transparent, reusable, and active PM2.5 air filter although the Ag nanowire percolation network has been studied as a very promising transparent conductor in optoelectronics. Compared with previous particulate matter air filter study using relatively weaker short-range intermolecular force in polar polymeric nanofiber, Ag nanowire percolation network filters use stronger long-range electrostatic force to capture PM2.5, and they are highly efficient (>99.99%), transparent, working on an active mode, low power consumption, antibacterial, and reusable after simple washing. The proposed new particulate matter filter can be applied for a highly efficient, reusable, active and energy efficient filter for wearable electronics application.

Superconducting Properties of Lead-Bismuth Films Controlled by Ferromagnetic Nanowire Arrays

NASA Astrophysics Data System (ADS)

Ye, Zuxin; Lyuksyutov, Igor F.; Wu, Wenhao; Naugle, Donald G.

2011-03-01

Superconducting properties of lead-bismuth (82% Pb and 18% Bi) alloy films deposited on ferromagnetic nanowire arrays have been investigated. Ferromagnetic Co or Ni nanowires are first electroplated into the columnar pores of anodic aluminum oxide (AAO) membranes. Superconducting Pb 82 Bi 18 films are then quench-condensed onto the polished surface of the AAO membranes filled with magnetic nanowires. A strong dependence of the Pb 82 Bi 18 superconducting properties on the ratio of the superconducting film thickness to the magnetic nanowire diameter and the material variety was observed.

Co/Au multisegmented nanowires: a 3D array of magnetostatically coupled nanopillars

NASA Astrophysics Data System (ADS)

Bran, C.; Ivanov, Yu P.; Kosel, J.; Chubykalo-Fesenko, O.; Vazquez, M.

2017-03-01

Arrays of multisegmented Co/Au nanowires with designed segment lengths and diameters have been prepared by electrodeposition into aluminum oxide templates. The high quality of the Co/Au interface and the crystallographic structure of Co segments have determined by high-resolution transmission electron microscopy. Magnetic hysteresis loop measurements show larger coercivity and squareness of multisegmented nanowires as compared to single segment Co nanowires. The complementary micromagnetic simulations are in good agreement with the experimental results, confirming that the magnetic behavior is defined mainly by magnetostatic coupling between different segments. The proposed structure constitutes an innovative route towards a 3D array of synchronized magnetic nano-oscillators with large potential in nanoelectronics.

Understanding InP Nanowire Array Solar Cell Performance by Nanoprobe-Enabled Single Nanowire Measurements.

PubMed

Otnes, Gaute; Barrigón, Enrique; Sundvall, Christian; Svensson, K Erik; Heurlin, Magnus; Siefer, Gerald; Samuelson, Lars; Åberg, Ingvar; Borgström, Magnus T

2018-05-09

III-V solar cells in the nanowire geometry might hold significant synthesis-cost and device-design advantages as compared to thin films and have shown impressive performance improvements in recent years. To continue this development there is a need for characterization techniques giving quick and reliable feedback for growth development. Further, characterization techniques which can improve understanding of the link between nanowire growth conditions, subsequent processing, and solar cell performance are desired. Here, we present the use of a nanoprobe system inside a scanning electron microscope to efficiently contact single nanowires and characterize them in terms of key parameters for solar cell performance. Specifically, we study single as-grown InP nanowires and use electron beam induced current characterization to understand the charge carrier collection properties, and dark current-voltage characteristics to understand the diode recombination characteristics. By correlating the single nanowire measurements to performance of fully processed nanowire array solar cells, we identify how the performance limiting parameters are related to growth and/or processing conditions. We use this understanding to achieve a more than 7-fold improvement in efficiency of our InP nanowire solar cells, grown from a different seed particle pattern than previously reported from our group. The best cell shows a certified efficiency of 15.0%; the highest reported value for a bottom-up synthesized InP nanowire solar cell. We believe the presented approach have significant potential to speed-up the development of nanowire solar cells, as well as other nanowire-based electronic/optoelectronic devices.

Platinum nanowire microelectrode arrays for neurostimulation applications: Fabrication, characterization, and in-vitro retinal cell stimulation

NASA Astrophysics Data System (ADS)

Whalen, John J., III

Implantable electrical neurostimulating devices are being developed for a number of applications, including artificial vision through retinal stimulation. The epiretinal prosthesis will use a two-dimensional array microelectrodes to address individual cells of the retina. MEMS fabrication processes can produce arrays of microelectrodes with these dimensions, but there are two critical issues that they cannot satisfy. One, the stimulating electrodes are the only part of the implanted electrical device that penetrate through the water impermeable package, and must do so without sacrificing hermeticity. Two, As electrode size decreases, the current density (A cm-2 ) increases, due to increased electrochemical impedance. This reduces the amount of charge that can be safely injected into the tissue. To date, MEMS processing method, cannot produce electrode arrays with good, prolonged hermetic properties. Similarly, MEMS approaches do not account for the increased impedance caused by decreased surface area. For these reasons there is a strong motivation for the development of a water-impermeable, substrate-penetrating electrode array with low electrochemical impedance. This thesis presents a stimulating electrode array fabricated from platinum nanowires using a modified electrochemical template synthesis approach. Nanowires are electrochemically deposited from ammonium hexachloroplatinate solution into lithographically patterned nanoporous anodic alumina templates to produce microarrays of platinum nanowires. The platinum nanowires penetrating through the ceramic aluminum oxide template serve as parallel electrical conduits through the water impermeable, electrically insulating substrate. Electrode impedance can be adjusted by either controlling the nanowire hydrous platinum oxide content or by partially etching the alumina template to expose additional surface area. A stepwise approach to this project was taken. First, the electrochemistry of ammonium

Misfit-guided self-organization of anti-correlated Ge quantum dot arrays on Si nanowires

PubMed Central

Kwon, Soonshin; Chen, Zack C.Y.; Kim, Ji-Hun; Xiang, Jie

2012-01-01

Misfit-strain guided growth of periodic quantum dot (QD) arrays in planar thin film epitaxy has been a popular nanostructure fabrication method. Engineering misfit-guided QD growth on a nanoscale substrate such as the small curvature surface of a nanowire represents a new approach to self-organized nanostructure preparation. Perhaps more profoundly, the periodic stress underlying each QD and the resulting modulation of electro-optical properties inside the nanowire backbone promise to provide a new platform for novel mechano-electronic, thermoelectronic, and optoelectronic devices. Herein, we report a first experimental demonstration of self-organized and self-limited growth of coherent, periodic Ge QDs on a one dimensional Si nanowire substrate. Systematic characterizations reveal several distinctively different modes of Ge QD ordering on the Si nanowire substrate depending on the core diameter. In particular, Ge QD arrays on Si nanowires of around 20 nm diameter predominantly exhibit an anti-correlated pattern whose wavelength agrees with theoretical predictions. The correlated pattern can be attributed to propagation and correlation of misfit strain across the diameter of the thin nanowire substrate. The QD array growth is self-limited as the wavelength of the QDs remains unchanged even after prolonged Ge deposition. Furthermore, we demonstrate a direct kinetic transformation from a uniform Ge shell layer to discrete QD arrays by a post-growth annealing process. PMID:22889063

In situ study on surface roughening in radiation-resistant Ag nanowires

NASA Astrophysics Data System (ADS)

Shang, Z.; Li, Jin; Fan, C.; Chen, Y.; Li, Q.; Wang, H.; Shen, T. D.; Zhang, X.

2018-05-01

Metallic materials subjected to heavy ion irradiation experience significant radiation damage. Free surface is a type of effective defect sinks to improve the radiation resistance in metallic materials. However, the radiation resistance of metallic nanowires (NWs) is largely unknown. Here we show, via in situ Kr ion irradiations in a transmission electron microscope, Ag NWs exhibited much better radiation resistance than coarse-grained Ag. Irradiation-induced prominent surface roughening in Ag NWs provides direct evidence for interaction between defect clusters and free surface. Diameter dependent variation of the surface roughness in irradiated Ag NWs has also been observed. This study provides insight on mechanisms of enhanced radiation resistance via free surfaces in metallic NWs.

In situ study on surface roughening in radiation-resistant Ag nanowires.

PubMed

Shang, Z; Li, Jin; Fan, C; Chen, Y; Li, Q; Wang, H; Shen, T D; Zhang, X

2018-05-25

Metallic materials subjected to heavy ion irradiation experience significant radiation damage. Free surface is a type of effective defect sinks to improve the radiation resistance in metallic materials. However, the radiation resistance of metallic nanowires (NWs) is largely unknown. Here we show, via in situ Kr ion irradiations in a transmission electron microscope, Ag NWs exhibited much better radiation resistance than coarse-grained Ag. Irradiation-induced prominent surface roughening in Ag NWs provides direct evidence for interaction between defect clusters and free surface. Diameter dependent variation of the surface roughness in irradiated Ag NWs has also been observed. This study provides insight on mechanisms of enhanced radiation resistance via free surfaces in metallic NWs.

Fabrication of free-standing copper foils covered with highly-ordered copper nanowire arrays

NASA Astrophysics Data System (ADS)

Zaraska, Leszek; Sulka, Grzegorz D.; Jaskuła, Marian

2012-07-01

The through-hole nanoporous anodic aluminum oxide (AAO) membranes with relatively large surface area (ca. 2 cm2) were employed for fabrication of free-standing and mechanically stable copper foils covered with close-packed and highly-ordered copper nanowire arrays. The home-made AAO membranes with different pore diameters and interpore distances were fabricated via a two-step self-organized anodization of aluminum performed in sulfuric acid, oxalic acid and phosphoric acid followed by the pore opening/widening procedure. The direct current (DC) electrodeposition of copper was performed efficiently on both sides of AAO templates. The bottom side of the AAO templates was not insulated and consequently Cu nanowire arrays on thick Cu layers were obtained. The proposed template-assisted fabrication of free-standing copper nanowire array electrodes is a promising method for synthesis of nanostructured current collectors. The composition of Cu nanowires was confirmed by energy dispersive X-Ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses. The structural features of nanowires were evaluated from field emission scanning electron microscopy (FE-SEM) images and compared with the characteristic parameters of anodic alumina membranes.

Epitaxial growth of InGaN nanowire arrays for light emitting diodes.

PubMed

Hahn, Christopher; Zhang, Zhaoyu; Fu, Anthony; Wu, Cheng Hao; Hwang, Yun Jeong; Gargas, Daniel J; Yang, Peidong

2011-05-24

Significant synthetic challenges remain for the epitaxial growth of high-quality InGaN across the entire compositional range. One strategy to address these challenges has been to use the nanowire geometry because of its strain relieving properties. Here, we demonstrate the heteroepitaxial growth of In(x)Ga(1-x)N nanowire arrays (0.06 ≤ x ≤ 0.43) on c-plane sapphire (Al(2)O(3)(001)) using a halide chemical vapor deposition (HCVD) technique. Scanning electron microscopy and X-ray diffraction characterization confirmed the long-range order and epitaxy of vertically oriented nanowires. Structural characterization by transmission electron microscopy showed that single crystalline nanowires were grown in the ⟨002⟩ direction. Optical properties of InGaN nanowire arrays were investigated by absorption and photoluminescence measurements. These measurements show the tunable direct band gap properties of InGaN nanowires into the yellow-orange region of the visible spectrum. To demonstrate the utility of our HCVD method for implementation into devices, LEDs were fabricated from In(x)Ga(1-x)N nanowires epitaxially grown on p-GaN(001). Devices showed blue (x = 0.06), green (x = 0.28), and orange (x = 0.43) electroluminescence, demonstrating electrically driven color tunable emission from this p-n junction.

Large-area fabrication of patterned ZnO-nanowire arrays using light stamping lithography.

PubMed

Hwang, Jae K; Cho, Sangho; Seo, Eun K; Myoung, Jae M; Sung, Myung M

2009-12-01

We demonstrate selective adsorption and alignment of ZnO nanowires on patterned poly(dimethylsiloxane) (PDMS) thin layers with (aminopropyl)siloxane self-assembled monolayers (SAMs). Light stamping lithography (LSL) was used to prepare patterned PDMS thin layers as neutral passivation regions on Si substrates. (3-Aminopropyl)triethoxysilane-based SAMs were selectively formed only on regions exposing the silanol groups of the Si substrates. The patterned positively charged amino groups define and direct the selective adsorption of ZnO nanowires with negative surface charges in the protic solvent. This procedure can be adopted in automated printing machines that generate patterned ZnO-nanowire arrays on large-area substrates. To demonstrate its usefulness, the LSL method was applied to prepare ZnO-nanowire transistor arrays on 4-in. Si wafers.

Color-Tunable ZnO/GaN Heterojunction LEDs Achieved by Coupling with Ag Nanowire Surface Plasmons.

PubMed

Yang, Liu; Wang, Yue; Xu, Haiyang; Liu, Weizhen; Zhang, Cen; Wang, Chunliang; Wang, Zhongqiang; Ma, Jiangang; Liu, Yichun

2018-05-09

Color-tunable light-emitting devices (LEDs) have a great impact on our daily life. Herein, LEDs with tunable electroluminescence (EL) color were achieved via introducing Ag nanowires surface plasmons into p-GaN/n-ZnO film heterostructures. By optimizing the surface coverage density of coated Ag nanowires, the EL color was changed continuously from yellow-green to blue-violet. Transient-state and temperature-variable fluorescence emission characterizations uncovered that the spontaneous emission rate and the internal quantum efficiency of the near-UV emission were increased as a consequence of the resonance coupling interaction between Ag nanowires surface plasmons and ZnO excitons. This effect induces the selective enhancement of the blue-violet EL component but suppresses the defect-related yellow-green emission, leading to the observed tunable EL color. The proposed strategy of introducing surface plasmons can be further applied to many other kinds of LEDs for their selective enhancement of EL intensity and effective adjustment of the emission color.

Effect of impurities on the mechanical and electronic properties of Au, Ag, and Cu monatomic chain nanowires

NASA Astrophysics Data System (ADS)

Çakır, D.; Gülseren, O.

2011-08-01

In this study, we have investigated the interaction of various different atomic and molecular species (H, C, O, H2, and O2) with the monatomic chains of Au, Ag, and Cu via total-energy calculations using the plane-wave pseudopotential method based on density functional theory. The stability, energetics, mechanical, and electronic properties of the clean and contaminated Au, Ag, and Cu nanowires have been presented. We have observed that the interaction of H, C, or O atoms with the monatomic chains are much stronger than the one of H2 or O2 molecules. The atomic impurities can easily be incorporated into these nanowires; they form stable and strong bonds with these one-dimensional structures when they are inserted in or placed close to the nanowires. Moreover, the metal-atomic impurity bond is much stronger than the metal-metal bond. Upon elongation, the nanowires contaminated with atomic impurities usually break from the remote metal-metal bond. We have observed both metallic and semiconducting contaminated nanowires depending on the type of impurity, whereas all clean monatomic chains of Au, Cu, and Ag exhibit metallic behavior. Our findings indicate that the stability and the electronic properties of these monatomic chains can be tuned by using appropriate molecular or atomic additives.

Disposable sensor based on enzyme-free Ni nanowire array electrode to detect glutamate.

PubMed

Jamal, Mamun; Hasan, Maksudul; Mathewson, Alan; Razeeb, Kafil M

2013-02-15

Enzyme free electrochemical sensor platform based on a vertically aligned nickel nanowire array (NiNAE) and Pt coated nickel nanowire array (Pt/NiNAE) have been developed to detect glutamate. Morphological characterisation of Ni electrodes was carried out using scanning and transmission electron microscopy combined with energy dispersive X-ray (SEM-EDX), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Cyclic voltammetry (CV) and amperometry were used to evaluate the catalytic activity of the NiNAE and the Pt/NiNAE for glutamate. It has been found that both NiNAE and Pt/NiNAE electrodes showed remarkably enhanced electrocatalytic activity towards glutamate compared to planar Ni electrodes, and showed higher catalytic activity when compared to other metallic nanostructure electrodes such as gold nanowire array electrodes (AuNAE) and Pt coated gold nanowire array electrode (Pt/AuNAE). The sensitivity of NiNAE and Pt/NiNAE has been found to be 65 and 96 μA mM(-1) cm(-2), respectively, which is approximately 6 to 9 times higher than the state of the art glutamate sensor. Under optimal detection conditions, the as prepared sensors exhibited linear behaviour for glutamate detection in the concentration up to 8mM for both NiNAE and Pt/NiNAE with a limit of detection of 68 and 83 μM, respectively. Experimental results show that the vertically aligned ordered nickel nanowire array electrode (NiNAE) has significant promise for fabricating cost effective, enzyme-less, sensitive, stable and selective sensor platform. Copyright © 2012 Elsevier B.V. All rights reserved.

Tunable absorption resonances in the ultraviolet for InP nanowire arrays.

PubMed

Aghaeipour, Mahtab; Anttu, Nicklas; Nylund, Gustav; Samuelson, Lars; Lehmann, Sebastian; Pistol, Mats-Erik

2014-11-17

The ability to tune the photon absorptance spectrum is an attracting way of tailoring the response of devices like photodetectors and solar cells. Here, we measure the reflectance spectra of InP substrates patterned with arrays of vertically standing InP nanowires. Using the reflectance spectra, we calculate and analyze the corresponding absorptance spectra of the nanowires. We show that we can tune absorption resonances for the nanowire arrays into the ultraviolet by decreasing the diameter of the nanowires. When we compare our measurements with electromagnetic modeling, we generally find good agreement. Interestingly, the remaining differences between modeled and measured spectra are attributed to a crystal-phase dependence in the refractive index of InP. Specifically, we find indication of significant differences in the refractive index between the modeled zinc-blende InP nanowires and the measured wurtzite InP nanowires in the ultraviolet. We believe that such crystal-phase dependent differences in the refractive index affect the possibility to excite optical resonances in the large wavelength range of 345 < λ < 390 nm. To support this claim, we investigated how resonances in nanostructures can be shifted in wavelength by geometrical tuning. We find that dispersion in the refractive index can dominate over geometrical tuning and stop the possibility for such shifting. Our results open the door for using crystal-phase engineering to optimize the absorption in InP nanowire-based solar cells and photodetectors.

Improving emission uniformity and linearizing band dispersion in nanowire arrays using quasi-aperiodicity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, P. Duke; Koleske, Daniel D.; Povinelli, Michelle L.

For this study, we experimentally investigate a new class of quasi-aperiodic structures for improving the emission pattern in nanowire arrays. Efficient normal emission, as well as lasing, can be obtained from III-nitride photonic crystal (PhC) nanowire arrays that utilize slow group velocity modes near the Γ-point in reciprocal space. However, due to symmetry considerations, the emitted far-field pattern of such modes are often ‘donut’-like. Many applications, including lighting for displays or lasers, require a more uniform beam profile in the far-field. Previous work has improved far-field beam uniformity of uncoupled modes by changing the shape of the emitting structure. However,more » in nanowire systems, the shape of nanowires cannot always be arbitrarily changed due to growth or etch considerations. Here, we investigate breaking symmetry by instead changing the position of emitters. Using a quasi-aperiodic geometry, which changes the emitter position within a photonic crystal supercell (2x2), we are able to linearize the photonic bandstructure near the Γ-point and greatly improve emitted far-field uniformity. We realize the III-nitride nanowires structures using a top-down fabrication procedure that produces nanowires with smooth, vertical sidewalls. Comparison of room-temperature micro-photoluminescence (µ-PL) measurements between periodic and quasi-aperiodic nanowire arrays reveal resonances in each structure, with the simple periodic structure producing a donut beam in the emitted far-field and the quasi-aperiodic structure producing a uniform Gaussian-like beam. We investigate the input pump power vs. output intensity in both systems and observe the simple periodic array exhibiting a non-linear relationship, indicative of lasing. We believe that the quasi-aperiodic approach studied here provides an alternate and promising strategy for shaping the emission pattern of nanoemitter systems.« less

Hydrothermal growth of ZnO nanowire arrays: fine tuning by precursor supersaturation

DOE PAGES

Yan, Danhua; Cen, Jiajie; Zhang, Wenrui; ...

2016-12-20

In this paper, we develop a technique that fine tunes the hydrothermal growth of ZnO nanowires to address the difficulties in controlling their growth in a conventional one-pot hydrothermal method. In our technique, precursors are separately and slowly supplied with the assistance of a syringe pump, through the entire course of the growth. Compared to the one-pot method, the significantly lowered supersaturation of precursors helps eliminating competitive homogeneous nucleation and improves the reproducibility. The supersaturation degree can be readily tuned by the precursor quantity and injection rate, thus forming ZnO nanowire arrays of various geometries and packing densities in amore » highly controllable fashion. The precise control of ZnO nanowire growth enables systematic studies on the correlation between the material's properties and its morphology. Finally, in this work, ZnO nanowire arrays of various morphologies are studied as photoelectrochemical (PEC) water splitting photoanodes, in which we establish clear correlations between the water splitting performance and the nanowires' size, shape, and packing density.« less

CONDUCTING-POLYMER NANOWIRE IMMUNOSENSOR ARRAYS FOR MICROBIAL PATHOGENS

EPA Science Inventory

The lack of methods for routine rapid and sensitive detection and quantification of specific pathogens has limited the amount of information available on their occurrence in drinking water and other environmental samples. The nanowire biosensor arrays developed in this study w...

Silver nanowire/polymer composite soft conductive film fabricated by large-area compatible coating for flexible pressure sensor array

NASA Astrophysics Data System (ADS)

Chen, Sujie; Li, Siying; Peng, Sai; Huang, Yukun; Zhao, Jiaqing; Tang, Wei; Guo, Xiaojun

2018-01-01

Soft conductive films composed of a silver nanowire (AgNW) network, a neutral-pH PEDOT:PSS over-coating layer and a polydimethylsiloxane (PDMS) elastomer substrate are fabricated by large area compatible coating processes. The neutral-pH PEDOT:PSS layer is shown to be able to significantly improve the conductivity, stretchability and air stability of the conductive films. The soft conductive films are patterned using a simple maskless patterning approach to fabricate an 8 × 8 flexible pressure sensor array. It is shown that such soft conductive films can help to improve the sensitivity and reduce the signal crosstalk over the pressure sensor array. Project supported by the Science and Technology Commission of Shanghai Municipality (No. 16JC1400603).

Synthesis and characterization of silicon nanowire arrays for photovoltaic applications

NASA Astrophysics Data System (ADS)

Eichfeld, Sarah M.

The overall objective of this thesis was the development of processes for the fabrication of radial p-n silicon nanowires (SiNWs) using bottom-up nanowire growth techniques on silicon and glass substrates. Vapor-liquid-solid (VLS) growth was carried out on Si(111) substrates using SiCl4 as the silicon precursor. Growth conditions including temperature, PSiCl4, PH2, and position were investigated to determine the optimum growth conditions for epitaxially oriented silicon nanowire arrays. The experiments revealed that the growth rate of the silicon nanowires exhibits a maximum as a function of PSiCl4 and P H2. Gas phase equilibrium calculations were used in conjunction with a mass transport model to explain the experimental data. The modeling results demonstrate a similar maximum in the mass of solid silicon predicted to form as a function of PSiCl4 and PH2, which results from a change in the gas phase concentration of SiHxCly and SiClx species. This results in a shift in the process from growth to etching with increasing PSiCl4. In general, for the atmospheric pressure conditions employed in this study, growth at higher temperatures >1000°C and higher SiCl4 concentrations gave the best results. The growth of silicon nanowire arrays on anodized alumina (AAO)-coated glass substrates was also investigated. Glass will not hold up to the high temperatures required for Si nanowire growth with SiCl4 so SiH 4 was used as the Si precursor instead. Initial studies were carried out to measure the resistivity of p-type and n-type silicon nanowires grown in freestanding AAO membranes. A series of nanowire samples were grown in which the doping and the nanowire length inside the membrane were varied. Circular metal contacts were deposited on the top surface of the membranes and the resistance of the nanowire arrays was measured. The measured resistance versus nanowire length was plotted and the nanowire resistivity was extracted from the slope. The resistivity of the silicon

Growth of Vertically Aligned ZnO Nanowire Arrays Using Bilayered Metal Catalysts

DTIC Science & Technology

2012-01-01

12] J. P. Liu, C. X. Guo, C. M. Li et al., “Carbon-decorated ZnO nanowire array: a novel platform for direct electrochemistry of enzymes and...cited. Vertically aligned, high-density ZnO nanowires (NWs) were grown for the first time on c-plane sapphire using binary alloys of Ni/Au or Cu/Au as...deleterious to the ZnO NW array growth. Significant improvement of the Au adhesion on the substrate was noted, opening the potential for direct

Aligning Ag Nanowires by a Facile Bioinspired Directional Liquid Transfer: Toward Anisotropic Flexible Conductive Electrodes.

PubMed

Meng, Lili; Bian, Ruixin; Guo, Cheng; Xu, Bojie; Liu, Huan; Jiang, Lei

2018-06-01

Recent years have witnessed the booming development of transparent flexible electrodes (TFEs) for their applications in electronics and optoelectronic devices. Various strategies have thus been developed for preparing TFEs with higher flexibility and conductivity. However, little work has focused on TFEs with anisotropic conductivity. Here, a facile strategy of directional liquid transfer is proposed, guided by a conical fibers array (CFA), based on which silver nanowires (AgNWs) are aligned on a soft poly(ethylene terephthalate) substrate in large scale. After further coating a second thin layer of the conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), a TFE with notable anisotropic conductivity and excellent optical transmittance of 95.2% is prepared. It is proposed that the CFA enables fine control over the receding of the three-phase contact line during the dewetting process, where AgNWs are guided and aligned by the as-generated directional stress. Moreover, anisotropic electrochemical deposition is enabled where the Cu nanoparticles deposit only on the oriented AgNWs, leading to a surface with anisotropic wetting behavior. Importantly, the approach enables alignment of AgNWs via multiple directions at one step. It is envisioned that the as-developed approach will provide an optional approach for simple and low-cost preparation of TFE with various functions. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Large-scale fabrication of single crystalline tin nanowire arrays.

PubMed

Luo, Bin; Yang, Dachi; Liang, Minghui; Zhi, Linjie

2010-09-01

Large-scale single crystalline tin nanowire arrays with preferred lattice orientation along the [100] direction were fabricated in porous anodic aluminium oxide (AAO) membranes by the electrodeposition method using copper nanorod as a second electrode.

Controlling the growth and field emission properties of silicide nanowire arrays by direct silicification of Ni foil.

PubMed

Liu, Zhihong; Zhang, Hui; Wang, Lei; Yang, Deren

2008-09-17

Nickel silicide nanowire arrays have been achieved by the decomposition of SiH(4) on Ni foil at 650 °C. It is indicated that the nickel silicide nanowires consist of roots with diameter of about 100-200 nm and tips with diameter of about 10-50 nm. A Ni diffusion controlled mechanism is proposed to explain the formation of the nickel silicide nanowires. Field emission measurement shows that the turn-on field of the nickel silicide nanowire arrays is low, at about 3.7 V µm(-1), and the field enhancement factor is as high as 4280, so the arrays have promising applications as emitters.

Amplified Thermionic Cooling Using Arrays of Nanowires

NASA Technical Reports Server (NTRS)

Yang, Eui-Hyeok; Choi, Daniel; Shcheglov, Kirill; Hishinuma, Yoshikazu

2007-01-01

A class of proposed thermionic cooling devices would incorporate precise arrays of metal nanowires as electron emitters. The proposed devices could be highly miniaturized, enabling removal of heat from locations, very close to electronic devices, that have previously been inaccessible for heat-removal purposes. The resulting enhancement of removal of heat would enable operation of the devices at higher power levels and higher clock speeds. Moreover, the mass, complexity, and bulk of electronic circuitry incorporating these highly miniaturized cooling devices could be considerably reduced, relative to otherwise equivalent circuitry cooled by conventional electromechanical, thermoelectric, and fluidic means. In thermionic cooling, one exploits the fact that because only the highest-energy electrons are thermionically emitted, collecting those electrons to prevent their return to the emitting electrode results in the net removal of heat from that electrode. Collection is effected by applying an appropriate positive bias potential to another electrode placed near the emitting electrode. The concept underlying the proposal is that the thermionic-emission current and, hence, the cooling effect attainable by use of an array of nanowires could be significantly greater than that attainable by use of a single emitting electrode or other electron- emitting surface. The wires in an array according to the proposal would protrude perpendicularly from a planar surface and their heights would be made uniform to within a sub-nanometer level of precision

Titanium dioxide nanowire sensor array integration on CMOS platform using deterministic assembly.

PubMed

Gall, Oren Z; Zhong, Xiahua; Schulman, Daniel S; Kang, Myungkoo; Razavieh, Ali; Mayer, Theresa S

2017-06-30

Nanosensor arrays have recently received significant attention due to their utility in a wide range of applications, including gas sensing, fuel cells, internet of things, and portable health monitoring systems. Less attention has been given to the production of sensor platforms in the μW range for ultra-low power applications. Here, we discuss how to scale the nanosensor energy demand by developing a process for integration of nanowire sensing arrays on a monolithic CMOS chip. This work demonstrates an off-chip nanowire fabrication method; subsequently nanowires link to a fused SiO 2 substrate using electric-field assisted directed assembly. The nanowire resistances shown in this work have the highest resistance uniformity reported to date of 18%, which enables a practical roadmap towards the coupling of nanosensors to CMOS circuits and signal processing systems. The article also presents the utility of optimizing annealing conditions of the off-chip metal-oxides prior to CMOS integration to avoid limitations of thermal budget and process incompatibility. In the context of the platform demonstrated here, directed assembly is a powerful tool that can realize highly uniform, cross-reactive arrays of different types of metal-oxide nanosensors suited for gas discrimination and signal processing systems.

Titanium dioxide nanowire sensor array integration on CMOS platform using deterministic assembly

NASA Astrophysics Data System (ADS)

Gall, Oren Z.; Zhong, Xiahua; Schulman, Daniel S.; Kang, Myungkoo; Razavieh, Ali; Mayer, Theresa S.

2017-06-01

Nanosensor arrays have recently received significant attention due to their utility in a wide range of applications, including gas sensing, fuel cells, internet of things, and portable health monitoring systems. Less attention has been given to the production of sensor platforms in the μW range for ultra-low power applications. Here, we discuss how to scale the nanosensor energy demand by developing a process for integration of nanowire sensing arrays on a monolithic CMOS chip. This work demonstrates an off-chip nanowire fabrication method; subsequently nanowires link to a fused SiO2 substrate using electric-field assisted directed assembly. The nanowire resistances shown in this work have the highest resistance uniformity reported to date of 18%, which enables a practical roadmap towards the coupling of nanosensors to CMOS circuits and signal processing systems. The article also presents the utility of optimizing annealing conditions of the off-chip metal-oxides prior to CMOS integration to avoid limitations of thermal budget and process incompatibility. In the context of the platform demonstrated here, directed assembly is a powerful tool that can realize highly uniform, cross-reactive arrays of different types of metal-oxide nanosensors suited for gas discrimination and signal processing systems.

Mechanical behavior enhancement of ZnO nanowire by embedding different nanowires

NASA Astrophysics Data System (ADS)

Vazinishayan, Ali; Yang, Shuming; Lambada, Dasaradha Rao; Wang, Yiming

2018-06-01

In this work, we employed commercial finite element modeling (FEM) software package ABAQUS to analyze mechanical properties of ZnO nanowire before and after embedding with different kinds of nanowires, having different materials and cross-section models such as Au (circular), Ag (pentagonal) and Si (rectangular) using three point bending technique. The length and diameter of the ZnO nanowire were measured to be 12,280 nm and 103.2 nm, respectively. In addition, Au, Ag and Si nanowires were considered to have the length of 12,280 nm and the diameter of 27 nm. It was found that after embedding Si nanowire with rectangular cross-section into the ZnO nanowire, the distribution of Von Misses stresses criterion, displacement and strain were decreased than the other nanowires embedded. The highest stiffness, the elastic deformation and the high strength against brittle failure have been made by Si nanowire comparison to the Au and Ag nanowires, respectively.

Electrolyte-gated transistors based on conducting polymer nanowire junction arrays.

PubMed

Alam, Maksudul M; Wang, Jun; Guo, Yaoyao; Lee, Stephanie P; Tseng, Hsian-Rong

2005-07-07

In this study, we describe the electrolyte gating and doping effects of transistors based on conducting polymer nanowire electrode junction arrays in buffered aqueous media. Conducting polymer nanowires including polyaniline, polypyrrole, and poly(ethylenedioxythiophene) were investigated. In the presence of a positive gate bias, the device exhibits a large on/off current ratio of 978 for polyaniline nanowire-based transistors; these values vary according to the acidity of the gate medium. We attribute these efficient electrolyte gating and doping effects to the electrochemically fabricated nanostructures of conducting polymer nanowires. This study demonstrates that two-terminal devices can be easily converted into three-terminal transistors by simply immersing the device into an electrolyte solution along with a gate electrode. Here, the field-induced modulation can be applied for signal amplification to enhance the device performance.

Synchrotron emission from nanowire array targets irradiated by ultraintense laser pulses

NASA Astrophysics Data System (ADS)

Martinez, B.; d’Humières, E.; Gremillet, L.

2018-07-01

We present a numerical study, based on two-dimensional particle-in-cell simulations, of the synchrotron emission induced during the interaction of femtosecond laser pulses of intensities I = 1021–1023 W cm‑2 with nanowire arrays. Through an extensive parametric scan on the target parameters, we identify and characterize several dominant radiation mechanisms, mainly depending on the transparency or opacity of the plasma produced by the wire expansion. At I = 1022 W m‑2, the emission of high-energy (>10 keV) photons attains a maximum conversion efficiency of ∼10% for 36–50 nm wire widths and 1 μm interspacing. This maximum radiation yield is found to be similar to that achieved in a uniform plasma of same average (sub-solid) density, but nanowire arrays provide efficient radiation sources over a broader parameter range. Moreover, we examine the variations of the photon spectra with the laser intensity and the wire material, and we demonstrate that the radiation efficiency can be further enhanced by adding a plasma mirror at the backside of the nanowire array. Finally, we briefly consider the influence of a finite laser focal spot and oblique incidence angle.

High thermoelectric properties of (Sb, Bi)2Te3 nanowire arrays by tilt-structure engineering

NASA Astrophysics Data System (ADS)

Tan, Ming; Hao, Yanming; Deng, Yuan; Chen, Jingyi

2018-06-01

In this paper, we present an innovative tilt-structure design concept for (Sb, Bi)2Te3 nanowire array assembled by high-quality nanowires with well oriented growth, utilizing a simple vacuum thermal evaporation technique. The unusual tilt-structure (Sb, Bi)2Te3 nanowire array with a tilted angle of 45° exhibits a high thermoelectric dimensionless figure-of-merit ZT = 1.72 at room temperature. The relatively high ZT value in contrast to that of previously reported (Sb, Bi)2Te3 materials and the vertical (Sb, Bi)2Te3 nanowire arrays evidently reveals the crucial role of the unique tilt-structure in favorably influencing carrier and phonon transport properties, resulting in a significantly improved ZT value. The transport mechanism of such tilt-structure is proposed and investigated. This method opens a new approach to optimize nano-structure in thin films for next-generation thermoelectric materials and devices.

Seedless Growth of Bismuth Nanowire Array via Vacuum Thermal Evaporation

PubMed Central

Liu, Mingzhao; Nam, Chang-Yong; Zhang, Lihua

2015-01-01

Here a seedless and template-free technique is demonstrated to scalably grow bismuth nanowires, through thermal evaporation in high vacuum at RT. Conventionally reserved for the fabrication of metal thin films, thermal evaporation deposits bismuth into an array of vertical single crystalline nanowires over a flat thin film of vanadium held at RT, which is freshly deposited by magnetron sputtering or thermal evaporation. By controlling the temperature of the growth substrate the length and width of the nanowires can be tuned over a wide range. Responsible for this novel technique is a previously unknown nanowire growth mechanism that roots in the mild porosity of the vanadium thin film. Infiltrated into the vanadium pores, the bismuth domains (~ 1 nm) carry excessive surface energy that suppresses their melting point and continuously expels them out of the vanadium matrix to form nanowires. This discovery demonstrates the feasibility of scalable vapor phase synthesis of high purity nanomaterials without using any catalysts. PMID:26709727

Localized temperature and chemical reaction control in nanoscale space by nanowire array.

PubMed

Jin, C Yan; Li, Zhiyong; Williams, R Stanley; Lee, K-Cheol; Park, Inkyu

2011-11-09

We introduce a novel method for chemical reaction control with nanoscale spatial resolution based on localized heating by using a well-aligned nanowire array. Numerical and experimental analysis shows that each individual nanowire could be selectively and rapidly Joule heated for local and ultrafast temperature modulation in nanoscale space (e.g., maximum temperature gradient 2.2 K/nm at the nanowire edge; heating/cooling time < 2 μs). By taking advantage of this capability, several nanoscale chemical reactions such as polymer decomposition/cross-linking and direct and localized hydrothermal synthesis of metal oxide nanowires were demonstrated.

Controllable Synthesis of Copper Oxide/Carbon Core/Shell Nanowire Arrays and Their Application for Electrochemical Energy Storage

PubMed Central

Zhan, Jiye; Chen, Minghua; Xia, Xinhui

2015-01-01

Rational design/fabrication of integrated porous metal oxide arrays is critical for the construction of advanced electrochemical devices. Herein, we report self-supported CuO/C core/shell nanowire arrays prepared by the combination of electro-deposition and chemical vapor deposition methods. CuO/C nanowires with diameters of ~400 nm grow quasi-vertically to the substrates forming three-dimensional arrays architecture. A thin carbon shell is uniformly coated on the CuO nanowire cores. As an anode of lithium ion batteries, the resultant CuO/C nanowire arrays are demonstrated to have high specific capacity (672 mAh·g−1 at 0.2 C) and good cycle stability (425 mAh·g−1 at 1 C up to 150 cycles). The core/shell arrays structure plays positive roles in the enhancement of Li ion storage due to fast ion/electron transfer path, good strain accommodation and sufficient contact between electrolyte and active materials. PMID:28347084

The structural conversion from α-AgVO3 to β-AgVO3: Ag nanoparticle decorated nanowires with application as cathode materials for Li-ion batteries.

PubMed

McNulty, David; Ramasse, Quentin; O'Dwyer, Colm

2016-09-15

The majority of electrode materials in batteries and related electrochemical energy storage devices are fashioned into slurries via the addition of a conductive additive and a binder. However, aggregation of smaller diameter nanoparticles in current generation electrode compositions can result in non-homogeneous active materials. Inconsistent slurry formulation may lead to inconsistent electrical conductivity throughout the material, local variations in electrochemical response, and the overall cell performance. Here we demonstrate the hydrothermal preparation of Ag nanoparticle (NP) decorated α-AgVO 3 nanowires (NWs) and their conversion to tunnel structured β-AgVO 3 NWs by annealing to form a uniform blend of intercalation materials that are well connected electrically. The synthesis of nanostructures with chemically bound conductive nanoparticles is an elegant means to overcome the intrinsic issues associated with electrode slurry production, as wire-to-wire conductive pathways are formed within the overall electrode active mass of NWs. The conversion from α-AgVO 3 to β-AgVO 3 is explained in detail through a comprehensive structural characterization. Meticulous EELS analysis of β-AgVO 3 NWs offers insight into the true β-AgVO 3 structure and how the annealing process facilitates a higher surface coverage of Ag NPs directly from ionic Ag content within the α-AgVO 3 NWs. Variations in vanadium oxidation state across the surface of the nanowires indicate that the β-AgVO 3 NWs have a core-shell oxidation state structure, and that the vanadium oxidation state under the Ag NP confirms a chemically bound NP from reduction of diffused ionic silver from the α-AgVO 3 NWs core material. Electrochemical comparison of α-AgVO 3 and β-AgVO 3 NWs confirms that β-AgVO 3 offers improved electrochemical performance. An ex situ structural characterization of β-AgVO 3 NWs after the first galvanostatic discharge and charge offers new insight into the Li + reaction

Superconducting properties of Pb82Bi18 films controlled by ferromagnetic nanowire arrays

NASA Astrophysics Data System (ADS)

Ye, Zuxin; Lyuksyutov, Igor F.; Wu, Wenhao; Naugle, Donald G.

2011-02-01

The superconducting properties of Pb82Bi18 alloy films deposited on ferromagnetic nanowire arrays have been investigated. Ferromagnetic Co or Ni nanowires are first electroplated into the columnar pores of anodic aluminum oxide (AAO) membranes. Superconducting Pb82Bi18 films are then quench condensed onto the polished surface of the AAO membranes filled with magnetic nanowires. A strong dependence of the Pb82Bi18 superconducting properties on the ratio of the superconducting film thickness to the magnetic nanowire diameter and material variety was observed.

Photovoltaic devices based on quantum dot functionalized nanowire arrays embedded in an organic matrix

NASA Astrophysics Data System (ADS)

Kung, Patrick; Harris, Nicholas; Shen, Gang; Wilbert, David S.; Baughman, William; Balci, Soner; Dawahre, Nabil; Butler, Lee; Rivera, Elmer; Nikles, David; Kim, Seongsin M.

2012-01-01

Quantum dot (QD) functionalized nanowire arrays are attractive structures for low cost high efficiency solar cells. QDs have the potential for higher quantum efficiency, increased stability and lifetime compared to traditional dyes, as well as the potential for multiple electron generation per photon. Nanowire array scaffolds constitute efficient, low resistance electron transport pathways which minimize the hopping mechanism in the charge transport process of quantum dot solar cells. However, the use of liquid electrolytes as a hole transport medium within such scaffold device structures have led to significant degradation of the QDs. In this work, we first present the synthesis uniform single crystalline ZnO nanowire arrays and their functionalization with InP/ZnS core-shell quantum dots. The structures are characterized using electron microscopy, optical absorption, photoluminescence and Raman spectroscopy. Complementing photoluminescence, transmission electron microanalysis is used to reveal the successful QD attachment process and the atomistic interface between the ZnO and the QD. Energy dispersive spectroscopy reveals the co-localized presence of indium, phosphorus, and sulphur, suggestive of the core-shell nature of the QDs. The functionalized nanowire arrays are subsequently embedded in a poly-3(hexylthiophene) hole transport matrix with a high degree of polymer infiltration to complete the device structure prior to measurement.

