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Sample records for high ordered nanoporous

  1. Engineering of highly ordered TiO2 nanopore arrays by anodization

    NASA Astrophysics Data System (ADS)

    Wang, Huijie; Huang, Zhennan; Zhang, Li; Ding, Jie; Ma, Zhaoxia; Liu, Yong; Kou, Shengzhong; Yang, Hangsheng

    2016-07-01

    Finite element analysis was used to simulate the current density distributions in the TiO2 barrier layer formed at the initial stage of Ti anodization. The morphology modification of the barrier layer was found to induce current density distribution change. By starting the anodization with proper TiO2 barrier layer morphology, the current density distribution can be adjusted to favor the formation of either nanotube arrays or nanopore arrays of anodic TiO2. We also found that the addition of sodium acetate into the electrolyte suppressed both the field-assisted chemical dissolution of TiO2 and the TiF62- hydrolysis induced TiO2 deposition during anodization, and thus further favored the nanopore formation. Accordingly, highly ordered anodic TiO2 nanopore arrays, similar to anodic aluminum oxide nanopore arrays, were successfully prepared.

  2. Highly Efficient Elimination of Carbon Monoxide with Binary Copper-Manganese Oxide Contained Ordered Nanoporous Silicas

    NASA Astrophysics Data System (ADS)

    Lee, Jiho; Kim, Hwayoun; Lee, Hyesun; Jang, Seojun; Chang, Jeong Ho

    2016-01-01

    Ordered nanoporous silicas containing various binary copper-manganese oxides were prepared as catalytic systems for effective carbon monoxide elimination. The carbon monoxide elimination efficiency was demonstrated as a function of the [Mn]/[Cu] ratio and reaction time. The prepared catalysts were characterized by Brunauer-Emmett-Teller (BET) method, small- and wide-angle X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HR-TEM) for structural analysis. Moreover, quantitative analysis of the binary metal oxides within the nanoporous silica was achieved by inductively coupled plasma (ICP). The binary metal oxide-loaded nanoporous silica showed high room temperature catalytic efficiency with over 98 % elimination of carbon monoxide at higher concentration ratio of [Mn]/[Cu].

  3. Highly Efficient Elimination of Carbon Monoxide with Binary Copper-Manganese Oxide Contained Ordered Nanoporous Silicas.

    PubMed

    Lee, Jiho; Kim, Hwayoun; Lee, Hyesun; Jang, Seojun; Chang, Jeong Ho

    2016-12-01

    Ordered nanoporous silicas containing various binary copper-manganese oxides were prepared as catalytic systems for effective carbon monoxide elimination. The carbon monoxide elimination efficiency was demonstrated as a function of the [Mn]/[Cu] ratio and reaction time. The prepared catalysts were characterized by Brunauer-Emmett-Teller (BET) method, small- and wide-angle X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HR-TEM) for structural analysis. Moreover, quantitative analysis of the binary metal oxides within the nanoporous silica was achieved by inductively coupled plasma (ICP). The binary metal oxide-loaded nanoporous silica showed high room temperature catalytic efficiency with over 98 % elimination of carbon monoxide at higher concentration ratio of [Mn]/[Cu]. PMID:26744146

  4. Bacteria repelling on highly-ordered alumina-nanopore structures

    PubMed Central

    Kim, Sunghan; Cirillo, Jeffrey D.; Polycarpou, Andreas A.; Liang, Hong

    2015-01-01

    Bacteria introduce diseases and infections to humans by their adherence to biomaterials, such as implants and surgical tools. Cell desorption is an effective step to reduce such damage. Here, we report mechanisms of bacteria desorption. An alumina nanopore structure (ANS) with pore size of 35 nm, 55 nm, 70 nm, and 80 nm was used as substrate to grow Escherichia coli (E. coli) cells. A bacteria repelling experimental method was developed to quantitatively evaluate the area percentage of adherent bacterial cells that represent the nature of cell adhesion as well as desorption. Results showed that there were two crucial parameters: contact angle and contact area that affect the adhesion/desorption. The cells were found to be more easily repelled when the contact angle increased. The area percentage of adherent bacterial cells decreased with the decrease in the contact area of a cell on ANS. This means that cell accessibility on ANS depends on the contact area. This research reveals the effectiveness of the nanopored structures in repelling cells. PMID:25944966

  5. Bacteria repelling on highly-ordered alumina-nanopore structures

    NASA Astrophysics Data System (ADS)

    Kim, Sunghan; Zhou, Yan; Cirillo, Jeffrey D.; Polycarpou, Andreas A.; Liang, Hong

    2015-04-01

    Bacteria introduce diseases and infections to humans by their adherence to biomaterials, such as implants and surgical tools. Cell desorption is an effective step to reduce such damage. Here, we report mechanisms of bacteria desorption. An alumina nanopore structure (ANS) with pore size of 35 nm, 55 nm, 70 nm, and 80 nm was used as substrate to grow Escherichia coli (E. coli) cells. A bacteria repelling experimental method was developed to quantitatively evaluate the area percentage of adherent bacterial cells that represent the nature of cell adhesion as well as desorption. Results showed that there were two crucial parameters: contact angle and contact area that affect the adhesion/desorption. The cells were found to be more easily repelled when the contact angle increased. The area percentage of adherent bacterial cells decreased with the decrease in the contact area of a cell on ANS. This means that cell accessibility on ANS depends on the contact area. This research reveals the effectiveness of the nanopored structures in repelling cells.

  6. Designing 3D highly ordered nanoporous CuO electrodes for high-performance asymmetric supercapacitors.

    PubMed

    Moosavifard, Seyyed E; El-Kady, Maher F; Rahmanifar, Mohammad S; Kaner, Richard B; Mousavi, Mir F

    2015-03-01

    The increasing demand for energy has triggered tremendous research efforts for the development of lightweight and durable energy storage devices. Herein, we report a simple, yet effective, strategy for high-performance supercapacitors by building three-dimensional pseudocapacitive CuO frameworks with highly ordered and interconnected bimodal nanopores, nanosized walls (∼4 nm) and large specific surface area of 149 m(2) g(-1). This interesting electrode structure plays a key role in providing facilitated ion transport, short ion and electron diffusion pathways and more active sites for electrochemical reactions. This electrode demonstrates excellent electrochemical performance with a specific capacitance of 431 F g(-1) (1.51 F cm(-2)) at 3.5 mA cm(-2) and retains over 70% of this capacitance when operated at an ultrafast rate of 70 mA cm(-2). When this highly ordered CuO electrode is assembled in an asymmetric cell with an activated carbon electrode, the as-fabricated device demonstrates remarkable performance with an energy density of 19.7 W h kg(-1), power density of 7 kW kg(-1), and excellent cycle life. This work presents a new platform for high-performance asymmetric supercapacitors for the next generation of portable electronics and electric vehicles. PMID:25671715

  7. A Simple Route to Highly Oriented and Ordered Nanoporous Block Copolymer Templates

    SciTech Connect

    Park,S.; Wang, J.; Kim, B.; Xu, J.; Russell, T.

    2008-01-01

    Controlling the orientation and lateral ordering of the block copolymer microdomains is essential to their use as templates and scaffolds for the fabrication of nanostructured materials. In addition, a process must be robust, simple to implement, and rapid, and should not introduce disruptive processing steps that would impede their use. Here, we describe thin films of poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) diblock copolymers, spin-coated from mixed solvents that show highly oriented, cylindrical microdomains with a high degree of order on a wide range of substrates, including silicon oxide, polystyrene, germanium, polyimide, and poly(butylene terephthalate). In addition, the preferential solvation of the P4VP block with an alcohol caused a surface reconstruction that resulted in the formation of a nanoporous film upon drying. The evaporation of gold onto the reconstructed films produced thermally stable and reactive ion etching resistant films.

  8. Highly ordered nanoporous films from supramolecular diblock copolymers with hydrogen-bonding junctions.

    PubMed

    Montarnal, Damien; Delbosc, Nicolas; Chamignon, Cécile; Virolleaud, Marie-Alice; Luo, Yingdong; Hawker, Craig J; Drockenmuller, Eric; Bernard, Julien

    2015-09-14

    We designed efficient precursors that combine complementary associative groups with exceptional binding affinities and thiocarbonylthio moieties enabling precise RAFT polymerization. Well defined PS and PMMA supramolecular polymers with molecular weights up to 30 kg mol(-1) are synthesized and shown to form highly stable supramolecular diblock copolymers (BCPs) when mixed, in non-polar solvents or in the bulk. Hierarchical self-assembly of such supramolecular BCPs by thermal annealing affords morphologies with excellent lateral order, comparable to features expected from covalent diblock copolymer analogues. Simple washing of the resulting materials with protic solvents disrupts the supramolecular association and selectively dissolves one polymer, affording a straightforward process for preparing well-ordered nanoporous materials without resorting to crosslinking or invasive chemical degradations. PMID:26234749

  9. Impedance spectroscopy of highly ordered nano-porous electrodes based on Au-AAO (anodic aluminum oxide) structure.

    PubMed

    Ahn, Jaehwan; Cho, Sungbo; Min, Junhong

    2013-11-01

    Electrochemical measurements using the microelectrodes are increasingly utilized for the label-free detection of the small amount of biological materials such as DNA, protein, and cells. However, the interfacial electrode impedance increases and may hinder the detection of weak signals as the size of electrode decreases. To enhance the measurement sensitivity while reducing the electrode size, in this study, microelectrodes employing a nanoporous structure were fabricated and characterized by using electrical impedance spectroscopy. We made the highly ordered honeycomb nanoporous structure of Anodic Aluminum Oxide (AAO) by electrochemical anodizing and formed Au layer on the surface of AAO (Au/AAO) by electroless Au plating method. The electrical characteristics of the fabricated Au/AAO electrodes were evaluated by using de Levie's model derived for the pore electrodes. As a result, the interfacial electrode impedance of the fabricated Au/AAO electrodes was 2-3 order lower than the value of the planar electrodes at frequencies below 1 kHz. It implies this nanoporous electrode could be directly applied to label free detection of biomaterials. PMID:24245278

  10. Influence of Anodic Conditions on Self-ordered Growth of Highly Aligned Titanium Oxide Nanopores

    PubMed Central

    2007-01-01

    Self-aligned nanoporous TiO2templates synthesized via dc current electrochemical anodization have been carefully analyzed. The influence of environmental temperature during the anodization, ranging from 2 °C to ambient, on the structure and morphology of the nanoporous oxide formation has been investigated, as well as that of the HF electrolyte chemical composition, its concentration and their mixtures with other acids employed for the anodization. Arrays of self-assembled titania nanopores with inner pores diameter ranging between 50 and 100 nm, wall thickness around 20–60 nm and 300 nm in length, are grown in amorphous phase, vertical to the Ti substrate, parallel aligned to each other and uniformly disordering distributed over all the sample surface. Additional remarks about the photoluminiscence properties of the titania nanoporous templates and the magnetic behavior of the Ni filled nanoporous semiconductor Ti oxide template are also included.

  11. Ordered arrays of nanoporous silicon nanopillars and silicon nanopillars with nanoporous shells

    PubMed Central

    2013-01-01

    The fabrication of ordered arrays of nanoporous Si nanopillars with and without nanoporous base and ordered arrays of Si nanopillars with nanoporous shells are presented. The fabrication route is using a combination of substrate conformal imprint lithography and metal-assisted chemical etching. The metal-assisted chemical etching is performed in solutions with different [HF]/[H2O2 + HF] ratios. Both pore formation and polishing (marked by the vertical etching of the nanopillars) are observed in highly doped and lightly doped Si during metal-assisted chemical etching. Pore formation is more active in the highly doped Si, while the transition from polishing to pore formation is more obvious in the lightly doped Si. The etching rate is clearly higher in the highly doped Si. Oxidation occurs on the sidewalls of the pillars by etching in solutions with small [HF]/[H2O2 + HF] ratios, leading to thinning, bending, and bonding of pillars. PMID:23336430

  12. Highly ordered nanoporous carbon films with tunable pore diameters and their excellent sensing properties.

    PubMed

    Jia, Lichao; Lawrence, Geoffrey; Balasubramanian, V V; Choi, Goeun; Choy, Jin-Ho; Abdullah, Aboubakr M; Elzatahry, Ahmed; Ariga, Katsuhiko; Vinu, Ajayan

    2015-01-01

    Ordered porous carbon films with tunable pore diameters, immobilized with glucose oxidase (GOD) have been fabricated and employed for the construction of a biosensor for glucose molecules. The as-prepared porous films have large specific surface areas and highly ordered porous structure with uniform pore sizes, which are critical for the immobilization of large amounts of GOD and support the promotion of heterogeneous electron transfer. The developed biosensors give enough room for the encapsulation of a high amount of GOD molecules and show excellent biosensing performance with a linear response to glucose concentration ranging from 0.5 to 9 mM and a detection limit of 1.5 μM. It is also demonstrated that the sensitivity of the biosensor can be easily tuned by modulating the pore size of carbon film as it dictates the amount of immobilization of GOD in the porous channels. The fabricated carbon-film-based biosensor has a good stability and a high reproducibility, which opens the gateway for the commercialization of this excellent technology. PMID:25394330

  13. Ordered arrays of patterned nanoporous silicon

    NASA Astrophysics Data System (ADS)

    Wang, D.; Schönherr, S.; Ji, R.; Herz, A.; Ronning, C.; Schaaf, P.

    2013-07-01

    The fabrication of ordered arrays of patterned nanoporous Si with two-level nanostructures using a combination of metal-assisted chemical etching and nanoimprint lithography is presented. One nanostructure is the periodic arrays of holes and pillars with a period of several hundred nanometers and another nanostructure is the nanoporosity with a pore size of about 10 nm. The etching rate of (1 0 0) oriented Si is clearly higher than that of (1 1 0) and (1 1 1) oriented Si under the same conditions. More effective pore formation occurs in (1 1 1) oriented Si than in (1 0 0) and (1 1 0) oriented Si. Cathodoluminescence was measured and the patterned array of nanoporous Si shows visible luminescence with an overlap of two red emission bands at room temperature.

  14. High Density Methane Storage in Nanoporous Carbon

    NASA Astrophysics Data System (ADS)

    Rash, Tyler; Dohnke, Elmar; Soo, Yuchoong; Maland, Brett; Doynov, Plamen; Lin, Yuyi; Pfeifer, Peter; Mriglobal Collaboration; All-Craft Team

    2014-03-01

    Development of low-pressure, high-capacity adsorbent based storage technology for natural gas (NG) as fuel for advanced transportation (flat-panel tank for NG vehicles) is necessary in order to address the temperature, pressure, weight, and volume constraints present in conventional storage methods (CNG & LNG.) Subcritical nitrogen adsorption experiments show that our nanoporous carbon hosts extended narrow channels which generate a high surface area and strong Van der Waals forces capable of increasing the density of NG into a high-density fluid. This improvement in storage density over compressed natural gas without an adsorbent occurs at ambient temperature and pressures ranging from 0-260 bar (3600 psi.) The temperature, pressure, and storage capacity of a 40 L flat-panel adsorbed NG tank filled with 20 kg of nanoporous carbon will be featured.

  15. Plasmonic devices and sensors built from ordered nanoporous materials.

    SciTech Connect

    Jacobs, Benjamin W.; Kobayashi, Yoji; Houk, Ronald J. T.; Allendorf, Mark D.; Long, Jeffrey R.; Robertson, Ian M.; House, Stephen D.; Graham, Dennis D.; Talin, Albert Alec; Chang, Noel N.; El Gabaly Marquez, Farid

    2009-09-01

    The objective of this project is to lay the foundation for using ordered nanoporous materials known as metal-organic frameworks (MOFs) to create devices and sensors whose properties are determined by the dimensions of the MOF lattice. Our hypothesis is that because of the very short (tens of angstroms) distances between pores within the unit cell of these materials, enhanced electro-optical properties will be obtained when the nanopores are infiltrated to create nanoclusters of metals and other materials. Synthetic methods used to produce metal nanoparticles in disordered templates or in solution typically lead to a distribution of particle sizes. In addition, creation of the smallest clusters, with sizes of a few to tens of atoms, remains very challenging. Nanoporous metal-organic frameworks (MOFs) are a promising solution to these problems, since their long-range crystalline order creates completely uniform pore sizes with potential for both steric and chemical stabilization. We report results of synthetic efforts. First, we describe a systematic investigation of silver nanocluster formation within MOFs using three representative MOF templates. The as-synthesized clusters are spectroscopically consistent with dimensions {le} 1 nm, with a significant fraction existing as Ag{sub 3} clusters, as shown by electron paramagnetic resonance. Importantly, we show conclusively that very rapid TEM-induced MOF degradation leads to agglomeration and stable, easily imaged particles, explaining prior reports of particles larger than MOF pores. These results solve an important riddle concerning MOF-based templates and suggest that heterostructures composed of highly uniform arrays of nanoparticles within MOFs are feasible. Second, a preliminary study of methods to incorporate fulleride (K{sub 3}C{sub 60}) guest molecules within MOF pores that will impart electrical conductivity is described.

  16. Highly cross-linked nanoporous polymers

    DOEpatents

    Steckle, Jr., Warren P.; Apen, Paul G.; Mitchell, Michael A.

    1997-01-01

    Condensation polymerization followed by a supercritical extraction step can be used to obtain highly cross-linked nanoporous polymers with high surface area, controlled pore sizes and rigid structural integrity. The invention polymers are useful for applications requiring separation membranes.

  17. Highly cross-linked nanoporous polymers

    DOEpatents

    Steckle, Jr., Warren P.; Apen, Paul G.; Mitchell, Michael A.

    1998-01-01

    Condensation polymerization followed by a supercritical extraction step can be used to obtain highly cross-linked nanoporous polymers with high surface area, controlled pore sizes and rigid structural integrity. The invention polymers are useful for applications requiring separation membranes.

  18. Role of sp3 Defect in Ordered Nanoporous Carbon

    NASA Astrophysics Data System (ADS)

    Xu, Enshi; Lueking, Angela; Crespi, Vincent; Lammert, Paul; Maleski, Kathleen

    Schwarzite is considered an ideal model for nanoporous carbon and is energetically more stable than fullerene. However, carbon don't form well-ordered Schwarzite-type nanoporous material possibly due to kinetic arrests under pyrolytic conditions. We computationally discovered a new thermodynamically stable local defect in carbon sp2 networks: an sp3 carbon defect, which inspires new solutions to the problem. The defect is most stable in nanoporous carbon (i.e., networks with negative curvatures, known as Schwarzites) and its topological merit, carrying negative curvature, results in the design of new model structures of nanoporous materials (periodic, negatively-curved networks), and provides a handle of the negative curvature carrier in nanoporous carbon, and we propose a kinetics-dominated synthetic route to novel nanoporous carbon with long range order by controlling the sp3 defect through sp3 carbon atom injection or Si atom substitution, with the aid of first principle molecular dynamics simulation. Calculations also suggest the defect can be observed by Raman.

  19. High-resolution dielectric study reveals pore-size-dependent orientational order of a discotic liquid crystal confined in tubular nanopores.

    PubMed

    Całus, Sylwia; Kityk, Andriy V; Borowik, Lech; Lefort, Ronan; Morineau, Denis; Krause, Christina; Schönhals, Andreas; Busch, Mark; Huber, Patrick

    2015-07-01

    We report a high-resolution dielectric study on a pyrene-based discotic liquid crystal (DLC) in the bulk state and confined in parallel tubular nanopores of monolithic silica and alumina membranes. The positive dielectric anisotropy of the DLC molecule at low frequencies (in the quasistatic case) allows us to explore the thermotropic collective orientational order. A face-on arrangement of the molecular discs on the pore walls and a corresponding radial arrangement of the molecules is found. In contrast to the bulk, the isotropic-to-columnar transition of the confined DLC is continuous, shifts with decreasing pore diameter to lower temperatures, and exhibits a pronounced hysteresis between cooling and heating. These findings corroborate conclusions from previous neutron and x-ray-scattering experiments as well as optical birefringence measurements. Our study also indicates that the relative simple dielectric technique presented here is a quite efficient method in order to study the thermotropic orientational order of DLC-based nanocomposites. PMID:26274191

  20. Highly cross-linked nanoporous polymers

    DOEpatents

    Steckle, W.P. Jr.; Apen, P.G.; Mitchell, M.A.

    1998-01-20

    Condensation polymerization followed by a supercritical extraction step can be used to obtain highly cross-linked nanoporous polymers with high surface area, controlled pore sizes and rigid structural integrity. The invention polymers are useful for applications requiring separation membranes. 1 fig.

  1. High-throughput optical sensing of nucleic acids in a nanopore array

    PubMed Central

    Huang, Shuo; Romero-Ruiz, Mercedes; Castell, Oliver K.; Bayley, Hagan; Wallace, Mark I.

    2016-01-01

    Protein nanopores such as α-hemolysin and MspA can potentially be used to sequence long strands of DNA quickly and at low cost. In order to provide high-speed sequencing, large arrays of nanopores are required that allow the nanopores to individually addressed, but current nanopore sequencing methods rely on ionic current measurements and such methods are likely to prove difficult to scale up. Here, we show that, by optically encoding the ionic flux through protein nanopores, the discrimination of nucleic acid sequences and the detection of sequence-specific nucleic acid binding events can be parallelized. We make optical recordings at a density of ~104 nanopores per mm2 in a single droplet interface bilayer. Nanopore blockades can discriminate between DNAs with sub-pA equivalent resolution, and specific miRNA sequences can be identified by differences in unzipping kinetics. By creating an array of 2500 bilayers with a micro-patterned hydrogel chip, we are also able to load different samples into specific bilayers, suitable for high-throughput nanopore recording. PMID:26322943

  2. Effect of ordered intermediate porosity on ion transport in hierarchically nanoporous electrodes.

    PubMed

    Chae, Weon-Sik; Gough, Dara Van; Ham, Sung-Kyoung; Robinson, David B; Braun, Paul V

    2012-08-01

    The high surface area of nanoporous electrodes makes them promising for use in electrochemical double-layer supercapacitors, desalination and pollution remediation, and drug delivery applications. When designed well and operating near their peak power, their charging rates are limited by ion transport through their long, narrow pores. This can be alleviated by creating pores of intermediate diameter that penetrate the electrode. We have fabricated electrodes featuring these by creating colloidal crystal-templated opals of nanoporous gold formed by dealloying. The resulting electrodes contain a bimodal pore-size distribution, with large pores on the order of several 100 nm and small pores on the order of 10 nm. Electrochemical impedance spectrometry shows that porous gold opals sacrifice some capacitance, but possess a lower internal resistance, when compared to a porous gold electrode with only the smaller-diameter pores. The architectural flexibility of this approach provides a greater ability to design a balance between power density and energy density. PMID:22799397

  3. Ordered arrays of polymeric nanopores by using inverse nanostructured PTFE surfaces.

    PubMed

    Martín, Jaime; Martín-González, Marisol; del Campo, Adolfo; Reinosa, Julián J; Fernández, José Francisco

    2012-09-28

    We present a simple, efficient, and high-throughput methodology for the fabrication of ordered nanoporous polymeric surfaces with areas in the range of cm(2). The procedure is based on a two-stage replication of a master nanostructured pattern. The process starts with the preparation of an ordered array of poly(tetrafluoroethylene) (PTFE) free-standing nanopillars by wetting self-ordered porous anodic aluminum oxide templates with molten PTFE. The nanopillars are 120 nm in diameter and approximately 350 nm long, while the array extends over cm(2). The PTFE nanostructuring process induces surface hydrocarbonation of the nanopillars, as revealed by confocal Raman microscopy/spectroscopy, which enhances the wettability of the originally hydrophobic material and facilitates its subsequent use as an inverse pattern. Thus, the PTFE nanostructure is then used as a negative master for the fabrication of macroscopic hexagonal arrays of nanopores composed of biocompatible poly(vinylalcohol). In this particular case, the nanopores are 130-140 nm in diameter and the interpore distance is around 430 nm. Features of such characteristic dimensions are known to be easily recognized by living cells. Moreover, the inverse mold is not destroyed in the pore array demolding process and can be reused for further pore array fabrication. Therefore, the developed method allows the high-throughput production of cm(2)-scale biocompatible nanoporous surfaces that could be interesting as two-dimensional scaffolds for tissue repair or wound healing. Moreover, our approach can be extrapolated to the fabrication of almost any polymer and biopolymer ordered pore array. PMID:22948375

  4. Structural evolution of self-ordered alumina tapered nanopores with 100 nm interpore distance

    NASA Astrophysics Data System (ADS)

    Li, Juan; Li, Congshan; Gao, Xuefeng

    2011-10-01

    We in-detail investigated the profile evolution processes of highly ordered alumina under the cyclic treatment of mild anodizing of aluminum foils in oxalic acid followed by etching in phosphoric acid. With the cyclic times increasing, the profiles of nanopores were gradually evolved into the parabola-like, trumpet-like and conical shape. Although the inserted etching itself nearly had no impact on the growth rate of the nanopores due to the rapid recovering of thinned barrier layer at the initial stage of next anodizing, overmuch etching could bring apparent side effects such as wall-breaking, thinning and taper-removing from the top down. The anodizing and etching kinetics and their synergetic effects in modulating different aspect ratios and open sizes of conical pores were studied systematically. These findings are helpful to tailor high-quality anodic alumina taper-pores with tunable profiles.

  5. Fabrication of ordered nanoporous anodic alumina prepatterned by mold-assisted chemical etching

    PubMed Central

    2011-01-01

    In this article, a simple and cost-effective method to create patterned nanoindentations on Al surface via mold-assisted chemical etching process is demonstrated. This report shows the reaction-diffusion method which formed nanoscale shallow etch pits by the absorption/liberation behaviors of chemical etchant in poly(dimethylsiloxane) stamp. During subsequent anodization, it was possible to obtain the ordered nanopore arrays with 277 nm pitch that were guided by the prepatterned etch pits. The prepatterned etch pits obtained can guide the growth of AAO nanopores during anodization and facilitate the preparation of ordered nanopore arrays. PMID:21711706

  6. Modeling the specular spectral reflectance of partially ordered alumina nanopores on an aluminum substrate.

    PubMed

    Kuang, Dengfeng; Charrière, Renée; Matsapey, Natalia; Flury, Manuel; Faucheu, Jenny; Chavel, Pierre

    2015-02-23

    Anodizing of aluminum generates a porous alumina layer comprising cylindrical nanopores (300 nm diameter) extending essentially perpendicular to the substrate. The pore distribution over the surface exhibits a short-distance order close to hexagonal arrangement. On the contrary, long-distance order cannot be defined: the arrangement is not periodic. Visual observation of such nanoporous layers shows a reddish specular reflectance consistent with reflectance spectrum measurements. This work is a parametric study aiming at demonstrating that color effects are caused by the presence of disorder illustrated by the deviations from periodicity in terms of nanopore location and nanopore radius. Using the method of Rigorous Coupled Wave Analysis (RCWA), the reflectance spectrum has been simulated. Although our calculations were done using a simple one-dimensional (1D) model, a fair fit with experimental results is found. PMID:25836487

  7. Metallic muscles at work: high rate actuation in nanoporous gold/polyaniline composites.

    PubMed

    Detsi, Eric; Onck, Patrick; De Hosson, Jeff Th M

    2013-05-28

    Metallic muscles made of nanoporous metals suffer from serious drawbacks caused by the usage of an aqueous electrolyte for actuation. An aqueous electrolyte prohibits metallic muscles from operating in dry environments and hampers a high actuation rate due to the low ionic conductivity of electrolytes. In addition, redox reactions involved in electrochemical actuation severely coarsen the ligaments of nanoporous metals, leading to a substantial loss in performance of the actuator. Here we present an electrolyte-free approach to put metallic muscles to work via a metal/polymer interface. A nanocoating of polyaniline doped with sulfuric acid was grown onto the ligaments of nanoporous gold. Dopant sulfate anions coadsorbed into the polymer coating matrix were exploited to tune the nanoporous metal surface stress and subsequently generate macroscopic dimensional changes in the metal. Strain rates achieved in the single-component nanoporous metal/polymer composite actuator are 3 orders of magnitude higher than that of the standard three-component nanoporous metal/electrolyte hybrid actuator. PMID:23582044

  8. Biomimetic solution against dewetting in a highly hydrophobic nanopore.

    PubMed

    Picaud, Fabien; Paris, Guillaume; Gharbi, Tijani; Balme, Sébastien; Lepoitevin, Mathilde; Tangaraj, Vidhyadevi; Bechelany, Mikhael; Janot, Jean Marc; Balanzat, Emmanuel; Henn, François

    2016-06-14

    A water molecule is the foundation of life and is the primary compound in every living system. While many of its properties are understood in a bulk solvent, its behavior in a small hydrophobic nanopore still raises fundamental questions. For instance, a wetting/dewetting transition in a hydrophobic solid-state or a polymer nanopore occurs stochastically and can only be prevented by external physical stimuli. Controlling these transitions would be a primary requirement to improve many applications. Some biological channels, such as gramicidin A (gA) proteins, show a high rate of water and ion diffusion in their central subnanochannel while their external surface is highly hydrophobic. The diameter of this channel is significantly smaller than the inner size of the lowest artificial nanopore in which water drying occurs (i.e. 1.4 nm). In this paper, we propose an innovative idea to generate nanopore wetting as a result of which the application of an external field is no longer required. In a nanopore, the drying or wetting of the inner walls occurs randomly (in experiments and in simulations). However, we have shown how the confinement of gA, in a dried hydrophobic nanopore, rapidly generates a stable wetting of the latter. We believe that this simple idea, based on biomimetism, could represent a real breakthrough that could help to improve and develop new nanoscale applications. PMID:27157717

  9. Flow of methane in shale nanopores at low and high pressure by molecular dynamics simulations.

    PubMed

    Jin, Zhehui; Firoozabadi, Abbas

    2015-09-14

    Flow in shale nanopores may be vastly different from that in the conventional permeable media. In large pores and fractures, flow is governed by viscosity and pressure-driven. Convection describes the process. Pores in some shale media are in nanometer range. At this scale, continuum flow mechanism may not apply. Knudsen diffusion and hydrodynamic expressions such as the Hagen-Poiseuille equation and their modifications have been used to compute flow in nanopores. Both approaches may have drawbacks and can significantly underestimate molecular flux in nanopores. In this work, we use the dual control volume-grand canonical molecular dynamics simulations to investigate methane flow in carbon nanopores at low and high pressure conditions. Our simulations reveal that methane flow in a slit pore width of 1-4 nm can be more than one order of magnitude greater than that from Knudsen diffusion at low pressure and the Hagen-Poiseuille equation at high pressure. Knudsen diffusion and Hagen-Poiseuille equations do not account for surface adsorption and mobility of the adsorbed molecules, and inhomogeneous fluid density distributions. Mobility of molecules in the adsorbed layers significantly increases molecular flux. Molecular velocity profiles in nanopores deviate significantly from the Navier-Stokes hydrodynamic predictions. Our molecular simulation results are in agreement with the enhanced flow measurements in carbon nanotubes. PMID:26374043

  10. Direct imprinting of ordered and dense TiO 2 nanopore arrays by using a soft template for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Zhong, Peng; Que, Wenxiu; Hu, X.

    2011-09-01

    Highly ordered and dense TiO2 nanopore arrays are directly nanoimprinted on a transparent conductive glass substrate by using a polymethylmethacrylate/polydimethylsiloxane (PMMA/PDMS) composite soft template, which is replicated from an anodic aluminum oxide (AAO) replica mold. Results indicate that heat infiltration under vacuum conditions can ensure complete filling of PMMA into the AAO pores, and that free-standing PMMA nanorods with an aspect ratio more than 5 can be obtained by adjusting the AAO pore depth based on a freeze-drying technique. TiO2 nanopore arrays with different diameters from 30 to 300 nm and inter-pore distances between 70 and 450 nm can be easily fabricated by using the corresponding templates with different sizes. Preliminary solar cells are also assembled with a heterojunction of conjugated polymer/TiO2 nanopore arrays. Results indicate that the construction of poly-(3-hexylthiophene) (P3HT)/TiO2 nanopore arrays can be more helpful in quenching the PL emission of P3HT than that of P3HT/flat TiO2 film, and a maximum efficiency of about 0.32% can be obtained for a photovoltaic device with a TiO2/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM)/P3HT structure.

  11. Self-Ordered Nanoporous Alumina Templates Formed by Anodization of Aluminum in Oxalic Acid

    NASA Astrophysics Data System (ADS)

    Vida-Simiti, Ioan; Nemes, Dorel; Jumate, Nicolaie; Thalmaier, Gyorgy; Sechel, Niculina

    2012-10-01

    Anodic aluminum oxide (AAO) membranes with highly ordered nanopores serve as ideal templates for the formation of various nanostructured materials. The procedure of the template preparation is based on a two-step self-organized anodization of aluminum. In the current study, AAO templates were fabricated in 0.3 M oxalic acid under the anodizing potential range of 30-60 V at an electrolyte temperature of ~5°C. The AAO templates were analyzed using scanning electron microscopy, x-ray diffraction, Fourier-transform infrared spectroscopy, and differential thermal analysis. The as obtained layers are amorphous; the mean pore size is between 40 nm and 75 nm and increases with the increase of the anodization potential. Well-defined pores across the whole aluminum template, a pore density of ~1010 pores/cm2, and a tendency to form a porous structure with hexagonal symmetry were observed.

  12. The Core-Shell Approach to Formation of Ordered Nanoporous Materials

    SciTech Connect

    Chang, Jeong H.; Wang, Li Q.; Shin, Yongsoon; Jeong, Byeongmoon; Birnbaum, Jerome C.; Exarhos, Gregory J.

    2002-03-04

    This work describes a novel core-shell approach for the preparation of ordered nanoporous ceramic materials that involve a self-assembly process at the molecular level using MPEG-b-PDLLA bloack copolymers. This approach provides for rapid self-assembly and structural reorganization at room temperature. Selected MPEG-b-PDLLA block copolymers were synthesized with systematic variation of the chain lengths of the resident hydrophilic and hydrophobic blocks. This allows the micelle size to be systematically varied. Results from this work are used to understand the formation mechanism of nanoporous structures in which the pore size and wall thickness are closely dependent on the size of hydrophobic cores and hydrophilic shells of the block copolymer templates. The core-shell mechanism for nanoporous structure evolution is based on the size and contrasting micellar packing arrangements that are controlled by the copolymer.

  13. High-density nanopore array for selective biomolecule transport.

    SciTech Connect

    Patel, Kamlesh D.

    2011-11-01

    Development of sophisticated tools capable of manipulating molecules at their own length scale enables new methods for chemical synthesis and detection. Although nanoscale devices have been developed to perform individual tasks, little work has been done on developing a truly scalable platform: a system that combines multiple components for sequential processing, as well as simultaneously processing and identifying the millions of potential species that may be present in a biological sample. The development of a scalable micro-nanofluidic device is limited in part by the ability to combine different materials (polymers, metals, semiconductors) onto a single chip, and the challenges with locally controlling the chemical, electrical, and mechanical properties within a micro or nanochannel. We have developed a unique construct known as a molecular gate: a multilayered polymer based device that combines microscale fluid channels with nanofluidic interconnects. Molecular gates have been demonstrated to selectively transport molecules between channels based on size or charge. In order to fully utilize these structures, we need to develop methods to actively control transport and identify species inside a nanopore. While previous work has been limited to creating electrical connections off-channel or metallizing the entire nanopore wall, we now have the ability to create multiple, separate conductive connections at the interior surface of a nanopore. These interior electrodes will be used for direct sensing of biological molecules, probing the electrical potential and charge distribution at the surface, and to actively turn on and off electrically driven transport of molecules through nanopores.

  14. Fabrication and ultraviolet photoresponse characteristics of ordered SnOx (x ≈ 0.87, 1.45, 2) nanopore films

    PubMed Central

    2011-01-01

    Based on the porous anodic aluminum oxide templates, ordered SnOx nanopore films (approximately 150 nm thickness) with different x (x ≈ 0.87, 1.45, 2) have been successfully fabricated by direct current magnetron sputtering and oxidizing annealing. Due to the high specific surface area, this ordered nanopore films exhibit a great improvement in recovery time compared to thin films for ultraviolet (UV) detection. Especially, the ordered SnOx nanopore films with lower x reveal higher UV light sensitivity and shorter current recovery time, which was explained by the higher concentration of the oxygen vacancies in this SnOx films. This work presents a potential candidate material for UV light detector. PACS: 81.15.Cd, 81.40.Ef, 81.70.Jb, 85.60.Gz. PMID:22142559

  15. The use of PEEK nanorod arrays for the fabrication of nanoporous surfaces under high temperature: SiNx example.

    PubMed

    Martín, Jaime; Martín-González, Marisol

    2012-09-21

    Large area silicon nitride (SiN(x)) nanoporous surfaces are fabricated using poly(ether-ether-ketone) (PEEK) nanorod arrays as a template. The procedure involves manipulation of nanoporous anodic aluminum oxide (AAO) templates in order to form an ordered array of PEEK nanopillars with high temperature resistant characteristics. In this context, self-ordered AAO templates are infiltrated with PEEK melts via the "precursor film" method. Once the melts have been crystallized in the porous structure of AAO, the basis alumina layer is removed, yielding an ordered array of PEEK nanopillars. The resulting structure is a high temperature and chemical resistant polymeric nanomold, which can be utilized in the synthesis of nanoporous materials under aggressive conditions. Such conditions are high temperatures (up to 320 °C), vacuum, or extreme pH. For example, SiN(x) nanopore arrays have been grown by plasma enhanced chemical vapor deposition at 300 °C, which can be of interest as mold for nanoimprint lithography, due to its hardness and low surface energy. The SiN(x) nanopore array portrays the same characteristics as the original AAO template: 120 nm diameter pores and an interpore distance of 430 nm. Furthermore, the aspect ratio of the SiN(x) nanopores can be tuned by selecting an AAO template with appropriate conditions. The use of PEEK as a nanotemplate extends the applicability of polymeric nanopatterns into a temperature regime up to now not accessible and opens up the simple fabrication of novel nanoporous inorganic surfaces. PMID:22854871

  16. Nanoporous ultra-high specific surface inorganic fibres

    NASA Astrophysics Data System (ADS)

    Kanehata, Masaki; Ding, Bin; Shiratori, Seimei

    2007-08-01

    Nanoporous inorganic (silica) nanofibres with ultra-high specific surface have been fabricated by electrospinning the blend solutions of poly(vinyl alcohol) (PVA) and colloidal silica nanoparticles, followed by selective removal of the PVA component. The configurations of the composite and inorganic nanofibres were investigated by changing the average silica particle diameters and the concentrations of colloidal silica particles in polymer solutions. After the removal of PVA by calcination, the fibre shape of pure silica particle assembly was maintained. The nanoporous silica fibres were assembled as a porous membrane with a high surface roughness. From the results of Brunauer-Emmett-Teller (BET) measurements, the BET surface area of inorganic silica nanofibrous membranes was increased with the decrease of the particle diameters. The membrane composed of silica particles with diameters of 15 nm showed the largest BET surface area of 270.3 m2 g-1 and total pore volume of 0.66 cm3 g-1. The physical absorption of methylene blue dye molecules by nanoporous silica membranes was examined using UV-vis spectrometry. Additionally, the porous silica membranes modified with fluoroalkylsilane showed super-hydrophobicity due to their porous structures.

  17. Nanoporous Cathodes for High-Energy Li-S Batteries from Gyroid Block Copolymer Templates.

    PubMed

    Choudhury, Soumyadip; Agrawal, Mukesh; Formanek, Petr; Jehnichen, Dieter; Fischer, Dieter; Krause, Beate; Albrecht, Victoria; Stamm, Manfred; Ionov, Leonid

    2015-06-23

    This study reports on a facile approach to the fabrication of nanoporous carbon cathodes for lithium sulfur batteries using gyroid carbon replicas based on use of polystyrene-poly-4-vinylpyridine (PS-P4VP) block copolymers as sacrificial templates. The free-standing gyroid carbon network with a highly ordered and interconnected porous structure has been fabricated by impregnating the carbon precursor solution into the gyroid block copolymer nanotemplates and subsequently carbonizing them. A wide range of analytical tools have been employed to characterize fabricated porous carbon material. Prepared nanostructures are envisioned to have a great potential in myriad areas such as energy storage/conversion devices owing to their fascinating morphology exhibiting high surface area and uniform porosity with interconnected three-dimensional networks. The resulting carbon nanoporous structures infused with elemental sulfur have been found to work as a promising electrode for lithium sulfur batteries demonstrating a high cycling stability over more than 200 cycles. PMID:26014100

  18. Three-dimensional bicontinuous nanoporous Au/polyaniline hybrid films for high-performance electrochemical supercapacitors

    NASA Astrophysics Data System (ADS)

    Lang, Xingyou; Zhang, Ling; Fujita, Takeshi; Ding, Yi; Chen, Mingwei

    2012-01-01

    We report three-dimensional bicontinuous nanoporous Au/polyaniline (PANI) composite films made by one-step electrochemical polymerization of PANI shell onto dealloyed nanoporous gold (NPG) skeletons for the applications in electrochemical supercapacitors. The NPG/PANI based supercapacitors exhibit ultrahigh volumetric capacitance (∼1500 F cm-3) and energy density (∼0.078 Wh cm-3), which are seven and four orders of magnitude higher than these of electrolytic capacitors, with the same power density up to ∼190 W cm-3. The outstanding capacitive performances result from a novel nanoarchitecture in which pseudocapacitive PANI shells are incorporated into pore channels of highly conductive NPG, making them promising candidates as electrode materials in supercapacitor devices combing high-energy storage densities with high-power delivery.

  19. 3D Nanoporous Metal Phosphides toward High-Efficiency Electrochemical Hydrogen Production.

    PubMed

    Tan, Yongwen; Wang, Hao; Liu, Pan; Cheng, Chun; Zhu, Fan; Hirata, Akihiko; Chen, Mingwei

    2016-04-01

    Free-standing nanoporous metal phosphides are fabricated by a novel top-down method, by selectively leaching less-stable metal phases from rapidly solidified two-phase metal-phosphorus alloys. The phosphide phases with relatively high electrochemical stability are left as the skeletons of nanoporous structures. The resultant nanoporous phosphides with tunable pore size and porosity show superior catalytic activities toward electrochemical hydrogen production. PMID:26889914

  20. Investigation of microcantilever array with ordered nanoporous coatings for selective chemical detection

    NASA Astrophysics Data System (ADS)

    Lee, J.-H.; Houk, R. T. J.; Robinson, A.; Greathouse, J. A.; Thornberg, S. M.; Allendorf, M. D.; Hesketh, P. J.

    2010-04-01

    In this paper we demonstrate the potential for novel nanoporous framework materials (NFM) such as metal-organic frameworks (MOFs) to provide selectivity and sensitivity to a broad range of analytes including explosives, nerve agents, and volatile organic compounds (VOCs). NFM are highly ordered, crystalline materials with considerable synthetic flexibility resulting from the presence of both organic and inorganic components within their structure. Detection of chemical weapons of mass destruction (CWMD), explosives, toxic industrial chemicals (TICs), and volatile organic compounds (VOCs) using micro-electro-mechanical-systems (MEMS) devices, such as microcantilevers and surface acoustic wave sensors, requires the use of recognition layers to impart selectivity. Traditional organic polymers are dense, impeding analyte uptake and slowing sensor response. The nanoporosity and ultrahigh surface areas of NFM enhance transport into and out of the NFM layer, improving response times, and their ordered structure enables structural tuning to impart selectivity. Here we describe experiments and modeling aimed at creating NFM layers tailored to the detection of water vapor, explosives, CWMD, and VOCs, and their integration with the surfaces of MEMS devices. Force field models show that a high degree of chemical selectivity is feasible. For example, using a suite of MOFs it should be possible to select for explosives vs. CWMD, VM vs. GA (nerve agents), and anthracene vs. naphthalene (VOCs). We will also demonstrate the integration of various NFM with the surfaces of MEMS devices and describe new synthetic methods developed to improve the quality of VFM coatings. Finally, MOF-coated MEMS devices show how temperature changes can be tuned to improve response times, selectivity, and sensitivity.

  1. Investigation of microcantilever array with ordered nanoporous coatings for selective chemical detection.

    SciTech Connect

    Allendorf, Mark D.; Thornberg, Steven Michael; Lee, J. -H.; Robinson, Alex Lockwood; Hesketh, Peter J.; Greathouse, Jeffery A.; Houk, Ronald J. T.

    2010-03-01

    In this paper we demonstrate the potential for novel nanoporous framework materials (NFM) such as metal-organic frameworks (MOFs) to provide selectivity and sensitivity to a broad range of analytes including explosives, nerve agents, and volatile organic compounds (VOCs). NFM are highly ordered, crystalline materials with considerable synthetic flexibility resulting from the presence of both organic and inorganic components within their structure. Detection of chemical weapons of mass destruction (CWMD), explosives, toxic industrial chemicals (TICs), and volatile organic compounds (VOCs) using micro-electro-mechanical-systems (MEMS) devices, such as microcantilevers and surface acoustic wave sensors, requires the use of recognition layers to impart selectivity. Traditional organic polymers are dense, impeding analyte uptake and slowing sensor response. The nanoporosity and ultrahigh surface areas of NFM enhance transport into and out of the NFM layer, improving response times, and their ordered structure enables structural tuning to impart selectivity. Here we describe experiments and modeling aimed at creating NFM layers tailored to the detection of water vapor, explosives, CWMD, and VOCs, and their integration with the surfaces of MEMS devices. Force field models show that a high degree of chemical selectivity is feasible. For example, using a suite of MOFs it should be possible to select for explosives vs. CWMD, VM vs. GA (nerve agents), and anthracene vs. naphthalene (VOCs). We will also demonstrate the integration of various NFM with the surfaces of MEMS devices and describe new synthetic methods developed to improve the quality of VFM coatings. Finally, MOF-coated MEMS devices show how temperature changes can be tuned to improve response times, selectivity, and sensitivity.

  2. Fabrication of high reflectivity nanoporous distributed Bragg reflectors by controlled electrochemical etching of GaN

    NASA Astrophysics Data System (ADS)

    Lee, Seung-Min; Kang, Jin-Ho; Lee, June Key; Ryu, Sang-Wan

    2016-07-01

    The nanoporous medium is a valuable feature of optical devices because of its variable optical refractive index with porosity. One important application is in a GaN-based vertical cavity surface emitting laser having a distributed Bragg reflector (DBR) composed of alternating nanoporous and bulk GaNs. However, optimization of the fabrication process for high reflectivity DBRs having wellcontrolled high reflection bands has not been studied yet. We used electrochemical etching to study the fabrication process of a nanoporous GaN DBR and analyzed the relationship between the morphology and optical reflectivity. Several electrolytes were examined for the formation of the optimized nanoporous structure. A highly reflective DBRs having reflectivity of ~100% were obtained over a wide wavelength range of 450-750 nm. Porosification of semiconductors into nanoporous layers could provide a high reflectivity DBR due to controlled index-contrast, which would be advantages for the construction of a high-Q optical cavity.

  3. Nondestructive Creation of Ordered Nanopores by Selective Swelling of Block Copolymers: Toward Homoporous Membranes.

    PubMed

    Wang, Yong

    2016-07-19

    Pores regulate the entry and exit of substances based on the differences in physical sizes or chemical affinities. Pore uniformity, ordering, and the homogeneity of the surface chemistry of the pore walls are vital for maximizing the performance of a porous material because any scattering in these parameters weakens the capability of pores to discriminate foreign substances. Most strategies for the creation of homogeneous pores are destructive, and sacrificial components in the precursor materials must be selectively removed to generate porosities. The incorporation and subsequent removal of the sacrificial components frequently make the pore-making process complicated and inefficient and impose greater uncertainty in the control of the pore homogeneity. Block copolymers (BCPs) have been demonstrated to be promising precursors in the fabrication of highly ordered nanoporous structures. Unfortunately, BCP-derived porosities are also predominantly dependent on destructive pore-making processes (e.g., etching or extraction). To address this problem, we have developed a swelling-based nondestructive strategy. In this swelling process, one simply needs to immerse BCP materials in a solvent selective for the minority blocks for hours. After removing the BCPs from the solvent followed by air drying, pores are generated throughout the BCP materials in the positions where the minority blocks initially dwell. This Account discusses our recent discoveries, new insights, and emerging applications of this burgeoning pore-making method with a focus on the development of ordered porosities in bulk BCP materials. The initial morphology and orientation of the minority phases in BCPs determine the pore orientation and geometry in the produced porous materials. For nonaligned BCPs, three-dimensionally interconnected pores with sizes scattering in the 10-50 nm range are produced after swelling. There is a morphology evolution of BCP materials from the initial nonporous structure to

  4. Large enhancement of quantum dot fluorescence by highly scalable nanoporous gold.

    PubMed

    Zhang, Ling; Song, Yunke; Fujita, Takeshi; Zhang, Ye; Chen, Mingwei; Wang, Tza-Huei

    2014-02-26

    Dealloyed nanoporous gold (NPG) dramatically enhances quantum dot (QD) fluorescence by amplifying near-field excitation and increasing the radiative decay rate. Originating from plasmonic coupling, the fluorescence enhancement is highly dependent upon the nanopore size of the NPG. In contrast to other nanoengineered metallic structures, NPG exhibits fluorescence enhancement of QDs over a large substrate surface. PMID:24339211

  5. Molecular Order and Dynamics of Tris(2-ethylhexyl)phosphate Confined in Uni-Directional Nanopores

    SciTech Connect

    Kipnusu, Wycliffe Kiprop; Kossack, Wilhelm; Iacob, Ciprian; Jasiurkowska, Malgorzata; Sangoro, Joshua R; Kremer, Friedrich

    2012-01-01

    Infrared Transition Moment Orientational Analysis (IR-TMOA) and Broadband Dielectric Spectroscopy (BDS) are combined to study molecular order and dynamics of the glass-forming liquid Tris(2-ethylhexy)phosphate (TEHP) confined in uni-directional nanopores with diameters of 4, 8, and 10.4 nm. The former method enables one to determine the molecular order parameter of specific IR transition moments. It is observed that the central P=O moiety of TEHP has a weak orientational effect (molecular order parameter Sz = 0.1 0.04) due the nanoporous confinement, in contrast to the terminal C H groups. BDS traces the dynamic glass transition of the guest molecules in a broad spectral range and at widely varying temperature. An enhancement of the mobility takes place when approaching the glass transition temperature and becomes more pronounced with decreasing pore diameter. This is attributed to a slight reduction of the density of the confined liquid caused by the 2-dimensional geometrical constraint.

  6. Nanoporous Gyroid-Structured Epoxy from Block Copolymer Templates for High Protein Adsorbability.

    PubMed

    Wang, Xin-Bo; Lin, Tze-Chung; Hsueh, Han-Yu; Lin, Shih-Chieh; He, Xiao-Dong; Ho, Rong-Ming

    2016-06-28

    Nanoporous epoxy with gyroid texture is fabricated by using a nanoporous polymer with gyroid-forming nanochannels as a template for polymerization of epoxy. The nanoporous polymer template is obtained from the self-assembly of degradable block copolymer, polystyrene-b-poly(l-lactide) (PS-PLLA), followed by hydrolysis of PLLA blocks. Templated polymerization can be conducted under ambient conditions to create well-defined, bicontinuous epoxy networks in a PS matrix. By taking advantage of multistep curing of epoxy, well-ordered robust nanoporous epoxy can be obtained after removal of PS template, giving robust porous materials. The through-hole nanoporous epoxy in the film state can be used as a coated layer to enhance the adsorbability for both lysozyme and bovine serum albumin. PMID:27245380

  7. High-Bandwidth Protein Analysis Using Solid-State Nanopores

    PubMed Central

    Larkin, Joseph; Henley, Robert Y.; Muthukumar, Murugappan; Rosenstein, Jacob K.; Wanunu, Meni

    2014-01-01

    High-bandwidth measurements of the ion current through hafnium oxide and silicon nitride nanopores allow the analysis of sub-30 kD protein molecules with unprecedented time resolution and detection efficiency. Measured capture rates suggest that at moderate transmembrane bias values, a substantial fraction of protein translocation events are detected. Our dwell-time resolution of 2.5 μs enables translocation time distributions to be fit to a first-passage time distribution derived from a 1D diffusion-drift model. The fits yield drift velocities that scale linearly with voltage, consistent with an electrophoretic process. Further, protein diffusion constants (D) are lower than the bulk diffusion constants (D0) by a factor of ∼50, and are voltage-independent in the regime tested. We reason that deviations of D from D0 are a result of confinement-driven pore/protein interactions, previously observed in porous systems. A straightforward Kramers model for this inhibited diffusion points to 9- to 12-kJ/mol interactions of the proteins with the nanopore. Reduction of μ and D are found to be material-dependent. Comparison of current-blockage levels of each protein yields volumetric information for the two proteins that is in good agreement with dynamic light scattering measurements. Finally, detection of a protein-protein complex is achieved. PMID:24507610

  8. Atomic layer deposition of nanoporous biomaterials.

    SciTech Connect

    Narayan, R. J.; Adiga, S. P.; Pellin, M. J.; Curtiss, L. A.; Stafslien, S.; Chisholm, B.; Monteiro-Riviere, N. A.; Brigmon, R. L.; Elam, J. W.; Univ. of North Carolina; North Carolina State Univ.; Eastman Kodak Co.; North Dakota State Univ.; SRL

    2010-03-01

    Due to its chemical stability, uniform pore size, and high pore density, nanoporous alumina is being investigated for use in biosensing, drug delivery, hemodialysis, and other medical applications. In recent work, we have examined the use of atomic layer deposition for coating the surfaces of nanoporous alumina membranes. Zinc oxide coatings were deposited on nanoporous alumina membranes using atomic layer deposition. The zinc oxide-coated nanoporous alumina membranes demonstrated antimicrobial activity against Escherichia coli and Staphylococcus aureus bacteria. These results suggest that atomic layer deposition is an attractive technique for modifying the surfaces of nanoporous alumina membranes and other nanostructured biomaterials. Nanoporous alumina, also known as anodic aluminum oxide (AAO), is a nanomaterial that exhibits several unusual properties, including high pore densities, straight pores, small pore sizes, and uniform pore sizes. In 1953, Keller et al. showed that anodizing aluminum in acid electrolytes results in a thick layer of nearly cylindrical pores, which are arranged in a close-packed hexagonal cell structure. More recently, Matsuda & Fukuda demonstrated preparation of highly ordered platinum and gold nanohole arrays using a replication process. In this study, a negative structure of nanoporous alumina was initially fabricated and a positive structure of a nanoporous metal was subsequently fabricated. Over the past fifteen years, nanoporous alumina membranes have been used as templates for growth of a variety of nanostructured materials, including nanotubes, nanowires, nanorods, and nanoporous membranes.

  9. Large scale synthesis of nanoporous BN flake with high surface areas

    NASA Astrophysics Data System (ADS)

    Zhu, Hui-Ling; Han, Qiu-Xia; Wu, Jie; Meng, Xiang-Lin; Cui, Hong-Zhi

    2016-01-01

    Nanoporous boron nitride (BN) flake was synthesized in large scale at temperatures between 550 and 600 °C for 10 h via the simple reaction between NaBH4 and CH5N3S. X-ray diffraction and Fourier transform infrared spectra confirm the formation of hexagonal BN. Examination by high-resolution transmission electron microscope reveals that the product is comprised of nanoporous flake, which exhibits a high surface area of 214 m2 g-1 characterized by nitrogen adsorption-desorption isotherms. The nanoporous BN flake has good thermal stability and oxidation resistance up to 800 °C measured by thermogravimetric analysis.

  10. Preparation of nanoporous metal foam from high nitrogen transition metal complexes

    DOEpatents

    Tappan, Bryce C.; Huynh, My Hang V.; Hiskey, Michael A.; Son, Steven F.; Oschwald, David M.; Chavez, David E.; Naud, Darren L.

    2006-11-28

    Nanoporous metal foams are prepared by ignition of high nitrogen transition metal complexes. The ammonium salts of iron(III) tris[bi(tetrazolato)-amine], cobalt(III) tris(bi(tetrazolato)amine), and high nitrogen compounds of copper and silver were prepared as loose powders, pressed into pellets and wafers, and ignited under an inert atmosphere to form nanoporous metal foam monoliths having very high surface area and very low density.

  11. High-throughput optical sensing of nucleic acids in a nanopore array

    NASA Astrophysics Data System (ADS)

    Huang, Shuo; Romero-Ruiz, Mercedes; Castell, Oliver K.; Bayley, Hagan; Wallace, Mark I.

    2015-11-01

    Protein nanopores such as α-haemolysin and Mycobacterium smegmatis porin A (MspA) can be used to sequence long strands of DNA at low cost. To provide high-speed sequencing, large arrays of nanopores are required, but current nanopore sequencing methods rely on ionic current measurements from individually addressed pores and such methods are likely to prove difficult to scale up. Here we show that, by optically encoding the ionic flux through protein nanopores, the discrimination of nucleic acid sequences and the detection of sequence-specific nucleic acid hybridization events can be parallelized. We make optical recordings at a density of ∼104 nanopores per mm2 in a single droplet interface bilayer. Nanopore blockades can discriminate between DNAs with sub-picoampere equivalent resolution, and specific miRNA sequences can be identified by differences in unzipping kinetics. By creating an array of 2,500 bilayers with a micropatterned hydrogel chip, we are also able to load different samples into specific bilayers suitable for high-throughput nanopore recording.

  12. High-throughput optical sensing of nucleic acids in a nanopore array.

    PubMed

    Huang, Shuo; Romero-Ruiz, Mercedes; Castell, Oliver K; Bayley, Hagan; Wallace, Mark I

    2015-11-01

    Protein nanopores such as α-haemolysin and Mycobacterium smegmatis porin A (MspA) can be used to sequence long strands of DNA at low cost. To provide high-speed sequencing, large arrays of nanopores are required, but current nanopore sequencing methods rely on ionic current measurements from individually addressed pores and such methods are likely to prove difficult to scale up. Here we show that, by optically encoding the ionic flux through protein nanopores, the discrimination of nucleic acid sequences and the detection of sequence-specific nucleic acid hybridization events can be parallelized. We make optical recordings at a density of ∼10(4) nanopores per mm(2) in a single droplet interface bilayer. Nanopore blockades can discriminate between DNAs with sub-picoampere equivalent resolution, and specific miRNA sequences can be identified by differences in unzipping kinetics. By creating an array of 2,500 bilayers with a micropatterned hydrogel chip, we are also able to load different samples into specific bilayers suitable for high-throughput nanopore recording. PMID:26322943

  13. Ordered La0.7Sr0.3MnO3 nanohole arrays fabricated on a nanoporous alumina template by pulsed laser ablation

    NASA Astrophysics Data System (ADS)

    Kumaresavanji, M.; Gomes, I. T.; Apolinario, A.; Rolo, A. G.; Almeida, B. G.; Lopes, A. M. L.; Araujo, J. P.

    2016-03-01

    Highly ordered nanohole arrays of {{La}}0.7{{Sr}}0.3{{MnO}}3 manganite have been synthesized using pulsed laser deposition on nanoporous alumina template. Their structure and phase formation were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive x-ray spectroscopy (EDX) and x-ray diffraction (XRD). The magnetic measurements were performed with respect to temperature and field and exhibit a ferromagnetic to paramagnetic transition at 284 K. In addition, the temperature dependence of electrical resistance was measured at different magnetic fields and an insulating phase throughout all the temperatures was observed. The low temperature ferromagnetic insulating state is discussed by the presence of a canted ferromagnetic state induced by the nanoholes. The present work shows the feasibility of combining both the nanoporous alumina template and pulsed laser ablation for the fabrication of perovskite manganite nanohole arrays which can also be extended to fabricate other multicomponent oxide nanohole materials.

  14. Ordered nanoporous silica as carriers for improved delivery of water insoluble drugs: a comparative study between three dimensional and two dimensional macroporous silica

    PubMed Central

    Wang, Ying; Zhao, Qinfu; Hu, Yanchen; Sun, Lizhang; Bai, Ling; Jiang, Tongying; Wang, Siling

    2013-01-01

    The goal of the present study was to compare the drug release properties and stability of the nanoporous silica with different pore architectures as a matrix for improved delivery of poorly soluble drugs. For this purpose, three dimensional ordered macroporous (3DOM) silica with 3D continuous and interconnected macropores of different sizes (200 nm and 500 nm) and classic mesoporous silica (ie, Mobil Composition of Matter [MCM]-41 and Santa Barbara Amorphous [SBA]-15) with well-ordered two dimensional (2D) cylindrical mesopores were successfully fabricated and then loaded with the model drug indomethacin (IMC) via the solvent deposition method. Scanning electron microscopy (SEM), N2 adsorption, differential scanning calorimetry (DSC), and X-ray diffraction (XRD) were applied to systematically characterize all IMC-loaded nanoporous silica formulations, evidencing the successful inclusion of IMC into nanopores, the reduced crystallinity, and finally accelerated dissolution of IMC. It was worth mentioning that, in comparison to 2D mesoporous silica, 3DOM silica displayed a more rapid release profile, which may be ascribed to the 3D interconnected pore networks and the highly accessible surface areas. The results obtained from the stability test indicated that the amorphous state of IMC entrapped in the 2D mesoporous silica (SBA-15 and MCM-41) has a better physical stability than in that of 3DOM silica. Moreover, the dissolution rate and stability of IMC loaded in 3DOM silica was closely related to the pore size of macroporous silica. The colorimetric 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Cell Counting Kit (CCK)-8 assays in combination with direct morphology observations demonstrated the good biocompatibility of nanoporous silica, especially for 3DOM silica and SBA-15. The present work encourages further study of the drug release properties and stability of drug entrapped in different pore architecture of silica in order to realize

  15. 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.

  16. Obtaining structural information of small proteins using solid-state nanopores and high-bandwidth measurements

    NASA Astrophysics Data System (ADS)

    Niedzwiecki, David; Lanci, Christopher; Saven, Jeffery; Drndic, Marija

    2015-03-01

    The use of biological nanopores sensors to characterize proteins has proved a fruitful field of study. Solid-state nanopores hold several advantages over their biological counterparts, including the ability to tune pore diameter and their robustness to external conditions. Despite these advantages, the use of solid-state nanopores for protein analysis has proved difficult due to rapid translocation times of proteins and poor signal-to-noise of small peptides. Recently, improvements in high-bandwidth acquisition and in signal-to-noise have made the study of small peptides using solid-state nanopores feasible. Here we report on the detection and characterization of peptides as small as 33 amino-acids in length using sub-10 nm thin silicon nitride nanopores, giving high signal levels, combined with high-bandwidth electronics. In addition we show differentiation between monomers and dimer forms of the GCN-4 p1 leucine zipper, a coil-coil structure, and compare this with the unstructured 33-mer. The differentiation between these two forms demonstrates the possibility of extracting useful structural information from short peptide structures using modern solid-state nanopore systems.

  17. Optically pumped GaN vertical cavity surface emitting laser with high index-contrast nanoporous distributed Bragg reflector.

    PubMed

    Lee, Seung-Min; Gong, Su-Hyun; Kang, Jin-Ho; Ebaid, Mohamed; Ryu, Sang-Wan; Cho, Yong-Hoon

    2015-05-01

    Laser operation of a GaN vertical cavity surface emitting laser (VCSEL) is demonstrated under optical pumping with a nanoporous distributed Bragg reflector (DBR). High reflectivity, approaching 100%, is obtained due to the high index-contrast of the nanoporous DBR. The VCSEL system exhibits low threshold power density due to the formation of high Q-factor cavity, which shows the potential of nanoporous medium for optical devices. PMID:25969197

  18. Fabrication and Characterization of Solid-state Nanopore Arrays for High Throughput DNA Sequencing

    PubMed Central

    Torre, Ruby dela; Larkin, Joseph; Singer, Alon; Meller, Amit

    2012-01-01

    We report the fabrication and characterization of uniformly-sized nanopore arrays, integrated into an optical detection system for high-throughput DNA sequencing applications. Nanopore arrays were fabricated using Focused Ion Beam milling followed by TiO2 coating using Atomic Layer Deposition (ALD). The TiO2 layer decreases the initial pore diameter down to sub-10nm range, compatible with the requirements for nanopore-based sequencing using optical readout. We find that the TiO2 layers produce a lower photoluminescence background as compared with the more broadly used Al2O3 coatings. The functionality of the nanopore array was demonstrated by the simultaneous optical detection of DNA-quantum dot-conjugates, which were electro-kinetically driven through the nanopores. Our optical scheme employs Total Internal Reflection Fluorescence (TIRF) microscopy to illuminate a wide area of the TiO2-coated membrane. A highly parallel system for observing DNA capture events in a uniformly-sized 6×6 nanopore array was experimentally realized. PMID:22948520

  19. Optimizing Nanopore Surface Properties for High-Efficiency Water Desalination

    NASA Astrophysics Data System (ADS)

    Cohen-Tanugi, David; Grossman, Jeffrey

    2011-03-01

    As water resources worldwide become rapidly scarcer, it is becoming increasingly important to devise new techniques to obtain clean water from seawater. At present, water purification technologies are limited by costly energy requirements relative to the theoretical thermodynamic limit and by insufficient understanding of the physical processes underlying ion filtration and fluid transport at the molecular scale. New advances in computational materials science offer a promising way to deepen our understanding of these physical phenomena. In this presentation, we describe a new approach for high-efficiency water desalination based on surface-engineered porous materials. This approach is especially relevant for promising technologies such as nanofiltration and membrane distillation, which offers promising advantages over traditional desalination technologies using mesoporous membranes that are only permeable to pure water vapor. More accurate molecular modeling of mesoporous and nanoporous materials represents a key step towards efficient large-scale treatment of seawater. Results regarding the effect of pore properties (surface texture, morphology, density, tortuosity) on desired performance characteristics such as ion selectivity, maximal water flux and energy requirements will be presented.