Fabrication of ZnO Nanowires Arrays by Anodization and High-Vacuum Die Casting Technique, and Their Piezoelectric Properties

PubMed Central

Kuo, Chin-Guo; Chang, Ho; Wang, Jian-Hao

2016-01-01

In this investigation, anodic aluminum oxide (AAO) with arrayed and regularly arranged nanopores is used as a template in the high-vacuum die casting of molten zinc metal (Zn) into the nanopores. The proposed technique yields arrayed Zn nanowires with an aspect ratio of over 600. After annealing, arrayed zinc oxide (ZnO) nanowires are obtained. Varying the anodizing time yields AAO templates with thicknesses of approximately 50 μm, 60 μm, and 70 μm that can be used in the fabrication of nanowires of three lengths with high aspect ratios. Experimental results reveal that a longer nanowire generates a greater measured piezoelectric current. The ZnO nanowires that are fabricated using an alumina template are anodized for 7 h and produce higher piezoelectric current of up to 69 pA. PMID:27023546

Fabrication of ZnO Nanowires Arrays by Anodization and High-Vacuum Die Casting Technique, and Their Piezoelectric Properties.

PubMed

Kuo, Chin-Guo; Chang, Ho; Wang, Jian-Hao

2016-03-24

In this investigation, anodic aluminum oxide (AAO) with arrayed and regularly arranged nanopores is used as a template in the high-vacuum die casting of molten zinc metal (Zn) into the nanopores. The proposed technique yields arrayed Zn nanowires with an aspect ratio of over 600. After annealing, arrayed zinc oxide (ZnO) nanowires are obtained. Varying the anodizing time yields AAO templates with thicknesses of approximately 50 μm, 60 μm, and 70 μm that can be used in the fabrication of nanowires of three lengths with high aspect ratios. Experimental results reveal that a longer nanowire generates a greater measured piezoelectric current. The ZnO nanowires that are fabricated using an alumina template are anodized for 7 h and produce higher piezoelectric current of up to 69 pA.

Highly Flexible and Transparent Ag Nanowire Electrode Encapsulated with Ultra-Thin Al2O3: Thermal, Ambient, and Mechanical Stabilities

PubMed Central

Hwang, Byungil; An, Youngseo; Lee, Hyangsook; Lee, Eunha; Becker, Stefan; Kim, Yong-Hoon; Kim, Hyoungsub

2017-01-01

There is an increasing demand in the flexible electronics industry for highly robust flexible/transparent conductors that can withstand high temperatures and corrosive environments. In this work, outstanding thermal and ambient stability is demonstrated for a highly transparent Ag nanowire electrode with a low electrical resistivity, by encapsulating it with an ultra-thin Al2O3 film (around 5.3 nm) via low-temperature (100 °C) atomic layer deposition. The Al2O3-encapsulated Ag nanowire (Al2O3/Ag) electrodes are stable even after annealing at 380 °C for 100 min and maintain their electrical and optical properties. The Al2O3 encapsulation layer also effectively blocks the permeation of H2O molecules and thereby enhances the ambient stability to greater than 1,080 h in an atmosphere with a relative humidity of 85% at 85 °C. Results from the cyclic bending test of up to 500,000 cycles (under an effective strain of 2.5%) confirm that the Al2O3/Ag nanowire electrode has a superior mechanical reliability to that of the conventional indium tin oxide film electrode. Moreover, the Al2O3 encapsulation significantly improves the mechanical durability of the Ag nanowire electrode, as confirmed by performing wiping tests using isopropyl alcohol. PMID:28128218

Preparation and enhanced infrared response properties of ordered W-doped VO2 nanowire array

NASA Astrophysics Data System (ADS)

Xie, Bing He; Fu, Wen Biao; Fei, Guang Tao; Xu, Shao Hui; Gao, Xu Dong; Zhang, Li De

2018-04-01

In this article, pure and tungsten-doped (W-doped) highly ordered two-dimensional (2D) vanadium dioxide (VO2) nanowire arrays were successfully prepared by a hydrothermal treatment, followed by a self-assembly progress and the in-situ high temperature treatment. The infrared photodetector devices based on monoclinic VO2 (VO2(M)) and W-doped VO2(M) nanowires were comparatively studied . It was found that the device based on W-doped VO2(M) nanowires exhibits a rapid infrared response and an enhanced photoelectric responsivity of 21.4 mA/W under the incident infrared light intensity of 280 mW/cm2, which is nearly two orders of magnitude superior to pure VO2(M) nanowire array. Our experimental results provided a direct and convenient path for design of future high-performance photodetector devices.

Method for Synthesizing Metal Nanowires in Anodic Alumina Membranes Using Solid State Reduction

NASA Technical Reports Server (NTRS)

Martinez-Inesta, Maria M (Inventor); Feliciano, Jennie (Inventor); Quinones-Fontalvo, Leonel (Inventor)

2016-01-01

The invention proposes a novel method for the fabrication of regular arrays of MNWs using solid-state reduction (SSR). Using this method copper (Cu), silver (Ag), and palladium (Pd) nanowire (NWs) arrays were synthesized using anodic alumina membranes (AAMs) as templates. Depending on the metal loading used the NWs reached different diameters.

Waveguide modes in sparse III-V nanowire arrays for ultra-broadband tunable perfect absorbers (Conference Presentation)

NASA Astrophysics Data System (ADS)

Fountaine, Katherine T.; Cheng, Wen-Hui; Bukowsky, Colton R.; Atwater, Harry A.

2016-09-01

Design of perfect absorbers and emitters has been a primary focus of the metamaterials community owing to their potential to enhance device efficiency and sensitivity in energy harvesting and sensing applications, specifically photovoltaics, thermal emission control, bolometers and photodetectors, to name a few. While reports of perfect absorbers/emitters for a specific frequency, wavevector, and polarization are ubiquitous, a broadband and polarization- and angle-insensitive perfect absorber remains a particular challenge. In this work, we report on directed optical design and fabrication of sparse III-V nanowire arrays as broadband, polarization- and angle-insensitive perfect absorbers and emitters. Specifically, we target response in the UV-Vis-NIR and NIR-SWIR-MWIR via two material systems, InP (Eg=1.34 eV) and InSb (Eg=0.17 eV), respectively. Herein, we present results on InP and InSb nanowire array broadband absorbers, supported by experiment, simulation and analytic theory. Electromagnetic simulations indicate that, with directed optical design, tapered nanowire arrays and multi-radii nanowire arrays with 5% fill fraction can achieve greater than 95% broadband absorption (λInP=400-900nm, λInSb=1.5-5.5µm), due to efficient excitation and interband transition-mediated attenuation of the HE11 waveguide mode. Experimentally-fabricated InP nanowire arrays embedded in PDMS achieved broadband, polarization- and angle-insensitive 90-95% absorption, limited primarily by reflection off the PDMS interface. Addition of a thin, planar VO2 layer above a sparse InSb nanowire array enables active thermal tunability in the infrared, effecting a 50% modulation, from 87% (insulating VO2) to 43% (metallic VO2) average absorption. These concepts and results along with photovoltaic and other optical and optoelectronic device applications will be discussed.

Si-H induced synthesis of Si/Cu2O nanowire arrays for photoelectrochemical water splitting

NASA Astrophysics Data System (ADS)

Zhang, Shaoyang; She, Guangwei; Li, Shengyang; Mu, Lixuan; Shi, Wensheng

2018-01-01

We report a facile and low-cost method to synthesize Si/Cu2O heterojunction nanowire arrays, without SiOx, at the Si/Cu2O interface. The reductive Si-H bonds on the surface of Si nanowires plays a key role in situ by reducing Cu(II) ions to Cu2O nanocubes and avoiding the SiOx interface layer. Different pH values would vary the electrochemical potential of reactions and as a result, different products would be formed. Utilized as a photoanode for water splitting, Si/Cu2O nanowire arrays exhibit good photoelectrochemical performance.

Hierarchically Structured Co3O4@Pt@MnO2 Nanowire Arrays for High-Performance Supercapacitors

NASA Astrophysics Data System (ADS)

Xia, Hui; Zhu, Dongdong; Luo, Zhentao; Yu, Yue; Shi, Xiaoqin; Yuan, Guoliang; Xie, Jianping

2013-10-01

Here we proposed a novel architectural design of a ternary MnO2-based electrode - a hierarchical Co3O4@Pt@MnO2 core-shell-shell structure, where the complemental features of the three key components (a well-defined Co3O4 nanowire array on the conductive Ti substrate, an ultrathin layer of small Pt nanoparticles, and a thin layer of MnO2 nanoflakes) are strategically combined into a single entity to synergize and construct a high-performance electrode for supercapacitors. Owing to the high conductivity of the well-defined Co3O4 nanowire arrays, in which the conductivity was further enhanced by a thin metal (Pt) coating layer, in combination with the large surface area provided by the small MnO2 nanoflakes, the as-fabricated Co3O4@Pt@MnO2 nanowire arrays have exhibited high specific capacitances, good rate capability, and excellent cycling stability. The architectural design demonstrated in this study provides a new approach to fabricate high-performance MnO2-based nanowire arrays for constructing next-generation supercapacitors.

Plasmonic engineering of metal-oxide nanowire heterojunctions in integrated nanowire rectification units

NASA Astrophysics Data System (ADS)

Lin, Luchan; Zou, Guisheng; Liu, Lei; Duley, Walt W.; Zhou, Y. Norman

2016-05-01

We show that irradiation with femtosecond laser pulses can produce robust nanowire heterojunctions in coupled non-wetting metal-oxide Ag-TiO2 structures. Simulations indicate that joining arises from the effect of strong plasmonic localization in the region of the junction. Strong electric field effects occur in both Ag and TiO2 resulting in the modification of both surfaces and an increase in wettability of TiO2, facilitating the interconnection of Ag and TiO2 nanowires. Irradiation leads to the creation of a thin layer of highly defected TiO2 in the contact region between the Ag and TiO2 nanowires. The presence of this layer allows the formation of a heterojunction and offers the possibility of engineering the electronic characteristics of interfacial structures. Rectifying junctions with single and bipolar properties have been generated in Ag-TiO2 nanowire circuits incorporating asymmetrical and symmetrical interfacial structures, respectively. This fabrication technique should be applicable for the interconnection of other heterogeneous metal-oxide nanowire components and demonstrates that femtosecond laser irradiation enables interfacial engineering for electronic applications of integrated nanowire structures.

Enhanced magnetic performance of metal-organic nanowire arrays by FeCo/polypyrrole co-electrodeposition

NASA Astrophysics Data System (ADS)

Luo, X. J.; Xia, W. B.; Gao, J. L.; Zhang, S. Y.; Li, Y. L.; Tang, S. L.; Du, Y. W.

2013-05-01

FeCo/polypyrrole (PPy) composite nanowire array, which shows enhanced magnetic remanence and coercivity along the nanowires, was fabricated by AC electrodeposition using anodic aluminum oxide templates. High resolution transmission electron microscopy shows that PPy grows on the surface of FeCo nanowires forming a coaxial nanowire structure, with a coating layer of about 4 nm. It suggests that the decreased dipolar interaction due to the reduced nanowire diameters is responsible for the enhancement of magnetic performance. The possible mechanism of this coating may be that PPy is inclined to nucleate along the pore wall of the templates.

STEM-EELS analysis of multipole surface plasmon modes in symmetry-broken AuAg nanowire dimers

NASA Astrophysics Data System (ADS)

Schubert, Ina; Sigle, Wilfried; van Aken, Peter A.; Trautmann, Christina; Toimil-Molares, Maria Eugenia

2015-03-01

Surface plasmon coupling in nanowires separated by small gaps generates high field enhancements at the position of the gap and is thus of great interest for sensing applications. It is known that the nanowire dimensions and in particular the symmetry of the structures has strong influence on the plasmonic properties of the dimer structure. Here, we report on multipole surface plasmon coupling in symmetry-broken AuAg nanowire dimers. Our dimers, consisting of two nanowires with different lengths and separated by gaps of only 10 to 30 nm, were synthesized by pulsed electrochemical deposition in ion track-etched polymer templates. Electron energy-loss spectroscopy in scanning transmission electron microscopy allows us to resolve up to nine multipole order surface plasmon modes of these dimers spectrally separated from each other. The spectra evidence plasmon coupling between resonances of different multipole order, resulting in the generation of additional plasmonic modes. Since such complex structures require elaborated synthesis techniques, dimer structures with complex composition, morphology and shape are created. We demonstrate that finite element simulations on pure Au dimers can predict the generated resonances in the fabricated structures. The excellent agreement of our experiment on AuAg dimers with finite integration simulations using CST microwave studio manifests great potential to design complex structures for sensing applications.

Magnetization reversal and coercivity of Fe3Se4 nanowire arrays

NASA Astrophysics Data System (ADS)

Li, D.; Li, S. J.; Zhou, Y. T.; Bai, Y.; Zhu, Y. L.; Ren, W. J.; Long, G.; Zeng, H.; Zhang, Z. D.

2015-05-01

The microstructure and magnetic properties of Fe3Se4 nanowire (NW) arrays in anodic aluminum oxide (AAO) porous membrane are studied. Cross-sectional SEM and plane-view TEM images show that the mean wire diameter (dw) and the center-to-center spacing (D) of Fe3Se4 nanowires are about 220 nm and 330 nm, respectively. The field-cooled magnetization dependent on the temperature indicates a Curie temperature around 334 K for the Fe3Se4 nanowires. The coercivities of Fe3Se4 nanowires at 10 K, obtained from the in-plane and out-of-plane hysteresis loops, are as high as 22.4 kOe and 23.3 kOe, which can be understood from the magnetocrystalline anisotropy and the magnetization reversal process.

Fabrication of porous silicon nanowires by MACE method in HF/H2O2/AgNO3 system at room temperature

PubMed Central

2014-01-01

In this paper, the moderately and lightly doped porous silicon nanowires (PSiNWs) were fabricated by the ‘one-pot procedure’ metal-assisted chemical etching (MACE) method in the HF/H2O2/AgNO3 system at room temperature. The effects of H2O2 concentration on the nanostructure of silicon nanowires (SiNWs) were investigated. The experimental results indicate that porous structure can be introduced by the addition of H2O2 and the pore structure could be controlled by adjusting the concentration of H2O2. The H2O2 species replaces Ag+ as the oxidant and the Ag nanoparticles work as catalyst during the etching. And the concentration of H2O2 influences the nucleation and motility of Ag particles, which leads to formation of different porous structure within the nanowires. A mechanism based on the lateral etching which is catalyzed by Ag particles under the motivation by H2O2 reduction is proposed to explain the PSiNWs formation. PMID:24910568

Transparently wrap-gated semiconductor nanowire arrays for studies of gate-controlled photoluminescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nylund, Gustav; Storm, Kristian; Torstensson, Henrik

2013-12-04

We present a technique to measure gate-controlled photoluminescence (PL) on arrays of semiconductor nanowire (NW) capacitors using a transparent film of Indium-Tin-Oxide (ITO) wrapping around the nanowires as the gate electrode. By tuning the wrap-gate voltage, it is possible to increase the PL peak intensity of an array of undoped InP NWs by more than an order of magnitude. The fine structure of the PL spectrum reveals three subpeaks whose relative peak intensities change with gate voltage. We interpret this as gate-controlled state-filling of luminescing quantum dot segments formed by zincblende stacking faults in the mainly wurtzite NW crystal structure.

Piezo-Phototronic Enhanced UV Sensing Based on a Nanowire Photodetector Array.

PubMed

Han, Xun; Du, Weiming; Yu, Ruomeng; Pan, Caofeng; Wang, Zhong Lin

2015-12-22

A large array of Schottky UV photodetectors (PDs) based on vertical aligned ZnO nanowires is achieved. By introducing the piezo-phototronic effect, the performance of the PD array is enhanced up to seven times in photoreponsivity, six times in sensitivity, and 2.8 times in detection limit. The UV PD array may have applications in optoelectronic systems, adaptive optical computing, and communication. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication of flexible and vertical silicon nanowire electronics.

PubMed

Weisse, Jeffrey M; Lee, Chi Hwan; Kim, Dong Rip; Zheng, Xiaolin

2012-06-13

Vertical silicon nanowire (SiNW) array devices directly connected on both sides to metallic contacts were fabricated on various non-Si-based substrates (e.g., glass, plastics, and metal foils) in order to fully exploit the nanomaterial properties for final applications. The devices were realized with uniform length Ag-assisted electroless etched SiNW arrays that were detached from their fabrication substrate, typically Si wafers, reattached to arbitrary substrates, and formed with metallic contacts on both sides of the NW array. Electrical characterization of the SiNW array devices exhibits good current-voltage characteristics consistent with the SiNW morphology.

Improvement of polypyrrole nanowire devices by plasmonic space charge generation: high photocurrent and wide spectral response by Ag nanoparticle decoration.

PubMed

Lee, S-H; Bae, J; Lee, S W; Jang, J-W

2015-11-07

In this study, improvement of the opto-electronic properties of non-single crystallized nanowire devices with space charges generated by localized surface plasmon resonance (LSPR) is demonstrated. The photocurrent and spectral response of single polypyrrole (PPy) nanowire (NW) devices are increased by electrostatically attached Ag nanoparticles (Ag NPs). To take advantage of plasmon-exciton coupling in the photocurrent of the device, 80 nm of Ag NPs (454 nm = λmax) were chosen for matching the maximum absorption with PPy NWs (442 nm = λmax). The photocurrent density is remarkably improved, up to 25.3 times (2530%), by the Ag NP decoration onto the PPy NW (PPyAgNPs NW) under blue light (λ = 425-475 nm) illumination. In addition, the PPyAgNPs NW shows a photocurrent decay time twice that of PPy NW, as well as an improved spectral response of the photocurrent. The improved photocurrent efficiency, decay time, and spectral response resulted from the space charges generated by the LSPR of Ag NPs. Furthermore, the increasing exponent (m) of the photocurrent (JPC ∼ V(m)) and finite-differential time domain (FDTD) simulation straightforwardly indicate relatively large plasmonic space charge generation under blue light illumination. These results prove that the performance of non-single crystallized polymer nanowire devices can also be improved by plasmonic enhancement.

Time-dependent optical response of three-dimensional Au nanoparticle arrays formed on silica nanowires

NASA Astrophysics Data System (ADS)

Di Mario, Lorenzo; Otomalo, Tadele Orbula; Catone, Daniele; O'Keeffe, Patrick; Tian, Lin; Turchini, Stefano; Palpant, Bruno; Martelli, Faustino

2018-03-01

We present stationary and transient absorption measurements on 3D Au nanoparticle (NP)-decorated Si O2 nanowire arrays. The 3D NP array has been produced by the dewetting of a thin Au film deposited on silica nanowires produced by oxidation of silicon nanowires. The experimental behaviors of the spectral and temporal dynamics observed in the experiment are accurately described by a two-step, three-temperature model. Using an arbitrary set of Au NPs with different aspect ratios, we demonstrate that the width of the experimental spectra, the energy shift of their position with time, and the asymmetry between the two positive wings in the dynamical variation of absorption can all be attributed to the nonuniform shape distribution of the Au NPs in the sample.

Floating compression of Ag nanowire networks for effective strain release of stretchable transparent electrodes

NASA Astrophysics Data System (ADS)

Pyo, Jun Beom; Kim, Byoung Soo; Park, Hyunchul; Kim, Tae Ann; Koo, Chong Min; Lee, Jonghwi; Son, Jeong Gon; Lee, Sang-Soo; Park, Jong Hyuk

2015-10-01

Manipulation of the configuration of Ag nanowire (NW) networks has been pursued to enhance the performance of stretchable transparent electrodes. However, it has remained challenging due to the high Young's modulus and low yield strain of Ag NWs, which lead to their mechanical failure when subjected to structural deformation. We demonstrate that floating a Ag NW network on water and subsequent in-plane compression allows convenient development of a wavy configuration in the Ag NW network, which can release the applied strain. A greatly enhanced electromechanical stability of Ag NW networks can be achieved due to their wavy configuration, while the NW networks maintain the desirable optical and electrical properties. Moreover, the produced NW networks can be transferred to a variety of substrates, offering flexibility for device fabrication. The Ag NW networks with wavy configurations are used as compliant electrodes for dielectric elastomer actuators. The study demonstrates their promising potential to provide improved performance for soft electronic devices.Manipulation of the configuration of Ag nanowire (NW) networks has been pursued to enhance the performance of stretchable transparent electrodes. However, it has remained challenging due to the high Young's modulus and low yield strain of Ag NWs, which lead to their mechanical failure when subjected to structural deformation. We demonstrate that floating a Ag NW network on water and subsequent in-plane compression allows convenient development of a wavy configuration in the Ag NW network, which can release the applied strain. A greatly enhanced electromechanical stability of Ag NW networks can be achieved due to their wavy configuration, while the NW networks maintain the desirable optical and electrical properties. Moreover, the produced NW networks can be transferred to a variety of substrates, offering flexibility for device fabrication. The Ag NW networks with wavy configurations are used as compliant

One-Step Synthesis of Au-Ag Nanowires through Microorganism-Mediated, CTAB-Directed Approach.

PubMed

Xu, Luhang; Huang, Dengpo; Chen, Huimei; Jing, Xiaoling; Huang, Jiale; Odoom-Wubah, Tareque; Li, Qingbiao

2018-05-28

Synthesis and applications of one dimensional (1D) metal nanostructures have attracted much attention. However, one-step synthesis of bimetallic nanowires (NWs) has remained challenging. In this work, we developed a microorganism-mediated, hexadecyltrimethylammonium bromide (CTAB)-directed (MCD) approach to synthesize closely packed and long Au-Ag NWs with the assistance of a continuous injection pump. Characterization results confirmed that the branched Au-Ag alloy NWs was polycrystalline. And the Au-Ag NWs exhibited a strong absorbance at around 1950 nm in the near-infrared (NIR) region, which can find potential application in NIR absorption. In addition, the Au-Ag NWs showed excellent surface-enhanced Raman scattering (SERS) enhancement when 4-mercaptobenzoic acid (MBA) and rhodamine 6G (R6G) were used as probe molecules.

Fabrication and characterization of hexagonally patterned quasi-1D ZnO nanowire arrays

PubMed Central

2014-01-01

Quasi-one-dimensional (quasi-1D) ZnO nanowire arrays with hexagonal pattern have been successfully synthesized via the vapor transport process without any metal catalyst. By utilizing polystyrene microsphere self-assembled monolayer, sol–gel-derived ZnO thin films were used as the periodic nucleation sites for the growth of ZnO nanowires. High-quality quasi-1D ZnO nanowires were grown from nucleation sites, and the original hexagonal periodicity is well-preserved. According to the experimental results, the vapor transport solid condensation mechanism was proposed, in which the sol–gel-derived ZnO film acting as a seed layer for nucleation. This simple method provides a favorable way to form quasi-1D ZnO nanostructures applicable to diverse fields such as two-dimensional photonic crystal, nanolaser, sensor arrays, and other optoelectronic devices. PMID:24521308

Dependence of performance of Si nanowire solar cells on geometry of the nanowires.

PubMed

Khan, Firoz; Baek, Seong-Ho; Kim, Jae Hyun

2014-01-01

The dependence of performance of silicon nanowires (SiNWs) solar cells on the growth condition of the SiNWs has been described. Metal-assisted electroless etching (MAE) technique has been used to grow SiNWs array. Different concentration of aqueous solution containing AgNO3 and HF for Ag deposition is used. The diameter and density of SiNWs are found to be dependent on concentration of solution used for Ag deposition. The diameter and density of SiNWs have been used to calculate the filling ratio of the SINWs arrays. The filling ratio is increased with increase in AgNO3 concentration, whereas it is decreased with increase in HF concentration. The minimum reflectance value achieved is ~1% for SiNWs of length of ~1.2 μ m in the wavelength range of 300-1000 nm. The performance and diode parameters strongly depend on the geometry of SiNWs. The maximum short circuit current density achieved is 35.6 mA/cm(2). The conversion efficiency of solar cell is 9.73% for SiNWs with length, diameter, and wire density of ~1.2 μ m, ~75 nm, and 90 μ m(-2), respectively.

Hierarchically Structured Co3O4@Pt@MnO2 Nanowire Arrays for High-Performance Supercapacitors

PubMed Central

Xia, Hui; Zhu, Dongdong; Luo, Zhentao; Yu, Yue; Shi, Xiaoqin; Yuan, Guoliang; Xie, Jianping

2013-01-01

Here we proposed a novel architectural design of a ternary MnO2-based electrode – a hierarchical Co3O4@Pt@MnO2 core-shell-shell structure, where the complemental features of the three key components (a well-defined Co3O4 nanowire array on the conductive Ti substrate, an ultrathin layer of small Pt nanoparticles, and a thin layer of MnO2 nanoflakes) are strategically combined into a single entity to synergize and construct a high-performance electrode for supercapacitors. Owing to the high conductivity of the well-defined Co3O4 nanowire arrays, in which the conductivity was further enhanced by a thin metal (Pt) coating layer, in combination with the large surface area provided by the small MnO2 nanoflakes, the as-fabricated Co3O4@Pt@MnO2 nanowire arrays have exhibited high specific capacitances, good rate capability, and excellent cycling stability. The architectural design demonstrated in this study provides a new approach to fabricate high-performance MnO2–based nanowire arrays for constructing next-generation supercapacitors. PMID:24132040

Synthesis of β-AgVO3 nanowires decorated with Ag2CrO4, with improved visible light photocatalytic performance

NASA Astrophysics Data System (ADS)

Ouyang, Qi; Li, Zhonghua; Liu, Jiawen

2018-05-01

Silver chromate‑silver vanadate (Ag2CrO4/β-AgVO3) heterojunction composites are synthesized through a facile precipitation process. The Ag2CrO4/β-AgVO3 hybrids obtained exhibit better photocatalytic activity in degradation of RhB than both pure Ag2CrO4 and β-AgVO3 under visible light irradiation. The 20 wt% Ag2CrO4/β-AgVO3 heterojunction possesses the best photocatalytic ability for degrading RhB: 24.4 times that of pristine β-AgVO3 nanowires and 3.2 times that of individual Ag2CrO4 particles. The phase of the nanocomposites was analyzed using x-ray diffraction as well as x-ray photoelectron spectroscopy. Their morphology was observed via scanning electron microscopy and transmission electron microscopy. The improvement in photocatalytic performance is chiefly ascribed to the synergies between Ag2CrO4/β-AgVO3 heterostructure, which can enhance the light absorbance ability and also accelerate the separation and transfer of photoinduced electrons and holes under visible light irradiation; this is also confirmed by UV–vis diffuse reflection spectrometry and fluorescence emission spectra.

Prevalence of information stored in arrays of magnetic nanowires against external fields

NASA Astrophysics Data System (ADS)

Ceballos, D.; Cisternas, E.; Vogel, E. E.; Allende, S.

2018-04-01

Arrays of magnetic nanowires in porous alumina can be used to store information inscribed on the system by orienting the magnetization of selected wires pointing in a desired direction, so symbols can be read as ferromagnetic sectors. However, this information is subject to aging and the stored information could be gradually lost. We investigate here two mechanisms proposed to improve the prevalence of the stored information: opposite ferromagnetic band at the center of the symbol and bi-segmented nanowires acting as two layers of nanowires storing the same information. Both mechanisms prove to increase resistance to the action of external magnetic fields for the case of Ni wires in a geometry compatible with actually grown nanowires. Advantages and disadvantages of these mechanisms are discussed.

Low-haze, annealing-free, very long Ag nanowire synthesis and its application in a flexible transparent touch panel

NASA Astrophysics Data System (ADS)

Moon, Hyunjin; Won, Phillip; Lee, Jinhwan; Ko, Seung Hwan

2016-07-01

Since transparent conducting films based on silver nanowires (AgNWs) have shown higher transmittance and electrical conductivity compared to those of indium tin oxide (ITO) films, the electronics industry has recognized them as promising substitutes. However, due to the higher haze value of AgNW transparent conducting films compared to ITO films, the clarity is decreased when AgNW films are applied to optoelectronic devices. In this study, we develop a highly transparent, low-haze, very long AgNW percolation network. Moreover, we confirm that analyzed chemical roles can easily be applied to different AgNW synthesis methods, and that they have a direct impact on the nanowire shape. Consequently, the lengths of the wires are increased up to 200 μm and the diameters of the wires are decreased up to 45 nm. Using these results, we fabricate highly transparent (96%) conductors (100 Ω/sq) with low-haze (2%) without any annealing process. This electrode shows enhanced clarity compared to previous results due to the decreased diffusive transmittance and scattering. In addition, a flexible touchscreen using a AgNW network is demonstrated to show the performance of modified AgNWs.

Fabrication of vertically aligned Pd nanowire array in AAO template by electrodeposition using neutral electrolyte.

PubMed

Taşaltın, Nevin; Oztürk, Sadullah; Kılınç, Necmettin; Yüzer, Hayrettin; Oztürk, Zaferziya

2010-05-01

A vertically aligned Pd nanowire array was successfully fabricated on an Au/Ti substrate using an anodic aluminum oxide (AAO) template by a direct voltage electrodeposition method at room temperature using diluted neutral electrolyte. The fabrication of Pd nanowires was controlled by analyzing the current-time transient during electrodeposition using potentiostat. The AAO template and the Pd nanowires were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) methods and X-Ray diffraction (XRD). It was observed that the Pd nanowire array was standing freely on an Au-coated Ti substrate after removing the AAO template in a relatively large area of about 5 cm2, approximately 50 nm in diameter and 2.5 μm in length with a high aspect ratio. The nucleation rate and the number of atoms in the critical nucleus were determined from the analysis of current transients. Pd nuclei density was calculated as 3.55 × 108 cm-2. Usage of diluted neutral electrolyte enables slower growing of Pd nanowires owing to increase in the electrodeposition potential and thus obtained Pd nanowires have higher crystallinity with lower dislocations. In fact, this high crystallinity of Pd nanowires provides them positive effect for sensor performances especially.

Fabrication of vertically aligned Pd nanowire array in AAO template by electrodeposition using neutral electrolyte

PubMed Central

2010-01-01

A vertically aligned Pd nanowire array was successfully fabricated on an Au/Ti substrate using an anodic aluminum oxide (AAO) template by a direct voltage electrodeposition method at room temperature using diluted neutral electrolyte. The fabrication of Pd nanowires was controlled by analyzing the current–time transient during electrodeposition using potentiostat. The AAO template and the Pd nanowires were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) methods and X-Ray diffraction (XRD). It was observed that the Pd nanowire array was standing freely on an Au-coated Ti substrate after removing the AAO template in a relatively large area of about 5 cm2, approximately 50 nm in diameter and 2.5 μm in length with a high aspect ratio. The nucleation rate and the number of atoms in the critical nucleus were determined from the analysis of current transients. Pd nuclei density was calculated as 3.55 × 108 cm−2. Usage of diluted neutral electrolyte enables slower growing of Pd nanowires owing to increase in the electrodeposition potential and thus obtained Pd nanowires have higher crystallinity with lower dislocations. In fact, this high crystallinity of Pd nanowires provides them positive effect for sensor performances especially. PMID:20596417

Ag Nanotwin-Assisted Grain Growth-Induced by Stress in SiO₂/Ag/SiO₂ Nanocap Arrays.

PubMed

Zhang, Fan; Wang, Yaxin; Zhang, Yongjun; Chen, Lei; Liu, Yang; Yang, Jinghai

2018-06-14

A trilayer SiO₂/Ag/SiO₂ nanocap array was prepared on a two-dimensional template. When annealed at different temperatures, the curvature of the SiO₂/Ag/SiO₂ nanocap arrays increased, which led to Ag nanocap shrinkage. The stress provided by the curved SiO₂ layer induced the formation of Ag nanotwins. Ag nanotwins assisted the growth of nanoparticles when the neighboring nanotwins changed the local misorientations. Nanocap shrinkage reduced the surface plasmon resonance (SPR) coupling between neighboring nanocaps; concurrently, grain growth decreased the SPR coupling between the particles in each nanocap, which led to a red shift of the localized surface plasmon resonance (LSPR) bands and decreased the surface-enhanced Raman scattering (SERS) signals.

Fabrication of Si/ZnS radial nanowire heterojunction arrays for white light emitting devices on Si substrates.

PubMed

Katiyar, Ajit K; Sinha, Arun Kumar; Manna, Santanu; Ray, Samit K

2014-09-10

Well-separated Si/ZnS radial nanowire heterojunction-based light-emitting devices have been fabricated on large-area substrates by depositing n-ZnS film on p-type nanoporous Si nanowire templates. Vertically oriented porous Si nanowires on p-Si substrates have been grown by metal-assisted chemical etching catalyzed using Au nanoparticles. Isolated Si nanowires with needle-shaped arrays have been made by KOH treatment before ZnS deposition. Electrically driven efficient white light emission from radial heterojunction arrays has been achieved under a low forward bias condition. The observed white light emission is attributed to blue and green emission from the defect-related radiative transition of ZnS and Si/ZnS interface, respectively, while the red arises from the porous surface of the Si nanowire core. The observed white light emission from the Si/ZnS nanowire heterojunction could open up the new possibility to integrate Si-based optical sources on a large scale.

Strikingly enhanced cooling performance for a micro-cooler using unique Cu nanowire array with high electrical conductivity and fast heat transfer behavior

NASA Astrophysics Data System (ADS)

Tan, Ming; Wang, Xiuzhen; Hao, Yanming; Deng, Yuan

2017-06-01

It was found that phonons/electrons are less scattered along (1 1 1)-preferred Cu nanowires than in ordinary structure films and that the interface of Cu nanowires electrode and thermoelectric materials are more compatible. Here highly ordered, high-crystal-quality, high-density Cu nanowire array was successfully fabricated by a magnetron sputtering method. The Cu nanowire array was successfully incorporated using mask-assisted deposition technology as electrodes for thin-film thermoelectric coolers, which would greatly improve electrical/thermal transport and enhance performance of micro-coolers. The cooling performance of the micro-cooler with Cu nanowire array electrode is over 200% higher than that of the cooler with ordinary film electrode.

Size-dependent fracture behavior of silver nanowires.

PubMed

Cao, Ke; Han, Ying; Zhang, Hongti; Gao, Libo; Yang, Hongwei; Chen, Jialin; Li, Yuxiu; Lu, Yang

2018-07-20

Silver (Ag) nanowires have great potential to be used in the flexible electronics industry for their applications in flexible, transparent conductors due to high conductivity and light reflectivity. Those applications always involve mechanical loading and deformations, which requires an in-depth understanding of their mechanical behavior and performance under loadings. However, current understanding on the mechanical properties of Ag nanowires is limited, especially on their size-dependent fracture behavior. In this work, mechanical properties of Ag nanowires with diameters ranging from 50 to 300 nm were systematically studied by in situ TEM tensile testing for the first time. The size effect was clearly found, with the increasing of the diameter of Ag nanowires, the ultimate tensile stress decreased. More importantly, the fracture behavior of Ag nanowire was studied and a brittle-to-ductile transition in fracture behavior was observed at the diameters around 100 nm which could be attributed to the dislocation activities within the geometry confinement. This work could give insights for understanding nanosized Ag wires and the design of Ag nanowire-based flexible devices and touchable panels.

Size-dependent fracture behavior of silver nanowires

NASA Astrophysics Data System (ADS)

Cao, Ke; Han, Ying; Zhang, Hongti; Gao, Libo; Yang, Hongwei; Chen, Jialin; Li, Yuxiu; Lu, Yang

2018-07-01

Silver (Ag) nanowires have great potential to be used in the flexible electronics industry for their applications in flexible, transparent conductors due to high conductivity and light reflectivity. Those applications always involve mechanical loading and deformations, which requires an in-depth understanding of their mechanical behavior and performance under loadings. However, current understanding on the mechanical properties of Ag nanowires is limited, especially on their size-dependent fracture behavior. In this work, mechanical properties of Ag nanowires with diameters ranging from 50 to 300 nm were systematically studied by in situ TEM tensile testing for the first time. The size effect was clearly found, with the increasing of the diameter of Ag nanowires, the ultimate tensile stress decreased. More importantly, the fracture behavior of Ag nanowire was studied and a brittle-to-ductile transition in fracture behavior was observed at the diameters around 100 nm which could be attributed to the dislocation activities within the geometry confinement. This work could give insights for understanding nanosized Ag wires and the design of Ag nanowire-based flexible devices and touchable panels.

From immobilized cells to motile cells on a bed-of-nails: effects of vertical nanowire array density on cell behaviour

PubMed Central

Persson, Henrik; Li, Zhen; Tegenfeldt, Jonas O.; Oredsson, Stina; Prinz, Christelle N.

2015-01-01

The field of vertical nanowire array-based applications in cell biology is growing rapidly and an increasing number of applications are being explored. These applications almost invariably rely on the physical properties of the nanowire arrays, creating a need for a better understanding of how their physical properties affect cell behaviour. Here, we investigate the effects of nanowire density on cell migration, division and morphology for murine fibroblasts. Our results show that few nanowires are sufficient to immobilize cells, while a high nanowire spatial density enables a ”bed-of-nails” regime, where cells reside on top of the nanowires and are fully motile. The presence of nanowires decreases the cell proliferation rate, even in the “bed-of-nails” regime. We show that the cell morphology strongly depends on the nanowire density. Cells cultured on low (0.1 μm−2) and medium (1 μm−2) density substrates exhibit an increased number of multi-nucleated cells and micronuclei. These were not observed in cells cultured on high nanowire density substrates (4 μm−2). The results offer important guidelines to minimize cell-function perturbations on nanowire arrays. Moreover, these findings offer the possibility to tune cell proliferation and migration independently by adjusting the nanowire density, which may have applications in drug testing. PMID:26691936

Core-shell heterojunction of silicon nanowire arrays and carbon quantum dots for photovoltaic devices and self-driven photodetectors.

PubMed

Xie, Chao; Nie, Biao; Zeng, Longhui; Liang, Feng-Xia; Wang, Ming-Zheng; Luo, Linbao; Feng, Mei; Yu, Yongqiang; Wu, Chun-Yan; Wu, Yucheng; Yu, Shu-Hong

2014-04-22

Silicon nanostructure-based solar cells have lately intrigued intensive interest because of their promising potential in next-generation solar energy conversion devices. Herein, we report a silicon nanowire (SiNW) array/carbon quantum dot (CQD) core-shell heterojunction photovoltaic device by directly coating Ag-assisted chemical-etched SiNW arrays with CQDs. The heterojunction with a barrier height of 0.75 eV exhibited excellent rectifying behavior with a rectification ratio of 10(3) at ±0.8 V in the dark and power conversion efficiency (PCE) as high as 9.10% under AM 1.5G irradiation. It is believed that such a high PCE comes from the improved optical absorption as well as the optimized carrier transfer and collection capability. Furthermore, the heterojunction could function as a high-performance self-driven visible light photodetector operating in a wide switching wavelength with good stability, high sensitivity, and fast response speed. It is expected that the present SiNW array/CQD core-shell heterojunction device could find potential applications in future high-performance optoelectronic devices.

Ag@Ni core-shell nanowire network for robust transparent electrodes against oxidation and sulfurization.

PubMed

Eom, Hyeonjin; Lee, Jaemin; Pichitpajongkit, Aekachan; Amjadi, Morteza; Jeong, Jun-Ho; Lee, Eungsug; Lee, Jung-Yong; Park, Inkyu

2014-10-29

Silver nanowire (Ag NW) based transparent electrodes are inherently unstable to moist and chemically reactive environment. A remarkable stability improvement of the Ag NW network film against oxidizing and sulfurizing environment by local electrodeposition of Ni along Ag NWs is reported. The optical transmittance and electrical resistance of the Ni deposited Ag NW network film can be easily controlled by adjusting the morphology and thickness of the Ni shell layer. The electrical conductivity of the Ag NW network film is increased by the Ni coating via welding between Ag NWs as well as additional conductive area for the electron transport by electrodeposited Ni layer. Moreover, the chemical resistance of Ag NWs against oxidation and sulfurization can be dramatically enhanced by the Ni shell layer electrodeposited along the Ag NWs, which provides the physical barrier against chemical reaction and diffusion as well as the cathodic protection from galvanic corrosion. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Scalable Direct Writing of Lanthanide-Doped KMnF3 Perovskite Nanowires into Aligned Arrays with Polarized Up-Conversion Emission.

PubMed

Shi, Shuo; Sun, Ling-Dong; Xue, Ying-Xian; Dong, Hao; Wu, Ke; Guo, Shi-Chen; Wu, Bo-Tao; Yan, Chun-Hua

2018-05-09

The use of one-dimensional nano- and microstructured semiconductor and lanthanide materials is attractive for polarized-light-emission studies. Up-conversion emission from single-nanorod or anisotropic nanoparticles with a degree of polarization has also been discussed. However, microscale arrays of nanoparticles, especially well-aligned one-dimensional nanostructures as well as their up-conversion polarization characterization, have not been investigated yet. Herein, we present a novel and facile paradigm for preparing highly aligned arrays of lanthanide-doped KMnF 3 (KMnF 3 :Ln) perovskite nanowires, which are good candidates for polarized up-conversion emission studies. These perovskite nanowires, with a width of 10 nm and length of a few micrometers, are formed through the oriented attachment of KMnF 3 :Ln nanocubes along the [001] direction. By the employment of KMnF 3 :Ln nanowire gel as nanoink, a direct-writing method is developed to obtain diverse types of aligned patterns from the nanoscale to the wafer scale. Up-conversion emissions from the highly aligned nanowire arrays are polarized along the array direction with a polarization degree up to 60%. Taking advantage of microscopic nanowire arrays, these polarized up-conversion emissions should offer potential applications in light or information transportation.

Piezo-Phototronic Matrix via a Nanowire Array.