  20. Crosstalk between adjacent nanopores in a solid-state membrane array for multi-analyte high-throughput biomolecule detection

    NASA Astrophysics Data System (ADS)

    Raza, Muhammad Usman; Saleem, Sajid; Ali, Waqas; Iqbal, Samir M.

    2016-08-01

    Single nanopores are used to detect a variety of biological molecules. The modulations in ionic current under applied bias across the nanopore contain important information about translocating species, thus providing single analyte detection. These systems are, however, challenged in practical situations where multiple analytes have to be detected at high throughput. This paper presents the analysis of a multi-nanopore system that can be used for the detection of analytes with high throughput. As a scalable model, two nanopores were simulated in a single solid-state membrane. The interactions of the electric fields at the mouths of the individual nanopores were analyzed. The data elucidated the electrostatic properties of the nanopores from a single membrane and provided a framework to calculate the -3 dB distance, akin to the Debye length, from one nanopore to the other. This distance was the minimum distance between the adjacent nanopores such that their individual electric fields did not significantly interact with one another. The results can help in the optimal experimental design to construct solid-state nanopore arrays for any given nanopore size and applied bias.

  1. Toward high permeability, selectivity and controllability of water desalination with FePc nanopores.

    PubMed

    Deng, Qingming; Pan, Jun; Yin, Xiaohui; Wang, Xiaofeng; Zhao, Lina; Kang, Seung-gu; Jimenez-Cruz, Camilo A; Zhou, Ruhong; Li, Jingyuan

    2016-03-21

    Nanoporous materials exhibit promising potential in water transportation applications, especially in ocean water desalination. It is highly desired to have great permeability, selectivity and controllability in the desalination performance of these nanopores. However, it is still a challenge to achieve all three features in one material or device. Here, we demonstrate efficient and controllable water desalination with a nanoporous 2D Fe phthalocyanine (FePc) membrane using molecular dynamics simulations. We find the FePc membrane not only conducts fast water flow, but it also suppresses ion permeation. The selectivity is attributed to a mechanism distinct from the traditional steric exclusion: cations are excluded due to electrostatic repulsion, whereas anions can be trapped in the nanopore and induce the reorganization of ions in the vicinity of the nanopore, which in turn creates a tendency for the trapped anions to move back into the saline reservoir. More interestingly, we find such mechanism is largely due to the sufficiently strong electrostatic interaction of the charged nanopore region with ions and is not restricted to the FePc nanopore. In addition, the number of protonated nitrogen atoms in FePc pores can be modulated by adjusting the pH value of the solution. The extent of the anion occupancy can thus be regulated, giving rise to control of the water flow. Taken together, great permeability, selectivity and controllability can be achieved with this nanosheet system. Moreover, our study suggests there is an alternative mechanism of water desalination which may be realized by intrinsically nanoporous materials such as FePc membranes. PMID:26923172

  2. Threading DNA through nanopores for biosensing applications

    NASA Astrophysics Data System (ADS)

    Fyta, Maria

    2015-07-01

    This review outlines the recent achievements in the field of nanopore research. Nanopores are typically used in single-molecule experiments and are believed to have a high potential to realize an ultra-fast and very cheap genome sequencer. Here, the various types of nanopore materials, ranging from biological to 2D nanopores are discussed together with their advantages and disadvantages. These nanopores can utilize different protocols to read out the DNA nucleobases. Although, the first nanopore devices have reached the market, many still have issues which do not allow a full realization of a nanopore sequencer able to sequence the human genome in about a day. Ways to control the DNA, its dynamics and speed as the biomolecule translocates the nanopore in order to increase the signal-to-noise ratio in the reading-out process are examined in this review. Finally, the advantages, as well as the drawbacks in distinguishing the DNA nucleotides, i.e., the genetic information, are presented in view of their importance in the field of nanopore sequencing.

  3. Threading DNA through nanopores for biosensing applications.

    PubMed

    Fyta, Maria

    2015-07-15

    This review outlines the recent achievements in the field of nanopore research. Nanopores are typically used in single-molecule experiments and are believed to have a high potential to realize an ultra-fast and very cheap genome sequencer. Here, the various types of nanopore materials, ranging from biological to 2D nanopores are discussed together with their advantages and disadvantages. These nanopores can utilize different protocols to read out the DNA nucleobases. Although, the first nanopore devices have reached the market, many still have issues which do not allow a full realization of a nanopore sequencer able to sequence the human genome in about a day. Ways to control the DNA, its dynamics and speed as the biomolecule translocates the nanopore in order to increase the signal-to-noise ratio in the reading-out process are examined in this review. Finally, the advantages, as well as the drawbacks in distinguishing the DNA nucleotides, i.e., the genetic information, are presented in view of their importance in the field of nanopore sequencing. PMID:26061408

  4. Highly efficient shrinkage of inverted-pyramid silicon nanopores by plasma-enhanced chemical vapor deposition technology.

    PubMed

    Wang, Yifan; Deng, Tao; Chen, Qi; Liang, Feng; Liu, Zewen

    2016-06-24

    Solid-state nanopore-based analysis systems are currently one of the most attractive and promising platforms in sensing fields. This work presents a highly efficient method to shrink inverted-pyramid silicon nanopores using plasma-enhanced chemical vapor deposition (PECVD) technology by the deposition of SiN x onto the surface of the nanopore. The contraction of the inverted-pyramid silicon nanopores when subjected to the PECVD process has been modeled and carefully analyzed, and the modeling data are in good agreement with the experimental results within a specific PECVD shrinkage period (∼0-600 s). Silicon nanopores within a 50-400 nm size range contract to sub-10 nm dimensions. Additionally, the inner structure of the nanopores after the PECVD process has been analyzed by focused ion beam cutting process. The results show an inner structure morphology change from inverted-pyramid to hourglass, which may enhance the spatial resolution of sensing devices. PMID:27181294

  5. Highly efficient shrinkage of inverted-pyramid silicon nanopores by plasma-enhanced chemical vapor deposition technology

    NASA Astrophysics Data System (ADS)

    Wang, Yifan; Deng, Tao; Chen, Qi; Liang, Feng; Liu, Zewen

    2016-06-01

    Solid-state nanopore-based analysis systems are currently one of the most attractive and promising platforms in sensing fields. This work presents a highly efficient method to shrink inverted-pyramid silicon nanopores using plasma-enhanced chemical vapor deposition (PECVD) technology by the deposition of SiN x onto the surface of the nanopore. The contraction of the inverted-pyramid silicon nanopores when subjected to the PECVD process has been modeled and carefully analyzed, and the modeling data are in good agreement with the experimental results within a specific PECVD shrinkage period (∼0–600 s). Silicon nanopores within a 50–400 nm size range contract to sub-10 nm dimensions. Additionally, the inner structure of the nanopores after the PECVD process has been analyzed by focused ion beam cutting process. The results show an inner structure morphology change from inverted-pyramid to hourglass, which may enhance the spatial resolution of sensing devices.

  6. Photoresistance Switching of Plasmonic Nanopores

    PubMed Central

    2015-01-01

    Fast and reversible modulation of ion flow through nanosized apertures is important for many nanofluidic applications, including sensing and separation systems. Here, we present the first demonstration of a reversible plasmon-controlled nanofluidic valve. We show that plasmonic nanopores (solid-state nanopores integrated with metal nanocavities) can be used as a fluidic switch upon optical excitation. We systematically investigate the effects of laser illumination of single plasmonic nanopores and experimentally demonstrate photoresistance switching where fluidic transport and ion flow are switched on or off. This is manifested as a large (∼1–2 orders of magnitude) increase in the ionic nanopore resistance and an accompanying current rectification upon illumination at high laser powers (tens of milliwatts). At lower laser powers, the resistance decreases monotonically with increasing power, followed by an abrupt transition to high resistances at a certain threshold power. A similar rapid transition, although at a lower threshold power, is observed when the power is instead swept from high to low power. This hysteretic behavior is found to be dependent on the rate of the power sweep. The photoresistance switching effect is attributed to plasmon-induced formation and growth of nanobubbles that reversibly block the ionic current through the nanopore from one side of the membrane. This explanation is corroborated by finite-element simulations of a nanobubble in the nanopore that show the switching and the rectification. PMID:25514824

  7. Photoresistance switching of plasmonic nanopores.

    PubMed

    Li, Yi; Nicoli, Francesca; Chen, Chang; Lagae, Liesbet; Groeseneken, Guido; Stakenborg, Tim; Zandbergen, Henny W; Dekker, Cees; Van Dorpe, Pol; Jonsson, Magnus P

    2015-01-14

    Fast and reversible modulation of ion flow through nanosized apertures is important for many nanofluidic applications, including sensing and separation systems. Here, we present the first demonstration of a reversible plasmon-controlled nanofluidic valve. We show that plasmonic nanopores (solid-state nanopores integrated with metal nanocavities) can be used as a fluidic switch upon optical excitation. We systematically investigate the effects of laser illumination of single plasmonic nanopores and experimentally demonstrate photoresistance switching where fluidic transport and ion flow are switched on or off. This is manifested as a large (∼ 1-2 orders of magnitude) increase in the ionic nanopore resistance and an accompanying current rectification upon illumination at high laser powers (tens of milliwatts). At lower laser powers, the resistance decreases monotonically with increasing power, followed by an abrupt transition to high resistances at a certain threshold power. A similar rapid transition, although at a lower threshold power, is observed when the power is instead swept from high to low power. This hysteretic behavior is found to be dependent on the rate of the power sweep. The photoresistance switching effect is attributed to plasmon-induced formation and growth of nanobubbles that reversibly block the ionic current through the nanopore from one side of the membrane. This explanation is corroborated by finite-element simulations of a nanobubble in the nanopore that show the switching and the rectification. PMID:25514824

  8. Analysis of nanopore arrangement of porous alumina layers formed by anodizing in oxalic acid at relatively high temperatures

    NASA Astrophysics Data System (ADS)

    Zaraska, Leszek; Stępniowski, Wojciech J.; Jaskuła, Marian; Sulka, Grzegorz D.

    2014-06-01

    Anodic aluminum oxide (AAO) layers were formed by a simple two-step anodization in 0.3 M oxalic acid at relatively high temperatures (20-30 °C) and various anodizing potentials (30-65 V). The effect of anodizing conditions on structural features of as-obtained oxides was carefully investigated. A linear and exponential relationships between cell diameter, pore density and anodizing potential were confirmed, respectively. On the other hand, no effect of temperature and duration of anodization on pore spacing and pore density was found. Detailed quantitative and qualitative analyses of hexagonal arrangement of nanopore arrays were performed for all studied samples. The nanopore arrangement was evaluated using various methods based on the fast Fourier transform (FFT) images, Delaunay triangulations (defect maps), pair distribution functions (PDF), and angular distribution functions (ADF). It was found that for short anodizations performed at relatively high temperatures, the optimal anodizing potential that results in formation of nanostructures with the highest degree of pore order is 45 V. No direct effect of temperature and time of anodization on the nanopore arrangement was observed.

  9. Nanoporous gold as a highly active substrate for surface-enhanced Raman scattering spectroscopy

    SciTech Connect

    Kucheyev, S O; Hayes, J R; Biener, J; Hamza, A V

    2006-03-28

    Colloidal solutions of metal nanoparticles are currently among most studied substrates for sensors based on surface-enhanced Raman scattering (SERS). However, such substrates often suffer from not being cost-effective, reusable, or stable. Here, we develop nanoporous Au as a highly active, tunable, a.ordable, stable, bio-compatible, and reusable SERS substrate. Nanoporous Au is prepared by a facile process of free corrosion of AgAu alloys followed by annealing. Results show that nanofoams with average pore sizes of {approx} 250 nm exhibit the largest SERS signal for 632.8 nm excitation. This is attributed to the electromagnetic SERS enhancement mechanism with additional field localization within pores.

  10. 3D nanoporous optofluidic device for high sensitivity SERS detection

    NASA Astrophysics Data System (ADS)

    H. Yazdi, Soroush; White, Ian M.

    2012-03-01

    We report the demonstration of an optofluidic surface enhanced Raman spectroscopy (SERS) device that leverages nanoporous microfluidics to dramatically increase the SERS performance. A number of optofluidic approaches have been used to improve the detection limit of SERS in microfluidic channels, including active concentration of nanoparticles and/or analyte and passive concentration of nanoparticles. Previous reports have used a single nanofabricated fluidic channel to trap metal nanoparticles and adsorbed analytes. In this work, we utilize a significantly simpler fabrication approach by packing silica beads in a microfluidic channel to create a 3D nanofluidic concentration matrix. The device is fabricated using polydimethylsiloxane (PDMS) on glass using typical soft lithography methods. Due to the larger area of the nanoporous fluidic channel, this approach should be less prone to clogging than single nanofluidic inlets, and the loading time is decreased compared to previous reports. Using this microfluidic device, we achieved a detection limit of 4 femtomoles of Rhodamine 6G in 2 minutes. Compared to an open microfluidic channel, the 3D nanoporous concentration matrix increased the SERS signal by a factor of 250 due to the trapping of silver nanoclusters. Fiber optic cables are integrated into the PDMS to deliver excitation light directly to the detection volume and to collect Raman-scattered photons. As a result, the use of a laser diode and alignment-free integrated fiber optics implies the potential for the device to be used in portable and automated applications, such as the on-site detection of pesticides, water contaminants, and explosives.

  11. Ultrasonic deposition of high-selectivity nanoporous carbon membranes

    PubMed

    Shiflett; Foley

    1999-09-17

    Ultrasonic deposition creates a thin film of polymer on a tubular, macroporous, stainless steel support. Using polyfurfuryl alcohol as the nanoporous carbon precursor and a pyrolysis temperature of 723 kelvin, a membrane was prepared with the following permeances, measured in moles per square meter per Pascal per second: nitrogen, 1.8 x 10(-12); oxygen, 5.6 x 10(-11); helium, 3.3 x 10(-10); and hydrogen, 6.1 x 10(-10). The ideal separation factors as compared to that for nitrogen are 30:1, 178:1, and 331:1 for oxygen, helium, and hydrogen, respectively. PMID:10489366

  12. High Performance Graphene Nano-ribbon Thermoelectric Devices by Incorporation and Dimensional Tuning of Nanopores.

    PubMed

    Hossain, Md Sharafat; Al-Dirini, Feras; Hossain, Faruque M; Skafidas, Efstratios

    2015-01-01

    Thermoelectric properties of Graphene nano-ribbons (GNRs) with nanopores (NPs) are explored for a range of pore dimensions in order to achieve a high performance two-dimensional nano-scale thermoelectric device. We reduce thermal conductivity of GNRs by introducing pores in them in order to enhance their thermoelectric performance. The electrical properties (Seebeck coefficient and conductivity) of the device usually degrade with pore inclusion; however, we tune the pore to its optimal dimension in order to minimize this degradation, enhancing the overall thermoelectric performance (high ZT value) of our device. We observe that the side channel width plays an important role to achieve optimal performance while the effect of pore length is less pronounced. This result is consistent with the fact that electronic conduction in GNRs is dominated along its edges. Ballistic transport regime is assumed and a semi-empirical method using Huckel basis set is used to obtain the electrical properties, while the phononic system is characterized by Tersoff empirical potential model. The proposed device structure has potential applications as a nanoscale local cooler and as a thermoelectric power generator. PMID:26083450

  13. High Performance Graphene Nano-ribbon Thermoelectric Devices by Incorporation and Dimensional Tuning of Nanopores

    PubMed Central

    Sharafat Hossain, Md; Al-Dirini, Feras; Hossain, Faruque M.; Skafidas, Efstratios

    2015-01-01

    Thermoelectric properties of Graphene nano-ribbons (GNRs) with nanopores (NPs) are explored for a range of pore dimensions in order to achieve a high performance two-dimensional nano-scale thermoelectric device. We reduce thermal conductivity of GNRs by introducing pores in them in order to enhance their thermoelectric performance. The electrical properties (Seebeck coefficient and conductivity) of the device usually degrade with pore inclusion; however, we tune the pore to its optimal dimension in order to minimize this degradation, enhancing the overall thermoelectric performance (high ZT value) of our device. We observe that the side channel width plays an important role to achieve optimal performance while the effect of pore length is less pronounced. This result is consistent with the fact that electronic conduction in GNRs is dominated along its edges. Ballistic transport regime is assumed and a semi-empirical method using Huckel basis set is used to obtain the electrical properties, while the phononic system is characterized by Tersoff empirical potential model. The proposed device structure has potential applications as a nanoscale local cooler and as a thermoelectric power generator. PMID:26083450

  14. High Performance Graphene Nano-ribbon Thermoelectric Devices by Incorporation and Dimensional Tuning of Nanopores

    NASA Astrophysics Data System (ADS)

    Sharafat Hossain, Md; Al-Dirini, Feras; Hossain, Faruque M.; Skafidas, Efstratios

    2015-06-01

    Thermoelectric properties of Graphene nano-ribbons (GNRs) with nanopores (NPs) are explored for a range of pore dimensions in order to achieve a high performance two-dimensional nano-scale thermoelectric device. We reduce thermal conductivity of GNRs by introducing pores in them in order to enhance their thermoelectric performance. The electrical properties (Seebeck coefficient and conductivity) of the device usually degrade with pore inclusion; however, we tune the pore to its optimal dimension in order to minimize this degradation, enhancing the overall thermoelectric performance (high ZT value) of our device. We observe that the side channel width plays an important role to achieve optimal performance while the effect of pore length is less pronounced. This result is consistent with the fact that electronic conduction in GNRs is dominated along its edges. Ballistic transport regime is assumed and a semi-empirical method using Huckel basis set is used to obtain the electrical properties, while the phononic system is characterized by Tersoff empirical potential model. The proposed device structure has potential applications as a nanoscale local cooler and as a thermoelectric power generator.

  15. Optical reflectance studies of highly specular anisotropic nanoporous (111) InP membrane

    NASA Astrophysics Data System (ADS)

    Steele, J. A.; Lewis, R. A.; Sirbu, L.; Enachi, M.; Tiginyanu, I. M.; Skuratov, V. A.

    2015-04-01

    High-precision optical angular reflectance measurements are reported for a specular anisotropic nanoporous (111) InP membrane prepared by doping-assisted wet-electrochemical etching. The membrane surface morphology was investigated using scanning electron microscope imaging and revealed a quasi-uniform and self-organized nanoporous network consisting of semiconductor ‘islands’ in the sub-wavelength regime. The optical response of the nanoporous InP surface was studied at 405 nm (740 THz; UV), 633 nm (474 THz; VIS) and 1064 nm (282 THz; NIR), and exhibited a retention of basic macro-dielectric properties. Refractive index determinations demonstrate an optical anisotropy for the membrane which is strongly dependent on the wavelength of incident light, and exhibits an interesting inversion (positive anisotropy to negative) between 405 and 633 nm. The inversion of optical anisotropy is attributed to a strongly reduced ‘metallic’ behaviour in the membrane when subject to above-bandgap illumination. For the simplest case of sub-bandgap incident irradiation, the optical properties of the nanoporous InP sample are analysed in terms of an effective refractive index neff and compared to effective media approximations.

  16. Graphene Nanopore Support System for Simultaneous High-Resolution AFM Imaging and Conductance Measurements

    PubMed Central

    2015-01-01

    Accurately defining the nanoporous structure and sensing the ionic flow across nanoscale pores in thin films and membranes has a wide range of applications, including characterization of biological ion channels and receptors, DNA sequencing, molecule separation by nanoparticle films, sensing by block co-polymers films, and catalysis through metal–organic frameworks. Ionic conductance through nanopores is often regulated by their 3D structures, a relationship that can be accurately determined only by their simultaneous measurements. However, defining their structure–function relationships directly by any existing techniques is still not possible. Atomic force microscopy (AFM) can image the structures of these pores at high resolution in an aqueous environment, and electrophysiological techniques can measure ion flow through individual nanoscale pores. Combining these techniques is limited by the lack of nanoscale interfaces. We have designed a graphene-based single-nanopore support (∼5 nm thick with ∼20 nm pore diameter) and have integrated AFM imaging and ionic conductance recording using our newly designed double-chamber recording system to study an overlaid thin film. The functionality of this integrated system is demonstrated by electrical recording (<10 pS conductance) of suspended lipid bilayers spanning a nanopore and simultaneous AFM imaging of the bilayer. PMID:24581087

  17. Long-term controlled release of 125I-tagged BMP-2 by mesoporous bioactive glass with ordered nanopores

    PubMed Central

    ZHANG, QUAN; ZHANG, YE; CHEN, WENJUN; ZHANG, BINGWEN; WANG, SHILONG

    2013-01-01

    The aim of this study was to investigate the ability of mesoporous bioactive glass with ordered nanopores (80S MBG) to adsorb and provide the delayed release of 125I-tagged bone morphogenetic protein-2 (BMP-2). A 50 mg piece of 80S MBG was produced, which comprised SiO2, CaO and P2O5 in a component molar ratio of 80:15:5. Each MBG piece adsorbed 30 μg 125I-BMP-2. Persistent radioactivity in the MBG was periodically measured in simulated body fluid. The total amount of BMP-2 released and the mean amount released per day were calculated. A delayed release curve of BMP-2 was constructed. SPSS 15.0 software was used to perform a statistical analysis. The amount of BMP-2 released in the first two days was one-quarter of the total load. A line equation, y = 490.55×1/2 + 7268.82, was obtained from the square root of protein release doses value at 3–94 days. The total amount of BMP-2 released over 94 days was 11.894 μg, which was ~39.6% of the total load. The half-life of the release time was 248 days. From the second week, the rate of BMP release had stabilized to a mean of 37.42±18.67 ng/day and the difference of the mean amount released per day had no statistical significance (P>0.05). High adsorption and delayed release effects of BMP-2 were observed in 80S MBG. The delayed release conforms to the Higuchi equation, which indicates possible applications in promoting bone healing. PMID:24250724

  18. Monolithic nanoporous gold disks with large surface area and high-density plasmonic hot-spots

    NASA Astrophysics Data System (ADS)

    Zhao, Fusheng; Zeng, Jianbo; Arnob, Md Masud Parvez; Santos, Greggy M.; Shih, Wei-Chuan

    2015-03-01

    Plasmonic metal nanostructures have shown great potential in sensing, photovoltaics, imaging and biomedicine, principally due to enhancement of the local electric field by light-excited surface plasmons, the collective oscillation of conduction band electrons. Thin films of nanoporous gold have received a great deal of interest due to the unique 3- dimensional bicontinuous nanostructures with high specific surface area. However, in the form of semi-infinite thin films, nanoporous gold exhibits weak plasmonic extinction and little tunability in the plasmon resonance, because the pore size is much smaller than the wavelength of light. Here we show that by making nanoporous gold in the form of disks of sub-wavelength diameter and sub-100 nm thickness, these limitations can be overcome. Nanoporous gold disks (NPGDs) not only possess large specific surface area but also high-density, internal plasmonic "hot-spots" with impressive electric field enhancement, which greatly promotes plasmon-matter interaction as evidenced by spectral shifts in the surface plasmon resonance. In addition, the plasmonic resonance of NPGD can be easily tuned from 900 to 1850 nm by changing the disk diameter from 300 to 700 nm. The coupling between external and internal nanoarchitecture provides a potential design dimension for plasmonic engineering. The synergy of large specific surface area, high-density hot spots, and tunable plasmonics would profoundly impact applications where plasmonic nanoparticles and non-plasmonic mesoporous nanoparticles are currently employed, e.g., in in-vitro and in-vivo biosensing, molecular imaging, photothermal contrast agents, and molecular cargos.

  19. Facile method for modulating the profiles and periods of self-ordered three-dimensional alumina taper-nanopores.

    PubMed

    Li, Juan; Li, Congshan; Chen, Cheng; Hao, Qingli; Wang, Zhijia; Zhu, Jie; Gao, Xuefeng

    2012-10-24

    We report a facile nanofabrication method, one-step hard anodizing and etching peeling (OS-HA-EP) of aluminum foils followed by multistep mild anodizing and etching pore-widening (MS-MA-EW), for the controllable tailoring of hexagonally packed three-dimensional alumina taper-nanopores. Their profiles can be precisely tailored by the synergistic control of anodizing time, etching time and cyclic times at the MS-MA-EW stage, exemplified by linear cones, whorl-embedded cones, funnels, pencils, parabolas, and trumpets. Meantime, their periods can also be modulated in the range of 70-370 nm by choosing matched anodizing electrolytes (e.g., H(2)C(2)O(4), H(2)SO(4), H(2)C(2)O(4)-H(2)SO(4), and H(2)C(2)O(4)-C(2)H(5)OH mixture) and anodizing voltages at the OS-HA-EP stage. We also demonstrated that the long-range ordering of nanopits and the peak voltage of stable self-ordered HA, which are unachievable in a single H(2)C(2)O(4) electrolyte system, can be effectively tuned by simply adding tiny quantity of H(2)SO(4) and C(2)H(5)OH to keep an appropriate HA current density, respectively. This method of using the combination of simple pure chemical nanofabrication technologies is very facile and efficient in realizing the controllable tailoring of large-area alumina membranes containing self-ordered taper-nanopores. Our work opens a door for exploring the novel physical and chemical properties of different materials of nanotaper arrays. PMID:23020550

  20. High-performance flexible nanoporous Si-carbon nanotube paper anodes for micro-battery applications

    NASA Astrophysics Data System (ADS)

    Biserni, Erika; Scarpellini, Alice; Li Bassi, Andrea; Bruno, Paola; Zhou, Yun; Xie, Ming

    2016-06-01

    Nanoporous Si has been grown by pulsed laser deposition on a free-standing carbon nanotube (CNT) paper sheet for micro-battery anodes. The Si deposition shows conformal coverage on the CNT paper, and the Si-CNT paper anodes demonstrate high areal capacity of ∼1000 μAh cm‑2 at a current density of 54 μA cm‑2, while 69% of its initial capacity is preserved when the current density is increased by a factor 10. Excellent stability without capacity decay up to 1000 cycles at a current density of 1080 μA cm‑2 is also demonstrated. After bending along the diameter of the circular paper disc many times, the Si-CNT paper anodes preserve the same morphology and show promising electrochemical performance, indicating that nanoporous Si-CNT paper anodes can find application for flexible micro-batteries.

  1. The fabrication of highly ordered block copolymer micellar arrays: control of the separation distances of silicon oxide dots.

    PubMed

    Yoo, Hana; Park, Soojin

    2010-06-18

    We demonstrate the fabrication of highly ordered silicon oxide dotted arrays prepared from polydimethylsiloxane (PDMS) filled nanoporous block copolymer (BCP) films and the preparation of nanoporous, flexible Teflon or polyimide films. Polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) films were annealed in toluene vapor to enhance the lateral order of micellar arrays and were subsequently immersed in alcohol to produce nano-sized pores, which can be used as templates for filling a thin layer of PDMS. When a thin layer of PDMS was spin-coated onto nanoporous BCP films and thermally annealed at a certain temperature, the PDMS was drawn into the pores by capillary action. PDMS filled BCP templates were exposed to oxygen plasma environments in order to fabricate silicon oxide dotted arrays. By addition of PS homopolymer to PS-b-P2VP copolymer, the separation distances of micellar arrays were tuned. As-prepared silicon oxide dotted arrays were used as a hard master for fabricating nanoporous Teflon or polyimide films by spin-coating polymer precursor solutions onto silicon patterns and peeling off. This simple process enables us to fabricate highly ordered nanoporous BCP templates, silicon oxide dots, and flexible nanoporous polymer patterns with feature size of sub-20 nm over 5 cm x 5 cm. PMID:20498523

  2. Nanoporous framework materials interfaced with mechanical sensors for highly-sensitive chemical sensing.

    SciTech Connect

    Lee, Jin-Hwan; Skinner, Jack L.; Houk, Ronald J. T.; Fischer, Roland A.; Robinson, Alex Lockwood; Allendorf, Mark D.; Yusenko, Kirill; Meilikhov, Mikhail; Hesketh, Peter J.; Venkatasubramanian, Anandram; Thornberg, Steven Michael

    2010-04-01

    We will describe how novel nanoporous framework materials (NFM) such as metal-organic frameworks (MOFs) can be interfaced with common mechanical sensors, such as surface acoustic wave (SAW), microcantilever array, and quartz crystal microbalance (QCM) devices, and subsequently be used to provide selectivity and sensitivity to a broad range of analytes including explosives, nerve agents, and volatile organic compounds (VOCs). NFM are highly ordered, crystalline materials with considerable synthetic flexibility resulting from the presence of both organic and inorganic components within their structure. Chemical detection using micro-electro-mechanical-systems (MEMS) devices (i.e. SAWs, microcantilevers) requires the use of recognition layers to impart selectivity. Unlike traditional organic polymers, which are dense, the nanoporosity and ultrahigh surface areas of NFM allow for greater analyte uptake and enhance transport into and out of the sensing layer. This enhancement over traditional coatings leads to improved response times and greater sensitivity, while their ordered structure allows chemical tuning to impart selectivity. We describe here experiments and modeling aimed at creating NFM layers tailored to the detection of water vapor, explosives, CWMD, and volatile organic compound (VOCs), and their integration with the surfaces of MEMS devices. Molecular simulation shows that a high degree of chemical selectivity is feasible. For example, a suite of MOFs can select for strongly interacting organics (explosives, CWMD) vs. lighter volatile organics at trace concentrations. At higher gas pressures, the CWMD are deselected in favor of the volatile organics. We will also demonstrate the integration of various NFM on the surface of microcantiliver arrays, QCM crystals, and SAW devices, and describe new synthetic methods developed to improve the quality of NFM coatings. Finally, MOF-coated MEMS devices show how temperature changes can be tuned to improve response

  3. Fabrication of ultra-high aspect ratio silicon nanopores by electrochemical etching

    SciTech Connect

    Schmidt, Torsten; Zhang, Miao; Linnros, Jan; Yu, Shun

    2014-09-22

    We report on the formation of ultra-high aspect ratio nanopores in silicon bulk material using photo-assisted electrochemical etching. Here, n-type silicon is used as anode in contact with hydrofluoric acid. Based on the local dissolution of surface atoms in pre-defined etching pits, pore growth and pore diameter are, respectively, driven and controlled by the supply of minority charge carriers generated by backside illumination. Thus, arrays with sub-100 nm wide pores were fabricated. Similar to macropore etching, it was found that the pore diameter is proportional to the etching current, i.e., smaller etching currents result in smaller pore diameters. To find the limits under which nanopores with controllable diameter still can be obtained, etching was performed at very low current densities (several μA cm{sup −2}). By local etching, straight nanopores with aspect ratios above 1000 (∼19 μm deep and ∼15 nm pore tip diameter) were achieved. However, inherent to the formation of such narrow pores is a radius of curvature of a few nanometers at the pore tip, which favors electrical breakdown resulting in rough pore wall morphologies. Lowering the applied bias is adequate to reduce spiking pores but in most cases also causes etch stop. Our findings on bulk silicon provide a realistic chance towards sub-10 nm pore arrays on silicon membranes, which are of great interest for molecular filtering and possibly DNA sequencing.

  4. A Low-Noise Solid-State Nanopore Platform Based on a Highly Insulating Substrate

    PubMed Central

    Lee, Min-Hyun; Kumar, Ashvani; Park, Kyeong-Beom; Cho, Seong-Yong; Kim, Hyun-Mi; Lim, Min-Cheol; Kim, Young-Rok; Kim, Ki-Bum

    2014-01-01

    A solid-state nanopore platform with a low noise level and sufficient sensitivity to discriminate single-strand DNA (ssDNA) homopolymers of poly-A40 and poly-T40 using ionic current blockade sensing is proposed and demonstrated. The key features of this platform are (a) highly insulating dielectric substrates that are used to mitigate the effect of parasitic capacitance elements, which decrease the ionic current RMS noise level to sub-10 pA and (b) ultra-thin silicon nitride membranes with a physical thickness of 5 nm (an effective thickness of 2.4 nm estimated from the ionic current) are used to maximize the signal-to-noise ratio and the spatial depth resolution. The utilization of an ultra-thin membrane and a nanopore diameter as small as 1.5 nm allow the successful discrimination of 40 nucleotide ssDNA poly-A40 and poly-T40. Overall, we demonstrate that this platform overcomes several critical limitations of solid-state nanopores and opens the door to a wide range of applications in single-molecule-based detection and analysis. PMID:25502421

  5. Pt-Al2O3 dual layer atomic layer deposition coating in high aspect ratio nanopores

    NASA Astrophysics Data System (ADS)

    Pardon, Gaspard; Gatty, Hithesh K.; Stemme, Göran; van der Wijngaart, Wouter; Roxhed, Niclas

    2013-01-01

    Functional nanoporous materials are promising for a number of applications ranging from selective biofiltration to fuel cell electrodes. This work reports the functionalization of nanoporous membranes using atomic layer deposition (ALD). ALD is used to conformally deposit platinum (Pt) and aluminum oxide (Al2O3) on Pt in nanopores to form a metal-insulator stack inside the nanopore. Deposition of these materials inside nanopores allows the addition of extra functionalities to nanoporous materials such as anodic aluminum oxide (AAO) membranes. Conformal deposition of Pt on such materials enables increased performances for electrochemical sensing applications or fuel cell electrodes. An additional conformal Al2O3 layer on such a Pt film forms a metal-insulator-electrolyte system, enabling field effect control of the nanofluidic properties of the membrane. This opens novel possibilities in electrically controlled biofiltration. In this work, the deposition of these two materials on AAO membranes is investigated theoretically and experimentally. Successful process parameters are proposed for a reliable and cost-effective conformal deposition on high aspect ratio three-dimensional nanostructures. A device consisting of a silicon chip supporting an AAO membrane of 6 mm diameter and 1.3 μm thickness with 80 nm diameter pores is fabricated. The pore diameter is reduced to 40 nm by a conformal deposition of 11 nm Pt and 9 nm Al2O3 using ALD.

  6. High-speed event detector for embedded nanopore bio-systems.

    PubMed

    Huang, Yiyun; Magierowski, Sebastian; Ghafar-Zadeh, Ebrahim; Wang, Chengjie

    2015-08-01

    Biological measurements of microscopic phenomena often deal with discrete-event signals. The ability to automatically carry out such measurements at high-speed in a miniature embedded system is desirable but compromised by high-frequency noise along with practical constraints on filter quality and sampler resolution. This paper presents a real-time event-detection method in the context of nanopore sensing that helps to mitigate these drawbacks and allows accurate signal processing in an embedded system. Simulations show at least a 10× improvement over existing on-line detection methods. PMID:26736722

  7. Ion Beam Nanosculpting and Materials Science with Single Nanopores

    SciTech Connect

    Golovchenko, J A; Branton, D

    2009-10-03

    Work is reported in these areas: Nanopore studies; Ion sculpting of metals; High energy ion sculpting; Metrology of nanopores with single wall carbon nanotube probes; Capturing molecules in a nanopore; Strand separation in a nanopore; and DNA molecules and configurations in solid-state nanopores.

  8. Ionic transport through sub-10 nm diameter hydrophobic high-aspect ratio nanopores: experiment, theory and simulation

    PubMed Central

    Balme, Sébastien; Picaud, Fabien; Manghi, Manoel; Palmeri, John; Bechelany, Mikhael; Cabello-Aguilar, Simon; Abou-Chaaya, Adib; Miele, Philippe; Balanzat, Emmanuel; Janot, Jean Marc

    2015-01-01

    Fundamental understanding of ionic transport at the nanoscale is essential for developing biosensors based on nanopore technology and new generation high-performance nanofiltration membranes for separation and purification applications. We study here ionic transport through single putatively neutral hydrophobic nanopores with high aspect ratio (of length L = 6 μm with diameters ranging from 1 to 10 nm) and with a well controlled cylindrical geometry. We develop a detailed hybrid mesoscopic theoretical approach for the electrolyte conductivity inside nanopores, which considers explicitly ion advection by electro-osmotic flow and possible flow slip at the pore surface. By fitting the experimental conductance data we show that for nanopore diameters greater than 4 nm a constant weak surface charge density of about 10−2 C m−2 needs to be incorporated in the model to account for conductance plateaus of a few pico-siemens at low salt concentrations. For tighter nanopores, our analysis leads to a higher surface charge density, which can be attributed to a modification of ion solvation structure close to the pore surface, as observed in the molecular dynamics simulations we performed. PMID:26036687

  9. Nanoporous plasmonic metamaterials

    SciTech Connect

    Biener, J; Nyce, G W; Hodge, A M; Biener, M M; Hamza, A V; Maier, S A

    2007-05-24

    We review different routes for the generation of nanoporous metallic foams and films exhibiting well-defined pore size and short-range order. Dealloying and templating allows the generation of both two- and three-dimensional structures which promise a well defined plasmonic response determined by material constituents and porosity. Viewed in the context of metamaterials, the ease of fabrication of samples covering macroscopic dimensions is highly promising, and suggests more in-depth investigations of the plasmonic and photonic properties of this material system for photonic applications.

  10. High Capacity Nanoporous Silicon Carrier for Systemic Delivery of Gene Silencing Therapeutics

    PubMed Central

    Kim, Han-Cheon; Guo, Xiaojing; Qin, Guoting; Yang, Yong; Wolfram, Joy; Mu, Chaofeng; Xia, Xiaojun; Gu, Jianhua; Liu, Xuewu; Mao, Zong-Wan; Ferrari, Mauro; Shen, Haifa

    2013-01-01

    Gene silencing agents such as small interfering RNA (siRNA) and microRNA offer the promise to modulate expression of almost every gene for the treatment of human diseases including cancer. However, lack of vehicles for effective systemic delivery to the disease organs has greatly limited their in vivo applications. In this study, we developed a high capacity polycation-functionalized nanoporous silicon (PCPS) platform comprised of nanoporous silicon microparticles functionalized with arginine-polyethyleneimine inside the nanopores for effective delivery of gene silencing agents. Incubation of MDA-MB-231 human breast cancer cells with PCPS loaded with STAT3 siRNA (PCPS/STAT3) or GRP78 siRNA (PCPS/GRP78) resulted in 91% and 83% reduction of STAT3 and GRP78 gene expression in vitro. Treatment of cells with a microRNA-18a mimic in PCPS (PCPS/miR-18) knocked down 90% expression of the microRNA-18a target gene ATM. Systemic delivery of PCPS/STAT3 siRNA in murine model of MDA-MB-231 breast cancer enriched particles in tumor tissues and reduced STAT3 expression in cancer cells, causing significant reduction of cancer stem cells in the residual tumor tissue. At the therapeutic dosage, PCPS/STAT3 siRNA did not trigger acute immune response in FVB mice, including changes in serum cytokines, chemokines and colony-stimulating factors. In addition, weekly dosing of PCPS/STAT3 siRNA for four weeks did not cause signs of sub-acute toxicity based on changes in body weight, hematology, blood chemistry, and major organ histology. Collectively, the results suggest that we have developed a safe vehicle for effective delivery of gene silencing agents. PMID:24131405

  11. Photoelectrocatalytic degradation of tetracycline by highly effective TiO2 nanopore arrays electrode.

    PubMed

    Liu, Yanbiao; Gan, Xiaojie; Zhou, Baoxue; Xiong, Bitao; Li, Jinhua; Dong, Chaoping; Bai, Jing; Cai, Weimin

    2009-11-15

    The widely utilization of pharmaceutical and personal care products (PPCPs) in the pharmaceutical therapies and agricultural husbandry has led to the worldwide pollution in the environment. In this study, the photoelectrocatalytic (PEC) behaviors of typical PPCPs, tetracycline (TC), were performed via a highly effective TiO(2) nanopore arrays (TNPs) electrode, comparing with electrochemical (EC) and photocatalytic (PC) process. A significant photoelectrochemical synergetic effect in TC degradation was observed on the TNPs electrode and the rate constant for the PEC process of TNPs electrode was approximately 6.7 times as high as its PC process. The TC removal rate achieved approximately 80% within 3h PEC reaction by TNPs electrode, which is approximately 25% higher than that obtained for a conventional coated TiO(2) nanofilm electrode fabricated by sol-gel method. The possible mechanism involved in the PEC degradation of TC by TNPs electrode was discussed. Furthermore, the TNPs electrode also shows enhanced photocurrent response compared with that for the coated TiO(2) nanofilm electrode. Such kind of TiO(2) nanopores will have many potential applications in various areas as an outstanding photoelectrochemical material. PMID:19577843

  12. Electric double-layer capacitors based on highly graphitized nanoporous carbons derived from ZIF-67.

    PubMed

    Torad, Nagy L; Salunkhe, Rahul R; Li, Yunqi; Hamoudi, Hicham; Imura, Masataka; Sakka, Yoshio; Hu, Chi-Chang; Yamauchi, Yusuke

    2014-06-23

    Nanoporous carbons (NPCs) have large specific surface areas, good electrical and thermal conductivity, and both chemical and mechanical stability, which facilitate their use in energy storage device applications. In the present study, highly graphitized NPCs are synthesized by one-step direct carbonization of cobalt-containing zeolitic imidazolate framework-67 (ZIF-67). After chemical etching, the deposited Co content can be completely removed to prepare pure NPCs with high specific surface area, large pore volume, and intrinsic electrical conductivity (high content of sp(2) -bonded carbons). A detailed electrochemical study is performed using cyclic voltammetry and galvanostatic charge-discharge measurements. Our NPC is very promising for efficient electrodes for high-performance supercapacitor applications. A maximum specific capacitance of 238 F g(-1) is observed at a scan rate of 20 mV s(-1) . This value is very high compared to previous works on carbon-based electric double layer capacitors. PMID:24788922

  13. Nanoporous, Metal Carbide, Surface Diffusion Membranes for High Temperature Hydrogen Separations

    SciTech Connect

    Way, J.; Wolden, Colin

    2013-09-30

    Colorado School of Mines (CSM) developed high temperature, hydrogen permeable membranes that contain no platinum group metals with the goal of separating hydrogen from gas mixtures representative of gasification of carbon feedstocks such as coal or biomass in order to meet DOE NETL 2015 hydrogen membrane performance targets. We employed a dual synthesis strategy centered on transition metal carbides. In the first approach, novel, high temperature, surface diffusion membranes based on nanoporous Mo{sub 2}C were fabricated on ceramic supports. These were produced in a two step process that consisted of molybdenum oxide deposition followed by thermal carburization. Our best Mo{sub 2}C surface diffusion membrane achieved a pure hydrogen flux of 367 SCFH/ft{sup 2} at a feed pressure of only 20 psig. The highest H{sub 2}/N{sub 2} selectivity obtained with this approach was 4.9. A transport model using “dusty gas” theory was derived to describe the hydrogen transport in the Mo{sub 2}C coated, surface diffusion membranes. The second class of membranes developed were dense metal foils of BCC metals such as vanadium coated with thin (< 60 nm) Mo{sub 2}C catalyst layers. We have fabricated a Mo{sub 2}C/V composite membrane that in pure gas testing delivered a H{sub 2} flux of 238 SCFH/ft{sup 2} at 600 °C and 100 psig, with no detectable He permeance. This exceeds the 2010 DOE Target flux. This flux is 2.8 times that of pure Pd at the same membrane thickness and test conditions and over 79% of the 2015 flux target. In mixed gas testing we achieved a permeate purity of ≥99.99%, satisfying the permeate purity milestone, but the hydrogen permeance was low, ~0.2 SCFH/ft{sup 2}.psi. However, during testing of a Mo{sub 2}C coated Pd alloy membrane with DOE 1 feed gas mixture a hydrogen permeance of >2 SCFH/ft{sup 2}.psi was obtained which was stable during the entire test, meeting the permeance associated with the 2010 DOE target flux. Lastly, the Mo{sub 2}C/V composite

  14. Nanoporous gold supported cobalt oxide microelectrodes as high-performance electrochemical biosensors.

    PubMed

    Lang, Xing-You; Fu, Hong-Ying; Hou, Chao; Han, Gao-Feng; Yang, Ping; Liu, Yong-Bing; Jiang, Qing

    2013-01-01

    Tremendous demands for electrochemical biosensors with high sensitivity and reliability, fast response and excellent selectivity have stimulated intensive research on developing versatile materials with ultrahigh electrocatalytic activity. Here we report flexible and self-supported microelectrodes with a seamless solid/nanoporous gold/cobalt oxide hybrid structure for electrochemical nonenzymatic glucose biosensors. As a result of synergistic electrocatalytic activity of the gold skeleton and cobalt oxide nanoparticles towards glucose oxidation, amperometric glucose biosensors based on the hybrid microelectrodes exhibit multi-linear detection ranges with ultrahigh sensitivities at a low potential of 0.26 V (versus Ag/AgCl). The sensitivity up to 12.5 mA mM⁻¹ cm⁻² with a short response time of less than 1 s gives rise to ultralow detection limit of 5 nM. The outstanding performance originates from a novel nanoarchitecture in which the cobalt oxide nanoparticles are incorporated into pore channels of the seamless solid/nanoporous Au microwires, providing excellent electronic/ionic conductivity and mass transport for the enhanced electrocatalysis. PMID:23851924

  15. Retroreflection of light from nanoporous InP: correlation with high absorption

    NASA Astrophysics Data System (ADS)

    Prislopski, S. Ya.; Tiginyanu, I. M.; Ghimpu, L.; Monaico, E.; Sirbu, L.; Gaponenko, S. V.

    2014-09-01

    Pronounced retroreflection behavior is reported for a fishnet nanoporous strongly absorbing semiconductor material. Retroreflection appears along with diffusive specular reflection for all angles of incidence for light wavelength corresponding to interband optical transitions, where absorption coefficient is of the order of 105 cm-1 (green and red light). Retroreflection is apparent by the naked eye with daylight illumination and exhibits no selectivity with respect to wavelength and polarization of incident light featuring minor depolarization of retroreflected light. Retroreflection vanishes for wavelength corresponding to optical transparency range where photon energy is lower than the InP bandgap (1.064 μm). The phenomenon can be classified neither as coherent backscattering nor as Anderson localization of light. The primary model includes light scattering from strongly absorptive and refractive super-wavelength clusters existing within the porous fishnet structure. We found that retroreflection vanishes for wavelength where absorption becomes negligible.

  16. DNA translocation through graphene nanopores.

    PubMed

    Merchant, Christopher A; Healy, Ken; Wanunu, Meni; Ray, Vishva; Peterman, Neil; Bartel, John; Fischbein, Michael D; Venta, Kimberly; Luo, Zhengtang; Johnson, A T Charlie; Drndić, Marija

    2010-08-11

    We report on DNA translocations through nanopores created in graphene membranes. Devices consist of 1-5 nm thick graphene membranes with electron-beam sculpted nanopores from 5 to 10 nm in diameter. Due to the thin nature of the graphene membranes, we observe larger blocked currents than for traditional solid-state nanopores. However, ionic current noise levels are several orders of magnitude larger than those for silicon nitride nanopores. These fluctuations are reduced with the atomic-layer deposition of 5 nm of titanium dioxide over the device. Unlike traditional solid-state nanopore materials that are insulating, graphene is an excellent electrical conductor. Use of graphene as a membrane material opens the door to a new class of nanopore devices in which electronic sensing and control are performed directly at the pore. PMID:20698604

  17. DNA-based detection of mercury(ii) ions through characteristic current signals in nanopores with high sensitivity and selectivity

    NASA Astrophysics Data System (ADS)

    Zeng, Tao; Li, Ting; Li, Yuru; Liu, Lei; Wang, Xingyong; Liu, Quansheng; Zhao, Yuliang; Wu, Hai-Chen

    2014-07-01

    We report single-molecule detection of Hg2+ by threading an Hg2+-mediated DNA duplex through α-hemolysin nanopores, which generates characteristic three-level current patterns and enables the unambiguous detection of Hg2+. This strategy precludes any background interference and features high sensitivity and selectivity. Moreover, the platform could be readily integrated with aptamers and molecular beacons, offering extended possibilities for the construction of a new DNA-based nanopore sensing system.We report single-molecule detection of Hg2+ by threading an Hg2+-mediated DNA duplex through α-hemolysin nanopores, which generates characteristic three-level current patterns and enables the unambiguous detection of Hg2+. This strategy precludes any background interference and features high sensitivity and selectivity. Moreover, the platform could be readily integrated with aptamers and molecular beacons, offering extended possibilities for the construction of a new DNA-based nanopore sensing system. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr02062f

  18. Nanoporous Structure and Medium-Range Order in Synthetic Amorphous Calcium Carbonate

    SciTech Connect

    Goodwin, Andrew L.; Michel, F. Marc; Phillips, Brian L.; Keen, David A.; Dove, Martin T.; Reeder, Richard J.

    2010-12-03

    We adopt a reverse Monte Carlo refinement approach, using experimental X-ray total scattering data, to develop a structure model for synthetic, hydrated amorphous calcium carbonate (ACC). The ACC is revealed to consist of a porous calcium-rich framework that supports interconnected channels containing water and carbonate molecules. The existence of a previously unrecognized nanometer-scale channel network suggests mechanisms of how additives can be accommodated within the structure and provide temporary stabilization, as well as influence the crystallization process. Moreover, while lacking long-range order, the calcium-rich framework in the ACC contains similar Ca packing density to that present in calcite, aragonite, and vaterite, yielding clues of how the amorphous material converts into the different crystalline forms. Our results provide a new starting point for advancing our understanding of biomineralization as well as the development of biomimetic approaches to next-generation materials synthesis.

  19. 3D SERS Imaging Using Chemically Synthesized Highly Symmetric Nanoporous Silver Microparticles.

    PubMed

    Vantasin, Sanpon; Ji, Wei; Tanaka, Yoshito; Kitahama, Yasutaka; Wang, Mengfan; Wongravee, Kanet; Gatemala, Harnchana; Ekgasit, Sanong; Ozaki, Yukihiro

    2016-07-11

    3D surface-enhanced Raman scattering (SERS) imaging with highly symmetric 3D silver microparticles as a SERS substrate was developed. Although the synthesis method is purely chemical and does not involve lithography, the synthesized nanoporous silver microparticles possess a regular hexapod shape and octahedral symmetry. By using p-aminothiophenol (PATP) as a probe molecule, the 3D enhancement patterns of the particles were shown to be very regular and predictable, resembling the particle shape and exhibiting symmetry. An application to the detection of 3D inhomogeneity in a polymer blend, which relies on the predictable enhancement pattern of the substrate, is presented. 3D SERS imaging using the substrate also provides an improvement in spatial resolution along the Z axis, which is a challenge for Raman measurement in polymers, especially layered polymeric systems. PMID:27240138

  20. Generalized high order compact methods.

    SciTech Connect

    Spotz, William F.; Kominiarczuk, Jakub

    2010-09-01

    The fundamental ideas of the high order compact method are combined with the generalized finite difference method. The result is a finite difference method that works on unstructured, nonuniform grids, and is more accurate than one would classically expect from the number of grid points employed.

  1. Highly-Ordered Thin Films from Photocleavable Block Copolymers

    NASA Astrophysics Data System (ADS)

    Gu, Weiyin; Zhao, Hui; Coughlin, E.; Theato, Patrick; Russell, Thomas; University of Massachusetts at Amherst Team; University of Hamburg Team

    2013-03-01

    A robust route for the preparation of nanoscopic dot/line patterns with long range lateral order from poly(styrene-block-ethylene oxide) (PS-b-PEO) with an o-nitrobenzyl ester junction (PS-h ν-PEO) is demonstrated. Solvent annealing condition is optimized to achieve the highly ordered cylindrical block copolymer (BCP) microdomains oriented normal or parallel to the silicon substrates. Following a very mild UV exposure and successive washing with methanol, PS-hv-PEO thin films were transformed into highly ordered porous or trench templates. Afterwards the pores or trenches were either filled with PDMS by spin-coating or exposed to direct metal deposition of Au. After a plasma etching or lift-off process to remove the polymer templates, highly ordered arrays of silica or Au nanopatterns were obtained. This represents the first template application example from highly ordered nanoporous thin films derived from block copolymers featuring a photocleavable junction. DOE (DE-FG02-96ER45612), NSF-MRSEC, DFG (TH 1104/4-1), CHE 0924435, R31-10013.

  2. Preparation of 3D nanoporous copper-supported cuprous oxide for high-performance lithium ion battery anodes.

    PubMed

    Liu, Dequan; Yang, Zhibo; Wang, Peng; Li, Fei; Wang, Desheng; He, Deyan

    2013-03-01

    Three-dimensional (3D) nanoporous architectures can provide efficient and rapid pathways for Li-ion and electron transport as well as short solid-state diffusion lengths in lithium ion batteries (LIBs). In this work, 3D nanoporous copper-supported cuprous oxide was successfully fabricated by low-cost selective etching of an electron-beam melted Cu(50)Al(50) alloy and subsequent in situ thermal oxidation. The architecture was used as an anode in lithium ion batteries. In the first cycle, the sample delivered an extremely high lithium storage capacity of about 2.35 mA h cm(-2). A high reversible capacity of 1.45 mA h cm(-2) was achieved after 120 cycles. This work develops a promising approach to building reliable 3D nanostructured electrodes for high-performance lithium ion batteries. PMID:23354412

  3. Atomically thin molybdenum disulfide nanopores with high sensitivity for DNA translocation.

    PubMed

    Liu, Ke; Feng, Jiandong; Kis, Andras; Radenovic, Aleksandra

    2014-03-25

    Atomically thin nanopore membranes are considered to be a promising approach to achieve single base resolution with the ultimate aim of rapid and cheap DNA sequencing. Molybdenum disulfide (MoS2) is newly emerging as a material complementary to graphene due to its semiconductive nature and other interesting physical properties that can enable a wide range of potential sensing and nanoelectronics applications. Here, we demonstrate that monolayer or few-layer thick exfoliated MoS2 with subnanometer thickness can be transferred and suspended on a predesigned location on the 20 nm thick SiNx membranes. Nanopores in MoS2 are further sculpted with variable sizes using a transmission electron microscope (TEM) to drill through suspended portions of the MoS2 membrane. Various types of double-stranded (ds) DNA with different lengths and conformations are translocated through such a novel architecture, showing improved sensitivity (signal-to-noise ratio>10) compared to the conventional silicon nitride (SiNx) nanopores with tens of nanometers thickness. Unlike graphene nanopores, no special surface treatment is needed to avoid hydrophobic interaction between DNA and the surface. Our results imply that MoS2 membranes with nanopore can complement graphene nanopore membranes and offer potentially better performance in transverse detection. PMID:24547924

  4. Thermoresponsive Ultrathin Membranes with Precisely Tuned Nanopores for High-Flux Separation.

    PubMed

    Zhu, Yuzhang; Gao, Shoujian; Hu, Liang; Jin, Jian

    2016-06-01

    With the growing demand for small- and large-scale bioprocesses, advanced membranes with high energy efficiency are highly required. However, conventional polymer-based membranes often have to sacrifice selectivity for permeability. In this work, we report the fabrication of a thermoresponsive composite ultrathin membrane with precisely controlled nanopores for high-throughput separation. The composite membrane is made by grafting a PEG analogue thermoresponsive copolymer onto an ultrathin single-wall carbon nanotubes (SWCNTs) membrane via π-π interaction with no use of the common "grafting from" synthesis approach. The composite membrane exhibits ultrahigh water permeation flux as high as 6430 L m(-2) h(-1) at 40 °C, and more importantly, the pore size of the membrane could be finely adjusted by utilizing the thermoresponsive property of the grafted copolymer. With the temperature changing below and above the lower critical solution temperature (LCST) of the copolymer, the effective pore size of the membrane can be tuned precisely between approximately 12 and 14 nm, which could be applied to effectively separate materials with very small size differences through size sieving. PMID:27177239

  5. Fabrication of a high-density nano-porous structure on polyimide by using ultraviolet laser irradiation

    NASA Astrophysics Data System (ADS)

    Ma, Yong-Won; Jeong, Myung Yung; Lee, Sang-Mae; Shin, Bo Sung

    2016-03-01

    A new approach for fabricating a high-density nano-porous structure on polyimide (PI) by using a 355-nm UV laser is presented here. When PI was irradiated by using a laser, debris that had electrical conductivity was generated. Accordingly, that debris caused electrical defects in the field of electronics. Thus, many researchers have tried to focus on a clean processing without debris. However, this study focused on forming a high density of debris so as to fabricate a nano-porous structure consisting of nanofibers on the PI film. A PI film with closed pores and open pores was successfully formed by using a chemical blowing agent (azodicarbonamide, CBA) in an oven. Samples were precured at 130 °C and cured at 205 °C in sequence so that the closed pores might not coalesce in the film. When the laser irradiated the PI film with closed pores, nanofibers were generated because polyimide was not completely decomposed by photochemical ablation. Our results indicated that a film with micro-closed pores, in conjunction with a 355-nm pulsed laser, can facilitate the fabrication of a high-density nano-porous structure.

  6. Synthesis and characterization of nanoporous silica film via non-surfactant template sol-gel technique

    NASA Astrophysics Data System (ADS)

    Al-Harbi, T.; Al-Hazmi, F.; Mahmoud, Waleed E.

    2012-10-01

    Nanoporous silicon dioxide has received growing interests owing to their peculiar application potentials in conservation and storage energy. Therefore, the development of novel and simple techniques is required for raising these nanoporous materials to industrial level. In this research, we report novel strategy for the synthesis of nanoporous SiO2 via non-surfactant template sol-gel technique for the first time. The morphology and structure of the as prepared and annealed nanoporous silica films were studied using X-ray diffraction, scanning electron microscope, Fourier transform infrared spectroscopy and nitrogen absorption/desorption technique. The results showed that highly order nanoporous silica film has been obtained at annealing temperature 600 °C with average diameter 5.1 nm and average pore volume 3.6 cm3 g-1.

  7. Room temperature NO2 sensor based on highly ordered porphyrin nanotubes.

    PubMed

    Song, Feifei; Ma, Pan; Chen, Changlong; Jia, Jingna; Wang, Yucheng; Zhu, Peihua

    2016-07-15

    Highly ordered nanotubes of 5, 10, 15, 20-tetrakis(4-aminophenyl)porphyrin zinc (ZnTAP) are fabricated by using nanoporous anodized aluminum oxide (AAO) membrane as the template. Electronic absorption spectra, fluorescence spectra, transmission electron microscope (TEM), scanning electronic microscopy (SEM), low-angle X-ray diffraction (XRD) techniques are adopted to characterize these nanotubes. The highly ordered nanotubes of ZnTAP show good conductivity and present an efficient gas sensor platform for the ultrasensitive detection of NO2 under room temperature. The proposed sensor shows high sensitivity, reproducibility and fast response/recovery behavior, and provides a promising avenue for improving the sensing performance. PMID:27100904

  8. Size control of nanopores formed on SiO{sub 2} glass by swift-heavy-ion irradiation and its application to highly sensitive biomolecular detection

    SciTech Connect

    Nomura, Ken-ichi; Fujimaki, Makoto; Awazu, Koichi; Komatsubara, Tetsuro

    2011-09-15

    Swift-heavy-ion irradiation creates latent tracks in SiO{sub 2} glass and nanopores with a high aspect ratio can be formed along these ion paths by selective etching of the latent tracks using hydrogen fluoride (HF) vapor. Here we report that the size of nanopores can easily be controlled by simply changing the temperature of the HF solution generating the vapor and/or that of the SiO{sub 2} glass exposed to the vapor. Furthermore, this method of size control was used to produce SiO{sub 2} glass sheets with nanopores of different sizes and number densities for use as the waveguide layer in the sensing plates for a waveguide-mode sensor. In comparison with nonperforated plates, the increased surface area due to the formation of nanopores was found to create up to a tenfold increase in sensitivity.

  9. Highly sensitive nano-porous lattice biosensor based on localized surface plasmon resonance and interference.

    PubMed

    Yeom, Se-Hyuk; Kim, Ok-Geun; Kang, Byoung-Ho; Kim, Kyu-Jin; Yuan, Heng; Kwon, Dae-Hyuk; Kim, Hak-Rin; Kang, Shin-Won

    2011-11-01

    We propose a design for a highly sensitive biosensor based on nanostructured anodized aluminum oxide (AAO) substrates. A gold-deposited AAO substrate exhibits both optical interference and localized surface plasmon resonance (LSPR). In our sensor, application of these disparate optical properties overcomes problems of limited sensitivity, selectivity, and dynamic range seen in similar biosensors. We fabricated uniform periodic nanopore lattice AAO templates by two-step anodizing and assessed their suitability for application in biosensors by characterizing the change in optical response on addition of biomolecules to the AAO template. To determine the suitability of such structures for biosensing applications, we immobilized a layer of C-reactive protein (CRP) antibody on a gold coating atop an AAO template. We then applied a CRP antigen (Ag) atop the immobilized antibody (Ab) layer. The shift in reflectance is interpreted as being caused by the change in refractive index with membrane thickness. Our results confirm that our proposed AAO-based biosensor is highly selective toward detection of CRP antigen, and can measure a change in CRP antigen concentration of 1 fg/ml. This method can provide a simple, fast, and sensitive analysis for protein detection in real-time. PMID:22109166

  10. Ion selection of charge-modified large nanopores in a graphene sheet

    NASA Astrophysics Data System (ADS)

    Zhao, Shijun; Xue, Jianming; Kang, Wei

    2013-09-01

    Water desalination becomes an increasingly important approach for clean water supply to meet the rapidly growing demand of population boost, industrialization, and urbanization. The main challenge in current desalination technologies lies in the reduction of energy consumption and economic costs. Here, we propose to use charged nanopores drilled in a graphene sheet as ion exchange membranes to promote the efficiency and capacity of desalination systems. Using molecular dynamics simulations, we investigate the selective ion transport behavior of electric-field-driven KCl electrolyte solution through charge modified graphene nanopores. Our results reveal that the presence of negative charges at the edge of graphene nanopore can remarkably impede the passage of Cl- while enhance the transport of K+, which is an indication of ion selectivity for electrolytes. We further demonstrate that this selectivity is dependent on the pore size and total charge number assigned at the nanopore edge. By adjusting the nanopore diameter and electric charge on the graphene nanopore, a nearly complete rejection of Cl- can be realized. The electrical resistance of nanoporous graphene, which is a key parameter to evaluate the performance of ion exchange membranes, is found two orders of magnitude lower than commercially used membranes. Our results thus suggest that graphene nanopores are promising candidates to be used in electrodialysis technology for water desalinations with a high permselectivity.

  11. Ion selection of charge-modified large nanopores in a graphene sheet.

    PubMed

    Zhao, Shijun; Xue, Jianming; Kang, Wei

    2013-09-21

    Water desalination becomes an increasingly important approach for clean water supply to meet the rapidly growing demand of population boost, industrialization, and urbanization. The main challenge in current desalination technologies lies in the reduction of energy consumption and economic costs. Here, we propose to use charged nanopores drilled in a graphene sheet as ion exchange membranes to promote the efficiency and capacity of desalination systems. Using molecular dynamics simulations, we investigate the selective ion transport behavior of electric-field-driven KCl electrolyte solution through charge modified graphene nanopores. Our results reveal that the presence of negative charges at the edge of graphene nanopore can remarkably impede the passage of Cl(-) while enhance the transport of K(+), which is an indication of ion selectivity for electrolytes. We further demonstrate that this selectivity is dependent on the pore size and total charge number assigned at the nanopore edge. By adjusting the nanopore diameter and electric charge on the graphene nanopore, a nearly complete rejection of Cl(-) can be realized. The electrical resistance of nanoporous graphene, which is a key parameter to evaluate the performance of ion exchange membranes, is found two orders of magnitude lower than commercially used membranes. Our results thus suggest that graphene nanopores are promising candidates to be used in electrodialysis technology for water desalinations with a high permselectivity. PMID:24070300

  12. Guest-dependent high pressure phenomena in a nanoporous metal-organic framework material.

    PubMed

    Chapman, Karena W; Halder, Gregory J; Chupas, Peter J

    2008-08-13

    The nanoporous metal-organic framework material Cu3(1,3,5-benzenetricarboxylate)2(H2O)3.{guest} exhibits anomalous compression under applied pressure that is associated with the hyper-filling of the pore network. This behavior involves a dramatic transition between a "hard" regime (bulk modulus, Khard approximately 118 GPa), where the pressure-transmitting fluid penetrates the framework cavities, and a "soft" regime (Ksoft approximately 30 GPa), where the guest-framework system compresses concertedly. Not only is the duality in compressibility triggered by the availability of potential guests but the size/penetrability of the guest molecules determines the pressure at which the hard-soft transition occurs. Specifically, the observed compression behavior depends on the size of the pressure-transmitting fluid molecules, the sample particle size (i.e., the extent of the pore network), and the rate at which the pressure is increased. The unprecedented pressure-induced phenomena documented here, illustrates the exotic high-pressure behaviors possible in this versatile class of advanced functional materials with broad implications for their structure-function relationships and accordingly their practical application. PMID:18636710

  13. Carbon Nanofiber/3D Nanoporous Silicon Hybrids as High Capacity Lithium Storage Materials.

    PubMed

    Park, Hyeong-Il; Sohn, Myungbeom; Kim, Dae Sik; Park, Cheolho; Choi, Jeong-Hee; Kim, Hansu

    2016-04-21

    Carbon nanofiber (CNF)/3D nanoporous (3DNP) Si hybrid materials were prepared by chemical etching of melt-spun Si/Al-Cu-Fe alloy nanocomposites, followed by carbonization using a pitch. CNFs were successfully grown on the surface of 3DNP Si particles using residual Fe impurities after acidic etching, which acted as a catalyst for the growth of CNFs. The resulting CNF/3DNP Si hybrid materials showed an enhanced cycle performance up to 100 cycles compared to that of the pristine Si/Al-Cu-Fe alloy nanocomposite as well as that of bare 3DNP Si particles. These results indicate that CNFs and the carbon coating layer have a beneficial effect on the capacity retention characteristics of 3DNP Si particles by providing continuous electron-conduction pathways in the electrode during cycling. The approach presented here provides another way to improve the electrochemical performances of porous Si-based high capacity anode materials for lithium-ion batteries. PMID:26970098

  14. Molecularly imprinted polymer decorated nanoporous gold for highly selective and sensitive electrochemical sensors

    NASA Astrophysics Data System (ADS)

    Li, Yingchun; Liu, Yuan; Liu, Jie; Liu, Jiang; Tang, Hui; Cao, Cong; Zhao, Dongsheng; Ding, Yi

    2015-01-01

    Electrochemical nanosensors based on nanoporous gold leaf (NPGL) and molecularly imprinted polymer (MIP) are developed for pharmaceutical analysis by using metronidazole (MNZ) as a model analyte. NPGL, serving as the loading platform for MIP immobilization, possesses large accessible surface area with superb electric conductivity, while electrochemically synthesized MIP thin layer affords selectivity for specific recognition of MNZ molecules. For MNZ determination, the hybrid electrode shows two dynamic linear range of 5 × 10-11 to 1 × 10-9 mol L-1 and 1 × 10-9 to 1.4 × 10-6 mol L-1 with a remarkably low detection limit of 1.8 × 10-11 mol L-1 (S/N = 3). In addition, the sensor exhibits high binding affinity and selectivity towards MNZ with excellent reproducibility and stability. Finally, the reliability of MIP-NPGL for MNZ detection is proved in real fish tissue samples, demonstrating the potential for the proposed electrochemical sensors in monitoring drug and biological samples.

  15. Guest-dependent high-pressure phenomena in a nanoporous metal-organic framework material.

    SciTech Connect

    Chapman, K.; Halder, G. J.; Chupas, P. J.

    2008-08-13

    The nanoporous metal?organic framework material Cu{sub 3}(1,3,5-benzenetricarboxylate){sub 2}(H{sub 2}O){sub 3} {center_dot} (guest) exhibits anomalous compression under applied pressure that is associated with the hyper-filling of the pore network. This behavior involves a dramatic transition between a 'hard' regime (bulk modulus, K{sub hard} {approx} 118 GPa), where the pressure-transmitting fluid penetrates the framework cavities, and a 'soft' regime (K{sub soft} {approx} 30 GPa), where the guest-framework system compresses concertedly. Not only is the duality in compressibility triggered by the availability of potential guests but the size/penetrability of the guest molecules determines the pressure at which the hard-soft transition occurs. Specifically, the observed compression behavior depends on the size of the pressure-transmitting fluid molecules, the sample particle size (i.e., the extent of the pore network), and the rate at which the pressure is increased. The unprecedented pressure-induced phenomena documented here, illustrates the exotic high-pressure behaviors possible in this versatile class of advanced functional materials with broad implications for their structure-function relationships and accordingly their practical application.

  16. Molecularly imprinted polymer decorated nanoporous gold for highly selective and sensitive electrochemical sensors

    PubMed Central

    Li, Yingchun; Liu, Yuan; Liu, Jie; Liu, Jiang; Tang, Hui; Cao, Cong; Zhao, Dongsheng; Ding, Yi

    2015-01-01

    Electrochemical nanosensors based on nanoporous gold leaf (NPGL) and molecularly imprinted polymer (MIP) are developed for pharmaceutical analysis by using metronidazole (MNZ) as a model analyte. NPGL, serving as the loading platform for MIP immobilization, possesses large accessible surface area with superb electric conductivity, while electrochemically synthesized MIP thin layer affords selectivity for specific recognition of MNZ molecules. For MNZ determination, the hybrid electrode shows two dynamic linear range of 5 × 10−11 to 1 × 10−9 mol L−1 and 1 × 10−9 to 1.4 × 10−6 mol L−1 with a remarkably low detection limit of 1.8 × 10−11 mol L−1 (S/N = 3). In addition, the sensor exhibits high binding affinity and selectivity towards MNZ with excellent reproducibility and stability. Finally, the reliability of MIP-NPGL for MNZ detection is proved in real fish tissue samples, demonstrating the potential for the proposed electrochemical sensors in monitoring drug and biological samples. PMID:25572290

  17. Molecularly imprinted polymer decorated nanoporous gold for highly selective and sensitive electrochemical sensors.

    PubMed

    Li, Yingchun; Liu, Yuan; Liu, Jie; Liu, Jiang; Tang, Hui; Cao, Cong; Zhao, Dongsheng; Ding, Yi

    2015-01-01

    Electrochemical nanosensors based on nanoporous gold leaf (NPGL) and molecularly imprinted polymer (MIP) are developed for pharmaceutical analysis by using metronidazole (MNZ) as a model analyte. NPGL, serving as the loading platform for MIP immobilization, possesses large accessible surface area with superb electric conductivity, while electrochemically synthesized MIP thin layer affords selectivity for specific recognition of MNZ molecules. For MNZ determination, the hybrid electrode shows two dynamic linear range of 5 × 10(-11) to 1 × 10(-9) mol L(-1) and 1 × 10(-9) to 1.4 × 10(-6) mol L(-1) with a remarkably low detection limit of 1.8 × 10(-11) mol L(-1) (S/N = 3). In addition, the sensor exhibits high binding affinity and selectivity towards MNZ with excellent reproducibility and stability. Finally, the reliability of MIP-NPGL for MNZ detection is proved in real fish tissue samples, demonstrating the potential for the proposed electrochemical sensors in monitoring drug and biological samples. PMID:25572290

  18. Formation of highly adherent nano-porous alumina on Ti-based substrates: a novel bone implant coating.

    PubMed

    Briggs, E P; Walpole, A R; Wilshaw, P R; Karlsson, M; Pålsgård, E

    2004-09-01

    Thin, nano-porous, highly adherent layers of anodised aluminium formed on the surface of titanium alloys are being developed as coatings for metallic surgical implants. The layers are formed by anodisation of a 1-5 microm thick layer of aluminium which has been deposited on substrate material by electron beam evaporation. The surface ceramic layer so produced is alumina with 6-8 wt % phosphate ions and contains approximately 5 x 10(8) cm(-2) pores with a approximately 160 nm average diameter, running perpendicular to the surface. Mechanical testing showed the coatings' shear and tensile strength to be at least 20 and 10 MPa, respectively. Initial cell/material studies show promising cellular response to the nano-porous alumina. A normal osteoblastic growth pattern with cell number increasing from day 1 to 21 was shown, with slightly higher proliferative activity on the nano-porous alumina compared to the Thermanox control. Scanning electron microscopy (SEM) examination of the cells on the porous alumina membrane showed normal osteoblast morphology. Flattened cells with filopodia attaching to the pores and good coverage were also observed. In addition, the pore structure produced in these ceramic coatings is expected to be suitable for loading with bioactive material to enhance further their biological properties. PMID:15448410

  19. Graphene Oxide Derived Carbons (GODC); High-Surface Area NanoPorous Materials for Hydrogen Storage and Carbon Capture

    NASA Astrophysics Data System (ADS)

    Yildirim, Taner

    2012-02-01

    Even though there has been extensive research on gas adsorption properties of various carbon materials based on activated carbon and nanotubes, there has been little work done on the gas adsorption properties of graphite oxide (GO). In this study [1], we show that one-and-a-half-century-old graphite oxide can be easily turned into a potentially useful gas storage material. In order to create high-surface nanoporous materials from GO, we used two different approaches. In the first approach, we have successfully synthesized graphene-oxide framework materials (GOFs) by interlinking GO layers by diboronic acids. The resulting GOF materials have well defined pore size and BET surface area up to 500 m2/g with twice larger heat of adsorption of H2 and CO2 than those found in other physisorption materials such as MOF5. In the second approach, we synthesized a range of high surface area GO derived carbons (GODC) and studied their applications toward H2, CO2 and CH4 gas storage. The GODCs, with wide range of pore structure, have been prepared by chemical activation with potassium hydroxide (KOH). We obtain largely increased surface areas up to nearly 1900 m^2/g for GODC samples from 10 m^2/g for initial GO. A detailed experimental study of high pressure excess sorption isotherms on GODCs reveal an increase in both CO2 and CH4 storage capacities compared to other high surface area activated carbons. Finally, we compared the gas sorption properties of our GO-based matarials with other systems such as MOFs, ZIFs, and COFs. [4pt] [1] See http://www.ncnr.nist.gov/staff/taner for references and more information.

  20. Molecule-hugging graphene nanopores

    PubMed Central

    Garaj, Slaven; Liu, Song; Golovchenko, Jene A.; Branton, Daniel

    2013-01-01

    It has recently been recognized that solid-state nanopores in single-atomic-layer graphene membranes can be used to electronically detect and characterize single long charged polymer molecules. We have now fabricated nanopores in single-layer graphene that are closely matched to the diameter of a double-stranded DNA molecule. Ionic current signals during electrophoretically driven translocation of DNA through these nanopores were experimentally explored and theoretically modeled. Our experiments show that these nanopores have unusually high sensitivity (0.65 nA/Å) to extremely small changes in the translocating molecule’s outer diameter. Such atomically short graphene nanopores can also resolve nanoscale-spaced molecular structures along the length of a polymer, but do so with greatest sensitivity only when the pore and molecule diameters are closely matched. Modeling confirms that our most closely matched pores have an inherent resolution of ≤0.6 nm along the length of the molecule. PMID:23836648

  1. Molecule-hugging graphene nanopores.

    PubMed

    Garaj, Slaven; Liu, Song; Golovchenko, Jene A; Branton, Daniel

    2013-07-23

    It has recently been recognized that solid-state nanopores in single-atomic-layer graphene membranes can be used to electronically detect and characterize single long charged polymer molecules. We have now fabricated nanopores in single-layer graphene that are closely matched to the diameter of a double-stranded DNA molecule. Ionic current signals during electrophoretically driven translocation of DNA through these nanopores were experimentally explored and theoretically modeled. Our experiments show that these nanopores have unusually high sensitivity (0.65 nA/Å) to extremely small changes in the translocating molecule's outer diameter. Such atomically short graphene nanopores can also resolve nanoscale-spaced molecular structures along the length of a polymer, but do so with greatest sensitivity only when the pore and molecule diameters are closely matched. Modeling confirms that our most closely matched pores have an inherent resolution of ≤ 0.6 nm along the length of the molecule. PMID:23836648

  2. TiO2 nanopores with high sensitivity to ultraviolet light

    NASA Astrophysics Data System (ADS)

    Rodríguez, D. F.; Perillo, P. M.

    2015-04-01

    We investigated the UV photoconductivity and transient response of TiO2 nanopores on silicon substrate. Ti thin films were first deposited by radio-frequency (RF) magnetron sputtering and then anodized in glycerol electrolytes containing ammonium fluoride (NH4F). For the UV irradiation, the rise and decay curves of photocurrent are well fitted to a bi-exponential function. In both cases, the photocurrent was dominated by an initial fast response about 2 s. The ohmic I-V characteristic of the TiO2 nanopores under illumination could be ascribed to the decrease of the Schottky barrier height, to the accumulation of conduction electrons, resulted from the neutralization between photogenerated holes and negatively charged oxygen ions. These nanopores arrays could be useful in serving as photodetectors, chemical and biological sensors, and switching devices for nanoscale optoelectronics.

  3. Membrane Transport Processes Analyzed by a Highly Parallel Nanopore Chip System at Single Protein Resolution.

    PubMed

    Urban, Michael; Vor der Brüggen, Marc; Tampé, Robert

    2016-01-01

    Membrane protein transport on the single protein level still evades detailed analysis, if the substrate translocated is non-electrogenic. Considerable efforts have been made in this field, but techniques enabling automated high-throughput transport analysis in combination with solvent-free lipid bilayer techniques required for the analysis of membrane transporters are rare. This class of transporters however is crucial in cell homeostasis and therefore a key target in drug development and methodologies to gain new insights desperately needed. The here presented manuscript describes the establishment and handling of a novel biochip for the analysis of membrane protein mediated transport processes at single transporter resolution. The biochip is composed of microcavities enclosed by nanopores that is highly parallel in its design and can be produced in industrial grade and quantity. Protein-harboring liposomes can directly be applied to the chip surface forming self-assembled pore-spanning lipid bilayers using SSM-techniques (solid supported lipid membranes). Pore-spanning parts of the membrane are freestanding, providing the interface for substrate translocation into or out of the cavity space, which can be followed by multi-spectral fluorescent readout in real-time. The establishment of standard operating procedures (SOPs) allows the straightforward establishment of protein-harboring lipid bilayers on the chip surface of virtually every membrane protein that can be reconstituted functionally. The sole prerequisite is the establishment of a fluorescent read-out system for non-electrogenic transport substrates. High-content screening applications are accomplishable by the use of automated inverted fluorescent microscopes recording multiple chips in parallel. Large data sets can be analyzed using the freely available custom-designed analysis software. Three-color multi spectral fluorescent read-out furthermore allows for unbiased data discrimination into different

  4. Recent trends in nanopores for biotechnology

    PubMed Central

    Stoloff, Daniel H; Wanunu, Meni

    2016-01-01

    Nanopore technology employs a nanoscale hole in an insulating membrane to stochastically sense with high throughput individual biomolecules in solution. The generality of the nanopore detection principle and the ease of single-molecule detection suggest many potential applications of nanopores in biotechnology. Recent progress has been made with nanopore fabrication and sophistication, as well as with applications in DNA/protein mapping, biomolecular structure analysis, protein detection, and DNA sequencing. In addition, concepts for DNA sequencing devices have been suggested, and computational efforts have been made. The state of the nanopore field is maturing and given the right type of nanopore and operating conditions, nearly every application could revolutionize medicine in terms of speed, cost, and quality. In this review, we summarize progress in nanopores for biotechnological applications over the past 2–3 years. PMID:23266100

  5. Self-assembling synthesis of free-standing nanoporous graphene-transition-metal oxide flexible electrodes for high-performance lithium-ion batteries and supercapacitors.

    PubMed

    Huang, Xiaodan; Sun, Bing; Chen, Shuangqiang; Wang, Guoxiu

    2014-01-01

    The synthesis of nanoporous graphene by a convenient carbon nanofiber assisted self-assembly approach is reported. Porous structures with large pore volumes, high surface areas, and well-controlled pore sizes were achieved by employing spherical silica as hard templates with different diameters. Through a general wet-immersion method, transition-metal oxide (Fe3O4, Co3O4, NiO) nanocrystals can be easily loaded into nanoporous graphene papers to form three-dimensional flexible nanoarchitectures. When directly applied as electrodes in lithium-ion batteries and supercapacitors, the materials exhibited superior electrochemical performances, including an ultra-high specific capacity, an extended long cycle life, and a high rate capability. In particular, nanoporous Fe3O4-graphene composites can deliver a reversible specific capacity of 1427.5 mAh g(-1) at a high current density of 1000 mA g(-1) as anode materials in lithium-ion batteries. Furthermore, nanoporous Co3O4-graphene composites achieved a high supercapacitance of 424.2 F g(-1) . This work demonstrated that the as-developed freestanding nanoporous graphene papers could have significant potential for energy storage and conversion applications. PMID:24129981

  6. Fabrication of cobalt-nickel binary nanowires in a highly ordered alumina template via AC electrodeposition

    PubMed Central

    2013-01-01

    Cobalt-nickel (Co-Ni) binary alloy nanowires of different compositions were co-deposited in the nanopores of highly ordered anodic aluminum oxide (AAO) templates from a single sulfate bath using alternating current (AC) electrodeposition. AC electrodeposition was accomplished without modifying or removing the barrier layer. Field emission scanning electron microscope was used to study the morphology of templates and alloy nanowires. Energy-dispersive X-ray analysis confirmed the deposition of Co-Ni alloy nanowires in the AAO templates. Average diameter of the alloy nanowires was approximately 40 nm which is equal to the diameter of nanopore. X-ray diffraction analysis showed that the alloy nanowires consisted of both hexagonal close-packed and face-centered cubic phases. Magnetic measurements showed that the easy x-axis of magnetization is parallel to the nanowires with coercivity of approximately 706 Oe. AC electrodeposition is very simple, fast, and is useful for the homogenous deposition of various secondary nanostuctured materials into the nanopores of AAO. PMID:23941234

  7. A high-performance supercapacitor cell based on ZIF-8-derived nanoporous carbon using an organic electrolyte.

    PubMed

    Salunkhe, Rahul R; Young, Christine; Tang, Jing; Takei, Toshiaki; Ide, Yusuke; Kobayashi, Naoya; Yamauchi, Yusuke

    2016-04-01

    Low-cost supercapacitors have the ability to rapidly store a large amount of charge, which makes them the best alternative to batteries in portable electronics. Here, we demonstrate the fabrication of all-carbon supercapacitors using an organic electrolyte. By using ZIF-derived nanoporous carbon electrodes, we have realized a high-performance supercapacitor cell using 2 M NEt4BF4/PC as the electrolyte. Our device shows good energy storage capacity that is comparable to the other previously reported supercapacitors. PMID:26928244

  8. High-throughput Z T predictions of nanoporous bulk materials as next-generation thermoelectric materials: A material genome approach

    NASA Astrophysics Data System (ADS)

    Hao, Qing; Xu, Dongchao; Lu, Na; Zhao, Hongbo

    2016-05-01

    The advancement of computational tools for material property predictions enables a broad search of novel materials for various energy-related applications. However, challenges still exist in accurately predicting the mean free paths of electrons and phonons in a high-throughput frame for thermoelectric property predictions, which largely hinders the computation-driven material search for novel materials. In this work, this need is eliminated under the limit of reduced nanostructure size within a bulk material, in which these mean free paths are restricted by the nanostructure size. A criterion for Z T evaluation is proposed for general nanoporous bulk materials and is demonstrated with representative oxides.

  9. Hierarchical structural nanopore arrays fabricated by pre-patterning aluminum using nanosphere lithography.

    PubMed

    Wang, Xinnan; Xu, Shuping; Cong, Ming; Li, Haibo; Gu, Yuejiao; Xu, Weiqing

    2012-04-10

    A highly ordered and hierarchical structural nanopore array is fabricated via anodizing a pre-patterned aluminum foil under an optimized voltage. A pre-patterned hexagonal nanoindentation array on an aluminum substrate is prepared via the nanosphere lithography method. This pattern leads to an elaborate nanochannel structure with seven nanopores in each nanoindentation after anodization treatment. The structure achieved in our study is new, interesting, and likely to be applied in photonic devices. PMID:22315204

  10. Fabrication and Characterization of High-Crystalline Nanoporous ZnO Thin Films by Modified Thermal Evaporation System

    NASA Astrophysics Data System (ADS)

    Islam, M. S.; Hossain, M. F.; Razzak, S. M. A.; Haque, M. M.; Saha, D. K.

    2016-05-01

    The aim of this work is to fabricate high-crystalline nanoporous zinc oxide (ZnO) thin films by a modified thermal evaporation system. First, zinc thin films have been deposited on bare glass substrate by the modified thermal evaporation system with pressure of 0.05mbar, source-substrate distance of 3cm and source temperature 700∘C. Then, high-crystalline ZnO thin film is obtained by annealing at 500∘C for 2h in atmosphere. The prepared ZnO films are characterized with various deposition times of 10min and 20min. The structural property was investigated by X-ray diffractometer (XRD). The optical bandgap and absorbance/transmittance of these films are examined by ultraviolet/visible spectrophotometer. The surface morphological property has been observed by scanning electron microscope (SEM). ZnO films have showed uniform nanoporous surface with high-crystalline hexagonal wurtzite structure. The ZnO films prepared with 20min has excitation absorption-edge at 369nm, which is blueshifted with respect to the bulk absorption-edge appearing at 380nm. The gap energy of ZnO film is decreased from 3.14eV to 3.09eV with increase of the deposition time, which can enhance the excitation of ZnO films by the near visible light, and is suitable for the application of photocatalyst of waste water cleaning and polluted air purification.

  11. Nanoporous Polytetrafluoroethylene/Silica Composite Separator as a High-Performance All-Vanadium Redox Flow Battery Membrane

    SciTech Connect

    Wei, Xiaoliang; Nie, Zimin; Luo, Qingtao; Li, Bin; Chen, Baowei; Simmons, Kevin L.; Sprenkle, Vincent L.; Wang, Wei

    2013-09-02

    Driven by the motivation of searching for low-cost membrane alternatives, a novel nanoporous polytetrafluoroethylene/silica composite separator has been prepared and evaluated for its use in all-vanadium mixed-acid redox flow battery. This separator consisting of silica particles enmeshed in a polytetrafluoroethylene fibril matrix has no ion exchange capacity and is featured with unique nanoporous structures, which function as the ion transport channels in redox flow battery operation, with an average pore size of 38nm and a porosity of 48%. This separator has produced excellent electrochemical performance in the all-vanadium mixed-acid system with energy efficiency delivery comparable to Nafion membrane and superior rate capability and temperature tolerance. The separator also demonstrates an exceptional capacity retention capability over extended cycling, offering additional operational latitude towards conveniently mitigating the capacity decay that is inevitable for Nafion. Because of the inexpensive raw materials and simple preparation protocol, the separator is particularly low-cost, estimated to be at least an order of magnitude more inexpensive than Nafion. Plus the proven chemical stability due to the same backbone material as Nafion, this separator possesses a good combination of critical membrane requirements and shows great potential to promote market penetration of the all-vanadium redox flow battery by enabling significant reduction of capital and cycle costs.

  12. Surface Electronic Properties and Site-Specific Laser Desorption Processes of Highly Structured Nanoporous MgO Thin Films

    SciTech Connect

    Henyk, Matthias; Beck, Kenneth M.; Engelhard, Mark H.; Joly, Alan G.; Hess, Wayne P.; Dickinson, J T.

    2005-11-20

    The surface electronic properties of metal oxides critically depends on low-coordinated sites, such as kinks, corners and steps [1]. In order to characterize experimentally those surface states as well as their role for laser desorption processes, we prepare defect enriched surfaces by growing thin MgO films using reactive ballistic deposition [2] on crystalline dielectric substrates. With samples held at room temperature, the resulting MgO films are highly textured and consist of porous columns with column lengths ranging from tens of nanometers up to six micrometers. Measurements by x-ray photoelectron spectroscopy (XPS) are carried out in-situ for MgO films, vacuum-cleaved MgO crystals, and water vapor exposed samples. In the case of thin films, we observe O 1s spectra with a significant shoulder feature at 2.3 eV higher binding energy (HBE) than the corresponding peak at 530.0 eV representing regular lattice oxygen. We evaluate this feature in terms of non-stoichiometric oxygen and formation of an oxygen-rich layer at the topmost surface of the MgO columns. In contrast, no HBE-features are detectable from clean single crystal MgO surfaces, while the hydroxyl O 1s band peaks at 531.6 eV. Under excitation with 266-nm-laser-pulses, known to be resonant with low-coordinated surface anions [3], we observe preferential depletion of defective oxygen-states (HBE signal) and temporary restoration of ideal surface stoichiometry. Furthermore, auxiliary signals are observed on several micrometer thick films, acting like satellites to major photoelectron-peaks (O 1s, Mg 2s, and Mg 2p) but shifted by approximately 4 eV towards lower kinetic energy. These features are depleted by UV-light exposure, pointing to the occurrence of surface-charge imbalance, accompanied by photon stimulated charge-transfer reactions. These results are in line with desorption experiments of neutrals, stimulated by laser excitation at 266 nm. According to the low-coordination nature of nanoporous Mg

  13. Kinetics of nanopore fabrication during controlled breakdown of dielectric membranes in solution

    NASA Astrophysics Data System (ADS)

    Briggs, Kyle; Charron, Martin; Kwok, Harold; Le, Timothea; Chahal, Sanmeet; Bustamante, José; Waugh, Matthew; Tabard-Cossa, Vincent

    2015-02-01

    Nanopore fabrication by controlled breakdown (CBD) overcomes many of the challenges of traditional nanofabrication techniques, by reliably forming solid-state nanopores sub-2 nm in size in a low-cost and scalable way for nucleic acid analysis applications. Herein, the breakdown kinetics of thin dielectric membranes immersed in a liquid environment are investigated in order to gain deeper insights into the mechanism of solid-state nanopore formation by high electric fields. For various fabrication conditions, we demonstrate that nanopore fabrication time is Weibull-distributed, in support of the hypothesis that the fabrication mechanism is a stochastic process governed by the probability of forming a connected path across the membrane (i.e. a weakest-link problem). Additionally, we explore the roles that various ions and solvents play in breakdown kinetics, revealing that asymmetric pH conditions across the membrane can significantly affect nanopore fabrication time for a given voltage polarity. These results, characterizing the stochasticity of the nanopore fabrication process and highlighting the parameters affecting it, should assist researchers interested in exploiting the potential of CBD for nanofluidic channel fabrication, while also offering guidance towards the conceivable manufacturing of solid-state nanopore-based technologies for DNA sequencing applications.

  14. Integrated Solid/Nanoporous Copper/Oxide Hybrid Bulk Electrodes for High-performance Lithium-Ion Batteries

    PubMed Central

    Hou, Chao; Lang, Xing-You; Han, Gao-Feng; Li, Ying-Qi; Zhao, Lei; Wen, Zi; Zhu, Yong-Fu; Zhao, Ming; Li, Jian-Chen; Lian, Jian-She; Jiang, Qing

    2013-01-01

    Nanoarchitectured electroactive materials can boost rates of Li insertion/extraction, showing genuine potential to increase power output of Li-ion batteries. However, electrodes assembled with low-dimensional nanostructured transition metal oxides by conventional approach suffer from dramatic reductions in energy capacities owing to sluggish ion and electron transport kinetics. Here we report that flexible bulk electrodes, made of three-dimensional bicontinuous nanoporous Cu/MnO2 hybrid and seamlessly integrated with Cu solid current collector, substantially optimizes Li storage behavior of the constituent MnO2. As a result of the unique integration of solid/nanoporous hybrid architecture that simultaneously enhances the electron transport of MnO2, facilitates fast ion diffusion and accommodates large volume changes on Li insertion/extraction of MnO2, the supported MnO2 exhibits a stable capacity of as high as ~1100 mA h g−1 for 1000 cycles, and ultrahigh charge/discharge rates. It makes the environmentally friendly and low-cost electrode as a promising anode for high-performance Li-ion battery applications. PMID:24096928

  15. Synthesis of Nanoporous Metals, Oxides, Carbides, and Sulfides: Beyond Nanocasting.

    PubMed

    Luc, Wesley; Jiao, Feng

    2016-07-19

    Nanoporous metal-based solids are of particular interest because they combine a large quantity of surface metal sites, interconnected porous networks, and nanosized crystalline walls, thus exhibiting unique physical and chemical properties compared to other nanostructures and bulk counterparts. Among all of the synthetic approaches, nanocasting has proven to be a highly effective method for the syntheses of metal oxides with three-dimensionally ordered porous structures and crystalline walls. A typical procedure involves a thermal annealing process of a porous silica template filled with an inorganic precursor (often a metal nitrate salt), which converts the precursor into a desired phase within the silica pores. The final step is the selective removal of the silica template in either a strong base or a hydrofluoric acid solution. In the past decade, nanocasting has become a popular synthetic approach and has enabled the syntheses of a variety of nanoporous metal oxides. However, there is still a lack of synthetic methods to fabricate nanoporous materials beyond simple metal oxides. Therefore, the development of new synthetic strategies beyond nanocasting has become an important direction. This Account describes new progress in the preparation of novel nanoporous metal-based solids for heterogeneous catalysis. The discussion begins with a method called dealloying, an effective method to synthesize nanoporous metals. The starting material is a metallic alloy containing two or more elements followed by a selective chemical or electrochemical leaching process that removes one of the preferential elements, resulting in a highly porous structure. Nanoporous metals, such as Cu, Ag, and CuTi, exhibit remarkable electrocatalytic properties in carbon dioxide reduction, oxygen reduction, and hydrogen evolution reactions. In addition, the syntheses of metal oxides with hierarchical porous structures are also discussed. On the basis of the choice of hard template, nanoporous

  16. High-Order/Low-Order methods for ocean modeling

    SciTech Connect

    Newman, Christopher; Womeldorff, Geoff; Chacón, Luis; Knoll, Dana A.

    2015-06-01

    We examine a High Order/Low Order (HOLO) approach for a z-level ocean model and show that the traditional semi-implicit and split-explicit methods, as well as a recent preconditioning strategy, can easily be cast in the framework of HOLO methods. The HOLO formulation admits an implicit-explicit method that is algorithmically scalable and second-order accurate, allowing timesteps much larger than the barotropic time scale. We demonstrate how HOLO approaches, in particular the implicit-explicit method, can provide a solid route for ocean simulation to heterogeneous computing and exascale environments.

  17. Current oscillations in nanopores

    NASA Astrophysics Data System (ADS)

    Hyland, Brittany

    We develop a simple phenomenological model to describe current oscillations in single, conically shaped nanopores. The model utilizes aspects of reaction rate theory, electrochemical oscillators, and nonlinear dynamical systems. Time series of experimental data were analyzed and compared to time series simulated using the model equations. There is good qualitative agreement between experiment and simulation, though the model needs to be improved in order to obtain better quantitative agreement.

  18. Nanoporous materials for biomedical devices.

    SciTech Connect

    Adiga, S. P.; Curtiss, L. A.; Elam, J. W.; Pellin, M. J.; Shih, C.-C.; Shin, C.-M.; Lin, S.-J.; Su, Y.-Y.; Gittard, S. D.; Zhang, J.; Narayan, R. J.; National Yang-Ming Univ.; Taipei Medical Univ.; Univ. of North Carolina at Chapel Hill

    2008-01-01

    Nanoporous materials are currently being developed for use in implantable drug delivery systems, bioartificial organs, and other novel medical devices. Advances in nanofabrication have made it possible to precisely control the pore size, pore distribution, porosity, and chemical properties of pores in nanoporous materials. As a result, these materials are attractive for regulating and sensing transport at the molecular level. In this work, the use of nanoporous membranes for biomedical applications is reviewed. The basic concepts underlying membrane transport are presented in the context of design considerations for efficient size sorting. Desirable properties of nanoporous membranes used in implantable devices, including biocompatibility and antibiofouling behavior, are also discussed. In addition, the use of surface modification techniques to improve the function of nanoporous membranes is reviewed. An intriguing possibility involves functionalizing nanoporous materials with smart polymers in order to modulate biomolecular transport in response to pH, temperature, ionic concentration, or other stimuli. These efforts open up avenues to develop smart medical devices that respond to specific physiological conditions.

  19. Noncovalent functionalization of solid-state nanopores via self-assembly of amphipols

    NASA Astrophysics Data System (ADS)

    Pérez-Mitta, Gonzalo; Burr, Loïc; Tuninetti, Jimena S.; Trautmann, Christina; Toimil-Molares, María Eugenia; Azzaroni, Omar

    2016-01-01

    In recent years there has been increasing interest in the development of new methods for conferring functional features to nanopore-based fluidic devices. In this work, we describe for the first time the noncovalent integration of amphoteric-amphipathic polymers, also known as ``amphipols'', into single conical nanopores in order to obtain signal-responsive chemical nanodevices. Highly-tapered conical nanopores were fabricated by single-sided chemical etching of polycarbonate foils. After etching, the surface of the conical nanopores was chemically modified, by first metallizing the surface via gold sputtering and then by amphiphilic self-assembly of the amphipol. The net charge of adsorbed amphipols was regulated via pH changes under the environmental conditions. The pH-dependent chemical equilibrium of the weak acidic and basic monomers facilitates the regulation of the ionic transport through the nanopore by adjusting the pH of the electrolyte solution. Our results demonstrate that functional amphipathic polymers are powerful building blocks for the surface modification of nanopores and might ultimately pave the way to a new means of integrating functional and/or responsive units within nanofluidic structures.In recent years there has been increasing interest in the development of new methods for conferring functional features to nanopore-based fluidic devices. In this work, we describe for the first time the noncovalent integration of amphoteric-amphipathic polymers, also known as ``amphipols'', into single conical nanopores in order to obtain signal-responsive chemical nanodevices. Highly-tapered conical nanopores were fabricated by single-sided chemical etching of polycarbonate foils. After etching, the surface of the conical nanopores was chemically modified, by first metallizing the surface via gold sputtering and then by amphiphilic self-assembly of the amphipol. The net charge of adsorbed amphipols was regulated via pH changes under the environmental

  20. Surface chemistry driven actuation in nanoporous gold

    SciTech Connect

    Biener, J; Wittstock, A; Zepeda-Ruiz, L; Biener, M M; Zielasek, V; Kramer, D; Viswanath, R N; Weissmuller, J; Baumer, M; Hamza, A V

    2008-04-14

    Although actuation in biological systems is exclusively powered by chemical energy, this concept has not been realized in man-made actuator technologies, as these rely on generating heat or electricity first. Here, we demonstrate that surface-chemistry driven actuation can be realized in high surface area materials such as nanoporous gold. For example, we achieve reversible strain amplitudes in the order of a few tenths of a percent by alternating exposure of nanoporous Au to ozone and carbon monoxide. The effect can be explained by adsorbate-induced changes of the surface stress, and can be used to convert chemical energy directly into a mechanical response thus opening the door to surface-chemistry driven actuator and sensor technologies.

  1. In Situ Observation of Directed Nanoparticle Aggregation During the Synthesis of Ordered Nanoporous Metal in Soft Templates

    SciTech Connect

    Parent, Lucas R.; Robinson, David B.; Cappillino, Patrick J.; Hartnett, Ryan J.; Abellan Baeza, Patricia; Evans, James E.; Browning, Nigel D.; Arslan, Ilke

    2014-02-11

    The prevalent approach to developing new nanomaterials is a trial and error process of iteratively altering synthesis procedures and then characterizing the resulting nanostructures. This is fundamentally limited in that the growth processes that occur during synthesis can only be inferred from the final synthetic structure. Directly observing real-time nanomaterial growth provides unprecedented insight into the relationship between synthesis conditions and product evolution, and facilitates a mechanistic approach to nanomaterial development. Here we use in situ liquid stage scanning transmission electron microscopy to observe the growth of mesoporous palladium in a solvated block copolymer (BCP) template under various synthesis conditions, and ultimately determine a refined synthesis procedure that yields ordered pores. We find that at low organic solvent (tetrahydrofuran, THF) content, the BCP assembles into a rigid, cylindrical micelle array with a high degree of short-range order, but poor long-range order. Upon slowing the THF evaporation rate using a solvent-vapor anneal step, the long-range order is greatly improved. The electron beam induces nucleation of small particles in the aqueous phase around the micelles. The small particles then flocculate and grow into denser structures that surround the micelles, forming an ordered mesoporous structure. The microscope observations revealed that template disorder can be addressed prior to reaction, and is not invariably induced by the growth process itself, allowing us to more quickly optimize the synthetic method. This work was conducted in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy under contract DE-AC05-76RL01830. This research

  2. Nanopore reactive adsorbents for the high-efficiency removal of waste species

    DOEpatents

    Yang, Arthur Jing-Min; Zhang, Yuehua

    2005-01-04

    A nanoporous reactive adsorbent incorporates a relatively small number of relatively larger reactant, e.g., metal, enzyme, etc., particles (10) forming a discontinuous or continuous phase interspersed among and surrounded by a continuous phase of smaller adsorbent particles (12) and connected interstitial pores (14) therebetween. The reactive adsorbent can effectively remove inorganic or organic impurities in a liquid by causing the liquid to flow through the adsorbent. For example, silver ions may be adsorbed by the adsorbent particles (12) and reduced to metallic silver by reducing metal, such as ions, as the reactant particles (10). The column can be regenerated by backwashing with the liquid effluent containing, for example, acetic acid.

  3. Using High-Order Methods on Lower-Order Geometries

    NASA Technical Reports Server (NTRS)

    Casper, Jay

    1997-01-01

    The desire to obtain acoustic information from the numerical solution of a nonlinear system of equations is a demanding proposition for a computational algorithm. High-order accuracy is required for the propagation of high-frequency, low-amplitude waves. The accuracy of an algorithm can be compromised by low-order errors that naturally occur in the solution of a particular problem. Such errors arise from two sources: the presence of discontinuities in the flow field or because the geometry on which the problem is defined is not everywhere smooth to the order of the scheme. The performance of high-order accurate essentially non-oscillatory (ENO) schemes on piecewise smooth solutions is well documented. Herein, the performance of these methods on smooth solutions defined on piecewise smooth geometries is investigated. The propagation of sound in a quasi-one-dimensional nozzle is considered as a test case. Some of the issues involved in the extension to two spatial dimensions are discussed.

  4. Noise Properties of Rectifying Nanopore

    SciTech Connect

    Vlassiouk, Ivan V

    2011-01-01

    Ion currents through three types of rectifying nanoporous structures are studied and compared: conically shaped polymer nanopores, glass nanopipettes, and silicon nitride nanopores. Time signals of ion currents are analyzed by the power spectrum. We focus on the low-frequency range where the power spectrum magnitude scales with frequency, f, as 1/f. Glass nanopipettes and polymer nanopores exhibit nonequilibrium 1/f noise; thus, the normalized power spectrum depends on the voltage polarity and magnitude. In contrast, 1/f noise in rectifying silicon nitride nanopores is of equilibrium character. Various mechanisms underlying the voltage-dependent 1/f noise are explored and discussed, including intrinsic pore wall dynamics and formation of vortices and nonlinear flow patterns in the pore. Experimental data are supported by modeling of ion currents based on the coupled Poisson-Nernst-Planck and Navier-Stokes equations. We conclude that the voltage-dependent 1/f noise observed in polymer and glass asymmetric nanopores might result from high and asymmetric electric fields, inducing secondary effects in the pore, such as enhanced water dissociation.

  5. Noise Properties of Rectifying Nanopores

    SciTech Connect

    Powell, M R; Sa, N; Davenport, M; Healy, K; Vlassiouk, I; Letant, S E; Baker, L A; Siwy, Z S

    2011-02-18

    Ion currents through three types of rectifying nanoporous structures are studied and compared for the first time: conically shaped polymer nanopores, glass nanopipettes, and silicon nitride nanopores. Time signals of ion currents are analyzed by power spectrum. We focus on the low-frequency range where the power spectrum magnitude scales with frequency, f, as 1/f. Glass nanopipettes and polymer nanopores exhibit non-equilibrium 1/f noise, thus the normalized power spectrum depends on the voltage polarity and magnitude. In contrast, 1/f noise in rectifying silicon nitride nanopores is of equilibrium character. Various mechanisms underlying the voltage-dependent 1/f noise are explored and discussed, including intrinsic pore wall dynamics, and formation of vortices and non-linear flow patterns in the pore. Experimental data are supported by modeling of ion currents based on the coupled Poisson-Nernst-Planck and Navier Stokes equations. We conclude that the voltage-dependent 1/f noise observed in polymer and glass asymmetric nanopores might result from high and asymmetric electric fields inducing secondary effects in the pore such as enhanced water dissociation.

  6. Water desalination with a single-layer MoS2 nanopore.

    PubMed

    Heiranian, Mohammad; Farimani, Amir Barati; Aluru, Narayana R

    2015-01-01

    Efficient desalination of water continues to be a problem facing the society. Advances in nanotechnology have led to the development of a variety of nanoporous membranes for water purification. Here we show, by performing molecular dynamics simulations, that a nanopore in a single-layer molybdenum disulfide can effectively reject ions and allow transport of water at a high rate. More than 88% of ions are rejected by membranes having pore areas ranging from 20 to 60 Å(2). Water flux is found to be two to five orders of magnitude greater than that of other known nanoporous membranes. Pore chemistry is shown to play a significant role in modulating the water flux. Pores with only molybdenum atoms on their edges lead to higher fluxes, which are ∼ 70% greater than that of graphene nanopores. These observations are explained by permeation coefficients, energy barriers, water density and velocity distributions in the pores. PMID:26465062

  7. Water desalination with a single-layer MoS2 nanopore

    PubMed Central

    Heiranian, Mohammad; Farimani, Amir Barati; Aluru, Narayana R.

    2015-01-01

    Efficient desalination of water continues to be a problem facing the society. Advances in nanotechnology have led to the development of a variety of nanoporous membranes for water purification. Here we show, by performing molecular dynamics simulations, that a nanopore in a single-layer molybdenum disulfide can effectively reject ions and allow transport of water at a high rate. More than 88% of ions are rejected by membranes having pore areas ranging from 20 to 60 Å2. Water flux is found to be two to five orders of magnitude greater than that of other known nanoporous membranes. Pore chemistry is shown to play a significant role in modulating the water flux. Pores with only molybdenum atoms on their edges lead to higher fluxes, which are ∼70% greater than that of graphene nanopores. These observations are explained by permeation coefficients, energy barriers, water density and velocity distributions in the pores. PMID:26465062

  8. Micro-nanopores fabricated by high-energy electron beam irradiation: suitable structure for controlling pesticide loss.

    PubMed

    Xiang, Yubin; Wang, Ning; Song, Jimei; Cai, Dongqing; Wu, Zhengyan

    2013-06-01

    Pesticide sprayed onto crop leaves tends to be washed off by rainwater and discharge into the environment through leaching and runoff, resulting in severe pollution to both soil and water. Here, to control pesticide loss, we developed a loss-control pesticide (LCP) by adding modified natural nanoclay (diatomite) through high-energy electron beam (HEEB) to traditional pesticide. After HEEB treatment, the originally clogged pores in diatomite opened, resulting in plenty of micro-nanopores in diatomite, which are beneficial for the pesticide molecules to access and be adsorbed. This pesticide-diatomite complex tended to be retained by the rough surface of crop leaves, displaying a high adhesion performance onto the leaves, so that the pesticide loss reduced, sufficient pesticide for crops was supplied, and the pollution risk of the pesticide could be substantially lowered. PMID:23672373

  9. The Potential and Challenges of Nanopore Sequencing

    SciTech Connect

    Branton, Daniel; Deamer, D. W.; Marziali, A.; Bayley, H.; Benner, S. A.; Butler, Thomas; Di Ventra, Massimiliano; Garaj, S.; Hibbs, Andrew; Huang, Xiaohua; Jovanovich, Stevan B.; Krstic, Predrag S; Lindsay, Stuart; Ling, Xinsheng Sean; Mastrangelo, Carlos H.; Meller, Amit; Oliver, John S.; Pershin, Yuriy V.; Ramsey, Dr. John Michael; Riehn, Robert; Soni, Gautam; Tabard-Cossa, Vincent; Wanuunu, Meni; Wiggin, Matthew; Schloss, Jeffrey A

    2008-10-01

    A nanopore-based device provides single-molecule detection and analytical capabilities that are achieved by electrophoretically driving molecules in solution through a nan-scale pore. The nanopore provides a highly confined space within which single nucleic acid polymers can be analyzed at high throughput by one of a variety of means, and the perfect processivity that can be enforced in a narrow pore ensures that the native order of the nucleobases in a polynucleotide is reflected in the sequence of signals that is detected. Kilobase length polymers (single-stranded genomic DNA or RNA) or small molecules (e.g., nucleosides) can be identified and characterized without amplification or labeling, a unique analytical capability that makes inexpensive, rapid DNA sequencing a possibility. Further research and development to overcome current challenges to nanopore identification of each successive nucleotide in a DNA strand offers the prospect of 'third generation' instruments that will sequence a diploid mammalian genome for ~$1,000 in ~24 h.

  10. Nanoporous anodic aluminum oxide with a long-range order and tunable cell sizes by phosphoric acid anodization on pre-patterned substrates

    PubMed Central

    Surawathanawises, Krissada; Cheng, Xuanhong

    2014-01-01

    Nanoporous anodic aluminum oxide (AAO) has been explored for various applications due to its regular cell arrangement and relatively easy fabrication processes. However, conventional two-step anodization based on self-organization only allows the fabrication of a few discrete cell sizes and formation of small domains of hexagonally packed pores. Recent efforts to pre-pattern aluminum followed with anodization significantly improve the regularity and available pore geometries in AAO, while systematic study of the anodization condition, especially the impact of acid composition on pore formation guided by nanoindentation is still lacking. In this work, we pre-patterned aluminium thin films using ordered monolayers of silica beads and formed porous AAO in a single-step anodization in phosphoric acid. Controllable cell sizes ranging from 280 nm to 760 nm were obtained, matching the diameters of the silica nanobead molds used. This range of cell size is significantly greater than what has been reported for AAO formed in phosphoric acid in the literature. In addition, the relationships between the acid concentration, cell size, pore size, anodization voltage and film growth rate were studied quantitatively. The results are consistent with the theory of oxide formation through an electrochemical reaction. Not only does this study provide useful operational conditions of nanoindentation induced anodization in phosphoric acid, it also generates significant information for fundamental understanding of AAO formation. PMID:24535886

  11. Nanoporous membranes for medical and biological applications

    PubMed Central

    Adiga, Shashishekar P; Jin, Chunmin; Curtiss, Larry A; Monteiro-Riviere, Nancy A.; Narayan, Roger J

    2013-01-01

    Synthetic nanoporous materials have numerous potential biological and medical applications that involve sorting, sensing, isolating and releasing biological molecules. Nanoporous systems engineered to mimic natural filtration systems are actively being developed for use in smart implantable drug delivery systems, bioartificial organs, and other novel nano-enabled medical devices. Recent advances in nanoscience have made it possible to precisely control the morphology as well as physical and chemical properties of the pores in nanoporous materials that make them increasingly attractive for regulating and sensing transport at the molecular level. In this work, an overview of nanoporous membranes for biomedical applications is given. Various in vivo and in vitro membrane applications, including biosensing, biosorting, immunoisolation and drug delivery, are presented. Different types of nanoporous materials and their fabrication techniques are discussed with an emphasis on membranes with ordered pores. Desirable properties of membranes used in implantable devices, including biocompatibility and antibiofouling behavior, are discussed. The use of surface modification techniques to improve the function of nanoporous membranes is reviewed. Despite the extensive research carried out in fabrication, characterization, and modeling of nanoporous materials, there are still several challenges that must be overcome in order to create synthetic nanoporous systems that behave similarly to their biological counterparts. PMID:20049818

  12. Fabrication and characterization of a nanoporous NiO film with high specific energy and power via an electrochemical dealloying approach

    SciTech Connect

    Liang, Kun; Tang, Xianzhong; Wei, Bingqing; Hu, Wencheng

    2013-10-15

    Graphical abstract: The maximum values were 170 Wh kg{sup −1} and 27.5 kW kg{sup −1} for specific energy and power at the potential window of 1.1 V, respectively. As so far as we know, the values of specific energy and power were both the highest than that reported in literatures. - Highlights: • We developed a convenient approach to fabricate the three-dimensional nanoporous NiO film. • The nanoporous films contain irregular 3D interconnected nanosheets structure with open channels. • The film as supercapacitor electrode showed excellent specific capacitance values. • It is noticed that the nanoporous film exhibited high specific energy and high specific power. • The electrochemical electrode presented excellent cycling performance and low retention. - Abstract: A three-dimensional (3D) nanoporous NiO film was fabricated via a two-step process using an electrochemical route. This process included electrodeposition of the Ni/Zn alloy film and electrochemical dealloying using a direct-current power source. The scanning electron microscopy images suggest that the film has an irregular 3D interconnected nanosheet structure with open channels. The adsorption–desorption isotherms indicate that the as-prepared NiO film had a high specific surface area of 198 m g{sup −1} and a narrow pore size distribution, with two peaks at 2.7 and 5.1 nm. The specific capacitance of the sample reached 1670 F g{sup −1} at a discharge current density of 1 A g{sup −1}. In addition, the as-prepared nanoporous film exhibited high performance during a long-term cycling test. The maximum values for the specific energy and specific power at the 1.1 V potential window were 170 and 27.5 kW kg{sup −1}, respectively.

  13. Creation of nanopores on graphene planes with MgO template for preparing high-performance supercapacitor electrodes

    NASA Astrophysics Data System (ADS)

    Wang, Huanjing; Sun, Xiuxia; Liu, Zonghuai; Lei, Zhibin

    2014-05-01

    Creation of nanopores on graphene planar sheets is of great significance in promoting the kinetic diffusion of electrolyte and enhancing the utilization efficiency of graphene planar sheets. Herein, we developed a facile chemical vapor deposition strategy to prepare highly porous graphene with flake-like MgO as template and ferrocene as the carbon precursor. The graphene layers show a highly porous structure with small mesopores of 4-8 nm, large mesopores of 10-20 nm and additional macropores of 100-200 nm. These nanopores on graphene sheets provide numerous channels for fast ion transport perpendicular to the 2D basal plane, while the good powder conductivity ensures an effective electron propagation within the 2D graphene plane. As a result, a specific capacitance of 303 F g-1, an areal capacitance up to 17.3 μF cm-2 and a nearly tenfold shorter time constant were achieved when compared with those of nonporous and stacked graphene electrodes. The method demonstrated herein would open up an opportunity to prepare porous graphene for a wide applications in energy storage, biosensors, nanoelectronics and catalysis.Creation of nanopores on graphene planar sheets is of great significance in promoting the kinetic diffusion of electrolyte and enhancing the utilization efficiency of graphene planar sheets. Herein, we developed a facile chemical vapor deposition strategy to prepare highly porous graphene with flake-like MgO as template and ferrocene as the carbon precursor. The graphene layers show a highly porous structure with small mesopores of 4-8 nm, large mesopores of 10-20 nm and additional macropores of 100-200 nm. These nanopores on graphene sheets provide numerous channels for fast ion transport perpendicular to the 2D basal plane, while the good powder conductivity ensures an effective electron propagation within the 2D graphene plane. As a result, a specific capacitance of 303 F g-1, an areal capacitance up to 17.3 μF cm-2 and a nearly tenfold shorter time

  14. Highly Transparent and Flexible Triboelectric Nanogenerators with Subwavelength-Architectured Polydimethylsiloxane by a Nanoporous Anodic Aluminum Oxide Template.

    PubMed

    Dudem, Bhaskar; Ko, Yeong Hwan; Leem, Jung Woo; Lee, Soo Hyun; Yu, Jae Su

    2015-09-23

    Highly transparent and flexible triboelectric nanogenerators (TENGs) were fabricated using the subwavelength-architectured (SWA) polydimethylsiloxane (PDMS) with a nanoporous anodic aluminum oxide (AAO) template as a replica mold. The SWA PDMS could be utilized as a multifunctional film for a triboelectric layer, an antireflection coating, and a self-cleaning surface. The nanopore arrays of AAO were formed by a simple, fast, and cost-effective electrochemical oxidation process of aluminum, which is relatively impressive for fabrication of the TENG device. For electrical contacts, the SWA PDMS was laminated on the indium tin oxide (ITO)-coated polyethylene terephthalate (PET) as a bottom electrode, and the bare ITO-coated PET (i.e., ITO/PET) was used for the top electrode. Compared to the ITO/PET, the SWA PDMS on the ITO/PET improved the transmittance from 80.5 to 83% in the visible wavelength region and also had high transmittances of >85% at wavelengths of 430-455 nm. The SWA PDMS also exhibited the hydrophobic surface with a water contact angle (θCA) of ∼115°, which can be useful for self-cleaning applications. The average transmittance (Tavg) of the entire TENG device was observed to be ∼70% over a broad wavelength range. At an external pushing frequency of 0.5 Hz, for the TENG device with the ITO top electrode, open-circuit voltage (VOC) and short-circuit current (ISC) values of ∼3.8 V and ∼0.8 μA were obtained instantaneously, respectively, which were higher than those (i.e., VOC ≈ 2.2 V, and ISC ≈ 0.4 μA) of the TENG device with a gold top electrode. The effect of external pushing force and frequency on the output device performance of the TENGs was investigated, including the device robustness. A theoretical optical analysis of SWA PDMS was also performed. PMID:26301328

  15. Method to fabricate functionalized conical nanopores

    DOEpatents

    Small, Leo J.; Spoerke, Erik David; Wheeler, David R.

    2016-07-12

    A pressure-based chemical etch method is used to shape polymer nanopores into cones. By varying the pressure, the pore tip diameter can be controlled, while the pore base diameter is largely unaffected. The method provides an easy, low-cost approach for conically etching high density nanopores.

  16. Nanoporous Materials from ABAC Tetrablock Terpolymers

    NASA Astrophysics Data System (ADS)

    Jackson, Elizabeth Ashley

    This dissertation describes efforts towards the preparation of tough nanoporous membranes from ABAC tetrablock terpolymers. This architecture was strategically chosen to combine an etchable C block, PLA, with a mechanically tough ABA triblock into one ABAC terpolymer. Multiple series of poly(styrene- b-isoprene-b-styrene-b-lactide) (PS-PI-PS-PLA) tetrablock terpolymers were synthesized. Morphological behavior was characterized for terpolymers containing both a 50:50 and 30:70 PS:PI ratio with between 0 and ~20% PLA by volume. Observed bulk morphologies include hexagonally packed cylinders (HEX), core(PLA)-shell(PS) cylinders (CSC), and a PLA sphere in cylinder morphology. Mechanical properties of PS-PEEP-PS-PLA tetrablocks were also investigated. All materials exhibited mechanical properties characteristic of tough thermoplastic elastomers. Composite membranes were prepared from a thin film of PS-PI-PS-PLA terpolymer and a macroporous polyethersulfone support. Described within are the efforts related to the fabrication and filtration performance of these nanoporous PS-PI-PS composite membranes. As part of this process, solvent casting and annealing conditions were varied to investigate effects on tetrablock thin film morphology. Optimum conditions were determined to achieve PS-PI-PS-PLA films with perpendicular PLA cylinder orientation. These conditions included use of a mixed solvent system and the addition of a small amount of homopolymer PLA. Highly ordered films with vertically oriented nanopores were obtained.

  17. Fabrication and structural characterization of highly ordered titania nanotube arrays

    NASA Astrophysics Data System (ADS)

    Shi, Hongtao; Ordonez, Rosita

    Titanium (Ti) dioxide nanotubes have drawn much attention in the past decade due to the fact that titania is an extremely versatile material with a variety of technological applications. Anodizing Ti in different electrolytes has proved to be quite successful so far in creating the nanotubes, however, their degree of order is still not nearly as good as nanoporous anodic alumina. In this work, we first deposit a thin layer of aluminum (Al) onto electropolished Ti substrates, using thermal evaporation. Such an Al layer is then anodized in 0.3 M oxalic acid, forming an ordered nanoporous alumina mask on top of Ti. Afterwards, the anodization of Ti is accomplished at 20 V in solutions containing 1 M NaH2PO4 and 0.5% HF or H2SO4, which results in the creation of ordered titania nanotube arrays. The inner pore diameter of the nanotubes can be tuned from ~50 nm to ~75 nm, depending on the anodization voltage applied to Al or Ti. X-ray diffractometry shows the as-grown titania nanotubes are amorphous. Samples annealed at different temperatures in ambient atmosphere will be also reported.

  18. High-order beam optics: An overview

    SciTech Connect

    Heighway, E.A.

    1988-01-01

    Beam-transport codes have been around for as long as thirty years and high-order codes, second-order at least, for close to twenty years. Before this period of design-code development, there was considerable high-order treatment, but it was almost entirely analytical. History has a way of repeating itself, and the current excitement in the field of high-order optics is based on the application of Lie algebra and the so-called differential algebra to beam-transport codes, both of which are highly analytical in foundation. Some of the main design tools available today will be described, giving a little of their history, and will conclude by trying to convey some of the excitement in the field through a brief description of Lie and differential algebra. 30 refs., 7 figs.

  19. Impedance spectroscopy analysis of human odorant binding proteins immobilized on nanopore arrays for biochemical detection.

    PubMed

    Lu, Yanli; Zhang, Diming; Zhang, Qian; Huang, Yixuan; Luo, Senbiao; Yao, Yao; Li, Shuang; Liu, Qingjun

    2016-05-15

    Human odorant-binding proteins (hOBPs) not only can bind and transport odorants in the surrounding environment for sensing smells, but also play important roles in transmitting lots of biomolecules in different organs. Utilizing the properties of hOBPs, an electrochemical biosensor with nanopore array was developed to detect specific biomolecular ligands, such as aldehydes and fatty acids. The highly ordered nanopores of anodic aluminum oxide with diameter of 20-40 nm were fabricated with two-step oxidation. Through 2-carboxyethyl phosphonic acid, hOBPs were self-assembled on nanopores as the sensing membrane. With nanopore arrays, the impedance spectra showed quite different electron transfer processes in the frequency spectra, which could be characterized by the electron transfer resistance and electrical resistance of the porous membrane. Under stimulation of biomolecular ligands, series resistance of nanopores and hOBPs increased and showed a concentration-dependence feature, while the electron transfer resistance hardly changed. The nanopore based biosensor could sensitively detect biological ligands of benzaldehyde, docosahexaenoic acid, and lauric acid, which were closely related to or were potential biomarkers for cancers and other serious diseases. Equipped with hOBPs, the sensor exhibited promising potentials both in odorant and biomolecule detection for olfactory biosensing and in disease diagnosis and evaluation for biochemical detection. PMID:26710343

  20. Nanoporous carbon nanotubes synthesized through confined hydrogen-bonding self-assembly.

    PubMed

    Rodriguez, Adrian T; Chen, Min; Chen, Zhu; Brinker, C Jeffrey; Fan, Hongyou

    2006-07-26

    We report a simple and direct synthetic method for the preparation of nanoporous carbon nanotubes with larger pores (>10 nm) on the tube wall. The method combines the use of anodic aluminum oxide (AAO) as a template for the tube diameter and block copolymer/carbohydrates self-assembly within thin films confined inside AAO pore channels to form nanopores. It involves coating the AAO inner pore channel surface with block copolymer (polystyrene-co-poly(vinylpyridine)) and carbohydrates in dimethylformamide (DMF) solution. Drying of DMF induced microphase separation of PS-PVP and formation of ordered PS and PVP/carbohydrate domains. Within the coating, the carbohydrates stay specifically only in the pyridine domains surrounding PS domains due to the hydrogen bonding between carbohydrates and pyridine blocks. After carbonization at high temperature (>460 degrees C) in argon, PS was removed, forming the nanopores and carbohydrates, and PVP was carbonized, forming the framework of nanoporous carbon tubes within AAO channels. Removal of AAO led to the formation of individual monodisperse nanoporous carbon nanotubes with a tube wall of approximately 16 nm. The ease with which these nanoporous carbon nanotubes can be fabricated, and the ability to tune tube nanostructures and surface chemistry through the choice of block copolymers used and carbonization temperature, should facilitate investigations of their scope for practical applications. PMID:16848431

  1. Noncovalent functionalization of solid-state nanopores via self-assembly of amphipols.

    PubMed

    Pérez-Mitta, Gonzalo; Burr, Loïc; Tuninetti, Jimena S; Trautmann, Christina; Toimil-Molares, María Eugenia; Azzaroni, Omar

    2016-01-21

    In recent years there has been increasing interest in the development of new methods for conferring functional features to nanopore-based fluidic devices. In this work, we describe for the first time the noncovalent integration of amphoteric-amphipathic polymers, also known as "amphipols", into single conical nanopores in order to obtain signal-responsive chemical nanodevices. Highly-tapered conical nanopores were fabricated by single-sided chemical etching of polycarbonate foils. After etching, the surface of the conical nanopores was chemically modified, by first metallizing the surface via gold sputtering and then by amphiphilic self-assembly of the amphipol. The net charge of adsorbed amphipols was regulated via pH changes under the environmental conditions. The pH-dependent chemical equilibrium of the weak acidic and basic monomers facilitates the regulation of the ionic transport through the nanopore by adjusting the pH of the electrolyte solution. Our results demonstrate that functional amphipathic polymers are powerful building blocks for the surface modification of nanopores and might ultimately pave the way to a new means of integrating functional and/or responsive units within nanofluidic structures. PMID:26676314

  2. USE OF ATOMIC LAYER DEPOSITION OF FUNCTIONALIZATION OF NANOPOROUS BIOMATERIALS

    SciTech Connect

    Brigmon, R.; Narayan, R.; Adiga, S.; Pellin, M.; Curtiss, L.; Stafslien, S.; Chisholm, B.; Monteiro-Riviere, N.; Elam, J.

    2010-02-08

    Due to its chemical stability, uniform pore size, and high pore density, nanoporous alumina is being investigated for use in biosensing, drug delivery, hemodialysis, and other medical applications. In recent work, we have examined the use of atomic layer deposition for coating the surfaces of nanoporous alumina membranes. Zinc oxide coatings were deposited on nanoporous alumina membranes using atomic layer deposition. The zinc oxide-coated nanoporous alumina membranes demonstrated antimicrobial activity against Escherichia coli and Staphylococcus aureus bacteria. These results suggest that atomic layer deposition is an attractive technique for modifying the surfaces of nanoporous alumina membranes and other nanostructured biomaterials.