PubMed

Zhang, Yang; Zhai, Junyi; Wang, Zhong Lin

2017-12-01

Piezoelectric semiconductors, such as ZnO and GaN, demonstrate multiproperty coupling effects toward various aspects of mechanical, electrical, and optical excitation. In particular, the three-way coupling among semiconducting, photoexcitation, and piezoelectric characteristics in wurtzite-structured semiconductors is established as a new field, which was first coined as piezo-phototronics by Wang in 2010. The piezo-phototronic effect can controllably modulate the charge-carrier generation, separation, transport, and/or recombination in optical-electronic processes by modifying the band structure at the metal-semiconductor or semiconductor-semiconductor heterojunction/interface. Here, the progress made in using the piezo-phototronic effect for enhancing photodetectors, pressure sensors, light-emitting diodes, and solar cells is reviewed. In comparison with previous works on a single piezoelectric semiconducting nanowire, piezo-phototronic nanodevices built using nanowire arrays provide a promising platform for fabricating integrated optoelectronics with the realization of high-spatial-resolution imaging and fast responsivity. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transparent arrays of silver nanowire rings driven by evaporation of sessile droplets

NASA Astrophysics Data System (ADS)

Wang, Xiaofeng; Kang, Giho; Seong, Baekhoon; Chae, Illkyeong; Teguh Yudistira, Hadi; Lee, Hyungdong; Kim, Hyunggun; Byun, Doyoung

2017-11-01

A coffee-ring pattern can be yielded on the three-phase contact line following evaporation of sessile droplets with suspended insoluble solutes, such as particles, DNA molecules, and mammalian cells. The formation of such coffee-ring, together with their suppression has been applied in printing and coating technologies. We present here an experimental study on the assembly of silver nanowires inside an evaporating droplet of a colloidal suspension. The effects of nanowire length and concentration on coffee-ring formation of the colloidal suspension were investigated. Several sizes of NWs with an aspect ratio between 50 and 1000 were systematically investigated to fabricate coffee-ring patterns. Larger droplets containing shorter nanowires formed clearer ring deposits after evaporation. An order-to-disorder transition of the nanowires’ alignment was found inside the rings. A printing technique with the evaporation process enabled fabrication of arrays of silver nanowire rings. We could manipulate the patterns silver nanowire rings, which might be applied to the transparent and flexible electrode.

Growth of high-aspect ratio horizontally-aligned ZnO nanowire arrays.

PubMed

Soman, Pranav; Darnell, Max; Feldman, Marc D; Chen, Shaochen

2011-08-01

A method of fabricating horizontally-aligned zinc-oxide (ZnO) nanowire (NW) arrays with full control over the width and length is demonstrated. SEM images reveal the hexagonal structure typical of zinc oxide NWs. Arrays of high-aspect ratio horizontal ZnO NWs are fabricated by making use of the lateral overgrowth from dot patterns created by electron beam lithography (EBL). An array of patterned wires are lifted off and transferred to a flexible PDMS substrate with possible applications in several key nanotechnology areas.

Three-Dimensional Porous Iron Vanadate Nanowire Arrays as a High-Performance Lithium-Ion Battery.

PubMed

Cao, Yunhe; Fang, Dong; Liu, Ruina; Jiang, Ming; Zhang, Hang; Li, Guangzhong; Luo, Zhiping; Liu, Xiaoqing; Xu, Jie; Xu, Weilin; Xiong, Chuanxi

2015-12-23

Development of three-dimensional nanoarchitectures on current collectors has emerged as an effective strategy for enhancing rate capability and cycling stability of the electrodes. Herein, a new type of three-dimensional porous iron vanadate (Fe0.12V2O5) nanowire arrays on a Ti foil has been synthesized by a hydrothermal method. The as-prepared Fe0.12V2O5 nanowires are about 30 nm in diameter and several micrometers in length. The effect of reaction time on the resulting morphology is investigated and the mechanism for the nanowire formation is proposed. As an electrode material used in lithium-ion batteries, the unique configuration of the Fe0.12V2O5 nanowire arrays presents enhanced capacitance, satisfying rate capability and good cycling stability, as evaluated by cyclic voltammetry and galvanostatic discharge-charge cycling. It delivers a high discharge capacity of 293 mAh·g(-1) at 2.0-3.6 V or 382.2 mAh·g(-1) at 1.0-4.0 V after 50 cycles at 30 mA·g(-1).

Heterogeneous NiCo2O4@polypyrrole core/sheath nanowire arrays on Ni foam for high performance supercapacitors

NASA Astrophysics Data System (ADS)

Hu, Jing; Li, Minchan; Lv, Fucong; Yang, Mingyang; Tao, Pengpeng; Tang, Yougen; Liu, Hongtao; Lu, Zhouguang

2015-10-01

A novel heterogeneous NiCo2O4@PPy core/sheath nanowire arrays are directly grown on Ni foam involving three facile steps, hydrothermal synthesis and calcination of NiCo2O4 nanowire arrays and subsequent in-situ oxidative polymerization of polypyrrole (PPy). When investigated as binder- and conductive additive-free electrodes for supercapacitors (SCs) in 6 M KOH, the NiCo2O4@PPy core/sheath nanowire arrays exhibit high areal capacitance of 3.49 F cm-2 at a discharge current density of 5 mA cm-2, which is almost 1.5 times as much as the pristine NiCo2O4 (2.30 F cm-2). More importantly, it can remain 3.31 F cm-2 (94.8% retention) after 5000 cycles. The as-obtained electrode also displays excellent rate capability, whose areal capacitance can still remain 2.79 F cm-2 while the discharge current density is increased to 50 mA cm-2. The remarkable electrochemical performance is mainly attributed to the unique heterogeneous core/sheath nanowire-array architectures.

Facile synthesis of PdAgTe nanowires with superior electrocatalytic activity

NASA Astrophysics Data System (ADS)

Hong, Wei; Wang, Jin; Wang, Erkang

2014-12-01

In this work, ultrathin Te nanowires (NWs) with high-aspect-ratio are prepared by a simple hydrothermal method. By using Te NWs as the sacrificial template, we demonstrate a facile and efficient method for the synthesis of PdAgTe NWs with high-quality through the partly galvanic replacement between Te NWs and the corresponding noble metal salts precursors in an aqueous solution. The compositions of PdAgTe NWs can be tuned by simply altering the concentration of the precursors. After cyclic voltammetry treatment, multi-component PdAgTe NW with a highly active and stable surface can be obtained. The structure and composition of the as-prepared nanomaterials are analyzed by transmission electron microscope, X-ray diffraction, energy dispersive X-ray spectroscopy, inductively coupled plasma-mass spectroscopy and X-ray photoelectron spectroscopy. Electrochemical catalytic measurement results prove that the as synthesized PdAgTe NWs present superior catalytic activity toward ethanol electrooxidation in alkaline solution than the commercial Pd/C catalyst, which making them can be used as effective catalysts for the direct ethanol fuel cells.

Temperature-dependent structure and phase variation of nickel silicide nanowire arrays prepared by in situ silicidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Hailong; She, Guangwei, E-mail: shegw@mail.ipc.ac.cn; Mu, Lixuan

Graphical abstract: Display Omitted Highlight: ► Nickel silicides nanowire arrays prepared by a simple in situ silicidation method. ► Phases of nickel silicides could be varied by tuning the reaction temperature. ► A growth model was proposed for the nickel silicides nanowires. ► Diffusion rates of Ni and Si play a critical role for the phase variation. -- Abstract: In this paper, we report an in situ silicidizing method to prepare nickel silicide nanowire arrays with varied structures and phases. The in situ reaction (silicidation) between Si and NiCl{sub 2} led to conversion of Si nanowires to nickel silicide nanowires.more » Structures and phases of the obtained nickel silicides could be varied by changing the reaction temperature. At a relatively lower temperature of 700 °C, the products are Si/NiSi core/shell nanowires or NiSi nanowires, depending on the concentration of NiCl{sub 2} solution. At a higher temperature (800 °C and 900 °C), other phases of the nickel silicides, including Ni{sub 2}Si, Ni{sub 31}Si{sub 12}, and NiSi{sub 2}, were obtained. It is proposed that the different diffusion rates of Ni and Si atoms at different temperatures played a critical role in the formation of nickel silicide nanowires with different phases.« less

Engineered ZnO nanowire arrays using different nanopatterning techniques

NASA Astrophysics Data System (ADS)

Volk, János; Szabó, Zoltán; Erdélyi, Róbert; Khánh, Nguyen Q.

2012-02-01

The impact of various masking patterns and template layers on the wet chemically grown vertical ZnO nanowire arrays was investigated. The nanowires/nanorods were seeded at nucleation windows which were patterned in a mask layer using various techniques such as electron beam lithography, nanosphere photolithography, and atomic force microscope type nanolithography. The compared ZnO templates included single crystals, epitaxial layer, and textured polycrystalline films. Scanning electron microscopy revealed that the alignment and crystal orientation of the nanowires were dictated by the underlying seed layer, while their geometry can be tuned by the parameters of the certain nanopatterning technique and of the wet chemical process. The comparison of the alternative nanolithography techniques showed that using direct writing methods the diameter of the ordered ZnO nanowires can be as low as 30-40 nm at a density of 100- 1000 NW/μm2 in a very limited area (10 μm2-1 mm2). Nanosphere photolithography assisted growth, on the other hand, favors thicker nanopillars (~400 nm) and enables large-area, low-cost patterning (1-100 cm2). These alternative lowtemperature fabrication routes can be used for different novel optoelectronic devices, such as nanorod based ultraviolet photodiode, light emitting device, and waveguide laser.

Efficiency enhancement of organic solar cells using transparent plasmonic Ag nanowire electrodes.

PubMed

Kang, Myung-Gyu; Xu, Ting; Park, Hui Joon; Luo, Xiangang; Guo, L Jay

2010-10-15

Surface plasmon enhanced photo-current and power conversion efficiency of organic solar cells using periodic Ag nanowires as transparent electrodes are reported, as compared to the device with conventional ITO electrodes. External quantum efficiencies are enhanced about 2.5 fold around the peak solar spectrum wavelength of 560 nm, resulting in 35% overall increase in power conversion efficiency than the ITO control device under normal unpolarized light.

Aluminum Nanowire Arrays via Soft Nanoimprint Lithography

NASA Astrophysics Data System (ADS)

Naughton, Michael J.; Nesbitt, Nathan T.; Merlo, Juan M.; Rose, Aaron H.; Calm, Yitzi M.; D'Imperio, Luke A.; Courtney, Dave T.; Shepard, Steve; Kempa, Krzysztof; Burns, Michael J.

We have previously reported a method to fabricate freestanding, vertically-oriented, and lithographically-ordered Al nanowire arrays via directed assembly, and demonstrated their utility as a plasmonic waveguide. However, the process, a variation on the preparation of anodized aluminum oxide (AAO), involved imprinting Al with a hard stamp, which wore down the stamp and had a low yield of Al NWs. Here we show a new nanoimprint lithography (NIL) technique that uses a soft stamp to pattern a mask on the Al; it provides a greater yield of Al NWs and is less destructive to the stamp, providing a path to applications that require NW arrays over macroscopic areas. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. (DGE-1258923).

Magnetization mechanisms in ordered arrays of polycrystalline Fe100-xCox nanowires

NASA Astrophysics Data System (ADS)

Viqueira, M. S.; Bajales, N.; Urreta, S. E.; Bercoff, P. G.

2015-05-01

Magnetization reversal processes and coercivity mechanisms in polycrystalline Fe100-xCox nanowire arrays, resulting from an AC electrodeposition process, are investigated. The array coercivity is described on the basis of polarization reversal mechanisms operating in individual wires, under the effect of inter-wire dipolar interactions described by a mean field approximation. For individual wires, a reversal mechanism involving the nucleation and further expansion of domain-wall like spin configuration is considered. The wires have a mean grain size larger than both the nanowire diameter and the exchange length, so localized and non-cooperative nucleation modes are considered. As the Co content increases, the alloy saturation polarization gradually decreases, but the coercive field and the relative remanence of the arrays increase, indicating that they are not controlled by the shape anisotropy in all the composition range. The coercive field dependence on the angle between the applied field and the wire long axis is not well described by reversal mechanisms involving nucleation and further displacement of neither vortex nor transverse ideal domain walls. On the contrary, the angular dependence of the coercive field observed at room temperature is well predicted by a model considering nucleation of inverse domains by localized curling, in regions smaller than the grain size, exhibiting quite small aspect ratios as compared to those of the entire nanowire. In arrays with higher Co contents, a transition from an initial (small angle) localized curling nucleation mechanism to another one, involving localized coherent rotation is observed at about π/4.

The Self- and Directed Assembly of Nanowires

NASA Astrophysics Data System (ADS)

Smith, Benjamin David

nanowires rapidly sedimented due to gravity onto a glass cover slip to concentrate and form a dense film. Particles and assemblies were imaged using inverted optical microscopy. We quantitatively analyzed the images and movies captured in order to track and classify particles and classify the overall arrays formed. We then correlated how particle characteristics, e.g., materials, size, segmentation, etc. changed the ordering and alignment observed. With that knowledge, we hope to be able to form new and interesting structures. We began our studies by examining the assembly of single component nanowires. Chapter 2 describes this work, in which solid Au nanowires measuring 2-7 mum in length and 290 nm in diameter self-assembled into smectic rows. By both experiment and theory, we determined that these rows formed due to a balance of electrostatic repulsions and van der Waals attractions. Final assemblies were stable for at least several days. Monte Carlo methods were used to simulate assemblies and showed structures that mirrored those experimentally observed. Simulations indicated that the smectic phase was preferred over others, i.e., nematic, when an additional small charge was added to the ends of the nanowires. Our particles have rough tips, which might create these additional electrostatic repulsions. To increase the particle and array complexity, two-component, metallic nanowire assembly was explored in Chapter 3. We examined numerous types of nanowires by changing the segment length, ratio, and material, the nanowire length, the surface coating, and the presence of small third segments. These segmented nanowires were generally Au-Ag and also ordered into smectic rows. Segmented wires arranged in rows, however, can be aligned in two possible ways with respect to a neighboring particle. The Au segments on neighboring particles can be oriented in the same direction or opposed to each other. Orientation was quantified in terms of an order parameter that took into account

Interactions and reversal-field memory in complex magnetic nanowire arrays

NASA Astrophysics Data System (ADS)

Rotaru, Aurelian; Lim, Jin-Hee; Lenormand, Denny; Diaconu, Andrei; Wiley, John. B.; Postolache, Petronel; Stancu, Alexandru; Spinu, Leonard

2011-10-01

Interactions and magnetization reversal of Ni nanowire arrays have been investigated by the first-order reversal curve (FORC) method. Several series of samples with controlled spatial distribution were considered including simple wires of different lengths and diameters (70 and 110 nm) and complex wires with a single modulated diameter along their length. Subtle features of magnetic interactions are revealed through a quantitative analysis of the local interaction field profile distributions obtained from the FORC method. In addition, the FORC analysis indicates that the nanowire systems with a mean diameter of 70 nm appear to be organized in symmetric clusters indicative of a reversal-field memory effect.

Highly organised and dense vertical silicon nanowire arrays grown in porous alumina template on <100> silicon wafers

PubMed Central

2013-01-01

In this work, nanoimprint lithography combined with standard anodization etching is used to make perfectly organised triangular arrays of vertical cylindrical alumina nanopores onto standard <100>−oriented silicon wafers. Both the pore diameter and the period of alumina porous array are well controlled and can be tuned: the periods vary from 80 to 460 nm, and the diameters vary from 15 nm to any required diameter. These porous thin layers are then successfully used as templates for the guided epitaxial growth of organised mono-crystalline silicon nanowire arrays in a chemical vapour deposition chamber. We report the densities of silicon nanowires up to 9 × 109 cm−2 organised in highly regular arrays with excellent diameter distribution. All process steps are demonstrated on surfaces up to 2 × 2 cm2. Specific emphasis was made to select techniques compatible with microelectronic fabrication standards, adaptable to large surface samples and with a reasonable cost. Achievements made in the quality of the porous alumina array, therefore on the silicon nanowire array, widen the number of potential applications for this technology, such as optical detectors or biological sensors. PMID:23773702

Frequency-multiplexed bias and readout of a 16-pixel superconducting nanowire single-photon detector array

NASA Astrophysics Data System (ADS)

Doerner, S.; Kuzmin, A.; Wuensch, S.; Charaev, I.; Boes, F.; Zwick, T.; Siegel, M.

2017-07-01

We demonstrate a 16-pixel array of microwave-current driven superconducting nanowire single-photon detectors with an integrated and scalable frequency-division multiplexing architecture, which reduces the required number of bias and readout lines to a single microwave feed line. The electrical behavior of the photon-sensitive nanowires, embedded in a resonant circuit, as well as the optical performance and timing jitter of the single detectors is discussed. Besides the single pixel measurements, we also demonstrate the operation of a 16-pixel array with a temporal, spatial, and photon-number resolution.

Ultra-thin g-C{sub 3}N{sub 4} nanosheets wrapped silicon nanowire array for improved chemical stability and enhanced photoresponse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Beibei; Yu, Hongtao; Quan, Xie, E-mail: quanxie@dlut.edu.cn

2014-11-15

Highlights: • g-C{sub 3}N{sub 4}, as an oxygen free and metal free protective material for Si, was proposed. • g-C{sub 3}N{sub 4} nanosheets wrapped Si nanowire array was synthesized. • SiNW/g-C{sub 3}N{sub 4} exhibited enhancement of photoelectrochemical stability and photocurrent. - Abstract: In order to inhibit the oxidation of Si materials in aqueous solution, Si nanowire array was wrapped by ultra-thin g-C{sub 3}N{sub 4} nanosheets via an electrophoresis process. Scanning electron microscopy and transmission electron microscopy images showed that g-C{sub 3}N{sub 4} nanosheets were evenly distributed on the surface of Si nanowire array. X-ray diffraction patterns indicated that Si nanowiremore » array/g-C{sub 3}N{sub 4} nanosheets were composed of Si (4 0 0 crystal plane) and g-C{sub 3}N{sub 4} (0 0 2 and 1 0 0 crystal planes). The cyclic voltammetry curves revealed that the corrosion of Si nanowire array was restrained under the protection of g-C{sub 3}N{sub 4} nanosheets. Furthermore, the photocurrent density of Si nanowire array/g-C{sub 3}N{sub 4} nanosheets increased by nearly 3 times compared to that of bare Si nanowire array due to the effective charge separation caused by the built-in electric field at the interface. This work will facilitate the applications of Si materials in aqueous solution, such as solar energy harvest and photocatalytic pollution control.« less

Template-directed atomically precise self-organization of perfectly ordered parallel cerium silicide nanowire arrays on Si(110)-16 × 2 surfaces.

PubMed

Hong, Ie-Hong; Liao, Yung-Cheng; Tsai, Yung-Feng

2013-11-05

The perfectly ordered parallel arrays of periodic Ce silicide nanowires can self-organize with atomic precision on single-domain Si(110)-16 × 2 surfaces. The growth evolution of self-ordered parallel Ce silicide nanowire arrays is investigated over a broad range of Ce coverages on single-domain Si(110)-16 × 2 surfaces by scanning tunneling microscopy (STM). Three different types of well-ordered parallel arrays, consisting of uniformly spaced and atomically identical Ce silicide nanowires, are self-organized through the heteroepitaxial growth of Ce silicides on a long-range grating-like 16 × 2 reconstruction at the deposition of various Ce coverages. Each atomically precise Ce silicide nanowire consists of a bundle of chains and rows with different atomic structures. The atomic-resolution dual-polarity STM images reveal that the interchain coupling leads to the formation of the registry-aligned chain bundles within individual Ce silicide nanowire. The nanowire width and the interchain coupling can be adjusted systematically by varying the Ce coverage on a Si(110) surface. This natural template-directed self-organization of perfectly regular parallel nanowire arrays allows for the precise control of the feature size and positions within ±0.2 nm over a large area. Thus, it is a promising route to produce parallel nanowire arrays in a straightforward, low-cost, high-throughput process.

Template-directed atomically precise self-organization of perfectly ordered parallel cerium silicide nanowire arrays on Si(110)-16 × 2 surfaces

PubMed Central

2013-01-01

The perfectly ordered parallel arrays of periodic Ce silicide nanowires can self-organize with atomic precision on single-domain Si(110)-16 × 2 surfaces. The growth evolution of self-ordered parallel Ce silicide nanowire arrays is investigated over a broad range of Ce coverages on single-domain Si(110)-16 × 2 surfaces by scanning tunneling microscopy (STM). Three different types of well-ordered parallel arrays, consisting of uniformly spaced and atomically identical Ce silicide nanowires, are self-organized through the heteroepitaxial growth of Ce silicides on a long-range grating-like 16 × 2 reconstruction at the deposition of various Ce coverages. Each atomically precise Ce silicide nanowire consists of a bundle of chains and rows with different atomic structures. The atomic-resolution dual-polarity STM images reveal that the interchain coupling leads to the formation of the registry-aligned chain bundles within individual Ce silicide nanowire. The nanowire width and the interchain coupling can be adjusted systematically by varying the Ce coverage on a Si(110) surface. This natural template-directed self-organization of perfectly regular parallel nanowire arrays allows for the precise control of the feature size and positions within ±0.2 nm over a large area. Thus, it is a promising route to produce parallel nanowire arrays in a straightforward, low-cost, high-throughput process. PMID:24188092

Seesaw-like polarized transmission behavior of silver nanowire arrays aligned by off-center spin-coating

NASA Astrophysics Data System (ADS)

Kang, Lu; Chen, Hui; Yang, Zhong-Jian; Yuan, Yongbo; Huang, Han; Yang, Bingchu; Gao, Yongli; Zhou, Conghua

2018-05-01

Straight silver nanowires were synthesized by accelerated oxidization and then aligned into ordered arrays by off-center spin-coating. Seesaw-like behavior was observed in the polarized transmission spectra of the arrays. With the increment of polarization angle (θP, defined as the angle between axis of nanowires and direction of electric field of light), transmission changed repeatedly with a period of 180°, but it moved to opposite directions between the two regions separated by supporting points locating at 494 nm. The behavior is ascribed to the competition between the extinction behaviors of the two modes of surface plasma polaritons on silver nanowires. One is the longitudinal mode which is excited by long wavelengths and tuned by function of cos2( θ p ) and the other is the transverse mode that is excited by short wavelengths and tuned by function of sin2( θ p ). Simulation was performed based on the finite-difference time domain method. The effect of the nanowire diameter and length (aspect ratio) on the position of the supporting point was studied. As nanowire width increased from 20 nm to 350 nm, the supporting point moved from 400 to 500 nm. While it changed slightly when the nanowire length increased from 3 μm to infinitely long (width fixed at 260 nm). In current study, the position of the supporting point is mainly determined by the nanowire width.

Epitaxial-Growth-Induced Junction Welding of Silver Nanowire Network Electrodes.

PubMed

Kang, Hyungseok; Song, Sol-Ji; Sul, Young Eun; An, Byeong-Seon; Yin, Zhenxing; Choi, Yongsuk; Pu, Lyongsun; Yang, Cheol-Woong; Kim, Youn Sang; Cho, Sung Min; Kim, Jung-Gu; Cho, Jeong Ho

2018-05-22

In this study, we developed a roll-to-roll Ag electroplating process for metallic nanowire electrodes using a galvanostatic mode. Electroplating is a low-cost and facile method for deposition of metal onto a target surface with precise control of both the composition and the thickness. Metallic nanowire networks [silver nanowires (AgNWs) and copper nanowires (CuNWs)] coated onto a polyethylene terephthalate (PET) film were immersed directly in an electroplating bath containing AgNO 3 . Solvated silver ions (Ag + ions) were deposited onto the nanowire surface through application of a constant current via an external circuit between the nanowire networks (cathode) and a Ag plate (anode). The amount of electroplated Ag was systematically controlled by changing both the applied current density and the electroplating time, which enabled precise control of the sheet resistance and optical transmittance of the metallic nanowire networks. The optimized Ag-electroplated AgNW (Ag-AgNW) films exhibited a sheet resistance of ∼19 Ω/sq at an optical transmittance of 90% (550 nm). A transmission electron microscopy study confirmed that Ag grew epitaxially on the AgNW surface, but a polycrystalline Ag structure was formed on the CuNW surface. The Ag-electroplated metallic nanowire electrodes were successfully applied to various electronic devices such as organic light-emitting diodes, triboelectric nanogenerators, and a resistive touch panel. The proposed roll-to-roll Ag electroplating process provides a simple, low-cost, and scalable method for the fabrication of enhanced transparent conductive electrode materials for next-generation electronic devices.

Air-bridged Ohmic contact on vertically aligned si nanowire arrays: application to molecule sensors.

PubMed

Han, Hee; Kim, Jungkil; Shin, Ho Sun; Song, Jae Yong; Lee, Woo

2012-05-02

A simple, cost-effective, and highly reliable method for constructing an air-bridged electrical contact on large arrays of vertically aligned nanowires was developed. The present method may open up new opportunities for developing advanced nanowire-based devices for energy harvest and storage, power generation, and sensing applications. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Volumetric Heating of Ultra-High Energy Density Relativistic Plasmas by Ultrafast Laser Irradiation of Aligned Nanowire Arrays

NASA Astrophysics Data System (ADS)

Bargsten, Clayton; Hollinger, Reed; Shlyaptsev, Vyacheslav; Pukhov, Alexander; Keiss, David; Townsend, Amanda; Wang, Yong; Wang, Shoujun; Prieto, Amy; Rocca, Jorge

2014-10-01

We have demonstrated the volumetric heating of near-solid density plasmas to keV temperatures by ultra-high contrast femtosecond laser irradiation of arrays of vertically aligned nanowires with an average density up to 30% solid density. X-ray spectra show that irradiation of Ni and Au nanowire arrays with laser pulses of relativistic intensities ionizes plasma volumes several micrometers in depth to the He-like and Co-like (Au 52 +) stages respectively. The penetration depth of the heat into the nanowire array was measured monitoring He-like Co lines from irradiated arrays in which the nanowires are composed of a Co segment buried under a selected length of Ni. The measurement shows the ionization reaches He-like Co for depth of up to 5 μm within the target. This volumetric plasma heating approach creates a new laboratory plasma regime in which extreme plasma parameters can be accessed with table-top lasers. Scaling to higher laser intensities promises to create plasmas with temperatures and pressures approaching those in the center of the sun. Work supported by the U.S Department of Energy, Fusion Energy Sciences and the Defense Threat Reduction Agency grant HDTRA-1-10-1-0079. A.P was supported by of DFG-funded project TR18.

Fabrication of ordered NiO coated Si nanowire array films as electrodes for a high performance lithium ion battery.

PubMed

Qiu, M C; Yang, L W; Qi, X; Li, Jun; Zhong, J X

2010-12-01

Highly ordered NiO coated Si nanowire array films are fabricated as electrodes for a high performance lithium ion battery via depositing Ni on electroless-etched Si nanowires and subsequently annealing. The structures and morphologies of as-prepared films are characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. When the potential window versus lithium was controlled, the coated NiO can be selected to be electrochemically active to store and release Li+ ions, while highly conductive crystalline Si cores function as nothing more than a stable mechanical support and an efficient electrical conducting pathway. The hybrid nanowire array films exhibit superior cyclic stability and reversible capacity compared to that of NiO nanostructured films. Owing to the ease of large-scale fabrication and superior electrochemical performance, these hybrid nanowire array films will be promising anode materials for high performance lithium-ion batteries.

High yield of self-catalyzed GaAs nanowire arrays grown on silicon via gallium droplet positioning.

PubMed

Plissard, S; Larrieu, G; Wallart, X; Caroff, P

2011-07-08

We report and detail a method to achieve growth of vertical self-catalyzed GaAs nanowires directly on Si(111) with a near-perfect vertical yield, using electron-beam-defined arrays of holes in a dielectric layer and molecular beam epitaxy. In our conditions, GaAs nanowires are grown along a vapor-liquid-solid mechanism, using in situ self-forming Ga droplets. The focus of this paper is to understand the role of the substrate preparation and of the pre-growth conditioning. Without changing temperature or the V/III ratio, the yield of vertical nanowires is increased incrementally up to 95%. The possibility to achieve very dense arrays, with center-to-center inter-wire distances less than 100 nm, is demonstrated.

Macroscopic Quantum Tunneling in Superconducting Junctions of β-Ag2Se Topological Insulator Nanowire.

PubMed

Kim, Jihwan; Kim, Bum-Kyu; Kim, Hong-Seok; Hwang, Ahreum; Kim, Bongsoo; Doh, Yong-Joo

2017-11-08

We report on the fabrication and electrical transport properties of superconducting junctions made of β-Ag 2 Se topological insulator (TI) nanowires in contact with Al superconducting electrodes. The temperature dependence of the critical current indicates that the superconducting junction belongs to a short and diffusive junction regime. As a characteristic feature of the narrow junction, the critical current decreases monotonously with increasing magnetic field. The stochastic distribution of the switching current exhibits the macroscopic quantum tunneling behavior, which is robust up to T = 0.8 K. Our observations indicate that the TI nanowire-based Josephson junctions can be a promising building block for the development of nanohybrid superconducting quantum bits.

Highly aligned arrays of high aspect ratio barium titanate nanowires via hydrothermal synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bowland, Christopher C.; Zhou, Zhi; Malakooti, Mohammad H.

2015-06-01

We report on the development of a hydrothermal synthesis procedure that results in the growth of highly aligned arrays of high aspect ratio barium titanate nanowires. Using a multiple step, scalable hydrothermal reaction, a textured titanium dioxide film is deposited on titanium foil upon which highly aligned nanowires are grown via homoepitaxy and converted to barium titanate. Scanning electron microscope images clearly illustrate the effect the textured film has on the degree of orientation of the nanowires. The alignment of nanowires is quantified by calculating the Herman's Orientation Factor, which reveals a 58% improvement in orientation as compared to growthmore » in the absence of the textured film. The ferroelectric properties of barium titanate combined with the development of this scalable growth procedure provide a powerful route towards increasing the efficiency and performance of nanowire-based devices in future real-world applications such as sensing and power harvesting.« less

Surface plasmon aided high sensitive non-enzymatic glucose sensor using Au/NiAu multilayered nanowire arrays.

PubMed

Wang, Lanfang; Zhu, Weiqi; Lu, Wenbo; Qin, Xiufang; Xu, Xiaohong

2018-07-15

A novel plasmon aided non-enzymatic glucose sensor was first constructed based on the unique half-rough Au/NiAu multilayered nanowire arrays. These multilayered and half-rough nanowires provide high chemical activity and large surface area for glucose oxidation in an alkaline solution. Under visible light irradiation, the surface plasmons originated from Au part enhance the electron transfer in the vertically aligned nanowires, leading to high sensitivity and wide detection range. The resulting sensor exhibits a wide glucose detection concentration range, low detection limit, and high sensitivity for plasmon aided non-enzymatic glucose sensor. Moreover, the detection sensitivity is enhanced by almost 2 folds compared to that in the dark, which significantly enhanced the performance of Au/NiAu multilayered nanowire arrays sensor. An excellent selectivity and acceptable stability were also achieved. These results indicate that surface plasmon aided nanostructures are promising new platforms for the construction of non-enzymatic glucose sensors. Copyright © 2018 Elsevier B.V. All rights reserved.

Ultrahigh Density Array of Vertically Aligned Small-molecular Organic Nanowires on Arbitrary Substrates

PubMed Central

Starko-Bowes, Ryan; Pramanik, Sandipan

2013-01-01

In recent years π-conjugated organic semiconductors have emerged as the active material in a number of diverse applications including large-area, low-cost displays, photovoltaics, printable and flexible electronics and organic spin valves. Organics allow (a) low-cost, low-temperature processing and (b) molecular-level design of electronic, optical and spin transport characteristics. Such features are not readily available for mainstream inorganic semiconductors, which have enabled organics to carve a niche in the silicon-dominated electronics market. The first generation of organic-based devices has focused on thin film geometries, grown by physical vapor deposition or solution processing. However, it has been realized that organic nanostructures can be used to enhance performance of above-mentioned applications and significant effort has been invested in exploring methods for organic nanostructure fabrication. A particularly interesting class of organic nanostructures is the one in which vertically oriented organic nanowires, nanorods or nanotubes are organized in a well-regimented, high-density array. Such structures are highly versatile and are ideal morphological architectures for various applications such as chemical sensors, split-dipole nanoantennas, photovoltaic devices with radially heterostructured "core-shell" nanowires, and memory devices with a cross-point geometry. Such architecture is generally realized by a template-directed approach. In the past this method has been used to grow metal and inorganic semiconductor nanowire arrays. More recently π-conjugated polymer nanowires have been grown within nanoporous templates. However, these approaches have had limited success in growing nanowires of technologically important π-conjugated small molecular weight organics, such as tris-8-hydroxyquinoline aluminum (Alq3), rubrene and methanofullerenes, which are commonly used in diverse areas including organic displays, photovoltaics, thin film transistors

Ultrahigh density array of vertically aligned small-molecular organic nanowires on arbitrary substrates.

PubMed

Starko-Bowes, Ryan; Pramanik, Sandipan

2013-06-18

In recent years π-conjugated organic semiconductors have emerged as the active material in a number of diverse applications including large-area, low-cost displays, photovoltaics, printable and flexible electronics and organic spin valves. Organics allow (a) low-cost, low-temperature processing and (b) molecular-level design of electronic, optical and spin transport characteristics. Such features are not readily available for mainstream inorganic semiconductors, which have enabled organics to carve a niche in the silicon-dominated electronics market. The first generation of organic-based devices has focused on thin film geometries, grown by physical vapor deposition or solution processing. However, it has been realized that organic nanostructures can be used to enhance performance of above-mentioned applications and significant effort has been invested in exploring methods for organic nanostructure fabrication. A particularly interesting class of organic nanostructures is the one in which vertically oriented organic nanowires, nanorods or nanotubes are organized in a well-regimented, high-density array. Such structures are highly versatile and are ideal morphological architectures for various applications such as chemical sensors, split-dipole nanoantennas, photovoltaic devices with radially heterostructured "core-shell" nanowires, and memory devices with a cross-point geometry. Such architecture is generally realized by a template-directed approach. In the past this method has been used to grow metal and inorganic semiconductor nanowire arrays. More recently π-conjugated polymer nanowires have been grown within nanoporous templates. However, these approaches have had limited success in growing nanowires of technologically important π-conjugated small molecular weight organics, such as tris-8-hydroxyquinoline aluminum (Alq3), rubrene and methanofullerenes, which are commonly used in diverse areas including organic displays, photovoltaics, thin film transistors

Optimization of GaAs Nanowire Pin Junction Array Solar Cells by Using AlGaAs/GaAs Heterojunctions

NASA Astrophysics Data System (ADS)

Wu, Yao; Yan, Xin; Wei, Wei; Zhang, Jinnan; Zhang, Xia; Ren, Xiaomin

2018-04-01

We optimized the performance of GaAs nanowire pin junction array solar cells by introducing AlGaAs/GaAs heterejunctions. AlGaAs is used for the p type top segment for axial junctions and the p type outer shell for radial junctions. The AlGaAs not only serves as passivation layers for GaAs nanowires but also confines the optical generation in the active regions, reducing the recombination loss in heavily doped regions and the minority carrier recombination at the top contact. The results show that the conversion efficiency of GaAs nanowires can be greatly enhanced by using AlGaAs for the p segment instead of GaAs. A maximum efficiency enhancement of 8.42% has been achieved in this study. And for axial nanowire, by using AlGaAs for the top p segment, a relatively long top segment can be employed without degenerating device performance, which could facilitate the fabrication and contacting of nanowire array solar cells. While for radial nanowires, AlGaAs/GaAs nanowires show better tolerance to p-shell thickness and surface condition.

Optimization of GaAs Nanowire Pin Junction Array Solar Cells by Using AlGaAs/GaAs Heterojunctions.

PubMed

Wu, Yao; Yan, Xin; Wei, Wei; Zhang, Jinnan; Zhang, Xia; Ren, Xiaomin

2018-04-25

We optimized the performance of GaAs nanowire pin junction array solar cells by introducing AlGaAs/GaAs heterejunctions. AlGaAs is used for the p type top segment for axial junctions and the p type outer shell for radial junctions. The AlGaAs not only serves as passivation layers for GaAs nanowires but also confines the optical generation in the active regions, reducing the recombination loss in heavily doped regions and the minority carrier recombination at the top contact. The results show that the conversion efficiency of GaAs nanowires can be greatly enhanced by using AlGaAs for the p segment instead of GaAs. A maximum efficiency enhancement of 8.42% has been achieved in this study. And for axial nanowire, by using AlGaAs for the top p segment, a relatively long top segment can be employed without degenerating device performance, which could facilitate the fabrication and contacting of nanowire array solar cells. While for radial nanowires, AlGaAs/GaAs nanowires show better tolerance to p-shell thickness and surface condition.

Organic nanowire hierarchy over fabric platform for flexible cold cathode

NASA Astrophysics Data System (ADS)

Maiti, Soumen; Narayan Maiti, Uday; Pal, Shreyasi; Chattopadhyay, Kalyan Kumar

2013-11-01

Organic charge transfer (CT) complexes initiated a growing interest in modern electronic devices owing to their easy processability and unique characteristics. In this work, three-dimensional field emitters comprising metal-organic charge transfer complex nanostructures of AgTCNQ and CuTCNQ (TCNQ, 7,7,8,8-tetracyanoquinodimethane) over flexible fabric substrate are realized. Deliberate control over the reaction parameter during organic solid phase reaction leads to modification in structural parameters of the nanowires (i.e. length, diameter) as well as their arrangement atop the carbon fibers. The optimized arrays of AgTCNQ and CuTCNQ nanowires exhibit excellent field electron emission performance with very low turn-on (1.72 and 2.56 V μm-1) and threshold fields (4.21 and 6.33 V μm-1) respectively, which are comparable to those of the best organic field emitters reported to date. The underlying conducting carbon cloth with special woven-like geometry not only offers a flexible platform for nanowire growth, but also provides an additional field enhancement to ease the electron emission.

Electrodeposition of Rhodium Nanowires Arrays and Their Morphology-Dependent Hydrogen Evolution Activity

PubMed Central

Zhang, Liqiu; Liu, Lichun; Wang, Hongdan; Shen, Hongxia; Cheng, Qiong; Yan, Chao; Park, Sungho

2017-01-01

This work reports on the electrodeposition of rhodium (Rh) nanowires with a controlled surface morphology synthesized using an anodic aluminum oxide (AAO) template. Vertically aligned Rh nanowires with a smooth and coarse morphology were successfully deposited by adjusting the electrode potential and the concentration of precursor ions and by involving a complexing reagent in the electrolyte solution. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses were used to follow the morphological evolution of Rh nanowires. As a heterogeneous electrocatalyst for hydrogen evolution reactions (HER), the coarse Rh nanowire array exhibited an enhanced catalytic performance respect to smooth ones due to the larger surface area to mass ratio and the higher density of catalytically active defects, as evidenced by voltammetric measurements and TEM. Results suggest that the morphology of metallic nanomaterials could be readily engineered by electrodeposition. The controlled electrodeposition offers great potential for the development of an effective synthesis tool for heterogeneous catalysts with a superior performance for wide applications. PMID:28467375

FIB-tomographic studies on chemical vapor deposition grown SnO2 nanowire arrays on TiO2 (001)

NASA Astrophysics Data System (ADS)

Chen, Haoyun; Liu, Yi; Wu, Hong; Xiong, Xiang; Pan, Jun

2016-12-01

Tin oxide nanowire arrays on titania (001) have been successfully fabricated by chemical vapor deposition of Sn(O t Bu)4 precursor. The morphologies and structures of ordered SnO2 nanowires (NWs) were analyzed by cross-sectional SEM, HR-TEM and AFM. An FIB-tomography technique was applied in order to reconstruct a 3D presentation of ordered SnO2 nanowires. The achieved 3D analysis showed the spatial orientation and angles of ordered SnO2 NWs can be obtained in a one-shot experiment, and the distribution of Au catalysts showed the competition between 1D and 2D growth. The SnO2 nanowire arrays can be potentially used as a diameter- and surface-dependent sensing unit for the detection of gas- and bio-molecules.

Ordered arrays of Ni magnetic nanowires: Synthesis and investigation

NASA Astrophysics Data System (ADS)

Napolskii, K. S.; Eliseev, A. A.; Yesin, N. V.; Lukashin, A. V.; Tretyakov, Yu. D.; Grigorieva, N. A.; Grigoriev, S. V.; Eckerlebe, H.

2007-03-01

The present study is focused on the synthesis and investigation of anodic aluminum oxide (AAO) films and magnetic nanocomposites Ni/AAO obtained by Ni electrodeposition into porous matrix. AAO membranes and magnetic nanocomposites were investigated by HRSEM, EDX microanalysis, XRD, nitrogen capillary adsorption method, SQUID magnetometry, and polarized small-angle neutron scattering (SANS). The influence of synthesis conditions and form factor effect on the magnetic properties of nanowire arrays is reported.

Electrochemical properties of Ti3+ doped Ag-Ti nanotube arrays coated with hydroxyapatite

NASA Astrophysics Data System (ADS)

Zhang, Hangzhou; Shi, Xiaoguo; Tian, Ang; Wang, Li; Liu, Chuangwei

2018-04-01

Ag-Ti nanotube array was prepared by simple anodic oxidation method and uniform hydroxyapatite were electrochemically deposited on the nanotubes, and then characterized by SEM, XRD, XPS and EIS. In order to investigate the influence of Ti3+ on the electrochemical deposition of hydroxyapatite on the nanotubes, the Ag-Ti nanotube array self-doped with Ti3+ was prepared by one step reduction method. The experiment results revealed that the Ti3+ can promote the grow rate of hydroxyapatite coatings on nanotube surface. The hydroxyapatite coated Ag-Ti nanotube arrays with Ti3+ exhibit excellent stability and higher corrosion resistance. Moreover, the compact and dense hydroxyapatite coating can also prevent the Ag atom erosion from the Ag-Ti nanotube.

Optical analysis of a III-V-nanowire-array-on-Si dual junction solar cell.

PubMed

Chen, Yang; Höhn, Oliver; Tucher, Nico; Pistol, Mats-Erik; Anttu, Nicklas

2017-08-07

A tandem solar cell consisting of a III-V nanowire subcell on top of a planar Si subcell is a promising candidate for next generation photovoltaics due to the potential for high efficiency. However, for success with such applications, the geometry of the system must be optimized for absorption of sunlight. Here, we consider this absorption through optics modeling. Similarly, as for a bulk dual-junction tandem system on a silicon bottom cell, a bandgap of approximately 1.7 eV is optimum for the nanowire top cell. First, we consider a simplified system of bare, uncoated III-V nanowires on the silicon substrate and optimize the absorption in the nanowires. We find that an optimum absorption in 2000 nm long nanowires is reached for a dense array of approximately 15 nanowires per square micrometer. However, when we coat such an array with a conformal indium tin oxide (ITO) top contact layer, a substantial absorption loss occurs in the ITO. This ITO could absorb 37% of the low energy photons intended for the silicon subcell. By moving to a design with a 50 nm thick, planarized ITO top layer, we can reduce this ITO absorption to 5%. However, such a planarized design introduces additional reflection losses. We show that these reflection losses can be reduced with a 100 nm thick SiO 2 anti-reflection coating on top of the ITO layer. When we at the same time include a Si 3 N 4 layer with a thickness of 90 nm on the silicon surface between the nanowires, we can reduce the average reflection loss of the silicon cell from 17% to 4%. Finally, we show that different approximate models for the absorption in the silicon substrate can lead to a 15% variation in the estimated photocurrent density in the silicon subcell.

Vertically p-n-junctioned GaN nano-wire array diode fabricated on Si(111) using MOCVD.

PubMed

Park, Ji-Hyeon; Kim, Min-Hee; Kissinger, Suthan; Lee, Cheul-Ro

2013-04-07

We demonstrate the fabrication of n-GaN:Si/p-GaN:Mg nanowire arrays on (111) silicon substrate by metal organic chemical vapor deposition (MOCVD) method .The nanowires were grown by a newly developed two-step growth process. The diameter of as-grown nanowires ranges from 300-400 nm with a density of 6-7 × 10(7) cm(-2). The p- and n-type doping of the nanowires is achieved with Mg and Si dopant species. Structural characterization by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) indicates that the nanowires are relatively defect-free. The room-temperature photoluminescence emission with a strong peak at 370 nm indicates that the n-GaN:Si/p-GaN:Mg nanowire arrays have potential application in light-emitting nanodevices. The cathodoluminscence (CL) spectrum clearly shows a distinct optical transition of GaN nanodiodes. The nano-n-GaN:Si/p-GaN:Mg diodes were further completed using a sputter coating approach to deposit Au/Ni metal contacts. The polysilazane filler has been etched by a wet chemical etching process. The n-GaN:Si/p-GaN:Mg nanowire diode was fabricated for different Mg source flow rates. The current-voltage (I-V) measurements reveal excellent rectifying properties with an obvious turn-on voltage at 1.6 V for a Mg flow rate of 5 sccm (standard cubic centimeters per minute).

Vertically p-n-junctioned GaN nano-wire array diode fabricated on Si(111) using MOCVD

NASA Astrophysics Data System (ADS)

Park, Ji-Hyeon; Kim, Min-Hee; Kissinger, Suthan; Lee, Cheul-Ro

2013-03-01

We demonstrate the fabrication of n-GaN:Si/p-GaN:Mg nanowire arrays on (111) silicon substrate by metal organic chemical vapor deposition (MOCVD) method .The nanowires were grown by a newly developed two-step growth process. The diameter of as-grown nanowires ranges from 300-400 nm with a density of 6-7 × 107 cm-2. The p- and n-type doping of the nanowires is achieved with Mg and Si dopant species. Structural characterization by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) indicates that the nanowires are relatively defect-free. The room-temperature photoluminescence emission with a strong peak at 370 nm indicates that the n-GaN:Si/p-GaN:Mg nanowire arrays have potential application in light-emitting nanodevices. The cathodoluminscence (CL) spectrum clearly shows a distinct optical transition of GaN nanodiodes. The nano-n-GaN:Si/p-GaN:Mg diodes were further completed using a sputter coating approach to deposit Au/Ni metal contacts. The polysilazane filler has been etched by a wet chemical etching process. The n-GaN:Si/p-GaN:Mg nanowire diode was fabricated for different Mg source flow rates. The current-voltage (I-V) measurements reveal excellent rectifying properties with an obvious turn-on voltage at 1.6 V for a Mg flow rate of 5 sccm (standard cubic centimeters per minute).

A top-down approach to fabrication of high quality vertical heterostructure nanowire arrays.

PubMed

Wang, Hua; Sun, Minghua; Ding, Kang; Hill, Martin T; Ning, Cun-Zheng

2011-04-13

We demonstrate a novel top-down approach for fabricating nanowires with unprecedented complexity and optical quality by taking advantage of a nanoscale self-masking effect. We realized vertical arrays of nanowires of 20-40 nm in diameter with 16 segments of complex longitudinal InGaAsP/InP structures. The unprecedented high quality of etched wires is evidenced by the narrowest photoluminescence linewidth ever produced in similar wavelengths, indistinguishable from that of the corresponding wafer. This top-down, mask-free, large scale approach is compatible with the established device fabrication processes and could serve as an important alternative to the bottom-up approach, significantly expanding ranges and varieties of applications of nanowire technology.

Energy Penetration into Arrays of Aligned Nanowires Irradiated with Relativistic Intensities: Scaling to Terabar Pressures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bargsten, Clayton; Hollinger, Reed; Capeluto, Maria Gabriela

Ultra-high-energy-density (UHED) matter, characterized by energy densities > 1 x 10 8 J cm -3 and pressures greater than a gigabar, is encountered in the center of stars and in inertial confinement fusion capsules driven by the world’s largest lasers. Similar conditions can be obtained with compact, ultra-high contrast, femtosecond lasers focused to relativistic intensities onto targets composed of aligned nanowire arrays. Here we report the measurement of the key physical process in determining the energy density deposited in high aspect ratio nanowire array plasmas: the energy penetration. By monitoring the x-ray emission from buried Co tracer segments in Nimore » nanowire arrays irradiated at an intensity of 4 x 10 19 W cm -2, we demonstrate energy penetration depths of several μm, leading to UHED plasmas of that size. Relativistic 3D particle-in-cell-simulations, validated by these measurements, predict that irradiation of nanostructures at intensities of > 1 x 10 22 W cm -2 will lead to a virtually unexplored extreme UHED plasma regime characterized by energy densities in excess of 8 x 10 10 J cm -3, equivalent to a pressure of 0.35 Tbar.« less

Plasma nitriding induced growth of Pt-nanowire arrays as high performance electrocatalysts for fuel cells

NASA Astrophysics Data System (ADS)

Du, Shangfeng; Lin, Kaijie; Malladi, Sairam K.; Lu, Yaxiang; Sun, Shuhui; Xu, Qiang; Steinberger-Wilckens, Robert; Dong, Hanshan

2014-09-01

In this work, we demonstrate an innovative approach, combing a novel active screen plasma (ASP) technique with green chemical synthesis, for a direct fabrication of uniform Pt nanowire arrays on large-area supports. The ASP treatment enables in-situ N-doping and surface modification to the support surface, significantly promoting the uniform growth of tiny Pt nuclei which directs the growth of ultrathin single-crystal Pt nanowire (2.5-3 nm in diameter) arrays, forming a three-dimensional (3D) nano-architecture. Pt nanowire arrays in-situ grown on the large-area gas diffusion layer (GDL) (5 cm2) can be directly used as the catalyst electrode in fuel cells. The unique design brings in an extremely thin electrocatalyst layer, facilitating the charge transfer and mass transfer properties, leading to over two times higher power density than the conventional Pt nanoparticle catalyst electrode in real fuel cell environment. Due to the similar challenges faced with other nanostructures and the high availability of ASP for other material surfaces, this work will provide valuable insights and guidance towards the development of other new nano-architectures for various practical applications.

Energy penetration into arrays of aligned nanowires irradiated with relativistic intensities: Scaling to terabar pressures.

PubMed

Bargsten, Clayton; Hollinger, Reed; Capeluto, Maria Gabriela; Kaymak, Vural; Pukhov, Alexander; Wang, Shoujun; Rockwood, Alex; Wang, Yong; Keiss, David; Tommasini, Riccardo; London, Richard; Park, Jaebum; Busquet, Michel; Klapisch, Marcel; Shlyaptsev, Vyacheslav N; Rocca, Jorge J

2017-01-01

Ultrahigh-energy density (UHED) matter, characterized by energy densities >1 × 10 8 J cm -3 and pressures greater than a gigabar, is encountered in the center of stars and inertial confinement fusion capsules driven by the world's largest lasers. Similar conditions can be obtained with compact, ultrahigh contrast, femtosecond lasers focused to relativistic intensities onto targets composed of aligned nanowire arrays. We report the measurement of the key physical process in determining the energy density deposited in high-aspect-ratio nanowire array plasmas: the energy penetration. By monitoring the x-ray emission from buried Co tracer segments in Ni nanowire arrays irradiated at an intensity of 4 × 10 19 W cm -2 , we demonstrate energy penetration depths of several micrometers, leading to UHED plasmas of that size. Relativistic three-dimensional particle-in-cell simulations, validated by these measurements, predict that irradiation of nanostructures at intensities of >1 × 10 22 W cm -2 will lead to a virtually unexplored extreme UHED plasma regime characterized by energy densities in excess of 8 × 10 10 J cm -3 , equivalent to a pressure of 0.35 Tbar.

Energy penetration into arrays of aligned nanowires irradiated with relativistic intensities: Scaling to terabar pressures

PubMed Central

Bargsten, Clayton; Hollinger, Reed; Capeluto, Maria Gabriela; Kaymak, Vural; Pukhov, Alexander; Wang, Shoujun; Rockwood, Alex; Wang, Yong; Keiss, David; Tommasini, Riccardo; London, Richard; Park, Jaebum; Busquet, Michel; Klapisch, Marcel; Shlyaptsev, Vyacheslav N.; Rocca, Jorge J.

2017-01-01

Ultrahigh-energy density (UHED) matter, characterized by energy densities >1 × 108 J cm−3 and pressures greater than a gigabar, is encountered in the center of stars and inertial confinement fusion capsules driven by the world’s largest lasers. Similar conditions can be obtained with compact, ultrahigh contrast, femtosecond lasers focused to relativistic intensities onto targets composed of aligned nanowire arrays. We report the measurement of the key physical process in determining the energy density deposited in high-aspect-ratio nanowire array plasmas: the energy penetration. By monitoring the x-ray emission from buried Co tracer segments in Ni nanowire arrays irradiated at an intensity of 4 × 1019 W cm−2, we demonstrate energy penetration depths of several micrometers, leading to UHED plasmas of that size. Relativistic three-dimensional particle-in-cell simulations, validated by these measurements, predict that irradiation of nanostructures at intensities of >1 × 1022 W cm−2 will lead to a virtually unexplored extreme UHED plasma regime characterized by energy densities in excess of 8 × 1010 J cm−3, equivalent to a pressure of 0.35 Tbar. PMID:28097218

Photoelectrochemical Water Oxidation by GaAs Nanowire Arrays Protected with Atomic Layer Deposited NiO x Electrocatalysts

NASA Astrophysics Data System (ADS)

Zeng, Joy; Xu, Xiaoqing; Parameshwaran, Vijay; Baker, Jon; Bent, Stacey; Wong, H.-S. Philip; Clemens, Bruce

2018-02-01

Photoelectrochemical (PEC) hydrogen production makes possible the direct conversion of solar energy into chemical fuel. In this work, PEC photoanodes consisting of GaAs nanowire (NW) arrays were fabricated, characterized, and then demonstrated for the oxygen evolution reaction (OER). Uniform and periodic GaAs nanowire arrays were grown on a heavily n-doped GaAs substrates by metal-organic chemical vapor deposition selective area growth. The nanowire arrays were characterized using cyclic voltammetry and impedance spectroscopy in a non-aqueous electrochemical system using ferrocene/ferrocenium (Fc/Fc+) as a redox couple, and a maximum oxidation photocurrent of 11.1 mA/cm2 was measured. GaAs NW arrays with a 36 nm layer of nickel oxide (NiO x ) synthesized by atomic layer deposition were then used as photoanodes to drive the OER. In addition to acting as an electrocatalyst, the NiO x layer served to protect the GaAs NWs from oxidative corrosion. Using this strategy, GaAs NW photoanodes were successfully used for the oxygen evolution reaction. This is the first demonstration of GaAs NW arrays for effective OER, and the fabrication and protection strategy developed in this work can be extended to study any other nanostructured semiconductor materials systems for electrochemical solar energy conversion.

Scalable Top-Down Approach Tailored by Interferometric Lithography to Achieve Large-Area Single-Mode GaN Nanowire Laser Arrays on Sapphire Substrate.

PubMed

Behzadirad, Mahmoud; Nami, Mohsen; Wostbrock, Neal; Zamani Kouhpanji, Mohammad Reza; Feezell, Daniel F; Brueck, Steven R J; Busani, Tito

2018-03-27

GaN nanowires are promising for optical and optoelectronic applications because of their waveguiding properties and large optical band gap. However, developing a precise, scalable, and cost-effective fabrication method with a high degree of controllability to obtain high-aspect-ratio nanowires with high optical properties and minimum crystal defects remains a challenge. Here, we present a scalable two-step top-down approach using interferometric lithography, for which parameters can be controlled precisely to achieve highly ordered arrays of nanowires with excellent quality and desired aspect ratios. The wet-etch mechanism is investigated, and the etch rates of m-planes {11̅00} (sidewalls) were measured to be 2.5 to 70 nm/h depending on the Si doping concentration. Using this method, uniform nanowire arrays were achieved over a large area (>10 5 μm 2 ) with an spect ratio as large as 50, a radius as small as 17 nm, and atomic-scale sidewall roughness (<1 nm). FDTD modeling demonstrated HE 11 is the dominant transverse mode in the nanowires with a radius of sub-100 nm, and single-mode lasing from vertical cavity nanowire arrays with different doping concentrations on a sapphire substrate was interestingly observed in photoluminescence measurements. High Q-factors of ∼1139-2443 were obtained in nanowire array lasers with a radius and length of 65 nm and 2 μm, respectively, corresponding to a line width of 0.32-0.15 nm (minimum threshold of 3.31 MW/cm 2 ). Our results show that fabrication of high-quality GaN nanowire arrays with adaptable aspect ratio and large-area uniformity is feasible through a top-down approach using interferometric lithography and is promising for fabrication of III-nitride-based nanophotonic devices (radial/axial) on the original substrate.

Rapid Synthesis of Thin and Long Mo17O47 Nanowire-Arrays in an Oxygen Deficient Flame

PubMed Central

Allen, Patrick; Cai, Lili; Zhou, Lite; Zhao, Chenqi; Rao, Pratap M.

2016-01-01

Mo17O47 nanowire-arrays are promising active materials and electrically-conductive supports for batteries and other devices. While high surface area resulting from long, thin, densely packed nanowires generally leads to improved performance in a wide variety of applications, the Mo17O47 nanowire-arrays synthesized previously by electrically-heated chemical vapor deposition under vacuum conditions were relatively thick and short. Here, we demonstrate a method to grow significantly thinner and longer, densely packed, high-purity Mo17O47 nanowire-arrays with diameters of 20–60 nm and lengths of 4–6 μm on metal foil substrates using rapid atmospheric flame vapor deposition without any chamber or walls. The atmospheric pressure and 1000 °C evaporation temperature resulted in smaller diameters, longer lengths and order-of-magnitude faster growth rate than previously demonstrated. As explained by kinetic and thermodynamic calculations, the selective synthesis of high-purity Mo17O47 nanowires is achieved due to low oxygen partial pressure in the flame products as a result of the high ratio of fuel to oxidizer supplied to the flame, which enables the correct ratio of MoO2 and MoO3 vapor concentrations for the growth of Mo17O47. This flame synthesis method is therefore a promising route for the growth of composition-controlled one-dimensional metal oxide nanomaterials for many applications. PMID:27271194

Hierarchical Mesoporous Zinc-Nickel-Cobalt Ternary Oxide Nanowire Arrays on Nickel Foam as High-Performance Electrodes for Supercapacitors.

PubMed

Wu, Chun; Cai, Junjie; Zhang, Qiaobao; Zhou, Xiang; Zhu, Ying; Shen, Pei Kang; Zhang, Kaili

2015-12-09

Nickel foam supported hierarchical mesoporous Zn-Ni-Co ternary oxide (ZNCO) nanowire arrays are synthesized by a simple two-step approach including a hydrothermal method and subsequent calcination process and directly utilized for supercapacitive investigation for the first time. The nickel foam supported hierarchical mesoporous ZNCO nanowire arrays possess an ultrahigh specific capacitance value of 2481.8 F g(-1) at 1 A g(-1) and excellent rate capability of about 91.9% capacitance retention at 5 A g(-1). More importantly, an asymmetric supercapacitor with a high energy density (35.6 Wh kg(-1)) and remarkable cycle stability performance (94% capacitance retention over 3000 cycles) is assembled successfully by employing the ZNCO electrode as positive electrode and activated carbon as negative electrode. The remarkable electrochemical behaviors demonstrate that the nickel foam supported hierarchical mesoporous ZNCO nanowire array electrodes are highly desirable for application as advanced supercapacitor electrodes.

Enhanced Performance of Photoelectrochemical Water Splitting with ITO@α-Fe2O3 Core-Shell Nanowire Array as Photoanode.

PubMed

Yang, Jie; Bao, Chunxiong; Yu, Tao; Hu, Yingfei; Luo, Wenjun; Zhu, Weidong; Fu, Gao; Li, Zhaosheng; Gao, Hao; Li, Faming; Zou, Zhigang

2015-12-09

Hematite (α-Fe2O3) is one of the most promising candidates for photoelectrodes in photoelectrochemical water splitting system. However, the low visible light absorption coefficient and short hole diffusion length of pure α-Fe2O3 limits the performance of α-Fe2O3 photoelectrodes in water splitting. Herein, to overcome these drawbacks, single-crystalline tin-doped indium oxide (ITO) nanowire core and α-Fe2O3 nanocrystal shell (ITO@α-Fe2O3) electrodes were fabricated by covering the chemical vapor deposited ITO nanowire array with compact thin α-Fe2O3 nanocrystal film using chemical bath deposition (CBD) method. The J-V curves and IPCE of ITO@α-Fe2O3 core-shell nanowire array electrode showed nearly twice as high performance as those of the α-Fe2O3 on planar Pt-coated silicon wafers (Pt/Si) and on planar ITO substrates, which was considered to be attributed to more efficient hole collection and more loading of α-Fe2O3 nanocrystals in the core-shell structure than planar structure. Electrochemical impedance spectra (EIS) characterization demonstrated a low interface resistance between α-Fe2O3 and ITO nanowire arrays, which benefits from the well contact between the core and shell. The stability test indicated that the prepared ITO@α-Fe2O3 core-shell nanowire array electrode was stable under AM1.5 illumination during the test period of 40,000 s.

Switching behaviour of individual Ag-TCNQ nanowires: an in situ transmission electron microscopy study

NASA Astrophysics Data System (ADS)

Ran, Ke; Rösner, Benedikt; Butz, Benjamin; Fink, Rainer H.; Spiecker, Erdmann

2016-10-01

The organic semiconductor silver-tetracyanoquinodimethane (Ag-TCNQ) exhibits electrical switching and memory characteristics. Employing a scanning tunnelling microscopy setup inside a transmission electron microscope, the switching behaviour of individual Ag-TCNQ nanowires (NWs) is investigated in detail. For a large number of NWs, the switching between a high (OFF) and a low (ON) resistance state was successfully stimulated by negative bias sweeps. Fitting the experimental I-V curves with a Schottky emission function makes the switching features prominent and thus enables a direct evaluation of the switching process. A memory cycle including writing, reading and erasing features is demonstrated at an individual NW. Moreover, electronic failure mechanisms due to Joule heating are discussed. These findings have a significant impact on our understanding of the switching behaviour of Ag-TCNQ.

Polyaniline nanowire array encapsulated in titania nanotubes as a superior electrode for supercapacitors

NASA Astrophysics Data System (ADS)

Xie, Keyu; Li, Jie; Lai, Yanqing; Zhang, Zhi'an; Liu, Yexiang; Zhang, Guoge; Huang, Haitao

2011-05-01

Conducting polymer with 1D nanostructure exhibits excellent electrochemical performances but a poor cyclability that limits its use in supercapacitors. In this work, a novel composite electrode made of polyaniline nanowire-titania nanotube array was synthesized via a simple and inexpensive electrochemical route by electropolymerizing aniline onto an anodized titania nanotube array. The specific capacitance was as high as 732 F g-1 at 1 A g-1, which remained at 543 F g-1 when the current density was increased by 20 times. 74% of the maximum energy density (36.6 Wh kg-1) was maintained even at a high power density of 6000 W kg-1. An excellent long cycle life of the electrode was observed with a retention of ~86% of the initial specific capacitance after 2000 cycles. The good electrochemical performance was attributed to the unique microstructure of the electrode with disordered PANI nanowire arrays encapsulated inside the TiO2 nanotubes, providing high surface area, fast diffusion path for ions and long-term cycle stability. Such a nanocomposite electrode is attractive for supercapacitor applications.

Ambient-Stable and Durable Conductive Ag-Nanowire-Network 2-D Films Decorated with a Ti Layer.

PubMed

Kim, Yoon-Mi; Hwang, Bu-Yeon; Lee, Ki-Wook; Kim, Jin-Yeol

2018-05-11

Highly stable and durable conductive silver nanowire (Ag NW) network electrode films were prepared through decoration with a 5-nm-thick Ti layer. The Ag NW network 2-D films showed sheet resistance values as low as 32 ohm/sq at 88% transparency when decorated with Ti. These 2-D films exhibited a 30% increase in electrical conductivity while maintaining good stability of the films through enhanced resistance to moisture and oxygen penetration as a result of the protective effect of the Ti layer.

Enhancing absorption in coated semiconductor nanowire/nanorod core-shell arrays using active host matrices

NASA Astrophysics Data System (ADS)

Jule, Leta; Dejene, Francis; Roro, Kittessa

2016-12-01

In the present work, we investigated theoretically and experimentally the interaction of radiation field phenomena interacting with arrays of nanowire/nanorod core-shell embedded in active host matrices. The optical properties of composites are explored including the case when the absorption of propagating wave by dissipative component is completely compensated by amplification in active (lasing) medium. On the basis of more elaborated modeling approach and extended effective medium theory, the effective polarizability and the refractive index of electromagnetic mode dispersion of the core-shell nanowire arrays are derived. ZnS(shell)-coated by sulphidation process on ZnO(shell) nanorod arrays grown on (100) silicon substrate by chemical bath deposition (CBD) has been used for theoretical comparison. Compared with the bare ZnO nanorods, ZnS-coated core/shell nanorods exhibit a strongly reduced ultraviolet (UV) emission and a dramatically enhanced deep level (DL) emission. Obviously, the UV and DL emission peaks are attributed to the emissions of ZnO nanorods within ZnO/ZnS core/shell nanorods. The reduction of UV emission after ZnS coating seems to agree with the charge separation mechanism of type-II band alignment that holes transfer from the core to shell, which would quench the UV emission to a certain extent. Our theoretical calculations and numerical simulation demonstrate that the use of active host (amplifying) medium to compensate absorption at metallic inclusions. Moreover the core-shell nanorod/nanowire arrays create the opportunity for broad band absorption and light harvesting applications.

Energy penetration into arrays of aligned nanowires irradiated with relativistic intensities: Scaling to terabar pressures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bargsten, Clayton; Hollinger, Reed; Capeluto, Maria Gabriela

Ultrahigh-energy density (UHED) matter, characterized by energy densities >1 × 10 8 J cm –3 and pressures greater than a gigabar, is encountered in the center of stars and inertial confinement fusion capsules driven by the world’s largest lasers. Similar conditions can be obtained with compact, ultrahigh contrast, femtosecond lasers focused to relativistic intensities onto targets composed of aligned nanowire arrays. We report the measurement of the key physical process in determining the energy density deposited in high-aspect-ratio nanowire array plasmas: the energy penetration. By monitoring the x-ray emission from buried Co tracer segments in Ni nanowire arrays irradiated atmore » an intensity of 4 × 10 19 W cm –2, we demonstrate energy penetration depths of several micrometers, leading to UHED plasmas of that size. As a result, relativistic three-dimensional particle-in-cell simulations, validated by these measurements, predict that irradiation of nanostructures at intensities of >1 × 10 22 W cm –2 will lead to a virtually unexplored extreme UHED plasma regime characterized by energy densities in excess of 8 × 10 10 J cm –3, equivalent to a pressure of 0.35 Tbar.« less

Energy penetration into arrays of aligned nanowires irradiated with relativistic intensities: Scaling to terabar pressures

DOE PAGES

Bargsten, Clayton; Hollinger, Reed; Capeluto, Maria Gabriela; ...

2017-01-11

Ultrahigh-energy density (UHED) matter, characterized by energy densities >1 × 10 8 J cm –3 and pressures greater than a gigabar, is encountered in the center of stars and inertial confinement fusion capsules driven by the world’s largest lasers. Similar conditions can be obtained with compact, ultrahigh contrast, femtosecond lasers focused to relativistic intensities onto targets composed of aligned nanowire arrays. We report the measurement of the key physical process in determining the energy density deposited in high-aspect-ratio nanowire array plasmas: the energy penetration. By monitoring the x-ray emission from buried Co tracer segments in Ni nanowire arrays irradiated atmore » an intensity of 4 × 10 19 W cm –2, we demonstrate energy penetration depths of several micrometers, leading to UHED plasmas of that size. As a result, relativistic three-dimensional particle-in-cell simulations, validated by these measurements, predict that irradiation of nanostructures at intensities of >1 × 10 22 W cm –2 will lead to a virtually unexplored extreme UHED plasma regime characterized by energy densities in excess of 8 × 10 10 J cm –3, equivalent to a pressure of 0.35 Tbar.« less

Energy Density in Aligned Nanowire Arrays Irradiated with Relativistic Intensities: Path to Terabar Pressure Plasmas

NASA Astrophysics Data System (ADS)

Rocca, J.; Bargsten, C.; Hollinger, R.; Shylaptsev, V.; Wang, S.; Rockwood, A.; Wang, Y.; Keiss, D.; Capeluto, M.; Kaymak, V.; Pukhov, A.; Tommasini, R.; London, R.; Park, J.

2016-10-01

Ultra-high-energy-density (UHED) plasmas, characterized by energy densities >1 x 108 J cm-3 and pressures greater than a gigabar are encountered in the center of stars and in inertial confinement fusion capsules driven by the world's largest lasers. Similar conditions can be obtained with compact, ultra-high contrast, femtosecond lasers focused to relativistic intensities onto aligned nanowire array targets. Here we report the measurement of the key physical process in determining the energy density deposited in high aspect ratio nanowire array plasmas: the energy penetration. By monitoring the x-ray emission from buried Co tracer segments in Ni nanowire arrays irradiated at an intensity of 4 x 1019 W cm-2, we demonstrate energy penetration depths of several μm, leading to UHED plasmas of that size. Relativistic 3D particle-in-cell-simulations validated by these measurements predict that irradiation of nanostructures at increased intensity will lead to a virtually unexplored extreme UHED plasma regime characterized by energy densities in excess of 8 x 1010 J cm-3, equivalent to a pressure of 0.35 Tbar. This work was supported by the Fusion Energy Program, Office of Science of the U.S Department of Energy, and by the Defense Threat Reduction Agency.

A Novel Bimetallic NiMo Carbide Nanowire Array for Efficient Hydrogen Evolution.

PubMed

Guo, Lixia; Wang, Jianying; Teng, Xue; Liu, Yangyang; He, Xiaoming; Chen, Zuofeng

2018-06-12

Design and fabrication of noble metal-free hydrogen evolution electrocatalysts with high activity is significant to future renewable energy systems. In this work, self-supported NiMo carbide nanowires have been developed on carbon cloth (Ni3Mo3C@NPC NWs/CC; NPC is N,P-doped carbon) through an electropolymerization-assisted procedure. During the synthesis process, NiMoO4 nanowires were first grown on CC through a hydrothermal reaction which is free of any polymer binder like Nafion. The as-prepared NiMoO4 NWs/CC was then coated by a layer of polypyrole (PPy) by electropolymerization that serves as carbon source for the subsequent conversion to Ni3Mo3C@NPC NWs/CC by carbothermal reduction. The experimental results indicate that the judicious choices of the amount of coated PPy and the pyrolysis temperature are essential for obtaining pure phase and nanowire array structure of Ni3Mo3C@NPC NWs/CC. Benefitting from the pure phase of bimetallic carbide, the unique architecture of nanowire array and the self-supported merit, the optimized Ni3Mo3C@NPC NWs/CC electrode exhibits excellent HER performance in both acidic and alkaline media. It requires low overpotentials of 161 mV and 215 mV to afford a high current density of 100 mA cm-2 toward the HER in acidic and alkaline media, respectively, and the catalytic activity is maintained for at least 48 h, which makes it among the best HER electrocatalysts based on metallic carbides yet reported. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In situ fabrication of Ni-Co (oxy)hydroxide nanowire-supported nanoflake arrays and their application in supercapacitors.

PubMed

Zheng, Xiaoyu; Quan, Honglin; Li, Xiaoxin; He, Hai; Ye, Qinglan; Xu, Xuetang; Wang, Fan

2016-09-29

Three-dimensional (3D) hybrid nanostructured arrays grown on a flexible substrate have recently attracted great attention owing to their potential application as supercapacitor electrodes in portable and wearable electronic devices. Here, we report an in situ conversion of Ni-Co active electrode materials for the fabrication of high-performance electrodes. Ni-Co carbonate hydroxide nanowire arrays on carbon cloth were initially synthesized via a hydrothermal method, and they were gradually converted to Ni-Co (oxy)hydroxide nanowire-supported nanoflake arrays after soaking in an alkaline solution. The evolution of the supercapacitor performance of the soaked electrode was investigated in detail. The areal capacitance increases from 281 mF cm -2 at 1 mA cm -2 to 3710 and 3900 mF cm -2 after soaking for 36 h and 48 h, respectively. More interestingly, the electrode also shows an increased capacitance with charge/discharge cycles due to the long-time soaking in KOH solution, suggesting novel cycling durability. The enhancement in capacitive performance should be related to the formation of a unique nanowire-supported nanoflake array architecture, which controls the agglomeration of nanoflakes, making them fully activated. As a result, the facile in situ fabrication of the hybrid architectural design in this study provides a new approach to fabricate high-performance Ni/Co based hydroxide nanostructure arrays for next-generation energy storage devices.

Controllable fabrication of ultrafine oblique organic nanowire arrays and their application in energy harvesting

NASA Astrophysics Data System (ADS)

Zhang, Lu; Cheng, Li; Bai, Suo; Su, Chen; Chen, Xiaobo; Qin, Yong

2015-01-01

Ultrafine organic nanowire arrays (ONWAs) with a controlled direction were successfully fabricated by a novel one-step Faraday cage assisted plasma etching method. The mechanism of formation of nanowire arrays is proposed; the obliquity and aspect ratio can be accurately controlled from approximately 0° to 90° via adjusting the angle of the sample and the etching time, respectively. In addition, the ONWAs were further utilized to improve the output of the triboelectric nanogenerator (TENG). Compared with the output of TENG composed of vertical ONWAs, the open-circuit voltage, short-circuit current and inductive charges were improved by 73%, 150% and 98%, respectively. This research provides a convenient and practical method to fabricate ONWAs with various obliquities on different materials, which can be used for energy harvesting.

Controllable fabrication of ultrafine oblique organic nanowire arrays and their application in energy harvesting.

PubMed

Zhang, Lu; Cheng, Li; Bai, Suo; Su, Chen; Chen, Xiaobo; Qin, Yong

2015-01-28

Ultrafine organic nanowire arrays (ONWAs) with a controlled direction were successfully fabricated by a novel one-step Faraday cage assisted plasma etching method. The mechanism of formation of nanowire arrays is proposed; the obliquity and aspect ratio can be accurately controlled from approximately 0° to 90° via adjusting the angle of the sample and the etching time, respectively. In addition, the ONWAs were further utilized to improve the output of the triboelectric nanogenerator (TENG). Compared with the output of TENG composed of vertical ONWAs, the open-circuit voltage, short-circuit current and inductive charges were improved by 73%, 150% and 98%, respectively. This research provides a convenient and practical method to fabricate ONWAs with various obliquities on different materials, which can be used for energy harvesting.

CdS-Nanowires Flexible Photo-detector with Ag-Nanowires Electrode Based on Non-transfer Process

PubMed Central

Pei, Yanli; Pei, Ruihan; Liang, Xiaoci; Wang, Yuhao; Liu, Ling; Chen, Haibiao; Liang, Jun

2016-01-01

In this study, UV-visible flexible resistivity-type photo-detectors were demonstrated with CdS-nanowires (NWs) percolation network channel and Ag-NWs percolation network electrode. The devices were fabricated on Mixed Cellulose Esters (MCE) membrane using a lithographic filtration method combined with a facile non-transfer process. The photo-detectors demonstrated strong adhesion, fast response time, fast decay time, and high photo sensitivity. The high performance could be attributed to the high quality single crystalline CdS-NWs, encapsulation of NWs in MCE matrix and excellent interconnection of the NWs. Furthermore, the sensing performance was maintained even the device was bent at an angle of 90°. This research may pave the way for the facile fabrication of flexible photo-detectors with high performances. PMID:26899726

Ultrasmooth, extremely deformable and shape recoverable Ag nanowire embedded transparent electrode

PubMed Central

Nam, Sanggil; Song, Myungkwan; Kim, Dong-Ho; Cho, Byungjin; Lee, Hye Moon; Kwon, Jung-Dae; Park, Sung-Gyu; Nam, Kee-Seok; Jeong, Yongsoo; Kwon, Se-Hun; Park, Yun Chang; Jin, Sung-Ho; Kang, Jae-Wook; Jo, Sungjin; Kim, Chang Su

2014-01-01

Transparent electrodes have been widely used in electronic devices such as solar cells, displays, and touch screens. Highly flexible transparent electrodes are especially desired for the development of next generation flexible electronic devices. Although indium tin oxide (ITO) is the most commonly used material for the fabrication of transparent electrodes, its brittleness and growing cost limit its utility for flexible electronic devices. Therefore, the need for new transparent conductive materials with superior mechanical properties is clear and urgent. Ag nanowire (AgNW) has been attracting increasing attention because of its effective combination of electrical and optical properties. However, it still suffers from several drawbacks, including large surface roughness, instability against oxidation and moisture, and poor adhesion to substrates. These issues need to be addressed before wide spread use of metallic NW as transparent electrodes can be realized. In this study, we demonstrated the fabrication of a flexible transparent electrode with superior mechanical, electrical and optical properties by embedding a AgNW film into a transparent polymer matrix. This technique can produce electrodes with an ultrasmooth and extremely deformable transparent electrode that have sheet resistance and transmittance comparable to those of an ITO electrode. PMID:24763248

Ultrasmooth, extremely deformable and shape recoverable Ag nanowire embedded transparent electrode.

PubMed

Nam, Sanggil; Song, Myungkwan; Kim, Dong-Ho; Cho, Byungjin; Lee, Hye Moon; Kwon, Jung-Dae; Park, Sung-Gyu; Nam, Kee-Seok; Jeong, Yongsoo; Kwon, Se-Hun; Park, Yun Chang; Jin, Sung-Ho; Kang, Jae-Wook; Jo, Sungjin; Kim, Chang Su

2014-04-25

Transparent electrodes have been widely used in electronic devices such as solar cells, displays, and touch screens. Highly flexible transparent electrodes are especially desired for the development of next generation flexible electronic devices. Although indium tin oxide (ITO) is the most commonly used material for the fabrication of transparent electrodes, its brittleness and growing cost limit its utility for flexible electronic devices. Therefore, the need for new transparent conductive materials with superior mechanical properties is clear and urgent. Ag nanowire (AgNW) has been attracting increasing attention because of its effective combination of electrical and optical properties. However, it still suffers from several drawbacks, including large surface roughness, instability against oxidation and moisture, and poor adhesion to substrates. These issues need to be addressed before wide spread use of metallic NW as transparent electrodes can be realized. In this study, we demonstrated the fabrication of a flexible transparent electrode with superior mechanical, electrical and optical properties by embedding a AgNW film into a transparent polymer matrix. This technique can produce electrodes with an ultrasmooth and extremely deformable transparent electrode that have sheet resistance and transmittance comparable to those of an ITO electrode.

Optoelectrical modeling of solar cells based on c-Si/a-Si:H nanowire array: focus on the electrical transport in between the nanowires.

PubMed

Levtchenko, Alexandra; Le Gall, Sylvain; Lachaume, Raphaël; Michallon, Jérôme; Collin, Stéphane; Alvarez, José; Djebbour, Zakaria; Kleider, Jean-Paul

2018-06-22

By coupling optical and electrical modeling, we have investigated the photovoltaic performances of p-i-n radial nanowires array based on crystalline p-type silicon (c-Si) core/hydrogenated amorphous silicon (a-Si:H) shell. By varying either the doping concentration of the c-Si core, or back contact work function we can separate and highlight the contribution to the cell's performance of the nanowires themselves (the radial cell) from the interspace between the nanowires (the planar cell). We show that the build-in potential (V bi ) in the radial and planar cells strongly depends on the doping of c-Si core and the work function of the back contact respectively. Consequently, the solar cell's performance is degraded if either the doping concentration of the c-Si core, or/and the work function of the back contact is too low. By inserting a thin (p) a-Si:H layer between both core/absorber and back contact/absorber, the performance of the solar cell can be improved by partly fixing the V bi at both interfaces due to strong electrostatic screening effect. Depositing such a buffer layer playing the role of an electrostatic screen for charge carriers is a suggested way of enhancing the performance of solar cells based on radial p-i-n or n-i-p nanowire array.

Optoelectrical modeling of solar cells based on c-Si/a-Si:H nanowire array: focus on the electrical transport in between the nanowires

NASA Astrophysics Data System (ADS)

Levtchenko, Alexandra; Le Gall, Sylvain; Lachaume, Raphaël; Michallon, Jérôme; Collin, Stéphane; Alvarez, José; Djebbour, Zakaria; Kleider, Jean-Paul

2018-06-01

By coupling optical and electrical modeling, we have investigated the photovoltaic performances of p-i-n radial nanowires array based on crystalline p-type silicon (c-Si) core/hydrogenated amorphous silicon (a-Si:H) shell. By varying either the doping concentration of the c-Si core, or back contact work function we can separate and highlight the contribution to the cell’s performance of the nanowires themselves (the radial cell) from the interspace between the nanowires (the planar cell). We show that the build-in potential (V bi) in the radial and planar cells strongly depends on the doping of c-Si core and the work function of the back contact respectively. Consequently, the solar cell’s performance is degraded if either the doping concentration of the c-Si core, or/and the work function of the back contact is too low. By inserting a thin (p) a-Si:H layer between both core/absorber and back contact/absorber, the performance of the solar cell can be improved by partly fixing the V bi at both interfaces due to strong electrostatic screening effect. Depositing such a buffer layer playing the role of an electrostatic screen for charge carriers is a suggested way of enhancing the performance of solar cells based on radial p-i-n or n-i-p nanowire array.

Transparent capacitors with hybrid ZnO:Al and Ag nanowires as electrodes.

PubMed

Zhang, Guozhen; Wu, Hao; Wang, Xiao; Wang, Ti; Liu, Chang

2016-03-11

Transparent conducting films with a composite structure of AlZnO-Ag nanowires (AgNWs) have been prepared by atomic layer deposition. The sheet resistance was reduced from 120 to 9 Ω when the AgNW networks were involved. Transparent capacitors with Al2O3-TiO2-Al2O3 dielectrics were fabricated on the composite electrodes and demonstrated a capacitance density of 10.1 fF μm(-2), which was significantly higher than that of capacitors with AlZnO electrodes (8.8 fF μm(-1)). The capacitance density remained almost unchanged in a broad frequency range from 3 kHz to 1 MHz. Moreover, a low leakage current density of 2.4 × 10(-7) A cm(-2) at 1 V was achieved. Transparent and flexible capacitors were also fabricated using the composite electrodes, and demonstrated an improved bendability. The transparent capacitors showed an average optical transmittance over 70% in the visible range, and thus open the door to practical applications in transparent integrated circuits.

Copper Antimonide Nanowire Array Lithium Ion Anodes Stabilized by Electrolyte Additives.

PubMed

Jackson, Everett D; Prieto, Amy L

2016-11-09

Nanowires of electrochemically active electrode materials for lithium ion batteries represent a unique system that allows for intensive investigations of surface phenomena. In particular, highly ordered nanowire arrays produced by electrodeposition into anodic aluminum oxide templates can lead to new insights into a material's electrochemical performance by providing a high-surface-area electrode with negligible volume expansion induced pulverization. Here we show that for the Li-Cu x Sb ternary system, stabilizing the surface chemistry is the most critical factor for promoting long electrode life. The resulting solid electrolyte interphase is analyzed using a mix of electron microscopy, X-ray photoelectron spectroscopy, and lithium ion battery half-cell testing to provide a better understanding of the importance of electrolyte composition on this multicomponent alloy anode material.

Electrochemical properties of high-power supercapacitors using ordered NiO coated Si nanowire array electrodes

NASA Astrophysics Data System (ADS)

Lu, Fang; Qiu, Mengchun; Qi, Xiang; Yang, Liwen; Yin, Jinjie; Hao, Guolin; Feng, Xiang; Li, Jun; Zhong, Jianxin

2011-08-01

Highly ordered NiO coated Si nanowire arrays are fabricated as electrode materials for electrochemical supercapacitors (ES) via depositing Ni on electroless-etched Si nanowires and subsequently annealing. The electrochemical tests reveal that the constructed electrode has superior electrical conductibility and more active sites per unit area for chemical reaction processes, thereby possessing good cycle stability, high specific capacity, and low internal resistance. The specific capacity is up to 787.5 F g-1 at a discharge current of 2.5 mA and decreases slightly with 4.039% loss after 500 cycles, while the equivalent internal resistance is ˜3.067 Ω. Owing to its favorable electrochemical performance, this ordered hybrid array nanostructure is a promising electrode material in future commercial ES.