  3. Protein sensing with engineered protein nanopores*

    PubMed Central

    Mohammad, Mohammad M.; Movileanu, Liviu

    2013-01-01

    The use of nanopores is a powerful new frontier in single-molecule sciences. Nanopores have been used effectively in exploring various biophysical features of small polypeptides and proteins, such as their folding state and structure, ligand interactions, and enzymatic activity. In particular, the α-hemolysin protein pore (αHL) has been used extensively for the detection, characterization and analysis of polypeptides, because this protein nanopore is highly robust, versatile and tractable under various experimental conditions. Inspired by the mechanisms of protein translocation across the outer membrane translocases of mitochondria, we have shown the ability to use nanopore-probe techniques in controlling a single protein using engineered αHL pores. Here, we provide a detailed protocol for the preparation of αHL protein nanopores. Moreover, we demonstrate that placing attractive electrostatic traps is instrumental in tackling single-molecule stochastic sensing of folded proteins. PMID:22528256

  4. Integration of solid-state nanopores in a 0.5 μm CMOS foundry process.

    PubMed

    Uddin, A; Yemenicioglu, S; Chen, C-H; Corigliano, E; Milaninia, K; Theogarajan, L

    2013-04-19

    High-bandwidth and low-noise nanopore sensor and detection electronics are crucial in achieving single-DNA-base resolution. A potential way to accomplish this goal is to integrate solid-state nanopores within a CMOS platform, in close proximity to the biasing electrodes and custom-designed amplifier electronics. Here we report the integration of solid-state nanopore devices in a commercial complementary metal-oxide-semiconductor (CMOS) potentiostat chip implemented in On-Semiconductor's 0.5 μm technology. Nanopore membranes incorporating electrodes are fabricated by post-CMOS micromachining utilizing the n+ polysilicon/SiO2/n+ polysilicon capacitor structure available in the aforementioned process. Nanopores are created in the CMOS process by drilling in a transmission electron microscope and shrinking by atomic layer deposition. We also describe a batch fabrication method to process a large of number of electrode-embedded nanopores with sub-10 nm diameter across CMOS-compatible wafers by electron beam lithography and atomic layer deposition. The CMOS-compatibility of our fabrication process is verified by testing the electrical functionality of on-chip circuitry. We observe high current leakage with the CMOS nanopore devices due to the ionic diffusion through the SiO2 membrane. To prevent this leakage, we coat the membrane with Al2O3, which acts as an efficient diffusion barrier against alkali ions. The resulting nanopore devices also exhibit higher robustness and lower 1/f noise as compared to SiO2 and SiNx. Furthermore, we propose a theoretical model for our low-capacitance CMOS nanopore devices, showing good agreement with the experimental value. In addition, experiments and theoretical models of translocation studies are presented using 48.5 kbp λ-DNA in order to prove the functionality of on-chip pores coated with Al2O3. PMID:23519330

  5. Integration of solid-state nanopores in a 0.5 μm cmos foundry process

    PubMed Central

    Uddin, A; Yemenicioglu, S; Chen, C-H; Corigliano, E; Milaninia, K; Theogarajan, L

    2013-01-01

    High-bandwidth and low-noise nanopore sensor and detection electronics are crucial in achieving single-DNA base resolution. A potential way to accomplish this goal is to integrate solid-state nanopores within a CMOS platform, in close proximity to the biasing electrodes and custom-designed amplifier electronics. Here we report the integration of solid-state nanopore devices in a commercial complementary metal-oxide semiconductor (CMOS) potentiostat chip implemented in On-Semiconductor’s 0.5 μm technology. Nanopore membranes incorporating electrodes are fabricated by post-CMOS micromachining utilizing the N+ polysilicon/SiO2/N+ polysilicon capacitor structure available in the aforementioned process. Nanopores are created in the CMOS process by drilling in a transmission electron microscope and shrinking by atomic layer deposition. We also describe a batch fabrication method to process a large of number of electrode-embedded nanopores with sub-10 nm diameter across CMOS-compatible wafers by electron beam lithography and atomic layer deposition. The CMOS-compatibility of our fabrication process is verified by testing the electrical functionality of on-chip circuitry. We observe high current leakage with the CMOS nanopore devices due to the ionic diffusion through the SiO2 membrane. To prevent this leakage, we coat the membrane with Al2O3 which acts as an efficient diffusion barrier against alkali ions. The resulting nanopore devices also exhibit higher robustness and lower 1/f noise as compared to SiO2 and SiNx. Furthermore, we propose a theoretical model for our low-capacitance CMOS nanopore devices, showing good agreement with the experimental value. In addition, experiments and theoretical models of translocation studies are presented using 48.5 kbp λ-DNA in order to prove the functionality of on-chip pores coated with Al2O3. PMID:23519330

  6. Integration of solid-state nanopores in a 0.5 μm CMOS foundry process

    NASA Astrophysics Data System (ADS)

    Uddin, A.; Yemenicioglu, S.; Chen, C.-H.; Corigliano, E.; Milaninia, K.; Theogarajan, L.

    2013-04-01

    High-bandwidth and low-noise nanopore sensor and detection electronics are crucial in achieving single-DNA-base resolution. A potential way to accomplish this goal is to integrate solid-state nanopores within a CMOS platform, in close proximity to the biasing electrodes and custom-designed amplifier electronics. Here we report the integration of solid-state nanopore devices in a commercial complementary metal-oxide-semiconductor (CMOS) potentiostat chip implemented in On-Semiconductor’s 0.5 μm technology. Nanopore membranes incorporating electrodes are fabricated by post-CMOS micromachining utilizing the n+ polysilicon/SiO2/n+ polysilicon capacitor structure available in the aforementioned process. Nanopores are created in the CMOS process by drilling in a transmission electron microscope and shrinking by atomic layer deposition. We also describe a batch fabrication method to process a large of number of electrode-embedded nanopores with sub-10 nm diameter across CMOS-compatible wafers by electron beam lithography and atomic layer deposition. The CMOS-compatibility of our fabrication process is verified by testing the electrical functionality of on-chip circuitry. We observe high current leakage with the CMOS nanopore devices due to the ionic diffusion through the SiO2 membrane. To prevent this leakage, we coat the membrane with Al2O3, which acts as an efficient diffusion barrier against alkali ions. The resulting nanopore devices also exhibit higher robustness and lower 1/f noise as compared to SiO2 and SiNx. Furthermore, we propose a theoretical model for our low-capacitance CMOS nanopore devices, showing good agreement with the experimental value. In addition, experiments and theoretical models of translocation studies are presented using 48.5 kbp λ-DNA in order to prove the functionality of on-chip pores coated with Al2O3.

  7. STEM-EELS analysis reveals stable high-density He in nanopores of amorphous silicon coatings deposited by magnetron sputtering.

    PubMed

    Schierholz, Roland; Lacroix, Bertrand; Godinho, Vanda; Caballero-Hernández, Jaime; Duchamp, Martial; Fernández, Asunción

    2015-02-20

    A broad interest has been showed recently on the study of nanostructuring of thin films and surfaces obtained by low-energy He plasma treatments and He incorporation via magnetron sputtering. In this paper spatially resolved electron energy-loss spectroscopy in a scanning transmission electron microscope is used to locate and characterize the He state in nanoporous amorphous silicon coatings deposited by magnetron sputtering. A dedicated MATLAB program was developed to quantify the helium density inside individual pores based on the energy position shift or peak intensity of the He K-edge. A good agreement was observed between the high density (∼35-60 at nm(-3)) and pressure (0.3-1.0 GPa) values obtained in nanoscale analysis and the values derived from macroscopic measurements (the composition obtained by proton backscattering spectroscopy coupled to the macroscopic porosity estimated from ellipsometry). This work provides new insights into these novel porous coatings, providing evidence of high-density He located inside the pores and validating the methodology applied here to characterize the formation of pores filled with the helium process gas during deposition. A similar stabilization of condensed He bubbles has been previously demonstrated by high-energy He ion implantation in metals and is newly demonstrated here using a widely employed methodology, magnetron sputtering, for achieving coatings with a high density of homogeneously distributed pores and He storage capacities as high as 21 at%. PMID:25627862

  8. Highly sensitive detection of hydrogen peroxide based on nanoporous Fe₂O₃/CoO composites.

    PubMed

    Wang, Jinping; Gao, Hua; Sun, Fenglei; Hao, Qin; Xu, Caixia

    2013-04-15

    Nanoporous (NP) Fe₂O₃/CoO composites were straightforwardly fabricated by a simple dealloying strategy. Electron microscopy characterization demonstrates that selectively etching FeCoAl ternary alloy in a low concentration of NaOH solution generates a nanoparticle structure with a typical diameter around 80 nm. Interestingly, these nanoparticles consist of open three-dimensional bicontinuous nanosponge structure with uniform pore and ligament distribution around 10 nm. The resulted sample is confirmed to be a mixture of Fe₂O₃ and CoO species based on X-ray photoelectron spectroscopy and X-Ray diffraction analysis. Without any activation pretreatment, NP-Fe₂O₃/CoO composites exhibit excellent electro-oxidation activity toward H₂O₂, such as an excellent sensing performance in a wide linear sensing region from 0.05 to 4.85 mM H₂O₂, fast amperometric response (<2s), and a lower detection limit to 0.1 μM. Along with these attractive features, the as-made composites also behave as a good anti-interference towards glucose, uric acid, dopamine, and ascorbic acid during H₂O₂ detection. Furthermore, the H₂O₂ biosensor based on NP-Fe₂O₃/CoO composites also exhibits excellent long-term stability and reproducibility. PMID:23261688

  9. High-Order Energies for Stereo Segmentation.

    PubMed

    Peng, Jianteng; Shen, Jianbing; Li, Xuelong

    2016-07-01

    In this paper, we propose a novel segmentation approach for stereo images using the high-order energy optimization, which utilizes the disparity maps and statistical information of stereo images to enrich the high-order potential functions. To the best of our knowledge, our approach is the first one to formulate the problem of stereo segmentation as a high-order energy optimization problem, which simultaneously segments the foreground objects in left and right images using the proposed high-order potential function. A new method for designing the penalty function in our high-order term is proposed by the corresponding pixels and their neighboring pixels between left and right images. The relationships of stereo correspondence by disparity maps are further employed to enhance the connections between the left and right stereo images. Experimental results demonstrate that the proposed approach can effectively improve the performance of two kinds of stereo segmentation, including the automatic saliency-aware stereocut and the interactive stereo segmentation with user scribbles. PMID:26208377

  10. A FIB induced boiling mechanism for rapid nanopore formation.

    PubMed

    Das, K; Freund, J B; Johnson, H T

    2014-01-24

    Focused ion beam (FIB) technology is widely used to fabricate nanopores in solid-state membranes. These nanopores have desirable thermomechanical properties for applications such as high-throughput DNA sequencing. Using large scale molecular dynamics simulations of the FIB nanopore formation process, we show that there is a threshold ion delivery rate above which the mechanism underlying nanopore formation changes. At low rates nanopore formation is slow, with the rate proportional to the ion flux and therefore limited by the sputter rate of the target material. However, at higher fluxes nanopores form via a thermally dominated process, consistent with an explosive boiling mechanism. In this case, mass is rapidly rearranged via bubble growth and coalescence, much more quickly than would occur during sputtering. This mechanism has the potential to greatly speed up nanopore formation. PMID:24356374

  11. A FIB induced boiling mechanism for rapid nanopore formation

    PubMed Central

    Das, K; Freund, J B; Johnson, H T

    2015-01-01

    Focused ion beam (FIB) technology is widely used to fabricate nanopores in solid-state membranes. These nanopores have desirable thermomechanical properties for applications such as high-throughput DNA sequencing. Using large scale molecular dynamics simulations of the FIB nanopore formation process, we show that there is a threshold ion delivery rate above which the mechanism underlying nanopore formation changes. At low rates nanopore formation is slow, with the rate proportional to the ion flux and therefore limited by the sputter rate of the target material. However, at higher fluxes nanopores form via a thermally dominated process, consistent with an explosive boiling mechanism. In this case, mass is rapidly rearranged via bubble growth and coalescence, much more quickly than would occur during sputtering. This mechanism has the potential to greatly speed up nanopore formation. PMID:24356374

  12. Notable improvement of capacitive performance of highly nanoporous carbon materials simply by a redox additive electrolyte of p-nitroaniline

    NASA Astrophysics Data System (ADS)

    Zhu, Yan Qi; Zhang, Lei; Chen, Xiang Ying; Xiao, Zheng Hui; Zhang, Zhong Jie

    2015-12-01

    Highly nanoporous carbon materials have been produced by a synchronous carbonization/graphitization process, using magnesium citrate serves as the carbon source and nickel nitrate as graphitization catalyst. The carbonization temperature plays a crucial role in determining the porosity and graphitization. The lower temperature favors for the formation of larger porosity, whilst higher temperature for better crystallinity. Resultantly, a high BET surface area of 2587.13 m2 g-1 and large total pore volume of 4.64 cm3 g-1 appear, the case of C-800 sample, thereby resulting in a large specific capacitance of 305.3 F g-1 at 1 A g-1 from the contribution of electric double layer capacitances. More importantly, we demonstrate a novel redox active additive of p-nitroaniline (PNA) into the 6 mol L-1 KOH electrolyte to largely improve the capacitance by the quick self-discharge redox reaction of H+/e-. The C-800-2 sample with the PNA concentration of 2 mmol delivers largely improved capacitance of 502.1 F g-1 at 1 A g-1, which is almost 1.65 fold increase. Apparently, the present PNA is commercially available, and highly effective for elevating the specific capacitance and might be implemented for the wide supercapacitor application.

  13. HODIF:High-Order Discretizations, Interpolations and

    SciTech Connect

    Kennedy, Christopher A.; Carpenter, Mark H.; Ray, Jaideen

    2006-06-20

    This software, a library, contains FORTRAN77 subroutines to calculate first and second derivatives up to 8th order, interpolations (1D and 2D) up to 10th order and filters up to 14th order. Only even orders are addressed and finite-difference stencils are implemented on a vertex-centered mesh. The primary aim of this library is to be used in block-structured adaptive mesh simulations where high order is desired. The interpolants in this library are essentially designed to do prolongations and restrictions between levels of rfinement - however, they assume that the refinement ratio is 2. The filters are provided to remove high wavenumber content from solutions in case Runge phenomenon occurs - a common occurrence in case of marginal resolution of the solution. Details of the derivation and use are to be found in "Using high-order methods on adaptively refined block-structured meshes - discretizations, interpolations and filters", by J. Ray, C.A. Kennedy, S. Lefantzi and H.N. Najm, Sandia Technical Report, SAND2005-7981. The software comes with a User's Guide and examples how to use it.

  14. HODIF:High-Order Discretizations, Interpolations and

    Energy Science and Technology Software Center (ESTSC)

    2006-06-20

    This software, a library, contains FORTRAN77 subroutines to calculate first and second derivatives up to 8th order, interpolations (1D and 2D) up to 10th order and filters up to 14th order. Only even orders are addressed and finite-difference stencils are implemented on a vertex-centered mesh. The primary aim of this library is to be used in block-structured adaptive mesh simulations where high order is desired. The interpolants in this library are essentially designed to domore » prolongations and restrictions between levels of rfinement - however, they assume that the refinement ratio is 2. The filters are provided to remove high wavenumber content from solutions in case Runge phenomenon occurs - a common occurrence in case of marginal resolution of the solution. Details of the derivation and use are to be found in "Using high-order methods on adaptively refined block-structured meshes - discretizations, interpolations and filters", by J. Ray, C.A. Kennedy, S. Lefantzi and H.N. Najm, Sandia Technical Report, SAND2005-7981. The software comes with a User's Guide and examples how to use it.« less

  15. Preparation of Nano-Porous Activated Carbon Aerogel Using a Single-Step Activation Method for Use as High-Power EDLC Electrode in Organic Electrolyte.

    PubMed

    Kwon, Soon Hyung; Kim, Bum-Soo; Kim, Sang-Gil; Lee, Byung-Jun; Kim, Myung-Soo; Jung, Ji Chul

    2016-05-01

    Carbon aerogel was chemically activated with KOH using two different activation methods (conventional activation method and single-step activation method) to yield the nano-porous activated carbon aerogel. Both nano-porous activated carbon aerogels exhibited a better capacitive behavior than carbon aerogel in organic electrolyte. However, a drastic decrease in the specific capacitance with increasing current density was observed in the ACA_C (activated carbon aerogel prepared by a conventional activation method), which is a general tendency of carbon electrode for EDLC in organic electrolyte. Interestingly, the specific capacitance of ACA_S electrode (activated carbon aerogel prepared by a single-step activation method) decreased slowly with increasing current density and its CV curve maintained a rectangular shape well even at a high scan rate of 500 mV/s. The enhanced electrochemical performance of ACA_S at a high current density was attributed to its low ionic resistance caused by the well-developed pore structure with appropriate pore size for easy moving of organic electrolyte ion. Therefore, it can be concluded that single-step activation method could be one of the efficient methods for preparation of nano-porous activated carbon aerogel electrode for high-power EDLC in organic electrolyte. PMID:27483797

  16. Ultra-high-density 3D DNA arrays within nanoporous biocompatible membranes for single-molecule-level detection and purification of circulating nucleic acids.

    PubMed

    Aramesh, M; Shimoni, O; Fox, K; Karle, T J; Lohrmann, A; Ostrikov, K; Prawer, S; Cervenka, J

    2015-04-14

    Extracellular nucleic acids freely circulating in blood and other physiologic fluids are important biomarkers for non-invasive diagnostics and early detection of cancer and other diseases, yet difficult to detect because they exist in very low concentrations and large volumes. Here we demonstrate a new broad-range sensor platform for ultrasensitive and selective detection of circulating DNA down to the single-molecule level. The biosensor is based on a chemically functionalized nanoporous diamond-like carbon (DLC) coated alumina membrane. The few nanometer-thick, yet perfect and continuous DLC-coating confers the chemical stability and biocompatibility of the sensor, allowing its direct application in biological conditions. The selective detection is based on complementary hybridization of a fluorescently-tagged circulating cancer oncomarker (a 21-mer nucleic acid) with covalently immobilized DNA on the surface of the membrane. The captured DNAs are detected in the nanoporous structure of the sensor using confocal scanning laser microscopy. The flow-through membrane sensor demonstrates broad-range sensitivity, spanning from 10(15) molecules per cm(2) down to single molecules, which is several orders of magnitude improvement compared to the flat DNA microarrays. Our study suggests that these flow-through type nanoporous sensors represent a new powerful platform for large volume sampling and ultrasensitive detection of different chemical biomarkers. PMID:25744416

  17. High pressure induced phase transition and superdiffusion in anomalous fluid confined in flexible nanopores

    SciTech Connect

    Bordin, José Rafael; Krott, Leandro B. Barbosa, Marcia C.

    2014-10-14

    The behavior of a confined spherical symmetric anomalous fluid under high external pressure was studied with Molecular Dynamics simulations. The fluid is modeled by a core-softened potential with two characteristic length scales, which in bulk reproduces the dynamical, thermodynamical, and structural anomalous behavior observed for water and other anomalous fluids. Our findings show that this system has a superdiffusion regime for sufficient high pressure and low temperature. As well, our results indicate that this superdiffusive regime is strongly related with the fluid structural properties and the superdiffusion to diffusion transition is a first order phase transition. We show how the simulation time and statistics are important to obtain the correct dynamical behavior of the confined fluid. Our results are discussed on the basis of the two length scales.

  18. Ordering Transformations in High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Singh, Prashant; Johnson, Duane D.

    The high-temperature disordered phase of multi-component alloys, including high-entropy alloys (HEA), generally must experience segregation or else passes through partially-ordered phases to reach the low-temperature, fully-ordered phase. Our first-principles KKR-CPA-based atomic short-range ordering (SRO) calculations (analyzed as concentration-waves) reveal the competing partially and fully ordered phases in HEA, and these phases can be then directly assessed from KKR-CPA results in larger unit cells [Phys. Rev. B 91, 224204 (2015)]. For AlxCrFeNiTi0.25, Liu et al. [J Alloys Compd 619, 610 (2015)] experimentally find FCC+BCC coexistence that changes to BCC with increasing Al (x from 0-to-1), which then exhibits a partially-ordered B2 at low temperatures. CALPHAD (Calculation of Phase Diagrams) predicts a region with L21+B2 coexistence. From KKR-CPA calculations, we find crossover versus Al from FCC+BCC coexistence to BCC, as observed, and regions for partially-order B2+L21 coexistence, as suggest by CALPHAD. Our combined first-principles KKR-CPA method provides a powerful approach in predicting SRO and completing long-range order in HEA and other complex alloys. Supported by the U.S. DOE, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division. Work was performed at Ames Laboratory, which is operated by Iowa State University for the U.S. DOE under Contract #DE-AC02-07CH11358.

  19. Highly active nanoporous Pt-based alloy as anode and cathode catalyst for direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Chen, Xiaoting; Jiang, Yingying; Sun, Junzhe; Jin, Chuanhong; Zhang, Zhonghua

    2014-12-01

    In this paper, we explore nanoporous PtPdAlCu (np-PtPdAlCu) quaternary alloy through ball-milling with the subsequent two-step dealloying strategy. The microstructure and catalytic performance of the np-PtPdAlCu catalyst have been characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical measurements. The np-PtPdAlCu catalyst exhibits an open bi-continuous interpenetrating ligament/channel structure with a length scale of 2.3 ± 0.5 nm. The np-PtPdAlCu catalyst shows 2 and 3.5 times enhancement in the mass activity and area specific activity towards methanol oxidation at anode respectively, compared to the Johnson Matthey (JM) Pt/C (40 wt.%) catalyst. Moreover, the CO stripping peak of np-PtPdAlCu is 0.49 V (vs. SCE), indicating a 180 mV negative shift in comparison with the Pt/C catalyst (0.67 V vs. SCE). In addition, the np-PtPdAlCu catalyst also shows an enhanced oxygen reduction reaction (ORR) activity at cathode compared to Pt/C. The present study provides a facile and effective route to design high-performance catalysts for direct methanol fuel cells (DMFCs).

  20. Preparation and characterization of a novel highly hydrophilic and antifouling polysulfone/nanoporous TiO2 nanocomposite membrane.

    PubMed

    Bidsorkhi, H Cheraghi; Riazi, H; Emadzadeh, D; Ghanbari, M; Matsuura, T; Lau, W J; Ismail, A F

    2016-10-14

    In this research, novel ultrafiltration nanocomposite membranes were prepared by incorporating self-synthesized nanoporous titanium dioxide (NTiO2) nanoparticles into polysulfone. The surface of the nanoparticle was treated with a silane-based modifier to improve its distribution in the host polymer. Atomic-force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller, transmission electron microscopy, energy-dispersive x-ray spectroscopy, porosity and contact angle tests were conducted to characterize the properties of the particles as well as the fabricated nanocomposite membranes. The effects of the nanoparticle incorporation were evaluated by conducting ultrafiltration experiments. It was reported that the membrane pure water flux was increased with increasing NTiO2 loading owing to the high porosity of the nanoparticles embedded and/or formation of enlarged pores upon addition of them. The antifouling capacity of the membranes was also tested by ultrafiltration of bovine serum albumin fouling solution. It was found that both water flux and antifouling capacity tended to reach desired level if the NTiO2 added was at optimized loading. PMID:27607307

  1. Three-dimensional nanoporous gold-cobalt oxide electrode for high-performance electroreduction of hydrogen peroxide in alkaline medium

    NASA Astrophysics Data System (ADS)

    Li, Zhihao; He, Yanghua; Ke, Xi; Gan, Lin; Zhao, Jie; Cui, Guofeng; Wu, Gang

    2015-10-01

    Using a simple hydrothermal method combined with a post-annealing treatment, cobalt oxide (Co3O4) nanosheet arrays are grown on three-dimensional (3D) nanoporous gold (NPG) film supported on Ni foam substrates, in which NPG is fabricated by chemically dealloying electrodeposited Au-Sn alloy films. The morphology and structure of the Co3O4@NPG/Ni foam hybrids are characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The electrochemical activity of the Co3O4@NPG/Ni foam electrode toward hydrogen peroxide electroreduction in alkaline medium is studied by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and chronoamperometry (CA). The results demonstrate that the Co3O4@NPG/Ni foam electrode possesses exceptionally high catalytic activity and excellent stability for the peroxide electroreduction, resulting mainly from the unique electrode architecture. The combined 3D hierarchical porous structures of NPG/Ni foam with the open and porous structures of Co3O4 nanosheet arrays facilitate the mass transport and charge transfer. Therefore, the metal oxides supported on 3D hierarchical porous NPG/Ni foam framework may hold great promise to be effective electrodes for electrocatalytic reduction of peroxide and other electrochemical reactions.

  2. Facile chemical synthesis of nanoporous layered δ-MnO2 thin film for high-performance flexible electrochemical capacitors

    NASA Astrophysics Data System (ADS)

    Hu, Yu; Wang, Jun; Jiang, Xionghua; Zheng, Yanfeng; Chen, Zhenxing

    2013-04-01

    Layered δ-MnO2 thin films with a three-dimensional nanostructure are successfully fabricated on stainless steel foil substrates for flexible electrochemical capacitors by a facile and effective chemical bath deposition technology from ethanol and potassium permanganate solution at 15 °C. The as-prepared thin films display nanoporous morphology and a water contact angle of 20°. Energy-dispersive X-ray spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy analyses reveal that the thin films are composed of δ-MnO2. Electrochemical data demonstrate that the δ-MnO2 thin film electrodes can deliver a high special capacitance of 447 F/g at 2 mV/s, and provide a good capacitance retention ratio of 87% after 1000 continuous cycles at 10 mV/s in 0.5 M Na2SO4. Compressive and tensile bending tests show that the as-prepared electrodes can steadily work over a wide range of applied curvatures between -2.5 cm-1 (tension) and 2.5 cm-1 (compression). Only a small decrease in special capacitance (0.9% at a curvature of 2.5 cm-1 under compressive strain, or 1.2% at a curvature of -2.5 cm-1 under tensile strain) is observed even after bending for 200 cycles, indicating the excellent mechanical flexibility and electrochemical stability of the δ-MnO2 thin film electrodes.

  3. Room-temperature synthesis of nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) with highly enhanced photocatalytic activity and stability

    NASA Astrophysics Data System (ADS)

    Pawar, Rajendra C.; Kang, Suhee; Park, Jung Hyun; Kim, Jong-Ho; Ahn, Sunghoon; Lee, Caroline S.

    2016-08-01

    A one-dimensional (1D) nanostructure having a porous network is an exceptional photocatalytic material to generate hydrogen (H2) and decontaminate wastewater using solar energy. In this report, we synthesized nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) via a facile and template-free chemical approach at room temperature. The use of concentrated acids induced etching and lift-off because of strong oxidation and protonation. Compared with the bulk g-C3N4, the porous 1D microrod structure showed five times higher photocatalytic degradation performance toward methylene blue dye (MB) under visible light irradiation. The photocatalytic H2 evolution of the 1D nanostructure (34 μmol g‑1) was almost 26 times higher than that of the bulk g-C3N4 structure (1.26 μmol g‑1). Additionally, the photocurrent stability of this nanoporous 1D morphology over 24 h indicated remarkable photocorrosion resistance. The improved photocatalytic activities were attributed to prolonged carrier lifetime because of its quantum confinement effect, effective separation and transport of charge carriers, and increased number of active sites from interconnected nanopores throughout the microrods. The present 1D nanostructure would be highly suited for photocatalytic water purification as well as water splitting devices. Finally, this facile and room temperature strategy to fabricate the nanostructures is very cost-effective.

  4. Room-temperature synthesis of nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) with highly enhanced photocatalytic activity and stability.

    PubMed

    Pawar, Rajendra C; Kang, Suhee; Park, Jung Hyun; Kim, Jong-Ho; Ahn, Sunghoon; Lee, Caroline S

    2016-01-01

    A one-dimensional (1D) nanostructure having a porous network is an exceptional photocatalytic material to generate hydrogen (H2) and decontaminate wastewater using solar energy. In this report, we synthesized nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) via a facile and template-free chemical approach at room temperature. The use of concentrated acids induced etching and lift-off because of strong oxidation and protonation. Compared with the bulk g-C3N4, the porous 1D microrod structure showed five times higher photocatalytic degradation performance toward methylene blue dye (MB) under visible light irradiation. The photocatalytic H2 evolution of the 1D nanostructure (34 μmol g(-1)) was almost 26 times higher than that of the bulk g-C3N4 structure (1.26 μmol g(-1)). Additionally, the photocurrent stability of this nanoporous 1D morphology over 24 h indicated remarkable photocorrosion resistance. The improved photocatalytic activities were attributed to prolonged carrier lifetime because of its quantum confinement effect, effective separation and transport of charge carriers, and increased number of active sites from interconnected nanopores throughout the microrods. The present 1D nanostructure would be highly suited for photocatalytic water purification as well as water splitting devices. Finally, this facile and room temperature strategy to fabricate the nanostructures is very cost-effective. PMID:27498979

  5. Room-temperature synthesis of nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) with highly enhanced photocatalytic activity and stability

    PubMed Central

    Pawar, Rajendra C.; Kang, Suhee; Park, Jung Hyun; Kim, Jong-ho; Ahn, Sunghoon; Lee, Caroline S.

    2016-01-01

    A one-dimensional (1D) nanostructure having a porous network is an exceptional photocatalytic material to generate hydrogen (H2) and decontaminate wastewater using solar energy. In this report, we synthesized nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) via a facile and template-free chemical approach at room temperature. The use of concentrated acids induced etching and lift-off because of strong oxidation and protonation. Compared with the bulk g-C3N4, the porous 1D microrod structure showed five times higher photocatalytic degradation performance toward methylene blue dye (MB) under visible light irradiation. The photocatalytic H2 evolution of the 1D nanostructure (34 μmol g−1) was almost 26 times higher than that of the bulk g-C3N4 structure (1.26 μmol g−1). Additionally, the photocurrent stability of this nanoporous 1D morphology over 24 h indicated remarkable photocorrosion resistance. The improved photocatalytic activities were attributed to prolonged carrier lifetime because of its quantum confinement effect, effective separation and transport of charge carriers, and increased number of active sites from interconnected nanopores throughout the microrods. The present 1D nanostructure would be highly suited for photocatalytic water purification as well as water splitting devices. Finally, this facile and room temperature strategy to fabricate the nanostructures is very cost-effective. PMID:27498979

  6. High-order pulse front tilt caused by high-order angular dispersion.

    PubMed

    Nabekawa, Yasuo; Midorikawa, Katsumi

    2003-12-15

    We have found general expressions relating the high-order pulse front tilt and the high-order angular dispersion in an ultrashort pulse, for the first time to our knowledge. The general formulae based on Fermat's principle are applicable for any ultrashort pulse with angular dispersion in the limit of geometrical optics. By virtue of these formulae, we can calculate the high-order pulse front tilt in the sub-20-fs UV pulse generated in a novel scheme of sum-frequency mixing in a nonlinear crystal accompanied by angular dispersion. It is also demonstrated how the high-order angular dispersion can be eliminated in the calculation. PMID:19471467

  7. A Highly-Durable CO-Tolerant Poly(vinylphosphonic acid)-Coated Electrocatalyst Supported on a Nanoporous Carbon.

    PubMed

    Yang, Zehui; Moriguchi, Isamu; Nakashima, Naotoshi

    2016-04-13

    For direct methanol fuel cells (DMFCs) to be commercialized, the durability of the anodic electrocatalyst needs to be highly considered, especially under high temperature and methanol concentration conditions. Low durability caused by carbon corrosion as well as carbon monoxide (CO) poisoning of the platinum nanoparticles (Pt-NP) leads to a decrease in active Pt-NPs and increases inactive Pt-NPs covered by CO species. In this study, we deposited Pt-NPs on poly[2,2'-(2,6-pyridine)-5,5'-bibenzimidazole] (PyPBI)-wrapped nanoporous carbon (NanoPC) and coated the as-synthesized electrocatalyst with poly(vinylphosphonic acid) (PVPA). The durability of the as-synthesized NanoPC/PyPBI/Pt/PVPA was tested in 0.1 M HClO4 electrolyte at 60 °C by cycling the potential from 1.0 to 1.5 V relative to RHE, and the results indicated that NanoPC/PyPBI/Pt/PVPA showed ∼5 times better durability relative to that of the commercial CB/Pt. The methanol oxidation reaction (MOR) of the electrocatalyst was tested before and after the potential cycling in the presence of 4 or 8 M methanol at 60 °C and found that the CO tolerance of the electrocatalyst was ∼3 times higher than that of the commercial CB/Pt. Such a higher CO tolerance is due to the coating of the PVPA, which was proven by an EDX mapping measurement. The NanoPC/PyPBI/Pt/PVPA showed a high durability and CO tolerance under high temperature and high methanol concentration conditions, indicating that the electrocatalyst could be used in real fuel applications. PMID:26807598

  8. High order generalized permutational fractional Fourier transforms

    NASA Astrophysics Data System (ADS)

    Ran, Qi-Wen; Yuan, Lin; Tan, Li-Ying; Ma, Jing; Wang, Qi

    2004-02-01

    We generalize the definition of the fractional Fourier transform (FRFT) by extending the new definition proposed by Shih. The generalized FRFT, called the high order generalized permutational fractional Fourier transform (HGPFRFT), is a generalized permutational transform. It is shown to have arbitrary natural number M periodic eigenvalues not only with respect to the order of Hermite-Gaussian functions but also to the order of the transform. This HGPFRFT will be reduced to the original FRFT proposed by Namias and Liu's generalized FRFT and Shih's FRFT at the three limits with M = +infty, M = 4k (k is a natural number) and M = 4, respectively. Therefore the HGPFRFT introduces a comprehensive approach to Shih's FRFT and the original definition. Some important properties of HGPFRFT are discussed. Lastly the results of computer simulations and symbolic representations of the transform are provided.

  9. High-Order Energy Stable WENO Schemes

    NASA Technical Reports Server (NTRS)

    Yamaleev, Nail K.; Carpenter, Mark H.

    2008-01-01

    A new third-order Energy Stable Weighted Essentially NonOscillatory (ESWENO) finite difference scheme for scalar and vector linear hyperbolic equations with piecewise continuous initial conditions is developed. The new scheme is proven to be stable in the energy norm for both continuous and discontinuous solutions. In contrast to the existing high-resolution shock-capturing schemes, no assumption that the reconstruction should be total variation bounded (TVB) is explicitly required to prove stability of the new scheme. A rigorous truncation error analysis is presented showing that the accuracy of the 3rd-order ESWENO scheme is drastically improved if the tuning parameters of the weight functions satisfy certain criteria. Numerical results show that the new ESWENO scheme is stable and significantly outperforms the conventional third-order WENO finite difference scheme of Jiang and Shu in terms of accuracy, while providing essentially nonoscillatory solutions near strong discontinuities.

  10. Ultra-high-density 3D DNA arrays within nanoporous biocompatible membranes for single-molecule-level detection and purification of circulating nucleic acids

    NASA Astrophysics Data System (ADS)

    Aramesh, M.; Shimoni, O.; Fox, K.; Karle, T. J.; Lohrmann, A.; Ostrikov, K.; Prawer, S.; Cervenka, J.

    2015-03-01

    Extracellular nucleic acids freely circulating in blood and other physiologic fluids are important biomarkers for non-invasive diagnostics and early detection of cancer and other diseases, yet difficult to detect because they exist in very low concentrations and large volumes. Here we demonstrate a new broad-range sensor platform for ultrasensitive and selective detection of circulating DNA down to the single-molecule level. The biosensor is based on a chemically functionalized nanoporous diamond-like carbon (DLC) coated alumina membrane. The few nanometer-thick, yet perfect and continuous DLC-coating confers the chemical stability and biocompatibility of the sensor, allowing its direct application in biological conditions. The selective detection is based on complementary hybridization of a fluorescently-tagged circulating cancer oncomarker (a 21-mer nucleic acid) with covalently immobilized DNA on the surface of the membrane. The captured DNAs are detected in the nanoporous structure of the sensor using confocal scanning laser microscopy. The flow-through membrane sensor demonstrates broad-range sensitivity, spanning from 1015 molecules per cm2 down to single molecules, which is several orders of magnitude improvement compared to the flat DNA microarrays. Our study suggests that these flow-through type nanoporous sensors represent a new powerful platform for large volume sampling and ultrasensitive detection of different chemical biomarkers.Extracellular nucleic acids freely circulating in blood and other physiologic fluids are important biomarkers for non-invasive diagnostics and early detection of cancer and other diseases, yet difficult to detect because they exist in very low concentrations and large volumes. Here we demonstrate a new broad-range sensor platform for ultrasensitive and selective detection of circulating DNA down to the single-molecule level. The biosensor is based on a chemically functionalized nanoporous diamond-like carbon (DLC) coated

  11. On nanopore DNA sequencing by signal and noise analysis of ionic current.

    PubMed

    Wen, Chenyu; Zeng, Shuangshuang; Zhang, Zhen; Hjort, Klas; Scheicher, Ralph; Zhang, Shi-Li

    2016-05-27

    DNA sequencing, i.e., the process of determining the succession of nucleotides on a DNA strand, has become a standard aid in biomedical research and is expected to revolutionize medicine. With the capability of handling single DNA molecules, nanopore technology holds high promises to become speedier in sequencing at lower cost than what are achievable with the commercially available optics- or semiconductor-based massively parallelized technologies. Despite tremendous progress made with biological and solid-state nanopores, high error rates and large uncertainties persist with the sequencing results. Here, we employ a nano-disk model to quantitatively analyze the sequencing process by examining the variations of ionic current when a DNA strand translocates a nanopore. Our focus is placed on signal-boosting and noise-suppressing strategies in order to attain the single-nucleotide resolution. Apart from decreasing pore diameter and thickness, it is crucial to also reduce the translocation speed and facilitate a stepwise translocation. Our best-case scenario analysis points to severe challenges with employing plain nanopore technology, i.e., without recourse to any signal amplification strategy, in achieving sequencing with the desired single-nucleotide resolution. A conceptual approach based on strand synthesis in the nanopore of the translocating DNA from single-stranded to double-stranded is shown to yield a 10-fold signal amplification. Although it involves no advanced physics and is very simple in mathematics, this simple model captures the essence of nanopore sequencing and is useful in guiding the design and operation of nanopore sequencing. PMID:27095148

  12. On nanopore DNA sequencing by signal and noise analysis of ionic current

    NASA Astrophysics Data System (ADS)

    Wen, Chenyu; Zeng, Shuangshuang; Zhang, Zhen; Hjort, Klas; Scheicher, Ralph; Zhang, Shi-Li

    2016-05-01

    DNA sequencing, i.e., the process of determining the succession of nucleotides on a DNA strand, has become a standard aid in biomedical research and is expected to revolutionize medicine. With the capability of handling single DNA molecules, nanopore technology holds high promises to become speedier in sequencing at lower cost than what are achievable with the commercially available optics- or semiconductor-based massively parallelized technologies. Despite tremendous progress made with biological and solid-state nanopores, high error rates and large uncertainties persist with the sequencing results. Here, we employ a nano-disk model to quantitatively analyze the sequencing process by examining the variations of ionic current when a DNA strand translocates a nanopore. Our focus is placed on signal-boosting and noise-suppressing strategies in order to attain the single-nucleotide resolution. Apart from decreasing pore diameter and thickness, it is crucial to also reduce the translocation speed and facilitate a stepwise translocation. Our best-case scenario analysis points to severe challenges with employing plain nanopore technology, i.e., without recourse to any signal amplification strategy, in achieving sequencing with the desired single-nucleotide resolution. A conceptual approach based on strand synthesis in the nanopore of the translocating DNA from single-stranded to double-stranded is shown to yield a 10-fold signal amplification. Although it involves no advanced physics and is very simple in mathematics, this simple model captures the essence of nanopore sequencing and is useful in guiding the design and operation of nanopore sequencing.

  13. High order WENO scheme for computational cosmology

    NASA Astrophysics Data System (ADS)

    Roy, Ishani

    2010-11-01

    This doctoral dissertation is concerned with the formulation and application of a high order accurate numerical algorithm suitable in solving complex multi dimensional equations and the application of this algorithm to a problem in Astrophysics. The algorithm is designed with the aim of resolving solutions of partial differential equations with sharp fronts propagating with time. This high order accurate class of numerical technique is called a Weighted Essentially Non Oscillatory (WENO) method and is well suited for shock capturing in solving conservation laws. The numerical approximation method, in the algorithm, is coupled with high order time marching as well as integration techniques designed to reduce computational cost. This numerical algorithm is used in several applications in computational cosmology to help understand questions about certain physical phenomena which occurred during the formation and evolution of first generation stars. The thesis is divided broadly in terms of the algorithm and its application to the different galactic processes. The first chapter deals with the astrophysical problem and offers an introduction to the numerical algorithm. In chapter 2 we outline the mathematical model and the various functions and parameters associated with the model. We also give a brief description of the relevant physical phenomena and the conservation laws associated with them. In chapter 3, we give a detailed description of the higher order algorithm and its formulation. We also highlight the special techniques incorporated in the algorithm in order to make it more suitable for handling cases which are computationally intensive. In the later chapters, 4-7, we explore in detail the physical processes and the different applications of our numerical scheme. We calculate different results such as the time scale of a temperature coupling mechanism, radiation and intensity changes etc. Different tests are also performed to illustrate the stability and

  14. Reduction in thermal conductivity of Bi thin films with high-density ordered nanoscopic pores

    PubMed Central

    2013-01-01

    We prepared two-dimensional Bi thin films with high-density ordered nanoscopic pores by e-beam evaporation of Bi metal. For this structure, we used polystyrene beads ranging from 200 to 750 nm in diameter as an etch mask. The typical hole and neck sizes of the Bi thin films with approximately 50 nm in thickness on SiO2/Si substrates were in the range of 135 to 490 nm and 65 to 260 nm, respectively. By measuring the thermal characteristics through a 3ω technique, we found that the thermal conductivities of nanoporous Bi thin films are greatly suppressed compared with those of corresponding bulk materials. With a decrease in pore size to approximately 135 nm, the thermal conductivity decreased significantly to approximately 0.46 W/m·K at 300 K. PMID:24001222

  15. High-order counting statistics and interactions

    NASA Astrophysics Data System (ADS)

    Flindt, Christian

    2012-02-01

    Full counting statistics concerns the stochastic transport of electrons in mesoscopic structures [1]. Recently it has been shown that the charge transport statistics for noninteracting electrons in a two-terminal system is always generalized binomial: it can be decomposed into independent single-particle events, and the zeros of the generating function are real and negative [2]. In this talk I show how the zeros of the generating function move into the complex plane due to interactions and demonstrate how the positions of the zeros can be detected using high-order factorial cumulants [3]. As an illustrative example I discuss electron transport through a Coulomb blockade quantum dot for which the interactions on the quantum dot are clearly visible in the high-order factorial cumulants. These findings are important for understanding the influence of interactions on counting statistics, and the characterization in terms of zeros of the generating function provides a simple interpretation of recent experiments, where high-order statistics have been measured [4]. [4pt] [1] Yu. V. Nazarov, ed., Quantum Noise in Mesoscopic Physics, NATO Science Series, Vol. 97 (Kluwer, Dordrecht, 2003) [2] A. G. Abanov and D. A. Ivanov, Phys. Rev. Lett. 100, 086602 (2008), Phys. Rev. B 79, 205315 (2009) [3] D. Kambly, C. Flindt, and M. B"uttiker, Phys. Rev. B 83, 075432 (2011) -- Editors' Suggestion [4] C. Flindt, C. Fricke, F. Hohls, T. Novotn'y, K. Netocn'y, T. Brandes, and R. J. Haug, Proc. Natl. Acad. Sci. USA 106, 10116 (2009)

  16. Catalytic nanoporous membranes

    DOEpatents

    Pellin, Michael J.; Hryn, John N.; Elam, Jeffrey W.

    2009-12-01

    A nanoporous catalytic membrane which displays several unique features including pores which can go through the entire thickness of the membrane. The membrane has a higher catalytic and product selectivity than conventional catalysts. Anodic aluminum oxide (AAO) membranes serve as the catalyst substrate. This substrate is then subjected to Atomic Layer Deposition (ALD), which allows the controlled narrowing of the pores from 40 nm to 10 nm in the substrate by deposition of a preparatory material. Subsequent deposition of a catalytic layer on the inner surfaces of the pores reduces pore sizes to less than 10 nm and allows for a higher degree of reaction selectivity. The small pore sizes allow control over which molecules enter the pores, and the flow-through feature can allow for partial oxidation of reactant species as opposed to complete oxidation. A nanoporous separation membrane, produced by ALD is also provided for use in gaseous and liquid separations. The membrane has a high flow rate of material with 100% selectivity.

  17. Catalytic nanoporous membranes

    DOEpatents

    Pellin, Michael J; Hryn, John N; Elam, Jeffrey W

    2013-08-27

    A nanoporous catalytic membrane which displays several unique features Including pores which can go through the entire thickness of the membrane. The membrane has a higher catalytic and product selectivity than conventional catalysts. Anodic aluminum oxide (AAO) membranes serve as the catalyst substrate. This substrate is then subjected to Atomic Layer Deposition (ALD), which allows the controlled narrowing of the pores from 40 nm to 10 nm in the substrate by deposition of a preparatory material. Subsequent deposition of a catalytic layer on the inner surfaces of the pores reduces pore sizes to less than 10 nm and allows for a higher degree of reaction selectivity. The small pore sizes allow control over which molecules enter the pores, and the flow-through feature can allow for partial oxidation of reactant species as opposed to complete oxidation. A nanoporous separation membrane, produced by ALD is also provided for use in gaseous and liquid separations. The membrane has a high flow rate of material with 100% selectivity. Also provided is a method for producing a catalytic membrane having flow-through pores and discreet catalytic clusters adhering to the inside surfaces of the pores.

  18. Scaling Equation for yield strength of nanoporous open-cell foams

    SciTech Connect

    Hodge, A M; Biener, J; Hayes, J R; Bythrow, P M; A.Volkert, C; Hamza, A V

    2006-05-25

    A comprehensive study on the relationship between yield strength, relative density and ligament sizes is presented for nanoporous Au foams. Depth-sensing nanoindentation tests were performed on nanoporous foams ranging from 20 to 42% relative density with ligament sizes ranging from 10 to 900 nm. The Gibson and Ashby yield strength equation for open-cell macro-cellular foams is modified in order to incorporate ligament size effects. This study demonstrates that at the nanoscale, foam strength is governed by ligament size, in addition to relative density. Furthermore, we present the ligament length scale as a new parameter to tailor foam properties and achieve high strength at low densities.

  19. On High-Order Radiation Boundary Conditions

    NASA Technical Reports Server (NTRS)

    Hagstrom, Thomas

    1995-01-01

    In this paper we develop the theory of high-order radiation boundary conditions for wave propagation problems. In particular, we study the convergence of sequences of time-local approximate conditions to the exact boundary condition, and subsequently estimate the error in the solutions obtained using these approximations. We show that for finite times the Pade approximants proposed by Engquist and Majda lead to exponential convergence if the solution is smooth, but that good long-time error estimates cannot hold for spatially local conditions. Applications in fluid dynamics are also discussed.

  20. High Order Semi-Lagrangian Advection Scheme

    NASA Astrophysics Data System (ADS)

    Malaga, Carlos; Mandujano, Francisco; Becerra, Julian

    2014-11-01

    In most fluid phenomena, advection plays an important roll. A numerical scheme capable of making quantitative predictions and simulations must compute correctly the advection terms appearing in the equations governing fluid flow. Here we present a high order forward semi-Lagrangian numerical scheme specifically tailored to compute material derivatives. The scheme relies on the geometrical interpretation of material derivatives to compute the time evolution of fields on grids that deform with the material fluid domain, an interpolating procedure of arbitrary order that preserves the moments of the interpolated distributions, and a nonlinear mapping strategy to perform interpolations between undeformed and deformed grids. Additionally, a discontinuity criterion was implemented to deal with discontinuous fields and shocks. Tests of pure advection, shock formation and nonlinear phenomena are presented to show performance and convergence of the scheme. The high computational cost is considerably reduced when implemented on massively parallel architectures found in graphic cards. The authors acknowledge funding from Fondo Sectorial CONACYT-SENER Grant Number 42536 (DGAJ-SPI-34-170412-217).

  1. Electrochemistry of Graphene Edge Embedded Nanopores

    NASA Astrophysics Data System (ADS)

    Banerjee, Shouvik; Shim, Jiwook; Rivera, Jose; Jin, Xiaozhong; Estrada, David; Solovyeva, Vita; You, Xiuque; Pak, James; Pop, Eric; Aluru, Narayana; Bashir, Rashid

    2013-03-01

    We demonstrate a stacked graphene- Al2O3 dielectric nanopore architecture to investigate electrochemical activity at graphene edges. It has proven to be difficult to isolate electrochemical activity at the graphene edges from those at the basal planes. We use 24 nm of Al2O3 to isolate the graphene basal planes from an ionic fluid environment. Nanopores ranging from 5 to 20 nm are formed by an electron beam sculpting process to expose graphene edges. Electrochemical measurements at isolated graphene edges show current densities as high as 1.2 x 104 A/cm2, 300x greater than those reported for carbon nanotubes. Additionally, we modulate nanopore conductance by tuning the graphene edge electrochemical current as a function of the applied bias on the embedded graphene electrode. Our results indicate that electrochemical devices based on graphene nanopores have promising applications as sensitive chemical and biological sensors, energy storage devices, and DNA sequencing.

  2. Temporal resolution of nanopore sensor recordings.

    PubMed

    Rosenstein, Jacob K; Shepard, Kenneth L

    2013-01-01

    Here we discuss the limits to temporal resolution in nanopore sensor recordings, which arise from considerations of both small-signal frequency response and accumulated noise power. Nanopore sensors have strong similarities to patch-clamp ion channel recordings, except that the magnitudes of many physical parameters are substantially different. We will present examples from our recent work developing high-speed nanopore sensing platforms, in which we physically integrated nanopores with custom low-noise complementary metal-oxide-semiconductor (CMOS) circuitry. Close physical proximity of the sensor and amplifier electronics can reduce parasitic capacitances, improving both the signal-to-noise ratio and the effective temporal resolution of the recordings. PMID:24110636

  3. DNA nanopore translocation in glutamate solutions

    NASA Astrophysics Data System (ADS)

    Plesa, C.; van Loo, N.; Dekker, C.

    2015-08-01

    Nanopore experiments have traditionally been carried out with chloride-based solutions. Here we introduce silver/silver-glutamate-based electrochemistry as an alternative, and study the viscosity, conductivity, and nanopore translocation characteristics of potassium-, sodium-, and lithium-glutamate solutions. We show that it has a linear response at typical voltages and can be used to detect DNA translocations through a nanopore. The glutamate anion also acts as a redox-capable thickening agent, with high-viscosity solutions capable of slowing down the DNA translocation process by up to 11 times, with a corresponding 7 time reduction in signal. These results demonstrate that glutamate can replace chloride as the primary anion in nanopore resistive pulse sensing.

  4. Advanced Nanoporous Materials for Micro-Gravimetric Sensing to Trace-Level Bio/Chemical Molecules

    PubMed Central

    Xu, Pengcheng; Li, Xinxin; Yu, Haitao; Xu, Tiegang

    2014-01-01

    Functionalized nanoporous materials have been developed recently as bio/chemical sensing materials. Due to the huge specific surface of the nano-materials for molecular adsorption, high hopes have been placed on gravimetric detection with micro/nano resonant cantilevers for ultra-sensitive sensing of low-concentration bio/chemical substances. In order to enhance selectivity of the gravimetric resonant sensors to the target molecules, it is crucial to modify specific groups onto the pore-surface of the nano-materials. By loading the nanoporous sensing material onto the desired region of the mass-type transducers like resonant cantilevers, the micro-gravimetric bio/chemical sensors can be formed. Recently, such micro-gravimetric bio/chemical sensors have been successfully applied for rapid or on-the-spot detection of various bio/chemical molecules at the trace-concentration level. The applicable nanoporous sensing materials include mesoporous silica, zeolite, nanoporous graphene oxide (GO) and so on. This review article focuses on the recent achievements in design, preparation, functionalization and characterization of advanced nanoporous sensing materials for micro-gravimetric bio/chemical sensing. PMID:25313499

  5. Electron beam-assisted healing of nanopores in magnesium alloys

    PubMed Central

    Zheng, He; Liu, Yu; Cao, Fan; Wu, Shujing; Jia, Shuangfeng; Cao, Ajing; Zhao, Dongshan; Wang, Jianbo

    2013-01-01

    Nanopore-based sensing has emerged as a promising candidate for affordable and powerful DNA sequencing technologies. Herein, we demonstrate that nanopores can be successfully fabricated in Mg alloys via focused electron beam (e-beam) technology. Employing in situ high-resolution transmission electron microscopy techniques, we obtained unambiguous evidence that layer-by-layer growth of atomic planes at the nanopore periphery occurs when the e-beam is spread out, leading to the shrinkage and eventual disappearance of nanopores. The proposed healing process was attributed to the e-beam-induced anisotropic diffusion of Mg atoms in the vicinity of nanopore edges. A plausible diffusion mechanism that describes the observed phenomena is discussed. Our results constitute the first experimental investigation of nanopores in Mg alloys. Direct evidence of the healing process has advanced our fundamental understanding of surface science, which is of great practical importance for many technological applications, including thin film deposition and surface nanopatterning. PMID:23719630

  6. Electron beam-assisted healing of nanopores in magnesium alloys

    NASA Astrophysics Data System (ADS)

    Zheng, He; Liu, Yu; Cao, Fan; Wu, Shujing; Jia, Shuangfeng; Cao, Ajing; Zhao, Dongshan; Wang, Jianbo

    2013-05-01

    Nanopore-based sensing has emerged as a promising candidate for affordable and powerful DNA sequencing technologies. Herein, we demonstrate that nanopores can be successfully fabricated in Mg alloys via focused electron beam (e-beam) technology. Employing in situ high-resolution transmission electron microscopy techniques, we obtained unambiguous evidence that layer-by-layer growth of atomic planes at the nanopore periphery occurs when the e-beam is spread out, leading to the shrinkage and eventual disappearance of nanopores. The proposed healing process was attributed to the e-beam-induced anisotropic diffusion of Mg atoms in the vicinity of nanopore edges. A plausible diffusion mechanism that describes the observed phenomena is discussed. Our results constitute the first experimental investigation of nanopores in Mg alloys. Direct evidence of the healing process has advanced our fundamental understanding of surface science, which is of great practical importance for many technological applications, including thin film deposition and surface nanopatterning.

  7. Use of ZIF-8-derived nanoporous carbon as the adsorbent for the solid phase extraction of carbamate pesticides prior to high-performance liquid chromatographic analysis.

    PubMed

    Hao, Lin; Liu, Xingli; Wang, Juntao; Wang, Chun; Wu, Qiuhua; Wang, Zhi

    2015-09-01

    In this work, a chemically and thermally robust and highly porous zeolite-type metal-organic framework, zeolitic imidazolate framework-8 (ZIF-8), was used as both a precursor and a template and furfuryl alcohol as a second precursor to synthesize a nanoporous carbon. The prepared ZIF-8-derived nanoporous carbon was used as the solid-phase extraction adsorbent for the extraction of carbamate pesticides from cabbage and water samples. The adsorbed analytes were eluted with acetonitrile for the determination by high performance liquid chromatography-ultraviolet detection. The high surface area, high porosity, good stability and fast adsorption/desorption kinetics of the material enabled it to have a high adsorption capacity and good adsorption performance. Under optimum conditions, good linearity for the analytes in the range of 0.5-100 ng g(-1) and 0.05-20 ng mL(-1) existed for cabbage and water samples with the correlation coefficients of 0.9968-0.9980 and 0.9990-0.9995, respectively. The limits of detection (S/N=3) for the analytes were in the range of 0.25-0.1 ng g(-1) and 0.01-0.02 ng mL(-1) for the cabbage and water samples, respectively. The relative standard deviations (RSDs) for intra-day and the inter-day determinations of the analytes were below 7.0% and 12.5%, respectively. PMID:26003698

  8. Membrane platforms for biological nanopore sensing and sequencing.

    PubMed

    Schmidt, Jacob

    2016-06-01

    In the past two decades, biological nanopores have been developed and explored for use in sensing applications as a result of their exquisite sensitivity and easily engineered, reproducible, and economically manufactured structures. Nanopore sensing has been shown to differentiate between highly similar analytes, measure polymer size, detect the presence of specific genes, and rapidly sequence nucleic acids translocating through the pore. Devices featuring protein nanopores have been limited in part by the membrane support containing the nanopore, the shortcomings of which have been addressed in recent work developing new materials, approaches, and apparatus resulting in membrane platforms featuring automatability and increased robustness, lifetime, and measurement throughput. PMID:26773300

  9. An electron paramagnetic resonance spectroscopy investigation of the retention mechanisms of Mn and Cu in the nanopore channels of three zeolite minerals

    SciTech Connect

    Ferreira, Daniel R.; Schulthess, Cristian P.; Amonette, James E.; Walter, Eric D.

    2012-12-01

    The adsorption mechanisms of divalent cations in zeolite nanopore channels can vary as a function of their pore dimensions. The nanopore inner-sphere enhancement (NISE) theory predicts that ions may dehydrate inside small nanopore channels in order to adsorb more closely to the mineral surface if the nanopore channel is sufficiently small. The results of an electron paramagnetic resonance (EPR) spectroscopy study of Mn and Cu adsorption on the zeolite minerals zeolite Y (large nanopores), ZSM-5 (intermediate nanopores), and mordenite (small nanopores) are presented. The Cu and Mn cations both adsorbed via an outer-sphere mechanism on zeolite Y based on the similarity between the adsorbed spectra and the aqueous spectra. Conversely, Mn and Cu adsorbed via an inner-sphere mechanism on mordenite based on spectrum asymmetry and peak broadening of the adsorbed spectra. However, Mn adsorbed via an outer-sphere mechanism on ZSM-5, whereas Cu adsorbed on ZSM-5 shows a high degree of surface interaction that indicates that it is adsorbed closer to the mineral surface. Evidence of dehydration and immobility was more readily evident in the spectrum of mordenite than ZSM-5, indicating that Cu was not as close to the surface on ZSM-5 as it was when adsorbed on mordenite. Divalent Mn cations are strongly hydrated and are held strongly only in zeolites with small nanopore channels. Divalent Cu cations are also strongly hydrated, but can dehydrate more easily, presumably due to the Jahn-Teller effect, and are held strongly in zeolites with medium sized nanopore channels or smaller.

  10. Adiabatic burst evaporation from bicontinuous nanoporous membranes

    PubMed Central

    Ichilmann, Sachar; Rücker, Kerstin; Haase, Markus; Enke, Dirk

    2015-01-01

    Evaporation of volatile liquids from nanoporous media with bicontinuous morphology and pore diameters of a few 10 nm is an ubiquitous process. For example, such drying processes occur during syntheses of nanoporous materials by sol–gel chemistry or by spinodal decomposition in the presence of solvents as well as during solution impregnation of nanoporous hosts with functional guests. It is commonly assumed that drying is endothermic and driven by non-equilibrium partial pressures of the evaporating species in the gas phase. We show that nearly half of the liquid evaporates in an adiabatic mode involving burst-like liquid-to-gas conversions. During single adiabatic burst evaporation events liquid volumes of up to 107 μm3 are converted to gas. The adiabatic liquid-to-gas conversions occur if air invasion fronts get unstable because of the built-up of high capillary pressures. Adiabatic evaporation bursts propagate avalanche-like through the nanopore systems until the air invasion fronts have reached new stable configurations. Adiabatic cavitation bursts thus compete with Haines jumps involving air invasion front relaxation by local liquid flow without enhanced mass transport out of the nanoporous medium and prevail if the mean pore diameter is in the range of a few 10 nm. The results reported here may help optimize membrane preparation via solvent-based approaches, solution-loading of nanopore systems with guest materials as well as routine use of nanoporous membranes with bicontinuous morphology and may contribute to better understanding of adsorption/desorption processes in nanoporous media. PMID:25926406

  11. Translocation of a Polymer Chain Through a Nanopore Starting From a Confining Nanotube: The Limit of high Peclet Numbers

    NASA Astrophysics Data System (ADS)

    Slater, Gary W.; Sean, David; de Haan, Hendrick

    2015-03-01

    We use Langevin Dynamics simulations to study a scenario where a confining nanotube is used as a way to limit the range of conformations available to a polymer chain prior to driven translocation. We find that the tube not only reduces the variance in translocation times (a useful result for practical applications), but also that the elongated polymer conformations yield longer translocation times (also a useful result) that can be dominated by the post-propagation process when the diameter of the nanotube is smaller than a universal critical value. We adapt the tension propagation theory for this geometry and find agreement with the simulations using a single friction parameter to model the roles of both the nanopore and the crowding. To gain insight into the physical mechanisms behind this effective friction, we systematically remove i) crowding on the trans-side and/or ii) monomer collisions with the membrane containing the nanopore. We find that higher Peclet numbers increase the impact of crowding on the trans side but diminish the impact of the friction between the nanopore and the polymer.

  12. DNA translocation through single-layer boron nitride nanopores.

    PubMed

    Gu, Zonglin; Zhang, Yuanzhao; Luan, Binquan; Zhou, Ruhong

    2016-01-21

    Ultra-thin nanopores have become promising biological sensors because of their outstanding signal-to-noise ratio and spatial resolution. Here, we show that boron nitride (BN), which is a new two-dimensional (2D) material similar to graphene, could be utilized for making a nanopore with an atomic thickness. Using an all-atom molecular dynamics simulation, we investigated the dynamics of DNA translocation through the BN nanopore. The results of our simulations demonstrated that it is possible to detect different double-stranded DNA (dsDNA) sequences from the recording of ionic currents through the pore during the DNA translocation. Surprisingly, opposite to results for a graphene nanopore, we found the calculated blockage current for poly(A-T)40 in a BN nanopore to be less than that for poly(G-C)40. Also in contrast with the case of graphene nanopores, dsDNA models moved smoothly and in an unimpeded manner through the BN nanopores in the simulations, suggesting a potential advantage for using BN nanopores to design stall-free sequencing devices. BN nanopores, which display several properties (such as being hydrophilic and non-metallic) that are superior to those of graphene, are thus expected to find applications in the next generation of high-speed and low-cost biological sensors. PMID:26537824

  13. IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED IN STABLE NANOPOROUS HOST

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2005-03-31

    The objectives of this project are to synthesis nanocrystals of highly acidic zeolite Y, encapsulate them within the channels of mesoporous (nanoporous) silicates or nanoporous organosilicates and evaluate the ''zeolite Y/Nanoporous host'' composites as catalysts for the upgrading of heavy petroleum feedstocks. Our results to date are summarized as follows. The synthesis of high surface ordered nanoporous silica of expanded pore diameter of 25 nm (larger than the standard size of 8.4 nm) using trimethylbenzene as a pore size expander was accomplished. The synthesis of zeolite Y nanoparticles with median pore size of approximately 50 nm (smaller than the 80 nm typically obtained with TMAOH) using combined TMABr/TMAOH as organic additives was also accomplished. The successful synthesis of zeoliteY/Nanoporous host composite materials by sequential combination of zeolite precursors and nanoporous material precursor mixtures was implied based on results from various characterization techniques such as X-Ray diffraction, infrared spectra, thermal analysis, porosimetry data. The resulting materials showed pore sizes up to 11 nm, and infrared band at 570 cm{sup -1} suggesting the presence of both phases. New results indicated that good quality highly ordered nanoporous silica host can be synthesized in the presence of zeolite Y seed precursor depending on the amount of precursor added. Preliminary research on the catalytic performance of the materials is underway. Probe acid catalyzed reactions, such as the cracking of cumene is currently being conducted. Work in the immediate future will be focused on the following three areas: (1) Further characterization of all-silica and aluminosilicate mesoporous materials with expanded pore sizes up to 30 nm will continue; (2) Research efforts to reduce the average particle size of zeolite nanoparticles down to 35-30 nm will continue; (3) Further synthesis of ZeoliteY/Nanoporous host composite catalysts of improved structural and

  14. Highly optimized CO2 capture by inexpensive nanoporous covalent organic polymers and their amine composites.

    PubMed

    Patel, Hasmukh A; Yavuz, Cafer T

    2015-01-01

    Carbon dioxide (CO2) storage and utilization requires effective capture strategies that limit energy penalties. Polyethylenimine (PEI)-impregnated covalent organic polymers (COPs) with a high CO2 adsorption capacity are successfully prepared in this study. A low cost COP with a high specific surface area is suitable for PEI loading to achieve high CO2 adsorption, and the optimal PEI loading is 36 wt%. Though the adsorbed amount of CO2 on amine impregnated COPs slightly decreased with increasing adsorption temperature, CO2/N2 selectivity is significantly improved at higher temperatures. The adsorption of CO2 on the sorbent is very fast, and a sorption equilibrium (10% wt) was achieved within 5 min at 313 K under the flow of simulated flue gas streams. The CO2 capture efficiency of this sorbent is not affected under repetitive adsorption-desorption cycles. The highest CO2 capture capacity of 75 mg g(-1) at 0.15 bar is achieved under dry CO2 capture however it is enhanced to 100 mg g(-1) in the mixed gas flow containing humid 15% CO2. Sorbents were found to be thermally stable up to at least 200 °C. TGA and FTIR studies confirmed the loading of PEIs on COPs. This sorbent with high and fast CO2 sorption exhibits a very promising application in direct CO2 capture from flue gas. PMID:26388535

  15. Fabrication of nanofluidic diodes with polymer nanopores modified by atomic layer deposition

    PubMed Central

    Sheng, Qian; Wang, Lin; Wang, Ceming; Wang, Xinwei; Xue, Jianming

    2014-01-01

    Surface charge distribution is a crucial factor for the ionic transport properties inside nanopores. Modifying the surface charge inside a single conical nanopore can greatly affect the rectification behavior of the ionic current through the nanopore and afford nanofluidic diodes. In this work, we describe a new method to fabricate nanofluidic diodes by atomic layer deposition (ALD) on conical track-etched nanopores. Thorough investigation of the ionic transport behavior through ALD-modified polyethylene terephthalate (PET) nanopores is carried out. Our results demonstrate that ALD is a simple and effective method to modify the inner surface of the polymer nanopores for fabricating nanofluidic devices. In addition, we also investigate the stability of the ALD-modified nanopores, and the results suggest that the long-time stability could be compromised by high voltage applied along the nanopore. PMID:25332737

  16. High electrokinetic energy conversion efficiency in charged nanoporous nitrocellulose/sulfonated polystyrene membranes.