Optical absorption enhancement in silicon nanowire arrays with a large lattice constant for photovoltaic applications.

PubMed

Lin, Chenxi; Povinelli, Michelle L

2009-10-26

In this paper, we use the transfer matrix method to calculate the optical absorptance of vertically-aligned silicon nanowire (SiNW) arrays. For fixed filling ratio, significant optical absorption enhancement occurs when the lattice constant is increased from 100 nm to 600 nm. The enhancement arises from an increase in field concentration within the nanowire as well as excitation of guided resonance modes. We quantify the absorption enhancement in terms of ultimate efficiency. Results show that an optimized SiNW array with lattice constant of 600 nm and wire diameter of 540 nm has a 72.4% higher ultimate efficiency than a Si thin film of equal thickness. The enhancement effect can be maintained over a large range of incidence angles.

A Water-Based Silver-Nanowire Screen-Print Ink for the Fabrication of Stretchable Conductors and Wearable Thin-Film Transistors.

PubMed

Liang, Jiajie; Tong, Kwing; Pei, Qibing

2016-07-01

A water-based silver-nanowire (AgNW) ink is formulated for screen printing. Screen-printed AgNW patterns have uniform sharp edges, ≈50 μm resolution, and electrical conductivity as high as 4.67 × 10(4) S cm(-1) . The screen-printed AgNW patterns are used to fabricate a stretchable composite conductor, and a fully printed and intrinsically stretchable thin-film transistor array is also realized. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polyaniline nanowire array encapsulated in titania nanotubes as a superior electrode for supercapacitors.

PubMed

Xie, Keyu; Li, Jie; Lai, Yanqing; Zhang, Zhi'an; Liu, Yexiang; Zhang, Guoge; Huang, Haitao

2011-05-01

Conducting polymer with 1D nanostructure exhibits excellent electrochemical performances but a poor cyclability that limits its use in supercapacitors. In this work, a novel composite electrode made of polyaniline nanowire-titania nanotube array was synthesized via a simple and inexpensive electrochemical route by electropolymerizing aniline onto an anodized titania nanotube array. The specific capacitance was as high as 732 F g(-1) at 1 A g(-1), which remained at 543 F g(-1) when the current density was increased by 20 times. 74% of the maximum energy density (36.6 Wh kg(-1)) was maintained even at a high power density of 6000 W kg(-1). An excellent long cycle life of the electrode was observed with a retention of ∼86% of the initial specific capacitance after 2000 cycles. The good electrochemical performance was attributed to the unique microstructure of the electrode with disordered PANI nanowire arrays encapsulated inside the TiO(2) nanotubes, providing high surface area, fast diffusion path for ions and long-term cycle stability. Such a nanocomposite electrode is attractive for supercapacitor applications. © The Royal Society of Chemistry 2011

Unique X-ray emission characteristics from volumetrically heated nanowire array plasmas

NASA Astrophysics Data System (ADS)

Rocca, J. J.; Bargsten, C.; Hollinger, R.; Shlyaptsev, V.; Pukhov, A.; Kaymak, V.; Capeluto, G.; Keiss, D.; Townsend, A.; Rockwood, A.; Wang, Y.; Wang, S.

2015-11-01

Highly anisotropic emission of hard X-ray radiation (h ν >10 keV) is observed when arrays of ordered nanowires (50 nm diameter wires of Au or Ni) are volumetrically heated by normal incidence irradiation with high contrast 50-60 fs laser pulses of relativistic intensity. The annular emission is in contrast with angular distribution of softer X-rays (h ν >1 KeV) from these targets and with the X-ray radiation emitted by polished flat targets, both of which are nearly isotropic. Model computations that make use the electron energy distribution computed by particle-in-cell simulations show that the unexpected annular distribution of the hard x-rays is the result of bremsstrahlung from fast electrons. Volumetric heating of Au nanowire arrays irradiated with an intensity of 2 x 10 19 W cm-2 is measured to convert laser energy into h ν>1KeV photons with a record efficiency of >8 percent into 2 π, creating a bright picosecond X-ray source for applications. Work supported by the Office of Fusion Energy Science of the U.S Department of Energy, and the Defense Threat Reduction Agency. A.P was supported by DFG project TR18.

Fabrication of arrayed Si nanowire-based nano-floating gate memory devices on flexible plastics.

PubMed

Yoon, Changjoon; Jeon, Youngin; Yun, Junggwon; Kim, Sangsig

2012-01-01

Arrayed Si nanowire (NW)-based nano-floating gate memory (NFGM) devices with Pt nanoparticles (NPs) embedded in Al2O3 gate layers are successfully constructed on flexible plastics by top-down approaches. Ten arrayed Si NW-based NFGM devices are positioned on the first level. Cross-linked poly-4-vinylphenol (PVP) layers are spin-coated on them as isolation layers between the first and second level, and another ten devices are stacked on the cross-linked PVP isolation layers. The electrical characteristics of the representative Si NW-based NFGM devices on the first and second levels exhibit threshold voltage shifts, indicating the trapping and detrapping of electrons in their NPs nodes. They have an average threshold voltage shift of 2.5 V with good retention times of more than 5 x 10(4) s. Moreover, most of the devices successfully retain their electrical characteristics after about one thousand bending cycles. These well-arrayed and stacked Si NW-based NFGM devices demonstrate the potential of nanowire-based devices for large-scale integration.

Polarization-tuned Dynamic Color Filters Incorporating a Dielectric-loaded Aluminum Nanowire Array

PubMed Central

Raj Shrestha, Vivek; Lee, Sang-Shin; Kim, Eun-Soo; Choi, Duk-Yong

2015-01-01

Nanostructured spectral filters enabling dynamic color-tuning are saliently attractive for implementing ultra-compact color displays and imaging devices. Realization of polarization-induced dynamic color-tuning via one-dimensional periodic nanostructures is highly challenging due to the absence of plasmonic resonances for transverse-electric polarization. Here we demonstrate highly efficient dynamic subtractive color filters incorporating a dielectric-loaded aluminum nanowire array, providing a continuum of customized color according to the incident polarization. Dynamic color filtering was realized relying on selective suppression in transmission spectra via plasmonic resonance at a metal-dielectric interface and guided-mode resonance for a metal-clad dielectric waveguide, each occurring at their characteristic wavelengths for transverse-magnetic and electric polarizations, respectively. A broad palette of colors, including cyan, magenta, and yellow, has been attained with high transmission beyond 80%, by tailoring the period of the nanowire array and the incident polarization. Thanks to low cost, high durability, and mass producibility of the aluminum adopted for the proposed devices, they are anticipated to be diversely applied to color displays, holographic imaging, information encoding, and anti-counterfeiting. PMID:26211625

Flexible ultraviolet photodetectors based on ZnO-SnO2 heterojunction nanowire arrays

NASA Astrophysics Data System (ADS)

Lou, Zheng; Yang, Xiaoli; Chen, Haoran; Liang, Zhongzhu

2018-02-01

A ZnO-SnO2 nanowires (NWs) array, as a metal oxide semiconductor, was successfully synthesized by a near-field electrospinning method for the applications as high performance ultraviolet photodetectors. Ultraviolet photodetectors based on a single nanowire exhibited excellent photoresponse properties to 300 nm ultraviolet light illumination including ultrahigh I on/I off ratios (up to 103), good stability and reproducibility because of the separation between photo-generated electron-hole pairs. Moreover, the NWs array shows an enhanced photosensing performance. Flexible photodetectors on the PI substrates with similar tendency properties were also fabricated. In addition, under various bending curvatures and cycles, the as-fabricated flexible photodetectors revealed mechanical flexibility and good stable electrical properties, showing that they have the potential for applications in future flexible photoelectron devices. Project supported by the National Science Foundation of China (No. 61504136) and the State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine and Physics, Chinese Academy of Sciences.

Facile Synthesis of Ultrafine Hematite Nanowire Arrays in Mixed Water-Ethanol-Acetic Acid Solution for Enhanced Charge Transport and Separation.

PubMed

Wang, Jian; Wang, Menglong; Zhang, Tao; Wang, Zhiqiang; Guo, Penghui; Su, Jinzhan; Guo, Liejin

2018-04-18

Nanostructure engineering is of great significance for semiconductor electrode to achieve high photoelectrochemical performance. Herein, we report a novel strategy to fabricate ultrafine hematite (α-Fe 2 O 3 ) nanowire arrays in a mixed water-ethanol-acetic acid (WEA) solvent. To the best of our knowledge, this is the first report on direct growth of ultrafine (∼10 nm) α-Fe 2 O 3 nanowire arrays on fluorine-doped tin oxide substrates through solution-based fabrication process. The effect of WEA ratio on the morphology of nanowires has been systematically studied to understand the formation mechanism. Photoelectrochemical measurements were conducted on both Ti-treated α-Fe 2 O 3 nanowire and nanorod photoelectrodes. It reveals that α-Fe 2 O 3 nanowire electrode has higher photocurrent and charge separation efficiencies than nanorod electrode if the carrier concentration and space-charge carrier width are in the same order of magnitude. Normalized by electrochemically active surface area, the Ti-treated α-Fe 2 O 3 nanowire electrode obtains 6.4 times higher specific photocurrent density than nanorod electrode. This superiority of nanowires arises from the higher bulk and surface charge separation efficiencies, which could be partly attributed to reduced distance that holes must transfer to reach the semiconductor-liquid junction.

A high efficiency dual-junction solar cell implemented as a nanowire array.

PubMed

Yu, Shuqing; Witzigmann, Bernd

2013-01-14

In this work, we present an innovative design of a dual-junction nanowire array solar cell. Using a dual-diameter nanowire structure, the solar spectrum is separated and absorbed in the core wire and the shell wire with respect to the wavelength. This solar cell provides high optical absorptivity over the entire spectrum due to an electromagnetic concentration effect. Microscopic simulations were performed in a three-dimensional setup, and the optical properties of the structure were evaluated by solving Maxwell's equations. The Shockley-Queisser method was employed to calculate the current-voltage relationship of the dual-junction structure. Proper design of the geometrical and material parameters leads to an efficiency of 39.1%.

Dynamical formation of spatially localized arrays of aligned nanowires in plastic films with magnetic anisotropy.

PubMed

Fragouli, Despina; Buonsanti, Raffaella; Bertoni, Giovanni; Sangregorio, Claudio; Innocenti, Claudia; Falqui, Andrea; Gatteschi, Dante; Cozzoli, Pantaleo Davide; Athanassiou, Athanassia; Cingolani, Roberto

2010-04-27

We present a simple technique for magnetic-field-induced formation, assembling, and positioning of magnetic nanowires in a polymer film. Starting from a polymer/iron oxide nanoparticle casted solution that is allowed to dry along with the application of a weak magnetic field, nanocomposite films incorporating aligned nanocrystal-built nanowire arrays are obtained. The control of the dimensions of the nanowires and of their localization across the polymer matrix is achieved by varying the duration of the applied magnetic field, in combination with the evaporation dynamics. These multifunctional anisotropic free-standing nanocomposite films, which demonstrate high magnetic anisotropy, can be used in a wide field of technological applications, ranging from sensors to microfluidics and magnetic devices.

Localized, stepwise template growth of functional nanowires from an amino acid-supported framework in a microfluidic chip.

PubMed

Puigmartí-Luis, Josep; Rubio-Martínez, Marta; Imaz, Inhar; Cvetković, Benjamin Z; Abad, Llibertat; Pérez Del Pino, Angel; Maspoch, Daniel; Amabilino, David B

2014-01-28

A spatially controlled synthesis of nanowire bundles of the functional crystalline coordination polymer (CP) Ag(I)TCNQ (tetracyanoquinodimethane) from previously fabricated and trapped monovalent silver CP (Ag(I)Cys (cysteine)) using a room-temperature microfluidic-assisted templated growth method is demonstrated. The incorporation of microengineered pneumatic clamps in a two-layer polydimethylsiloxane-based (PDMS) microfluidic platform was used. Apart from guiding the formation of the Ag(I)Cys coordination polymer, this microfluidic approach enables a local trapping of the in situ synthesized structures with a simple pneumatic clamp actuation. This method not only enables continuous and multiple chemical events to be conducted upon the trapped structures, but the excellent fluid handling ensures a precise chemical activation of the amino acid-supported framework in a position controlled by interface and clamp location that leads to a site-specific growth of Ag(I)TCNQ nanowire bundles. The synthesis is conducted stepwise starting with Ag(I)Cys CPs, going through silver metal, and back to a functional CP (Ag(I)TCNQ); that is, a novel microfluidic controlled ligand exchange (CP → NP → CP) is presented. Additionally, the pneumatic clamps can be employed further to integrate the conductive Ag(I)TCNQ nanowire bundles onto electrode arrays located on a surface, hence facilitating the construction of the final functional interfaced systems from solution specifically with no need for postassembly manipulation. This localized self-supported growth of functional matter from an amino acid-based CP shows how sequential localized chemistry in a fluid cell can be used to integrate molecular systems onto device platforms using a chip incorporating microengineered pneumatic tools. The control of clamp pressure and in parallel the variation of relative flow rates of source solutions permit deposition of materials at different locations on a chip that could be useful for device

Controlled Growth of Parallel Oriented ZnO Nanostructural Arrays on Ga2O3 Nanowires

DTIC Science & Technology

2008-11-01

Controlled Growth of Parallel Oriented ZnO Nanostructural Arrays on Ga2O3 Nanowires Lena Mazeina,* Yoosuf N. Picard, and Sharka M. Prokes Electronics...Manuscript ReceiVed NoVember 6, 2008 ABSTRACT: Novel hierarchical ZnO- Ga2O3 nanostructures were fabricated via a two stage growth process. Nanowires of Ga2O3 ...nanobrushes (NBs) with Ga2O3 as the core and ZnO as the branches self-assembling symmetrically in six equiangular directions around the core

Template-Stripped Smooth Ag Nanohole Arrays with Silica Shells for Surface Plasmon Resonance Biosensing

PubMed Central

Im, Hyungsoon; Lee, Si Hoon; Wittenberg, Nathan J.; Johnson, Timothy W.; Lindquist, Nathan C.; Nagpal, Prashant; Norris, David J.; Oh, Sang-Hyun

2011-01-01

Inexpensive, reproducible and high-throughput fabrication of nanometric apertures in metallic films can benefit many applications in plasmonics, sensing, spectroscopy, lithography and imaging. Here we use template stripping to pattern periodic nanohole arrays in optically thick, smooth Ag films with a silicon template made via nanoimprint lithography. Ag is a low-cost material with good optical properties, but it suffers from poor chemical stability and biocompatibility. However, a thin silica shell encapsulating our template-stripped Ag nanoholes facilitates biosensing applications by protecting the Ag from oxidation as well as providing a robust surface that can be readily modified with a variety of biomolecules using well-established silane chemistry. The thickness of the conformal silica shell can be precisely tuned by atomic layer deposition, and a 15-nm-thick silica shell can effectively prevent fluorophore quenching. The Ag nanohole arrays with silica shells can also be bonded to polydimethylsiloxane (PDMS) microfluidic channels for fluorescence imaging, formation of supported lipid bilayers, and real-time, label-free SPR sensing. Additionally, the smooth surfaces of the template-stripped Ag films enhance refractive index sensitivity compared with as-deposited, rough Ag films. Because nearly centimeter-sized nanohole arrays can be produced inexpensively without using any additional lithography, etching or lift-off, this method can facilitate widespread applications of metallic nanohole arrays for plasmonics and biosensing. PMID:21770414

Hydrothermal Growth of ZnO Nanowires on UV-Nanoimprinted Polymer Structures.

PubMed

Park, Sooyeon; Moore, Sean A; Lee, Jaejong; Song, In-Hyouk; Farshchian, Bahador; Kim, Namwon

2018-05-01

Integration of zinc oxide (ZnO) nanowires on miniaturized polymer structures can broaden its application in multi-functional polymer devices by taking advantages of unique physical properties of ZnO nanowires and recent development of polymer microstructures in analytical systems. In this paper, we demonstrate the hydrothermal growth of ZnO nanowires on polymer microstructures fabricated by UV nanoimprinting lithography (NIL) using a polyurethane acrylate (PUA). Since PUA is a siloxane-urethane-acrylate compound containing the alpha-hydroxyl ketone, UV-cured PUA include carboxyl groups, which inhibit and suppress the nucleation and growth of ZnO nanowires on polymer structures. The presence of carboxyl groups in UV-cured PUA was substantiated by Fourier transform infrared spectroscopy (FTIR), and a Ag thin film was deposited on the nanoimprinted polymer structures to limit their inhibitive influence on the growth of ZnO nanowires. Furthermore, the naturally oxidized Ag layer (Ag2O) reduced crystalline lattice mismatches at the interface between ZnO-Ag during the seed annealing process. The ZnO nanowires grown on the Ag-deposited PUA microstructures were found to have comparable morphological characteristics with ZnO nanowires grown on a Si wafer.

Optical design of GaN nanowire arrays for photocatalytic applications

NASA Astrophysics Data System (ADS)

Winnerl, Julia; Hudeczek, Richard; Stutzmann, Martin

2018-05-01

GaN nanowire (NW) arrays are interesting candidates for photocatalytic applications due to their high surface-to-volume ratio and their waveguide character. The integration of GaN NW arrays on GaN-based light emitting diodes (LEDs), serving as a platform for electrically driven NW-based photocatalytic devices, enables an efficient coupling of the light from the planar LED to the GaN NWs. Here, we present a numerical study of the influence of the NW geometries, i.e., the NW diameter, length, and period, and the illumination wavelength on the transmission of GaN NW arrays on transparent substrates. A detailed numerical analysis reveals that the transmission characteristics for large periods are determined by the waveguide character of the single NW, whereas for dense GaN NW arrays inter-wire coupling and diffraction effects originating from the periodic arrangement of the GaN NWs dominate the transmission. The numerically simulated results are confirmed by experimental transmission measurements. We also investigate the influence of a dielectric NW shell and of the surrounding medium on the transmission characteristics of a GaN NW array.

Ag nanoparticle-ZnO nanowire hybrid nanostructures as enhanced and robust antimicrobial textiles via a green chemical approach

NASA Astrophysics Data System (ADS)

Li, Zhou; Tang, Haoying; Yuan, Weiwei; Song, Wei; Niu, Yongshan; Yan, Ling; Yu, Min; Dai, Ming; Feng, Siyu; Wang, Menghang; Liu, Tengjiao; Jiang, Peng; Fan, Yubo; Wang, Zhong Lin

2014-04-01

A new approach for fabrication of a long-term and recoverable antimicrobial nanostructure/textile hybrid without increasing the antimicrobial resistance is demonstrated. Using in situ synthesized Ag nanoparticles (NPs) anchored on ZnO nanowires (NWs) grown on textiles by a ‘dip-in and light-irradiation’ green chemical method, we obtained ZnONW@AgNP nanocomposites with small-size and uniform Ag NPs, which have shown superior performance for antibacterial applications. These new Ag/ZnO/textile antimicrobial composites can be used for wound dressings and medical textiles for topical and prophylactic antibacterial treatments, point-of-use water treatment to improve the cleanliness of water and antimicrobial air filters to prevent bioaerosols accumulating in ventilation, heating, and air-conditioning systems.

Reversal modes in FeCoNi nanowire arrays: Correlation between magnetostatic interactions and nanowires length

NASA Astrophysics Data System (ADS)

Samanifar, S.; Almasi Kashi, M.; Ramazani, A.; Alikhani, M.

2015-03-01

FeCoNi nanowire arrays (175 nm in diameter and lengths ranging from 5 to 40 μm) were fabricated into nanopores of hard-anodized aluminum oxide templates using pulsed ac electrodeposition technique. Increasing the length had no considerable effect on the composition and crystalline characteristics of Fe47Co38Ni15 nanowires (NWs). By eliminating the dendrites formed at the bottom of the pores, we report a careful investigation on the effect of magnetostatic interactions on magnetic properties and the effect of nanowire length on reversal modes. Hysteresis loop measurements indicated that increasing the length decreases coercivity and squareness values. On the other hand, first-order reversal curve measurements show a linear correlation between the magnetostatic interactions and length of NWs. Comparing reversal modes of the NWs both experimentally and theoretically using angular dependence of coercivity, we find that when L≤22 μm, a vortex domain wall mode is only occurred. When L>22 μm, a non-monotonic behavior indicates a transition from the vortex to transverse domain wall propagation. As a result, a critical length was found above which the transition between the reversal modes is occurred due the enhanced interactions. The transition angle also shifts toward a lower angle as the length increases. Moreover, with increasing length from 22 to 31 μm, the single domain structure of NWs changes to a pseudo single domain state. A multidomain-like behavior is also found for the longest NWs length.

Design and fabrication of Ni nanowires having periodically hollow nanostructures

NASA Astrophysics Data System (ADS)

Sada, Takao; Fujigaya, Tsuyohiko; Nakashima, Naotoshi

2014-09-01

We propose a concept for the design and fabrication of metal nanowires having periodically hollow nanostructures inside the pores of an anodic aluminum oxide (AAO) membrane using a sacrificial metal. In this study, nickel (Ni) and silver (Ag) were used as the base metal and the sacrificial metal, respectively. Alternating an applied potential between -0.4 and -1.0 V provided alternatively deposited Ni and Ag segments in a Ni-Ag `barcode' nanowire with a diameter of 18 or 35 nm. After etching away the Ag segments, we fabricated Ni nanowires with nanopores of 12 +/- 5.3 nm. Such nanostructure formation is explained by the formation of a Ni shell layer over the surface of the Ag segments due to the strong affinity of Ni2+ for the interior surfaces of AAO. The Ni shell layer allows the Ni segments to remain even after dissolution of the Ag segments. Because the electroplating conditions can be easily controlled, we could carefully adjust the size and pitch of the periodically hollow nanospaces. We also describe a method for the fabrication of Ni nanorods by forming an Ag shell instead of a Ni shell on the Ni-Ag barcode nanowire, in which the interior of the AAO surfaces was modified with a compound bearing a thiol group prior to electroplating.We propose a concept for the design and fabrication of metal nanowires having periodically hollow nanostructures inside the pores of an anodic aluminum oxide (AAO) membrane using a sacrificial metal. In this study, nickel (Ni) and silver (Ag) were used as the base metal and the sacrificial metal, respectively. Alternating an applied potential between -0.4 and -1.0 V provided alternatively deposited Ni and Ag segments in a Ni-Ag `barcode' nanowire with a diameter of 18 or 35 nm. After etching away the Ag segments, we fabricated Ni nanowires with nanopores of 12 +/- 5.3 nm. Such nanostructure formation is explained by the formation of a Ni shell layer over the surface of the Ag segments due to the strong affinity of Ni2+ for the

Hyperbolic and Plasmonic Properties of Silicon/Ag Aligned Nanowire Arrays

DTIC Science & Technology

2013-06-17

Cleveland, J. D. Caldwell, E. Foos, J. Niinistö, and M. Ritala, “Spoof-like plasmonic behavior of plasma enhanced atomic layer deposition grown Ag thin...M. Leskela, “ Plasma -enhanced atomic layer deposition of silver thin films,” Chem. Mater. 23(11), 2901–2907 (2011). 52. O. J. Glembocki, S. M. Prokes...all principal components of the dielectric permittivity tensor are positive, the iso-frequency surface is “closed” and forms a spheroid or ellipsoid

Smart integration of silicon nanowire arrays in all-silicon thermoelectric micro-nanogenerators

NASA Astrophysics Data System (ADS)

Fonseca, Luis; Santos, Jose-Domingo; Roncaglia, Alberto; Narducci, Dario; Calaza, Carlos; Salleras, Marc; Donmez, Inci; Tarancon, Albert; Morata, Alex; Gadea, Gerard; Belsito, Luca; Zulian, Laura

2016-08-01

Micro and nanotechnologies are called to play a key role in the fabrication of small and low cost sensors with excellent performance enabling new continuous monitoring scenarios and distributed intelligence paradigms (Internet of Things, Trillion Sensors). Harvesting devices providing energy autonomy to those large numbers of microsensors will be essential. In those scenarios where waste heat sources are present, thermoelectricity will be the obvious choice. However, miniaturization of state of the art thermoelectric modules is not easy with the current technologies used for their fabrication. Micro and nanotechnologies offer an interesting alternative considering that silicon in nanowire form is a material with a promising thermoelectric figure of merit. This paper presents two approaches for the integration of large numbers of silicon nanowires in a cost-effective and practical way using only micromachining and thin-film processes compatible with silicon technologies. Both approaches lead to automated physical and electrical integration of medium-high density stacked arrays of crystalline or polycrystalline silicon nanowires with arbitrary length (tens to hundreds microns) and diameters below 100 nm.

Synthesis and Characteristics of Large-Area and High-Filling CdS Nanowire Arrays in AAO Template.

PubMed

Lv, Xiao-Yi; Hou, Jun-Wei; Gao, Zhi-Xian; Liu, Hong-Fei

2018-05-01

CdS nanowires arrays were successfully synthesized by a simple solvothermal process using AAO as templates. The phase structures, morphologies, and optical properties of the products were investigated by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, and photoluminescence spectroscopy. It was found that the nanowires were composed of hexagonal structure CdS nanoparticles and the average diameters is about 60-70 nm. A strong green emission with a maximum around 505 nm was observed from the synthesized CdS nanowires at room temperature, which was attributed to near-band-edge emission. A 3D self-seed nucleation coalescent process was proposed for the formation of CdS nanowires structures. The present synthetic route is expected to be applied to the synthesis of other II-VI groups or other group's 1D semiconducting materials.

Magnetization mechanisms in ordered arrays of polycrystalline Fe{sub 100−x}Co{sub x} nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Viqueira, M. S.; Bajales, N.; Urreta, S. E.

2015-05-28

Magnetization reversal processes and coercivity mechanisms in polycrystalline Fe{sub 100−x}Co{sub x} nanowire arrays, resulting from an AC electrodeposition process, are investigated. The array coercivity is described on the basis of polarization reversal mechanisms operating in individual wires, under the effect of inter-wire dipolar interactions described by a mean field approximation. For individual wires, a reversal mechanism involving the nucleation and further expansion of domain-wall like spin configuration is considered. The wires have a mean grain size larger than both the nanowire diameter and the exchange length, so localized and non-cooperative nucleation modes are considered. As the Co content increases, themore » alloy saturation polarization gradually decreases, but the coercive field and the relative remanence of the arrays increase, indicating that they are not controlled by the shape anisotropy in all the composition range. The coercive field dependence on the angle between the applied field and the wire long axis is not well described by reversal mechanisms involving nucleation and further displacement of neither vortex nor transverse ideal domain walls. On the contrary, the angular dependence of the coercive field observed at room temperature is well predicted by a model considering nucleation of inverse domains by localized curling, in regions smaller than the grain size, exhibiting quite small aspect ratios as compared to those of the entire nanowire. In arrays with higher Co contents, a transition from an initial (small angle) localized curling nucleation mechanism to another one, involving localized coherent rotation is observed at about π/4.« less

Fabrication of Sb₂S₃ Hybrid Solar Cells Based on Embedded Photoelectrodes of Ag Nanowires-Au Nanoparticles Composite.

PubMed

Kim, Kang-Pil; Hwang, Dae-Kue; Woo, Sung-Ho; Kim, Dae-Hwan

2018-09-01

The Ag nanowire (NW) + Au nanoparticle (NP)-embedded TiO2 photoelectrodes were adopted for conventional planar TiO2-based Sb2S3 hybrid solar cells to improve the cell efficiency. Compared to conventional planar TiO2-based Sb2S3 hybrid solar cells, the Ag NW + Au NP/TiO2-based Sb2S3 hybrid solar cells exhibited an improvement of approximately 40% in the cell efficiency due to the significant increase in both Jsc and Voc. These enhanced Jsc and Voc were attributed to the increased surface area, charge-collection efficiency, and light absorption by embedding the Ag NWs + Au NPs composite. The Ag NW + Au NP/TiO2-based Sb2S3 hybrid solar cells showed the highest efficiency of 2.17%, demonstrating that the Ag NW + Au NP-embedded TiO2 photoelectrode was a suitable photoelectrode structure to improve the power conversion efficiency in the Sb2S3 hybrid solar cells.

Magnetic interactions and reversal mechanisms in Co nanowire and nanotube arrays

NASA Astrophysics Data System (ADS)

Proenca, M. P.; Sousa, C. T.; Escrig, J.; Ventura, J.; Vazquez, M.; Araujo, J. P.

2013-03-01

Ordered hexagonal arrays of Co nanowires (NWs) and nanotubes (NTs), with diameters between 40 and 65 nm, were prepared by potentiostatic electrodeposition into suitably modified nanoporous alumina templates. The geometrical parameters of the NW/NT arrays were tuned by the pore etching process and deposition conditions. The magnetic interactions between NWs/NTs with different diameters were studied using first-order reversal curves (FORCs). From a quantitative analysis of the FORC measurements, we are able to obtain the profiles of the magnetic interactions and the coercive field distributions. In both NW and NT arrays, the magnetic interactions were found to increase with the diameter of the NWs/NTs, exhibiting higher values for NW arrays. A comparative study of the magnetization reversal processes was also performed by analyzing the angular dependence of the coercivity and correlating the experimental data with theoretical calculations based on a simple analytical model. The magnetization in the NW arrays is found to reverse by the nucleation and propagation of a transverse-like domain wall; on the other hand, for the NT arrays a non-monotonic behavior occurs above a diameter of ˜50 nm, revealing a transition between the vortex and transverse reversal modes.

Combined flame and electrodeposition synthesis of energetic coaxial tungsten-oxide/aluminum nanowire arrays.

PubMed

Dong, Zhizhong; Al-Sharab, Jafar F; Kear, Bernard H; Tse, Stephen D

2013-09-11

A nanostructured thermite composite comprising an array of tungsten-oxide (WO2.9) nanowires (diameters of 20-50 nm and lengths of >10 μm) coated with single-crystal aluminum (thickness of ~16 nm) has been fabricated. The method involves combined flame synthesis of tungsten-oxide nanowires and ionic-liquid electrodeposition of aluminum. The geometry not only presents an avenue to tailor heat-release characteristics due to anisotropic arrangement of fuel and oxidizer but also eliminates or minimizes the presence of an interfacial Al2O3 passivation layer. Upon ignition, the energetic nanocomposite exhibits strong exothermicity, thereby being useful for fundamental study of aluminothermic reactions as well as enhancing combustion characteristics.

Flexible Dye-Sensitized Solar Cell Based on Vertical ZnO Nanowire Arrays

PubMed Central

2011-01-01

Flexible dye-sensitized solar cells are fabricated using vertically aligned ZnO nanowire arrays that are transferred onto ITO-coated poly(ethylene terephthalate) substrates using a simple peel-off process. The solar cells demonstrate an energy conversion efficiency of 0.44% with good bending tolerance. This technique paves a new route for building large-scale cost-effective flexible photovoltaic and optoelectronic devices. PMID:27502660

Process Development of Gallium Nitride Phosphide Core-Shell Nanowire Array Solar Cell

NASA Astrophysics Data System (ADS)

Chuang, Chen

Dilute Nitride GaNP is a promising materials for opto-electronic applications due to its band gap tunability. The efficiency of GaNxP1-x /GaNyP1-y core-shell nanowire solar cell (NWSC) is expected to reach as high as 44% by 1% N and 9% N in the core and shell, respectively. By developing such high efficiency NWSCs on silicon substrate, a further reduction of the cost of solar photovoltaic can be further reduced to 61$/MWh, which is competitive to levelized cost of electricity (LCOE) of fossil fuels. Therefore, a suitable NWSC structure and fabrication process need to be developed to achieve this promising NWSC. This thesis is devoted to the study on the development of fabrication process of GaNxP 1-x/GaNyP1-y core-shell Nanowire solar cell. The thesis is divided into two major parts. In the first parts, previously grown GaP/GaNyP1-y core-shell nanowire samples are used to develop the fabrication process of Gallium Nitride Phosphide nanowire solar cell. The design for nanowire arrays, passivation layer, polymeric filler spacer, transparent col- lecting layer and metal contact are discussed and fabricated. The property of these NWSCs are also characterized to point out the future development of Gal- lium Nitride Phosphide NWSC. In the second part, a nano-hole template made by nanosphere lithography is studied for selective area growth of nanowires to improve the structure of core-shell NWSC. The fabrication process of nano-hole templates and the results are presented. To have a consistent features of nano-hole tem- plate, the Taguchi Method is used to optimize the fabrication process of nano-hole templates.

High efficiency single Ag nanowire/p-GaN substrate Schottky junction-based ultraviolet light emitting diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Y.; Li, X.; Xu, P.

2015-02-02

We report a high efficiency single Ag nanowire (NW)/p-GaN substrate Schottky junction-based ultraviolet light emitting diode (UV-LED). The device demonstrates deep UV free exciton electroluminescence at 362.5 nm. The dominant emission, detectable at ultralow (<1 μA) forward current, does not exhibit any shifts when the forward current is increased. External quantum efficiency (EQE) as high as 0.9% is achieved at 25 μA current at room temperature. Experiments and simulation analysis show that devices fabricated with thinner Ag NWs have higher EQE. However, for very thin Ag NWs (diameter < 250 nm), this trend breaks down due to heat accumulation in the NWs. Our simple device architecturemore » offers a potentially cost-effective scheme to fabricate high efficiency Schottky junction-based UV-LEDs.« less

Facile fabrication of Ag nanowires for capacitive flexible pressure sensors by liquid polyol reduction method

NASA Astrophysics Data System (ADS)

Wei, Xiongbang; Quan, Yong; Zeng, Hongjuan; Huang, Wen; Li, Weizhi; Liao, Jiaxuan; Chen, Zhi

2018-01-01

The Ag nanowires (AgNWs) were prepared by improved liquid polyol reduction method, and the AgNWs were successfully applied to the capacitive flexible pressure sensors. Firstly, the one-dimensional radial growth conditions of AgNWs were optimized from four aspects of the molecular weight of the protective agent polyvinyl pyrrolidone (PVP), the molar ratio of AgNO3 and PVP, the anion concentration of the metal salt and the reaction temperature. The effect of polymerization degree of protective agent on one-dimensional radial growth of AgNWs was investigated by using three kinds of protective agents PVP-K-30, PVP-K-60 and PVP-K-90. Three different AgNO3 and PVP molar ratios of 1:1, 1:3 and 1:9 were designed, and the effects of PVP adsorption capacity on one-dimensional radial growth of AgNWs were investigated. Three concentrations of 0 mM NaCl, 16 mM NaCl and 32 mM NaCl were designed to study the effects of anion concentration of the metal salt on the nucleation and etching of silver nanoparticles. The effects of reaction temperature on the growth of AgNWs were studied at three different temperatures of 140 °C, 160 °C and 180 °C, and appropriate temperature design was proposed. In this experiment, the products of AgNWs prepared under various conditions were analyzed by UV-vis Spectrum and SEM, and the experimental conditions were optimized from the synthesis mechanism and reaction conditions.

GaN Nanowire Arrays for Efficient Optical Read-Out and Optoelectronic Control of NV Centers in Diamond.

PubMed

Hetzl, Martin; Wierzbowski, Jakob; Hoffmann, Theresa; Kraut, Max; Zuerbig, Verena; Nebel, Christoph E; Müller, Kai; Finley, Jonathan J; Stutzmann, Martin

2018-06-13

Solid-state quantum emitters embedded in a semiconductor crystal environment are potentially scalable platforms for quantum optical networks operated at room temperature. Prominent representatives are nitrogen-vacancy (NV) centers in diamond showing coherent entanglement and interference with each other. However, these emitters suffer from inefficient optical outcoupling from the diamond and from fluctuations of their charge state. Here, we demonstrate the implementation of regular n-type gallium nitride nanowire arrays on diamond as photonic waveguides to tailor the emission direction of surface-near NV centers and to electrically control their charge state in a p-i-n nanodiode. We show that the electrical excitation of single NV centers in such a diode can efficiently replace optical pumping. By the engineering of the array parameters, we find an optical read-out efficiency enhanced by a factor of 10 and predict a lateral NV-NV coupling 3 orders of magnitude stronger through evanescently coupled nanowire antennas compared to planar diamond not covered by nanowires, which opens up new possibilities for large-scale on-chip quantum-computing applications.

III-Nitride Nanowire Lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wright, Jeremy Benjamin

2014-07-01

In recent years there has been a tremendous interest in nanoscale optoelectronic devices. Among these devices are semiconductor nanowires whose diameters range from 10-100 nm. To date, nanowires have been grown using many semiconducting material systems and have been utilized as light emitting diodes, photodetectors, and solar cells. Nanowires possess a relatively large index contrast relative to their dielectric environment and can be used as lasers. A key gure of merit that allows for nanowire lasing is the relatively high optical con nement factor. In this work, I discuss the optical characterization of 3 types of III-nitride nanowire laser devices.more » Two devices were designed to reduce the number of lasing modes to achieve singlemode operation. The third device implements low-group velocity mode lasing with a photonic crystal constructed of an array of nanowires. Single-mode operation is necessary in any application where high beam quality and single frequency operation is required. III-Nitride nanowire lasers typically operate in a combined multi-longitudinal and multi-transverse mode state. Two schemes are introduced here for controlling the optical modes and achieving single-mode op eration. The rst method involves reducing the diameter of individual nanowires to the cut-o condition, where only one optical mode propagates in the wire. The second method employs distributed feedback (DFB) to achieve single-mode lasing by placing individual GaN nanowires onto substrates with etched gratings. The nanowire-grating substrate acted as a distributed feedback mirror producing single mode operation at 370 nm with a mode suppression ratio (MSR) of 17 dB. The usage of lasers for solid state lighting has the potential to further reduce U.S. lighting energy usage through an increase in emitter e ciency. Advances in nanowire fabrication, speci cally a two-step top-down approach, have allowed for the demonstration of a multi-color array of lasers on a single chip that

Green Synthesis of Ag and Pd Nanospheres, Nanowires, and Nanorods Using Vitamin B2: Catalytic Polymerisation of Aniline and Pyrrole

EPA Science Inventory

For the first time, we report green chemistry approach using vitamin B2 in the synthesis of silver (Ag) and palladium (Pd), nanospheres, nanowires and nanorods at room temperature without using any harmful reducing agents, such as sodium borohydride (NaBH4) or hydroxylamine hydro...

Sensors and devices containing ultra-small nanowire arrays

DOEpatents

Xiao, Zhili

2014-09-23

A network of nanowires may be used for a sensor. The nanowires are metallic, each nanowire has a thickness of at most 20 nm, and each nanowire has a width of at most 20 nm. The sensor may include nanowires comprising Pd, and the sensor may sense a change in hydrogen concentration from 0 to 100%. A device may include the hydrogen sensor, such as a vehicle, a fuel cell, a hydrogen storage tank, a facility for manufacturing steel, or a facility for refining petroleum products.

Sensors and devices containing ultra-small nanowire arrays

DOEpatents

Xiao, Zhili

2017-04-11

A network of nanowires may be used for a sensor. The nanowires are metallic, each nanowire has a thickness of at most 20 nm, and each nanowire has a width of at most 20 nm. The sensor may include nanowires comprising Pd, and the sensor may sense a change in hydrogen concentration from 0 to 100%. A device may include the hydrogen sensor, such as a vehicle, a fuel cell, a hydrogen storage tank, a facility for manufacturing steel, or a facility for refining petroleum products.

Efficient and scalable ionization of neutral atoms by an orderly array of gold-doped silicon nanowires

NASA Astrophysics Data System (ADS)

Bucay, Igal; Helal, Ahmed; Dunsky, David; Leviyev, Alex; Mallavarapu, Akhila; Sreenivasan, S. V.; Raizen, Mark

2017-04-01

Ionization of atoms and molecules is an important process in many applications and processes such as mass spectrometry. Ionization is typically accomplished by electron bombardment, and while it is scalable to large volumes, is also very inefficient due to the small cross section of electron-atom collisions. Photoionization methods can be highly efficient, but are not scalable due to the small ionization volume. Electric field ionization is accomplished using ultra-sharp conducting tips biased to a few kilovolts, but suffers from a low ionization volume and tip fabrication limitations. We report on our progress towards an efficient, robust, and scalable method of atomic and molecular ionization using orderly arrays of sharp, gold-doped silicon nanowires. As demonstrated in earlier work, the presence of the gold greatly enhances the ionization probability, which was attributed to an increase in available acceptor surface states. We present here a novel process used to fabricate the nanowire array, results of simulations aimed at optimizing the configuration of the array, and our progress towards demonstrating efficient and scalable ionization.

Direct selective growth of ZnO nanowire arrays from inkjet-printed zinc acetate precursor on a heated substrate

PubMed Central

2013-01-01

Inkjet printing of functional materials has drawn tremendous interest as an alternative to the conventional photolithography-based microelectronics fabrication process development. We introduce direct selective nanowire array growth by inkjet printing of Zn acetate precursor ink patterning and subsequent hydrothermal ZnO local growth without nozzle clogging problem which frequently happens in nanoparticle inkjet printing. The proposed process can directly grow ZnO nanowires in any arbitrary patterned shape, and it is basically very fast, low cost, environmentally benign, and low temperature. Therefore, Zn acetate precursor inkjet printing-based direct nanowire local growth is expected to give extremely high flexibility in nanomaterial patterning for high-performance electronics fabrication especially at the development stage. As a proof of concept of the proposed method, ZnO nanowire network-based field effect transistors and ultraviolet photo-detectors were demonstrated by direct patterned grown ZnO nanowires as active layer. PMID:24252130

Fabrication of CoFe2O4 ferrite nanowire arrays in porous silicon template and their local magnetic properties

NASA Astrophysics Data System (ADS)

Hui, Zheng; Man-Gui, Han; Long-Jiang, Deng

2016-02-01

CoFe2O4 ferrite nanowire arrays are fabricated in porous silicon templates. The porous silicon templates are prepared via metal-assisted chemical etching with gold (Au) nanoparticles as the catalyst. Subsequently, CoFe2O4 ferrite nanowires are successfully synthesized into porous silicon templates by the sol-gel method. The magnetic hysteresis loop of nanowire array shows an isotropic feature of magnetic properties. The coercivity and squareness ratio (Mr/Ms) of ensemble nanowires are found to be 630 Oe (1 Oe, = 79.5775 A·m-1 and 0.4 respectively. However, the first-order reversal curve (FORC) is adopted to reveal the probability density function of local magnetostatic properties (i.e., interwire interaction field and coercivity). The FORC diagram shows an obvious distribution feature for interaction field and coercivity. The local coercivity with a value of about 1000 Oe is found to have the highest probability. Project supported by the National Natural Science Foundation of China (Grant No. 61271039), the Scientific Projects of Sichuan Province, China (Grant No. 2015HH0016), and the Natural Science Foundations of Zhejiang Province, China (Grant Nos. LQ12E02001 and Y107255).

Preparation of a γ-Fe2 O3 /Ag nanowire coaxial nanocable for high-performance lithium-ion batteries.

PubMed

Geng, Hongbo; Ge, Danhua; Lu, Shuanglong; Wang, Jiaqing; Ye, Zhengmao; Yang, Yonggang; Zheng, Junwei; Gu, Hongwei

2015-07-27

In this study, we report the design and synthesis of a silver nanowire-γ-Fe2 O3 coaxial nanocable architecture (Ag NWs@γ-Fe2 O3 nanocable) through mild oxidation of [Fe(CO)5 ] on the surface of silver nanowires followed by a calcination process. After optimization of the structural design, the Ag NWs@γ-Fe2 O3 nanocable could deliver superior lithium storage performance in terms of high reversible capacity, good rate performance, and excellent stability, such as a high reversible capacity of about 890 mA h g(-1) after 60 cycles at a current rate of 0.1 C (1.0 C=1005 mA g(-1) ). The reversible capacity remains as high as about 550 mA h g(-1) even at a high current rate of 2.0 C. This dramatic performance is mainly attributed to the smart coaxial design, which can not only alleviate the large volume change and prevent the aggregation of γ-Fe2 O3 nanoparticles, but also enables good conductivity and thus enhances fast charge transfer. The unique structural features of the Ag NWs@γ-Fe2 O3 nanocable represent a promising anode material in lithium-ion battery applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication and characterization of a flow-through nanoporous gold nanowire/AAO composite membrane.

PubMed

Liu, L; Lee, W; Huang, Z; Scholz, R; Gösele, U

2008-08-20

The fabrication of a composite membrane of nanoporous gold nanowires and anodic aluminum oxide (AAO) is demonstrated by the electrodeposition of Au-Ag alloy nanowires into an AAO membrane, followed by selective etching of silver from the alloy nanowires. This composite membrane is advantageous for flow-through type catalytic reactions. The morphology evolution of the nanoporous gold nanowires as a function of the diameter of the Au-Ag nanowire 'precursors' is also investigated.

Synthesis and visible-light-induced catalytic activity of Ag2S-coupled TiO2 nanoparticles and nanowires

NASA Astrophysics Data System (ADS)

Xie, Yi; Heo, Sung Hwan; Kim, Yong Nam; Yoo, Seung Hwa; Cho, Sung Oh

2010-01-01

We present the synthesis and visible-light-induced catalytic activity of Ag2S-coupled TiO2 nanoparticles (NPs) and TiO2 nanowires (NWs). Through a simple wet chemical process from a mixture of peroxo titanic acid (PTA) solution, thiourea and AgAc, a composite of Ag2S NPs and TiO2 NPs with sizes of less than 7 nm was formed. When the NP composite was further treated with NaOH solution followed by annealing at ambient conditions, a new nanocomposite material comprising Ag2S NPs on TiO2 NWs was created. Due to the coupling with such a low bandgap material as Ag2S, the TiO2 nanocomposites could have a visible-light absorption capability much higher than that of pure TiO2. As a result, the synthesized Ag2S/TiO2 nanocomposites exhibited much higher catalytic efficiency for the decomposition of methyl orange than commercial TiO2 (Degussa P25, Germany) under visible light.

X-ray Reflectivity Study of a Highly Rough Surface: Si Nanowires Grown by Ag Nanoparticle Etching

NASA Astrophysics Data System (ADS)

Kremenak, Jesse; Arendse, Christopher; Cummings, Franscious; Chen, Yiyao; Miceli, Paul

Vertically oriented Si nanowires (SiNWs) formed by Ag-assisted wet chemical etching of a Si(100) substrate was studied by X-ray reflectivity (XRR) in combination with electron microscopy. Si(100) wafers coated with Ag nanoparticles, which serve as a catalyst, were etched for different durations in a HF/H2O2/DI-H2O solution. Because of the extreme roughness of these surfaces, there are challenges for using XRR methods in such systems. Therefore, significant attention is given to the analysis method of the XRR measurements. This sample-average information presents a valuable complement to electron microscopy studies, which focus on small sections of the sample. The present work shows-for the first time-the amount and distribution of Ag during the formation of SiNWs fabricated by Ag-assisted wet chemical etching, which is vital information for understanding the etching mechanisms. Support is gratefully acknowledged from the National Science Foundation (USA) - DGE1069091, the National Research Foundation (RSA) - TTK14052167658, 76568, 92520, and 93212; and the University of Missouri/University of Western Cape Linkage Program.

Effects of silicon nanowire morphology on optical properties and hybrid solar cell performance

NASA Astrophysics Data System (ADS)

Syu, Hong-Jhang; Shiu, Shu-Chia; Hung, Yung-Jr; Lee, San-Liang; Lin, Ching-Fuh

2012-10-01

Silicon nanowire (SiNW) arrays are widespread applied on hybrid photovoltaic devices because SiNW arrays can substitute the pyramid texture and anti-reflection coating due to its strong light trapping. Also, SiNWs can be prepared through a cost-efficient process of metal-assisted chemical etching. However, though longer SiNW arrays have lower reflectance, the top of long SiNWs aggregate together to make junction synthesis difficult for SiNW/organic hybrid solar cell. To control and analyze the effect of SiNW array morphology on hybrid solar cells, here we change the metal deposition condition for metal-assisted chemical etching to obtain different SiNW array morphologies. The experiment was separated to two groups, by depositing metal, say, Ag, before etching (BE) or during etching (DE). For group BE, Ag was deposited on n-type Si (n-Si) wafers by thermal evaporation; then etched by H2O2 and HF. For group DE, n-Si was etched by Ag+ and HF directly. Ag was deposited on n-Si during etching process. Afterwards, residual Ag and SiO2 were removed by HNO3 and buffered HF, successively; then Ti and Ag were evaporated on the bottom of Si to be a cathode. Finally, SiNWs were stuck on the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) that was spincoated on the ITO coated glass to form SiNW/organic heterojunction. The results show that group BE has reflectance lower than that in group DE in solar spectrum. However, group BE has smaller power conversion efficiency (PCE) of 8.65% and short-circuit current density (Jsc) of 24.94 mA/cm2 than group DE of PCE of 9.47% and Jsc of 26.81 mA/cm2.

Ultraflexible Transparent Film Heater Made of Ag Nanowire/PVA Composite for Rapid-Response Thermotherapy Pads.

PubMed

Lan, Wei; Chen, Youxin; Yang, Zhiwei; Han, Weihua; Zhou, Jinyuan; Zhang, Yue; Wang, Junya; Tang, Guomei; Wei, Yupeng; Dou, Wei; Su, Qing; Xie, Erqing

2017-02-22

Ultraflexible transparent film heaters have been fabricated by embedding conductive silver (Ag) nanowires into a thin poly(vinyl alcohol) film (AgNW/PVA). A cold-pressing method was used to rationally adjust the sheet resistance of the composite films and thus the heating powers of the AgNW/PVA film heaters at certain biases. The film heaters have a favorable optical transmittance (93.1% at 26 Ω/sq) and an outstanding mechanical flexibility (no visible change in sheet resistance after 10 000 bending cycles and at a radius of curvature ≤1 mm). The film heaters have an environmental endurance, and there is no significant performance degradation after being kept at high temperature (80 °C) and high humidity (45 °C, 80% humidity) for half a year. The efficient Joule heating can increase the temperature of the film heaters (20 Ω/sq) to 74 °C in ∼20 s at a bias of 5 V. The fast-heating characteristics at low voltages (a few volts) associated with its transparent and flexibility properties make the poly(dimethylsiloxane)/AgNW/PVA composite film a potential candidate in medical thermotherapy pads.

Thermal Conduction in Vertically Aligned Copper Nanowire Arrays and Composites.

PubMed

Barako, Michael T; Roy-Panzer, Shilpi; English, Timothy S; Kodama, Takashi; Asheghi, Mehdi; Kenny, Thomas W; Goodson, Kenneth E

2015-09-02

The ability to efficiently and reliably transfer heat between sources and sinks is often a bottleneck in the thermal management of modern energy conversion technologies ranging from microelectronics to thermoelectric power generation. These interfaces contribute parasitic thermal resistances that reduce device performance and are subjected to thermomechanical stresses that degrade device lifetime. Dense arrays of vertically aligned metal nanowires (NWs) offer the unique combination of thermal conductance from the constituent metal and mechanical compliance from the high aspect ratio geometry to increase interfacial heat transfer and device reliability. In the present work, we synthesize copper NW arrays directly onto substrates via templated electrodeposition and extend this technique through the use of a sacrificial overplating layer to achieve improved uniformity. Furthermore, we infiltrate the array with an organic phase change material and demonstrate the preservation of thermal properties. We use the 3ω method to measure the axial thermal conductivity of freestanding copper NW arrays to be as high as 70 W m(-1) K(-1), which is more than an order of magnitude larger than most commercial interface materials and enhanced-conductivity nanocomposites reported in the literature. These arrays are highly anisotropic, and the lateral thermal conductivity is found to be only 1-2 W m(-1) K(-1). We use these measured properties to elucidate the governing array-scale transport mechanisms, which include the effects of morphology and energy carrier scattering from size effects and grain boundaries.

"Hot spots" growth on single nanowire controlled by electric charge.

PubMed

Xi, Shaobo; Liu, Xuehua; He, Ting; Tian, Lei; Wang, Wenhui; Sun, Rui; He, Weina; Zhang, Xuetong; Zhang, Jinping; Ni, Weihai; Zhou, Xiaochun

2016-06-09

"Hot spots" - a kind of highly active site, which are usually composed of some unique units, such as defects, interfaces, catalyst particles or special structures - can determine the performance of nanomaterials. In this paper, we study a model system, i.e. "hot spots" on a single Ag nanowire in the galvanic replacement reaction (GRR), by dark-field microscopy. The research reveals that electric charge can be released by the formation reaction of AgCl, and consequently the electrochemical potential on Ag nanowire drops. The electric charge could induce the reduction of Ag(+) to form the "hot spots" on the nanowire during the GRR. The appearance probability of "hot spots" is almost even along the Ag nanowire, while it is slightly lower near the two ends. The spatial distance between adjacent "hot spots" is also controlled by the charge, and obeys a model based on Boltzmann distribution. In addition, the distance distribution here has an advantage in electron transfer and energy saving. Therefore, it's necessary to consider the functions of electric charge during the synthesis or application of nanomaterials.

Nonlinear Conductive Behaviour of Silver Nanowires/Silicone Rubber Composites

NASA Astrophysics Data System (ADS)

Lu, Pin; Qu, Zhaoming; Wang, Qingguo; Bai, Liyun; Zhao, Shiyang

2018-01-01

Silver nanowires with an average length of 10 μm and diameter of about 90 nm have been synthesized by polyol reduction of silver nitrate in the presence of polyvinylpyrrolidone(PVP). Silver nanowires (AgNWs)/silicone rubber (SR) composites have been made by mixing silver nanowires into silicone rubber. The nonlinear response of AgNWs/SR composites under high electric field is investigated. The nonlinear Conductive behavior of composites is considered as a competitive process of several effects. From the perspective of the microstructure of composites, the conductive path is established by the quantum tunnel effect between silver nanowires. The influence factors on the conductivity of composites are discussed and analyzed. The results show that the AgNWs/SR composites with nonlinear conductive properties are of great potential application in electromagnetic protection of electron device and system.

Construction of high-capacitance 3D CoO@polypyrrole nanowire array electrode for aqueous asymmetric supercapacitor.

PubMed

Zhou, Cheng; Zhang, Yangwei; Li, Yuanyuan; Liu, Jinping

2013-05-08

We have developed a supercapacitor electrode composed of well-aligned CoO nanowire array grown on 3D nickel foam with polypyrrole (PPy) uniformly immobilized onto or firmly anchored to each nanowire surface to boost the pseudocapacitive performance. The electrode architecture takes advantage of the high electrochemical activity from both the CoO and PPy, the high electronic conductivity of PPy, and the short ion diffusion pathway in ordered mesoporous nanowires. These merits together with the elegant synergy between CoO and PPy lead to a high specific capacitance of 2223 F g(-1) approaching the theoretical value, good rate capability, and cycling stability (99.8% capacitance retention after 2000 cycles). An aqueous asymmetric supercapacitor device with a maximum voltage of 1.8 V fabricated by using our hybrid array as the positive electrode and activated carbon film as the negative electrode has demonstrated high energy density (~43.5 Wh kg(-1)), high power density (~5500 W kg(-1) at 11.8 Wh kg(-1)) and outstanding cycleability (~20,000 times). After charging for only ~10 s, two such 4 cm(2) asymmetric supercapacitors connected in series can efficiently power 5 mm diameter red, yellow, and green round LED indicators (lasting for 1 h for red LED) and drive a mini 130 rotation-motor robustly.

Low-Cost Photolithographic Fabrication of Nanowires and Microfilters for Advanced Bioassay Devices

PubMed Central

Doan, Nhi M.; Qiang, Liangliang; Li, Zhe; Vaddiraju, Santhisagar; Bishop, Gregory W.; Rusling, James F.; Papadimitrakopoulos, Fotios

2015-01-01

Integrated microfluidic devices with nanosized array electrodes and microfiltration capabilities can greatly increase sensitivity and enhance automation in immunoassay devices. In this contribution, we utilize the edge-patterning method of thin aluminum (Al) films in order to form nano- to micron-sized gaps. Evaporation of high work-function metals (i.e., Au, Ag, etc.) on these gaps, followed by Al lift-off, enables the formation of electrical uniform nanowires from low-cost, plastic-based, photomasks. By replacing Al with chromium (Cr), the formation of high resolution, custom-made photomasks that are ideal for low-cost fabrication of a plurality of array devices were realized. To demonstrate the feasibility of such Cr photomasks, SU-8 micro-pillar masters were formed and replicated into PDMS to produce micron-sized filters with 3–4 µm gaps and an aspect ratio of 3. These microfilters were capable of retaining 6 µm beads within a localized site, while allowing solvent flow. The combination of nanowire arrays and micro-pillar filtration opens new perspectives for rapid R&D screening of various microfluidic-based immunoassay geometries, where analyte pre-concentration and highly sensitive, electrochemical detection can be readily co-localized. PMID:25774709

Characterizations of low-temperature electroluminescence from ZnO nanowire light-emitting arrays on the p-GaN layer.

PubMed

Lu, Tzu-Chun; Ke, Min-Yung; Yang, Sheng-Chieh; Cheng, Yun-Wei; Chen, Liang-Yi; Lin, Guan-Jhong; Lu, Yu-Hsin; He, Jr-Hau; Kuo, Hao-Chung; Huang, JianJang

2010-12-15

Low-temperature electroluminescence from ZnO nanowire light-emitting arrays is reported. By inserting a thin MgO current blocking layer in between ZnO nanowire and p-GaN, high-purity UV light emission at wavelength 398 nm was obtained. As the temperature is decreased, contrary to the typical GaN-based light emitting diodes, our device shows a decrease of optical output intensity. The results are associated with various carrier tunneling processes and frozen MgO defects.

Optimization of the short-circuit current in an InP nanowire array solar cell through opto-electronic modeling.

PubMed

Chen, Yang; Kivisaari, Pyry; Pistol, Mats-Erik; Anttu, Nicklas

2016-09-23

InP nanowire arrays with axial p-i-n junctions are promising devices for next-generation photovoltaics, with a demonstrated efficiency of 13.8%. However, the short-circuit current in such arrays does not match their absorption performance. Here, through combined optical and electrical modeling, we study how the absorption of photons and separation of the resulting photogenerated electron-hole pairs define and limit the short-circuit current in the nanowires. We identify how photogenerated minority carriers in the top n segment (i.e. holes) diffuse to the ohmic top contact where they recombine without contributing to the short-circuit current. In our modeling, such contact recombination can lead to a 60% drop in the short-circuit current. To hinder such hole diffusion, we include a gradient doping profile in the n segment to create a front surface barrier. This approach leads to a modest 5% increase in the short-circuit current, limited by Auger recombination with increased doping. A more efficient approach is to switch the n segment to a material with a higher band gap, like GaP. Then, a much smaller number of holes is photogenerated in the n segment, strongly limiting the amount that can diffuse and disappear into the top contact. For a 500 nm long top segment, the GaP approach leads to a 50% higher short-circuit current than with an InP top segment. Such a long top segment could facilitate the fabrication and contacting of nanowire array solar cells. Such design schemes for managing minority carriers could open the door to higher performance in single- and multi-junction nanowire-based solar cells.

Design and fabrication of Ni nanowires having periodically hollow nanostructures.

PubMed

Sada, Takao; Fujigaya, Tsuyohiko; Nakashima, Naotoshi

2014-10-07

We propose a concept for the design and fabrication of metal nanowires having periodically hollow nanostructures inside the pores of an anodic aluminum oxide (AAO) membrane using a sacrificial metal. In this study, nickel (Ni) and silver (Ag) were used as the base metal and the sacrificial metal, respectively. Alternating an applied potential between -0.4 and -1.0 V provided alternatively deposited Ni and Ag segments in a Ni-Ag 'barcode' nanowire with a diameter of 18 or 35 nm. After etching away the Ag segments, we fabricated Ni nanowires with nanopores of 12 ± 5.3 nm. Such nanostructure formation is explained by the formation of a Ni shell layer over the surface of the Ag segments due to the strong affinity of Ni(2+) for the interior surfaces of AAO. The Ni shell layer allows the Ni segments to remain even after dissolution of the Ag segments. Because the electroplating conditions can be easily controlled, we could carefully adjust the size and pitch of the periodically hollow nanospaces. We also describe a method for the fabrication of Ni nanorods by forming an Ag shell instead of a Ni shell on the Ni-Ag barcode nanowire, in which the interior of the AAO surfaces was modified with a compound bearing a thiol group prior to electroplating.

Synthesis, structural and optical properties of silver nanoparticles uniformly decorated ZnO nanowires

NASA Astrophysics Data System (ADS)

Zhang, Ke-Xin; Wen, Xing; Yao, Cheng-Bao; Li, Jin; Zhang, Meng; Li, Qiang-Hua; Sun, Wen-Jun; Wu, Jia-Da

2018-04-01

Silver (Ag) nanoparticles decorated Zinc oxide (A-ZnO) nanowires have been successfully synthesized by two-step chemical vapour deposition and magnetron sputtering method. The X-ray diffraction patterns revealed their hexagonal wurtzite structure. SEM images indicated the Ag nanoparticles are distributed uniformly on the surface of A-ZnO nanowires. By extending the sputtering time, the atomic percent of Ag increased gradually. Moreover, the photoluminescence results demonstrated two major emission peaks for the A-ZnO nanowires. Where, the visible emission peaks were stronger than those of unmodified ZnO nanowires. These studies promise their potential applications in multifunctional optical devices.

Ammonia sensing using arrays of silicon nanowires and graphene

NASA Astrophysics Data System (ADS)

Fobelets, K.; Panteli, C.; Sydoruk, O.; Li, Chuanbo

2018-06-01

Ammonia (NH3) is a toxic gas released in different industrial, agricultural and natural processes. It is also a biomarker for some diseases. These require NH3 sensors for health and safety reasons. To boost the sensitivity of solid-state sensors, the effective sensing area should be increased. Two methods are explored and compared using an evaporating pool of 0.5 mL NH4OH (28% NH3). In the first method an array of Si nanowires (Si NWA) is obtained via metal-assisted-electrochemical etching to increase the effective surface area. In the second method CVD graphene is suspended on top of the Si nanowires to act as a sensing layer. Both the effective surface area as well as the density of surface traps influences the amplitude of the response. The effective surface area of Si NWAs is 100 × larger than that of suspended graphene for the same top surface area, leading to a larger response in amplitude by a factor of ~7 notwithstanding a higher trap density in suspended graphene. The use of Si NWAs increases the response rate for both Si NWAs as well as the suspended graphene due to more effective NH3 diffusion processes.

Three-dimensional TiO2 nanowire@NiMoO4 ultrathin nanosheet core-shell arrays for lithium ion batteries

NASA Astrophysics Data System (ADS)

Cao, Minglei; Bu, Yi; Lv, Xiaowei; Jiang, Xingxing; Wang, Lichuan; Dai, Sirui; Wang, Mingkui; Shen, Yan

2018-03-01

This study reports a general and rational two-step hydrothermal strategy to fabricate three-dimensional (3D) TiO2 nanowire@NiMoO4 ultrathin nanosheet core-shell arrays (TNAs-NMO) as additives-free anodes for lithium-ion batteries (LIBs). The TNAs-NMO electrode delivers a reversible capacity of up to 446.6 mA h g-1 over 120 cycles at the current density of 0.2 A g-1 and a high rate capacity of 234.2 mA h g-1 at 2.0 A g-1. Impressively, the capacity retention efficiency is 74.7% after 2500 cycles at the high rate of 2.0 A g-1. In addition, the full cell consisting of TNAs-NMO anode and LCO cathode can afford a specific energy of up to 220.3 W h kg-1 (based on the entire mass of both electrodes). The high electrochemical performance of the TNAs-NMO electrode is ascribed to its 3D core-shell nanowire array architecture, in which the TiO2 nanowire arrays (TNAs) and the ultrathin NiMoO4 nanosheets exhibit strong synergistic effects. The TNAs maintain mechanical integrity of the electrode and the ultrathin NiMoO4 nanosheets contribute to high capacity and favorable electronic conductivity.

Tunable Nanowire Patterning Using Standing Surface Acoustic Waves

PubMed Central

Chen, Yuchao; Ding, Xiaoyun; Lin, Sz-Chin Steven; Yang, Shikuan; Huang, Po-Hsun; Nama, Nitesh; Zhao, Yanhui; Nawaz, Ahmad Ahsan; Guo, Feng; Wang, Wei; Gu, Yeyi; Mallouk, Thomas E.; Huang, Tony Jun

2014-01-01

Patterning of nanowires in a controllable, tunable manner is important for the fabrication of functional nanodevices. Here we present a simple approach for tunable nanowire patterning using standing surface acoustic waves (SSAW). This technique allows for the construction of large-scale nanowire arrays with well-controlled patterning geometry and spacing within 5 seconds. In this approach, SSAWs were generated by interdigital transducers (IDTs), which induced a periodic alternating current (AC) electric field on the piezoelectric substrate and consequently patterned metallic nanowires in suspension. The patterns could be deposited onto the substrate after the liquid evaporated. By controlling the distribution of the SSAW field, metallic nanowires were assembled into different patterns including parallel and perpendicular arrays. The spacing of the nanowire arrays could be tuned by controlling the frequency of the surface acoustic waves. Additionally, we observed 3D spark-shape nanowire patterns in the SSAW field. The SSAW-based nanowire-patterning technique presented here possesses several advantages over alternative patterning approaches, including high versatility, tunability, and efficiency, making it promising for device applications. PMID:23540330

Selective synthesis and characterization of single-crystal silver molybdate/tungstate nanowires by a hydrothermal process.

PubMed

Cui, Xianjin; Yu, Shu-Hong; Li, Lingling; Biao, Liu; Li, Huabin; Mo, Maosong; Liu, Xian-Ming

2004-01-05

Selective synthesis of uniform single crystalline silver molybdate/tungstate nanorods/nanowires in large scale can be easily realized by a facile hydrothermal recrystallization technique. The synthesis is strongly dependent on the pH conditions, temperature, and reaction time. The phase transformation was examined in details. Pure Ag(2)MoO(4) and Ag(6)Mo(10)O(33) can be easily obtained under neutral condition and pH 2, respectively, whereas other mixed phases of Mo(17)O(47), Ag(2)Mo(2)O(7,) Ag(6)Mo(10)O(33) were observed under different pH conditions. Ag(6)Mo(10)O(33) nanowires with uniform diameter 50-60 nm and length up to several hundred micrometers were synthesized in large scale for the first time at 140 degrees C. The melting point of Ag(6)Mo(10)O(33) nanowires were found to be about 238 degrees C. Similarly, Ag(2)WO(4), and Ag(2)W(2)O(7) nanorods/nanowires can be selectively synthesized by controlling pH value. The results demonstrated that this route could be a potential mild way to selectively synthesize various molybdate nanowires with various phases in large scale.

Polyaniline nanowire arrays aligned on nitrogen-doped carbon fabric for high-performance flexible supercapacitors.

PubMed

Yu, Pingping; Li, Yingzhi; Yu, Xinyi; Zhao, Xin; Wu, Lihao; Zhang, Qinghua

2013-09-24

A combination of vertical polyaniline (PANI) nanowire arrays and nitrogen plasma etched carbon fiber cloths (eCFC) was fabricated to create 3D nanostructured PANI/eCFC composites. The small size of the highly ordered PANI nanowires can greatly reduce the scale of the diffusion length, allowing for the improved utilization of electrode materials. A two-electrode flexible supercapacitor based on PANI/eCFC demonstrates a high specific capacitance (1035 F g(-1) at a current density of 1 A g(-1)), good rate capability (88% capacity retention at 8 A g(-1)), and long-term cycle life (10% capacity loss after 5000 cycles). The lightweight, low-cost, flexible composites are promising candidates for use in energy storage device applications.

Ag nanoparticles-decorated ZnO nanorod array on a mechanical flexible substrate with enhanced optical and antimicrobial properties

NASA Astrophysics Data System (ADS)

Chen, Yi; Tse, Wai Hei; Chen, Longyan; Zhang, Jin

2015-03-01

Heteronanostructured zinc oxide nanorod (ZnO NR) array are vertically grown on polydimethylsiloxane (PDMS) through a hydrothermal method followed by an in situ deposition of silver nanoparticles (Ag NPs) through a photoreduction process. The Ag-ZnO heterostructured nanorods on PDMS are measured with an average diameter of 160 nm and an average length of 2 μm. ZnO NRs measured by high-resolution transmission electron microscope (HRTEM) shows highly crystalline with a lattice fringe of 0.255 nm, which corresponds to the (0002) planes in ZnO crystal lattice. The average diameter of the Ag NPs in situ deposited on the ZnO NRs is estimated at 22 ± 2 nm. As compared to the bare ZnO NRs, the heterostructured Ag-ZnO nanorod array shows enhanced ultraviolet (UV) absorption at 440 nm, and significant emission in the visible region (λem = 542 nm). In addition, the antimicrobial efficiency of Ag-ZnO heterostructured nanorod array shows obvious improvement as compared to bare ZnO nanorod array. The cytotoxicity of ZnO nanorod array with and without Ag NPs was studied by using 3 T3 mouse fibroblast cell line. No significant toxic effect is imposed on the cells.

Ag nanoparticles-decorated ZnO nanorod array on a mechanical flexible substrate with enhanced optical and antimicrobial properties.

PubMed

Chen, Yi; Tse, Wai Hei; Chen, Longyan; Zhang, Jin

2015-01-01

Heteronanostructured zinc oxide nanorod (ZnO NR) array are vertically grown on polydimethylsiloxane (PDMS) through a hydrothermal method followed by an in situ deposition of silver nanoparticles (Ag NPs) through a photoreduction process. The Ag-ZnO heterostructured nanorods on PDMS are measured with an average diameter of 160 nm and an average length of 2 μm. ZnO NRs measured by high-resolution transmission electron microscope (HRTEM) shows highly crystalline with a lattice fringe of 0.255 nm, which corresponds to the (0002) planes in ZnO crystal lattice. The average diameter of the Ag NPs in situ deposited on the ZnO NRs is estimated at 22 ± 2 nm. As compared to the bare ZnO NRs, the heterostructured Ag-ZnO nanorod array shows enhanced ultraviolet (UV) absorption at 440 nm, and significant emission in the visible region (λem = 542 nm). In addition, the antimicrobial efficiency of Ag-ZnO heterostructured nanorod array shows obvious improvement as compared to bare ZnO nanorod array. The cytotoxicity of ZnO nanorod array with and without Ag NPs was studied by using 3 T3 mouse fibroblast cell line. No significant toxic effect is imposed on the cells.

Tungsten oxide@polypyrrole core-shell nanowire arrays as novel negative electrodes for asymmetric supercapacitors.

PubMed

Wang, Fengmei; Zhan, Xueying; Cheng, Zhongzhou; Wang, Zhenxing; Wang, Qisheng; Xu, Kai; Safdar, Muhammad; He, Jun

2015-02-11

Among active pseudocapacitive materials, polypyrrole (PPy) is a promising electrode material in electrochemical capacitors. PPy-based materials research has thus far focused on its electrochemical performance as a positive electrode rather than as a negative electrode for asymmetric supercapacitors (ASCs). Here high-performance electrochemical supercapacitors are designed with tungsten oxide@PPy (WO3 @PPy) core-shell nanowire arrays and Co(OH)2 nanowires grown on carbon fibers. The WO3 @PPy core-shell nanowire electrode exhibits a high capacitance (253 mF/cm2) in negative potentials (-1.0-0.0 V). The ASCs packaged with CF-Co(OH)2 as a positive electrode and CF-WO3 @PPy as a negative electrode display a high volumetric capacitance up to 2.865 F/cm3 based on volume of the device, an energy density of 1.02 mWh/cm3 , and very good stability performance. These findings promote the application of PPy-based nanostructures as advanced negative electrodes for ASCs. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Catalyst-free, III-V nanowire photovoltaics

NASA Astrophysics Data System (ADS)

Davies, D. G.; Lambert, N.; Fry, P. W.; Foster, A.; Krysa, A. B.; Wilson, L. R.

2014-05-01

We report on room temperature, photovoltaic operation of catalyst-free GaAs p-i-n junction nanowire arrays. Growth studies were first performed to determine the optimum conditions for controlling the vertical and lateral growth of the nanowires. Following this, devices consisting of axial p-i-n junctions were fabricated by planarising the nanowire arrays with a hard baked polymer. We discuss the photovoltaic properties of this proof-of-concept device, and significant improvements to be made during the growth.

Ag-NP@Ge-nanotaper/Si-micropillar ordered arrays as ultrasensitive and uniform surface enhanced Raman scattering substrates

NASA Astrophysics Data System (ADS)

Liu, Jing; Meng, Guowen; Li, Zhongbo; Huang, Zhulin; Li, Xiangdong

2015-10-01

Surface-enhanced Raman scattering (SERS) is considered to be an excellent candidate for analytical detection schemes, because of its molecular specificity, rapid response and high sensitivity. Here, SERS-substrates of Ag-nanoparticle (Ag-NP) decorated Ge-nanotapers grafted on hexagonally ordered Si-micropillar (denoted as Ag-NP@Ge-nanotaper/Si-micropillar) arrays are fabricated via a combinatorial process of two-step etching to achieve hexagonal Si-micropillar arrays, chemical vapor deposition of flocky Ge-nanotapers on each Si-micropillar and decoration of Ag-NPs onto the Ge-nanotapers through galvanic displacement. With high density three-dimensional (3D) ``hot spots'' created from the large quantities of the neighboring Ag-NPs and large-scale uniform morphology, the hierarchical Ag-NP@Ge-nanotaper/Si-micropillar arrays exhibit strong and reproducible SERS activity. Using our hierarchical 3D SERS-substrates, both methyl parathion (a commonly used pesticide) and PCB-2 (one congener of highly toxic polychlorinated biphenyls) with concentrations down to 10-7 M and 10-5 M have been detected respectively, showing great potential in SERS-based rapid trace-level detection of toxic organic pollutants in the environment.Surface-enhanced Raman scattering (SERS) is considered to be an excellent candidate for analytical detection schemes, because of its molecular specificity, rapid response and high sensitivity. Here, SERS-substrates of Ag-nanoparticle (Ag-NP) decorated Ge-nanotapers grafted on hexagonally ordered Si-micropillar (denoted as Ag-NP@Ge-nanotaper/Si-micropillar) arrays are fabricated via a combinatorial process of two-step etching to achieve hexagonal Si-micropillar arrays, chemical vapor deposition of flocky Ge-nanotapers on each Si-micropillar and decoration of Ag-NPs onto the Ge-nanotapers through galvanic displacement. With high density three-dimensional (3D) ``hot spots'' created from the large quantities of the neighboring Ag-NPs and large-scale uniform

3D ZnIn2S4 nanosheet/TiO2 nanowire arrays and their efficient photocathodic protection for 304 stainless steel

NASA Astrophysics Data System (ADS)

Sun, Wenxia; Wei, Na; Cui, Hongzhi; Lin, Yuan; Wang, Xinzhen; Tian, Jian; Li, Jian; Wen, Jing

2018-03-01

A well-designed heterostructure engineered ZnIn2S4 nanosheet/TiO2 nanowire arrays photoanode is investigated for photocathodic protection. The ZnIn2S4 nanosheets are distributed uniformly on the surface of the TiO2 nanowire by a hydrothermal method. The stem-and-leaf-like ZnIn2S4 nanosheet/TiO2 nanowire arrays exhibit excellent photoelectrochemical properties, owing to the energy band structure and large surface area. A maximum photocurrent density of 2 mA cm-2 is achieved for the ZnIn2S4 nanosheet/TiO2 nanowire composite film for a 6 h reaction time under white illumination. Moreover, the potential of the 304 stainless steel coupled with the composite film immediately shifts negatively to -1.17 V (vs. SCE), which is significantly lower than the corrosion potential (-0.201 V vs. SCE). Thus, the composite film offers a superior photocathodic protection for stainless steel against corrosion by a NaCl solution. This study provides a promising approach for the design and synthesis of composite films with enhanced photoelectrochemical performance.

Structure and properties of nanostructured ZnO arrays and ZnO/Ag nanocomposites fabricated by pulsed electrodeposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kopach, V. R.; Klepikova, K. S.; Klochko, N. P., E-mail: klochko-np@mail.ru

We investigate the structure, surface morphology, and optical properties of nanostructured ZnO arrays fabricated by pulsed electrodeposition, Ag nanoparticles precipitated from colloidal solutions, and a ZnO/Ag nanocomposite based on them. The electronic and electrical parameters of the ZnO arrays and ZnO/Ag nanocomposites are analyzed by studying the I–V and C–V characteristics. Optimal modes for fabricating the ZnO/Ag heterostructures with the high stability and sensitivity to ultraviolet radiation as promising materials for use in photodetectors, gas sensors, and photocatalysts are determined.

Pressure-sensitive strain sensor based on a single percolated Ag nanowire layer embedded in colorless polyimide

NASA Astrophysics Data System (ADS)

Lee, Chan-Jae; Jun, Sungwoo; Ju, Byeong-Kwon; Kim, Jong-Woong

2017-06-01

This paper presents the fabrication of an elastomer-free, transparent, pressure-sensitive strain sensor consisting of a specially designed silver nanowire (AgNW) pattern and colorless polyimide (cPI). A percolated AgNW network was patterned with a simple tandem compound circuit, which was then embedded in the surface of the cPI via inverted layer processing. The resulting film-type sensor was highly transparent ( 93.5% transmittance at 550 nm) and mechanically stable (capable of resisting 10000 cycles of bending to a 500 μm radius of curvature). We demonstrated that a thin, transparent, and mechanically stable electrode can be produced using a combination of AgNWs and cPI, and used to produce a system sensitive to pressure-induced bending. The capacitance of the AgNW tandem compound electrode pattern grew via fringing, which increased with the pressure-induced bending applied to the surface of the sensor. The sensitivity was four times higher than that of an elastomeric pressure sensor made with the same design. Finally, we demonstrated a skin-like pressure sensor attached to the inside wrist of a human arm.

High carrier concentration ZnO nanowire arrays for binder-free conductive support of supercapacitors electrodes by Al doping.

PubMed

Zheng, Xin; Sun, Yihui; Yan, Xiaoqin; Sun, Xu; Zhang, Guangjie; Zhang, Qian; Jiang, Yaru; Gao, Wenchao; Zhang, Yue

2016-12-15

Doping semiconductor nanowires (NWs) for altering their electrical and optical properties is a critical strategy for tailoring the performance of nanodevices. Here, we prepared in situ Al-doped ZnO nanowire arrays by using continuous flow injection (CFI) hydrothermal method to promote the conductivity. This reasonable method offers highly stable precursor concentration for doping that effectively avoid the appearance of the low conductivity ZnO nanosheets. Benefit from this, three orders of magnitude rise of the carrier concentration from 10 16 cm -3 to 10 19 cm -3 can be achieved compared with the common hydrothermal (CH) mothed in Mott-Schottky measurement. Possible effect of Al-doping was discussed by first-principle theory. On this basis, Al-doped ZnO nanowire arrays was developed as a binder-free conductive support for supercapacitor electrodes and high capacitance was triggered. It is owing to the dramatically decreased transfer resistance induced by the growing free-moving electrons and holes. Our results have a profound significance not merely in the controlled synthesis of other doping nanomaterials by co-precipitation method but also in the application of binder-free energy materials or other materials. Copyright © 2016 Elsevier Inc. All rights reserved.

A Two-Dimensional Ruddlesden-Popper Perovskite Nanowire Laser Array based on Ultrafast Light-Harvesting Quantum Wells.

PubMed

Zhang, Haihua; Wu, Yishi; Liao, Qing; Zhang, Zhaoyi; Liu, Yanping; Gao, Qinggang; Liu, Peng; Li, Meili; Yao, Jiannian; Fu, Hongbing

2018-06-25

Miniaturized nanowire nanolasers of 3D perovskites feature a high gain coefficient; however, room-temperature optical gain and nanowire lasers from 2D layered perovskites have not been reported to date. A biomimetic approach is presented to construct an artificial ligh-harvesting system in mixed multiple quantum wells (QWs) of 2D-RPPs of (BA) 2 (FA) n-1 Pb n Br 3n+1 , achieving room-temperature ASE and nanowire (NW) lasing. Owing to the improvement of flexible and deformable characteristics provided by organic BA cation layers, high-density large-area NW laser arrays were fabricated with high photostability. Well-controlled dimensions and uniform geometries enabled 2D-RPPs NWs functioning as high-quality Fabry-Perot (FP) lasers with almost identical optical modes, high quality (Q) factor (ca. 1800), and similarly low lasing thresholds. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

In situ TEM observation of heterogeneous phase transition of a constrained single-crystalline Ag2Te nanowire.

PubMed

In, Juneho; Yoo, Youngdong; Kim, Jin-Gyu; Seo, Kwanyong; Kim, Hyunju; Ihee, Hyotchel; Oh, Sang Ho; Kim, Bongsoo

2010-11-10

Laterally epitaxial single crystalline Ag2Te nanowires (NWs) are synthesized on sapphire substrates by the vapor transport method. We observed the phase transitions of these Ag2Te NWs via in situ transmission electron microscopy (TEM) after covering them with Pt layers. The constrained NW shows phase transition from monoclinic to a body-centered cubic (bcc) structure near the interfaces, which is ascribed to the thermal stress caused by differences in the thermal expansion coefficients. Furthermore, we observed the nucleation and growth of bcc phase penetrating into the face-centered cubic matrix at 200 °C by high-resolution TEM in real time. Our results would provide valuable insight into how compressive stresses imposed by overlayers affect behaviors of nanodevices.

Facile Synthesis of Vanadium-Doped Ni3S2 Nanowire Arrays as Active Electrocatalyst for Hydrogen Evolution Reaction.

PubMed

Qu, Yuanju; Yang, Mingyang; Chai, Jianwei; Tang, Zhe; Shao, Mengmeng; Kwok, Chi Tat; Yang, Ming; Wang, Zhenyu; Chua, Daniel; Wang, Shijie; Lu, Zhouguang; Pan, Hui

2017-02-22

Ni 3 S 2 nanowire arrays doped with vanadium(V) are directly grown on nickel foam by a facile one-step hydrothermal method. It is found that the doping can promote the formation of Ni 3 S 2 nanowires at a low temperature. The doped nanowires show excellent electrocatalytic performance toward hydrogen evolution reaction (HER), and outperform pure Ni 3 S 2 and other Ni 3 S 2 -based compounds. The stability test shows that the performance of V-doped Ni 3 S 2 nanowires is improved and stabilized after thousands of linear sweep voltammetry test. The onset potential of V-doped Ni 3 S 2 nanowire can be as low as 39 mV, which is comparable to platinum. The nanowire has an overpotential of 68 mV at 10 mA cm -2 , a relatively low Tafel slope of 112 mV dec -1 , good stability and high Faradaic efficiency. First-principles calculations show that the V-doping in Ni 3 S 2 extremely enhances the free carrier density near the Fermi level, resulting in much improved catalytic activities. We expect that the doping can be an effective way to enhance the catalytic performance of metal disulfides in hydrogen evolution reaction and V-doped Ni 3 S 2 nanowire is one of the most promising electrocatalysts for hydrogen production.