    PubMed

    Haldrup, Sofie; Catalano, Jacopo; Hansen, Michael Ryan; Wagner, Manfred; Jensen, Grethe Vestergaard; Pedersen, Jan Skov; Bentien, Anders

    2015-02-11

    The synthesis, characterization, and electrokinetic energy conversion performance have been investigated experimentally in a charged polymeric membrane based on a blend of nitrocellulose and sulfonated polystyrene. The membrane is characterized by a moderate ion exchange capacity and a relatively porous structure with average pore diameter of 11 nm. With electrokinetic energy conversion, pressure can be converted directly into electric energy and vice versa. From the electrokinetic transport properties, a remarkably large intrinsic maximum efficiency of 46% is found. It is anticipated that the results are an experimental verification of theoretical models that predict high electrokinetic energy conversion efficiency in pores with high permselectivity and hydrodynamic slip flow. Furthermore, the result is a promising step for obtaining efficient low-cost electrokinetic generators and pumps for small or microscale applications. PMID:25555128

  17. A highly sensitive and stable electrochemical sensor for simultaneous detection towards ascorbic acid, dopamine, and uric acid based on the hierarchical nanoporous PtTi alloy.

    PubMed

    Zhao, Dianyun; Yu, Guolong; Tian, Kunlong; Xu, Caixia

    2016-08-15

    In current work highly sensitive and stable electrochemical sensor for simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA) is constructed based on the hierarchical nanoporous (HNP) PtTi alloy. The HNP-PtTi alloy is simply fabricated by two-step dealloying process, characterized by the bimodal ligament/pore size distributions and interconnected hollow channels. The HNP structure with the advantages of large surface area, excellent structure stability, and rich pore channels is used for facilitating the electron conductivity and the mass transfer. Combined with the dual effects of the bimodal nanoporous architecture and the excellent electrocatalytic activity of PtTi alloy, the constructed sensor exhibits high electrochemical sensing activity with wide linear responses from 0.2 to 1mM, 0.004 to 0.5mM, and 0.1 to 1mM for simultaneous detection of AA, DA, and UA, respectively. In addition, HNP-PtTi alloy also shows long-term sensing stability towards the AA, DA, and UA detection and behaves as a good anti-interference towards NaCl, KCl, FeCl3, CuCl2, AlCl3, glucose, and H2O2. The HNP-PtTi alloy manifests intriguing application potential as the candidate for the application of the electrochemical sensor for simultaneous detection of AA, DA, and UA. PMID:27058442

  18. Local Release of Highly Loaded Antibodies from Functionalized Nanoporous Support for Cancer Immunotherapy

    SciTech Connect

    Lei, Chenghong; Liu, P.; Chen, Baowei; Mao, Yumeng; Engelmann, Heather E.; Shin, Yongsoon; Jaffar, Jade; Hellstrom, Ingegerd; Liu, Jun; Hellstrom, Karl E.

    2010-05-26

    We report that antibodies can be loaded in functionalized mesoporous silica (FMS) with super-high density to provide long-lasting local release at a given site. Preliminary data indicate that FMS-antibody injected directly into a mouse melanoma induces a greater inhibition of tumor growth than seen in various controls, including the antibody injected intraperitoneally. Our findings introduce a novel approach for local delivery of therapeutically active proteins to tumors and potentially, other diseases.

  19. Methane Storage in Nanoporous Media as Observed via High-Field NMR Relaxometry

    NASA Astrophysics Data System (ADS)

    Papaioannou, A.; Kausik, R.

    2015-08-01

    The storage properties of methane gas in Vycor porous glass (5.7 nm) are characterized in a wide pressure range from 0.7 to 89.7 MPa using nuclear magnetic resonance. We demonstrate the capability of high-field nuclear-magnetic-resonance relaxometry for the determination of the methane-gas storage capacity and the measurement of the hydrogen index, to a high degree of accuracy. This helps determine the excess gas in the pore space which can be identified to exhibit Langmuir properties in the low pressure regime of 0.7 to 39.6 MPa. The Langmuir model enables us to determine the equilibrium density of the monolayer of adsorbed gas to be 8.5% lower than that of liquid methane. We also identify the signatures of multilayer adsorption at the high pressure regime from 39.6 to 89.7 MPa and use the Brunauer-Emmet-Teller theory to determine the number of adsorbed layers of methane gas. We show how these measurements help us differentiate the gas stored in the Vycor pore space into free and adsorbed fractions for the entire pressure range paving way for similar applications such as studying natural-gas storage in gas shale rock or hydrogen storage in carbon nanotubes.

  20. IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED STABLE NANOPOROUS HOST

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2005-03-21

    The objectives of this project are to synthesis nanocrystals of highly acidic zeolite Y, encapsulate them within the channels of mesoporous (nanoporous) silicates or nanoporous organosilicates and evaluate the ''zeolite Y/Nanoporous host'' composites as catalysts for the upgrading of heavy petroleum feedstocks. Our results to date are summarized as follows. The synthesis of high surface ordered nanoporous silica of expanded pore diameter of 25 nm (larger than the standard size of 8.4 nm) using trimethylbenzene as a pore size expander was accomplished. The synthesis of zeolite Y nanoparticles with median pore size of approximately 50 nm (smaller than the 80 nm typically obtained with TMAOH) using combined TMABr/TMAOH as organic additives was also accomplished. The successful synthesis of zeoliteY/Nanoporous host composite materials by sequential combination of zeolite precursors and nanoporous material precursor mixtures was implied based on results from various characterization techniques such as X-Ray diffraction, infrared spectra, thermal analysis, porosimetry data. The resulting materials showed pore sizes up to 11 nm, and infrared band at 570 cm{sup -1} suggesting the presence of both phases. Work in the immediate future will be focused on the following three areas: (1) Further characterization of all-silica and aluminosilicate mesoporous materials with expanded pore sizes up to 30 nm will continue; (2) Research efforts to reduce the average particle size of zeolite nanoparticles down to 35-30 nm will continue; (3) Further synthesis of polymer-SBA15 nanocomposites will be conducted by changing the amount and chemistry of the zeolitic precursors added; and (4) Investigation on the catalytic properties of the materials using probe catalytic reactions (such as cumene cracking), followed by catalytic testing for heavy oil conversion.

  1. Nanoporous carbon-based electrodes for high strain ionomeric bending actuators

    NASA Astrophysics Data System (ADS)

    Palmre, Viljar; Brandell, Daniel; Mäeorg, Uno; Torop, Janno; Volobujeva, Olga; Punning, Andres; Johanson, Urmas; Kruusmaa, Maarja; Aabloo, Alvo

    2009-09-01

    Ionic polymer metal composites (IPMCs) are electroactive material devices that bend at low applied voltage (1-4 V). Inversely, a voltage is generated when the materials are deformed, which makes them useful both as sensors and actuators. In this paper, we propose two new highly porous carbon materials as electrodes for IPMC actuators, generating a high specific area, and compare their electromechanical performance with recently reported RuO2 electrodes and conventional IPMCs. Using a direct assembly process (DAP), we synthesize ionic liquid (Emi-Tf) actuators with either carbide-derived carbon (CDC) or coconut-shell-based activated carbon-based electrodes. The carbon electrodes were applied onto ionic liquid-swollen Nafion membranes using a direct assembly process. The study demonstrates that actuators based on carbon electrodes derived from TiC have the greatest peak-to-peak strain output, reaching up to 20.4 mɛ (equivalent to>2%) at a 2 V actuation signal, exceeding that of the RuO2 electrodes by more than 100%. The electrodes synthesized from TiC-derived carbon also exhibit significantly higher maximum strain rate. The differences between the materials are discussed in terms of molecular interactions and mechanisms upon actuation in the different electrodes.

  2. High phase order transmission demonstration. Final report

    SciTech Connect

    Krizauskas, E.; Landers, T.L.; Richeda, R.J.; Oppel, L.J.; Stewart, J.R.

    1997-12-01

    High-phase-order (HPO), or six-phase, transmission is an extension of line compaction that further increases the power transfer capability of a limited transmission line right-of-way. On July 1, 1992, the first commercially operated six-phase transmission line was energized as a tie line integrated into the New York State Electric and Gas (NYSEG) existing three-phase power system. Previous Empire State Electric Energy Research Corporation (ESEERCO) Project EP 88-23 reports detail the analytical framework and conceptual studies (Phase 1) and the detailed engineering and design/construction (Phase 2) that preceded the 1992 energization. After the six-phase line was constructed, a testing program verified the theoretical predictions of electrical effects due to six-phase construction. This Final Project Report details the results of the Phase 3 testing program and examines steady-state power frequency parameters, partial switching, corona effects, and field effects. In addition, this report details the results of two unplanned unstaged faults, and low-level staged faults. After one year of operation, results led to the identification of aspects that warranted additional study and evaluation. This report summarizes these additional investigations and evaluations of midspan spacers, off-the-shelf microprocessor-based relays for six-phase line protection, live line maintenance, possible standard six-phase station designs, and an economic evaluation of break-even distances for which six-phase is more economical than conventional double-circuit three-phase applications for line upgrades and new construction.

  3. High order harmonic generation in rare gases

    SciTech Connect

    Budil, K.S.

    1994-05-01

    The process of high order harmonic generation in atomic gases has shown great promise as a method of generating extremely short wavelength radiation, extending far into the extreme ultraviolet (XUV). The process is conceptually simple. A very intense laser pulse (I {approximately}10{sup 13}-10{sup 14} W/cm{sup 2}) is focused into a dense ({approximately}10{sup l7} particles/cm{sup 3}) atomic medium, causing the atoms to become polarized. These atomic dipoles are then coherently driven by the laser field and begin to radiate at odd harmonics of the laser field. This dissertation is a study of both the physical mechanism of harmonic generation as well as its development as a source of coherent XUV radiation. Recently, a semiclassical theory has been proposed which provides a simple, intuitive description of harmonic generation. In this picture the process is treated in two steps. The atom ionizes via tunneling after which its classical motion in the laser field is studied. Electron trajectories which return to the vicinity of the nucleus may recombine and emit a harmonic photon, while those which do not return will ionize. An experiment was performed to test the validity of this model wherein the trajectory of the electron as it orbits the nucleus or ion core is perturbed by driving the process with elliptically, rather than linearly, polarized laser radiation. The semiclassical theory predicts a rapid turn-off of harmonic production as the ellipticity of the driving field is increased. This decrease in harmonic production is observed experimentally and a simple quantum mechanical theory is used to model the data. The second major focus of this work was on development of the harmonic {open_quotes}source{close_quotes}. A series of experiments were performed examining the spatial profiles of the harmonics. The quality of the spatial profile is crucial if the harmonics are to be used as the source for experiments, particularly if they must be refocused.

  4. Oscillation of Capacitance inside Nanopores

    SciTech Connect

    Jiang, De-en; Jin, Zhehui; Wu, Jianzhong

    2011-10-26

    Porous carbons of high surface area are promising as cost-effective electrode materials for supercapacitors. Although great attention has been given to the anomalous increase of the capacitance as the pore size approaches the ionic dimensions, there remains a lack of full comprehension of the size dependence of the capacitance in nanopores. Here we predict from a classical density functional theory that the capacitance of an ionic-liquid electrolyte inside a nanopore oscillates with a decaying envelope as the pore size increases. The oscillatory behavior can be attributed to the interference of the overlapping electric double layers (EDLs); namely, the maxima in capacitance appear when superposition of the two EDLs is most constructive. The theoretical prediction agrees well with the experiment when the pore size is less than twice the ionic diameter. Confirmation of the entire oscillatory spectrum invites future experiments with a precise control of the pore size from micro- to mesoscales.

  5. Surface-enhanced Raman spectroscopy on laser-engineered ruthenium dye-functionalized nanoporous gold

    NASA Astrophysics Data System (ADS)

    Schade, Lina; Franzka, Steffen; Biener, Monika; Biener, Jürgen; Hartmann, Nils

    2016-06-01

    Photothermal processing of nanoporous gold with a microfocused continuous-wave laser at λ = 532 nm provides a facile means in order engineer the pore and ligament size of nanoporous gold. In this report we take advantage of this approach in order to investigate the size-dependence of enhancement effects in surface-enhanced Raman spectroscopy (SERS). Surface structures with laterally varying pore sizes from 25 nm to ≥200 nm are characterized using scanning electron microscopy and then functionalized with N719, a commercial ruthenium complex, which is widely used in dye-sensitized solar cells. Raman spectroscopy reveals the characteristic spectral features of N719. Peak intensities strongly depend on the pore size. Highest intensities are observed on the native support, i.e. on nanoporous gold with pore sizes around 25 nm. These results demonstrate the particular perspectives of laser-fabricated nanoporous gold structures in fundamental SERS studies. In particular, it is emphasized that laser-engineered porous gold substrates represent a very well defined platform in order to study size-dependent effects with high reproducibility and precision and resolve conflicting results in previous studies.

  6. Nanoporous polymer electrolyte

    SciTech Connect

    Elliott, Brian; Nguyen, Vinh

    2012-04-24

    A nanoporous polymer electrolyte and methods for making the polymer electrolyte are disclosed. The polymer electrolyte comprises a crosslinked self-assembly of a polymerizable salt surfactant, wherein the crosslinked self-assembly includes nanopores and wherein the crosslinked self-assembly has a conductivity of at least 1.0.times.10.sup.-6 S/cm at 25.degree. C. The method of making a polymer electrolyte comprises providing a polymerizable salt surfactant. The method further comprises crosslinking the polymerizable salt surfactant to form a nanoporous polymer electrolyte.

  7. High order accurate solutions of viscous problems

    NASA Technical Reports Server (NTRS)

    Hayder, M. E.; Turkel, Eli

    1993-01-01

    We consider a fourth order extension to MacCormack's scheme. The original extension was fourth order only for the inviscid terms but was second order for the viscous terms. We show how to modify the viscous terms so that the scheme is uniformly fourth order in the spatial derivatives. Applications are given to some boundary layer flows. In addition, for applications to shear flows the effect of the outflow boundary conditions are very important. We compare the accuracy of several of these different boundary conditions for both boundary layer and shear flows. Stretching at the outflow usually increases the oscillations in the numerical solution but the addition of a filtered sponge layer (with or without stretching) reduces such oscillations. The oscillations are generated by insufficient resolution of the shear layer. When the shear layer is sufficiently resolved then oscillations are not generated and there is less of a need for a nonreflecting boundary condition.

  8. High-Order Energy Stable WENO Schemes

    NASA Technical Reports Server (NTRS)

    Yamaleev, Nail K.; Carpenter, Mark H.

    2009-01-01

    A third-order Energy Stable Weighted Essentially Non-Oscillatory (ESWENO) finite difference scheme developed by Yamaleev and Carpenter was proven to be stable in the energy norm for both continuous and discontinuous solutions of systems of linear hyperbolic equations. Herein, a systematic approach is presented that enables 'energy stable' modifications for existing WENO schemes of any order. The technique is demonstrated by developing a one-parameter family of fifth-order upwind-biased ESWENO schemes; ESWENO schemes up to eighth order are presented in the appendix. New weight functions are also developed that provide (1) formal consistency, (2) much faster convergence for smooth solutions with an arbitrary number of vanishing derivatives, and (3) improved resolution near strong discontinuities.

  9. IMPROVED CATALYSTS FOR HEAVY OIL UPGRADING BASED ON ZEOLITE Y NANOPARTICLES ENCAPSULATED IN STABLE NANOPOROUS HOSTS

    SciTech Connect

    Conrad Ingram; Mark Mitchell

    2004-06-30

    The focus of this project is to improve the catalytic performance of zeolite Y for heavy petroleum hydrocracking by synthesizing nanoparticles of the zeolite ({approx}20-30 nm) inside nanoporous silicate or aluminosilicate hosts of similar pore diameters. The encapsulated zeolite nanoparticles are expected to possess pores of reduced diffusional path lengths, hence hydrocarbon substrates will diffuse in, are converted and the products quickly diffused out. This is expected to prevent over-reaction, hence minimizing pore blockage and active sites deactivation. In this phase of the project, research activities were focused on refining procedures to: (a) improve the synthesis of ordered, high surface area nanoporous silica, such as SBA-15, with expanded pore size using trimethylbenzene as additive to the parent SBA-15 synthesis mixture; and (b) reduce the particle size of zeolite Y such that they can be effectively incorporated into the nanoporous silicas. The synthesis of high surface ordered nanoporous silica containing enlarged pores of diameter of 25 nm (larger than the standard size of 8.4 nm) using trimethylbenzene as a pore size expander was accomplished. The synthesis of zeolite Y nanoparticles with median pore size of approximately 50 nm (smaller than the 80 nm typically obtained with TMAOH) using combined TMABr/TMAOH as organic additives was also accomplished.

  10. Evaporation-induced self-assembled silica colloidal particle-assisted nanoporous structural evolution of poly(ethylene terephthalate) nonwoven composite separators for high-safety/high-rate lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Lee, Jung-Ran; Won, Ji-Hye; Kim, Jong Hun; Kim, Ki Jae; Lee, Sang-Young

    2012-10-01

    A facile approach to the fabrication of nanoporous structure-tuned nonwoven composite separators is demonstrated for application in high-safety/high-rate lithium-ion batteries. This strategy is based on the construction of silica (SiO2) colloidal particle-assisted nanoporous structure in a poly(ethylene terephthalate) (PET) nonwoven substrate. The nanoparticle arrangement arising from evaporation-induced self-assembly of SiO2 colloidal particles allows the evolution of the unusual nanoporous structure, i.e. well-connected interstitial voids formed between close-packed SiO2 particles adhered by styrene-butadiene rubber (SBR) binders. Meanwhile, the PET nonwoven serves as a mechanical support that contributes to suppressing thermal shrinkage of the nonwoven composite separator. The aforementioned structural novelty of the nonwoven composite separator plays a key role in providing the separator with advantageous characteristics (specifically, good electrolyte wettability, high ionic conductivity, and benign compatibility with electrodes), which leads to the better cell performance than a commercialized polyethylene (PE) separator.

  11. The role of nanopore shape in surface-induced crystallization

    NASA Astrophysics Data System (ADS)

    Diao, Ying; Harada, Takuya; Myerson, Allan S.; Alan Hatton, T.; Trout, Bernhardt L.

    2011-11-01

    Crystallization of a molecular liquid from solution often initiates at solid-liquid interfaces, and nucleation rates are generally believed to be enhanced by surface roughness. Here we show that, on a rough surface, the shape of surface nanopores can also alter nucleation kinetics. Using lithographic methods, we patterned polymer films with nanopores of various shapes and found that spherical nanopores 15-120 nm in diameter hindered nucleation of aspirin crystals, whereas angular nanopores of the same size promoted it. We also show that favourable surface-solute interactions are required for angular nanopores to promote nucleation, and propose that pore shape affects nucleation kinetics through the alteration of the orientational order of the crystallizing molecule near the angles of the pores. Our findings have clear technological implications, for instance in the control of pharmaceutical polymorphism and in the design of ‘seed’ particles for the regulation of crystallization of fine chemicals.

  12. A high performance totally ordered multicast protocol

    NASA Technical Reports Server (NTRS)

    Montgomery, Todd; Whetten, Brian; Kaplan, Simon

    1995-01-01

    This paper presents the Reliable Multicast Protocol (RMP). RMP provides a totally ordered, reliable, atomic multicast service on top of an unreliable multicast datagram service such as IP Multicasting. RMP is fully and symmetrically distributed so that no site bears un undue portion of the communication load. RMP provides a wide range of guarantees, from unreliable delivery to totally ordered delivery, to K-resilient, majority resilient, and totally resilient atomic delivery. These QoS guarantees are selectable on a per packet basis. RMP provides many communication options, including virtual synchrony, a publisher/subscriber model of message delivery, an implicit naming service, mutually exclusive handlers for messages, and mutually exclusive locks. It has commonly been held that a large performance penalty must be paid in order to implement total ordering -- RMP discounts this. On SparcStation 10's on a 1250 KB/sec Ethernet, RMP provides totally ordered packet delivery to one destination at 842 KB/sec throughput and with 3.1 ms packet latency. The performance stays roughly constant independent of the number of destinations. For two or more destinations on a LAN, RMP provides higher throughput than any protocol that does not use multicast or broadcast.

  13. High-order tail in Schwarzschild spacetime

    NASA Astrophysics Data System (ADS)

    Casals, Marc; Ottewill, Adrian

    2015-12-01

    We present an analysis of the behavior at late times of linear field perturbations of a Schwarzschild black hole spacetime. In particular, we give explicit analytic expressions for the field perturbations (for a specific ℓ-multipole) of general spin up to the first four orders at late times. These expressions are valid at arbitrary radius and include, apart from the well-known power-law tail decay at leading order (˜t-2 ℓ-3), a new logarithmic behavior at third leading order (˜t-2 ℓ-5ln t ). We obtain these late-time results by developing an analytical formalism initially formulated by Mano, Suzuki and Takasugi (MST) [Prog. Theor. Phys. 95, 1079 (1996); 96, 549 (1996)] formalism and by expanding the various MST Fourier-mode quantities for small frequency. While we give explicit expansions up to the first four leading orders (for small frequency for the Fourier modes, for late time for the field perturbation), we give a prescription for obtaining expressions to arbitrary order within a "perturbative regime."

  14. Thin Nanoporous Metal-Insulator-Metal Membranes.

    PubMed

    Aramesh, Morteza; Djalalian-Assl, Amir; Yajadda, Mir Massoud Aghili; Prawer, Steven; Ostrikov, Kostya Ken

    2016-02-01

    Insulating nanoporous materials are promising platforms for soft-ionizing membranes; however, improvement in fabrication processes and the quality and high breakdown resistance of the thin insulator layers are needed for high integration and performance. Here, scalable fabrication of highly porous, thin, silicon dioxide membranes with controlled thickness is demonstrated using plasma-enhanced chemical-vapor-deposition. The fabricated membranes exhibit good insulating properties with a breakdown voltage of 1 × 10(7) V/cm. Our calculations suggest that the average electric field inside a nanopore of the membranes can be as high as 1 × 10(6) V/cm; sufficient for ionization of wide range of molecules. These metal-insulator-metal nanoporous arrays are promising for applications such soft ionizing membranes for mass spectroscopy. PMID:26846250

  15. Switchable imbibition in nanoporous gold

    PubMed Central

    Xue, Yahui; Markmann, Jürgen; Duan, Huiling; Weissmüller, Jörg; Huber, Patrick

    2014-01-01

    Spontaneous imbibition enables the elegant propelling of nano-flows because of the dominance of capillarity at small length scales. The imbibition kinetics are, however, solely determined by the static host geometry, the capillarity, and the fluidity of the imbibed liquid. This makes active control particularly challenging. Here we show for aqueous electrolyte imbibition in nanoporous gold that the fluid flow can be reversibly switched on and off through electric potential control of the solid–liquid interfacial tension, that is, we can accelerate the imbibition front, stop it, and have it proceed at will. Simultaneous measurements of the mass flux and the electrical current allow us to document simple scaling laws for the imbibition kinetics, and to explore the charge transport in the metallic nanopores. Our findings demonstrate that the high electric conductivity along with the pathways for fluid/ionic transport render nanoporous gold a versatile, accurately controllable electrocapillary pump and flow sensor for minute amounts of liquids with exceptionally low operating voltages. PMID:24980062

  16. Switchable imbibition in nanoporous gold

    NASA Astrophysics Data System (ADS)

    Huber, Patrick; Markmann, Juergen; Duan, Huiling; Weissmueller, Joerg; Xue, Yahui

    2015-11-01

    Spontaneous imbibition enables the elegant propelling of nano-flows because of the dominance of capillarity at small length scales. The imbibition kinetics are, however, solely determined by the static host geometry, the capillarity, and the fluidity of the imbibed liquid. This makes active control particularly challenging. Here we show for aqueous electrolyte imbibition in nanoporous gold that the fluid flow can be reversibly switched on and off through electric potential control of the solid-liquid interfacial tension, that is, we can accelerate the imbibition front, stop it, and have it proceed at will. Simultaneous measurements of the mass flux and the electrical current allow us to document simple scaling laws for the imbibition kinetics, and to explore the charge transport in the metallic nanopores. Our findings demonstrate that the high electric conductivity along with the pathways for fluid/ionic transport render nanoporous gold a versatile, accurately controllable electrocapillary pump and flow sensor for minute amounts of liquids with exceptionally low operating voltages.

  17. Deformation Behavior of Nanoporous Metals

    SciTech Connect

    Biener, J; Hodge, A M; Hamza, A V

    2007-11-28

    Nanoporous open-cell foams are a rapidly growing class of high-porosity materials (porosity {ge} 70%). The research in this field is driven by the desire to create functional materials with unique physical, chemical and mechanical properties where the material properties emerge from both morphology and the material itself. An example is the development of nanoporous metallic materials for photonic and plasmonic applications which has recently attracted much interest. The general strategy is to take advantage of various size effects to introduce novel properties. These size effects arise from confinement of the material by pores and ligaments, and can range from electromagnetic resonances to length scale effects in plasticity. In this chapter we will focus on the mechanical properties of low density nanoporous metals and how these properties are affected by length scale effects and bonding characteristics. A thorough understanding of the mechanical behavior will open the door to further improve and fine-tune the mechanical properties of these sometimes very delicate materials, and thus will be crucial for integrating nanoporous metals into products. Cellular solids with pore sizes above 1 micron have been the subject of intense research for many years, and various scaling relations describing the mechanical properties have been developed.[4] In general, it has been found that the most important parameter in controlling their mechanical properties is the relative density, that is, the density of the foam divided by that of solid from which the foam is made. Other factors include the mechanical properties of the solid material and the foam morphology such as ligament shape and connectivity. The characteristic internal length scale of the structure as determined by pores and ligaments, on the other hand, usually has only little effect on the mechanical properties. This changes at the submicron length scale where the surface-to-volume ratio becomes large and the effect

  18. Regulating Current Rectification and Nanoparticle Transport Through a Salt Gradient in Bipolar Nanopores.

    PubMed

    Lin, Chih-Yuan; Yeh, Li-Hsien; Hsu, Jyh-Ping; Tseng, Shiojenn

    2015-09-16

    Tuning of ion and nanoparticle transport is validated through applying a salt gradient in two types of nanopores: the inner wall of a nanopore has bipolar charges and its outer wall neutral (type I), and both the inner and outer walls of a nanopore have bipolar charges (type II). The ion current rectification (ICR) behavior of these nanopores can be regulated by an applied salt gradient: if it is small, the degree of ICR in type II nanopore is more significant than that in type I nanopore; a reversed trend is observed at a sufficiently large salt gradient. If the applied salt gradient and electric field have the same direction, type I nanopore exhibits two significant features that are not observed in type II nanopore: (i) a cation-rich concentration polarization field and an enhanced funneling electric field are present near the cathode side of the nanopore, and (ii) the magnitude of the axial electric field inside the nanopore is reduced. These features imply that applying a salt gradient to type I nanopore is capable of simultaneously enhancing the nanoparticle capture into the nanopore and reducing its translocation velocity inside, so that high sensing performance and resolution can be achieved. PMID:26148458

  19. Periodicity of high-order neural functions

    NASA Technical Reports Server (NTRS)

    Kellaway, P.; Borda, R. P.; Frost, J. D.; Carrie, J. R. G.; Coats, A. C.

    1973-01-01

    The results of recent studies on higher order, integrative processes in the central nervous system are reported. Attempts were made to determine whether these processes exhibit any ongoing rhythmicity which might manifest itself in alterations of attention and alertness. Experiments were also designed to determine if a periodicity approximating that of the REM could be detected in various parameters of brain electrical activity.

  20. Monolithic aerogels with nanoporous crystalline phases

    NASA Astrophysics Data System (ADS)

    Daniel, Christophe; Guerra, Gaetano

    2015-05-01

    High porosity monolithic aerogels with nanoporous crystalline phases can be obtained from syndiotactic polystyrene and poly(2,6-dimethyl-1,4-phenylene)oxide thermoreversible gels by removing the solvent with supercritical CO2. The presence of crystalline nanopores in the aerogels based on these polymers allows a high uptake associated with a high selectivity of volatile organic compounds from vapor phase or aqueous solutions even at very low activities. The sorption and the fast kinetics make these materials particularly suitable as sorption medium to remove traces of pollutants from water and moist air.

  1. Water Purification across MoS2 Nano-porous Membranes

    NASA Astrophysics Data System (ADS)

    Heiranian, Mohammad; Barati Farimani, Amir; Aluru, Narayana R.

    2015-11-01

    A 2D material, molybdenum disulfide (MoS2) , is proposed as a nano-porous membrane for water desalination. By performing detailed molecular dynamics simulations, we find that salt ions are rejected efficiently across a single-layer MoS2 while water permeates at high rates. Depending on the pore area, which ranges from 20 to 60 Å2, the nanopore allows less than 12% of ions to pass through even at theoretically high pressures of 350 MPa. Water permeation across the MoS2 membrane is found to be as high as 12 L/cm2/day/MPa which is at least two orders of magnitude higher than that of other existing nano-porous membranes. Pore chemistry is shown to be one of the important factors leading to large water fluxes. MoS2 pore edges terminated with only molybdenum atoms result in higher fluxes which are about 70% higher than that of graphene nanopores. These findings are explained and supported by the permeation coefficients, energy barriers, water density and velocity distributions in the pores.

  2. Optical waveguides having flattened high order modes

    DOEpatents

    Messerly, Michael Joseph; Beach, Raymond John; Heebner, John Edward; Dawson, Jay Walter; Pax, Paul Henry

    2014-08-05

    A deterministic methodology is provided for designing optical fibers that support field-flattened, ring-like higher order modes. The effective and group indices of its modes can be tuned by adjusting the widths of the guide's field-flattened layers or the average index of certain groups of layers. The approach outlined here provides a path to designing fibers that simultaneously have large mode areas and large separations between the propagation constants of its modes.

  3. Structure-dependent water transport across nanopores of carbon nanotubes: toward selective gating upon temperature regulation.

    PubMed

    Zhao, Kuiwen; Wu, Huiying

    2015-04-28

    Determining water structure in nanopores and its influence on water transport behaviour is of great importance for understanding and regulating the transport across nanopores. Here we report an ultrafast-slow flow transition phenomenon for water transport across nanopores of carbon nanotubes owing to the change in water structure in nanopores induced by temperature. By performing extensive molecular dynamics simulations, we show the dependence of water transport behaviours on water structures. Our results indicate that owing to the change in water structure in nanopores, water flux across nanopores with certain pore sizes decreases sharply (nearly 3 orders of magnitude) with the decreasing temperature. This phenomenon is very sensitive to the pore size. The threshold temperatures for the occurrence of the ultrafast-slow flow transition for water transport are also determined for various pore sizes. These findings suggest a novel protocol for selective gating of water and proton conduction across nanopores and temperature-controlled drug release. PMID:25805425

  4. Single Nanoparticle Translocation Through Chemically Modified Solid Nanopore.

    PubMed

    Tan, Shengwei; Wang, Lei; Liu, Hang; Wu, Hongwen; Liu, Quanjun

    2016-12-01

    The nanopore sensor as a high-throughput and low-cost technology can detect single nanoparticle in solution. In the present study, the silicon nitride nanopores were fabricated by focused Ga ion beam (FIB), and the surface was functionalized with 3-aminopropyltriethoxysilane to change its surface charge density. The positively charged nanopore surface attracted negatively charged nanoparticles when they were in the vicinity of the nanopore. And, nanoparticle translocation speed was slowed down to obtain a clear and deterministic signal. Compared with previous studied small nanoparticles, the electrophoretic translocation of negatively charged polystyrene (PS) nanoparticles (diameter ~100 nm) was investigated in solution using the Coulter counter principle in which the time-dependent nanopore current was recorded as the nanoparticles were driven across the nanopore. A linear dependence was found between current drop and biased voltage. An exponentially decaying function (t d   ~ e (-v/v0) ) was found between the duration time and biased voltage. The interaction between the amine-functionalized nanopore wall and PS microspheres was discussed while translating PS microspheres. We explored also translocations of PS microspheres through amine-functionalized solid-state nanopores by varying the solution pH (5.4, 7.0, and 10.0) with 0.02 M potassium chloride (KCl). Surface functionalization showed to provide a useful step to fine-tune the surface property, which can selectively transport molecules or particles. This approach is likely to be applied to gene sequencing. PMID:26831688

  5. Single Nanoparticle Translocation Through Chemically Modified Solid Nanopore

    NASA Astrophysics Data System (ADS)

    Tan, Shengwei; Wang, Lei; Liu, Hang; Wu, Hongwen; Liu, Quanjun

    2016-02-01

    The nanopore sensor as a high-throughput and low-cost technology can detect single nanoparticle in solution. In the present study, the silicon nitride nanopores were fabricated by focused Ga ion beam (FIB), and the surface was functionalized with 3-aminopropyltriethoxysilane to change its surface charge density. The positively charged nanopore surface attracted negatively charged nanoparticles when they were in the vicinity of the nanopore. And, nanoparticle translocation speed was slowed down to obtain a clear and deterministic signal. Compared with previous studied small nanoparticles, the electrophoretic translocation of negatively charged polystyrene (PS) nanoparticles (diameter ~100 nm) was investigated in solution using the Coulter counter principle in which the time-dependent nanopore current was recorded as the nanoparticles were driven across the nanopore. A linear dependence was found between current drop and biased voltage. An exponentially decaying function ( t d ~ e -v/v0 ) was found between the duration time and biased voltage. The interaction between the amine-functionalized nanopore wall and PS microspheres was discussed while translating PS microspheres. We explored also translocations of PS microspheres through amine-functionalized solid-state nanopores by varying the solution pH (5.4, 7.0, and 10.0) with 0.02 M potassium chloride (KCl). Surface functionalization showed to provide a useful step to fine-tune the surface property, which can selectively transport molecules or particles. This approach is likely to be applied to gene sequencing.

  6. Nanopore analysis of amyloid fibrils formed by lysozyme aggregation.

    PubMed

    Martyushenko, Nikolay; Bell, Nicholas A W; Lamboll, Robin D; Keyser, Ulrich F

    2015-07-21

    The measurement of single particle size distributions of amyloid fibrils is crucial for determining mechanisms of growth and toxicity. Nanopore sensing is an attractive solution for this problem since it gives information on aggregates' shapes with relatively high throughput for a single particle technology. In this paper we study the translocation of lysozyme fibrils through quartz glass nanopores. We demonstrate that, under appropriate salt and pH conditions, lysozyme fibrils translocate through bare quartz nanopores without causing significant clogging. This enables us to measure statistics on tens of thousands of translocations of lysozyme fibrils with the same nanopore and track their development over a time course of aggregation spanning 24 h. Analysis of our events shows that the statistics are consistent with a simple bulk conductivity model for the passage of rods with a fixed cross sectional area through a conical glass nanopore. PMID:25994201

  7. Universal Scaling Law for the Collapse of Viscous Nanopores.

    PubMed

    Lu, Jiakai; Yu, Jiayun; Corvalan, Carlos M

    2015-08-11

    Below a threshold size, a small pore nucleated in a fluid sheet will contract to minimize the surface energy. Such behavior plays a key role in nature and technology, from nanopores in biological membranes to nanopores in sensors for rapid DNA and RNA sequencing. Here we show that nanopores nucleated in viscous fluid sheets collapse following a universal scaling law for the pore radius. High-fidelity numerical simulations reveal that the scaling is largely independent of the initial conditions, including the size, shape, and thickness of the original nanopore. Results further show that the scaling law yields a constant speed of collapse as observed in recent experiments. Nanopores in fluid sheets of moderate viscosity also attain this constant terminal speed provided that they are sufficiently close to the singularity. PMID:26230279

  8. Entropic cages for trapping DNA near a nanopore

    NASA Astrophysics Data System (ADS)

    Liu, Xu; Skanata, Mirna Mihovilovic; Stein, Derek

    2015-02-01

    Nanopores can probe the structure of biopolymers in solution; however, diffusion makes it difficult to study the same molecule for extended periods. Here we report devices that entropically trap single DNA molecules in a 6.2-femtolitre cage near a solid-state nanopore. We electrophoretically inject DNA molecules into the cage through the nanopore, pause for preset times and then drive the DNA back out through the nanopore. The saturating recapture time and high recapture probability after long pauses, their agreement with a convection-diffusion model and the observation of trapped DNA under fluorescence microscopy all confirm that the cage stably traps DNA. Meanwhile, the cages have 200 nm openings that make them permeable to small molecules, like the restriction endonuclease we use to sequence-specifically cut trapped DNA into fragments whose number and sizes are analysed upon exiting through the nanopore. Entropic cages thus serve as reactors for chemically modifying single DNA molecules.

  9. Nanopore Fabrication by Controlled Dielectric Breakdown

    PubMed Central

    Tabard-Cossa, Vincent

    2014-01-01

    Nanofabrication techniques for achieving dimensional control at the nanometer scale are generally equipment-intensive and time-consuming. The use of energetic beams of electrons or ions has placed the fabrication of nanopores in thin solid-state membranes within reach of some academic laboratories, yet these tools are not accessible to many researchers and are poorly suited for mass-production. Here we describe a fast and simple approach for fabricating a single nanopore down to 2-nm in size with sub-nm precision, directly in solution, by controlling dielectric breakdown at the nanoscale. The method relies on applying a voltage across an insulating membrane to generate a high electric field, while monitoring the induced leakage current. We show that nanopores fabricated by this method produce clear electrical signals from translocating DNA molecules. Considering the tremendous reduction in complexity and cost, we envision this fabrication strategy would not only benefit researchers from the physical and life sciences interested in gaining reliable access to solid-state nanopores, but may provide a path towards manufacturing of nanopore-based biotechnologies. PMID:24658537

  10. High-order control for symplectic maps

    NASA Astrophysics Data System (ADS)

    Sansottera, M.; Giorgilli, A.; Carletti, T.

    2016-02-01

    We revisit the problem of introducing an a priori control for devices that can be modeled via a symplectic map in a neighborhood of an elliptic equilibrium. Using a technique based on Lie transform methods we produce a normal form algorithm that avoids the usual step of interpolating the map with a flow. The formal algorithm is completed with quantitative estimates that bring into evidence the asymptotic character of the normal form transformation. Then we perform an heuristic analysis of the dynamical behavior of the map using the invariant function for the normalized map. Finally, we discuss how control terms of different orders may be introduced so as to increase the size of the stable domain of the map. The numerical examples are worked out on a two dimensional map of Hénon type.

  11. InGaN Light-Emitting Diodes with an Embedded Nanoporous GaN Distributed Bragg Reflectors.

    PubMed

    Shiu, Guo-Yi; Chen, Kuei-Ting; Fan, Feng-Hsu; Huang, Kun-Pin; Hsu, Wei-Ju; Dai, Jing-Jie; Lai, Chun-Feng; Lin, Chia-Feng

    2016-01-01

    InGaN light emitting diodes (LED) structure with an embedded 1/4λ-stack nanoporous-GaN/undoped-GaN distributed Bragg reflectors (DBR) structure have been demonstrated. Si-heavily doped GaN epitaxial layers (n(+)-GaN) in the 12-period n(+)-GaN/u-GaN stack structure are transformed into low refractive index nanoporous GaN structure through the doping-selective electrochemical wet etching process. The central wavelength of the nanoporous DBR structure was located at 442.3 nm with a 57 nm linewidth and a 97.1% peak reflectivity. The effective cavity length (6.0λ), the effective penetration depth (278 nm) in the nanoporous DBR structure, and InGaN active layer matching to Fabry-Pérot mode order 12 were observed in the far-field photoluminescence radiative spectra. High electroluminescence emission intensity and line-width narrowing effect were measured in the DBR-LED compared with the non-treated LED structure. Non-linear emission intensity and line-width reducing effect, from 11.8 nm to 0.73 nm, were observed by increasing the laser excited power. Resonant cavity effect was observed in the InGaN LED with bottom nanoporous-DBR and top GaN/air interface. PMID:27363290

  12. InGaN Light-Emitting Diodes with an Embedded Nanoporous GaN Distributed Bragg Reflectors

    NASA Astrophysics Data System (ADS)

    Shiu, Guo-Yi; Chen, Kuei-Ting; Fan, Feng-Hsu; Huang, Kun-Pin; Hsu, Wei-Ju; Dai, Jing-Jie; Lai, Chun-Feng; Lin, Chia-Feng

    2016-07-01

    InGaN light emitting diodes (LED) structure with an embedded 1/4λ-stack nanoporous-GaN/undoped-GaN distributed Bragg reflectors (DBR) structure have been demonstrated. Si-heavily doped GaN epitaxial layers (n+-GaN) in the 12-period n+-GaN/u-GaN stack structure are transformed into low refractive index nanoporous GaN structure through the doping-selective electrochemical wet etching process. The central wavelength of the nanoporous DBR structure was located at 442.3 nm with a 57 nm linewidth and a 97.1% peak reflectivity. The effective cavity length (6.0λ), the effective penetration depth (278 nm) in the nanoporous DBR structure, and InGaN active layer matching to Fabry-Pérot mode order 12 were observed in the far-field photoluminescence radiative spectra. High electroluminescence emission intensity and line-width narrowing effect were measured in the DBR-LED compared with the non-treated LED structure. Non-linear emission intensity and line-width reducing effect, from 11.8 nm to 0.73 nm, were observed by increasing the laser excited power. Resonant cavity effect was observed in the InGaN LED with bottom nanoporous-DBR and top GaN/air interface.

  13. InGaN Light-Emitting Diodes with an Embedded Nanoporous GaN Distributed Bragg Reflectors

    PubMed Central

    Shiu, Guo-Yi; Chen, Kuei-Ting; Fan, Feng-Hsu; Huang, Kun-Pin; Hsu, Wei-Ju; Dai, Jing-Jie; Lai, Chun-Feng; Lin, Chia-Feng

    2016-01-01

    InGaN light emitting diodes (LED) structure with an embedded 1/4λ-stack nanoporous-GaN/undoped-GaN distributed Bragg reflectors (DBR) structure have been demonstrated. Si-heavily doped GaN epitaxial layers (n+-GaN) in the 12-period n+-GaN/u-GaN stack structure are transformed into low refractive index nanoporous GaN structure through the doping-selective electrochemical wet etching process. The central wavelength of the nanoporous DBR structure was located at 442.3 nm with a 57 nm linewidth and a 97.1% peak reflectivity. The effective cavity length (6.0λ), the effective penetration depth (278 nm) in the nanoporous DBR structure, and InGaN active layer matching to Fabry-Pérot mode order 12 were observed in the far-field photoluminescence radiative spectra. High electroluminescence emission intensity and line-width narrowing effect were measured in the DBR-LED compared with the non-treated LED structure. Non-linear emission intensity and line-width reducing effect, from 11.8 nm to 0.73 nm, were observed by increasing the laser excited power. Resonant cavity effect was observed in the InGaN LED with bottom nanoporous-DBR and top GaN/air interface. PMID:27363290

  14. Fine-tuning the Size and Minimizing the Noise of Solid-state Nanopores

    PubMed Central

    Beamish, Eric; Kwok, Harold; Tabard-Cossa, Vincent; Godin, Michel

    2013-01-01

    Solid-state nanopores have emerged as a versatile tool for the characterization of single biomolecules such as nucleic acids and proteins1. However, the creation of a nanopore in a thin insulating membrane remains challenging. Fabrication methods involving specialized focused electron beam systems can produce well-defined nanopores, but yield of reliable and low-noise nanopores in commercially available membranes remains low2,3 and size control is nontrivial4,5. Here, the application of high electric fields to fine-tune the size of the nanopore while ensuring optimal low-noise performance is demonstrated. These short pulses of high electric field are used to produce a pristine electrical signal and allow for enlarging of nanopores with subnanometer precision upon prolonged exposure. This method is performed in situ in an aqueous environment using standard laboratory equipment, improving the yield and reproducibility of solid-state nanopore fabrication. PMID:24300128

  15. Large-scale low temperature fabrication of SnO2 hollow/nanoporous nanostructures: the template-engaged replacement reaction mechanism and high-rate lithium storage.

    PubMed

    Ding, Yuan-Li; Wen, Yuren; van Aken, Peter A; Maier, Joachim; Yu, Yan

    2014-10-01

    The morphology-controlled synthesis of SnO2 hollow/nanoporous nanostructures (nanotubes, urchin-like morphologies and nanospheres) was achieved via a template-engaged replacement reaction at a mild temperature (lower than 80 °C). The formation mechanism of hollow interior and nanoporous walls for the obtained SnO2 nanostructures (SnO2 nanotubes were used as an example) was investigated based on TEM and HRTEM observations during different reaction stages. It is found that bridge voids firstly form at the MnO2/SnO2 interface, followed by the inward development of voids before the MnO2 core is completely consumed. Two types of short-circuited galvanic cells, MnO2/Mn(2+)∣SnO2/Sn(2+) and concentration cell-SnO2/Sn(2+) (interior)∣SnO2/Sn(2+) (exterior), are probably responsible for the formation of SnO2 nanotubes and outward growth of SnO2 along MnO2. Moreover, the calculation result of the outer diameter of SnO2 nanotubes is in good agreement with the observation results by SEM and TEM. When evaluated as anodes for lithium ion batteries (LIBs), the three SnO2 nanostructures exhibit superior rate capability and cycling performance. Especially, SnO2 nanotubes present the best rate capability: specific capacities of above 800 mA h g(-1) at 200 mA g(-1) and about 500 mA h g(-1) at 4000 mA g(-1) were achieved, respectively. Importantly, the 1D morphology of SnO2 nanotubes can be well preserved after prolonged cycling at a relatively high current density, indicating good structural stability of the resulting nanotubes during the Li(+) insertion/extraction process. These results indicate that the obtained SnO2 hollow/nanoporous nanostructures would be promising anode materials for next-generation LIBs. PMID:25148613

  16. Nanoporous silicon oxide memory.

    PubMed

    Wang, Gunuk; Yang, Yang; Lee, Jae-Hwang; Abramova, Vera; Fei, Huilong; Ruan, Gedeng; Thomas, Edwin L; Tour, James M

    2014-08-13

    Oxide-based two-terminal resistive random access memory (RRAM) is considered one of the most promising candidates for next-generation nonvolatile memory. We introduce here a new RRAM memory structure employing a nanoporous (NP) silicon oxide (SiOx) material which enables unipolar switching through its internal vertical nanogap. Through the control of the stochastic filament formation at low voltage, the NP SiOx memory exhibited an extremely low electroforming voltage (∼ 1.6 V) and outstanding performance metrics. These include multibit storage ability (up to 9-bits), a high ON-OFF ratio (up to 10(7) A), a long high-temperature lifetime (≥ 10(4) s at 100 °C), excellent cycling endurance (≥ 10(5)), sub-50 ns switching speeds, and low power consumption (∼ 6 × 10(-5) W/bit). Also provided is the room temperature processability for versatile fabrication without any compliance current being needed during electroforming or switching operations. Taken together, these metrics in NP SiOx RRAM provide a route toward easily accessed nonvolatile memory applications. PMID:24992278

  17. Rapid nanopore discrimination between single polynucleotide molecules

    PubMed Central

    Meller, Amit; Nivon, Lucas; Brandin, Eric; Golovchenko, Jene; Branton, Daniel

    2000-01-01

    A variety of different DNA polymers were electrophoretically driven through the nanopore of an α-hemolysin channel in a lipid bilayer. Single-channel recording of the translocation duration and current flow during traversal of individual polynucleotides yielded a unique pattern of events for each of the several polymers tested. Statistical data derived from this pattern of events demonstrate that in several cases a nanopore can distinguish between polynucleotides of similar length and composition that differ only in sequence. Studies of temperature effects on the translocation process show that translocation duration scales as ∼T−2. A strong correlation exists between the temperature dependence of the event characteristics and the tendency of some polymers to form secondary structure. Because nanopores can rapidly discriminate and characterize unlabeled DNA molecules at low copy number, refinements of the experimental approach demonstrated here could eventually provide a low-cost high-throughput method of analyzing DNA polynucleotides. PMID:10655487

  18. Optical Properties of Nanoporous Germanium Thin Films.

    PubMed

    Cavalcoli, Daniela; Impellizzeri, Giuliana; Romano, Lucia; Miritello, Maria; Grimaldi, Maria Grazia; Fraboni, Beatrice

    2015-08-12

    In the present article we report enhanced light absorption, tunable size-dependent blue shift, and efficient electron-hole pairs generation in Ge nanoporous films (np-Ge) grown on Si. The Ge films are grown by sputtering and molecular beam epitaxy; subsequently, the nanoporous structure is obtained by Ge+ self-implantation. We show, by surface photovoltage spectroscopy measurements, blue shift of the optical energy gap and strong signal enhancement effects in the np-Ge films. The blue shift is related to quantum confinement effects at the wall separating the pore in the structure, the signal enhancement to multiple light-scattering events, which result in enhanced absorption. All these characteristics are highly stable with time. These findings demonstrate that nanoporous Ge films can be very promising for photovoltaic applications. PMID:26177652

  19. Molecular Sensing with Protein and Solid-State Nanopores

    NASA Astrophysics Data System (ADS)

    Niedzwiecki, David J.

    In the past 15 years nanopore sensing has proven to be a successful method for probing a variety of molecules of biological interest, such as DNA, RNA and proteins. Of particular appeal is this technique's ability to probe these molecules without the need for chemical modification or labeling, to do so at physiological conditions, and to probe single molecules at a time, allowing the possibility for results masked in bulk measurements to come to light. In this thesis these advantageous properties will be used in work on both a synthetic (solid-state) nanopore system and an engineered biological nanopore. I will describe the techniques for producing solid-state nanopores in thin membranes of silicon nitride and how these nanopores can be integrated into a fully functioning nanopore sensor system. I will then explore two applications of this system. First, a study of adsorption of bovine serum albumin (BSA), a protein found in blood serum, to the inorganic surface of nitride at the single molecule level. A simple physical model describing the behavior of this protein in the nanopore will be shown. Second, a study of the binding of the nucleocapsid protein of HIV-1 (NCp7) to three aptamers of different affinity, specifically three sequence 20mer mimics of the stem-loop 3 (SL3) RNA---the packaging domain of genomic RNA. Additionally, N-ethylmaleimide, which is known to inhibit the binding of NCp7 to a high-affinity SL3 RNA aptamer, will be used to demonstrate that the inhibition of the binding can be monitored in real time. Following these applications of the solid-state nanopore system, I will explore the geometry of a newly engineered biological nanopore, FhuA DeltaC/Delta4L, by using inert polymers to probe the nanopore interior.

  20. Advanced Solid State Nanopores Architectures: From Early Cancer Detection to Nano-electrochemistry

    NASA Astrophysics Data System (ADS)

    Bashir, Rashid

    2013-03-01

    Solid-state nanopores (ssNPs) are potentially low-cost and highly scalable technologies for rapid and reliable se-quencing of the human diploid genome for under 1,000. The ssNPs detect ionic current changes while molecules translocate through the pore. Several key challenges must be overcome in order for ssNPs to become ubiquitous in the fields of medical diagnostics and personalized healthcare. One major challenge is to reduce the speed at which DNA translocates through the nanopore from microseconds to milliseconds per nucleotide, enabling reliable identification of single nucleotides. The other major challenge is to improve the sensitivity of the approach requiring new sensing modalities and novel device architectures. In this paper, we review our recent efforts to (i) develop ssNPs for early cancer detection, (ii) to embed graphene electrodes in dielectric nanolaminates to form 3 and 4 terminal nanopore devices, and (iii) we demonstrate a nanopore based structure consisting of stacked graphene and Al2O3 dielectric layers to study electrochemical activity at graphene edges. The electrochemical signal corresponding to the atomically thin graphene layer could also provide a pathway to DNA sequencing. Supported by National Institute of Health.

  1. Optical observation of DNA translocation through Al2O3 sputtered silicon nanopores in porous membrane

    NASA Astrophysics Data System (ADS)

    Yamazaki, Hirohito; Ito, Shintaro; Esashika, Keiko; Taguchi, Yoshihiro; Saiki, Toshiharu

    2016-03-01

    Nanopore sensors are being developed as a platform for analyzing single DNA, RNA, and protein. In nanopore sensors, ionic current measurement is widely used and proof-of-concept of nanopore DNA sequencing by it has been demonstrated by previous studies. Recently, we proposed an alternative platform of nanopore DNA sequencing that incorporates ultraviolet light and porous silicon membrane to perform high-throughput measurement. In the development of our DNA sequencing platform, controlling nanopore size in porous silicon membrane is essential but remains a challenge. Here, we report on observation of DNA translocation through Al2O3 sputtered silicon nanopores (Al2O3 nanopores) by our optical scheme. Electromagnetic wave simulation was performed to analyze the excitation volume on Al2O3 nanopores generated by focused ultraviolet light. In the experiment, DNA translocation time through Al2O3 nanopores was compared with that of silicon nanopores and we examined the effect of nanopore density and thickness of membrane by supplementing the static electric field simulation.

  2. Nanopore Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Bush, Joseph; Mihovilovic, Mirna; Maulbetsch, William; Frenchette, Layne; Moon, Wooyoung; Pruitt, Cole; Bazemore-Walker, Carthene; Weber, Peter; Stein, Derek

    2013-03-01

    We report on the design, construction, and characterization of a nanopore-based ion source for mass spectrometry. Our goal is to field-extract ions directly from solution into the high vacuum to enable unit collection efficiency and temporal resolution of sequential ion emissions for DNA sequencing. The ion source features a capillary whose tip, measuring tens to hundreds of nanometers in inner diameter, is situated in the vacuum ~ 1.5 cm away from an extractor electrode. The capillary was filled with conductive solution and voltage-biased relative to the extractor. Applied voltages of hundreds of volts extracted tens to hundreds of nA of current from the tip. A mass analysis of the extracted ions showed primarily singly charged clusters comprising the cation or anion solvated by several solvent molecules. Our interpretation of these results, based on the works of Taylor and of de la Mora, is that the applied electric stresses distort the fluid meniscus into a Taylor cone, where electric fields reach ~ 1V/nm and induce significant ion evaporation. Accordingly, the abundances of extracted ionic clusters resemble a Boltzmann distribution. This work was supported by NIH grant NHGRI 1R21HG005100-01.

  3. Nanoporous microscale microbial incubators.

    PubMed

    Ge, Zhifei; Girguis, Peter R; Buie, Cullen R

    2016-02-01

    Reconstruction of phylogenetic trees based on 16S rRNA gene sequencing reveals abundant microbial diversity that has not been cultured in the laboratory. Many attribute this so-called 'great plate count anomaly' to traditional microbial cultivation techniques, which largely facilitate the growth of a single species. Yet, it is widely recognized that bacteria in nature exist in complex communities. One technique to increase the pool of cultivated bacterial species is to co-culture multiple species in a simulated natural environment. Here, we present nanoporous microscale microbial incubators (NMMI) that enable high-throughput screening and real-time observation of multi-species co-culture. The key innovation in NMMI is that they facilitate inter-species communication while maintaining physical isolation between species, which is ideal for genomic analysis. Co-culture of a quorum sensing pair demonstrates that the NMMI can be used to culture multiple species in chemical communication while monitoring the growth dynamics of individual species. PMID:26584739

  4. Large-scale low temperature fabrication of SnO2 hollow/nanoporous nanostructures: the template-engaged replacement reaction mechanism and high-rate lithium storage

    NASA Astrophysics Data System (ADS)

    Ding, Yuan-Li; Wen, Yuren; van Aken, Peter A.; Maier, Joachim; Yu, Yan

    2014-09-01

    The morphology-controlled synthesis of SnO2 hollow/nanoporous nanostructures (nanotubes, urchin-like morphologies and nanospheres) was achieved via a template-engaged replacement reaction at a mild temperature (lower than 80 °C). The formation mechanism of hollow interior and nanoporous walls for the obtained SnO2 nanostructures (SnO2 nanotubes were used as an example) was investigated based on TEM and HRTEM observations during different reaction stages. It is found that bridge voids firstly form at the MnO2/SnO2 interface, followed by the inward development of voids before the MnO2 core is completely consumed. Two types of short-circuited galvanic cells, MnO2/Mn2+|SnO2/Sn2+ and concentration cell-SnO2/Sn2+ (interior)|SnO2/Sn2+ (exterior), are probably responsible for the formation of SnO2 nanotubes and outward growth of SnO2 along MnO2. Moreover, the calculation result of the outer diameter of SnO2 nanotubes is in good agreement with the observation results by SEM and TEM. When evaluated as anodes for lithium ion batteries (LIBs), the three SnO2 nanostructures exhibit superior rate capability and cycling performance. Especially, SnO2 nanotubes present the best rate capability: specific capacities of above 800 mA h g-1 at 200 mA g-1 and about 500 mA h g-1 at 4000 mA g-1 were achieved, respectively. Importantly, the 1D morphology of SnO2 nanotubes can be well preserved after prolonged cycling at a relatively high current density, indicating good structural stability of the resulting nanotubes during the Li+ insertion/extraction process. These results indicate that the obtained SnO2 hollow/nanoporous nanostructures would be promising anode materials for next-generation LIBs.The morphology-controlled synthesis of SnO2 hollow/nanoporous nanostructures (nanotubes, urchin-like morphologies and nanospheres) was achieved via a template-engaged replacement reaction at a mild temperature (lower than 80 °C). The formation mechanism of hollow interior and nanoporous walls

  5. High-Resolution Size-Discrimination of Single Nonionic Synthetic Polymers with a Highly Charged Biological Nanopore.

    PubMed

    Baaken, Gerhard; Halimeh, Ibrahim; Bacri, Laurent; Pelta, Juan; Oukhaled, Abdelghani; Behrends, Jan C

    2015-06-23

    Electrophysiological studies of the interaction of polymers with pores formed by bacterial toxins (1) provide a window on single molecule interaction with proteins in real time, (2) report on the behavior of macromolecules in confinement, and (3) enable label-free single molecule sensing. Using pores formed by the staphylococcal toxin α-hemolysin (aHL), a particularly pertinent observation was that, under high salt conditions (3-4 M KCl), the current through the pore is blocked for periods of hundreds of microseconds to milliseconds by poly(ethylene glycol) (PEG) oligomers (degree of polymerization approximately 10-60). Notably, this block showed monomeric sensitivity on the degree of polymerization of individual oligomers, allowing the construction of size or mass spectra from the residual current values. Here, we show that the current through the pore formed by aerolysin (AeL) from Aeromonas hydrophila is also blocked by PEG but with drastic differences in the voltage-dependence of the interaction. In contrast to aHL, AeL strongly binds PEG at high transmembrane voltages. This fact, which is likely related to AeL's highly charged pore wall, allows discrimination of polymer sizes with particularly high resolution. Multiple applications are now conceivable with this pore to screen various nonionic or charged polymers. PMID:26028280

  6. Nanopore sequencing detects structural variants in cancer.

    PubMed

    Norris, Alexis L; Workman, Rachael E; Fan, Yunfan; Eshleman, James R; Timp, Winston

    2016-03-01

    Despite advances in sequencing, structural variants (SVs) remain difficult to reliably detect due to the short read length (<300 bp) of 2nd generation sequencing. Not only do the reads (or paired-end reads) need to straddle a breakpoint, but repetitive elements often lead to ambiguities in the alignment of short reads. We propose to use the long-reads (up to 20 kb) possible with 3rd generation sequencing, specifically nanopore sequencing on the MinION. Nanopore sequencing relies on a similar concept to a Coulter counter, reading the DNA sequence from the change in electrical current resulting from a DNA strand being forced through a nanometer-sized pore embedded in a membrane. Though nanopore sequencing currently has a relatively high mismatch rate that precludes base substitution and small frameshift mutation detection, its accuracy is sufficient for SV detection because of its long reads. In fact, long reads in some cases may improve SV detection efficiency. We have tested nanopore sequencing to detect a series of well-characterized SVs, including large deletions, inversions, and translocations that inactivate the CDKN2A/p16 and SMAD4/DPC4 tumor suppressor genes in pancreatic cancer. Using PCR amplicon mixes, we have demonstrated that nanopore sequencing can detect large deletions, translocations and inversions at dilutions as low as 1:100, with as few as 500 reads per sample. Given the speed, small footprint, and low capital cost, nanopore sequencing could become the ideal tool for the low-level detection of cancer-associated SVs needed for molecular relapse, early detection, or therapeutic monitoring. PMID:26787508

  7. Nanopore sequencing detects structural variants in cancer

    PubMed Central

    Norris, Alexis L.; Workman, Rachael E.; Fan, Yunfan; Eshleman, James R.; Timp, Winston

    2016-01-01

    ABSTRACT Despite advances in sequencing, structural variants (SVs) remain difficult to reliably detect due to the short read length (<300 bp) of 2nd generation sequencing. Not only do the reads (or paired-end reads) need to straddle a breakpoint, but repetitive elements often lead to ambiguities in the alignment of short reads. We propose to use the long-reads (up to 20 kb) possible with 3rd generation sequencing, specifically nanopore sequencing on the MinION. Nanopore sequencing relies on a similar concept to a Coulter counter, reading the DNA sequence from the change in electrical current resulting from a DNA strand being forced through a nanometer-sized pore embedded in a membrane. Though nanopore sequencing currently has a relatively high mismatch rate that precludes base substitution and small frameshift mutation detection, its accuracy is sufficient for SV detection because of its long reads. In fact, long reads in some cases may improve SV detection efficiency. We have tested nanopore sequencing to detect a series of well-characterized SVs, including large deletions, inversions, and translocations that inactivate the CDKN2A/p16 and SMAD4/DPC4 tumor suppressor genes in pancreatic cancer. Using PCR amplicon mixes, we have demonstrated that nanopore sequencing can detect large deletions, translocations and inversions at dilutions as low as 1:100, with as few as 500 reads per sample. Given the speed, small footprint, and low capital cost, nanopore sequencing could become the ideal tool for the low-level detection of cancer-associated SVs needed for molecular relapse, early detection, or therapeutic monitoring. PMID:26787508

  8. Fluorescence biosensing in nanopores.

    PubMed

    Karolin, Jan; Pánek, Dalibor; MacMillan, Alexander; Rolinski, Olaf; Birch, David

    2009-01-01

    Hydrated nanopores offer a unique environment for studying biological molecules under controlled conditions and fabricating sensors using fluorescence. Silica nanopores for example are non-toxic, biologically and optically compatible with protein, and can be easily synthesized to entrap protein and exclude potentially interfering macromolecules, while transmitting analytes of interest. A well known problem when polymerizing orthosilicates to fabricate silica sol-gel nanopores is the release of alcohol, which denatures proteins. We will describe how using the fluorescence of PRODAN (6-propionyl-2-(N,N-dimethylamino) naphthalene) to monitor methanol generated during polymerization has helped define a protocol with enhanced biocompatibility. The improved biocompatibility of sol-gel nanopores synthesized using tetramethyl orthosilicate (TMOS) has been demonstrated by preserving the unstable native trimer form of allophycocyanin (APC) for up to 500 Hrs without the need to covalently binding the subunits together. This has enabled the observation of native APC trimer by means of its fluorescence in a pore down to the single molecule level. In this paper we demonstrate how PRODAN and another polarity sensitive dye, 9-diethylamino-5H-benzo[alpha]phenoxazine-5-one, Nile red (NR) report on pore polarity and successfully extend protein encapsulation to nano-channels of alumina (Al2O3). Improved biocompatibility of nanopores has potential impact in nanomedicine where the ability to study single biomolecules is a primary goal as it underpins our understanding of disease pathology and therapeutics at the most fundamental level. In sensing also the advantages of nanopore isolation of metabolite-specific protein for detecting non-fluorescent metabolites has been demonstrated. Similar approaches can in principle be developed for both single-molecules and lab-on-a-chip sensors. PMID:19964618

  9. Cell encapsulation and oxygenation in nanoporous microcontainers

    PubMed Central

    Kwon, Joonbum; Liu, Li; Su, Yang; Nemani, Krishnamurthy; Trivedi, Krutarth; Cui, Yonghao; Vachha, Behroze; Mason, Ralph; Hu, Wenchuang; Lee, Jeong-Bong

    2010-01-01

    With strides in stem cell biology, cell engineering and molecular therapy, the transplantation of cells to produce therapeutic molecules endogenously is an attractive and achievable alternative to the use of exogenous drugs. The encapsulation of such cell transplants in semi-permeable, nanoporous constructs is often required to protect them from immune attack and to prevent their proliferation in the host. However, effective graft immunoisolation has been mostly elusive owing to the absence of a high-throughput method to create precisely controlled, high-aspect-ratio nanopores. To address the clinical need for effective cell encapsulation and immunoisolation, we devised a biocompatible cell-encapsulating microcontainer and a method to create highly anisotropic nanopores in the micro-container’s surface. To evaluate the efficacy of these nanopores in oxygenating the encapsulated cells, we engineered 9L rat glioma cells to bioluminesce under hypoxic conditions. The methods described above should aid in evaluating the long term survival and efficacy of cellular grafts. PMID:19629700

  10. Synthesis of nanoporous material from zeolite USY and catalytic application to bio-oil conversion.

    PubMed

    Park, Hyun Ju; Jeon, Jong-Ki; Kim, Ji Man; Lee, Hyung Ik; Yim, Jin-Heong; Park, Junhong; Park, Young-Kwon

    2008-10-01

    A highly ordered nanoporous aluminosilicate (MMZ(USY)) was synthesized using commercially available zeolite USY as the framework source and cetyltrimethylammonium bromide as the template. The aluminosilicate was characterized by XRD, N2 adsorption, ICP-AES and TPD. The catalytic performance of the MMZ(USY) material in the conversion of bio-oil was compared with that of Al-MCM-41, which was synthesized using a direct sol-gel method. The highly accessible nanopores, hydrothermal stability and the intermediate acidic properties of MMZ(USY) correlated with the catalytic performance in the conversion of the bio-oil. The MMZ(USY) used in this study showed excellent activity, selectivity and stability for the production of desirable organic compounds, such as phenolics, with a high degree of deoxygenation. PMID:19198472

  11. Slow DNA Transport through Nanopores in Hafnium Oxide Membranes

    PubMed Central

    Bell, David C.; Cohen-Karni, Tzahi; Rosenstein, Jacob K.; Wanunu, Meni

    2016-01-01

    We present a study of double- and single-stranded DNA transport through nanopores fabricated in ultrathin (2–7 nm thick) free-standing hafnium oxide (HfO2) membranes. The high chemical stability of ultrathin HfO2 enables long-lived experiments with <2 nm diameter pores that last several hours, in which we observe >50 000 DNA translocations with no detectable pore expansion. Mean DNA velocities are slower than velocities through comparable silicon nitride pores, providing evidence that HfO2 nanopores have favorable physicochemical interactions with nucleic acids that can be leveraged to slow down DNA in a nanopore. PMID:24083444

  12. 3D nanoporous gold scaffold supported on graphene paper: Freestanding and flexible electrode with high loading of ultrafine PtCo alloy nanoparticles for electrochemical glucose sensing.

    PubMed

    Zhao, Anshun; Zhang, Zhaowei; Zhang, Penghui; Xiao, Shuang; Wang, Lu; Dong, Yue; Yuan, Hao; Li, Peiwu; Sun, Yimin; Jiang, Xueliang; Xiao, Fei

    2016-09-28

    Recent advances in on-body wearable medical apparatus and implantable devices drive the development of light-weight and bendable electrochemical sensors, which require the design of high-performance flexible electrode system. In this work, we reported a new type of freestanding and flexible electrode based on graphene paper (GP) supported 3D monolithic nanoporous gold (NPG) scaffold (NPG/GP), which was further modified by a layer of highly dense, well dispersed and ultrafine binary PtCo alloy nanoparticles via a facile and effective ultrasonic electrodeposition method. Our results demonstrated that benefited from the synergistic effect of the electrocatalytically active PtCo alloy nanoparticles, the large-active-area and highly conductive 3D NPG scaffold, and the mechanically strong and stable GP electrode substrate, the resultant PtCo alloy nanoparticles modified NPG/GP (PtCo/NPG/GP) exhibited high mechanical strength and good electrochemical sensing performances toward nonenzymatic detection of glucose, including a wide linear range from 35 μM- to 30 mM, a low detection limit of 5 μM (S/N = 3) and a high sensitivity of 7.84 μA cm(-2) mM(-1) as well as good selectivity, long-term stability and reproducibility. The practical application of the proposed PtCo/NPG/GP has also been demonstrated in in vitro detection of blood glucose in real clinic samples. PMID:27619087

  13. Development of high performance nano-porous polyethersulfone ultrafiltration membranes with hydrophilic surface and superior antifouling properties

    NASA Astrophysics Data System (ADS)

    Rahimpour, Ahmad; Madaeni, Sayed Siavash; Jahanshahi, Mohsen; Mansourpanah, Yaghoub; Mortazavian, Narmin

    2009-08-01

    Hydrophilic nano-porous polyethersulfone ultrafiltration membranes were developed for milk concentration. The membranes were prepared from new dope solution containing polyethersulfone (PES)/polyvinylpirrolidone (PVP)/polyethyleneglycole (PEG)/cellulose acetate phthalate (CAP)/acrylic acid/Triton X-100 using phase inversion induced by immersion precipitation technique. This casting solution leads to formation of new hydrophilic membranes. The morphological studies were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). In addition, the hydrophilicity and performance of membranes were examined by contact angel measurements and cross-flow filtration (pure water flux, milk water permeation, protein rejection and antifouling measurements). The contact angle measurements indicate that a surface with superior hydrophilicity was obtained for PES membranes. Two concentrations of PES (16 and 14.4 wt.%) and two different non-solvents (pure water and mixtures of water and IPA) were used for preparation of membranes. The morphological studies showed that the higher concentration of PES and the presence of IPA in the gelation media results in formation of a membrane with a dense top and sub-layer with small pores on the surface. The pure water flux of membranes was decreased when higher polymer concentration and mixtures of water and IPA were employed for membrane formation. On the other hand, the milk water permeation and protein rejection were increased using mixtures of water and IPA as non-solvent. Furthermore, the fouling analysis of the membranes demonstrated that the membrane surface with fewer tendencies for fouling was obtained.

  14. Mechanical Properties and Fracture Behavior of Nanoporous Au

    SciTech Connect

    Biener, J; Hodge, A M; Wang, Y M; Hayes, J R; Hamza, A V

    2005-06-16

    Nanoporous metals have recently attracted considerable interest fueled by potential sensor and actuator applications. From a material science point of view, one of the key issues in this context is the synthesis of nanoporous metals with both high tensile and compressive strength. Nanoporous gold (np-Au) has been suggested as a candidate material for this application due to its monolithic character. The material can be synthesized by electrochemically-driven dealloying of Ag-Au alloys, and exhibits an open sponge-like structure of interconnecting ligaments with a typical pore size distribution on the nanometer length scale. However, besides the observation of a ductile-brittle transition very little is known about the mechanical behavior of this material. Here, we present our results regarding the mechanical properties and the fracture behavior of np-Au. Depth-sensing nanoindentation reveals that the yield strength of np-Au is almost one order of magnitude higher than the value predicted by scaling laws developed for macroscopic open-cell foams. The unexpectedly high value of the yield strength indicates the presence of a distinct size effect of the mechanical properties due to the sub-micron dimensions of the ligaments, thus potentially opening a door to a new class of high yield strength--low density materials. The failure mechanism of np-Au under tensile stress was evaluated by microscopic examination of fracture surfaces using scanning electron microscopy. On a macroscopic level, np-Au is a very brittle material. However, microscopically np-Au is very ductile as ligaments strained by as much as 200% can be observed in the vicinity of crack tips. Cell-size effects on the microscopic failure mechanism were studied by annealing experiments whereby increasing the typical pore size/ligament diameter from {approx}100 nm to {approx}1{micro}m.

  15. Nanoparticle size and shape characterization with Solid State Nanopores

    NASA Astrophysics Data System (ADS)

    Nandivada, Santoshi; Benamara, Mourad; Li, Jiali

    2015-03-01

    Solid State Nanopores are widely used in a variety of single molecule studies including DNA and biomolecule detection based on the principle of Resistive Pulse technique. This technique is based on electrophoretically driving charged particles through 35-60 nm solid state nanopores. The translocation of these particles produces current blockage events that provide an insight to the properties of the translocation particles and the nanopore. In this work we study the current blockage events produced by ~ 30nm negatively charged PS nanoparticles through Silicon Nitride solid state nanopores. We show how the current blockage amplitudes and durations are related to the ratio of the volume of the particle to the volume of the pore, the shape of the particle, charge of the particle and the nanopore surface, salt concentration, solution pH, and applied voltage. The solid-state nanopores are fabricated by a combination of Focus Ion Beam and low energy Ion beams in silicon nitride membranes. High resolution TEM is used to measure the 3D geometry of the nanopores and a finite element analysis program (COMSOL) is used to simulate the experimental results.

  16. On the importance of a precise crystal structure for simulating gas adsorption in nanoporous materials.

    PubMed

    Lawler, Keith V; Hulvey, Zeric; Forster, Paul M

    2015-07-15

    We show that simulation of gas adsorption in nanoporous sorbents may be highly sensitive to accurate crystallographic coordinates, even for frameworks anticipated to have low flexibility. PMID:26133672

  17. Stabilization of graphene nanopore

    PubMed Central

    Lee, Jaekwang; Yang, Zhiqing; Zhou, Wu; Pennycook, Stephen J.; Pantelides, Sokrates T.; Chisholm, Matthew F.

    2014-01-01

    Graphene is an ultrathin, impervious membrane. The controlled introduction of nanoscale pores in graphene would lead to applications that involve water purification, chemical separation, and DNA sequencing. However, graphene nanopores are unstable against filling by carbon adatoms. Here, using aberration-corrected scanning transmission electron microscopy and density-functional calculations, we report that Si atoms stabilize graphene nanopores by bridging the dangling bonds around the perimeter of the hole. Si‐passivated pores remain intact even under intense electron beam irradiation, and they were observed several months after the sample fabrication, demonstrating that these structures are intrinsically robust and stable against carbon filling. Theoretical calculations reveal the underlying mechanism for this stabilization effect: Si atoms bond strongly to the graphene edge, and their preference for tetrahedral coordination forces C adatoms to form dendrites sticking out of the graphene plane, instead of filling the nanopore. Our results provide a novel way to develop stable nanopores, which is a major step toward reliable graphene-based molecular translocation devices. PMID:24821802

  18. Stabilization of graphene nanopore

    SciTech Connect

    Lee, Jaekwang; Yang, Zhiqing; Zhou, Wu; Pennycook, Stephen J.; Pantelides, Sokrates T.; Chisholm, Matthew F.

    2014-05-27

    Graphene is an ultrathin, impervious membrane. The controlled introduction of nanoscale pores in graphene would lead to applications that involve water purification, chemical separation, and DNA sequencing. However, graphene nanopores are unstable against filling by carbon adatoms. Using aberration-corrected scanning transmission electron microscopy and density-functional calculations, we report that Si atoms stabilize graphene nanopores by bridging the dangling bonds around the perimeter of the hole. Si-passivated pores remain intact even under intense electron beam irradiation, and they were observed several months after the sample fabrication, demonstrating that these structures are intrinsically robust and stable against carbon filling. Theoretical calculations reveal the underlying mechanism for this stabilization effect: Si atoms bond strongly to the graphene edge, and their preference for tetrahedral coordination forces C adatoms to form dendrites sticking out of the graphene plane, instead of filling the nanopore. Our results provide a novel way to develop stable nanopores, which is a major step toward reliable graphene-based molecular translocation devices.

  19. Multichannel detection of ionic currents through two nanopores fabricated on integrated Si3N4 membranes.

    PubMed

    Yanagi, Itaru; Akahori, Rena; Aoki, Mayu; Harada, Kunio; Takeda, Ken-Ichi

    2016-08-16

    Integration of solid-state nanopores and multichannel detection of signals from each nanopore are effective measures for realizing high-throughput nanopore sensors. In the present study, we demonstrated fabrication of Si3N4 membrane arrays and the simultaneous measurement of ionic currents through two nanopores formed in two adjacent membranes. Membranes with thicknesses as low as 6.4 nm and small nanopores with diameters of less than 2 nm could be fabricated using the poly-Si sacrificial-layer process and multilevel pulse-voltage injection. Using the fabricated nanopore membranes, we successfully achieved simultaneous detection of clear ionic-current blockades when single-stranded short homopolymers (poly(dA)60) passed through two nanopores. In addition, we investigated the signal crosstalk and leakage current among separated chambers. When two nanopores were isolated on the front surface of the membrane, there was no signal crosstalk or leakage current between the chambers. However, when two nanopores were isolated on the backside of the Si substrate, signal crosstalk and leakage current were observed owing to high-capacitance coupling between the chambers and electrolysis of water on the surface of the Si substrate. The signal crosstalk and leakage current could be suppressed by oxidizing the exposed Si surface in the membrane chip. Finally, the observed ionic-current blockade when poly(dA)60 passed through the nanopore in the oxidized chip was approximately half of that observed in the non-oxidized chip. PMID:27440476

  20. A novel hierarchically structured and highly hydrophilic poly(vinyl alcohol-co-ethylene)/poly(ethylene terephthalate) nanoporous membrane for lithium-ion battery separator

    NASA Astrophysics Data System (ADS)

    Xia, Ming; Liu, Qiongzhen; Zhou, Zhou; Tao, Yifei; Li, MuFang; Liu, Ke; Wu, Zhihong; Wang, Dong

    2014-11-01

    A novel hierarchically structured and highly hydrophilic poly(vinyl alcohol-co-ethylene)/poly(ethylene terephthalate) nanoporous separator (referred to NFs/PET/NFs) composed of a poly(ethylene terephthalate) (PET) nonwoven sandwiched between two interconnected poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibrous membranes is successfully developed for lithium-ion battery. Systematical investigations including structural characterization, porosity measurement, water contact angle testing, electrolyte uptake, and thermal shrinkage testing demonstrate that the notable feature of this NFs/PET/NFs nanofibrous separator is an electrolyte-philic, highly porous and hierarchically nanoscaled structure, thus resulting in superior electrolyte wettability, lower thermal shrinkage, and higher ion conductivity, in comparison to the commercial Polypropylene (PP) separator. These structural characteristics enable the NFs/PET/NFs separator to offer an excellent cell performance including outstanding C-rate capability, high capacity and excellent cycling performance. This suggests that the NFs/PET/NFs separator is a promising material for practical application in lithium-ion battery due to it low cost production and high performance.

  1. Film Growth on Nanoporous Substrate

    NASA Astrophysics Data System (ADS)

    Zhang, Xue; Joy, James; Zhao, Chenwei; Xu, J. M.; Valles, James

    Self-ordered nanoporous anodic aluminum oxide (AAO) provides an easy way to fabricate nano structured material, such as nano wires and nano particles. We employ AAO as substrates and focus on the thermally evaporated film growth on the surface of the substrate. With various materials deposited onto the substrate, we find the films show different structures, e,g. ordered array of nano particles for Lead and nanohoneycomb structure for Silver. We relate the differing behaviors to the difference of surface energy and diffusion constant. To verify this, the effect of substrate temperature on the film growth has been explored and the structure of the film has been successfully changed through the process. We are grateful for the support of NSF Grants No. DMR-1307290.

  2. High-order correlation of chaotic bosons and fermions

    NASA Astrophysics Data System (ADS)

    Liu, Hong-Chao

    2016-08-01

    We theoretically study the high-order correlation functions of chaotic bosons and fermions. Based on the different parity of the Stirling number, the products of the first-order correlation functions are well classified and employed to represent the high-order correlation function. The correlation of bosons conduces a bunching effect, which will be enhanced as order N increases. Different from bosons, the anticommutation relation of fermions leads to the parity of the Stirling number, which thereby results in a mixture of bunching and antibunching behaviors in high-order correlation. By further investigating third-order ghost diffraction and ghost imaging, the differences between the high-order correlations of bosons and fermions are discussed in detail. A larger N will dramatically improve the ghost image quality for bosons, but a good strategy should be carefully chosen for the fermionic ghost imaging process due to its complex correlation components.

  3. Electrochemical Reaction in Single Layer MoS2: Nanopores Opened Atom by Atom.

    PubMed

    Feng, J; Liu, K; Graf, M; Lihter, M; Bulushev, R D; Dumcenco, D; Alexander, D T L; Krasnozhon, D; Vuletic, T; Kis, A; Radenovic, A

    2015-05-13

    Ultrathin nanopore membranes based on 2D materials have demonstrated ultimate resolution toward DNA sequencing. Among them, molybdenum disulfide (MoS2) shows long-term stability as well as superior sensitivity enabling high throughput performance. The traditional method of fabricating nanopores with nanometer precision is based on the use of focused electron beams in transmission electron microscope (TEM). This nanopore fabrication process is time-consuming, expensive, not scalable, and hard to control below 1 nm. Here, we exploited the electrochemical activity of MoS2 and developed a convenient and scalable method to controllably make nanopores in single-layer MoS2 with subnanometer precision using electrochemical reaction (ECR). The electrochemical reaction on the surface of single-layer MoS2 is initiated at the location of defects or single atom vacancy, followed by the successive removals of individual atoms or unit cells from single-layer MoS2 lattice and finally formation of a nanopore. Step-like features in the ionic current through the growing nanopore provide direct feedback on the nanopore size inferred from a widely used conductance vs pore size model. Furthermore, DNA translocations can be detected in situ when as-fabricated MoS2 nanopores are used. The atomic resolution and accessibility of this approach paves the way for mass production of nanopores in 2D membranes for potential solid-state nanopore sequencing. PMID:25928894

  4. Voltage-Gated Hydrophobic Nanopores

    SciTech Connect

    Lavrik, Nickolay V

    2011-01-01

    Hydrophobicity is a fundamental property that is responsible for numerous physical and biophysical aspects of molecular interactions in water. Peculiar behavior is expected for water in the vicinity of hydrophobic structures, such as nanopores. Indeed, hydrophobic nanopores can be found in two distinct states, dry and wet, even though the latter is thermodynamically unstable. Transitions between these two states are kinetically hindered in long pores but can be much faster in shorter pores. As it is demonstrated for the first time in this paper, these transitions can be induced by applying a voltage across a membrane with a single hydrophobic nanopore. Such voltage-induced gating in single nanopores can be realized in a reversible manner through electrowetting of inner walls of the nanopores. The resulting I-V curves of such artificial hydrophobic nanopores mimic biological voltage-gated channels.

  5. Nanopore fabrication and characterization by helium ion microscopy

    NASA Astrophysics Data System (ADS)

    Emmrich, D.; Beyer, A.; Nadzeyka, A.; Bauerdick, S.; Meyer, J. C.; Kotakoski, J.; Gölzhäuser, A.

    2016-04-01

    The Helium Ion Microscope (HIM) has the capability to image small features with a resolution down to 0.35 nm due to its highly focused gas field ionization source and its small beam-sample interaction volume. In this work, the focused helium ion beam of a HIM is utilized to create nanopores with diameters down to 1.3 nm. It will be demonstrated that nanopores can be milled into silicon nitride, carbon nanomembranes, and graphene with well-defined aspect ratio. To image and characterize the produced nanopores, helium ion microscopy and high resolution scanning transmission electron microscopy were used. The analysis of the nanopores' growth behavior allows inferring on the profile of the helium ion beam.

  6. Electrochemistry at Edge of Single Graphene Layer in a Nanopore

    PubMed Central

    Banerjee, Shouvik; Shim, Jiwook; Rivera, Jose; Jin, Xiaozhong; Estrada, David; Solovyeva, Vita; You, Xiuque; Pak, James; Pop, Eric; Aluru, Narayana; Bashir, Rashid

    2013-01-01

    We study the electrochemistry of single layer graphene edges using a nanopore-based structure consisting of stacked graphene and Al2O3 dielectric layers. Nanopores, with diameters ranging from 5 to 20 nm, are formed by an electron beam sculpting process on the stacked layers. This leads to unique edge structure which, along with the atomically thin nature of the embedded graphene electrode, demonstrates electrochemical current densities as high as 1.2 × 104 A/cm2. The graphene edge embedded structure offers a unique capability to study the electrochemical exchange at an individual graphene edge, isolated from the basal plane electrochemical activity. We also report ionic current modulation in the nanopore by biasing the embedded graphene terminal with respect to the electrodes in the fluid. The high electrochemical specific current density for a graphene nanopore-based device can have many applications in sensitive chemical and biological sensing, and energy storage devices. PMID:23249127

  7. Microscopic failure behavior of nanoporous Gold

    SciTech Connect

    Biener, J; Hodge, A; Hamza, A

    2005-01-10

    Nanoporous metals have recently attracted considerable interest fueled by potential sensor and actuator applications. One of the key issues in this context is the synthesis of high yield strength materials. Nanoporous Au (np-Au) has been suggested as a candidate due to its monolithic character. The material can be synthesized by dealloying Ag-Au alloys, and exhibits an open sponge-like morphology of interconnecting Au ligaments with a typical pore size distribution on the nanometer length scale. Unfortunately, very little is known about the mechanical properties of np-Au besides a length-scale dependent ductile-brittle transition. A key question in this context is: what causes the macroscopic brittleness of np-Au? Is the normal dislocation-mediated plastic deformation suppressed in nanoscale Au ligaments, or is the brittleness a consequence of the macroscopic morphology? Here, we report on the fracture behavior of nanoporous Au studied by scanning electron microscopy. Specifically, we demonstrate the microscopic ductility of nanometer-sized Au ligaments. The observed fracture behavior seems to be general for nanoporous metals, and can be understood in terms of simple fuse networks.

  8. Nanopores: A journey towards DNA sequencing

    PubMed Central

    Wanunu, Meni

    2013-01-01

    Much more than ever, nucleic acids are recognized as key building blocks in many of life's processes, and the science of studying these molecular wonders at the single-molecule level is thriving. A new method of doing so has been introduced in the mid 1990's. This method is exceedingly simple: a nanoscale pore that spans across an impermeable thin membrane is placed between two chambers that contain an electrolyte, and voltage is applied across the membrane using two electrodes. These conditions lead to a steady stream of ion flow across the pore. Nucleic acid molecules in solution can be driven through the pore, and structural features of the biomolecules are observed as measurable changes in the trans-membrane ion current. In essence, a nanopore is a high-throughput ion microscope and a single-molecule force apparatus. Nanopores are taking center stage as a tool that promises to read a DNA sequence, and this promise has resulted in overwhelming academic, industrial, and national interest. Regardless of the fate of future nanopore applications, in the process of this 16-year-long exploration, many studies have validated the indispensability of nanopores in the toolkit of single-molecule biophysics. This review surveys past and current studies related to nucleic acid biophysics, and will hopefully provoke a discussion of immediate and future prospects for the field. PMID:22658507

  9. Synthesis on structure and properties of zinc nanocrystal in high ordered 3D nanostructures

    SciTech Connect

    Sathyaseelan, B.; Manigandan, A.; Anbarasu, V.; Sivakumar, K.

    2015-06-24

    The wet impregnation method was employed to prepare ZnO encapsulated in mesoporous silica (ZnO/KIT-6). The prepared ZnO/KIT-6 samples have been studied by X-ray diffraction, transmission electron microscope, and nitrogen adsorption–desorption isotherm. The low angle powder XRD patterns of Calcined ZnO/KIT-6 materials showed a phase that can be indexed to cubic Ia3d. Tem images revealed well ordered cubic 3D nanoporous chennels. The ZnO encapsulated in KIT-6 can be used as light-emitting diodes and ultraviolet nanolasers.

  10. Fast fabrication of self-ordered anodic porous alumina on oriented aluminum grains by high acid concentration and high temperature anodization.

    PubMed

    Cheng, Chuan; Ngan, Alfonso H W

    2013-05-31

    Anodic porous alumina, which exhibits a characteristic nanohoneycomb structure, has been used in a wide range of nanotechnology applications. The conventional fabrication method of mild anodization (MA) requires a prolonged anodization time which is impractical for batch processing, and self-ordered porous structures can only be formed within narrow processing windows so that the dimensions of the resultant structures are extremely limited. The alternative hard anodization (HA) may easily result in macroscopic defects on the alumina surface. In this work, by systematically varying the anodization conditions including the substrate grain orientation, electrolyte concentration, temperature, voltage, and time, a new oxalic acid based anodization method, called high acid concentration and high temperature anodization (HHA), is found, which can result in far better self-ordering of the porous structures at rates 7-26 times faster than MA, under a continuous voltage range of 30-60 V on (001) oriented Al grains. Unlike HA, no macroscopic defects appear under the optimum self-ordered conditions of HHA at 40 V, even for pore channels grown up to high aspect ratios of more than 3000. Compared to MA and HA, HHA provides more choices of self-ordered nano-porous structures with fast and mechanically stable formation features for practical applications. PMID:23619572

  11. Surface Remeshing with Robust High-Order Reconstruction

    SciTech Connect

    Ray, Navamita; Delaney, Tristan; Einstein, Daniel R.; Jiao, Xiangmin

    2014-03-26

    Remeshing is an important problem in variety of applications, such as finite element methods and geometry processing. Surface remeshing poses some unique challenges, as it must deliver not only good mesh quality but also good geometric accuracy. For applications such as finite elements with high-order elements (quadratic or cubic elements), the geometry must be preserved to high-order (third-order or higher) accuracy, since low-order accuracy may undermine the convergence of numerical computations. The problem is particularly challenging if the CAD model is not available for the underlying geometry, and is even more so if the surface meshes contain some inverted elements. We describe remeshing strategies that can simultaneously produce high-quality triangular meshes, untangling mildly folded triangles and preserve the geometry to high-order of accuracy. Our approach extends our earlier works on high-order surface reconstruction and mesh optimization by enhancing its robustness with a geometric limiter for under-resolved geometries. We also integrate high-order surface reconstruction with surface mesh adaptation techniques, which alter the number of triangles and nodes. We demonstrate the utilization of our method to meshes for high-order finite elements, biomedical image-based surface meshes, and complex interface meshes in fluid simulations.

  12. Generation of intense high-order vortex harmonics.

    PubMed

    Zhang, Xiaomei; Shen, Baifei; Shi, Yin; Wang, Xiaofeng; Zhang, Lingang; Wang, Wenpeng; Xu, Jiancai; Yi, Longqiong; Xu, Zhizhan

    2015-05-01

    This Letter presents for the first time a scheme to generate intense high-order optical vortices that carry orbital angular momentum in the extreme ultraviolet region based on relativistic harmonics from the surface of a solid target. In the three-dimensional particle-in-cell simulation, the high-order harmonics of the high-order vortex mode is generated in both reflected and transmitted light beams when a linearly polarized Laguerre-Gaussian laser pulse impinges on a solid foil. The azimuthal mode of the harmonics scales with its order. The intensity of the high-order vortex harmonics is close to the relativistic region, with the pulse duration down to attosecond scale. The obtained intense vortex beam possesses the combined properties of fine transversal structure due to the high-order mode and the fine longitudinal structure due to the short wavelength of the high-order harmonics. In addition to the application in high-resolution detection in both spatial and temporal scales, it also presents new opportunities in the intense vortex required fields, such as the inner shell ionization process and high energy twisted photons generation by Thomson scattering of such an intense vortex beam off relativistic electrons. PMID:25978234

  13. Ion selectivity of graphene nanopores.

    PubMed

    Rollings, Ryan C; Kuan, Aaron T; Golovchenko, Jene A

    2016-01-01

    As population growth continues to outpace development of water infrastructure in many countries, desalination (the removal of salts from seawater) at high energy efficiency will likely become a vital source of fresh water. Due to its atomic thinness combined with its mechanical strength, porous graphene may be particularly well-suited for electrodialysis desalination, in which ions are removed under an electric field via ion-selective pores. Here, we show that single graphene nanopores preferentially permit the passage of K(+) cations over Cl(-) anions with selectivity ratios of over 100 and conduct monovalent cations up to 5 times more rapidly than divalent cations. Surprisingly, the observed K(+)/Cl(-) selectivity persists in pores even as large as about 20 nm in diameter, suggesting that high throughput, highly selective graphene electrodialysis membranes can be fabricated without the need for subnanometer control over pore size. PMID:27102837

  14. Ion selectivity of graphene nanopores

    NASA Astrophysics Data System (ADS)

    Rollings, Ryan C.; Kuan, Aaron T.; Golovchenko, Jene A.

    2016-04-01

    As population growth continues to outpace development of water infrastructure in many countries, desalination (the removal of salts from seawater) at high energy efficiency will likely become a vital source of fresh water. Due to its atomic thinness combined with its mechanical strength, porous graphene may be particularly well-suited for electrodialysis desalination, in which ions are removed under an electric field via ion-selective pores. Here, we show that single graphene nanopores preferentially permit the passage of K+ cations over Cl- anions with selectivity ratios of over 100 and conduct monovalent cations up to 5 times more rapidly than divalent cations. Surprisingly, the observed K+/Cl- selectivity persists in pores even as large as about 20 nm in diameter, suggesting that high throughput, highly selective graphene electrodialysis membranes can be fabricated without the need for subnanometer control over pore size.

  15. Nanoporous gold for enzyme immobilization.

    PubMed

    Stine, Keith J; Jefferson, Kenise; Shulga, Olga V

    2011-01-01

    Nanoporous gold (NPG) is a material of emerging interest for immobilization of biomolecules and -especially enzymes. NPG materials provide a high gold surface area onto which biomolecules can either be directly physisorbed or covalently linked after first modifying the NPG with a self-assembled monolayer. The material can be used as a high surface area electrode and with immobilized enzymes can be used for amperometric detection schemes. NPG can be prepared in a variety of formats from alloys containing less than 50 atomic% gold by dealloying procedures. Related high surface area gold structures have been prepared using templating approaches. Covalent enzyme immobilization can be achieved by first forming a self-assembled monolayer on NPG bearing a terminal reactive functional group followed by conjugation to the enzyme through amide linkages to lysine residues. PMID:20865389

  16. Ion selectivity of graphene nanopores

    PubMed Central

    Rollings, Ryan C.; Kuan, Aaron T.; Golovchenko, Jene A.

    2016-01-01

    As population growth continues to outpace development of water infrastructure in many countries, desalination (the removal of salts from seawater) at high energy efficiency will likely become a vital source of fresh water. Due to its atomic thinness combined with its mechanical strength, porous graphene may be particularly well-suited for electrodialysis desalination, in which ions are removed under an electric field via ion-selective pores. Here, we show that single graphene nanopores preferentially permit the passage of K+ cations over Cl− anions with selectivity ratios of over 100 and conduct monovalent cations up to 5 times more rapidly than divalent cations. Surprisingly, the observed K+/Cl− selectivity persists in pores even as large as about 20 nm in diameter, suggesting that high throughput, highly selective graphene electrodialysis membranes can be fabricated without the need for subnanometer control over pore size. PMID:27102837

  17. Ion selectivity of graphene nanopores

    DOE PAGESBeta

    Rollings, Ryan C.; Kuan, Aaron T.; Golovchenko, Jene A.

    2016-04-22

    As population growth continues to outpace development of water infrastructure in many countries, desalination (the removal of salts from seawater) at high energy efficiency will likely become a vital source of fresh water. Due to its atomic thinness combined with its mechanical strength, porous graphene may be particularly well-suited for electrodialysis desalination, in which ions are removed under an electric field via ion-selective pores. Here, we show that single graphene nanopores preferentially permit the passage of K+ cations over Cl- anions with selectivity ratios of over 100 and conduct monovalent cations up to 5 times more rapidly than divalent cations.more » Furthermore, the observed K+/Cl- selectivity persists in pores even as large as about 20 nm in diameter, suggesting that high throughput, highly selective graphene electrodialysis membranes can be fabricated without the need for subnanometer control over pore size.« less

  18. Toward sensitive graphene nanoribbon-nanopore devices by preventing electron beam-induced damage.

    PubMed

    Puster, Matthew; Rodríguez-Manzo, Julio A; Balan, Adrian; Drndić, Marija

    2013-12-23

    Graphene-based nanopore devices are promising candidates for next-generation DNA sequencing. Here we fabricated graphene nanoribbon-nanopore (GNR-NP) sensors for DNA detection. Nanopores with diameters in the range 2-10 nm were formed at the edge or in the center of graphene nanoribbons (GNRs), with widths between 20 and 250 nm and lengths of 600 nm, on 40 nm thick silicon nitride (SiN(x)) membranes. GNR conductance was monitored in situ during electron irradiation-induced nanopore formation inside a transmission electron microscope (TEM) operating at 200 kV. We show that GNR resistance increases linearly with electron dose and that GNR conductance and mobility decrease by a factor of 10 or more when GNRs are imaged at relatively high magnification with a broad beam prior to making a nanopore. By operating the TEM in scanning TEM (STEM) mode, in which the position of the converged electron beam can be controlled with high spatial precision via automated feedback, we were able to prevent electron beam-induced damage and make nanopores in highly conducting GNR sensors. This method minimizes the exposure of the GNRs to the beam before and during nanopore formation. The resulting GNRs with unchanged resistances after nanopore formation can sustain microampere currents at low voltages (∼50 mV) in buffered electrolyte solution and exhibit high sensitivity, with a large relative change of resistance upon changes of gate voltage, similar to pristine GNRs without nanopores. PMID:24224888

  19. Weakened Flexural Strength of Nanocrystalline Nanoporous Gold by Grain Refinement.

    PubMed

    Gwak, Eun-Ji; Kim, Ju-Young

    2016-04-13

    High density of grain boundaries in solid materials generally leads to high strength because grain boundaries act as strong obstacles to dislocation activity. We find that the flexural strength of nanoporous gold of grain size 206 nm is 33.6% lower than that of grain size 238 μm. We prepared three gold-silver precursor alloys, well-annealed, prestrained, and high-energy ball-milled, from which nanoporous gold samples were obtained by the same free-corrosion dealloying process. Ligaments of the same size are formed regardless of precursor alloys, and microstructural aspects of precursor alloys such as crystallographic orientation and grain size is preserved in the dealloying process. While the nanoindentation hardness of three nanoporous golds is independent of microstructural variation, flexural strength of nanocrystalline nanoporous gold is significantly lower than that of nanoporous golds with much larger grain size. We investigate weakening mechanisms of grain boundaries in nanocrystalline nanoporous gold, leading to weakening of flexural strength. PMID:26982460

  20. Salinity gradient power: influences of temperature and nanopore size

    NASA Astrophysics Data System (ADS)

    Tseng, Shiojenn; Li, Yu-Ming; Lin, Chih-Yuan; Hsu, Jyh-Ping

    2016-01-01

    Salinity gradient power is a promising, challenging, and readily available renewable energy. Among various methods for harvesting this clean energy, nanofluidic reverse electrodialysis (NRED) is of great potential. Since ionic transport depends highly on the temperature, so is the efficiency of the associated power generated. Here, we conduct a theoretical analysis on the influences of temperature and nanopore size on NRED, focusing on the temperature and nanopore size. The results gathered reveal that the maximum power increases with increasing temperature, but the conversion efficiency depends weakly on temperature. In general, the smaller the nanopore radius or the longer the nanopore, the better the ion selectivity. These results provide desirable and necessary information for improving the performance of NRED as well as designing relevant units in renewable energy plants.

  1. Salinity gradient power: influences of temperature and nanopore size.

    PubMed

    Tseng, Shiojenn; Li, Yu-Ming; Lin, Chih-Yuan; Hsu, Jyh-Ping

    2016-01-28

    Salinity gradient power is a promising, challenging, and readily available renewable energy. Among various methods for harvesting this clean energy, nanofluidic reverse electrodialysis (NRED) is of great potential. Since ionic transport depends highly on the temperature, so is the efficiency of the associated power generated. Here, we conduct a theoretical analysis on the influences of temperature and nanopore size on NRED, focusing on the temperature and nanopore size. The results gathered reveal that the maximum power increases with increasing temperature, but the conversion efficiency depends weakly on temperature. In general, the smaller the nanopore radius or the longer the nanopore, the better the ion selectivity. These results provide desirable and necessary information for improving the performance of NRED as well as designing relevant units in renewable energy plants. PMID:26752789

  2. Nanoporous CuS with excellent photocatalytic property

    NASA Astrophysics Data System (ADS)

    Xu, Wence; Zhu, Shengli; Liang, Yanqin; Li, Zhaoyang; Cui, Zhenduo; Yang, Xianjin; Inoue, Akihisa

    2015-12-01

    We present the rational synthesis of nanoporous CuS for the first time by chemical dealloying method. The morphologies of the CuS catalysts are controlled by the composition of the original amorphous alloys. Nanoporous Cu2S is firstly formed during the chemical dealloying process, and then the Cu2S transforms into CuS. The nanoporous CuS exhibits excellent photocatalytic activity for the degradation of the methylene blue (MB), methyl orange (MO) and rhodamine B (RhB). The excellent photocatalytic activity of the nanoporous CuS is mainly attributed to the large specific surface area, high adsorbing capacity of dyes and low recombination of the photo generated electrons and holes. In the photo degradation process, both chemical and photo generated hydroxyl radicals are generated. The hydroxyl radicals are favor in the oxidation of the dye molecules. The present modified dealloying method may be extended for the preparation of other porous metal sulfide nanostructures.

  3. Highly efficient direct aerobic oxidative esterification of cinnamyl alcohol with alkyl alcohols catalysed by gold nanoparticles incarcerated in a nanoporous polymer matrix: a tool for investigating the role of the polymer host.

    PubMed

    Buonerba, Antonio; Noschese, Annarita; Grassi, Alfonso

    2014-04-25

    The selective aerobic oxidation of cinnamyl alcohol to cinnamaldehyde, as well as direct oxidative esterification of this alcohol with primary and secondary aliphatic alcohols, were achieved with high chemoselectivity by using gold nanoparticles supported in a nanoporous semicrystalline multi-block copolymer matrix, which consisted of syndiotactic polystyrene-co-cis-1,4-polybutadiene. The cascade reaction that leads to the alkyl cinnamates occurs through two oxidation steps: the selective oxidation of cinnamyl alcohol to cinnamaldehyde, followed by oxidation of the hemiacetal that results from the base-catalysed reaction of cinnamaldehyde with an aliphatic alcohol. The rate constants for the two steps were evaluated in the temperature range 10-45 °C. The cinnamyl alcohol oxidation is faster than the oxidative esterification of cinnamaldehyde with methanol, ethanol, 2-propanol, 1-butanol, 1-hexanol or 1-octanol. The rate constants of the latter reaction are pseudo-zero order with respect to the aliphatic alcohol and decrease as the bulkiness of the alcohol is increased. The activation energy (Ea) for the two oxidation steps was calculated for esterification of cinnamyl alcohol with 1-butanol (Ea = 57.8±11.5 and 62.7±16.7 kJ mol(-1) for the first and second step, respectively). The oxidative esterification of cinnamyl alcohol with 2-phenylethanol follows pseudo-first-order kinetics with respect to 2-phenylethanol and is faster than observed for other alcohols because of fast diffusion of the aromatic alcohol in the crystalline phase of the support. The kinetic investigation allowed us to assess the role of the polymer support in the determination of both high activity and selectivity in the title reaction. PMID:24644103

  4. Facile Self-Cross-Linking Synthesis of 3D Nanoporous Co3O4/Carbon Hybrid Electrode Materials for Supercapacitors.

    PubMed

    Wang, Ning; Liu, Qinglei; Kang, Danmiao; Gu, Jiajun; Zhang, Wang; Zhang, Di

    2016-06-29

    A hybrid electrode material with ultrafine Co3O4 nanoparticles embedded throughout a hierarchically nanoporous graphitic carbon matrix has been obtained via a facile self-cross-linking route. Sodium alginate, a biopolymer with an ability of cross-linking with multivalent cobalt cations to form ordered microcrystalline zones, is used as a carbon source to produce nanoporous carbon frameworks of the hybrids. Ultrafine Co3O4 nanoparticles with tunable particle size (3-30 nm) are in situ grown within the nanoporous graphitic carbon frameworks by a simple carbonization of Co-cross-linked alginate. The obtained hybrid electrodes exhibit high specific capacitance of 645, 548, 486, and 347 F/g at scan rates of 5, 10, 20, and 50 mV/s, respectively, and excellent cycle performance with only 1% fading in capacitance after 10 000 cycles at a high current density of 20 A/g. Such excellent capacitive performance is ascribed to the collaborative contributions of well-dispersed ultrafine Co3O4 nanoparticles and conductive nanoporous carbon frameworks. PMID:27266717

  5. Nanoporous PdZr surface alloy as highly active non-platinum electrocatalyst toward oxygen reduction reaction with unique structure stability and methanol-tolerance

    NASA Astrophysics Data System (ADS)

    Duan, Huimei; Xu, Caixia

    2016-06-01

    Nanoporous (NP) PdZr alloy with controllable bimetallic ratio is successfully fabricated by a simple dealloying method. By leaching out the more reactive Al from PdZrAl precursor alloy, NP-PdZr alloy with smaller ligament size was generated, characterized by the nanoscaled interconnected network skeleton and hollow channels extending in all three dimensions. Upon voltammetric scan in acid solution, the dissolution of surface Zr atoms generates the highly active Pd-Zr surface alloy with a nearly pure Pd surface and Pd-Zr alloy core. The NP-Pd80Zr20 surface alloy exhibits markedly enhanced specific and mass activities as well as higher catalytic stability toward oxygen reduction reaction (ORR) compared with NP-Pd and the state-of-the-art Pt/C catalysts. In addition, the NP-Pd80Zr20 surface alloy shows a better selectivity for ORR than methanol in the 0.1 M HClO4 and 0.1 M methanol mixed solution. X-ray photoelectron spectroscopy and density functional theory calculations both demonstrate that the weakened Pd-O bond and improved ORR performances in turn depend on the downshifted d-band center of Pd due to the alloying Pd with Zr (20 at.%). The as-made NP-PdZr alloy holds prospective applications as a cathode electrocatalyst in fuel-cell-related technologies with the advantages of superior overall ORR performances, unique structure stability, and easy preparation.

  6. Versatile metal-organic framework-functionalized magnetic graphene nanoporous composites: As deft matrix for high-effective extraction and purification of the N-linked glycans.

    PubMed

    Wang, Jiaxi; Wang, Yanan; Gao, Mingxia; Zhang, Xiangmin; Yang, Pengyuan

    2016-08-17

    The highly selective enrichment of N-linked glycans from complex biological sample is still very important but challenging task due to the ultra-low abundance, complicated structures and strong ion suppress effect caused by distractors such as proteins, peptides and salts. Here, we firstly present a novel metal-organic frameworks (MOFs)-functionalized magnetic nanoporous carbon-graphene composites (C-magG@ZIF-8) synthesized through a smart process. The obtained materials enjoy the unique properties including strong magnetic responsiveness, a large sum of graphitized carbon pore, remarkable biocompatibility and large specific surface area. By virtue of these unique properties, the C-magG@ZIF-8 composites displayed excellent selectivity and sensitivity, good recyclability and incredible size exclusion ability (roughly 2000 times) in the N-linked glycans analysis. Furthermore, 48 N-linked glycans were clearly identified from the normal human serum treated with the C-magG@ZIF-8. There is reason to believe that our smart strategy offers new possibilities for preparing the MOFs-functionalized composites for large-scale characterization of glycoproteomics by mass spectrometry analysis. PMID:27286768

  7. Optimized nanoporous materials.

    SciTech Connect

    Braun, Paul V.; Langham, Mary Elizabeth; Jacobs, Benjamin W.; Ong, Markus D.; Narayan, Roger J.; Pierson, Bonnie E.; Gittard, Shaun D.; Robinson, David B.; Ham, Sung-Kyoung; Chae, Weon-Sik; Gough, Dara V.; Wu, Chung-An Max; Ha, Cindy M.; Tran, Kim L.

    2009-09-01

    Nanoporous materials have maximum practical surface areas for electrical charge storage; every point in an electrode is within a few atoms of an interface at which charge can be stored. Metal-electrolyte interfaces make best use of surface area in porous materials. However, ion transport through long, narrow pores is slow. We seek to understand and optimize the tradeoff between capacity and transport. Modeling and measurements of nanoporous gold electrodes has allowed us to determine design principles, including the fact that these materials can deplete salt from the electrolyte, increasing resistance. We have developed fabrication techniques to demonstrate architectures inspired by these principles that may overcome identified obstacles. A key concept is that electrodes should be as close together as possible; this is likely to involve an interpenetrating pore structure. However, this may prove extremely challenging to fabricate at the finest scales; a hierarchically porous structure can be a worthy compromise.

  8. Discrimination of oligonucleotides of different lengths with a wild-type aerolysin nanopore

    NASA Astrophysics Data System (ADS)

    Cao, Chan; Ying, Yi-Lun; Hu, Zheng-Li; Liao, Dong-Fang; Tian, He; Long, Yi-Tao

    2016-08-01

    Protein nanopores offer an inexpensive, label-free method of analysing single oligonucleotides. The sensitivity of the approach is largely determined by the characteristics of the pore-forming protein employed, and typically relies on nanopores that have been chemically modified or incorporate molecular motors. Effective, high-resolution discrimination of oligonucleotides using wild-type biological nanopores remains difficult to achieve. Here, we show that a wild-type aerolysin nanopore can resolve individual short oligonucleotides that are 2 to 10 bases long. The sensing capabilities are attributed to the geometry of aerolysin and the electrostatic interactions between the nanopore and the oligonucleotides. We also show that the wild-type aerolysin nanopores can distinguish individual oligonucleotides from mixtures and can monitor the stepwise cleavage of oligonucleotides by exonuclease I.

  9. Discrimination of oligonucleotides of different lengths with a wild-type aerolysin nanopore.

    PubMed

    Cao, Chan; Ying, Yi-Lun; Hu, Zheng-Li; Liao, Dong-Fang; Tian, He; Long, Yi-Tao

    2016-08-01

    Protein nanopores offer an inexpensive, label-free method of analysing single oligonucleotides. The sensitivity of the approach is largely determined by the characteristics of the pore-forming protein employed, and typically relies on nanopores that have been chemically modified or incorporate molecular motors. Effective, high-resolution discrimination of oligonucleotides using wild-type biological nanopores remains difficult to achieve. Here, we show that a wild-type aerolysin nanopore can resolve individual short oligonucleotides that are 2 to 10 bases long. The sensing capabilities are attributed to the geometry of aerolysin and the electrostatic interactions between the nanopore and the oligonucleotides. We also show that the wild-type aerolysin nanopores can distinguish individual oligonucleotides from mixtures and can monitor the stepwise cleavage of oligonucleotides by exonuclease I. PMID:27111839

  10. Na⁺ and K⁺ ion selectivity by size-controlled biomimetic graphene nanopores.

    PubMed

    Kang, Yu; Zhang, Zhisen; Shi, Hui; Zhang, Junqiao; Liang, Lijun; Wang, Qi; Ågren, Hans; Tu, Yaoquan

    2014-09-21

    Because biological ionic channels play a key role in cellular transport phenomena, they have attracted extensive research interest for the design of biomimetic nanopores with high permeability and selectivity in a variety of technical applications. Inspired by the structure of K(+) channel proteins, we designed a series of oxygen doped graphene nanopores of different sizes by molecular dynamics simulations to discriminate between K(+) and Na(+) channel transport. The results from free energy calculations indicate that the ion selectivity of such biomimetic graphene nanopores can be simply controlled by the size of the nanopore; compared to K(+), the smaller radius of Na(+) leads to a significantly higher free energy barrier in the nanopore of a certain size. Our results suggest that graphene nanopores with a distance of about 3.9 Å between two neighboring oxygen atoms could constitute a promising candidate to obtain excellent ion selectivity for Na(+) and K(+) ions. PMID:25089590

  11. Nanoporous Ti-metal film deposition using radio frequency magnetron sputtering technique for photovoltaic application.

    PubMed

    Sung, Youl-Moon; Paeng, Sung-Hwan; Moon, Byung-Ho; Kwak, Dong-Joo

    2012-02-01

    Nanoporous Ti-metal film electrode was fabricated by radio frequency (rf) magnetron sputtering technique on nanoporous TiO2 layer prepared by sol-gel combustion method and investigated with respect to its photo-anode properties of TCO-less DSCs. The porous Ti layer (approximately 1 microm) with low sheet resistance (approximately 17 Omega/sq.) can collect electrons from the TiO2 layer and allows the ionic diffusion of I(-)/I(3-) through the hole. The porous Ti layer with highly ordered columnar structure prepared by 8 mTorr sputtering shows the good impedance characteristics. The efficiency of prepared TCO-less DSCs sample is about 4.83% (ff: 0.6, Voc: 0.65 V, Jsc: 11.2 mA/cm2). PMID:22629960

  12. De novo sequencing and variant calling with nanopores using PoreSeq

    PubMed Central

    Szalay, Tamas; Golovchenko, Jene A.

    2016-01-01

    The single-molecule accuracy of nanopore sequencing has been an area of rapid academic and commercial advancement, but remains challenging for the de novo analysis of genomes. We introduce here a novel algorithm for the error correction of nanopore data, utilizing statistical models of the physical system in order to obtain high accuracy de novo sequences at a range of coverage depths. We demonstrate the technique by sequencing M13 bacteriophage DNA to 99% accuracy at moderate coverage as well as its use in an assembly pipeline by sequencing E. coli and λ DNA at a range of coverages. We also show the algorithm’s ability to accurately classify sequence variants at far lower coverage than existing methods. PMID:26352647

  13. High Spin-Chern Insulators with Magnetic Order

    PubMed Central

    Ezawa, Motohiko

    2013-01-01

    As a topological insulator, the quantum Hall (QH) effect is indexed by the Chern and spin-Chern numbers and . We have only in conventional QH systems. We investigate QH effects in generic monolayer honeycomb systems. We search for spin-resolved characteristic patterns by exploring Hofstadter's butterfly diagrams in the lattice theory and fan diagrams in the low-energy Dirac theory. It is shown that the spin-Chern number can takes an arbitrary high value for certain QH systems. This is a new type of topological insulators, which we may call high spin-Chern insulators. Samples may be provided by graphene on the SiC substrate with ferromagnetic order, transition-metal dichalcogenides with ferromagnetic order, transition-metal oxide with antiferromagnetic order and silicene with ferromagnetic order. Actually high spin-Chern insulators are ubiquitous in any systems with magnetic order. Nevertheless, the honeycomb system would provide us with unique materials for practical materialization. PMID:24310394

  14. High Spin-Chern Insulators with Magnetic Order

    NASA Astrophysics Data System (ADS)

    Ezawa, Motohiko

    2013-12-01

    As a topological insulator, the quantum Hall (QH) effect is indexed by the Chern and spin-Chern numbers and . We have only in conventional QH systems. We investigate QH effects in generic monolayer honeycomb systems. We search for spin-resolved characteristic patterns by exploring Hofstadter's butterfly diagrams in the lattice theory and fan diagrams in the low-energy Dirac theory. It is shown that the spin-Chern number can takes an arbitrary high value for certain QH systems. This is a new type of topological insulators, which we may call high spin-Chern insulators. Samples may be provided by graphene on the SiC substrate with ferromagnetic order, transition-metal dichalcogenides with ferromagnetic order, transition-metal oxide with antiferromagnetic order and silicene with ferromagnetic order. Actually high spin-Chern insulators are ubiquitous in any systems with magnetic order. Nevertheless, the honeycomb system would provide us with unique materials for practical materialization.

  15. New high order schemes in BATS-R-US

    NASA Astrophysics Data System (ADS)

    Toth, G.; van der Holst, B.; Daldorff, L.; Chen, Y.; Gombosi, T. I.

    2013-12-01

    The University of Michigan global magnetohydrodynamics code BATS-R-US has long relied on the block-adaptive mesh refinement (AMR) to increase accuracy in regions of interest, and we used a second order accurate TVD scheme. While AMR can in principle produce arbitrarily accurate results, there are still practical limitations due to computational resources. To further improve the accuracy of the BATS-R-US code, recently, we have implemented a 4th order accurate finite volume scheme (McCorquodale and Colella, 2011}), the 5th order accurate Monotonicity Preserving scheme (MP5, Suresh and Huynh, 1997) and the 5th order accurate CWENO5 scheme (Capdeville, 2008). In the first implementation the high order accuracy is achieved in the uniform parts of the Cartesian grids, and we still use the second order TVD scheme at resolution changes. For spherical grids the new schemes are only second order accurate so far, but still much less diffusive than the TVD scheme. We show a few verification tests that demonstrate the order of accuracy as well as challenging space physics applications. The high order schemes are less robust than the TVD scheme, and it requires some tricks and effort to make the code work. When the high order scheme works, however, we find that in most cases it can obtain similar or better results than the TVD scheme on twice finer grids. For three dimensional time dependent simulations this means that the high order scheme is almost 10 times faster requires 8 times less storage than the second order method.

  16. Widely tuning optical properties of nanoporous gold-titania core-shells.

    PubMed

    Qian, Lihua; Shen, Bo; Qin, Gaowu W; Das, Biswajit

    2011-01-01

    Widely shifting localized surface plasmon resonance (LSPR) bands of nanoporous metals is essential for light manipulation within small volumes. In this work, nanoporous gold-titania core-shells fabricated by atomic layer deposition exhibit tunable LSPR of gold skeletons in comparison with nanoporous gold-alumina developed before. Extremely large red-shift of LSPR band in nanoporous gold-titania from 537 to 751 nm results from high refractive index of titania and its dielectric medium dependence of LSPR, and the well-controlled thickness of titania shell at the nanometer scale will benefit to integrate optical nanodevices with supreme performances. PMID:21219020

  17. Study of Nanopore Sculpting with Noble Gas Ion Beams at Various Energies

    NASA Astrophysics Data System (ADS)

    Ledden, Bradley; Krueger, Eric; Li, Jiali

    2006-03-01

    We report on experiments using noble gas beams: Helium, Neon, Argon, Krypton, and Xenon, at energies of 1keV, 3keV, and 5keV to controllably fabricate nanopores in freestanding silicon nitride membranes. Utilizing computer simulations (SRIM and TRIM), and a surface adatom diffusion model to describe the phenomenon of nanopore formation, we evaluate the conditions, specifically the ion energy, responsible for highly controllable fabrication of solid state nanopores. Additionally, we present methods to determine the thickness of the grown film as well as the thickness profile of the nanopore.

  18. A High-Order Multiscale Global Atmospheric Model

    NASA Astrophysics Data System (ADS)

    Nair, Ram

    2016-04-01

    The High-Order Method Modeling Environment (HOMME), developed at NCAR, is a petascale hydrostatic framework, which employs the cubed-sphere grid system and high-order continuous or discontinuous Galerkin (DG) methods. Recently, the HOMME framework is being extended to a non-hydrostatic dynamical core, named as the "High-Order Multiscale Atmospheric Model (HOMAM)." The spatial discretization is based on DG or high-order finite-volume methods. Orography is handled by the terrain-following height-based coordinate system. To alleviate the stringent CFL stability requirement resulting from the vertical aspects of the dynamics, an operator-splitting time integration scheme based on the horizontally explicit and vertically implicit (HEVI) philosophy is adopted for HOMAM. Preliminary results with the benchmark test cases proposed in the Dynamical Core Model Intercomparison project (DCMIP) test-suite will be presented in the seminar.

  19. Near infrared frequency dependence of high-order sideband generation

    SciTech Connect

    Zaks, Benjamin; Banks, Hunter; Sherwin, Mark; Liu, Ren-Bao

    2013-12-04

    The near infrared frequency dependence of high order sideband generation in InGaAs quantum wells is discussed. The NIR frequency dependence of the sidebands indicates that the HSG phenomenon is excitonic in nature.

  20. Lipid bilayer coated Al(2)O(3) nanopore sensors: towards a hybrid biological solid-state nanopore.

    PubMed

    Venkatesan, Bala Murali; Polans, James; Comer, Jeffrey; Sridhar, Supriya; Wendell, David; Aksimentiev, Aleksei; Bashir, Rashid

    2011-08-01

    Solid-state nanopore sensors are highly versatile platforms for the rapid, label-free electrical detection and analysis of single molecules, applicable to next generation DNA sequencing. The versatility of this technology allows for both large scale device integration and interfacing with biological systems. Here we report on the development of a hybrid biological solid-state nanopore platform that incorporates a highly mobile lipid bilayer on a single solid-state Al(2)O(3) nanopore sensor, for the potential reconstitution of ion channels and biological nanopores. Such a system seeks to combine the superior electrical, thermal, and mechanical stability of Al(2)O(3) solid-state nanopores with the chemical specificity of biological nanopores. Bilayers on Al(2)O(3) exhibit higher diffusivity than those formed on TiO(2) and SiO(2) substrates, attributed to the presence of a thick hydration layer on Al(2)O(3), a key requirement to preserving the biological functionality of reconstituted membrane proteins. Molecular dynamics simulations demonstrate that the electrostatic repulsion between the dipole of the DOPC headgroup and the positively charged Al(2)O(3) surface may be responsible for the enhanced thickness of this hydration layer. Lipid bilayer coated Al(2)O(3) nanopore sensors exhibit excellent electrical properties and enhanced mechanical stability (GΩ seals for over 50 h), making this technology ideal for use in ion channel electrophysiology, the screening of ion channel active drugs and future integration with biological nanopores such as α-hemolysin and MspA for rapid single molecule DNA sequencing. This technology can find broad application in bio-nanotechnology. PMID:21487665

  1. Controlled synthesis of nanoporous nickel oxide with two-dimensional shapes through thermal decomposition of metal-cyanide hybrid coordination polymers.

    PubMed

    Zakaria, Mohamed B; Hu, Ming; Salunkhe, Rahul R; Pramanik, Malay; Takai, Kimiko; Malgras, Victor; Choi, Seyong; Dou, Shi Xue; Kim, Jung Ho; Imura, Masataka; Ishihara, Shinsuke; Yamauchi, Yusuke

    2015-02-23

    The urgent need for nanoporous metal oxides with highly crystallized frameworks is motivating scientists to try to discover new preparation methods, because of their wide use in practical applications. Recent work has demonstrated that two-dimensional (2D) cyanide-bridged coordination polymers (CPs) are promising materials and appropriate for this purpose (Angew. Chem. Int. Ed.- 2013, 52, 1235). After calcination, 2D CPs can be transformed into nanoporous metal oxides with a highly accessible surface area. Here, this strategy is adopted in order to form 2D nanoporous nickel oxide (NiO) with tunable porosity and crystallinity, using trisodium citrate dihydrate as a controlling agent. The presence of trisodium citrate dihydrate plays a key role in the formation of 2D nanoflakes by controlling the nucleation rate and the crystal growth. The size of the nanoflakes gradually increases by augmenting the amount of trisodium citrate dihydrate in the reaction. After heating the as-prepared CPs in air at different temperatures, nanoporous NiO can be obtained. During this thermal treatment, organic units (carbon and nitrogen) are completely removed and only the metal content remains to take part in the formation of nanoporous NiO. In the case of large-sized 2D CP nanoflakes, the original 2D flake-shapes are almost retained, even after thermal treatment at low temperature, but they are completely destroyed at high temperature because of further crystallization in the framework. Nanoporous NiO with high surface area shows significant efficiency and interesting results for supercapacitor application. PMID:25639533

  2. Bonding Low-density Nanoporous Metal Foams Using Sputtered Solder

    SciTech Connect

    Bono, M; Cervantes, O; Akaba, C; Hamza, A; Foreman, R; Teslich, N

    2007-08-21

    A method has been developed for bonding low-density nanoporous metal foam components to a substrate using solder that is sputtered onto the surfaces. Metal foams have unusual properties that make them excellent choices for many applications, and as technologies for processing these materials are evolving, their use in industry is increasing dramatically. Metal foams are lightweight and have advantageous dynamic properties, which make them excellent choices for many structural applications. They also provide good acoustic damping, low thermal conductivity, and excellent energy absorption characteristics. Therefore, these materials are commonly used in the automotive, aerospace, construction, and biomedical industries. The synthesis of nanoporous metal foams with a cell size of less then 1 {micro}m is an emerging technology that is expected to lead to widespread application of metal foams in microdevices, such as sensors and actuators. One of the challenges to manufacturing components from metal foams is that they can be difficult to attach to other structures without degrading their properties. For example, traditional liquid adhesives cannot be used because they are absorbed into foams. The problem of bonding or joining can be particularly difficult for small-scale devices made from nanoporous foam, due to the requirement for a thin bond layer. The current study addresses this problem and develops a method of soldering a nanoporous metal foam to a substrate with a bond thickness of less than 2 {micro}m. There are many applications that require micro-scale metal foams precisely bonded to substrates. This study was motivated by a physics experiment that used a laser to drive a shock wave through an aluminum foil and into a copper foam, in order to determine the speed of the shock in the copper foam. To avoid disturbing the shock, the interface between the copper foam and the aluminum substrate had to be as thin as possible. There are many other applications that

  3. A stable 1D multigroup high-order low-order method

    DOE PAGESBeta

    Yee, Ben Chung; Wollaber, Allan Benton; Haut, Terry Scot; Park, HyeongKae

    2016-07-13

    The high-order low-order (HOLO) method is a recently developed moment-based acceleration scheme for solving time-dependent thermal radiative transfer problems, and has been shown to exhibit orders of magnitude speedups over traditional time-stepping schemes. However, a linear stability analysis by Haut et al. (2015 Haut, T. S., Lowrie, R. B., Park, H., Rauenzahn, R. M., Wollaber, A. B. (2015). A linear stability analysis of the multigroup High-Order Low-Order (HOLO) method. In Proceedings of the Joint International Conference on Mathematics and Computation (M&C), Supercomputing in Nuclear Applications (SNA) and the Monte Carlo (MC) Method; Nashville, TN, April 19–23, 2015. American Nuclear Society.)more » revealed that the current formulation of the multigroup HOLO method was unstable in certain parameter regions. Since then, we have replaced the intensity-weighted opacity in the first angular moment equation of the low-order (LO) system with the Rosseland opacity. Furthermore, this results in a modified HOLO method (HOLO-R) that is significantly more stable.« less

  4. A Simple Route for Preparation of Nanoporous Templates

    NASA Astrophysics Data System (ADS)

    Park, Soojin; Wang, Jia-Yu; Kim, Bokyung; Russell, Thomas

    2007-03-01

    Spin-coating method of block copolymers represents a very simple means of producing thin films for the fabrication of nanostructured materials. However, the orientation and long-range ordering of the block copolymer microdomains must be controlled to maximize areal density. Here, spin coated films of poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) diblock copolymers in THF/toluene solvent mixtures were investigated and it was found that highly oriented cylindrical microdomains with long-range lateral order were obtained on a variety of substrates, such as silicon oxide, polystyrene, polyimide, poly(butylene terephthalate), and germanium. The preferential solvation of P4VP block with an alcohol enabled a surface reconstruction to produce a structure of the block copolymer film that leads to the generation of a nanoporous template upon drying. The gold evaporation on the reconstructed films produces thermally stable and plasma resistant films.

  5. In-Situ Creation of Solid State Nanopores

    NASA Astrophysics Data System (ADS)

    Briggs, Kyle; Kwok, Harold; Tabard-Cossa, Vincent

    2013-03-01

    Recent advances in nanopore technology have demonstrated that they are a powerful tool for single biomolecule analysis, and great progress has been made toward the promise of nanopore-based DNA sequencing devices. A limiting factor in solid-state nanopore science is the complexity, throughput and cost of current fabrication methods, based on focused ion or election beam drilling, which require sophisticated equipment and highly trained personnel. Our laboratory at the University of Ottawa has demonstrated a simple and extremely low cost method to fabricate individual nanopores on thin solid-state membranes. By controlling an applied voltage across the membrane in aqueous salt solution, we are able to routinely create sub-5nm pores in dielectric membranes. In addition, the method can easily be extended to tune nanopore size with sub-nm precision. We will describe the fabrication method in detail, and present the effects of electric field strength, membrane material, solution salt composition, concentration and pH on the pore creation time and size distribution. These results allow us to elucidate the physical mechanisms responsible for nanopore formation.

  6. Colloquium: Theory of intertwined orders in high temperature superconductors

    NASA Astrophysics Data System (ADS)

    Fradkin, Eduardo; Kivelson, Steven A.; Tranquada, John M.

    2015-04-01

    The electronic phase diagrams of many highly correlated systems, and, in particular, the cuprate high temperature superconductors, are complex, with many different phases appearing with similar (sometimes identical) ordering temperatures even as material properties, such as dopant concentration, are varied over wide ranges. This complexity is sometimes referred to as "competing orders." However, since the relation is intimate, and can even lead to the existence of new phases of matter such as the putative "pair-density wave," the general relation is better thought of in terms of "intertwined orders." Some of the experiments in the cuprates which suggest that essential aspects of the physics are reflected in the intertwining of multiple orders, not just in the nature of each order by itself, are selectively analyzed. Several theoretical ideas concerning the origin and implications of this complexity are also summarized and critiqued.