Monolithic Integration of a Silicon Nanowire Field-Effect Transistors Array on a Complementary Metal-Oxide Semiconductor Chip for Biochemical Sensor Applications

PubMed Central

Livi, Paolo; Kwiat, Moria; Shadmani, Amir; Pevzner, Alexander; Navarra, Giulio; Rothe, Jörg; Stettler, Alexander; Chen, Yihui; Patolsky, Fernando; Hierlemann, Andreas

2017-01-01

We present a monolithic complementary metal-oxide semiconductor (CMOS)-based sensor system comprising an array of silicon nanowire field-effect transistors (FETs) and the signal-conditioning circuitry on the same chip. The silicon nanowires were fabricated by chemical vapor deposition methods and then transferred to the CMOS chip, where Ti/Pd/Ti contacts had been patterned via e-beam lithography. The on-chip circuitry measures the current flowing through each nanowire FET upon applying a constant source-drain voltage. The analog signal is digitized on chip and then transmitted to a receiving unit. The system has been successfully fabricated and tested by acquiring I−V curves of the bare nanowire-based FETs. Furthermore, the sensing capabilities of the complete system have been demonstrated by recording current changes upon nanowire exposure to solutions of different pHs, as well as by detecting different concentrations of Troponin T biomarkers (cTnT) through antibody-functionalized nanowire FETs. PMID:26348408

Monolithic integration of a silicon nanowire field-effect transistors array on a complementary metal-oxide semiconductor chip for biochemical sensor applications.

PubMed

Livi, Paolo; Kwiat, Moria; Shadmani, Amir; Pevzner, Alexander; Navarra, Giulio; Rothe, Jörg; Stettler, Alexander; Chen, Yihui; Patolsky, Fernando; Hierlemann, Andreas

2015-10-06

We present a monolithic complementary metal-oxide semiconductor (CMOS)-based sensor system comprising an array of silicon nanowire field-effect transistors (FETs) and the signal-conditioning circuitry on the same chip. The silicon nanowires were fabricated by chemical vapor deposition methods and then transferred to the CMOS chip, where Ti/Pd/Ti contacts had been patterned via e-beam lithography. The on-chip circuitry measures the current flowing through each nanowire FET upon applying a constant source-drain voltage. The analog signal is digitized on chip and then transmitted to a receiving unit. The system has been successfully fabricated and tested by acquiring I-V curves of the bare nanowire-based FETs. Furthermore, the sensing capabilities of the complete system have been demonstrated by recording current changes upon nanowire exposure to solutions of different pHs, as well as by detecting different concentrations of Troponin T biomarkers (cTnT) through antibody-functionalized nanowire FETs.

Non-destructive detection of cross-sectional strain and defect structure in an individual Ag five-fold twinned nanowire by 3D electron diffraction mapping.

PubMed

Fu, Xin; Yuan, Jun

2017-07-24

Coherent x-ray diffraction investigations on Ag five-fold twinned nanowires (FTNWs) have drawn controversial conclusions concerning whether the intrinsic 7.35° angular gap could be compensated homogeneously through phase transformation or inhomogeneously by forming disclination strain field. In those studies, the x-ray techniques only provided an ensemble average of the structural information from all the Ag nanowires. Here, using three-dimensional (3D) electron diffraction mapping approach, we non-destructively explore the cross-sectional strain and the related strain-relief defect structures of an individual Ag FTNW with diameter about 30 nm. The quantitative analysis of the fine structure of intensity distribution combining with kinematic electron diffraction simulation confirms that for such a Ag FTNW, the intrinsic 7.35° angular deficiency results in an inhomogeneous strain field within each single crystalline segment consistent with the disclination model of stress-relief. Moreover, the five crystalline segments are found to be strained differently. Modeling analysis in combination with system energy calculation further indicates that the elastic strain energy within some crystalline segments, could be partially relieved by the creation of stacking fault layers near the twin boundaries. Our study demonstrates that 3D electron diffraction mapping is a powerful tool for the cross-sectional strain analysis of complex 1D nanostructures.

1-Dimensional AgVO3 nanowires hybrid with 2-dimensional graphene nanosheets to create 3-dimensional composite aerogels and their improved electrochemical properties

NASA Astrophysics Data System (ADS)

Liang, Liying; Xu, Yimeng; Lei, Yong; Liu, Haimei

2014-03-01

Three-dimensional (3D) porous composite aerogels have been synthesized via an innovative in situ hydrothermal method assisted by a freeze-drying process. In this hybrid structure, one-dimensional (1D) AgVO3 nanowires are uniformly dispersed on two-dimensional (2D) graphene nanosheet surfaces and/or are penetrated through the graphene sheets, forming 3D porous composite aerogels. As cathode materials for lithium-ion batteries, the composite aerogels exhibit high discharge capacity, excellent rate capability, and good cycling stability.Three-dimensional (3D) porous composite aerogels have been synthesized via an innovative in situ hydrothermal method assisted by a freeze-drying process. In this hybrid structure, one-dimensional (1D) AgVO3 nanowires are uniformly dispersed on two-dimensional (2D) graphene nanosheet surfaces and/or are penetrated through the graphene sheets, forming 3D porous composite aerogels. As cathode materials for lithium-ion batteries, the composite aerogels exhibit high discharge capacity, excellent rate capability, and good cycling stability. Electronic supplementary information (ESI) available: Preparation, characterization, SEM images, XRD patterns, and XPS of AgVO3/GAs. See DOI: 10.1039/c3nr06899d

Solution-Processed Ag Nanowires + PEDOT:PSS Hybrid Electrode for Cu(In,Ga)Se₂ Thin-Film Solar Cells.

PubMed

Shin, Donghyeop; Kim, Taegeon; Ahn, Byung Tae; Han, Seung Min

2015-06-24

To reduce the cost of the Cu(In,Ga)Se2 (CIGS) solar cells while maximizing the efficiency, we report the use of an Ag nanowires (NWs) + poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PSS) hybrid transparent electrode, which was deposited using all-solution-processed, low-cost, scalable methods. This is the first demonstration of an Ag NWs + PSS transparent electrode applied to CIGS solar cells. The spin-coated 10-nm-thick PSS conducting polymer layer in our hybrid electrode functioned as a filler of empty space of an electrostatically sprayed Ag NW network. Coating of PSS on the Ag NW network resulted in an increase in the short-circuit current from 15.4 to 26.5 mA/cm(2), but the open-circuit voltage and shunt resistance still needed to be improved. The limited open-circuit voltage was found to be due to interfacial recombination that is due to the ineffective hole-blocking ability of the CdS film. To suppress the interfacial recombination between Ag NWs and the CdS film, a Zn(S,O,OH) film was introduced as a hole-blocking layer between the CdS film and Ag NW network. The open-circuit voltage of the cell sharply improved from 0.35 to 0.6 V, which resulted in the best cell efficiency of 11.6%.

Spontaneous and Selective Nanowelding of Silver Nanowires by Electrochemical Ostwald Ripening and High Electrostatic Potential at the Junctions for High-Performance Stretchable Transparent Electrodes.

PubMed

Lee, Hyo-Ju; Oh, Semi; Cho, Ki-Yeop; Jeong, Woo-Lim; Lee, Dong-Seon; Park, Seong-Ju

2018-04-25

Metal nanowires have been gaining increasing attention as the most promising stretchable transparent electrodes for emerging field of stretchable optoelectronic devices. Nanowelding technology is a major challenge in the fabrication of metal nanowire networks because the optoelectronic performances of metal nanowire networks are mostly limited by the high junction resistance between nanowires. We demonstrate the spontaneous and selective welding of Ag nanowires (AgNWs) by Ag solders via an electrochemical Ostwald ripening process and high electrostatic potential at the junctions of AgNWs. The AgNWs were welded by depositing Ag nanoparticles (AgNPs) on the conducting substrate and then exposing them to water at room temperature. The AgNPs were spontaneously dissolved in water to form Ag + ions, which were then reduced to single-crystal Ag solders selectively at the junctions of the AgNWs. Hence, the welded AgNWs showed higher optoelectronic and stretchable performance compared to that of as-formed AgNWs. These results indicate that electrochemical Ostwald ripening-based welding can be used as a promising method for high-performance metal nanowire electrodes in various next-generation devices such as stretchable solar cells, stretchable displays, organic light-emitting diodes, and skin sensors.

Measuring and Modeling the Growth Dynamics of Self-Catalyzed GaP Nanowire Arrays.

PubMed

Oehler, Fabrice; Cattoni, Andrea; Scaccabarozzi, Andrea; Patriarche, Gilles; Glas, Frank; Harmand, Jean-Christophe

2018-02-14

The bottom-up fabrication of regular nanowire (NW) arrays on a masked substrate is technologically relevant, but the growth dynamic is rather complex due to the superposition of severe shadowing effects that vary with array pitch, NW diameter, NW height, and growth duration. By inserting GaAsP marker layers at a regular time interval during the growth of a self-catalyzed GaP NW array, we are able to retrieve precisely the time evolution of the diameter and height of a single NW. We then propose a simple numerical scheme which fully computes shadowing effects at play in infinite arrays of NWs. By confronting the simulated and experimental results, we infer that re-emission of Ga from the mask is necessary to sustain the NW growth while Ga migration on the mask must be negligible. When compared to random cosine or random uniform re-emission from the mask, the simple case of specular reflection on the mask gives the most accurate account of the Ga balance during the growth.

Ag-NP@Ge-nanotaper/Si-micropillar ordered arrays as ultrasensitive and uniform surface enhanced Raman scattering substrates.

PubMed

Liu, Jing; Meng, Guowen; Li, Zhongbo; Huang, Zhulin; Li, Xiangdong

2015-11-21

Surface-enhanced Raman scattering (SERS) is considered to be an excellent candidate for analytical detection schemes, because of its molecular specificity, rapid response and high sensitivity. Here, SERS-substrates of Ag-nanoparticle (Ag-NP) decorated Ge-nanotapers grafted on hexagonally ordered Si-micropillar (denoted as Ag-NP@Ge-nanotaper/Si-micropillar) arrays are fabricated via a combinatorial process of two-step etching to achieve hexagonal Si-micropillar arrays, chemical vapor deposition of flocky Ge-nanotapers on each Si-micropillar and decoration of Ag-NPs onto the Ge-nanotapers through galvanic displacement. With high density three-dimensional (3D) "hot spots" created from the large quantities of the neighboring Ag-NPs and large-scale uniform morphology, the hierarchical Ag-NP@Ge-nanotaper/Si-micropillar arrays exhibit strong and reproducible SERS activity. Using our hierarchical 3D SERS-substrates, both methyl parathion (a commonly used pesticide) and PCB-2 (one congener of highly toxic polychlorinated biphenyls) with concentrations down to 10(-7) M and 10(-5) M have been detected respectively, showing great potential in SERS-based rapid trace-level detection of toxic organic pollutants in the environment.

Roll-to-roll slot-die coating of 400 mm wide, flexible, transparent Ag nanowire films for flexible touch screen panels.

PubMed

Kim, Dong-Ju; Shin, Hae-In; Ko, Eun-Hye; Kim, Ki-Hyun; Kim, Tae-Woong; Kim, Han-Ki

2016-09-28

We report fabrication of large area Ag nanowire (NW) film coated using a continuous roll-to-roll (RTR) slot die coater as a viable alternative to conventional ITO electrodes for cost-effective and large-area flexible touch screen panels (TSPs). By controlling the flow rate of shear-thinning Ag NW ink in the slot die, we fabricated Ag NW percolating network films with different sheet resistances (30-70 Ohm/square), optical transmittance values (89-90%), and haze (0.5-1%) percentages. Outer/inner bending, twisting, and rolling tests as well as dynamic fatigue tests demonstrated that the mechanical flexibility of the slot-die coated Ag NW films was superior to that of conventional ITO films. Using diamond-shape patterned Ag NW layer electrodes (50 Ohm/square, 90% optical transmittance), we fabricated 12-inch flexible film-film type and rigid glass-film-film type TSPs. Successful operation of flexible TSPs with Ag NW electrodes indicates that slot-die-coated large-area Ag NW films are promising low cost, high performance, and flexible transparent electrodes for cost-effective large-area flexible TSPs and can be substituted for ITO films, which have high sheet resistance and are brittle.

Roll-to-roll slot-die coating of 400 mm wide, flexible, transparent Ag nanowire films for flexible touch screen panels

NASA Astrophysics Data System (ADS)

Kim, Dong-Ju; Shin, Hae-In; Ko, Eun-Hye; Kim, Ki-Hyun; Kim, Tae-Woong; Kim, Han-Ki

2016-09-01

We report fabrication of large area Ag nanowire (NW) film coated using a continuous roll-to-roll (RTR) slot die coater as a viable alternative to conventional ITO electrodes for cost-effective and large-area flexible touch screen panels (TSPs). By controlling the flow rate of shear-thinning Ag NW ink in the slot die, we fabricated Ag NW percolating network films with different sheet resistances (30-70 Ohm/square), optical transmittance values (89-90%), and haze (0.5-1%) percentages. Outer/inner bending, twisting, and rolling tests as well as dynamic fatigue tests demonstrated that the mechanical flexibility of the slot-die coated Ag NW films was superior to that of conventional ITO films. Using diamond-shape patterned Ag NW layer electrodes (50 Ohm/square, 90% optical transmittance), we fabricated 12-inch flexible film-film type and rigid glass-film-film type TSPs. Successful operation of flexible TSPs with Ag NW electrodes indicates that slot-die-coated large-area Ag NW films are promising low cost, high performance, and flexible transparent electrodes for cost-effective large-area flexible TSPs and can be substituted for ITO films, which have high sheet resistance and are brittle.

Ag nanoparticle-filled TiO2 nanotube arrays prepared by anodization and electrophoretic deposition for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Wei, Xing; Sugri Nbelayim, Pascal; Kawamura, Go; Muto, Hiroyuki; Matsuda, Atsunori

2017-03-01

A layer of TiO2 nanotube (TNT) arrays with a thickness of 13 μm is synthesized by a two-step anodic oxidation from Ti metal foil. Surface charged Ag nanoparticles (NPs) are prepared by chemical reduction. After a pretreatment of the TNT arrays by acetone vapor, Ag NP filled TNT arrays can be achieved by electrophoretic deposition (EPD). Effects of the applied voltage during EPD such as DC-AC difference, frequency and waveform are investigated by quantitative analysis using atomic absorption spectroscopy. The results show that the best EPD condition is using DC 2 V + AC 4 V and a square wave of 1 Hz as the applied voltage. Back illuminated dye-sensitized solar cells are fabricated from TNT arrays with and without Ag NPs. The efficiency increased from 3.70% to 5.01% by the deposition of Ag NPs.

Effect of Crossing Geometry on the Plasmonic Behavior of Dielectric Core/Metal Sheath Nanowires

DTIC Science & Technology

2009-03-01

uniform SERS substrate. The growth of the Ga2O3 nanowires was achieved by the controlled oxidation of pure Ga metal in a vacuum tube furnace.14 The...equations.15 We have previously shown that Ga2O3 /Ag nanowire composites can be very efficient SERS substrates,11,12 and we suggested that the nanowire...detail, we used these Au lithographically produced lines, combined with the placement of individual Ga2O3 /Ag nanowires in specific crossing angles

Performance of ethanol electro-oxidation on Ni-Cu alloy nanowires through composition modulation.

PubMed

Tian, Xi-Ke; Zhao, Xiao-Yu; Zhang, Li-de; Yang, Chao; Pi, Zhen-Bang; Zhang, Su-Xin

2008-05-28

To reduce the cost of the catalyst for direct ethanol fuel cells and improve its catalytic activity, highly ordered Ni-Cu alloy nanowire arrays have been fabricated successfully by differential pulse current electro-deposition into the pores of a porous anodic alumina membrane (AAMs). The energy dispersion spectrum, scanning and transmission electron microscopy were utilized to characterize the composition and morphology of the Ni-Cu alloy nanowire arrays. The results reveal that the nanowires in the array are uniform, well isolated and parallel to each other. The catalytic activity of the nanowire electrode arrays for ethanol oxidation was tested and the binary alloy nanowire array possesses good catalytic activity for the electro-oxidation of ethanol. The performance of ethanol electro-oxidation was controlled by varying the Cu content in the Ni-Cu alloy and the Ni-Cu alloy nanowire electrode shows much better stability than the pure Ni one.

The fabrication of Ag nanoflake arrays via self-assembly on the surface of an anodic aluminum oxide template

NASA Astrophysics Data System (ADS)

Li, Xueming; Dong, Kun; Tang, Libin; Wu, Yongjun; Yang, Peizhi; Zhang, Pengxiang

2010-02-01

Vertical-aligned Ag nanoflake arrays are fabricated on the surface of an anodic aluminum oxide (AAO) template under a hydrothermal condition for the first time. The porous surface of AAO templates and the precursor solution may play key roles in the process of fabricating Ag nanoflakes. The rim of pores can provide many active sites for nucleation and growth, and then nanoflake arrays gradually form through self-assembly of Ag on the surface of AAO membranes. The product is characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and a growth mechanism of nanoflake is deduced. This work demonstrates that it is possible to make ordered nanoarrays without dissolving templates using the hydrothermal method, and this interesting Ag nanoflake arrays may provide a wider range of nanoscale applications.

Electrostatic spray deposition of highly transparent silver nanowire electrode on flexible substrate.

PubMed

Kim, Taegeon; Canlier, Ali; Kim, Geun Hong; Choi, Jaeho; Park, Minkyu; Han, Seung Min

2013-02-01

In this work, a modified polyol synthesis by adding KBr and by replacing the AgCl with NaCl seed was used to obtain high quality silver nanowires with long aspect ratios with an average length of 13.5 μm in length and 62.5 nm in diameter. The Ag nanowires suspended in methanol solution after removing any unwanted particles using a glass filter system were then deposited on a flexible polycarbonate substrate using an electrostatic spray system. Transmittance of 92.1% at wavelength of 550 nm with sheet resistance of 20 Ω/sq and haze of 4.9% were measured for the electrostatic sprayed Ag nanowire transparent electrode.

Developing high coercivity in large diameter cobalt nanowire arrays

NASA Astrophysics Data System (ADS)

Montazer, A. H.; Ramazani, A.; Almasi Kashi, M.; Zavašnik, J.

2016-11-01

Regardless of the synthetic method, developing high magnetic coercivity in ferromagnetic nanowires (NWs) with large diameters has been a challenge over the past two decades. Here, we report on the synthesis of highly coercive cobalt NW arrays with diameters of 65 and 80 nm, which are embedded in porous anodic alumina templates with high-aspect-ratio pores. Using a modified electrochemical deposition method enabled us to reach room temperature coercivity and remanent ratio up to 3000 Oe and 0.70, respectively, for highly crystalline as-synthesized hcp cobalt NW arrays with a length of 8 μm. The first-order reversal curve (FORC) analysis showed the presence of both soft and hard magnetic phases along the length of the resulting NWs. To develop higher coercive fields, the length of the NWs was then gradually reduced in order from bottom to top, thereby reaching NW sections governed by the hard phase. Consequently, this resulted in record high coercivities of 4200 and 3850 Oe at NW diameters of 65 and 80 nm, respectively. In this case, the FORC diagrams confirmed a significant reduction in interactions between the magnetic phases of the remaining sections of NWs. At this stage, x-ray diffraction (XRD) and dark-field transmission electron microscopy analyses indicated the formation of highly crystalline bamboo-like sections along the [0 0 2] direction during a progressive pulse-controlled electrochemical growth of NW arrays under optimized parameters. Our results both provide new insights into the growth process, crystalline characteristics and magnetic phases along the length of large diameter NW arrays and, furthermore, develop the performance of pure 3d transition magnetic NWs.

Defect-induced infrared electroluminescence from radial GaInP/AlGaInP quantum well nanowire array light- emitting diodes

NASA Astrophysics Data System (ADS)

Hussain, Laiq; Karimi, Mohammad; Berg, Alexander; Jain, Vishal; Borgström, Magnus T.; Gustafsson, Anders; Samuelson, Lars; Pettersson, Håkan

2017-12-01

Radial GaInP/AlGaInP nanowire array light-emitting diodes (LEDs) are promising candidates for novel high-efficiency solid state lighting due to their potentially large strain-free active emission volumes compared to planar LEDs. Moreover, by proper tuning of the diameter of the nanowires, the fraction of emitted light extracted can be significantly enhanced compared to that of planar LEDs. Reports so far on radial growth of nanowire LED structures, however, still point to significant challenges related to obtaining defect-free radial heterostructures. In this work, we present evidence of optically active growth-induced defects in a fairly broad energy range in vertically processed radial GaInP/AlGaInP quantum well nanowire array LEDs using a variety of complementary experimental techniques. In particular, we demonstrate strong infrared electroluminescence in a spectral range centred around 1 eV (1.2 μm) in addition to the expected red light emission from the quantum well. Spatially resolved cathodoluminescence studies reveal a patchy red light emission with clear spectral features along the NWs, most likely induced by variations in QW thickness, composition and barriers. Dark areas are attributed to infrared emission generated by competing defect-assisted radiative transitions, or to trapping mechanisms involving non-radiative recombination processes. Possible origins of the defects are discussed.

Hybrid heterojunction solar cell based on organic-inorganic silicon nanowire array architecture.

PubMed

Shen, Xiaojuan; Sun, Baoquan; Liu, Dong; Lee, Shuit-Tong

2011-12-07

Silicon nanowire arrays (SiNWs) on a planar silicon wafer can be fabricated by a simple metal-assisted wet chemical etching method. They can offer an excellent light harvesting capability through light scattering and trapping. In this work, we demonstrated that the organic-inorganic solar cell based on hybrid composites of conjugated molecules and SiNWs on a planar substrate yielded an excellent power conversion efficiency (PCE) of 9.70%. The high efficiency was ascribed to two aspects: one was the improvement of the light absorption by SiNWs structure on the planar components; the other was the enhancement of charge extraction efficiency, resulting from the novel top contact by forming a thin organic layer shell around the individual silicon nanowire. On the contrary, the sole planar junction solar cell only exhibited a PCE of 6.01%, due to the lower light trapping capability and the less hole extraction efficiency. It indicated that both the SiNWs structure and the thin organic layer top contact were critical to achieve a high performance organic/silicon solar cell. © 2011 American Chemical Society

Piezo‐Phototronic Effect Enhanced Flexible Solar Cells Based on n‐ZnO/p‐SnS Core–Shell Nanowire Array

PubMed Central

Zhu, Laipan; Wang, Longfei; Xue, Fei; Chen, Libo; Fu, Jianqiang; Feng, Xiaolong; Li, Tianfeng

2016-01-01

The piezo‐phototronic effect is about the enhanced separation, transport, and recombination of the photogenerated carriers using the piezoelectric polarization charges present in piezoelectric‐semiconductor materials. Here, it is presented that the piezo‐phototronic effect can be effectively applied to improve the relative conversion efficiency of a flexible solar cell based on n‐ZnO/p‐SnS core–shell nanowire array for 37.3% under a moderate vertical pressure. The performance of the solar cell can be effectively enhanced by a gentle bending of the device, showing its potential for application in curly geometries. This study not only adds further understanding about the concept of increasing solar energy conversion efficiency via piezo‐phototronic effect, but also demonstrates the great potential of piezo‐phototronic effect in the application of large‐scale, flexible, and lightweight nanowire array solar cells. PMID:28105394

Piezo-Phototronic Effect Enhanced Flexible Solar Cells Based on n-ZnO/p-SnS Core-Shell Nanowire Array.

PubMed

Zhu, Laipan; Wang, Longfei; Xue, Fei; Chen, Libo; Fu, Jianqiang; Feng, Xiaolong; Li, Tianfeng; Wang, Zhong Lin

2017-01-01

The piezo-phototronic effect is about the enhanced separation, transport, and recombination of the photogenerated carriers using the piezoelectric polarization charges present in piezoelectric-semiconductor materials. Here, it is presented that the piezo-phototronic effect can be effectively applied to improve the relative conversion efficiency of a flexible solar cell based on n-ZnO/p-SnS core-shell nanowire array for 37.3% under a moderate vertical pressure. The performance of the solar cell can be effectively enhanced by a gentle bending of the device, showing its potential for application in curly geometries. This study not only adds further understanding about the concept of increasing solar energy conversion efficiency via piezo-phototronic effect, but also demonstrates the great potential of piezo-phototronic effect in the application of large-scale, flexible, and lightweight nanowire array solar cells.

Extreme Carrier Depletion and Superlinear Photoconductivity in Ultrathin Parallel-Aligned ZnO Nanowire Array Photodetectors Fabricated by Infiltration Synthesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nam, Chang-Yong; Stein, Aaron

Ultrathin semiconductor nanowires enable high-performance chemical sensors and photodetectors, but their synthesis and device integration by standard complementary metal-oxide-semiconductor (CMOS)-compatible processes remain persistent challenges. This work demonstrates fully CMOS-compatible synthesis and integration of parallel-aligned polycrystalline ZnO nanowire arrays into ultraviolet photodetectors via infiltration synthesis, material hybridization technique derived from atomic layer deposition. The nanowire photodetector features unique, high device performances originating from extreme charge carrier depletion, achieving photoconductive on–off ratios of >6 decades, blindness to visible light, and ultralow dark currents as low as 1 fA, the lowest reported for nanostructure-based photoconductive photodetectors. Surprisingly, the low dark current is invariantmore » with increasing number of nanowires and the photodetector shows unusual superlinear photoconductivity, observed for the first time in nanowires, leading to increasing detector responsivity and other parameters for higher incident light powers. Temperature-dependent carrier concentration and mobility reveal the photoelectrochemical-thermionic emission process at grain boundaries, responsible for the observed unique photodetector performances and superlinear photoconductivity. Here, the results elucidate fundamental processes responsible for photogain in polycrystalline nanostructures, providing useful guidelines for developing nanostructure-based detectors and sensors. Lastly, the developed fully CMOS-compatible nanowire synthesis and device fabrication methods also have potentials for scalable integration of nanowire sensor devices and circuitries.« less

Extreme Carrier Depletion and Superlinear Photoconductivity in Ultrathin Parallel-Aligned ZnO Nanowire Array Photodetectors Fabricated by Infiltration Synthesis

DOE PAGES

Nam, Chang-Yong; Stein, Aaron

2017-11-15

Ultrathin semiconductor nanowires enable high-performance chemical sensors and photodetectors, but their synthesis and device integration by standard complementary metal-oxide-semiconductor (CMOS)-compatible processes remain persistent challenges. This work demonstrates fully CMOS-compatible synthesis and integration of parallel-aligned polycrystalline ZnO nanowire arrays into ultraviolet photodetectors via infiltration synthesis, material hybridization technique derived from atomic layer deposition. The nanowire photodetector features unique, high device performances originating from extreme charge carrier depletion, achieving photoconductive on–off ratios of >6 decades, blindness to visible light, and ultralow dark currents as low as 1 fA, the lowest reported for nanostructure-based photoconductive photodetectors. Surprisingly, the low dark current is invariantmore » with increasing number of nanowires and the photodetector shows unusual superlinear photoconductivity, observed for the first time in nanowires, leading to increasing detector responsivity and other parameters for higher incident light powers. Temperature-dependent carrier concentration and mobility reveal the photoelectrochemical-thermionic emission process at grain boundaries, responsible for the observed unique photodetector performances and superlinear photoconductivity. Here, the results elucidate fundamental processes responsible for photogain in polycrystalline nanostructures, providing useful guidelines for developing nanostructure-based detectors and sensors. Lastly, the developed fully CMOS-compatible nanowire synthesis and device fabrication methods also have potentials for scalable integration of nanowire sensor devices and circuitries.« less

Three-dimensional carbon- and binder-free nickel nanowire arrays as a high-performance and low-cost anode for direct hydrogen peroxide fuel cell

NASA Astrophysics Data System (ADS)

Ye, Ke; Guo, Fen; Gao, Yinyi; Zhang, Dongming; Cheng, Kui; Zhang, Wenping; Wang, Guiling; Cao, Dianxue

2015-12-01

A novel three-dimensional carbon- and binder-free nickel nanowire arrays (Ni NAs) electrode is successfully fabricated by a facile galvanostatic electrodeposition method using polycarbonate membrane as the template. The Ni NAs electrode achieves a oxidation current density (divided by the electroactive surface areas of Ni) of 25.1 mA cm-2 in 4 mol L-1 KOH and 0.9 mol L-1 H2O2 at 0.2 V (vs. Ag/AgCl) accompanied with a desirable stability, which is significantly higher than the catalytic activity of H2O2 electro-oxidation achieved previously with precious metals as catalysts. The impressive electrocatalytic performance is largely attributed to the superior 3D open structure and high electronic conductivity, which ensures the high utilization of Ni surfaces and makes the electrode have higher electrochemical activity. The apparent activation energy of H2O2 electro-oxidation on the Ni NAs catalyst is 13.59 kJ mol-1. A direct peroxide-peroxide fuel cell using the Ni NAs as anode exhibits a peak power density of 48.7 mW cm-2 at 20 °C. The electrode displays a great promise as the anode of direct peroxide-peroxide fuel cell due to its low cost, high activity and stability.

Micromagnetic simulation and the angular dependence of coercivity and remanence for array of polycrystalline nickel nanowires

NASA Astrophysics Data System (ADS)

Fuentes, G. P.; Holanda, J.; Guerra, Y.; Silva, D. B. O.; Farias, B. V. M.; Padrón-Hernández, E.

2017-02-01

We present here our experimental results for the preparation and characterization of nanowires of nickel and the analysis of the angular dependence of coercivity and remanence using experimental data and micromagnetic simulation. The fabrication was made by using aluminum oxide membranes as templates and deposited nickel by an electrochemical route. The magnetic measurements showed that coercivity and remanence are dependent of the angle of application of the external magnetic field. Our results are different than that expected for the coherent, vortex and transversal modes of the reversion for the magnetic moments. According to the transmission electron microscopy analysis we can see that our nanowires have not a perfect cylindrical format. That is why we have used the ellipsoids chain model for better understanding the real structure of wires and its relation with the magnetic behavior. In order to generate theoretical results for this configuration we have made micromagnetic simulation using Nmag code. Our numerical results for the realistic distances are in correspondence with the magnetic measurements and we can see that there are contradictions if we assume the transverse reversal mode. Then, we can conclude that structure of nanowires should be taken into account to understand the discrepancies reported in the literature for the reversion mechanism in arrays of nickel nanowires.

Morphology and Doping Engineering of Sn-Doped Hematite Nanowire Photoanodes.

PubMed

Li, Mingyang; Yang, Yi; Ling, Yichuan; Qiu, Weitao; Wang, Fuxin; Liu, Tianyu; Song, Yu; Liu, Xiaoxia; Fang, Pingping; Tong, Yexiang; Li, Yat

2017-04-12

High-temperature activation has been commonly used to boost the photoelectrochemical (PEC) performance of hematite nanowires for water oxidation, by inducing Sn diffusion from fluorine-doped tin oxide (FTO) substrate into hematite. Yet, hematite nanowires thermally annealed at high temperature suffer from two major drawbacks that negatively affect their performance. First, the structural deformation reduces light absorption capability of nanowire. Second, this "passive" doping method leads to nonuniform distribution of Sn dopant in nanowire and limits the Sn doping concentration. Both factors impair the electrochemical properties of hematite nanowire. Here we demonstrate a silica encapsulation method that is able to simultaneously retain the hematite nanowire morphology even after high-temperature calcination at 800 °C and improve the concentration and uniformity of dopant distribution along the nanowire growth axis. The capability of retaining nanowire morphology allows tuning the nanowire length for optimal light absorption. Uniform distribution of Sn doping enhances the donor density and charge transport of hematite nanowire. The morphology and doping engineered hematite nanowire photoanode decorated with a cobalt oxide-based oxygen evolution reaction (OER) catalyst achieves an outstanding photocurrent density of 2.2 mA cm -2 at 0.23 V vs Ag/AgCl. This work provides important insights on how the morphology and doping uniformity of hematite photoanodes affect their PEC performance.

Why self-catalyzed nanowires are most suitable for large-scale hierarchical integrated designs of nanowire nanoelectronics

NASA Astrophysics Data System (ADS)

Noor Mohammad, S.

2011-10-01

Nanowires are grown by a variety of mechanisms, including vapor-liquid-solid, vapor-quasiliquid-solid or vapor-quasisolid-solid, oxide-assisted growth, and self-catalytic growth (SCG) mechanisms. A critical analysis of the suitability of self-catalyzed nanowires, as compared to other nanowires, for next-generation technology development has been carried out. Basic causes of superiority of self-catalyzed (SCG) nanowires over other nanowires have been described. Polytypism in nanowires has been studied, and a model for polytypism has been proposed. The model predicts polytypism in good agreement with available experiments. This model, together with various evidences, demonstrates lower defects, dislocations, and stacking faults in SCG nanowires, as compared to those in other nanowires. Calculations of carrier mobility due to dislocation scattering, ionized impurity scattering, and acoustic phonon scattering explain the impact of defects, dislocations, and stacking faults on carrier transports in SCG and other nanowires. Analyses of growth mechanisms for nanowire growth directions indicate SCG nanowires to exhibit the most controlled growth directions. In-depth investigation uncovers the fundamental physics underlying the control of growth direction by the SCG mechanism. Self-organization of nanowires in large hierarchical arrays is crucial for ultra large-scale integration (ULSI). Unique features and advantages of self-organized SCG nanowires, unlike other nanowires, for this ULSI have been discussed. Investigations of nanowire dimension indicate self-catalyzed nanowires to have better control of dimension, higher stability, and higher probability, even for thinner structures. Theoretical calculations show that self-catalyzed nanowires, unlike catalyst-mediated nanowires, can have higher growth rate and lower growth temperature. Nanowire and nanotube characteristics have been found also to dictate the performance of nanoelectromechanical systems. Defects, such as

Core-shell silicon nanowire solar cells

PubMed Central

Adachi, M. M.; Anantram, M. P.; Karim, K. S.

2013-01-01

Silicon nanowires can enhance broadband optical absorption and reduce radial carrier collection distances in solar cell devices. Arrays of disordered nanowires grown by vapor-liquid-solid method are attractive because they can be grown on low-cost substrates such as glass, and are large area compatible. Here, we experimentally demonstrate that an array of disordered silicon nanowires surrounded by a thin transparent conductive oxide has both low diffuse and specular reflection with total values as low as < 4% over a broad wavelength range of 400 nm < λ < 650 nm. These anti-reflective properties together with enhanced infrared absorption in the core-shell nanowire facilitates enhancement in external quantum efficiency using two different active shell materials: amorphous silicon and nanocrystalline silicon. As a result, the core-shell nanowire device exhibits a short-circuit current enhancement of 15% with an amorphous Si shell and 26% with a nanocrystalline Si shell compared to their corresponding planar devices. PMID:23529071

Controllable Synthesis of Ordered Mesoporous Mo2C@Graphitic Carbon Core-Shell Nanowire Arrays for Efficient Electrocatalytic Hydrogen Evolution.

PubMed

Zhu, Jiahui; Yao, Yan; Chen, Zhi; Zhang, Aijian; Zhou, Mengyuan; Guo, Jun; Wu, Winston Duo; Chen, Xiao Dong; Li, Yanguang; Wu, Zhangxiong

2018-06-06

Mo 2 C is a possible substitute to Pt-group metals for electrocatalytic hydrogen evolution reaction (HER). Both support-free and carbon-supported Mo 2 C nanomaterials with improved HER performance have been developed. Herein, distinct from prior research, novel ordered mesoporous core-shell nanowires with Mo 2 C cores and ultrathin graphitic carbon (GC) shells are rationally synthesized and demonstrated to be excellent for HER. The synthesis is fulfilled via a hard-templating approach combining in situ carburization and localized carbon deposition. Phosphomolybdic acid confined in the SBA-15 template is first converted to MoO 2 , which is then in situ carburized to Mo 2 C nanowires with abundant surface defects. Simultaneously, GC layer (the thickness is down to ∼1.0 nm in most areas) is controlled to be locally deposited on the Mo 2 C surface because of its strong affinity with carbon and catalytic effect on graphitization. Removal of the template results in the Mo 2 C@GC core-shell nanowire arrays with the structural properties well-characterized. They exhibit excellent performance for HER with a low overpotential of 125 mV at 10 mA cm -2 , a small Tafel slope of 66 mV dec -1 , and an excellent stability in acidic electrolytes. The influences of several factors, especially the spatial configuration and relative contents of the GC and Mo 2 C components, on HER performance are elucidated with control experiments. The excellent HER performance of the mesoporous Mo 2 C@GC core-shell nanowire arrays originates from the rough Mo 2 C nanowires with diverse active sites and short charge-transfer paths and the ultrathin GC shells with improved surface area, electronic conductivity, and stabilizing effect on Mo 2 C.

Enhanced flexibility and electron-beam-controlled shape recovery in alumina-coated Au and Ag core-shell nanowires

NASA Astrophysics Data System (ADS)

Vlassov, Sergei; Polyakov, Boris; Vahtrus, Mikk; Mets, Magnus; Antsov, Mikk; Oras, Sven; Tarre, Aivar; Arroval, Tõnis; Lõhmus, Rünno; Aarik, Jaan

2017-12-01

The proper choice of coating materials and methods in core-shell nanowire (NW) engineering is crucial to assuring improved characteristics or even new functionalities of the resulting composite structures. In this paper, we have reported electron-beam-induced reversible elastic-to-plastic transition in Ag/Al2O3 and Au/Al2O3 NWs prepared by the coating of Ag and Au NWs with Al2O3 by low-temperature atomic layer deposition. The observed phenomenon enabled freezing the bent core-shell NW at any arbitrary curvature below the yield strength of the materials and later restoring its initially straight profile by irradiating the NW with electrons. In addition, we demonstrated that the coating efficiently protects the core material from fracture and plastic yield, allowing it to withstand significantly higher deformations and stresses in comparison to uncoated NW.

Effects of polymer surface energy on morphology and properties of silver nanowire fabricated via nanoimprint and E-beam evaporation

NASA Astrophysics Data System (ADS)

Zhao, Zhi-Jun; Hwang, Soon Hyoung; Jeon, Sohee; Jung, Joo-Yun; Lee, Jihye; Choi, Dae-Geun; Choi, Jun-Hyuk; Park, Sang-Hu; Jeong, Jun-Ho

2017-10-01

In this paper, we demonstrate that use of different nanoimprint resins as a polymer pattern has a significant effect on the morphology of silver (Ag) nanowires deposited via an E-beam evaporator. RM-311 and Ormo-stamp resins are chosen as a polymer pattern to form a line with dimensions of width (100 nm) × space (100 nm) × height (120 nm) by using nanoimprint lithography (NIL). Their contact angles are then measured to evaluate their surface energies. In order to compare the properties of the Ag nanowires deposited on the various polymer patterns with different surface energies, hydrophobic surface treatment of the polymer pattern surface is implemented using self-assembled monolayers. In addition, gold and aluminum nanowires are fabricated for comparison with the Ag nanowires, with the differences in the nanowire morphologies being determined by the different atomic properties. The monocrystalline and polycrystalline structures of the various Ag nanowire formations are observed using transmission electron microscopy. In addition, the melting temperatures and optical properties of four kinds of Ag nanowire morphologies deposited on various polymer patterns are evaluated using a hot plate and an ultraviolet-visible (UV-vis) spectrometer, respectively. The results indicate that the morphology of the Ag nanowire determines the melting temperature and the transmission. We believe that these findings will greatly aid the development of NIL, along with physical evaporation and chemical deposition techniques, and will be widely employed in optics, biology, and surface wettability applications.

Roll-to-roll slot-die coating of 400 mm wide, flexible, transparent Ag nanowire films for flexible touch screen panels

PubMed Central

Kim, Dong-Ju; Shin, Hae-In; Ko, Eun-Hye; Kim, Ki-Hyun; Kim, Tae-Woong; Kim, Han-Ki

2016-01-01

We report fabrication of large area Ag nanowire (NW) film coated using a continuous roll-to-roll (RTR) slot die coater as a viable alternative to conventional ITO electrodes for cost-effective and large-area flexible touch screen panels (TSPs). By controlling the flow rate of shear-thinning Ag NW ink in the slot die, we fabricated Ag NW percolating network films with different sheet resistances (30–70 Ohm/square), optical transmittance values (89–90%), and haze (0.5–1%) percentages. Outer/inner bending, twisting, and rolling tests as well as dynamic fatigue tests demonstrated that the mechanical flexibility of the slot-die coated Ag NW films was superior to that of conventional ITO films. Using diamond-shape patterned Ag NW layer electrodes (50 Ohm/square, 90% optical transmittance), we fabricated 12-inch flexible film-film type and rigid glass-film-film type TSPs. Successful operation of flexible TSPs with Ag NW electrodes indicates that slot-die-coated large-area Ag NW films are promising low cost, high performance, and flexible transparent electrodes for cost-effective large-area flexible TSPs and can be substituted for ITO films, which have high sheet resistance and are brittle. PMID:27677410

Study of transmission function and electronic transport in one dimensional silver nanowire: Ab-initio method using density functional theory (DFT)

NASA Astrophysics Data System (ADS)

Thakur, Anil; Kashyap, Rajinder

2018-05-01

Single nanowire electrode devices have their application in variety of fields which vary from information technology to solar energy. Silver nanowires, made in an aqueous chemical reduction process, can be reacted with gold salt to create bimetallic nanowires. Silver nanowire can be used as electrodes in batteries and have many other applications. In this paper we investigated structural and electronic transport properties of Ag nanowire using density functional theory (DFT) with SIESTA code. Electronic transport properties of Ag nanowire have been studied theoretically. First of all an optimized geometry for Ag nanowire is obtained using DFT calculations, and then the transport relations are obtained using NEGF approach. SIESTA and TranSIESTA simulation codes are used in the calculations respectively. The electrodes are chosen to be the same as the central region where transport is studied, eliminating current quantization effects due to contacts and focusing the electronic transport study to the intrinsic structure of the material. By varying chemical potential in the electrode regions, an I-V curve is traced which is in agreement with the predicted behavior. Bulk properties of Ag are in agreement with experimental values which make the study of electronic and transport properties in silver nanowires interesting because they are promising materials as bridging pieces in nanoelectronics. Transmission coefficient and V-I characteristic of Ag nano wire reveals that silver nanowire can be used as an electrode device.