  7. The evolution of nanopore sequencing.

    PubMed

    Wang, Yue; Yang, Qiuping; Wang, Zhimin

    2014-01-01

    The "$1000 Genome" project has been drawing increasing attention since its launch a decade ago. Nanopore sequencing, the third-generation, is believed to be one of the most promising sequencing technologies to reach four gold standards set for the "$1000 Genome" while the second-generation sequencing technologies are bringing about a revolution in life sciences, particularly in genome sequencing-based personalized medicine. Both of protein and solid-state nanopores have been extensively investigated for a series of issues, from detection of ionic current blockage to field-effect-transistor (FET) sensors. A newly released protein nanopore sequencer has shown encouraging potential that nanopore sequencing will ultimately fulfill the gold standards. In this review, we address advances, challenges, and possible solutions of nanopore sequencing according to these standards. PMID:25610451

  8. The evolution of nanopore sequencing

    PubMed Central

    Wang, Yue; Yang, Qiuping; Wang, Zhimin

    2014-01-01

    The “$1000 Genome” project has been drawing increasing attention since its launch a decade ago. Nanopore sequencing, the third-generation, is believed to be one of the most promising sequencing technologies to reach four gold standards set for the “$1000 Genome” while the second-generation sequencing technologies are bringing about a revolution in life sciences, particularly in genome sequencing-based personalized medicine. Both of protein and solid-state nanopores have been extensively investigated for a series of issues, from detection of ionic current blockage to field-effect-transistor (FET) sensors. A newly released protein nanopore sequencer has shown encouraging potential that nanopore sequencing will ultimately fulfill the gold standards. In this review, we address advances, challenges, and possible solutions of nanopore sequencing according to these standards. PMID:25610451

  9. Dealloying-driven nanoporous palladium with superior electrochemical actuation performance.

    PubMed

    Zhang, Jie; Bai, Qingguo; Zhang, Zhonghua

    2016-04-01

    Metal-hydrogen (in particular, Pd-H) interactions have been receiving considerable attention over the past 150 years within the scope of hydrogen storage, catalytic hydrogenation, hydrogen embrittlement and hydrogen-induced interfacial failure. Here, for the first time, we show that the coupling of hydrogen adsorption and absorption could trigger giant reversible strain in bulk nanoporous Pd (np-Pd) in a weakly adsorbed NaF electrolyte. The bulk np-Pd with a hierarchically porous structure and a ligament/channel size of ∼10 nm was fabricated using a dealloying strategy with compositional/structural design of the precursor. The np-Pd actuator exhibits a giant reversible strain of up to 3.28% (stroke of 137.8 μm), which is a 252% enhancement in comparison to the state-of-the-art value of 1.3% in np-AuPt. The strain rate (∼10(-5) s(-1)) of np-Pd is two orders of magnitude higher than that of current metallic actuators. Moreover, the volume-/mass-specific strain energy density (10.71 MJ m(-3)/3811 J kg(-1)) of np-Pd reaches the highest level compared with that of previously reported actuator materials. The outstanding actuation performance of np-Pd could be attributed to the coupling of hydrogen adsorption/absorption and its unique hierarchically nanoporous structure. Our findings provide valuable information for the design of novel high-performance metallic actuators. PMID:26975834

  10. Device properties of nanopore PN junction Si for photovoltaic application

    NASA Astrophysics Data System (ADS)

    Jin, Hyunjong; Chang, Te Wei; Liu, Logan Gang

    2011-09-01

    Improvement of energy conversion efficiency of solar cells has led to innovative approaches, in particular the introduction of nanopillar photovoltaics [1]. Previous work on nanopillar Si photovoltaic has shown broadband reduction in optical reflection and enhancement of absorption [2]. Radial or axial PN junctions [3, 4] have been of high interest for improved photovoltaic devices. However, with the PN junction incorporated as part of the pillar, the discreteness of individual pillar requires additional conductive layer that would electrically short the top of each pillar for efficient carrier extraction. The fragile structure of the surface pillars would also require a protection layer for possible mechanical scratch to prevent pillars from breaking. Any additional layer that is applied, either for electrical contact or for mechanical properties may introduce additional recombination sites and also reduce the actual light absorption by the photovoltaic material. In this paper, nanopore Si photovoltaics that not only provides the advantages but also addresses the challenges of nanopillers is demonstrated. PN junction substrate of 250 nm thick N-type polycrystalline Si on P-type Si wafer is prepared. The nanopore structure is formed by using anodized aluminum oxide (AAO) as an etching mask against deep reactive ionic etching (DRIE). The device consists of semi-ordered pores of ~70 nm diameter.

  11. Sulfonated nanoporous colloidal films and membranes

    NASA Astrophysics Data System (ADS)

    Smith, Joanna Jane

    The objective of this thesis is to describe the preparation and investigation of a new class of proton-conducting membrane materials, namely, nanoporous colloidal membranes whose proton conductivity results from the nanopore surface modification with organic molecules carrying acid functionalities. Both the proton transport and ion transport were studied in nanoporous silica colloidal crystals that were surface modified with sulfonic groups. First, the transport of ions was studied through sulfonated silica colloidal films that were supported on platinum electrodes using cyclic voltammetry. The surface of self-assembled nanoporous silica colloidal crystalline films was sulfonated using 1,3-propanesultone. We found that the flux of anions through the sulfonated colloidal films is reduced, while the flux of cations is increased, compared to the unmodified colloidal films. Second, the proton transport in free-standing assemblies of surface-sulfonated silica nanospheres, either randomly packed or self-assembled into a close-packed arrangement, were studied. It was demonstrated that colloidal assemblies prepared using surface-sulfonated silica nanospheres posses proton conductivity that depends on the ordering of the material, temperature and relative humidity. Based on the comparison between the close-packed and disordered assemblies made of the same spheres, we conclude that the increase in structural organization of the self-assembled colloidal materials leads to increased proton conductivity and better water retention. Next free-standing colloidal membranes with a relatively large area and no mechanical defects were prepared by sintering silica colloidal films. The sintered membranes were then surface rehydroxylated, which restores the surface silanol groups, and then can be chemically modified. Finally, sintered self-assembled nanoporous silica colloidal crystals were modified with poly(sulfopropyl-methacrylate) (pSPM) and poly(stryrenesulfonic acid) (pSSA) brushes

  12. Development and characterization of nanopore system for nano-vesicle analysis

    NASA Astrophysics Data System (ADS)

    Goyal, Gaurav

    Nano-vesicles have recently attracted a lot of attention in research and medical communities and are very promising next-generation drug delivery vehicles. This is due to their biocompatibility, biodegradability and their ability to protect drug cargo and deliver it to site-specific locations, while maintaining the desired pharmacokinetic profile. The interaction of these drug loaded vesicles with the recipient cells via adsorption, endocytosis or receptor mediated internalization involve significant bending and deformation and is governed by mechanical properties of the nano-vesicles. Currently, the mechanical characteristics of nano-vesicles are left unexplored because of the difficulties associated with vesicle analysis at sub-100 nm length scale. The need for a complete understanding of nano-vesicle interaction with each other and the recipient cells warrants development of an analytical tool capable of mechanical investigation of individual vesicles at sub-100 nm scale. This dissertation presents investigation of nano-vesicle deformability using resistive pulse sensing and solid-state nanopore devices. The dissertation is divided into four chapters. Chapter 1 discusses the motivation, specific aims and presents an overview of nanoparticle characterization techniques, resistive pulse sensing background and principles, techniques for fabricating solid-state nanopores, as well the deformation behavior of giant vesicles when placed in electric field. Chapter 2 is dedicated to understanding of the scientific principles governing transport of sub-100 nm particles in dilute solutions. We investigated the translocation of rigid nanoparticles through nanopores at salt concentrations < 50 mM. When using low electrolyte strength, surface effects become predominant and resulted in unconventional current signatures in our experiments. It prompted us to explore the effects of different experimental parameters using Multiphysics simulations, in order to optimize our system

  13. A wavelet-optimized, very high order adaptive grid and order numerical method

    NASA Technical Reports Server (NTRS)

    Jameson, Leland

    1996-01-01

    Differencing operators of arbitrarily high order can be constructed by interpolating a polynomial through a set of data followed by differentiation of this polynomial and finally evaluation of the polynomial at the point where a derivative approximation is desired. Furthermore, the interpolating polynomial can be constructed from algebraic, trigonometric, or, perhaps exponential polynomials. This paper begins with a comparison of such differencing operator construction. Next, the issue of proper grids for high order polynomials is addressed. Finally, an adaptive numerical method is introduced which adapts the numerical grid and the order of the differencing operator depending on the data. The numerical grid adaptation is performed on a Chebyshev grid. That is, at each level of refinement the grid is a Chebvshev grid and this grid is refined locally based on wavelet analysis.

  14. Templated synthesis for highly ordered metal/support nanocomposite materials with catalytic applications

    NASA Astrophysics Data System (ADS)

    Sarkar, Jayashri

    Template synthesis is a powerful method of synthesizing materials with tunable properties. Tailorability of the templates makes it a viable method for high performance material synthesis. Surfactant, polymers and semiconductors have been used as templating tools for a long time. In the present work, we demonstrate the ability to synthesize hexagonally organized porous titania, zirconia and zirconia/titania mixed oxide supports and their respective nanocomposites of Pt from their alkoxide precursors using a highly viscous mixed surfactant template, separating nanoscopic bicontinuous channels of water and isooctane. Oil soluble precursor that eventually forms the support, precipitates at the oil-water interface mimicking the microstructure of the template. Subsequent reduction of Pt precursor in the aqueous nanochannels decorates the surface of the macropore walls with well-separated platinum (Pt) nanoparticles. This technique enables us to synthesize two components in a single template system by utilizing both oil and water phases. The composite formed possess a bimodal pore size distribution with one mean pore size ˜3.5nm (nanopores) and the other in the larger mean pore diameter regions ˜100nm-2mum (macropores), depending on the oxide support. Because of the decreased mass transfer resistance provided by the ordered and interconnected macropores in the support, the Pt/TiO2 nanocomposite exhibits a significantly higher carbon monoxide oxidation efficiency than that obtained with a commercial support that has a 4-fold larger specific surface area (at equivalent Pt loadings). We further demonstrate that simple changes in the post-synthesis processing can improve the properties of the material. Altering the drying technique and calcination temperature result in a substantial improvement in the specific surface area of the support material making them better than or comparable to the commercial support materials. We are able to synthesize materials with very low Pt

  15. Detection of short single-strand DNA homopolymers with ultrathin S i3N4 nanopores

    NASA Astrophysics Data System (ADS)

    Ma, Jian; Qiu, Yinghua; Yuan, Zhishan; Zhang, Yin; Sha, Jingjie; Liu, Lei; Sun, Litao; Ni, Zhonghua; Yi, Hong; Li, Deyu; Chen, Yunfei

    2015-08-01

    A series of nanopores with diameters ranging from 2.5 to 63 nm are fabricated on a reduced S i3N4 membrane by focused ion beam and high energy electron beam. Through measuring the blocked ionic currents for DNA strands threading linearly through those solid-state nanopores, it is found that the blockade ionic current is proportional to the square of the hydrodynamic diameter of the DNA strand. With the nanopore diameter reduced to be comparable with that of DNA strands, the hydrodynamic diameter of the DNA becomes smaller, which is attributed to the size confinement effects. The duration time for the linear DNA translocation events increases monotonically with the nanopore length. By comparing the spatial configurations of DNA strands through nanopores with different diameters, it is found that the nanopore with large diameter has enough space to allow the DNA strand to translocate through with complex conformation. With the decrease of the nanopore diameter, the folded part of the DNA is prone to be straightened by the nanopore, which leads to the increase in the occurrence frequency of the linear DNA translocation events. Reducing the diameter of the nanopore to 2.5 nm allows the detection and discrimination of three nucleotide "G" and three nucleotide "T" homopolymer DNA strands based on differences in their physical dimensions.

  16. Tuneable graphene nanopores for single biomolecule detection.

    PubMed

    Al-Dirini, Feras; Mohammed, Mahmood A; Hossain, Md Sharafat; Hossain, Faruque M; Nirmalathas, Ampalavanapillai; Skafidas, Efstratios

    2016-05-21

    Solid-state nanopores are promising candidates for next generation DNA and protein sequencing. However, once fabricated, such devices lack tuneability, which greatly restricts their biosensing capabilities. Here we propose a new class of solid-state graphene-based nanopore devices that exhibit a unique capability of self-tuneability, which is used to control their conductance, tuning it to levels comparable to the changes caused by the translocation of a single biomolecule, and hence, enabling high detection sensitivities. Our presented quantum simulation results suggest that the smallest amino acid, glycine, when present in water and in an aqueous saline solution can be detected with high sensitivity, up to a 90% change in conductance. Our results also suggest that passivating the device with nitrogen, making it an n-type device, greatly enhances its sensitivity, and makes it highly sensitive to not only the translocation of a single biomolecule, but more interestingly to intramolecular electrostatics within the biomolecule. Sensitive detection of the carboxyl group within the glycine molecule, which carries a charge equivalent to a single electron, is achieved with a conductance change that reaches as high as 99% when present in an aqueous saline solution. The presented findings suggest that tuneable graphene nanopores, with their capability of probing intramolecular electrostatics, could pave the way towards a new generation of single biomolecule detection devices. PMID:27171594

  17. Tuneable graphene nanopores for single biomolecule detection

    NASA Astrophysics Data System (ADS)

    Al-Dirini, Feras; Mohammed, Mahmood A.; Hossain, Md Sharafat; Hossain, Faruque M.; Nirmalathas, Ampalavanapillai; Skafidas, Efstratios

    2016-05-01

    Solid-state nanopores are promising candidates for next generation DNA and protein sequencing. However, once fabricated, such devices lack tuneability, which greatly restricts their biosensing capabilities. Here we propose a new class of solid-state graphene-based nanopore devices that exhibit a unique capability of self-tuneability, which is used to control their conductance, tuning it to levels comparable to the changes caused by the translocation of a single biomolecule, and hence, enabling high detection sensitivities. Our presented quantum simulation results suggest that the smallest amino acid, glycine, when present in water and in an aqueous saline solution can be detected with high sensitivity, up to a 90% change in conductance. Our results also suggest that passivating the device with nitrogen, making it an n-type device, greatly enhances its sensitivity, and makes it highly sensitive to not only the translocation of a single biomolecule, but more interestingly to intramolecular electrostatics within the biomolecule. Sensitive detection of the carboxyl group within the glycine molecule, which carries a charge equivalent to a single electron, is achieved with a conductance change that reaches as high as 99% when present in an aqueous saline solution. The presented findings suggest that tuneable graphene nanopores, with their capability of probing intramolecular electrostatics, could pave the way towards a new generation of single biomolecule detection devices.

  18. Conversion of Isoprenoid Oil by Catalytic Cracking and Hydrocracking over Nanoporous Hybrid Catalysts

    PubMed Central

    Kimura, Toshiyuki; Liu, Chen; Li, Xiaohong; Maekawa, Takaaki; Asaoka, Sachio

    2012-01-01

    In order to produce petroleum alternatives from biomass, a significant amount of research has been focused on oils from microalgae due to their origin, which would not affect food availability. Nanoporous hybrid catalysts composed of ns Al2O3 and zeolites have been proven to be very useful compared to traditional catalysts in hydrotreating (HT), hydrocracking (HC), and catalytic cracking (CC) of large molecules. To evaluate the reaction scheme and products from model isoprenoid compounds of microalgae oil, nanoporous hybrid catalyst technologies (CC: ns Al2O3/H-USY and ns Al2O3/H-GaAlMFI; HC: [Ni-Mo/γ-Al2O3]/ns Al2O3/H-beta) were studied. The major product from CC on ns Al2O3/H-USY was highly aromatic gasoline, while the product from HC was half-isoparaffinic/olefinic kerosene. Although more than 50 wt% of the products from HT/CC on the USY catalyst was liquefied petroleum gas due to overcracking, the product from HT/CC on the MFI catalyst was high-octane-number gasoline. Delightfully, the product from HT/HC was kerosene and its average number was 11, with more than 80 wt% being isoparaffinic. As a result, it was demonstrated that hydrotreating may convert isoprenoid oil from microalgae over nanoporous hybrid catalysts into a variety of products. PMID:22791962

  19. Conversion of isoprenoid oil by catalytic cracking and hydrocracking over nanoporous hybrid catalysts.

    PubMed

    Kimura, Toshiyuki; Liu, Chen; Li, Xiaohong; Maekawa, Takaaki; Asaoka, Sachio

    2012-01-01

    In order to produce petroleum alternatives from biomass, a significant amount of research has been focused on oils from microalgae due to their origin, which would not affect food availability. Nanoporous hybrid catalysts composed of ns Al₂O₃ and zeolites have been proven to be very useful compared to traditional catalysts in hydrotreating (HT), hydrocracking (HC), and catalytic cracking (CC) of large molecules. To evaluate the reaction scheme and products from model isoprenoid compounds of microalgae oil, nanoporous hybrid catalyst technologies (CC: ns Al₂O₃/H-USY and ns Al₂O₃/H-GaAlMFI; HC: [Ni-Mo/γ-Al₂O₃]/ns Al₂O₃/H-beta) were studied. The major product from CC on ns Al₂O₃/H-USY was highly aromatic gasoline, while the product from HC was half-isoparaffinic/olefinic kerosene. Although more than 50 wt% of the products from HT/CC on the USY catalyst was liquefied petroleum gas due to overcracking, the product from HT/CC on the MFI catalyst was high-octane-number gasoline. Delightfully, the product from HT/HC was kerosene and its average number was 11, with more than 80 wt% being isoparaffinic. As a result, it was demonstrated that hydrotreating may convert isoprenoid oil from microalgae over nanoporous hybrid catalysts into a variety of products. PMID:22791962

  20. High-order disclinations in space-variant polarization

    NASA Astrophysics Data System (ADS)

    Khajavi, B.; Galvez, E. J.

    2016-08-01

    We present the investigation of high-order disinclination patterns in the spatially variable polarization of a light beam. The beam was prepared by encoding two distinct high-order optical vortices on each of the circular polarization components of the beam. As a consequence, we were able to produce high-index lemon and star patterns, which have positive and negative indices, respectively. By varying the asymmetry of one of the vortices we were able to transform one symmetric pattern (lemon or star) into another (lemon or star). With one exception, monstar patterns always appear for specific ranges of asymmetry regardless of the end symmetric patterns. Mapping of all disclinations within each case is contained in a spherical space, where monstar regions are cusp-shaped. We found that high-order monstar patterns can have positive or negative index.

  1. CoreSVM: a generalized high-order spectral volume method bearing Conservative Order RElease

    NASA Astrophysics Data System (ADS)

    Lamouroux, Raphael; Gressier, Jeremie; Joly, Laurent; Grondin, Gilles

    2014-11-01

    The spectral volume method (SVM) introduced by Wang in 2002 is based on a compact polynomial reconstruction where the interpolation's degree is driven by the partition of the spectral volumes. We propose a generalization of the SVM which releases the polynomial degree from this constraint and more importantly that allows to resort to any polynomial order inferior to the regular stencil order without changing the original spectral volume partition. Using one-dimensional advection and Burgers equation, we prove that the proposed extended method exhibits versatile high-order convergence together with conservativity properties. This new method is thus named the CoreSVM for Conservative Order-REleased SVM and we therefore explore its potential towards the numerical simulation of stiff problems. It is stressed that CoreSVM is indeed particularly suited to handle discontinuities, as the order-reduction serves to damp the numerical oscillations due to Runge's phenomenon. To ensure computational stability, local p-coarsening is used to obtain the highest adequate polynomial degree. It is advocated finally that, since the CoreSVM sets the polynomial order adaptation free from any stencil changes, these features do not come at the expense of any extra remeshing or data adaptation cost. Part of this research was funded by the French DGA.

  2. Enzyme Reactions in Nanoporous, Picoliter Volume Containers

    PubMed Central

    Siuti, Piro; Retterer, Scott T.; Choi, Chang-Kyoung; Doktycz, Mitchel J.

    2012-01-01

    Advancements in nanoscale fabrication allow creation of small volume reaction containers that can facilitate the screening and characterization of enzymes. A porous, ~19 pL volume vessel has been used in this work to carry out enzyme reactions under varying substrate concentrations. Assessment of small molecule and Green Fluorescent Protein diffusion from the vessels indicates that pore sizes on order of 10 nm can be obtained, allowing capture of proteins and diffusive exchange of small molecules. Glucose oxidase and horseradish peroxidase can be contained in these structures and diffusively fed with a solution containing glucose and the fluorogenic substrate Amplex Red™ through the engineered nanoscale pore structure. Fluorescent microscopy was used to monitor the reaction, which was carried out under microfluidic control. Kinetic characteristics of the enzyme (Km and Vmax) were evaluated and compared with results from conventional scale reactions. These picoliter, nanoporous containers can facilitate quick determination of enzyme kinetics in microfluidic systems without the requirement of surface tethering and can be used for applications in drug discovery, clinical diagnostics and high-throughput screening. PMID:22148720

  3. Nano-porous calcium phosphate balls.

    PubMed

    Kovach, Ildyko; Kosmella, Sabine; Prietzel, Claudia; Bagdahn, Christian; Koetz, Joachim

    2015-08-01

    By dropping a NaH2PO4·H2O precursor solution to a CaCl2 solution at 90°C under continuous stirring in presence of two biopolymers, i.e. gelatin (G) and chitosan (C), supramolecular calcium phosphate (CP) card house structures are formed. Light microscopic investigations in combination with scanning electron microscopy show that the GC-based flower-like structure is constructed from very thin CP platelets. Titration experiments indicate that H-bonding between both biopolymers is responsible for the synergistic effect in presence of both polymers. Gelatin-chitosan-water complexes play an important role with regard to supramolecular ordering. FTIR spectra in combination with powder X-ray diffraction show that after burning off all organic components (heating up >600°C) dicalcium and tricalcium phosphate crystallites are formed. From high resolution transmission electron microscopy (HR-TEM) it is obvious to conclude, that individual crystal platelets are dicalcium phosphates, which build up ball-like supramolecular structures. The results reveal that the GC guided crystal growth leads to nano-porous supramolecular structures, potentially attractive candidates for bone repair. PMID:26052107

  4. High order sideband generation in terahertz quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Cavalié, P.; Freeman, J.; Maussang, K.; Strupiechonski, E.; Xu, G.; Colombelli, R.; Li, L.; Davies, A. G.; Linfield, E. H.; Tignon, J.; Dhillon, S. S.

    2013-06-01

    We demonstrate the generation of high order terahertz (THz) frequency sidebands (up to 3rd order) on a near infrared (NIR) optical carrier within a THz quantum cascade laser (QCL). The NIR carrier is resonant with the interband transition of the quantum wells composing the QCL, allowing the nonlinearity to be enhanced and leading to frequency mixing. A phonon depopulation based QCL with a double metal cavity was used to enhance the intracavity power density and to demonstrate the higher order sidebands. The 1st order sideband intensity shows a linear dependence with THz power corresponding to a single THz photon, while the second order sideband has a quadratic dependence implying a two THz photon interaction and hence a third order susceptibility. These measurements are compared to the photoluminescence and the QCL bandstructure to identify the states involved, with the lowest conduction band states contributing the most to the sideband intensity. We also show that the interaction for the second order sideband corresponds to an enhanced direct third order susceptibility χ(3) of ˜7 × 10-16(m/V)2, two orders of magnitude greater than the bulk value.

  5. In-situ growth of porous alumino-silicates and fabrication of nano-porous membranes

    NASA Astrophysics Data System (ADS)

    Kodumuri, Pradeep

    2009-12-01

    Feasibility of depositing continuous films of nano-porous alumino-silicates, primarily zeolites and MCM-41, on metallic and non-metallic substrates was examined with an aim to develop membranes for separation of gaseous mixtures and also for application as hydrogen storage material. Mesoporous silica was deposited in-side the pores of these nano-porous disks with an aim to develop membranes for selective separations. Our study involves supported zeolite film growth on substrates using in-situ hydrothermal synthesis. Faujasite, Silicalite and Mesoporous silica have been grown on various metallic and non-metallic supports. Metallic substrates used for film growth included anodized titanium, sodium hydroxide treated Titanium, Anodized aluminum, and sintered copper. A non-metallic substrate used was nano-porous aluminum oxide. Zeolite film growth was characterized using Scanning Electron Microscope (AMRAY 1820) and High Resolution Transmission electron microscope. Silicalite was found to grow uniformly on all the substrates to form a uniform and closely packed film. Faujasite tends to grow in the form of individual particles which do not inter-grow like silicalite to form a continuous film. Mesoporous silica was found to grow uniformly on anodized aluminum compared to growth on sintered copper and anodized titanium. Mesoporous silica growth on AnodiscRTM was found to cover more than half the surface of the substrate. Commercially obtained AnodiscRTM was found to have cylindrical channels of the pore branching into each other and since we needed pore channels of uniform dimension for Mesoporous silica growth, we have fabricated nano-porous alumina with uniform pore channels. Nano-porous alumina membranes containing uniform distribution of through thickness cylindrical pore channels were fabricated using anodization of aluminum disks. Free-standing nano-porous alumina membranes were used as templates for electro-deposition in order to fabricate nickel and palladium nano

  6. The Observation of Highly Ordered Domains in Membranes with Cholesterol

    SciTech Connect

    Armstrong, Clare L; Marquardt, Drew; Dies, Hannah; Kucerka, Norbert; Yamani, Zahra; Harroun, Thad; Katsaras, John; Shi, A-C; Rheinstadter, Maikel C

    2013-01-01

    Rafts, or functional domains, are transient nano- or mesoscopic structures in the exoplasmic leaflet of the plasma membrane, and are thought to be essential for many cellular processes. Using neutron diffraction and computer modelling, we present evidence for the existence of highly ordered lipid domains in the cholesterol-rich (32.5 mol%) liquid-ordered (lo) phase of dipalmitoylphosphatidylcholine membranes. The liquid ordered phase in one-component lipid membranes has previously been thought to be a homogeneous phase. The presence of highly ordered lipid domains embedded in a disordered lipid matrix implies non-uniform distribution of cholesterol between the two phases. The experimental results are in excellent agreement with recent computer simulations of DPPC/cholesterol complexes [Meinhardt, Vink and Schmid (2013). Proc Natl Acad Sci USA 110(12): 4476 4481], which reported the existence of nanometer size lo domains in a liquid disordered lipid environment.

  7. Theory of intertwined orders in high temperature superconductors

    DOE PAGESBeta

    Fradkin, Eduardo; Tranquada, John M.; Kivelson, Steven A.

    2015-03-26

    The electronic phase diagrams of many highly correlated systems, and in particular the cuprate high temperature superconductors, are complex, with many different phases appearing with similar—sometimes identical—ordering temperatures even as material properties, such as a dopant concentration, are varied over wide ranges. This complexity is sometimes referred to as “competing orders.” However, since the relation is intimate, and can even lead to the existence of new phases of matter such as the putative “pair-density-wave,” the general relation is better thought of in terms of “intertwined orders.” We selectively analyze some of the experiments in the cuprates which suggest that essentialmore » aspects of the physics are reflected in the intertwining of multiple orders—not just in the nature of each order by itself. We also summarize and critique several theoretical ideas concerning the origin and implications of this complexity.« less

  8. The Observation of Highly Ordered Domains in Membranes with Cholesterol

    PubMed Central

    Armstrong, Clare L.; Marquardt, Drew; Dies, Hannah; Kučerka, Norbert; Yamani, Zahra; Harroun, Thad A.; Katsaras, John; Shi, An-Chang; Rheinstädter, Maikel C.

    2013-01-01

    Rafts, or functional domains, are transient nano- or mesoscopic structures in the exoplasmic leaflet of the plasma membrane, and are thought to be essential for many cellular processes. Using neutron diffraction and computer modelling, we present evidence for the existence of highly ordered lipid domains in the cholesterol-rich (32.5 mol%) liquid-ordered () phase of dipalmitoylphosphatidylcholine membranes. The liquid ordered phase in one-component lipid membranes has previously been thought to be a homogeneous phase. The presence of highly ordered lipid domains embedded in a disordered lipid matrix implies non-uniform distribution of cholesterol between the two phases. The experimental results are in excellent agreement with recent computer simulations of DPPC/cholesterol complexes [Meinhardt, Vink and Schmid (2013). Proc Natl Acad Sci USA 110(12): 4476–4481], which reported the existence of nanometer size domains in a liquid disordered lipid environment. PMID:23823623

  9. Theory of intertwined orders in high temperature superconductors

    SciTech Connect

    Fradkin, Eduardo; Tranquada, John M.; Kivelson, Steven A.

    2015-03-26

    The electronic phase diagrams of many highly correlated systems, and in particular the cuprate high temperature superconductors, are complex, with many different phases appearing with similar—sometimes identical—ordering temperatures even as material properties, such as a dopant concentration, are varied over wide ranges. This complexity is sometimes referred to as “competing orders.” However, since the relation is intimate, and can even lead to the existence of new phases of matter such as the putative “pair-density-wave,” the general relation is better thought of in terms of “intertwined orders.” We selectively analyze some of the experiments in the cuprates which suggest that essential aspects of the physics are reflected in the intertwining of multiple orders—not just in the nature of each order by itself. We also summarize and critique several theoretical ideas concerning the origin and implications of this complexity.

  10. Lithium Titanate Confined in Carbon Nanopores for Asymmetric Supercapacitors.

    PubMed

    Zhao, Enbo; Qin, Chuanli; Jung, Hong-Ryun; Berdichevsky, Gene; Nese, Alper; Marder, Seth; Yushin, Gleb

    2016-04-26

    Porous carbons suffer from low specific capacitance, while intercalation-type active materials suffer from limited rate when used in asymmetric supercapacitors. We demonstrate that nanoconfinement of intercalation-type lithium titanate (Li4Ti5O12) nanoparticles in carbon nanopores yielded nanocomposite materials that offer both high ion storage density and rapid ion transport through open and interconnected pore channels. The use of titanate increased both the gravimetric and volumetric capacity of porous carbons by more than an order of magnitude. High electrical conductivity of carbon and the small size of titanate crystals allowed the composite electrodes to achieve characteristic charge and discharge times comparable to that of the electric double-layer capacitors. The proposed composite synthesis methodology is simple, scalable, and applicable for a broad range of active intercalation materials, while the produced composite powders are compatible with commercial electrode fabrication processes. PMID:26950509

  11. Separation of High Order Harmonics with Fluoride Windows

    SciTech Connect

    Allison, Tom; van Tilborg, Jeroen; Wright, Travis; Hertlein, Marcus; Falcone, Roger; Belkacem, Ali

    2010-08-02

    The lower orders produced in high order harmonic generation can be effciently temporally separated into monochromatic pulses by propagation in a Fluoride window while still preserving their femtosecond pulse duration. We present calculations for MgF2, CaF2, and LiF windows for the third, fifth, and seventh harmonics of 800 nm. We demonstrate the use of this simple and inexpensive technique in a femtosecond pump/probe experiment using the fifth harmonic.

  12. Fabricating Nanodots using Lift-Off of a Nanopore Template

    NASA Technical Reports Server (NTRS)

    Yang, Eui-Hyeok; Ramsey, Christopher R.; Bae, Youngsam; Choi, Daniel S.

    2008-01-01

    A process for fabricating a planar array of dots having characteristic dimensions of the order of several nanometers to several hundred nanometers involves the formation and use of a thin alumina nanopore template on a semiconductor substrate. The dot material is deposited in the nanopores, then the template is lifted off the substrate after the dots have been formed. This process is expected to be a basis for development of other, similar nanofabrication processes for relatively inexpensive mass production of nanometerscale optical, optoelectronic, electronic, and magnetic devices. Alumina nanopore templates are self-organized structures that result from anodization of aluminum under appropriate conditions. Alumina nanopore templates have been regarded as attractive for use in fabricating the devices mentioned above, but prior efforts to use alumina nanopore templates for this purpose have not been successful. One reason for the lack of success is that the aspect ratios (ratios between depth and diameter) of the pores have been too large: large aspect ratios can result in blockage of deposition and/or can prevent successful lift-off. The development of the present process was motivated partly by a requirement to reduce aspect ratios to values (of the order of 10) for which there is little or no blockage of deposition and attempts at lift-off are more likely to be successful. The fabrication process is outlined.

  13. Protein conducting nanopores

    NASA Astrophysics Data System (ADS)

    Harsman, Anke; Krüger, Vivien; Bartsch, Philipp; Honigmann, Alf; Schmidt, Oliver; Rao, Sanjana; Meisinger, Christof; Wagner, Richard

    2010-11-01

    About 50% of the cellular proteins have to be transported into or across cellular membranes. This transport is an essential step in the protein biosynthesis. In eukaryotic cells secretory proteins are transported into the endoplasmic reticulum before they are transported in vesicles to the plasma membrane. Almost all proteins of the endosymbiotic organelles chloroplasts and mitochondria are synthesized on cytosolic ribosomes and posttranslationally imported. Genetic, biochemical and biophysical approaches led to rather detailed knowledge on the composition of the translocon-complexes which catalyze the membrane transport of the preproteins. Comprehensive concepts on the targeting and membrane transport of polypeptides emerged, however little detail on the molecular nature and mechanisms of the protein translocation channels comprising nanopores has been achieved. In this paper we will highlight recent developments of the diverse protein translocation systems and focus particularly on the common biophysical properties and functions of the protein conducting nanopores. We also provide a first analysis of the interaction between the genuine protein conducting nanopore Tom40SC as well as a mutant Tom40SC (\\mathrm {S}_{54} \\to E ) containing an additional negative charge at the channel vestibule and one of its native substrates, CoxIV, a mitochondrial targeting peptide. The polypeptide induced a voltage-dependent increase in the frequency of channel closure of Tom40SC corresponding to a voltage-dependent association rate, which was even more pronounced for the Tom40SC S54E mutant. The corresponding dwelltime reflecting association/transport of the peptide could be determined with \\bar {t}_{\\mathrm {off}} \\cong 1.1 ms for the wildtype, whereas the mutant Tom40SC S54E displayed a biphasic dwelltime distribution (\\bar {t}_{\\mathrm {off}}^1 \\cong 0.4 ms \\bar {t}_{\\mathrm {off}}^2 \\cong 4.6 ms).

  14. High-order rogue waves for the Hirota equation

    SciTech Connect

    Li, Linjing; Wu, Zhiwei; Wang, Lihong; He, Jingsong

    2013-07-15

    The Hirota equation is better than the nonlinear Schrödinger equation when approximating deep ocean waves. In this paper, high-order rational solutions for the Hirota equation are constructed based on the parameterized Darboux transformation. Several types of this kind of solutions are classified by their structures. -- Highlights: •The determinant representation of the N-fold Darboux transformation of the Hirota equation. •Properties of the fundamental pattern of the higher order rogue wave. •Ring structure and triangular structure of the higher order rogue waves.

  15. High order ZIP' differencing of convective terms. Memorandum report

    SciTech Connect

    Zalesak, S.T.

    1980-05-08

    The ZIP flux form for differencing the term (wv) sub x, where w is a convected quantity and v is a convective velocity, is observed to be equivalent to differencing the alternative expression wv sub x + w sub x v using centered second order finite differences. Based on this observation, the extension of the ZIP flux concept to arbitrarily high order accuracy is given. Computational examples show the advantage both of the ZIP flux concept itself and of its higher order forms within the context of flux-corrected transport (FCT) algorithms.

  16. Vortices and charge order in high-Tc superconductors

    NASA Astrophysics Data System (ADS)

    Einenkel, Matthias; Meier, Hendrik; Pépin, Catherine; Efetov, Konstantin B.

    2015-03-01

    We theoretically investigate the vortex state of the cuprate high-temperature superconductors in the presence of magnetic fields. Assuming the recently derived nonlinear σ-model for fluctuations in the pseudogap phase, we find that the vortex cores consist of two crossed regions of elliptic shape, in which a static charge order emerges. Charge density wave order manifests itself as satellites to the ordinary Bragg peaks directed along the axes of the reciprocal copper lattice. Quadrupole density wave (bond order) satellites, if seen, are predicted to be along the diagonals. The intensity of the satellites should grow linearly with the magnetic field, in agreement with the result of recent experiments.

  17. Vortices and charge order in high-Tc superconductors

    NASA Astrophysics Data System (ADS)

    Einenkel, M.; Meier, H.; Pépin, C.; Efetov, K. B.

    2014-08-01

    We theoretically investigate the vortex state of the cuprate high-temperature superconductors in the presence of magnetic fields. Assuming the recently derived nonlinear σ-model for fluctuations in the pseudogap phase, we find that the vortex cores consist of two crossed regions of elliptic shape, in which a static charge order emerges. Charge density wave order manifests itself as satellites to the ordinary Bragg peaks directed along the axes of the reciprocal copper lattice. Quadrupole density wave (bond order) satellites, if seen, are predicted to be along the diagonals. The intensity of the satellites should grow linearly with the magnetic field, in agreement with the result of recent experiments.

  18. High order hybrid numerical simulations of two dimensional detonation waves

    NASA Technical Reports Server (NTRS)

    Cai, Wei

    1993-01-01

    In order to study multi-dimensional unstable detonation waves, a high order numerical scheme suitable for calculating the detailed transverse wave structures of multidimensional detonation waves was developed. The numerical algorithm uses a multi-domain approach so different numerical techniques can be applied for different components of detonation waves. The detonation waves are assumed to undergo an irreversible, unimolecular reaction A yields B. Several cases of unstable two dimensional detonation waves are simulated and detailed transverse wave interactions are documented. The numerical results show the importance of resolving the detonation front without excessive numerical viscosity in order to obtain the correct cellular patterns.

  19. A High Order Perturbation Analysis of the Sitnikov Problem

    NASA Astrophysics Data System (ADS)

    Hagel, Johannes; Lhotka, Christoph

    2005-09-01

    The Sitnikov problem is one of the most simple cases of the elliptic restricted three body system. A massless body oscillates along a line (z) perpendicular to a plane (x,y) in which two equally massive bodies, called primary masses, perform Keplerian orbits around their common barycentre with a given eccentricity e. The crossing point of the line of motion of the third mass with the plane is equal to the centre of gravity of the entire system. In spite of its simple geometrical structure, the system is nonlinear and explicitly time dependent. It is globally non integrable and therefore represents an interesting application for advanced perturbative methods. In the present work a high order perturbation approach to the problem was performed, by using symbolic algorithms written in Mathematica. Floquet theory was used to derive solutions of the linearized equation up to 17th order in e. In this way precise analytical expressions for the stability of the system were obtained. Then, applying the Courant and Snyder transformation to the nonlinear equation, algebraic solutions of seventh order in z and e were derived using the method of Poincaré Lindstedt. The enormous amount of necessary computations were performed by extensive use of symbolic programming. We developed automated and highly modularized algorithms in order to master the problem of ordering an increasing number of algebraic terms originating from high order perturbation theory.

  20. Nanoporous PdZr surface alloy as highly active non-platinum electrocatalyst toward oxygen reduction reaction with unique structure stability and methanol-tolerance

    NASA Astrophysics Data System (ADS)

    Duan, Huimei; Xu, Caixia

    2016-06-01

    Nanoporous (NP) PdZr alloy with controllable bimetallic ratio is successfully fabricated by a simple dealloying method. By leaching out the more reactive Al from PdZrAl precursor alloy, NP-PdZr alloy with smaller ligament size was generated, characterized by the nanoscaled interconnected network skeleton and hollow channels extending in all three dimensions. Upon voltammetric scan in acid solution, the dissolution of surface Zr atoms generates the highly active Pd-Zr surface alloy with a nearly pure Pd surface and Pd-Zr alloy core. The NP-Pd80Zr20 surface alloy exhibits markedly enhanced specific and mass activities as well as higher catalytic stability toward oxygen reduction reaction (ORR) compared with NP-Pd and the state-of-the-art Pt/C catalysts. In addition, the NP-Pd80Zr20 surface alloy shows a better selectivity for ORR than methanol in the 0.1 M HClO4 and 0.1 M methanol mixed solution. X-ray photoelectron spectroscopy and density functional theory calculations both demonstrate that the weakened Pd-O bond and improved ORR performances in turn depend on the downshifted d-band center of Pd due to the alloying Pd with Zr (20 at.%). The as-made NP-PdZr alloy holds prospective applications as a cathode electrocatalyst in fuel-cell-related technologies with the advantages of superior overall ORR performances, unique structure stability, and easy preparation.

  1. Mechanisms of material removal and mass transport in focused ion beam nanopore formation

    SciTech Connect

    Das, Kallol Johnson, Harley T.; Freund, Jonathan B.

    2015-02-28

    Despite the widespread use of focused ion beam (FIB) processing as a material removal method for applications ranging from electron microscope sample preparation to nanopore processing for DNA sequencing, the basic material removal mechanisms of FIB processing are not well understood. We present the first complete atomistic simulation of high-flux FIB using large-scale parallel molecular dynamics (MD) simulations of nanopore fabrication in freestanding thin films. We focus on the root mechanisms of material removal and rearrangement and describe the role of explosive boiling in forming nanopores. FIB nanopore fabrication is typically understood to occur via sputter erosion. This can be shown to be the case in low flux systems, where individual ion impacts are sufficiently separated in time that they may be considered as independent events. But our detailed MD simulations show that in high flux FIB processing, above a threshold level at which thermal effects become significant, the primary mechanism of material removal changes to a significantly accelerated, thermally dominated process. Under these conditions, the target is heated by the ion beam faster than heat is conducted away by the material, leading quickly to melting, and then continued heating to nearly the material critical temperature. This leads to explosive boiling of the target material with spontaneous bubble formation and coalescence. Mass is rapidly rearranged at the atomistic scale, and material removal occurs orders of magnitude faster than would occur by simple sputtering. While the phenomenology is demonstrated computationally in silicon, it can be expected to occur at lower beam fluxes in other cases where thermal conduction is suppressed due to material properties, geometry, or ambient thermal conditions.

  2. Formation of nanoporous aerogels from wheat starch.

    PubMed

    Ubeyitogullari, Ali; Ciftci, Ozan N

    2016-08-20

    Biodegradable nanoporous aerogels were obtained from wheat starch using a simple and green method based on supercritical carbon dioxide (SC-CO2) drying. Effects of processing parameters (temperature, wheat starch concentration and mixing rate during gelatinization; temperature, pressure, and flow rate of CO2, during SC-CO2 drying) on the aerogel formation were investigated, and optimized for the highest surface area and smallest pore size of the aerogels. At the optimized conditions, wheat starch aerogels had surface areas between 52.6-59.7m(2)/g and densities ranging between 0.05-0.29g/cm(3). The average pore size of the starch aerogels was 20nm. Starch aerogels were stable up to 280°C. Due to high surface area and nanoporous structure, wheat starch aerogels are promising carrier systems for bioactives and drugs in food and pharmaceutical industries. PMID:27178916

  3. Atomic short-range order and incipient long-range order in high-entropy alloys

    NASA Astrophysics Data System (ADS)

    Singh, Prashant; Smirnov, A. V.; Johnson, D. D.

    2015-06-01

    Within density-functional theory, we apply an electronic-structure-based thermodynamic theory to calculate short-ranged order (SRO) in homogeneously disordered substitutional N -component alloys, and its electronic origin. Using the geometric properties of an (N -1 ) simplex that describes the Gibbs (compositional) space, we derive the analytic transform of the SRO eigenvectors that provides a unique description of high-temperature SRO in N -component alloys and the incipient low-temperature long-range order. We apply the electronic-based thermodynamic theory and the new general analysis to ternaries (A 1 Cu-Ni-Zn and A 2 Nb-Al-Ti) for validation, and then to quinary Al-Co-Cr-Fe-Ni high-entropy alloys for predictive assessment.

  4. Efficient Low Dissipative High Order Schemes for Multiscale MHD Flows

    NASA Astrophysics Data System (ADS)

    Sjoegreen, Bjoern; Yee, Helen C.

    2002-11-01

    Accurate numerical simulations of complex multiscale compressible viscous flows, especially high speed turbulence combustion and acoustics, demand high order schemes with adaptive numerical dissipation controls. Standard high resolution shock-capturing methods are too dissipative to capture the small scales and/or long-time wave propagations without extreme grid refinements and small time steps. An integrated approach for the control of numerical dissipation in high order schemes for the compressible Euler and Navier-Stokes equations has been developed and verified by the authors and collaborators. These schemes are suitable for the problems in question. Basically, the scheme consists of sixth-order or higher non-dissipative spatial difference operators as the base scheme. To control the amount of numerical dissipation, multiresolution wavelets are used as sensors to adaptively limit the amount and to aid the selection and/or blending of the appropriate types of numerical dissipation to be used. Magnetohydrodynamics (MHD) waves play a key role in drag reduction in highly maneuverable high speed combat aircraft, in space weather forecasting, and in the understanding of the dynamics of the evolution of our solar system and the main sequence stars. Although there exist a few well-studied second and third-order high-resolution shock-capturing schemes for the MHD in the literature, these schemes are too diffusive and not practical for turbulence/combustion MHD flows. On the other hand, extension of higher than third-order high-resolution schemes to the MHD system of equations is not straightforward. Unlike the hydrodynamic equations, the inviscid MHD system is non-strictly hyperbolic with non-convex fluxes. The wave structures and shock types are different from their hydrodynamic counterparts. Many of the non-traditional hydrodynamic shocks are not fully understood. Consequently, reliable and highly accurate numerical schemes for multiscale MHD equations pose a great

  5. High-order fluorescence fluctuation analysis of model protein clusters.

    PubMed Central

    Palmer, A G; Thompson, N L

    1989-01-01

    The technique of high-order fluorescence fluctuation autocorrelation for detecting and characterizing protein oligomers was applied to solutions containing two fluorescent proteins in which the more fluorescent proteins were analogues for clusters of the less fluorescent ones. The results show that the model protein clusters can be detected for average numbers of observed subunits (free monomers plus monomers in oligomers) equal to 10-100 and for relative fluorescent yields that correspond to oligomers as small as trimers. High-order fluorescent fluctuation analysis may therefore be applicable to cell surface receptor clusters in natural or model membranes. PMID:2548201

  6. Ductile long range ordered alloys with high critical ordering temperature and wrought articles fabricated therefrom

    DOEpatents

    Liu, Chain T.; Inouye, Henry

    1979-01-01

    Malleable long range ordered alloys having high critical ordering temperatures exist in the V(Fe, Co).sub.3 and V(Fe, Co, Ni).sub.3 systems. These alloys have the following compositions comprising by weight: 22-23% V, 14-30% Fe, and the remainder Co or Co and Ni with an electron density no more than 7.85. The maximum combination of high temperature strength, ductility and creep resistance are manifested in the alloy comprising by weight 22-23% V, 14-20% Fe and the remainder Co and having an atomic composition of V(Fe .sub.0.20-0.26 C Co.sub.0.74-0.80).sub.3. The alloy comprising by weight 22-23% V, 16-17% Fe and 60-62% Co has excellent high temperature properties. The alloys are fabricable into wrought articles by casting, deforming, and annealing for sufficient time to provide ordered structure.

  7. Localized functionalization of single nanopores

    SciTech Connect

    Nilsson, J; Lee, J I; Ratto, T V; Letant, S E

    2005-09-12

    We demonstrate the localization of chemical functionality at the entrance of single nanopores for the first time by using the controlled growth of an oxide ring. Nanopores were fabricated by Focused Ion Beam machining on silicon platforms, locally derivatized by ion beam assisted oxide deposition, and further functionalized with DNA probes via silane chemistry. Ionic current recorded through single nanopores at various stages of the fabrication process demonstrated that the apertures can be locally functionalized with DNA probes. Future applications for this functional platform include the selective detection of biological organisms and molecules by ionic current blockade measurements.

  8. Theoretical study of intermolecular interactions in nanoporous networks on boron doped silicon surface

    NASA Astrophysics Data System (ADS)

    Boukari, Khaoula; Duverger, Eric; Hanf, Marie-Christine; Stephan, Régis; Sonnet, Philippe

    2014-11-01

    Supramolecular networks on a doped boron silicon surface under ultra high vacuum (UHV) have been recently obtained (Makoudi et al., 2013). The used molecule contains different end-groups, bearing either bromine, iodine or hydrogen atoms denoted 1,3,5-tri(4‧-bromophenyl)benzene (TBB), 1,3,5-tri(4-iodophenyl)benzene (TIB) and 1,3,5-triphenyl-benzene (THB). To explain the formation of the nanoporous structures, interactions of the type aryl-X⋯H hydrogen bonds (X being a halogen atom) have been proposed. In order to obtain a complete insight of the stabilizing interaction in these networks adsorbed on the Si(1 1 1)√3x√3R30°-boron surface, we present a full density-functional-theory study taking the van der Waals interactions into account. We investigated the energetic and structural properties of three different nanoporous networks constituted by TBB, TIB and THB molecules. The electronic studies allow us to identify hydrogen bond and dipole-dipole intermolecular interactions in the supramolecular halogen networks, whereas only dipole-dipole interactions are present in the 1,3,5-triphenyl-benzene nanoporous network.

  9. Acoustic centering of sources with high-order radiation patterns.

    PubMed

    Shabtai, Noam R; Vorländer, Michael

    2015-04-01

    Surrounding spherical microphone arrays have recently been used in order to model the radiation pattern of acoustic sources that are assumed to be at the center of the array. Source centering algorithms are applied to the measurements in order to reduce the negative effect of acoustic source misalignment with regard to the physical center of the microphone array. Recent works aim to minimize the energy that is contained in the high-order coefficients of the radiation pattern in the spherical harmonics domain, in order to directly address the problem of increased order and spatial aliasing resulted by this misalignment. However, objective functions which directly minimize the norm of these coefficients were shown to be convex only when employed on sources with low-order radiation patterns. This work presents a source centering algorithm that operates on plane sections and aims to achieve a convex objective function on every plane section. The results of the proposed algorithm are shown to be more convex than the previous algorithms for sources with higher-order radiation pattern, usually at higher frequencies. PMID:25920846

  10. Quantum interference of high-order harmonics from mixed gases

    NASA Astrophysics Data System (ADS)

    González-Fernández, A.; Velarde, P.

    2016-08-01

    We present a theoretical study about the interference of the harmonics generated by a mixture of two gases, He-Ne. Our model is based on the electron quantum paths, a discrete number of electron trajectories, and continuum-bound transitions. A laser with intensity around 1014W/cm2 that interacts with a mixture of gases, He-Ne, produces an interference that is destructive at the low-order harmonics and oscillates between constructive and destructive near to cutoff. This destructive interference at high-order harmonics may be used to explore other transitions, which are currently hidden. At low-order harmonic frequencies, our numerical results are in very good agreement with experimental data. At higher-order harmonics, where there are no experimental data, comparison is with a Schrödinger solver.

  11. Massively parallel high-order combinatorial genetics in human cells

    PubMed Central

    Wong, Alan S L; Choi, Gigi C G; Cheng, Allen A; Purcell, Oliver; Lu, Timothy K

    2016-01-01

    The systematic functional analysis of combinatorial genetics has been limited by the throughput that can be achieved and the order of complexity that can be studied. To enable massively parallel characterization of genetic combinations in human cells, we developed a technology for rapid, scalable assembly of high-order barcoded combinatorial genetic libraries that can be quantified with high-throughput sequencing. We applied this technology, combinatorial genetics en masse (CombiGEM), to create high-coverage libraries of 1,521 two-wise and 51,770 three-wise barcoded combinations of 39 human microRNA (miRNA) precursors. We identified miRNA combinations that synergistically sensitize drug-resistant cancer cells to chemotherapy and/or inhibit cancer cell proliferation, providing insights into complex miRNA networks. More broadly, our method will enable high-throughput profiling of multifactorial genetic combinations that regulate phenotypes of relevance to biomedicine, biotechnology and basic science. PMID:26280411

  12. Atomic layer deposition of TiO2 thin films on nanoporous alumina templates: Medical applications

    NASA Astrophysics Data System (ADS)

    Narayan, Roger J.; Monteiro-Riviere, Nancy A.; Brigmon, Robin L.; Pellin, Michael J.; Elam, Jeffrey W.

    2009-06-01

    Nanostructured materials may play a significant role in controlled release of pharmacologic agents for treatment of cancer. Many nanoporous polymer materials are inadequate for use in drug delivery. Nanoporous alumina provides several advantages over other materials for use in controlled drug delivery and other medical applications. Atomic layer deposition was used to coat all the surfaces of a nanoporous alumina membrane in order to reduce the pore size in a controlled manner. Neither the 20 nm nor the 100 nm TiO2-coated nanoporous alumina membranes exhibited statistically lower viability compared to the uncoated nanoporous alumina membrane control materials. Nanostructured materials prepared using atomic layer deposition may be useful for delivering a pharmacologic agent at a precise rate to a specific location in the body. These materials may serve as the basis for “smart” drug delivery devices, orthopedic implants, or self-sterilizing medical devices.

  13. A New Low Dissipative High Order Schemes for MHD Equations

    NASA Technical Reports Server (NTRS)

    Yee, H. C.; Sjoegreen, Bjoern; Mansour, Nagi (Technical Monitor)

    2002-01-01

    The goal of this talk is to extend our recently developed highly parallelizable nonlinear stable high order schemes for complex multiscale hydrodynamic applications to the viscous MHD equations. These schemes employed multiresolution wavelets as adaptive numerical dissipation controls to limit the amount and to aid the selection and/or blending of the appropriate types of dissipation to be used. The new scheme is formulated for both the conservative and non-conservative form of the MHD equations in curvilinear grids.

  14. Automated Approach to Very High-Order Aeroacoustic Computations. Revision

    NASA Technical Reports Server (NTRS)

    Dyson, Rodger W.; Goodrich, John W.

    2001-01-01

    Computational aeroacoustics requires efficient, high-resolution simulation tools. For smooth problems, this is best accomplished with very high-order in space and time methods on small stencils. However, the complexity of highly accurate numerical methods can inhibit their practical application, especially in irregular geometries. This complexity is reduced by using a special form of Hermite divided-difference spatial interpolation on Cartesian grids, and a Cauchy-Kowalewski recursion procedure for time advancement. In addition, a stencil constraint tree reduces the complexity of interpolating grid points that am located near wall boundaries. These procedures are used to develop automatically and to implement very high-order methods (> 15) for solving the linearized Euler equations that can achieve less than one grid point per wavelength resolution away from boundaries by including spatial derivatives of the primitive variables at each grid point. The accuracy of stable surface treatments is currently limited to 11th order for grid aligned boundaries and to 2nd order for irregular boundaries.

  15. Attosecond Pulse Trains Using High-Order Harmonics

    SciTech Connect

    Antoine, P.; LHuillier, A.; Lewenstein, M.

    1996-08-01

    We demonstrate that high-order harmonics generated by an atom in intense laser field form trains of ultrashort pulses corresponding to different trajectories of electrons that tunnel out of the atom and recombine. Propagation in an atomic jet allows us to select one of these trajectories, leading to a train of pulses of extremely short duration. {copyright} {ital 1996 The American Physical Society.}

  16. Input cavity for high-order asymmetric-mode gyroklystron

    NASA Astrophysics Data System (ADS)

    Danilov, Yu. Yu.

    2012-06-01

    A new input cavity design for a high-order asymmetric-mode gyroklystron is proposed. Methods of the selective excitation of a resonant mode with a rotating field structure and the prevention of cavity self-excitation at harmonics of the gyrofrequency are proposed. Results of experimental investigation of the H711 mode cavity for a multimegawatt pulsed gyroklystron are presented.

  17. Fabrication of Low Noise Borosilicate Glass Nanopores for Single Molecule Sensing

    PubMed Central

    Bafna, Jayesh A.; Soni, Gautam V.

    2016-01-01

    We show low-cost fabrication and characterization of borosilicate glass nanopores for single molecule sensing. Nanopores with diameters of ~100 nm were fabricated in borosilicate glass capillaries using laser assisted glass puller. We further achieve controlled reduction and nanometer-size control in pore diameter by sculpting them under constant electron beam exposure. We successfully fabricate pore diameters down to 6 nm. We next show electrical characterization and low-noise behavior of these borosilicate nanopores and compare their taper geometries. We show, for the first time, a comprehensive characterization of glass nanopore conductance across six-orders of magnitude (1M-1μM) of salt conditions, highlighting the role of buffer conditions. Finally, we demonstrate single molecule sensing capabilities of these devices with real-time translocation experiments of individual λ-DNA molecules. We observe distinct current blockage signatures of linear as well as folded DNA molecules as they undergo voltage-driven translocation through the glass nanopores. We find increased signal to noise for single molecule detection for higher trans-nanopore driving voltages. We propose these nanopores will expand the realm of applications for nanopore platform. PMID:27285088

  18. A universal model for nanoporous carbon supercapacitors

    SciTech Connect

    Huang, Jingsong; Sumpter, Bobby G; Meunier, Vincent

    2009-01-01

    Supercapacitors based on nanoporous carbon materials, commonly called electric double-layer capacitors (EDLCs), are emerging as a novel type of energy-storage device with the potential to substitute batteries in applications that require high power densities. Nanoporous carbon supercapacitors are generally viewed as a parallel-plate capacitor since supercapacitors store energy by charge separation in an electric double layer formed at the electrode/electrolyte interface. The EDLC model has been used to characterize the energy storage of supercapacitors for decades. We comment in this chapter on the shortcomings of the EDLC model when applied to nanoporous carbon supercapacitors. In response to the latest experimental breakthrough in nanoporous carbon supercapacitors, we have proposed a heuristic model that takes pore curvature into account as a replacement for the EDLC model. When the pore size is in the mesopore regime (2 50 nm), electrolyte counterions enter mesoporous carbons and approach the pore wall to form an electric double-cylinder capacitor (EDCC); in the micropore regime (< 2 nm), solvated/desolvated counterions line up along the pore axis to form an electric wire-in-cylinder capacitor (EWCC). In the macropore regime (> 50 nm), where pores are large enough so that pore curvature is no longer significant, the EDCC model can be reduced to the EDLC model. With the backing of experimental data and quantum density functional theory calculations, we have shown that the EDCC/EWCC model is universal for carbon supercapacitors with diverse carbon materials and electrolytes. The strengths and limitations of this new model are discussed. The new model allows the supercapacitor properties to be correlated with pore size, specific surface area, Debye length, electrolyte concentration, dielectric constant, and solute ion size, and may lend support to the systematic optimization of the properties of carbon supercapacitors through experiments.

  19. Direct single ion machining of nanopores.

    SciTech Connect

    Doyle, Barney Lee; Follstaedt, David Martin; Rossi, Paolo; Norman, Adam K.

    2004-10-01

    The irradiation of thin insulating films by high-energy ions (374 MeV Au{sup +25} or 241 MeV I{sup +19}) was used to attempt to form nanometer-size pores through the films spontaneously. Such ions deposit a large amount of energy into the target materials ({approx}20 keV/nm), which significantly disrupts their atomic lattice and sputters material from the surfaces, and might produce nanopores for appropriate ion-material combinations. Transmission electron microscopy was used to examine the resulting ion tracks. Tracks were found in the crystalline oxides quartz, sapphire, and mica. Sapphire and mica showed ion tracks that are likely amorphous and exhibit pits 5 nm in diameter on the surface at the ion entrance and exit points. This suggests that nanopores might form in mica if the film thickness is less than {approx}10 nm. Tracks in quartz showed strain in the matrix around them. Tracks were not found in the amorphous thin films examined: 20 nm-SiN{sub x}, deposited SiOx, fused quartz (amorphous SiO{sub 2}), formvar and 3 nm-C. Other promising materials for nanopore formation were identified, including thin Au and SnO{sub 2} layers.

  20. Accelerating experimental high-order spatial statistics calculations using GPUs

    NASA Astrophysics Data System (ADS)

    Li, Xue; Huang, Tao; Lu, De-Tang; Niu, Cong

    2014-09-01

    High-order spatial statistics have been widely used to describe the spatial phenomena in the field of geology science. Spatial statistics are subject to extremely heavy computational burden for large geostatistical models. To improve the computational efficiency, a parallel approach based on GPU (Graphics Processing Unit) is proposed for the calculation of high-order spatial statistics. The parallel scheme is achieved by utilizing a two-stage method to calculate the replicate of a moment for a given template simultaneously termed as the node-stage parallelism, and transform the spatial moments to cumulants for all lags of a template simultaneously termed as the template-stage parallelism. Also, a series of optimization strategies are proposed to take full advantage of the computational capabilities of GPUs, including the appropriate task allocation to the CUDA (Compute Unified Device Architecture) threads, proper organization of the GPU physical memory, and optimal improvement of the existed parallel routines. Tests are carried out on two training images to compare the performance of the GPU-based method with that of the serial implementation. Error analysis results indicate that the proposed parallel method can generate accurate cumulant maps, and the performance comparisons on various examples show that all the speedups for third-order, fourth-order and fifth-order cumulants calculation are over 17 times.

  1. Anomalies in high-order harmonic generation at relativistic intensities

    SciTech Connect

    Teubner, U.; Foerster, E.; Pretzler, G.; Eidmann, K.; Witte, K.; Schlegel, Th.

    2003-01-01

    High-order harmonic generation from a solid target surface has been investigated using femtosecond laser pulses focused to intensities greater than 10{sup 18} W/cm{sup 2}. The experiments show that the harmonics are very intense, with a conversion efficiency that is one or two orders of magnitude larger than that of harmonics generated in gases. Beside the observation of presently the shortest wavelength harmonics from femtosecond-laser solid target interaction, i.e., down to 22 nm, an anomaly has been observed in the harmonic spectrum. In contrast to the expected well-known continuous 'roll off' of the high-harmonic orders, the harmonic intensity decreases with the increase of harmonic order, but in between shows minima which are significantly less intense than the neighboring harmonics. Furthermore, the order of the harmonic minima depend on target material. Additional calculations using numerical kinetic particle simulations and a simpler oscillating mirror model show that the physical origin of these modulations is an intricate interplay of resonance absorption and ponderomotive force which leads to a complex electron density profile evolution. Furthermore, this is emphasized by a spectral line analysis of the harmonics. In agreement with the theory, broad lines have been observed and, in particular for the harmonics in the minima, a complex interference structure is present.

  2. Photothermoelectric Effects in Nanoporous Silicon.

    PubMed

    Lai, Yu-Sheng; Tsai, Chao-Yang; Chang, Chin-Kai; Huang, Cheng-Yin; Hsiao, Vincent K S; Su, Yuhlong Oliver

    2016-04-01

    The first observation of the photothermoelectric effect in a nanoporous silicon (NPSi) device indicates that the photocurrent is dependent on the position of light-induced local heating from illumination at the Au-electrode/NPSi interface. PMID:26821828

  3. A novel nanoporous graphitic composite.

    PubMed

    Wang, Zheng-Ming; Hoshinoo, Kumiko; Xue, M; Kanoh, Hirofumi; Ooi, Kenta

    2002-08-21

    A novel nanoporous composite containing micrographitic carbon layers is synthesized by preliminarily expanding the interlayer of an oxidized product of graphite using surfactant, followed by Si bridging/pillaring, and carbonization. PMID:12211211

  4. A Very High Order, Adaptable MESA Implementation for Aeroacoustic Computations

    NASA Technical Reports Server (NTRS)

    Dydson, Roger W.; Goodrich, John W.

    2000-01-01

    Since computational efficiency and wave resolution scale with accuracy, the ideal would be infinitely high accuracy for problems with widely varying wavelength scales. Currently, many of the computational aeroacoustics methods are limited to 4th order accurate Runge-Kutta methods in time which limits their resolution and efficiency. However, a new procedure for implementing the Modified Expansion Solution Approximation (MESA) schemes, based upon Hermitian divided differences, is presented which extends the effective accuracy of the MESA schemes to 57th order in space and time when using 128 bit floating point precision. This new approach has the advantages of reducing round-off error, being easy to program. and is more computationally efficient when compared to previous approaches. Its accuracy is limited only by the floating point hardware. The advantages of this new approach are demonstrated by solving the linearized Euler equations in an open bi-periodic domain. A 500th order MESA scheme can now be created in seconds, making these schemes ideally suited for the next generation of high performance 256-bit (double quadruple) or higher precision computers. This ease of creation makes it possible to adapt the algorithm to the mesh in time instead of its converse: this is ideal for resolving varying wavelength scales which occur in noise generation simulations. And finally, the sources of round-off error which effect the very high order methods are examined and remedies provided that effectively increase the accuracy of the MESA schemes while using current computer technology.

  5. Detection of a single enzyme molecule based on a solid-state nanopore sensor

    NASA Astrophysics Data System (ADS)

    Tan, ShengWei; Gu, DeJian; Liu, Hang; Liu, QuanJun

    2016-04-01

    The nanopore sensor as a high-throughput and low-cost technology can detect a single molecule in a solution. In the present study, relatively large silicon nitride (Si3N4) nanopores with diameters of ∼28 and ∼88 nm were fabricated successfully using a focused Ga ion beam. We have used solid-state nanopores with various sizes to detect the single horseradish peroxidase (HRP) molecule and for the first time analyzed single HRP molecular translocation events. In addition, a real-time monitored single enzyme molecular biochemical reaction and a translocation of the product of enzyme catalysis substrates were investigated by using a Si3N4 nanopore. Our nanopore system showed a high sensitivity in detecting single enzyme molecules and a real-time monitored single enzyme molecular biochemical reaction. This method could also be significant for studying gene expression or enzyme dynamics at the single-molecule level.