Integration of a highly ordered gold nanowires array with glucose oxidase for ultra-sensitive glucose detection.

PubMed

Cui, Jiewu; Adeloju, Samuel B; Wu, Yucheng

2014-01-27

A highly sensitive amperometric nanobiosensor has been developed by integration of glucose oxidase (GO(x)) with a gold nanowires array (AuNWA) by cross-linking with a mixture of glutaraldehyde (GLA) and bovine serum albumin (BSA). An initial investigation of the morphology of the synthesized AuNWA by field emission scanning electron microscopy (FESEM) and field emission transmission electron microscopy (FETEM) revealed that the nanowires array was highly ordered with rough surface, and the electrochemical features of the AuNWA with/without modification were also investigated. The integrated AuNWA-BSA-GLA-GO(x) nanobiosensor with Nafion membrane gave a very high sensitivity of 298.2 μA cm(-2) mM(-1) for amperometric detection of glucose, while also achieving a low detection limit of 0.1 μM, and a wide linear range of 5-6000 μM. Furthermore, the nanobiosensor exhibited excellent anti-interference ability towards uric acid (UA) and ascorbic acid (AA) with the aid of Nafion membrane, and the results obtained for the analysis of human blood serum indicated that the device is capable of glucose detection in real samples. Copyright © 2013 Elsevier B.V. All rights reserved.

2D XANES-XEOL mapping: observation of enhanced band gap emission from ZnO nanowire arrays

NASA Astrophysics Data System (ADS)

Wang, Zhiqiang; Guo, Xiaoxuan; Sham, Tsun-Kong

2014-05-01

Using 2D XANES-XEOL spectroscopy, it is found that the band gap emission of ZnO nanowire arrays is substantially enhanced i.e. that the intensity ratio between the band gap and defect emissions increases by more than an order of magnitude when the excitation energy is scanned across the O K-edge. Possible mechanisms are discussed.Using 2D XANES-XEOL spectroscopy, it is found that the band gap emission of ZnO nanowire arrays is substantially enhanced i.e. that the intensity ratio between the band gap and defect emissions increases by more than an order of magnitude when the excitation energy is scanned across the O K-edge. Possible mechanisms are discussed. Electronic supplementary information (ESI) available: XEOL spectra with different excitation energies. X-ray attenuation length vs. photon energy. Details of surface defects in ZnO NWs. The second O K-edge and Zn L-edge 2D XANES-XEOL maps. Comparison of the first and second TEY at O K-edge and Zn L-edge scans, respectively. Raman spectra of the ZnO NWs with different IBGE/IDE ratios. See DOI: 10.1039/c4nr01049c

Hexagonal Nanopyramidal Prisms of Nearly Intrinsic InN on Patterned GaN Nanowire Arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Golam Sarwar, A. T. M.; Leung, Benjamin; Wang, George T.

By using multiple growth steps that separate the nucleation and growth processes, we show that nearly intrinsic InN single nanocrystals of high optical quality can be formed on patterned GaN nanowire arrays by molecular beam epitaxy. The InN nanostructures form into well-defined hexagonal prisms with pyramidal tops. Micro-photoluminescence (μ-PL) is carried out at low temperature (LT: 28.2 K) and room temperature (RT: 285 K) to gauge the relative material quality of the InN nanostructures. Nanopyramidal prisms grown using a three-step growth method are found to show superior quantum efficiency. In conclusion, excitation and temperature dependent μ-PL demonstrates the very highmore » quality and nearly intrinsic nature of the ordered InN nanostructure arrays.« less

Hexagonal Nanopyramidal Prisms of Nearly Intrinsic InN on Patterned GaN Nanowire Arrays

DOE PAGES

Golam Sarwar, A. T. M.; Leung, Benjamin; Wang, George T.; ...

2018-01-04

By using multiple growth steps that separate the nucleation and growth processes, we show that nearly intrinsic InN single nanocrystals of high optical quality can be formed on patterned GaN nanowire arrays by molecular beam epitaxy. The InN nanostructures form into well-defined hexagonal prisms with pyramidal tops. Micro-photoluminescence (μ-PL) is carried out at low temperature (LT: 28.2 K) and room temperature (RT: 285 K) to gauge the relative material quality of the InN nanostructures. Nanopyramidal prisms grown using a three-step growth method are found to show superior quantum efficiency. In conclusion, excitation and temperature dependent μ-PL demonstrates the very highmore » quality and nearly intrinsic nature of the ordered InN nanostructure arrays.« less

Conductivity of Nanowire Arrays under Random and Ordered Orientation Configurations

PubMed Central

Jagota, Milind; Tansu, Nelson

2015-01-01

A computational model was developed to analyze electrical conductivity of random metal nanowire networks. It was demonstrated for the first time through use of this model that a performance gain in random metal nanowire networks can be achieved by slightly restricting nanowire orientation. It was furthermore shown that heavily ordered configurations do not outperform configurations with some degree of randomness; randomness in the case of metal nanowire orientations acts to increase conductivity. PMID:25976936

Novel Flexible Transparent Conductive Films with Enhanced Chemical and Electromechanical Sustainability: TiO2 Nanosheet-Ag Nanowire Hybrid.

PubMed

Sohn, Hiesang; Kim, Seyun; Shin, Weonho; Lee, Jong Min; Lee, Hyangsook; Yun, Dong-Jin; Moon, Kyoung-Seok; Han, In Taek; Kwak, Chan; Hwang, Seong-Ju

2018-01-24

Flexible transparent conductive films (TCFs) of TiO 2 nanosheet (TiO 2 NS) and silver nanowire (Ag NW) network hybrid were prepared through a simple and scalable solution-based process. The as-formed TiO 2 NS-Ag NW hybrid TCF shows a high optical transmittance (TT: 97% (90.2% including plastic substrate)) and low sheet resistance (R s : 40 Ω/sq). In addition, the TiO 2 NS-Ag NW hybrid TCF exhibits a long-time chemical/aging and electromechanical stability. As for the chemical/aging stability, the hybrid TCF of Ag NW and TiO 2 NS reveals a retained initial conductivity (ΔR s /R s < 1%) under ambient oxidant gas over a month, superior to that of bare Ag NW (ΔR s /R s > 4000%) or RuO 2 NS-Ag NW hybrid (ΔR s /R s > 200%). As corroborated by the density functional theory simulation, the superb chemical stability of TiO 2 NS-Ag NW hybrid is attributable to the unique role of TiO 2 NS as a barrier, which prevents Ag NW's chemical corrosion via the attenuated adsorption of sulfidation molecules (H 2 S) on TiO 2 NS. With respect to the electromechanical stability, in contrast to Ag NWs (ΔR/R 0 ∼ 152.9%), our hybrid TCF shows a limited increment of fractional resistivity (ΔR/R 0 ∼ 14.4%) after 200 000 cycles of the 1R bending test (strain: 6.7%) owing to mechanically welded Ag NW networks by TiO 2 NS. Overall, our unique hybrid of TiO 2 NS and Ag NW exhibits excellent electrical/optical properties and reliable chemical/electromechanical stabilities.

Photodeposition of Ag2S on TiO2 nanorod arrays for quantum dot-sensitized solar cells

PubMed Central

2013-01-01

Ag2S quantum dots were deposited on the surface of TiO2 nanorod arrays by a two-step photodeposition. The prepared TiO2 nanorod arrays as well as the Ag2S deposited electrodes were characterized by X-ray diffraction, scanning electron microscope, and transmission electron microscope, suggesting a large coverage of Ag2S quantum dots on the ordered TiO2 nanorod arrays. UV–vis absorption spectra of Ag2S deposited electrodes show a broad absorption range of the visible light. The quantum dot-sensitized solar cells (QDSSCs) based on these electrodes were fabricated, and the photoelectrochemical properties were examined. A high photocurrent density of 10.25 mA/cm2 with a conversion efficiency of 0.98% at AM 1.5 solar light of 100 mW/cm2 was obtained with an optimal photodeposition time. The performance of the QDSSC at different incident light intensities was also investigated. The results display a better performance at a lower incident light level with a conversion efficiency of 1.25% at 47 mW/cm2. PMID:23286551

Vertically aligned CdSe nanowire arrays for energy harvesting and piezotronic devices.

PubMed

Zhou, Yu Sheng; Wang, Kai; Han, Weihua; Rai, Satish Chandra; Zhang, Yan; Ding, Yong; Pan, Caofeng; Zhang, Fang; Zhou, Weilie; Wang, Zhong Lin

2012-07-24

We demonstrated the energy harvesting potential and piezotronic effect in vertically aligned CdSe nanowire (NW) arrays for the first time. The CdSe NW arrays were grown on a mica substrate by the vapor-liquid-solid process using a CdSe thin film as seed layer and platinum as catalyst. High-resolution transmission electron microscopy image and selected area electron diffraction pattern indicate that the CdSe NWs have a wurtzite structure and growth direction along (0001). Using conductive atomic force microscopy (AFM), an average output voltage of 30.7 mV and maximum of 137 mV were obtained. To investigate the effect of strain on electron transport, the current-voltage characteristics of the NWs were studied by positioning an AFM tip on top of an individual NW. By applying normal force/stress on the NW, the Schottky barrier between the Pt and CdSe was found to be elevated due to the piezotronic effect. With the change of strain of 0.12%, a current decreased from 84 to 17 pA at 2 V bias. This paper shows that the vertical CdSe NW array is a potential candidate for future piezo-phototronic devices.

Oriented epitaxial TiO2 nanowires for water splitting

NASA Astrophysics Data System (ADS)

Hou, Wenting; Cortez, Pablo; Wuhrer, Richard; Macartney, Sam; Bozhilov, Krassimir N.; Liu, Rong; Sheppard, Leigh R.; Kisailus, David

2017-06-01

Highly oriented epitaxial rutile titanium dioxide (TiO2) nanowire arrays have been hydrothermally grown on polycrystalline TiO2 templates with their orientation dependent on the underlying TiO2 grain. Both the diameter and areal density of the nanowires were tuned by controlling the precursor concentration, and the template surface energy and roughness. Nanowire tip sharpness was influenced by precursor solubility and diffusivity. A new secondary ion mass spectrometer technique has been developed to install additional nucleation sites in single crystal TiO2 templates and the effect on nanowire growth was probed. Using the acquired TiO2 nanowire synthesis knowhow, an assortment of nanowire arrays were installed upon the surface of undoped TiO2 photo-electrodes and assessed for their photo-electrochemical water splitting performance. The key result obtained was that the presence of short and dispersed nanowire arrays significantly improved the photocurrent when the illumination intensity was increased from 100 to 200 mW cm-2. This is attributed to the alignment of the homoepitaxially grown nanowires to the [001] direction, which provides the fastest charge transport in TiO2 and an improved pathway for photo-holes to find water molecules and undertake oxidation. This result lays a foundation for achieving efficient water splitting under conditions of concentrated solar illumination.

Band gap enhancement of glancing angle deposited TiO2 nanowire array

NASA Astrophysics Data System (ADS)

Chinnamuthu, P.; Mondal, A.; Singh, N. K.; Dhar, J. C.; Chattopadhyay, K. K.; Bhattacharya, Sekhar

2012-09-01

Vertically oriented TiO2 nanowire (NW) arrays were fabricated by glancing angle deposition technique. Field emission-scanning electron microscopy shows the formation of two different diameters ˜80 nm and ˜40 nm TiO2 NW for 120 and 460 rpm azimuthal rotation of the substrate. The x-ray diffraction and Raman scattering depicted the presence of rutile and anatase phase TiO2. The overall Raman scattering intensity decreased with nanowire diameter. The role of phonon confinement in anatase and rutile peaks has been discussed. The red (7.9 cm-1 of anatase Eg) and blue (7.4 cm-1 of rutile Eg, 7.8 cm-1 of rutile A1g) shifts of Raman frequencies were observed. UV-vis absorption measurements show the main band absorption at 3.42 eV, 3.48 eV, and ˜3.51 eV for thin film and NW prepared at 120 and 460 rpm, respectively. Three fold enhance photon absorption and intense light emission were observed for NW assembly. The photoluminescence emission from the NW assembly revealed blue shift in main band transition due to quantum confinement in NW structures.

Ag colloids and arrays for plasmonic non-radiative energy transfer from quantum dots to a quantum well

NASA Astrophysics Data System (ADS)

Murphy, Graham P.; Gough, John J.; Higgins, Luke J.; Karanikolas, Vasilios D.; Wilson, Keith M.; Garcia Coindreau, Jorge A.; Zubialevich, Vitaly Z.; Parbrook, Peter J.; Bradley, A. Louise

2017-03-01

Non-radiative energy transfer (NRET) can be an efficient process of benefit to many applications including photovoltaics, sensors, light emitting diodes and photodetectors. Combining the remarkable optical properties of quantum dots (QDs) with the electrical properties of quantum wells (QWs) allows for the formation of hybrid devices which can utilize NRET as a means of transferring absorbed optical energy from the QDs to the QW. Here we report on plasmon-enhanced NRET from semiconductor nanocrystal QDs to a QW. Ag nanoparticles in the form of colloids and ordered arrays are used to demonstrate plasmon-mediated NRET from QDs to QWs with varying top barrier thicknesses. Plasmon-mediated energy transfer (ET) efficiencies of up to ˜25% are observed with the Ag colloids. The distance dependence of the plasmon-mediated ET is found to follow the same d -4 dependence as the direct QD to QW ET. There is also evidence for an increase in the characteristic distance of the interaction, thus indicating that it follows a Förster-like model with the Ag nanoparticle-QD acting as an enhanced donor dipole. Ordered Ag nanoparticle arrays display plasmon-mediated ET efficiencies up to ˜21%. To explore the tunability of the array system, two arrays with different geometries are presented. It is demonstrated that changing the geometry of the array allows a transition from overall quenching of the acceptor QW emission to enhancement, as well as control of the competition between the QD donor quenching and ET rates.

Vapor-liquid-solid growth of <110> silicon nanowire arrays

NASA Astrophysics Data System (ADS)

Eichfeld, Sarah M.; Hainey, Mel F.; Shen, Haoting; Kendrick, Chito E.; Fucinato, Emily A.; Yim, Joanne; Black, Marcie R.; Redwing, Joan M.

2013-09-01

The epitaxial growth of <110> silicon nanowires on (110) Si substrates by the vapor-liquid-solid growth process was investigated using SiCl4 as the source gas. A high percentage of <110> nanowires was obtained at high temperatures and reduced SiCl4 partial pressures. Transmission electron microscopy characterization of the <110> Si nanowires revealed symmetric V-shaped {111} facets at the tip and large {111} facets on the sidewalls of the nanowires. The symmetric {111} tip faceting was explained as arising from low catalyst supersaturation during growth which is expected to occur given the near-equilibrium nature of the SiCl4 process. The predominance of {111} facets obtained under these conditions promotes the growth of <110> SiNWs.

Improvement of the physical properties of ZnO/CdTe core-shell nanowire arrays by CdCl2 heat treatment for solar cells

PubMed Central

2014-01-01

CdTe is an important compound semiconductor for solar cells, and its use in nanowire-based heterostructures may become a critical requirement, owing to the potential scarcity of tellurium. The effects of the CdCl2 heat treatment are investigated on the physical properties of vertically aligned ZnO/CdTe core-shell nanowire arrays grown by combining chemical bath deposition with close space sublimation. It is found that recrystallization phenomena are induced by the CdCl2 heat treatment in the CdTe shell composed of nanograins: its crystallinity is improved while grain growth and texture randomization occur. The presence of a tellurium crystalline phase that may decorate grain boundaries is also revealed. The CdCl2 heat treatment further favors the chlorine doping of the CdTe shell with the formation of chlorine A-centers and can result in the passivation of grain boundaries. The absorption properties of ZnO/CdTe core-shell nanowire arrays are highly efficient, and more than 80% of the incident light can be absorbed in the spectral range of the solar irradiance. The resulting photovoltaic properties of solar cells made from ZnO/CdTe core-shell nanowire arrays covered with CuSCN/Au back-side contact are also improved after the CdCl2 heat treatment. However, recombination and trap phenomena are expected to operate, and the collection of the holes that are mainly photo-generated in the CdTe shell from the CuSCN/Au back-side contact is presumably identified as the main critical point in these solar cells. PMID:24910576

Fully solution-processed transparent electrodes based on silver nanowire composites for perovskite solar cells.

PubMed

Kim, Areum; Lee, Hongseuk; Kwon, Hyeok-Chan; Jung, Hyun Suk; Park, Nam-Gyu; Jeong, Sunho; Moon, Jooho

2016-03-28

We report all-solution-processed transparent conductive electrodes based on Ag nanowire (AgNW)-embedded metal oxide composite films for application in organometal halide perovskite solar cells. To address the thermal instability of Ag nanowires, we used combustive sol-gel derived thin films to construct ZnO/ITO/AgNW/ITO composite structures. The resulting composite configuration effectively prevented the AgNWs from undergoing undesirable side-reactions with halogen ions present in the perovskite precursor solutions that significantly deteriorate the optoelectrical properties of Ag nanowires in transparent conductive films. AgNW-based composite electrodes had a transmittance of ∼80% at 550 nm and sheet resistance of 18 Ω sq(-1). Perovskite solar cells fabricated using a fully solution-processed transparent conductive electrode, Au/spiro-OMeTAD/CH3NH3PbI3 + m-Al2O3/ZnO/ITO/AgNW/ITO, exhibited a power conversion efficiency of 8.44% (comparable to that of the FTO/glass-based counterpart at 10.81%) and were stable for 30 days in ambient air. Our results demonstrate the feasibility of using AgNWs as a transparent bottom electrode in perovskite solar cells produced by a fully printable process.

Thermoporometry characterization of silica microparticles and nanowires.

PubMed

Wu, Jiaxin; Zheng, Han; Cheng, He; Zhou, L; Leong, K C; Rajagopalan, R; Too, H P; Choi, W K

2014-03-04

We present the results of a systematic study on the porosity of silica microparticles and nanowires prepared by glancing angle deposition-metal-assisted chemical etching (GLAD-MACE) and interference lithography-metal-assisted chemical etching (IL-MACE) techniques using the thermoporometry (TPM) method. Good agreement was obtained between our TPM results and published data provided by the suppliers of silica microparticles. TPM characterization of the GLAD-MACE and IL-MACE nanowires was carried out on the basis of parameters obtained from TPM experiments on microparticles. Our nanowires showed a similar trend but lower values of the pore volume and surface area than nanowires prepared by MACE with AgNO3 solution. We attribute the enhanced bioanalysis performance of the GLAD-MACE nanowires based devices to the increased pore volume and total surface area of the nanowires.

Magnetic and superconducting nanowires.

PubMed

Piraux, L; Encinas, A; Vila, L; Mátéfi-Tempfli, S; Mátéfi-Tempfli, M; Darques, M; Elhoussine, F; Michotte, S

2005-03-01

This article is focused on the use of electrodeposition and of various nanoporous templates for the fabrication of metallic nanowires made from single metals (Ni, Co, Pb, Sn), alloys (NiFe, CoFe, CoPt), and multilayers (Co/Cu, NiFe/Cu). An overview is given of our recent studies performed on both magnetic and superconducting nanowires. Using different approaches entailing measurements on both single wires and arrays, numerous interesting physical properties have been identified in relation to the nanoscopic dimensions of these materials. Finally, various novel applications of the nanowires are also discussed.

Highly catalytic and stabilized titanium nitride nanowire array-decorated graphite felt electrodes for all vanadium redox flow batteries

NASA Astrophysics Data System (ADS)

Wei, L.; Zhao, T. S.; Zeng, L.; Zeng, Y. K.; Jiang, H. R.

2017-02-01

In this work, we prepare a highly catalytic and stabilized titanium nitride (TiN) nanowire array-decorated graphite felt electrode for all vanadium redox flow batteries (VRFBs). Free-standing TiN nanowires are synthesized by a two-step process, in which TiO2 nanowires are first grown onto the surface of graphite felt via a seed-assisted hydrothermal method and then converted to TiN through nitridation reaction. When applied to VRFBs, the prepared electrode enables the electrolyte utilization and energy efficiency to be 73.9% and 77.4% at a high current density of 300 mA cm-2, which are correspondingly 43.3% and 15.4% higher than that of battery assembled with a pristine electrode. More impressively, the present battery exhibits good stability and high capacity retention during the cycle test. The superior performance is ascribed to the significant improvement in the electrochemical kinetics and enlarged active sites toward V3+/V2+ redox reaction.

Controlled growth of standing Ag nanorod arrays on bare Si substrate using glancing angle deposition for self-cleaning applications

NASA Astrophysics Data System (ADS)

Singh, Dhruv P.; Singh, J. P.

2014-03-01

A facile approach to manipulate the hydrophobicity of surface by controlled growth of standing Ag nanorod arrays is presented. Instead of following the complicated conventional method of the template-assisted growth, the morphology or particularly average diameter and number density (nanorods cm-2) of nanorods were controlled on bare Si substrate by simply varying the deposition rate during glancing angle deposition. The contact angle measurements showed that the evolution of Ag nanorods reduces the surface energy and makes an increment in the apparent water contact angle compared to the plain Ag thin film. The contact angle was found to increase for the Ag nanorod samples grown at lower deposition rates. Interestingly, the morphology of the nanorod arrays grown at very low deposition rate (1.2 Å sec-1) results in a self-cleaning superhydrophobic surface of contact angle about 157° and a small roll-off angle about 5°. The observed improvement in hydrophobicity with change in the morphology of nanorod arrays is explained as the effect of reduction in solid fraction within the framework of Cassie-Baxter model. These self-cleaning Ag nanorod arrays could have a significant impact in wide range of applications such as anti-icing coatings, sensors and solar panels.

1.4 µm-Thick Transparent Radio Frequency Transmission Lines Based on Instant Fusion of Polyethylene Terephthalate Through Surface of Ag Nanowires

NASA Astrophysics Data System (ADS)

Kim, Sang-Woo; Kim, Kwang-Seok; Park, Myeongkoo; Nah, Wansoo; Kim, Dae Up; Lee, Cheul-Ro; Jung, Seung-Boo; Kim, Jong-Woong

2018-05-01

Though a percolated network of silver nanowires (AgNWs) has been considered the most promising flexible transparent electrode because of it high conductivity, high transmittance, and excellent flexibility, fabrication of AgNW-based transmission lines designed to conduct high frequency signals has been scarcely reported. The fabrication and performance of extremely thin (1.4 µm thick) and low lossy (smaller than - 17 dB for reflection coefficient corresponding to 2.5 GHz) transmission lines with unprecedented transparency (higher than 90% for the entire visible light spectrum) are demonstrated in this study. AgNWs deposited onto a 1.4 µm-thick polyethylene terephthalate (PET) sheet were irradiated by intense-pulsed-light to selectively raise their temperature. The intensive photon energy delivered to the AgNWs simultaneously caused the active diffusion of Ag atoms and plasmonic welding, resulting in large drops in resistivity without drastic changes in their physical shape or the optical transmittance of the films. Furthermore, absorption of heat also thermally activated the underlying polymer and causing it to react with the surface of the AgNWs—this results in enhanced adhesion between the AgNWs and the PET. Measurements and simulation of specially designed coplanar waveguide circuits revealed that the fabricated electrode could simultaneously provide excellent transmission characteristics and mechanical stability and transparency.

Crystal Orientation Controlled Photovoltaic Properties of Multilayer GaAs Nanowire Arrays.

PubMed

Han, Ning; Yang, Zai-Xing; Wang, Fengyun; Yip, SenPo; Li, Dapan; Hung, Tak Fu; Chen, Yunfa; Ho, Johnny C

2016-06-28

In recent years, despite significant progress in the synthesis, characterization, and integration of various nanowire (NW) material systems, crystal orientation controlled NW growth as well as real-time assessment of their growth-structure-property relationships still presents one of the major challenges in deploying NWs for practical large-scale applications. In this study, we propose, design, and develop a multilayer NW printing scheme for the determination of crystal orientation controlled photovoltaic properties of parallel GaAs NW arrays. By tuning the catalyst thickness and nucleation and growth temperatures in the two-step chemical vapor deposition, crystalline GaAs NWs with uniform, pure ⟨110⟩ and ⟨111⟩ orientations and other mixture ratios can be successfully prepared. Employing lift-off resists, three-layer NW parallel arrays can be easily attained for X-ray diffraction in order to evaluate their growth orientation along with the fabrication of NW parallel array based Schottky photovoltaic devices for the subsequent performance assessment. Notably, the open-circuit voltage of purely ⟨111⟩-oriented NW arrayed cells is far higher than that of ⟨110⟩-oriented NW arrayed counterparts, which can be interpreted by the different surface Fermi level pinning that exists on various NW crystal surface planes due to the different As dangling bond densities. All this indicates the profound effect of NW crystal orientation on physical and chemical properties of GaAs NWs, suggesting the careful NW design considerations for achieving optimal photovoltaic performances. The approach presented here could also serve as a versatile and powerful platform for in situ characterization of other NW materials.

Fabrication of flexible silver nanowire conductive films and transmittance improvement based on moth-eye nanostructure array

NASA Astrophysics Data System (ADS)

Zhang, Chengpeng; Zhu, Yuwen; Yi, Peiyun; Peng, Linfa; Lai, Xinmin

2017-07-01

Transparent conductive electrodes (TCEs) are widely used in optoelectronic devices, such as touch screens, liquid-crystal displays and light-emitting diodes. To date, the material of the most commonly used TCEs was indium-tin oxide (ITO), which had several intrinsic drawbacks that limited its applications in the long term, including relatively high material cost and brittleness. Silver nanowire (AgNW), as one of the alternative materials for ITO TCEs, has already gained much attention all over the world. In this paper, we reported a facile method to greatly enhance the transmittance of the AgNW TCEs without reducing the electrical conductivity based on moth-eye nanostructures, and the moth-eye nanostructures were fabricated by using a roll-to-roll ultraviolet nanoimprint lithography process. Besides, the effects of mechanical pressure and bending on the moth-eye nanostructure layer were also investigated. In the research, the optical transmittance of the flexible AgNW TCEs was enhanced from 81.3% to 86.0% by attaching moth-eye nanostructures onto the other side of the flexible polyethylene terephthalate substrate while the electrical conductivity of the AgNW TCEs was not sacrificed. This research can provide a direction for the cost-effective fabrication of moth-eye nanostructures and the transmittance improvement of the flexible transparent electrodes.

Optical spectroscopy of arrays of Ag-Au nanoparticles obtained by vacuum-thermal evaporation

NASA Astrophysics Data System (ADS)

Gromov, D. G.; Mel'nikov, I. V.; Savitskii, A. I.; Trifonov, A. Yu.; Redichev, E. N.; Astapenko, V. A.

2017-03-01

The possibility of creating irregular arrays of bimetallic Ag-Au nanoparticles is investigated. The ability to manipulate their optical properties based on the simple engineering processes of thermal spraying followed by low-temperature annealing is demonstrated.

Resonant features of the terahertz generation in semiconductor nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trukhin, V. N., E-mail: valera.truchin@mail.ioffe.ru; Bouravleuv, A. D.; Mustafin, I. A.

2016-12-15

The paper presents the results of experimental studies of the generation of terahertz radiation in periodic arrays of GaAs nanowires via excitation by ultrashort optical pulses. It is found that the generation of THz radiation exhibits resonant behavior due to the resonant excitation of cylindrical modes in the nanowires. At the optimal geometric parameters of the nanowire array, the generation efficiency is found to be higher than that for bulk p-InAs, which is one of the most effective coherent terahertz emitters.

Superplastic Creep of Metal Nanowires from Rate-Dependent Plasticity Transition.

PubMed

Tao, Weiwei; Cao, Penghui; Park, Harold S

2018-05-22

Understanding the time-dependent mechanical behavior of nanomaterials such as nanowires is essential to predict their reliability in nanomechanical devices. This understanding is typically obtained using creep tests, which are the most fundamental loading mechanism by which the time-dependent deformation of materials is characterized. However, due to existing challenges facing both experimentalists and theorists, the time-dependent mechanical response of nanowires is not well-understood. Here, we use atomistic simulations that can access experimental time scales to examine the creep of single-crystal face-centered cubic metal (Cu, Ag, Pt) nanowires. We report that both Cu and Ag nanowires show significantly increased ductility and superplasticity under low creep stresses, where the superplasticity is driven by a rate-dependent transition in defect nucleation from twinning to trailing partial dislocations at the micro- or millisecond time scale. The transition in the deformation mechanism also governs a corresponding transition in the stress-dependent creep time at the microsecond (Ag) and millisecond (Cu) time scales. Overall, this work demonstrates the necessity of accessing time scales that far exceed those seen in conventional atomistic modeling for accurate insights into the time-dependent mechanical behavior and properties of nanomaterials.

Light-Trapping Characteristics of Ag Nanoparticles for Enhancing the Energy Conversion Efficiency of Hybrid Solar Cells.

PubMed

Fan, Zhiqiang; Zhang, Weijia; Ma, Qiang; Yan, Lanqin; Xu, Lihua; Fu, Yaolong

2017-10-18

In this paper, we investigated the optical and electrical characteristics of hybrid solar cells using silicon pyramid/Ag nanoparticle and nanowire/Ag nanoparticle nanocomposite structures, which are obtained by the Ag-assisted electroless etching method. We introduced the application of the physical and chemical properties of Ag nanoparticles on four kinds of solar cells: silicon pyramid, silicon pyramid/PEDOT:PSS, silicon nanowire, and silicon nanowire/PEDOT:PSS. We simulated the absorption of these structures for different parameters. Furthermore, we also show the result of the current density-voltage (J-V) characterization of the sample with Ag nanoparticles, which exhibits an improvement of the power conversion efficiency (PCE) in contrast to the samples without Ag nanoparticles. It was found that the properties of light-trapping of Ag nanoparticles have a prominent impact on improving the PCE of hybrid solar cells.

Single-mode plasmonic waveguiding properties of metal nanowires with dielectric substrates.

PubMed

Wang, Yipei; Ma, Yaoguang; Guo, Xin; Tong, Limin

2012-08-13

Single-mode plasmonic waveguiding properties of metal nanowires with dielectric substrates are investigated using a finite-element method. Au and Ag are selected as plasmonic materials for nanowire waveguides with diameters down to 5-nm-level. Typical dielectric materials with relatively low to high refractive indices, including magnesium fluoride (MgF2), silica (SiO2), indium tin oxide (ITO) and titanium dioxide (TiO2), are used as supporting substrates. Basic waveguiding properties, including propagation constants, power distributions, effective mode areas, propagation distances and losses are obtained at the typical plasmonic resonance wavelength of 660 nm. Compared to that of a freestanding nanowire, the mode area of a substrate-supported nanowire could be much smaller while maintaining an acceptable propagation length. For example, the mode area and propagation length of a 100-nm-diameter Ag nanowire with a MgF2 substrate are about 0.004 μm2 and 3.4 μm, respectively. The dependences of waveguiding properties on geometric and material parameters of the nanowire-substrate system are also provided. Our results may provide valuable references for waveguiding dielectric-supported metal nanowires for practical applications.

High speed superconducting nanowire single-photon detector with nine interleaved nanowires

NASA Astrophysics Data System (ADS)

Huang, Jia; Zhang, Weijun; You, Lixing; Zhang, Chengjun; Lv, Chaolin; Wang, Yong; Liu, Xiaoyu; Li, Hao; Wang, Zhen

2018-07-01

Count rate (CR) is one of the key parameters of superconducting nanowire single-photon detectors (SNSPDs). The practical SNSPDs usually have a CR of a few MHz to a few tens of MHz owing to the large kinetic inductance originating from the long nanowire, which is necessary for effectively coupling the photons. A feasible approach to decrease the kinetic inductance and consequently increase the detection speed is to replace a long single nanowire with multiple individual nanowires in an array. In this study, we report an SNSPD of nine interleaved nanowires with 70% system detection efficiency (SDE) and 200 Hz dark count rate at the low-photon-flux limit of 1550 nm. Owing to the small dead time (<6 ns) of each nanowire, the SNSPD achieved a maximum CR of 0.93 GHz at a photon flux of 1.26 × 1010 photons s‑1 with an SDE of ∼7.4%, and a CR of 200 MHz with an SDE of over 50%. Furthermore, a photon number resolvability of up to nine photons was also demonstrated.

Hierarchical Nanocomposites of Polyaniline Nanowire Arrays on Reduced Graphene Oxide Sheets for Supercapacitors

PubMed Central

Wang, Li; Ye, Yinjian; Lu, Xingping; Wen, Zhubiao; Li, Zhuang; Hou, Haoqing; Song, Yonghai

2013-01-01

Here we reported a novel route to synthesize a hierarchical nanocomposite (PANI-frGO) of polyaniline (PANI) nanowire arrays covalently bonded on reduced graphene oxide (rGO). In this strategy, nitrophenyl groups were initially grafted on rGO via C-C bond, and then reduced to aminophenyl to act as anchor sites for the growth of PANI arrays on rGO. The functionalized process was confirmed by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and thermogravimetric analysis. The electrochemical properties of the PANI-frGO as supercapacitor materials were investigated. The PANI-frGO nanocomposites showed high capacitance of 590 F g−1 at 0.1 A g−1, and had no loss of capacitance after 200 cycles at 2 A g−1. The improved electrochemical performance suggests promising application of the PANI-frGO nanocomposites in high-performance supercapacitors. PMID:24356535

Hierarchical Nanocomposites of Polyaniline Nanowire Arrays on Reduced Graphene Oxide Sheets for Supercapacitors

NASA Astrophysics Data System (ADS)

Wang, Li; Ye, Yinjian; Lu, Xingping; Wen, Zhubiao; Li, Zhuang; Hou, Haoqing; Song, Yonghai

2013-12-01

Here we reported a novel route to synthesize a hierarchical nanocomposite (PANI-frGO) of polyaniline (PANI) nanowire arrays covalently bonded on reduced graphene oxide (rGO). In this strategy, nitrophenyl groups were initially grafted on rGO via C-C bond, and then reduced to aminophenyl to act as anchor sites for the growth of PANI arrays on rGO. The functionalized process was confirmed by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and thermogravimetric analysis. The electrochemical properties of the PANI-frGO as supercapacitor materials were investigated. The PANI-frGO nanocomposites showed high capacitance of 590 F g-1 at 0.1 A g-1, and had no loss of capacitance after 200 cycles at 2 A g-1. The improved electrochemical performance suggests promising application of the PANI-frGO nanocomposites in high-performance supercapacitors.

Hierarchical nanocomposites of polyaniline nanowire arrays on reduced graphene oxide sheets for supercapacitors.

PubMed

Wang, Li; Ye, Yinjian; Lu, Xingping; Wen, Zhubiao; Li, Zhuang; Hou, Haoqing; Song, Yonghai

2013-12-20

Here we reported a novel route to synthesize a hierarchical nanocomposite (PANI-frGO) of polyaniline (PANI) nanowire arrays covalently bonded on reduced graphene oxide (rGO). In this strategy, nitrophenyl groups were initially grafted on rGO via C-C bond, and then reduced to aminophenyl to act as anchor sites for the growth of PANI arrays on rGO. The functionalized process was confirmed by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and thermogravimetric analysis. The electrochemical properties of the PANI-frGO as supercapacitor materials were investigated. The PANI-frGO nanocomposites showed high capacitance of 590 F g(-1) at 0.1 A g(-1), and had no loss of capacitance after 200 cycles at 2 A g(-1). The improved electrochemical performance suggests promising application of the PANI-frGO nanocomposites in high-performance supercapacitors.

Electrical and Optical Characterization of Nanowire based Semiconductor Devices

NASA Astrophysics Data System (ADS)

Ayvazian, Talin

This research project is focused on a new strategy for the creation of nanowire based semiconductor devices. The main goal is to understand and optimize the electrical and optical properties of two types of nanoscale devices; in first type lithographically patterned nanowire electrodeposition (LPNE) method has been utilized to fabricate nanowire field effect transistors (NWFET) and second type involved the development of light emitting semiconductor nanowire arrays (NWLED). Field effect transistors (NWFETs) have been prepared from arrays of polycrystalline cadmium selenide (pc-CdSe) nanowires using a back gate configuration. pc-CdSe nanowires were fabricated using the lithographically patterned nanowire electrode- position (LPNE) process on SiO2 /Si substrates. After electrodeposition, pc-CdSe nanowires were thermally annealed at 300 °C x 4 h either with or without exposure to CdCl 2 in methanol a grain growth promoter. The influence of CdCl2 treatment was to increase the mean grain diameter as determined by X-ray diffraction pattern and to convert the crystal structure from cubic to wurtzite. Transfer characteristics showed an increase of the field effect mobility (mu eff) by an order of magnitude and increase of the Ion/I off ratio by a factor of 3-4. Light emitting devices (NW-LED) based on lithographically patterned pc-CdSe nanowire arrays have been investigated. Electroluminescence (EL) spectra of CdSe nanowires under various biases exhibited broad emission spectra centered at 750 nm close to the band gap of CdSe (1.7eV). To enhance the intensity of the emitted light and the external quantum efficiency (EQE), the distance between the contacts were reduced from 5 mum to less than 1 mum which increased the efficiency by an order of magnitude. Also, increasing the annealing temperature of nanowires from 300 °C x4 h to 450 This research project is focused on a new strategy for the creation of nanowire based semiconductor devices. The main goal is to understand

Structure evolution of self-catalyzed grown Au, Ag and their alloy nanostructure

NASA Astrophysics Data System (ADS)

Zhu, Zhu; Chen, Feng; Xu, Chunxiang; Yang, Guangcan; Zhu, Ye; Luo, Zhaoxu

2017-12-01

Monitoring the nucleation and growth of nanomaterials is a key technique for material synthesis design and control. An efficient fabrication method can be realized deeply understanding the growth mechanisms. Here, noble metal nanostructures, gold (Au) nanoparticles, silver nanostructures (Ag nanoparticles/Ag nanowires) and gold-silver alloy nanoparticles were prepared in a facile method at room temperature. The growth processes of the Au nanoparticles, Ag nanowires and Au-Ag alloy nanoparticles can be monitored real-timely through the ultraviolet visible absorption (UV-vis), dynamic light scattering (DLS) and transmission electron microscopy (TEM). It is found that the whole formation involved Digestive ripening and Ostwald ripening cooperative mechanism. Furthermore, the self-assembly growth is noticed in the oriented attachment of precursor Ag monomers into nanowires under the same synthetic conditions without external templates or rigorous conditions. This result can provide a platform to discover the underlying growth mechanism of wet-chemistry methods for metal nanostructure fabrication.

Effect of Refractive Index of Substrate on Fabrication and Optical Properties of Hybrid Au-Ag Triangular Nanoparticle Arrays

PubMed Central

Liu, Jing; Chen, Yushan; Cai, Haoyuan; Chen, Xiaoyi; Li, Changwei; Yang, Cheng-Fu

2015-01-01

In this study, the nanosphere lithography (NSL) method was used to fabricate hybrid Au-Ag triangular periodic nanoparticle arrays. The Au-Ag triangular periodic arrays were grown on different substrates, and the effect of the refractive index of substrates on fabrication and optical properties was systematically investigated. At first, the optical spectrum was simulated by the discrete dipole approximation (DDA) numerical method as a function of refractive indexes of substrates and mediums. Simulation results showed that as the substrates had the refractive indexes of 1.43 (quartz) and 1.68 (SF5 glass), the nanoparticle arrays would have better refractive index sensitivity (RIS) and figure of merit (FOM). Simulation results also showed that the peak wavelength of the extinction spectra had a red shift when the medium’s refractive index n increased. The experimental results also demonstrated that when refractive indexes of substrates were 1.43 and 1.68, the nanoparticle arrays and substrate had better adhesive ability. Meanwhile, we found the nanoparticles formed a large-scale monolayer array with the hexagonally close-packed structure. Finally, the hybrid Au-Ag triangular nanoparticle arrays were fabricated on quartz and SF5 glass substrates and their experiment extinction spectra were compared with the simulated results.

Parameter optimization for Ag-coated TiO2 nanotube arrays as recyclable SERS substrates

NASA Astrophysics Data System (ADS)

Sun, Yuyang; Yang, Lulu; Liao, Fan; Dang, Qian; Shao, Mingwang

2018-06-01

The Ag-coated titanium dioxide nanotube arrays (Ag-coated TNTs) are obtained via the deposition of Ag nanoparticles on the two-step anodized TNTs. The wall thickness of TNTs is modulated via finite difference time domain simulation to get the favorable electromagnetic field for surface enhanced Raman scattering (SERS). Ag-coated TNTs with optimal wall thickness of 20 nm were employed as the SERS substrates to detect 2-mercaptobenzoxazole, which show superior detection sensitivity and uniformity. In addition, due to the photocatalysis of TNTs, the SERS substrates could clean themselves and be repeatedly used by photo-degradation of target molecules under the ultra-violet irradiation. The Ag-coated TNTs are a kind of bifunctional SERS substrates which can produce high-quality SERS signals and reuse to reduce the cost.

Development of a conformable electronic skin based on silver nanowires and PDMS

NASA Astrophysics Data System (ADS)

Wang, Haopeng

2017-06-01

This paper presented the designed and tested a flexible and stretchable pressure sensor array that could be used to cover 3D surface to measure contact pressure. The sensor array is laminated into a thin film with 1 mm in thickness and can easily be stretched without losing its functionality. The fabricated sensor array contained 8×8 sensing elements, each could measure the pressure up to 180 kPa. An improved sandwich structure is used to build the sensor array. The upper and lower layers were PDMS thin films embedded with conductor strips formed by PDMS-based silver nanowires (AgNWs) networks covered with nano-scale thin metal film. The middle layer was formed a porous PDMS film inserted with circular conductive rubber. The sensor array could detect the contact pressure within 30% stretching rate. In this paper, the performance of the pressure sensor array was systematically studied. With the corresponding scanning power-supply circuit and data acquisition system, it is demonstrated that the system can successfully capture the tactile images induced by objects of different shapes. Such sensor system could be applied on complex surfaces in robots or medical devices for contact pressure detection and feedback.

Shape Evolution of Highly Lattice-Mismatched InN/InGaN Nanowire Heterostructures