  6. Limiters for high-order discontinuous Galerkin methods

    NASA Astrophysics Data System (ADS)

    Krivodonova, Lilia

    2007-09-01

    We describe a limiter for the discontinuous Galerkin method that retains as high an order as possible, and does not automatically reduce to first order. The limiter is a generalization of the limiter introduced in [R. Biswas, K. Devine, J.E. Flaherty, Parallel adaptive finite element methods for conservation laws, Applied Numerical Mathematics 14 (1994) 255-284]. We present the one-dimensional case and extend it to two-dimensional problems on tensor-product meshes. Computational results for examples with both smooth and discontinuous solutions are shown.

  7. Effect of Under-Resolved Grids on High Order Methods

    NASA Technical Reports Server (NTRS)

    Yee, H. C.; Sjoegreen, B.; Mansour, Nagi (Technical Monitor)

    2001-01-01

    There has been much discussion on verification and validation processes for establishing the credibility of CFD simulations. Since the early 1990s, many of the aeronautical and mechanical engineering related reference journals mandated that any accepted articles in numerical simulations (without known solutions to compared with) need to perform a minimum of one level of grid refinement and time step reduction. Due to the difficulty in analysis, the effect of under-resolved grids and the nonlinear behavior of available spatial discretizations, are scarcely discussed in the literature. Here, an under-resolved numerical simulation is one where the grid spacing being used is too coarse to resolve the smallest physically relevant scales of the chosen continuum governing equations that are of interest to the numerical modeler. With the advent of new developments in fourth-order or higher spatial schemes, it has become common to regard high order schemes as more accurate, reliable and require less grid points. The danger comes when one tries to perform computations with the coarsest grid possible while still hoping to maintain numerical results sufficiently accurate for complex flows, and especially, data-limited problems. On one hand, high order methods when applies to highly coupled multidimensional complex nonlinear problems might have different stability, convergence and reliability behavior than their well studied low order counterparts, especially for nonlinear schemes such as TVD, MUSCL with limiters, ENO, WENO and discrete Galerkin. On the other hand, high order methods involve more operation counts and systematic grid convergence study can be time consuming and prohibitively expansive. At the same time it is difficult to fully understand or categorize the different nonlinear behavior of finite discretizations, especially at the limits of under-resolution when different types of bifurcation phenomena might occur, depending on the combination of grid spacings, time

  8. High order methods for elliptic problems in plasma physics

    NASA Astrophysics Data System (ADS)

    Pataki, Andras

    In this dissertation, we develop fast high order solvers for two elliptic problems in plasma physics. The first is the Grad-Shafranov equation, a nonlinear elliptic PDE that describes the magnetohydrodynamic equilibrium of three dimensional, axisymmetric plasmas. A high order solver is desirable to ensure the accurate evaluation of derivatives, required both for the computation of physical quantities and for studying perturbations near equilibrium. Using suitable scaling, we transform the problem from cylindrical coordinates to a nonlinear Poisson problem in Cartesian coordinates. We compute the conformal map from the original domain to the unit circle where we build a separation of variables based solver to obtain a high order, accurate solution. A fixed point or eigenvalue outer iteration is used to solve the nonlinear equation. Our second problem is the computation of the Coulomb collision operator that arises in kinetic models of plasmas. The collision operator can be written in terms of two Rosenbluth potentials obtained by solving a Poisson and a biharmonic problem in the velocity variables. For these PDEs we describe a new class of fast solvers in cylindrical coordinates with free-space radiation conditions. By combining integral equation methods in the radial variable with Fourier methods in the angular and z directions, we show that high-order accuracy can be achieved in both the solution and its derivatives. A weak singularity arises in the Fourier transform with respect to z that is handled with special purpose quadratures. Such solvers are ideally suited to the Rosenbluth potentials, since the collision operator is expressed in terms of up to fourth derivatives of the potentials, placing stringent demands on the computational order. Also, since axisymmetry is generally assumed in the velocity variables, the use of cylindrical coordinates reduces the three dimensional problem to a two dimensional computation.

  9. Research on chromatic properties of high order kinoform

    NASA Astrophysics Data System (ADS)

    Wegrzyńska, K.; Rachoń, M.; Doch, M.; Siemion, A.; Suszek, J.; Kołodziejczyk, A.; Sypek, M.

    2014-09-01

    This work is dedicated to the evaluation of the chromatic properties of high order kinoforms. Typical kinoform (of the first order) is a phase only structure having the phase retardation varying in the range 0-2π. Such structures are very commonly used in many practical applications for different ranges of electromagnetic radiation like ultraviolet, visible, infrared, terahertz and millimeter waves. Besides those benefits such structures have one crucial disadvantage - they suffer from big chromatic aberration. This limits their practical application only to the narrowband work, where main wavelength must be well defined (Δλ/λ<<1). This paper presents other type of diffractive structures called high order kinoforms (HOK). They exhibit phase retardation of n2π, where n is an integer number much bigger than 1. Due to this fact they are relatively thin and therefore can be manufactured using laser lithography in thick photoresist (deeply etched). On the other hand they are thick enough to suppress chromatic aberrations. In comparison to the well-known Fresnel lens, the high order kinoform structure has precisely controlled phase retardation between different zones. In the case of the Fresnel lens (known from XVIII/XIX century), phase retardations between different zones are random (designing process is based on the geometrical optics). In the case of the high order kinoform working as the spherical lens - taking into account the real size of the detector - it can be shown that the most of the energy being focused in the focal spot will be registered by the detector for different wavelengths. The paper presents simple theoretical considerations, numerical modeling and their experimental evaluation.

  10. Slowing and controlling the translocation of DNA in a solid-state nanopore

    PubMed Central

    Stolovitzky, Gustavo; Martyna, Glenn

    2013-01-01

    DNA sequencing methods based on nanopores could potentially represent a low-cost and high-throughput pathway to practical genomics, by replacing current sequencing methods based on synthesis that are limited in speed and cost. The success of nanopore sequencing techniques requires the solution to two fundamental problems: (1) sensing each nucleotide of a DNA strand, in sequence, as it passes through a nanopore; (2) delivering each nucleotide in a DNA strand, in turn, to a sensing site within the nanopore in a controlled manner. It has been demonstrated that a DNA nucleotide can be sensed using electric signals, such as ionic current changes caused by nucleotide blockage at a constriction region in a protein pore or a tunneling current through the nucleotide-bridged gap of two nanoelectrodes built near a solid-state nanopore. However, it is not yet clear how each nucleotide in a DNA strand can be delivered in turn to a sensing site and held there for a sufficient time to ensure high fidelity sensing. This latter problem has been addressed by modifying macroscopic properties, such as a solvent viscosity, ion concentration or temperature. Also, the DNA transistor, a solid state nanopore dressed with a series of metal-dielectric layers has been proposed as a solution. Molecular dynamics simulations provide the means to study and to understand DNA transport in nanopores microscopically. In this article, we review computational studies on how to slow down and control the DNA translocation through a solid-state nanopore PMID:22081018

  11. Elastic properties of protein functionalized nanoporous polymer films

    DOE PAGESBeta

    Charles T. Black; Wang, Haoyu; Akcora, Pinar

    2015-12-16

    Retaining the conformational structure and bioactivity of immobilized proteins is important for biosensor designs and drug delivery systems. Confined environments often lead to changes in conformation and functions of proteins. In this study, lysozyme is chemically tethered into nanopores of polystyrene thin films, and submicron pores in poly(methyl methacrylate) films are functionalized with streptavidin. Nanoindentation experiments show that stiffness of streptavidin increases with decreasing submicron pore sizes. Lysozymes in polystyrene nanopores are found to behave stiffer than the submicron pore sizes and still retain their specific bioactivity relative to the proteins on flat surfaces. Lastly, our results show that proteinmore » functionalized ordered nanoporous polystyrene/poly(methyl methacrylate) films present heterogeneous elasticity and can be used to study interactions between free proteins and designed surfaces.« less

  12. Elastic Properties of Protein Functionalized Nanoporous Polymer Films.

    PubMed

    Wang, Haoyu; Black, Charles T; Akcora, Pinar

    2016-01-12

    Retaining the conformational structure and bioactivity of immobilized proteins is important for biosensor designs and drug delivery systems. Confined environments often lead to changes in conformation and functions of proteins. In this study, lysozyme is chemically tethered into nanopores of polystyrene thin films, and submicron pores in poly(methyl methacrylate) films are functionalized with streptavidin. Nanoindentation experiments show that stiffness of streptavidin increases with decreasing submicron pore sizes. Lysozymes in polystyrene nanopores are found to behave stiffer than the submicron pore sizes and still retain their specific bioactivity relative to the proteins on flat surfaces. Our results show that protein functionalized ordered nanoporous polystyrene/poly(methyl methacrylate) films present heterogeneous elasticity and can be used to study interactions between free proteins and designed surfaces. PMID:26672623

  13. Elastic properties of protein functionalized nanoporous polymer films

    SciTech Connect

    Charles T. Black; Wang, Haoyu; Akcora, Pinar

    2015-12-16

    Retaining the conformational structure and bioactivity of immobilized proteins is important for biosensor designs and drug delivery systems. Confined environments often lead to changes in conformation and functions of proteins. In this study, lysozyme is chemically tethered into nanopores of polystyrene thin films, and submicron pores in poly(methyl methacrylate) films are functionalized with streptavidin. Nanoindentation experiments show that stiffness of streptavidin increases with decreasing submicron pore sizes. Lysozymes in polystyrene nanopores are found to behave stiffer than the submicron pore sizes and still retain their specific bioactivity relative to the proteins on flat surfaces. Lastly, our results show that protein functionalized ordered nanoporous polystyrene/poly(methyl methacrylate) films present heterogeneous elasticity and can be used to study interactions between free proteins and designed surfaces.

  14. Integrated nanopore sensing platform with sub-microsecond temporal resolution

    PubMed Central

    Rosenstein, Jacob K; Wanunu, Meni; Merchant, Christopher A; Drndic, Marija; Shepard, Kenneth L

    2012-01-01

    Nanopore sensors have attracted considerable interest for high-throughput sensing of individual nucleic acids and proteins without the need for chemical labels or complex optics. A prevailing problem in nanopore applications is that the transport kinetics of single biomolecules are often faster than the measurement time resolution. Methods to slow down biomolecular transport can be troublesome and are at odds with the natural goal of high-throughput sensing. Here we introduce a low-noise measurement platform that integrates a complementary metal-oxide semiconductor (CMOS) preamplifier with solid-state nanopores in thin silicon nitride membranes. With this platform we achieved a signal-to-noise ratio exceeding five at a bandwidth of 1 MHz, which to our knowledge is the highest bandwidth nanopore recording to date. We demonstrate transient signals as brief as 1 μs from short DNA molecules as well as current signatures during molecular passage events that shed light on submolecular DNA configurations in small nanopores. PMID:22426489

  15. Technique for Very High Order Nonlinear Simulation and Validation

    NASA Technical Reports Server (NTRS)

    Dyson, Rodger W.

    2001-01-01

    Finding the sources of sound in large nonlinear fields via direct simulation currently requires excessive computational cost. This paper describes a simple technique for efficiently solving the multidimensional nonlinear Euler equations that significantly reduces this cost and demonstrates a useful approach for validating high order nonlinear methods. Up to 15th order accuracy in space and time methods were compared and it is shown that an algorithm with a fixed design accuracy approaches its maximal utility and then its usefulness exponentially decays unless higher accuracy is used. It is concluded that at least a 7th order method is required to efficiently propagate a harmonic wave using the nonlinear Euler equations to a distance of 5 wavelengths while maintaining an overall error tolerance that is low enough to capture both the mean flow and the acoustics.

  16. A Low Order and a High Order Solution for a Converging-Diverging Nozzle Problem

    NASA Technical Reports Server (NTRS)

    Goodrich, John W.

    2000-01-01

    The Computational Aeroacoustics Workshops on Benchmark problems are conducted in order to generate solutions with a variety of methods for problems that are chosen both to be representative of significant and relevant acoustic phenomena. It is generally recognized that CAA applications require the resolution in time and in space of solution details over a significantly broader range of scales than typical computational fluid dynamics applications. These requirements are forcing the development of new methodologies for CAA applications. This paper presents numerical results from a third and a seventh order algorithm for the propagation of an acoustic signal through a converging-diverging nozzle. These two algorithms are members of a new family of high accuracy methods that have the same order accuracy in both space and time, and are an extension of previous work for linearized Euler equations to fully nonlinear time dependent problems. The simulations are all with the fully nonlinear quasi-1D Euler equations for the total solution, which includes both the fluid dynamics and the acoustics. The acoustic solution is obtained from the time dependent nonlinear solution by subtracting the steady solution.

  17. High Order Difference Method for Low Mach Number Aeroacoustics

    NASA Technical Reports Server (NTRS)

    Mueller, B.; Yee, H. C.; Mansour, Nagi (Technical Monitor)

    2001-01-01

    A high order finite difference method with improved accuracy and stability properties for computational aeroacoustics (CAA) at low Mach numbers is proposed. The Euler equations are split into a conservative and a symmetric non- conservative portion to allow the derivation of a generalized energy estimate. Since the symmetrization is based on entropy variables, that splitting of the flux derivatives is referred to as entropy splitting. Its discretization by high order central differences was found to need less numerical dissipation than conventional conservative schemes. Owing to the large disparity of acoustic and stagnation quantities in low Mach number aeroacoustics, the split Euler equations are formulated in perturbation form. The unknowns are the small changes of the conservative variables with respect to their large stagnation values. All nonlinearities and the conservation form of the conservative portion of the split flux derivatives can be retained, while cancellation errors are avoided with its discretization opposed to the conventional conservative form. The finite difference method is third-order accurate at the boundary and the conventional central sixth-order accurate stencil in the interior. The difference operator satisfies the summation by parts property analogous to the integration by parts in the continuous energy estimate. Thus, strict stability of the difference method follows automatically. Spurious high frequency oscillations are suppressed by a characteristic-based filter similar to but without limiter. The time derivative is approximated by a 4-stage low-storage second-order explicit Runge-Kutta method. The method has been applied to simulate vortex sound at low Mach numbers. We consider the Kirchhoff vortex, which is an elliptical patch of constant vorticity rotating with constant angular frequency in irrotational flow. The acoustic pressure generated by the Kirchhoff vortex is governed by the 2D Helmholtz equation, which can be solved

  18. All-order approach to high-precision atomic calculation

    NASA Astrophysics Data System (ADS)

    Iskrenova-Tchoukova, Eugeniya

    High-precision atomic calculations combined with experiments of matching accuracy provide an excellent opportunity to test our understanding of atomic structure and properties as well as the many-body atomic theories. The relativistic all-order method, which is a linearized version of the coupled-cluster singles-doubles method, has proven to yield high precision results for a variety of atomic properties. In this thesis, we study the atomic properties of neutral atoms and ions by means of the relativistic all-order method. The lifetimes and ground state static polarizabilities of a singly ionized barium atom are studied in comparison with the isoelectronic neutral cesium atom and with a singly ionized calcium atom. The lifetimes of a number of excited states in atomic potassium, rubidium, and francium are theoretically calculated and compared with the available experimental data. The magnetic dipole hyperfine constant of the 9S1/2 state in 210Fr is calculated and the result is combined with the experimental one to extract the value of the 210Fr nuclear magnetic moment. Another part of the thesis work focuses on the development and implementation of an extension of the currently used all-order singles-doubles (SD) method to include all valence triple excitations in an iterative way, all-order SD+vT approximation. Some of the ideas and results presented in Chapters 4, 5, and 6 have been published and are subject to copyright laws. These publications are cited accordingly.

  19. A new local high-order laminate theory

    NASA Astrophysics Data System (ADS)

    Wu, Chih-Ping; Hsu, Chih-Shun

    A new local high-order deformable theory of laminated composite/sandwich plates is presented here. The displacement fields of each discrete layer were assumed in the present theory to be of a high-order polynomial series through layer-thickness. The displacement and traction continuity conditions at the interface between layers and the traction conditions at the outer surfaces were imposed as the constraint conditions, and introduced into the potential energy functional by the Lagrange multiplier method. The equations of motion and admissible boundary conditions were given on the basis of the present theory by using the generalized variational principle. Pagano's 3-D elasticity solutions of generally rectangular laminated composite/sandwich plates, fully simply supported, subjected to transverse sinusoidal loading were used for assessment of the present theory and other theories discussed in previous literature. The present theory was found to agree very closely with 3-D elasticity solutions.

  20. Directed liquid phase assembly of highly ordered metallic nanoparticle arrays

    DOE PAGESBeta

    Wu, Yueying; Dong, Nanyi; Fu, Shaofang; Fowlkes, Jason D.; Kondic, Lou; Vincenti, Maria A.; de Ceglia, Domenico; Rack, Philip D.

    2014-04-01

    Directed assembly of nanomaterials is a promising route for the synthesis of advanced materials and devices. We demonstrate the directed-assembly of highly ordered two-dimensional arrays of hierarchical nanostructures with tunable size, spacing and composition. The directed assembly is achieved on lithographically patterned metal films that are subsequently pulse-laser melted; during the brief liquid lifetime, the pattened nanostructures assemble into highly ordered primary and secondary nanoparticles, with sizes below that which was originally patterned. Complementary fluid-dynamics simulations emulate the resultant patterns and show how the competition of capillary forces and liquid metal–solid substrate interaction potential drives the directed assembly. Lastly, asmore » an example of the enhanced functionality, a full-wave electromagnetic analysis has been performed to identify the nature of the supported plasmonic resonances.« less

  1. Directed liquid phase assembly of highly ordered metallic nanoparticle arrays

    SciTech Connect

    Wu, Yueying; Dong, Nanyi; Fu, Shaofang; Fowlkes, Jason D.; Kondic, Lou; Vincenti, Maria A.; de Ceglia, Domenico; Rack, Philip D.

    2014-04-01

    Directed assembly of nanomaterials is a promising route for the synthesis of advanced materials and devices. We demonstrate the directed-assembly of highly ordered two-dimensional arrays of hierarchical nanostructures with tunable size, spacing and composition. The directed assembly is achieved on lithographically patterned metal films that are subsequently pulse-laser melted; during the brief liquid lifetime, the pattened nanostructures assemble into highly ordered primary and secondary nanoparticles, with sizes below that which was originally patterned. Complementary fluid-dynamics simulations emulate the resultant patterns and show how the competition of capillary forces and liquid metal–solid substrate interaction potential drives the directed assembly. Lastly, as an example of the enhanced functionality, a full-wave electromagnetic analysis has been performed to identify the nature of the supported plasmonic resonances.

  2. Spectrally Resolved Maker Fringes in High-Order Harmonic Generation

    NASA Astrophysics Data System (ADS)

    Heyl, C. M.; Güdde, J.; Höfer, U.; L'Huillier, A.

    2011-07-01

    We investigate macroscopic interference effects in high-order harmonic generation using a Ti:sapphire laser operating at a 100 kHz repetition rate. The structure and behavior of spectral and spatial interference fringes are explained and analytically described by transient phase matching of the long electron trajectory contribution. Time-frequency mapping due to the temporal chirp of the harmonic emission allows us to observe Maker fringes directly in the spectral domain.

  3. A highly ordered cubic mesoporous silica/graphene nanocomposite.

    PubMed

    Lee, Chang-Wook; Roh, Kwang Chul; Kim, Kwang-Bum

    2013-10-21

    A highly ordered cubic mesoporous silica (KIT-6)/graphene nanocomposite and 2D KIT-6 nanoflakes were synthesized using a novel synthesis methodology. The non-ionic triblock copolymer, P123, played a dual role as a structure-directing agent in the formation of the cubic mesoporous structure and as a cross-linking agent between mesoporous silica and graphene. The prepared (KIT-6)/graphene nanocomposite could act as a template for the preparation of mesoporous material/graphene nanocomposites. PMID:24057016

  4. High order Nyström method for elastodynamic scattering

    NASA Astrophysics Data System (ADS)

    Chen, Kun; Gurrala, Praveen; Song, Jiming; Roberts, Ron

    2016-02-01

    Elastic waves in solids find important applications in ultrasonic non-destructive evaluation. The scattering of elastic waves has been treated using many approaches like the finite element method, boundary element method and Kirchhoff approximation. In this work, we propose a novel accurate and efficient high order Nyström method to solve the boundary integral equations for elastodynamic scattering problems. This approach employs high order geometry description for the element, and high order interpolation for fields inside each element. Compared with the boundary element method, this approach makes the choice of the nodes for interpolation based on the Gaussian quadrature, which renders matrix elements for far field interaction free from integration, and also greatly simplifies the process for singularity and near singularity treatment. The proposed approach employs a novel efficient near singularity treatment that makes the solver able to handle extreme geometries like very thin penny-shaped crack. Numerical results are presented to validate the approach. By using the frequency domain response and performing the inverse Fourier transform, we also report the time domain response of flaw scattering.

  5. High-order species interactions shape ecosystem diversity.

    PubMed

    Bairey, Eyal; Kelsic, Eric D; Kishony, Roy

    2016-01-01

    Classical theory shows that large communities are destabilized by random interactions among species pairs, creating an upper bound on ecosystem diversity. However, species interactions often occur in high-order combinations, whereby the interaction between two species is modulated by one or more other species. Here, by simulating the dynamics of communities with random interactions, we find that the classical relationship between diversity and stability is inverted for high-order interactions. More specifically, while a community becomes more sensitive to pairwise interactions as its number of species increases, its sensitivity to three-way interactions remains unchanged, and its sensitivity to four-way interactions actually decreases. Therefore, while pairwise interactions lead to sensitivity to the addition of species, four-way interactions lead to sensitivity to species removal, and their combination creates both a lower and an upper bound on the number of species. These findings highlight the importance of high-order species interactions in determining the diversity of natural ecosystems. PMID:27481625

  6. High-order species interactions shape ecosystem diversity

    PubMed Central

    Bairey, Eyal; Kelsic, Eric D.; Kishony, Roy

    2016-01-01

    Classical theory shows that large communities are destabilized by random interactions among species pairs, creating an upper bound on ecosystem diversity. However, species interactions often occur in high-order combinations, whereby the interaction between two species is modulated by one or more other species. Here, by simulating the dynamics of communities with random interactions, we find that the classical relationship between diversity and stability is inverted for high-order interactions. More specifically, while a community becomes more sensitive to pairwise interactions as its number of species increases, its sensitivity to three-way interactions remains unchanged, and its sensitivity to four-way interactions actually decreases. Therefore, while pairwise interactions lead to sensitivity to the addition of species, four-way interactions lead to sensitivity to species removal, and their combination creates both a lower and an upper bound on the number of species. These findings highlight the importance of high-order species interactions in determining the diversity of natural ecosystems. PMID:27481625

  7. Spatial Mode Control of High-Order Harmonics

    SciTech Connect

    Mercer, I.; Mevel, E.; Zerne, R.; LHuillier, A.; Antoine, P.; Wahlstroem, C.

    1996-08-01

    We demonstrate that the spatial mode of high-order harmonics can be continuously controlled. The control is achieved by spatially modulating the degree of elliptical polarization of the fundamental field using birefringent optics. A highly sensitive relationship between the efficiency of harmonic generation and the degree of laser elliptical polarization leads to atoms emitting harmonics only in regions of linear polarization. The harmonics are emitted as annular beams whose angles of divergence can be continuously varied. {copyright} {ital 1996 The American Physical Society.}

  8. Fast calibration of high-order adaptive optics systems

    NASA Astrophysics Data System (ADS)

    Kasper, Markus; Fedrigo, Enrico; Looze, Douglas P.; Bonnet, Henri; Ivanescu, Liviu; Oberti, Sylvain

    2004-06-01

    We present a new method of calibrating adaptive optics systems that greatly reduces the required calibration time or, equivalently, improves the signal-to-noise ratio. The method uses an optimized actuation scheme with Hadamard patterns and does not scale with the number of actuators for a given noise level in the wave-front sensor channels. It is therefore highly desirable for high-order systems and/or adaptive secondary systems on a telescope without a Gregorian focal plane. In the latter case, the measurement noise is increased by the effects of the turbulent atmosphere when one is calibrating on a natural guide star.

  9. Fast calibration of high-order adaptive optics systems.

    PubMed

    Kasper, Markus; Fedrigo, Enrico; Looze, Douglas P; Bonnet, Henri; Ivanescu, Liviu; Oberti, Sylvain

    2004-06-01

    We present a new method of calibrating adaptive optics systems that greatly reduces the required calibration time or, equivalently, improves the signal-to-noise ratio. The method uses an optimized actuation scheme with Hadamard patterns and does not scale with the number of actuators for a given noise level in the wavefront sensor channels. It is therefore highly desirable for high-order systems and/or adaptive secondary systems on a telescope without a Gregorian focal plane. In the latter case, the measurement noise is increased by the effects of the turbulent atmosphere when one is calibrating on a natural guide star. PMID:15191182

  10. Pre-breakdown cavitation nanopores in the dielectric fluid in the inhomogeneous, pulsed electric fields

    NASA Astrophysics Data System (ADS)

    Pekker, Mikhail; Shneider, Mikhail N.

    2015-10-01

    This paper discusses the nanopores emerging and developing in a liquid dielectric under the action of the ponderomotive electrostrictive forces in a nonuniform electric field. It is shown that the gradient of the electric field in the vicinity of the rupture (cavitation nanopore) substantially increases and determines whether the rupture grows or collapses. The cavitation rupture in the liquid (nanopore) tends to stretch along the lines of the original field. The mechanism of the breakdown associated with the generation of secondary ruptures in the vicinity of the poles of the nanopore is proposed. The estimations of the extension time for nanopore in water and oil (polar and nonpolar liquids, respectively) are presented. A new mechanism of nano- and subnanosecond breakdown in the insulating (transformer) oil that can be realized in the vicinity of water microdroplets in nanosecond high-voltage devices is considered.

  11. Label-Free Optical Detection of Biomolecular Translocation through Nanopore Arrays

    PubMed Central

    2015-01-01

    In recent years, nanopores have emerged as exceptionally promising single-molecule sensors due to their ability to detect biomolecules at subfemtomole levels in a label-free manner. Development of a high-throughput nanopore-based biosensor requires multiplexing of nanopore measurements. Electrical detection, however, poses a challenge, as each nanopore circuit must be electrically independent, which requires complex nanofluidics and embedded electrodes. Here, we present an optical method for simultaneous measurements of the ionic current across an array of solid-state nanopores, requiring no additional fabrication steps. Proof-of-principle experiments are conducted that show simultaneous optical detection and characterization of ssDNA and dsDNA using an array of pores. Through a comparison with electrical measurements, we show that optical measurements are capable of accessing equivalent transmembrane current information. PMID:25232895

  12. Bare conical nanopore embedded in polymer membrane for Cr(III) sensing.

    PubMed

    Zhai, Qingfeng; Wang, Jiahai; Jiang, Hong; Wei, Qin; Wang, Erkang

    2015-08-01

    In this article, we propose a nanopore-based approach to detect metal ions without any external functionalization. In detection of the biologically and environmentally relevant Cr(3+) ion as a prototypical example to prove our strategy, both selectivity and sensitivity were individually achieved. In contrast to mainstream research based on receptor-functionalized nanopores, we report a method for easy regeneration of the nanopore surface that allows elimination of the tedious functionalization steps. Besides, with the assistance of a strong chelator (EDTA), the asymmetric nanopore becomes highly resistant to the interference of the metal-ions matrix, and shows significant specificity towards Cr(3+). The detection limit of this sensor was 16 nM (signal-to-noise ratio=3), which was comparable to reported values. By virtue of the reusability of the polymer surface, metal ion sensors based on asymmetric nanopores can be applied universally in combination with chelators sensitive to specific metal ions. PMID:26048845

  13. Applications of Nanoporous Materials in Agriculture

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nanoporous materials possess organized pore distributions and increased surface areas. Advances in the systematic design of nanoporous materials enable incorporation of functionality for better sensitivity in detection methods, increased capacity of sorbents, and improved selectivity and yield in ca...

  14. Nanoporous gold film: fabrication and role as a catalytic reactor.

    PubMed

    Xia, Youyi; Deng, Xiang; Yan, Shuxin; Gao, Chang; Ma, Cong; Jin, Ling

    2015-07-14

    Nanoporous gold (NPG) is attractive due to its high catalytic activity. From an applied and economical point of view, fabricating thin NPG films is recognized to be an ideal approach. Herein, we report an interesting finding that a thin NPG film with a thickness of 90 nm can be prepared on various substrates conveniently by using seed-mediated growth. The film has a nanoporous character with 30-60 nm and 10-30 nm of ligament and pore size, respectively. The high cost-efficiency, adjustable substrates, easy and convenient operation make this film reactor a good candidate for catalyzing both oxidative and hydrogenation reactions. PMID:26067387

  15. Characterization of hydrophobic nanoporous particle liquids for energy absorption

    NASA Astrophysics Data System (ADS)

    Hsu, Yi; Liu, Yingtao

    2016-04-01

    Recently, the development of hydrophobic nanoporous technologies has drawn increased attention, especially for the applications of energy absorption and impact protection. Although significant amount of research has been conducted to synthesis and characterize materials to protect structures from impact damage, the tradition methods focused on converting kinetic energy to other forms, such as heat and cell buckling. Due to their high energy absorption efficiency, hydrophobic nanoporous particle liquids (NPLs) are one of the most attractive impact mitigation materials. During impact, such particles directly trap liquid molecules inside the non-wetting surface of nanopores in the particles. The captured impact energy is simply stored temporarily and isolated from the original energy transmission path. In this paper we will investigate the energy absorption efficiency of combinations of silica nanoporous particles and with multiple liquids. Inorganic particles, such as nanoporous silica, are characterized using scanning electron microscopy. Small molecule promoters, such as methanol and ethanol, are introduced to the prepared NPLs. Their effects on the energy absorption efficiency are studied in this paper. NPLs are prepared by dispersing the studied materials in deionized water. Energy absorption efficiency of these liquids are experimentally characterized using an Instron mechanical testing frame and in-house develop stainless steel hydraulic cylinder system.

  16. Development of macroscopic nanoporous graphene membranes for gas separation

    NASA Astrophysics Data System (ADS)

    Boutilier, Michael; Hadjiconstantinou, Nicolas; Karnik, Rohit

    2015-11-01

    Nanoporous graphene membranes have the potential to exceed permeance and selectivity limits of existing gas separation membranes due to their atomic thickness and ability to support sub-nanometer pores for molecular sieving, while offering low resistance to flow. Gas separation by graphene nanopores has been demonstrated experimentally on micron-scale membranes, but scaling-up to larger sizes is challenging due to graphene imperfections and control of the selective nanopore size distribution. Using a model we developed for the inherent permeance of graphene, we designed a macroscopic graphene membrane predicted to be selectively permeable despite material imperfections. Micrometer-scale defects are sealed by interfacial polymerization and nanometer-scale defects are sealed by atomic layer deposition. The underlying support structure is tuned to further reduce the effects of leakage. Finally, ion bombardment followed by oxidative etching is used to create a high density of selective nanopores. SEM and TEM imaging are used to characterize the resulting membrane structure, and its performance is assessed by gas permeance and selectivity measurements. This work provides insight into gas flow through nanoporous graphene membranes and guides their future development.

  17. DNA Translocation through Hydrophilic Nanopore in Hexagonal Boron Nitride

    NASA Astrophysics Data System (ADS)

    Zhou, Zhi; Hu, Ying; Wang, Hao; Xu, Zhi; Wang, Wenlong; Bai, Xuedong; Shan, Xinyan; Lu, Xinghua

    2013-11-01

    Ultra-thin solid-state nanopore with good wetting property is strongly desired to achieve high spatial resolution for DNA sequencing applications. Atomic thick hexagonal boron nitride (h-BN) layer provides a promising two-dimensional material for fabricating solid-state nanopores. Due to its good oxidation resistance, the hydrophilicity of h-BN nanopore device can be significantly improved by UV-Ozone treatment. The contact angle of a KCl-TE droplet on h-BN layer can be reduced from 57° to 26° after the treatment. Abundant DNA translocation events have been observed in such devices, and strong DNA-nanopore interaction has been revealed in pores smaller than 10 nm in diameter. The 1/f noise level is closely related to the area of suspended h-BN layer, and it is significantly reduced in smaller supporting window. The demonstrated performance in h-BN nanopore paves the way towards base discrimination in a single DNA molecule.

  18. DNA characterization with Ion Beam Sculpted Silicon Nitride Nanopores

    PubMed Central

    Rollings, Ryan C.; McNabb, David S.; Li, Jiali

    2013-01-01

    Solid state nanopores are emerging as robust single molecule electronic measurement devices and as platforms for confining biomolecules for further analysis. The first silicon nitride nanopore to detect individual DNA molecules were fabricated using ion beam sculpting (IBS), a method that uses broad, low energy ion beams to create nanopores with dimensions ranging from 2 to 20 nm. In this chapter, we discuss the fabrication, characterization, and use of IBS sculpted nanopores as well as efficient uses of pClamp and MATLAB software suites for data acquisition and analysis. The fabrication section will cover the repeatability and the pore size limits. The characterization discussion focuses on the geometric properties as measured by low and high resolution transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), and energy filtered TEM (EFTEM). The section on translocation experiments focuses on how to use tools commonly available to the nanopore experimenter to determine whether a pore will be useful for experimentation or if it should be abandoned. A memory efficient method of taking data using Clampex’s event-driven mode and dual channel recording will be presented, followed by an easy to implement multi-threshold event detection and classification method using MATLAB software. PMID:22528259

  19. Sensing applications based on plasmonic nanopores: The hole story.

    PubMed

    Dahlin, Andreas B

    2015-07-21

    A review of sensing applications based on plasmonic nanopores is given. Many new types of plasmonic nanopores have recently been fabricated, including pores penetrating multilayers of thin films, using a great variety of fabrication techniques based on either serial nanolithography or self-assembly. One unique advantage with nanopores compared to other plasmonic sensors is that sample liquids can flow through the surface, which increases the rate of binding and improves the detection limit under certain conditions. Also, by utilizing the continuous metal films, electrical control can be implemented for electrochemistry, dielectrophoresis and resistive heating. Much effort is still spent on trying to improve sensor performance in various ways, but the literature uses inconsistent benchmark parameters. Recently plasmonic nanopores have been used to analyse targets of high clinical or academic interest. Although this is an important step forward, one should probably reflect upon whether the same results could have been achieved with another optical technique. Overall, this critical review suggests that the research field would benefit by focusing on applications where plasmonic nanopores truly can offer unique advantages over similar techniques. PMID:25675146

  20. Probing non local order parameters in highly correlated Bose insulators

    NASA Astrophysics Data System (ADS)

    Altman, Ehud

    2008-03-01

    Ground states of integer spin chains are known since the late 80's to sustain highly non local order described by infinite string operators of the spins. Such states defy the usual Landau theory description and can be considered simple prototypes of topological order. Recently we showed that spinless Bose insulators with nearest neighbor or longer range repulsion in one dimension can exhibit similar string order in terms of the boson density [1]. The tunability of cold atomic systems would allow much more flexibility in probing the non local order than spin systems do. For example the bosons can be tuned across a quantum phase transition between the exotic insulator, which we term Haldane insulator, and the usual Mott insulator. Investigating how the transition responds to external perturbations lends direct access to properties of the string order parameter. I will demonstrate this with several new results obtained from a field theoretic description of the phases and confirmed by numerical calculations using DMRG. Particularly revealing of the unusual character of the string order is the prediction that any external perturbation, which breaks the lattice inversion symmetry, would eliminate the distinction between the Haldane and Mott phases and allow a fully gapped adiabatic connection between them. This is remarkable given that neither phase involves spontaneous breaking of lattice inversion symmetry. We also predict that inter-chain tunneling destroys the direct phase transition between the two insulators by establishing an intermediate superfluid phase. Finally I will discuss how the new phases and phase transitions may be realized and probed in actual experiments with ultra cold atoms or polar molecules. [1] E. G. Dalla Torre, E. Berg and E. Altman, Phys. Rev. Lett. 97, 260401 (2006)

  1. TWave: high-order analysis of functional MRI.

    PubMed

    Barnathan, Michael; Megalooikonomou, Vasileios; Faloutsos, Christos; Faro, Scott; Mohamed, Feroze B

    2011-09-15

    The traditional approach to functional image analysis models images as matrices of raw voxel intensity values. Although such a representation is widely utilized and heavily entrenched both within neuroimaging and in the wider data mining community, the strong interactions among space, time, and categorical modes such as subject and experimental task inherent in functional imaging yield a dataset with "high-order" structure, which matrix models are incapable of exploiting. Reasoning across all of these modes of data concurrently requires a high-order model capable of representing relationships between all modes of the data in tandem. We thus propose to model functional MRI data using tensors, which are high-order generalizations of matrices equivalent to multidimensional arrays or data cubes. However, several unique challenges exist in the high-order analysis of functional medical data: naïve tensor models are incapable of exploiting spatiotemporal locality patterns, standard tensor analysis techniques exhibit poor efficiency, and mixtures of numeric and categorical modes of data are very often present in neuroimaging experiments. Formulating the problem of image clustering as a form of Latent Semantic Analysis and using the WaveCluster algorithm as a baseline, we propose a comprehensive hybrid tensor and wavelet framework for clustering, concept discovery, and compression of functional medical images which successfully addresses these challenges. Our approach reduced runtime and dataset size on a 9.3GB finger opposition motor task fMRI dataset by up to 98% while exhibiting improved spatiotemporal coherence relative to standard tensor, wavelet, and voxel-based approaches. Our clustering technique was capable of automatically differentiating between the frontal areas of the brain responsible for task-related habituation and the motor regions responsible for executing the motor task, in contrast to a widely used fMRI analysis program, SPM, which only detected the

  2. Water desalination across nanoporous graphene.

    PubMed

    Cohen-Tanugi, David; Grossman, Jeffrey C

    2012-07-11

    We show that nanometer-scale pores in single-layer freestanding graphene can effectively filter NaCl salt from water. Using classical molecular dynamics, we report the desalination performance of such membranes as a function of pore size, chemical functionalization, and applied pressure. Our results indicate that the membrane's ability to prevent the salt passage depends critically on pore diameter with adequately sized pores allowing for water flow while blocking ions. Further, an investigation into the role of chemical functional groups bonded to the edges of graphene pores suggests that commonly occurring hydroxyl groups can roughly double the water flux thanks to their hydrophilic character. The increase in water flux comes at the expense of less consistent salt rejection performance, which we attribute to the ability of hydroxyl functional groups to substitute for water molecules in the hydration shell of the ions. Overall, our results indicate that the water permeability of this material is several orders of magnitude higher than conventional reverse osmosis membranes, and that nanoporous graphene may have a valuable role to play for water purification. PMID:22668008

  3. Integrated high-order surface diffraction gratings for diode lasers

    NASA Astrophysics Data System (ADS)

    Zolotarev, V. V.; Leshko, A. Yu; Pikhtin, N. A.; Slipchenko, S. O.; Sokolova, Z. N.; Lubyanskiy, Ya V.; Voronkova, N. V.; Tarasov, I. S.

    2015-12-01

    High-order surface diffraction gratings acting as a distributed Bragg reflector (DBR) in mesa stripe semiconductor lasers (λ = 1030 nm) have been studied theoretically and experimentally. Higher order interfering radiation modes (IRMs), which propagate off the plane of the waveguide, have been shown to have a crucial effect on the reflection and transmission spectra of the DBR. The decrease in the reflectivity of the DBR in response to the increase in the diffraction efficiency of these modes may reach 80% and more. According to theoretical analysis results, the intensity of the higher order IRMs is determined by the geometry of the DBR groove profile. Experimental data demonstrate that the noncavity modes are responsible for parasitic light leakage losses in the laser cavity. It has been shown that, in the case of nonoptimal geometry of the grating groove profile, the overall external differential quantum efficiency of the parasitic laser emission may exceed 45%, which is more than half of the laser output power. The optimal geometry of the DBR groove profile is trapezoidal, with the smallest possible lower base. Experimental evidence has been presented that this geometry considerably reduces the power of the higher order IRMs and minimises the parasitic light leakage loss.

  4. High-order primordial perturbations with quantum gravitational effects

    NASA Astrophysics Data System (ADS)

    Zhu, Tao; Wang, Anzhong; Kirsten, Klaus; Cleaver, Gerald; Sheng, Qin

    2016-06-01

    In this paper, we provide a systematic investigation of high-order primordial perturbations with nonlinear dispersion relations due to quantum gravitational effects in the framework of uniform asymptotic approximations. Because of these effects, the equation of motion of the mode function in general has multiple turning points. After obtaining analytically approximated solutions to any order in different regions, associated with different types of turning points, we match them to the third one. To this order the errors are less than 0.15%. General expressions of the power spectra of the primordial tensor and scalar perturbations are derived explicitly. We also investigate effects of backreactions of the quantum gravitational corrections, and make sure that inflation lasts long enough in order to solve the underlying problems, such as flatness, horizon, and monopole. Then we study various features of the spectra that are observationally relevant. In particular, under a moderate assumption about the energy scale of the underlying theory of quantum gravity, we have shown that the quantum gravitational effects may alter significantly the ratio between the tensor and scalar power spectra, thereby providing a natural mechanism to alleviate the tension between observations and certain inflationary models, including the one with a quadratic potential.

  5. A Multilevel Parallelization Framework for High-Order Stencil Computations

    NASA Astrophysics Data System (ADS)

    Dursun, Hikmet; Nomura, Ken-Ichi; Peng, Liu; Seymour, Richard; Wang, Weiqiang; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya

    Stencil based computation on structured grids is a common kernel to broad scientific applications. The order of stencils increases with the required precision, and it is a challenge to optimize such high-order stencils on multicore architectures. Here, we propose a multilevel parallelization framework that combines: (1) inter-node parallelism by spatial decomposition; (2) intra-chip parallelism through multithreading; and (3) data-level parallelism via single-instruction multiple-data (SIMD) techniques. The framework is applied to a 6 th order stencil based seismic wave propagation code on a suite of multicore architectures. Strong-scaling scalability tests exhibit superlinear speedup due to increasing cache capacity on Intel Harpertown and AMD Barcelona based clusters, whereas weak-scaling parallel efficiency is 0.92 on 65,536 BlueGene/P processors. Multithreading+SIMD optimizations achieve 7.85-fold speedup on a dual quad-core Intel Clovertown, and the data-level parallel efficiency is found to depend on the stencil order.

  6. High-order harmonics from laser-irradiated plasma surfaces

    SciTech Connect

    Teubner, U.; Gibbon, P.

    2009-04-15

    The investigation of high-order harmonic generation (HHG) of femtosecond laser pulses by means of laser-produced plasmas is surveyed. This kind of harmonic generation is an alternative to the HHG in gases and shows significantly higher conversion efficiency. Furthermore, with plasma targets there is no limitation on applicable laser intensity and thus the generated harmonics can be much more intense. In principle, harmonic light may also be generated at relativistic laser intensity, in which case their harmonic intensities may even exceed that of the focused laser pulse by many orders of magnitude. This phenomenon presents new opportunities for applications such as nonlinear optics in the extreme ultraviolet region, photoelectron spectroscopy, and opacity measurements of high-density matter with high temporal and spatial resolution. On the other hand, HHG is strongly influenced by the laser-plasma interaction itself. In particular, recent results show a strong correlation with high-energy electrons generated during the interaction process. The harmonics are a promising tool for obtaining information not only on plasma parameters such as the local electron density, but also on the presence of large electric and magnetic fields, plasma waves, and the (electron) transport inside the target. This paper reviews the theoretical and experimental progress on HHG via laser-plasma interactions and discusses the prospects for applying HHG as a short-wavelength, coherent optical tool.

  7. Shaping Neural Circuits by High Order Synaptic Interactions.

    PubMed

    Ravid Tannenbaum, Neta; Burak, Yoram

    2016-08-01

    Spike timing dependent plasticity (STDP) is believed to play an important role in shaping the structure of neural circuits. Here we show that STDP generates effective interactions between synapses of different neurons, which were neglected in previous theoretical treatments, and can be described as a sum over contributions from structural motifs. These interactions can have a pivotal influence on the connectivity patterns that emerge under the influence of STDP. In particular, we consider two highly ordered forms of structure: wide synfire chains, in which groups of neurons project to each other sequentially, and self connected assemblies. We show that high order synaptic interactions can enable the formation of both structures, depending on the form of the STDP function and the time course of synaptic currents. Furthermore, within a certain regime of biophysical parameters, emergence of the ordered connectivity occurs robustly and autonomously in a stochastic network of spiking neurons, without a need to expose the neural network to structured inputs during learning. PMID:27517461

  8. Shaping Neural Circuits by High Order Synaptic Interactions

    PubMed Central

    Ravid Tannenbaum, Neta; Burak, Yoram

    2016-01-01

    Spike timing dependent plasticity (STDP) is believed to play an important role in shaping the structure of neural circuits. Here we show that STDP generates effective interactions between synapses of different neurons, which were neglected in previous theoretical treatments, and can be described as a sum over contributions from structural motifs. These interactions can have a pivotal influence on the connectivity patterns that emerge under the influence of STDP. In particular, we consider two highly ordered forms of structure: wide synfire chains, in which groups of neurons project to each other sequentially, and self connected assemblies. We show that high order synaptic interactions can enable the formation of both structures, depending on the form of the STDP function and the time course of synaptic currents. Furthermore, within a certain regime of biophysical parameters, emergence of the ordered connectivity occurs robustly and autonomously in a stochastic network of spiking neurons, without a need to expose the neural network to structured inputs during learning. PMID:27517461

  9. Rad-Hydro with a High-Order, Low-Order Method

    SciTech Connect

    Wollaber, Allan Benton; Park, HyeongKae; Lowrie, Robert Byron; Rauenzahn, Rick M.; Cleveland, Mathew Allen

    2015-08-04

    Moment-based acceleration via the development of “high-order, low-order” (HO-LO) algorithms has provided substantial accuracy and efficiency enhancements for solutions of the nonlinear, thermal radiative transfer equations by CCS-2 and T-3 staff members. Accuracy enhancements over traditional, linearized methods are obtained by solving a nonlinear, timeimplicit HO-LO system via a Jacobian-free Newton Krylov procedure. This also prevents the appearance of non-physical maximum principle violations (“temperature spikes”) associated with linearization. Efficiency enhancements are obtained in part by removing “effective scattering” from the linearized system. In this highlight, we summarize recent work in which we formally extended the HO-LO radiation algorithm to include operator-split radiation-hydrodynamics.

  10. High Precision Superconducting Cavity Diagnostics With Higher Order Mode Measurements

    SciTech Connect

    Molloy, S.; Frisch, J.; McCormick, D.; May, J.; Ross, M.; Smith, T.; Baboi, N.; Hensler, O.; Petrosian, L.; Napoly, O.; Paparella, R.C.; Simon, C.; Eddy, N.; Nagaitsev, S.; Wendt, M.; /Fermilab

    2007-02-12

    Experiments at the FLASH facility at DESY have demonstrated that the higher order modes induced in superconducting cavities can be used to provide a variety of beam and cavity diagnostics. The axes of the modes can be determined from the beam orbit that produces minimum power in the dipole HOM modes. The phase and amplitude of the dipole modes can be used to obtain high resolution beam position information, and the phase of the monopole modes to measure the beam phase relative to the accelerator rf. For most superconducting accelerators, the existing higher order mode couplers provide the necessary signals, and the downmix and digitizing electronics are straightforward, similar to those for a conventional beam position monitor.

  11. High order parallel numerical schemes for solving incompressible flows

    NASA Technical Reports Server (NTRS)

    Lin, Avi; Milner, Edward J.; Liou, May-Fun; Belch, Richard A.

    1992-01-01

    The use of parallel computers for numerically solving flow fields has gained much importance in recent years. This paper introduces a new high order numerical scheme for computational fluid dynamics (CFD) specifically designed for parallel computational environments. A distributed MIMD system gives the flexibility of treating different elements of the governing equations with totally different numerical schemes in different regions of the flow field. The parallel decomposition of the governing operator to be solved is the primary parallel split. The primary parallel split was studied using a hypercube like architecture having clusters of shared memory processors at each node. The approach is demonstrated using examples of simple steady state incompressible flows. Future studies should investigate the secondary split because, depending on the numerical scheme that each of the processors applies and the nature of the flow in the specific subdomain, it may be possible for a processor to seek better, or higher order, schemes for its particular subcase.

  12. Highly sensitive electrochemiluminescence detection of p53 protein using functionalized Ru-silica nanoporous@gold nanocomposite.

    PubMed

    Afsharan, Hadi; Navaeipour, Farzaneh; Khalilzadeh, Balal; Tajalli, Habib; Mollabashi, Mahmood; Ahar, Mohammad Johari; Rashidi, Mohammad-Reza

    2016-06-15

    A simple, rapid response time and ultrahigh sensitive electrochemiluminescence (ECL) immunosensor based on Ru(bpy)3(2+)doped silica doped AuNPs (Ru-Si@Au nanocomposite) was developed for detection of p53 protein, a well-known tumor suppressor. The immunosensor was constructed using biotinylated capture antibody, immobilized on the glassy carbon electrode (GCE) using streptavidin modified-gold nanoparticles/thiolated graphene oxide, followed by its conjugation with the Ru-silica@Au nanocomposite labeled secondary antibody to form a sandwich-type immunocomplex. The use of Ru-Si@Au nanocomposites led to a remarkable increase in the ECL intensity and, thus, the sensitivity of the method. Under the optimized conditions, the linear range of the proposed p53 immunosensor was found between 0.2 and 200 pM with a calculated limit of detection of 22.8 fM. The selectivity and reproducibility of the immunosensor was also investigated and the results showed high specificity and great stability in detecting of p53. Moreover, the ECL immunosensor was successfully applied for quantification of p53 protein in the human spiked serum samples and more importantly in the human normal and cancer skin fibroblast cells showing much satisfactory result compared with the ELISA method. The proposed immunosensor reported herein offers a considerable potential in early detection of cancer and clinical diagnosis and provides a new platform for biomarker detection. PMID:26827144

  13. Nanoporous two-dimensional MoS2 membranes for fast saline solution purification.

    PubMed

    Kou, Jianlong; Yao, Jun; Wu, Lili; Zhou, Xiaoyan; Lu, Hangjun; Wu, Fengmin; Fan, Jintu

    2016-08-10

    Finding a membrane with both high permeability and high salt rejection is very important for saline solution purification. Here, we report the performance of molybdenum disulfide (MoS2) membranes with nanoscale pores for saline solution purification via all-atom molecular dynamics simulations. It was found that the nanoporous two-dimensional MoS2 membrane can impede salt ions, while allowing highly efficient permeation of water molecules. By engineering the appropriate sizes of the nanopores within two-dimensional MoS2 membranes, their water permeability can be tens of times as high as that of conventional reverse osmosis membranes, while still maintaining a high salt rejection rate. These remarkable water permeability and salt rejection properties of the nanoporous monolayer MoS2 membranes are attributed to the formation of single chain hydrogen bonds, which link the water molecules within the nanopores and those at the immediate exteriors of the nanopores, causing significant reduction in the resistance of water molecules passing through the nanopores, which are small enough for any salt ions to pass through. Therefore such nanoporous monolayer MoS2 membranes have great potential for saline solution purification. PMID:27453207

  14. Two Color DNA Barcode Detection in Photoluminescence Suppressed Silicon Nitride Nanopores

    PubMed Central

    2015-01-01

    Optical sensing of solid-state nanopores is a relatively new approach that can enable high-throughput, multicolor readout from a collection of nanopores. It is therefore highly attractive for applications such as nanopore-based DNA sequencing and genotyping using DNA barcodes. However, to date optical readout has been plagued by the need to achieve sufficiently high signal-to-noise ratio (SNR) for single fluorophore sensing, while still maintaining millisecond resolution. One of the main factors degrading the optical SNR in solid-state nanopores is the high photoluminescence (PL) background emanating from the silicon nitride (SiNx) membrane in which pores are commonly fabricated. Focusing on the optical properties of SiNx nanopores we show that the local membrane PL intensity is substantially reduced, and its spectrum is shifted toward shorter wavelengths with increasing e-beam dose. This phenomenon, which is correlated with a marked photocurrent enhancement in these nanopores, is utilized to perform for the first time single molecule fluorescence detection using both green and red laser excitations. Specifically, the reduction in PL and the concurrent measurement of the nanopore photocurrent enhancement allow us to maximize the background suppression and to detect a dual color, five-unit DNA barcode with high SNR levels. PMID:25522780

  15. Two color DNA barcode detection in photoluminescence suppressed silicon nitride nanopores.

    PubMed

    Assad, Ossama N; Di Fiori, Nicolas; Squires, Allison H; Meller, Amit

    2015-01-14

    Optical sensing of solid-state nanopores is a relatively new approach that can enable high-throughput, multicolor readout from a collection of nanopores. It is therefore highly attractive for applications such as nanopore-based DNA sequencing and genotyping using DNA barcodes. However, to date optical readout has been plagued by the need to achieve sufficiently high signal-to-noise ratio (SNR) for single fluorophore sensing, while still maintaining millisecond resolution. One of the main factors degrading the optical SNR in solid-state nanopores is the high photoluminescence (PL) background emanating from the silicon nitride (SiNx) membrane in which pores are commonly fabricated. Focusing on the optical properties of SiNx nanopores we show that the local membrane PL intensity is substantially reduced, and its spectrum is shifted toward shorter wavelengths with increasing e-beam dose. This phenomenon, which is correlated with a marked photocurrent enhancement in these nanopores, is utilized to perform for the first time single molecule fluorescence detection using both green and red laser excitations. Specifically, the reduction in PL and the concurrent measurement of the nanopore photocurrent enhancement allow us to maximize the background suppression and to detect a dual color, five-unit DNA barcode with high SNR levels. PMID:25522780

  16. Hybrid overlay metrology for high order correction by using CDSEM

    NASA Astrophysics Data System (ADS)

    Leray, Philippe; Halder, Sandip; Lorusso, Gian; Baudemprez, Bart; Inoue, Osamu; Okagawa, Yutaka

    2016-03-01

    Overlay control has become one of the most critical issues for semiconductor manufacturing. Advanced lithographic scanners use high-order corrections or correction per exposure to reduce the residual overlay. It is not enough in traditional feedback of overlay measurement by using ADI wafer because overlay error depends on other process (etching process and film stress, etc.). It needs high accuracy overlay measurement by using AEI wafer. WIS (Wafer Induced Shift) is the main issue for optical overlay, IBO (Image Based Overlay) and DBO (Diffraction Based Overlay). We design dedicated SEM overlay targets for dual damascene process of N10 by i-ArF multi-patterning. The pattern is same as device-pattern locally. Optical overlay tools select segmented pattern to reduce the WIS. However segmentation has limit, especially the via-pattern, for keeping the sensitivity and accuracy. We evaluate difference between the viapattern and relaxed pitch gratings which are similar to optical overlay target at AEI. CDSEM can estimate asymmetry property of target from image of pattern edge. CDSEM can estimate asymmetry property of target from image of pattern edge. We will compare full map of SEM overlay to full map of optical overlay for high order correction ( correctables and residual fingerprints).

  17. Nanoporous Gold as a Platform for a Building Block Catalyst

    SciTech Connect

    Wittstock, Arne; Wichmann, Andre; Baeumer, Marcus

    2012-09-25

    The porous bulk materials are of great interest in catalysis because they can be employed in heterogeneous gas and liquid phase catalysis, electrocatalysis, and in electrocatalytic sensing. Nanoporous gold gained considerable attraction in this context because it is the prime example of a corrosion-derived nanoporous bulk metal. Moreover, the material was shown to be a very active and selective Au type catalyst for a variety of oxidation reactions. In leveraging the functionalization of the surface of the material with various additives, its catalytic applications can be extended and tuned. In this review, we will summarize recent developments in using nanoporous gold as the platform for the development of high performance catalytic materials by adding metals, metal oxides, and molecular functionalities as building blocks.

  18. Nanoporous Carbon Monoliths with Tunable Thermal Insulation and Mechanical Properties.

    PubMed

    Wang, Xiaopeng; Chen, Fenghua; Luo, Zhenhua; Li, Hao; Zhao, Tong

    2016-01-01

    In this work, nanoscale porous carbon monoliths, with excellent compressive strength and thermal insulation, were obtained with a simple method of carbonizing cured phenol-formaldehyde resin/poly(methyl methacrylate) blends. Apparent density, pore size and morphology of the carbon monoliths were tailored by changing the composition, curing process and carbonization temperature. The continuous nanopores played a key role in enhancing mechanical and thermal performance of the carbon materials. When PMMA concentration was 25%, apparent density and thermal conductivity of the nanoporous carbonaceous monoliths were obtained as low as 1.07 g · cm⁻³ and 0.42 W/(m · K), decreasing by 29.4% and 35.4% than that of carbonaceous monoliths obtained from pure PF; while compressive strength of the nanoporous carbonaceous monoliths was as high as 34 MPa, which was improved over five times than that of pure PF carbon monoliths. PMID:27398592

  19. Fabrication of solid-state nanopores and its perspectives.

    PubMed

    Kudr, Jiri; Skalickova, Sylvie; Nejdl, Lukas; Moulick, Amitava; Ruttkay-Nedecky, Branislav; Adam, Vojtech; Kizek, Rene

    2015-10-01

    Nanofluidics is becoming an extensively developing technique in the field of bioanalytical chemistry. Nanoscale hole embed in an insulating membrane is employed in a vast variety of sensing platforms and applications. Although, biological nanopores have several attractive characteristics, in this paper, we focused on the solid-state nanopores due to their advantages as high stability, possibility of diameter control, and ease of surface functionalizing. A detection method, based on the translocation of analyzed molecules through nanochannels under applied voltage bias and resistive pulse sensing, is well established. Nevertheless, it seems that the new detection methods like measuring of transverse electron tunneling using nanogap electrodes or optical detection can offer significant additional advantages. The aim of this review is not to cite all related articles, but highlight the steps, which in our opinion, meant important progresses in solid-state nanopore analysis. PMID:26046318

  20. Deformation mechanisms in gold nanowires and nanoporous gold

    NASA Astrophysics Data System (ADS)

    Dou, R.; Derby, B.

    2011-03-01

    We present a study of the deformation of gold nanowires of diameter 30-70 nm and nanoporous gold specimens with ligament diameter 5-10 nm, both produced by electrodeposition into anodised aluminium oxide templates. The nanowires show extensive surface slip steps and low dislocation densities with a few perfect dislocation loops, Shockley partial dislocations and microtwins observed after deformation. Nanoporous specimens show deformation localised to the nodes between the ligaments of the foamed structure, with high densities of microtwins and Shockley partial dislocations in these regions. Similar dislocation structures are seen in larger nanowires deformed in bending. This is shown to be consistent with a strain gradient plasticity model for the deformation of nanoporous gold, with the strain gradient accommodated by geometrically necessary twins and partial dislocations.

  1. High order harmonic generation in dual gas multi-jets

    SciTech Connect

    Tosa, Valer E-mail: calin.hojbota@itim-cj.ro; Hojbota, Calin E-mail: calin.hojbota@itim-cj.ro

    2013-11-13

    High order harmonic generation (HHG) in gas media suffers from a low conversion efficiency that has its origins in the interaction of the atom/molecule with the laser field. Phase matching is the main way to enhance the harmonic flux and several solutions have been designed to achieve it. Here we present numerical results modeling HHG in a system of multi-jets in which two gases alternate: the first gas jet (for example Ne) generates harmonics and the second one which ionizes easier, recover the phase matching condition. We obtain configurations which are experimentally feasible with respect to pressures and dimensions of the jets.

  2. High Precision SC Cavity alignment Measurements with Higher Order Modes

    SciTech Connect

    Molloy, Stephen; Frisch, Josef; Hendrickson, Linda; McCormick, Douglas; May, Justin; Ross, Marc; Smith, Tonee; Eddy, Nathan; Nagaitsev, Sergei; Baboi, Nicoleta; Hensler, Olaf; Petrosyan, Lyudvig; Napoly, Olivier; Paparella, Rita; Simon, Claire; /DSM, DAPNIA, Saclay

    2007-06-14

    Experiments at the FLASH linac at DESY have demonstrated that the higher order modes (HOMs) induced in superconducting cavities can be used to provide a variety of beam and cavity diagnostics. The centers of the cavities can be determined from the beam orbit which produces minimum power in the dipole HOM modes. The phase and amplitude of the dipole modes can be used as a high resolution beam position monitor. For most superconducting accelerators, the existing HOM couplers provide the necessary signals, and the downmix and digitizing electronics are straightforward, similar to those for a conventional BPM.

  3. High-order harmonic generation in a capillary discharge

    DOEpatents

    Rocca, Jorge J.; Kapteyn, Henry C.; Mumane, Margaret M.; Gaudiosi, David; Grisham, Michael E.; Popmintchev, Tenio V.; Reagan, Brendan A.

    2010-06-01

    A pre-ionized medium created by a capillary discharge results in more efficient use of laser energy in high-order harmonic generation (HHG) from ions. It extends the cutoff photon energy, and reduces the distortion of the laser pulse as it propagates down the waveguide. The observed enhancements result from a combination of reduced ionization energy loss and reduced ionization-induced defocusing of the driving laser as well as waveguiding of the driving laser pulse. The discharge plasma also provides a means to spectrally tune the harmonics by tailoring the initial level of ionization of the medium.

  4. High-order momentum modes by resonant superradiant scattering

    SciTech Connect

    Zhou Xiaoji; Fu Jiageng; Chen Xuzong

    2009-12-15

    The spatial and time evolutions of superradiant scattering are studied theoretically for a weak pump beam with different frequency components traveling along the long axis of an elongated Bose-Einstein condensate. Resulting from the analysis for mode competition between the different resonant channels and the local depletion of the spatial distribution in the superradiant Rayleigh scattering, a method of getting a large number of high-order forward modes by resonant frequency components of the pump beam is provided, which is beneficial to a lager momentum transfer in atom manipulation for the atom interferometry and atomic optics.

  5. Highly Ordered Porous Anodic Alumina with Large Diameter Pores Fabricated by an Improved Two-Step Anodization Approach.

    PubMed

    Li, Xiaohong; Ni, Siyu; Zhou, Xingping

    2015-02-01

    The aim of this study is to prepare highly ordered porous anodic alumina (PAA) with large pore sizes (> 200 nm) by an improved two-step anodization approach which combines the first hard anodization in oxalic acid-water-ethanol system and second mild anodization in phosphoric acid-water-ethanol system. The surface morphology and elemental composition of PAA are characterized by field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectrometer (EDS). The effects of matching of two-step anodizing voltages on the regularity of pore arrangement is evaluated and discussed. Moreover, the pore formation mechanism is also discussed. The results show that the nanopore arrays on all the PAA samples are in a highly regular arrangement and the pore size is adjustable in the range of 200-300 nm. EDS analysis suggests that the main elements of the as-prepared PAA are oxygen, aluminum and a small amount of phosphorus. Furthermore, the voltage in the first anodization must match well with that in the second anodization, which has significant influence on the PAA regularity. The addition of ethanol to the electrolytes effectively accelerates the diffusion of the heat that evolves from the sample, and decreases the steady current to keep the steady growth of PAA film. The improved two-step anodization approach in this study breaks through the restriction of small pore size in oxalic acid and overcomes the drawbacks of irregular pore morphology in phosphoric acid, and is an efficient way to fabricate large diameter ordered PAA. PMID:26353721

  6. Optimization of High-order Wave Equations for Multicore CPUs

    Energy Science and Technology Software Center (ESTSC)

    2011-11-01

    This is a simple benchmark to guage the performance of a high-order isotropic wave equation grid. The code is optimized for both SSE and AVX and is parallelized using OpenMP (see Optimization section). Structurally, the benchmark begins, reads a few command-line parameters, allocates and pads the four arrays (current, last, next wave fields, and the spatially varying but isotropic velocity), initializes these arrays, then runs the benchmark proper. The code then benchmarks the naive, SSEmore » (if supported), and AVX (if supported implementations) by applying the wave equation stencil 100 times and taking the average performance. Boundary conditions are ignored and would noiminally be implemented by the user. THus, the benchmark measures only the performance of the wave equation stencil and not a full simulation. The naive implementation is a quadruply (z,y,x, radius) nested loop that can handle arbitrarily order wave equations. The optimized (SSE/AVX) implentations are somewhat more complex as they operate on slabs and include a case statement to select an optimized inner loop depending on wave equation order.« less

  7. Optimization of High-order Wave Equations for Multicore CPUs

    SciTech Connect

    Williams, Samuel

    2011-11-01

    This is a simple benchmark to guage the performance of a high-order isotropic wave equation grid. The code is optimized for both SSE and AVX and is parallelized using OpenMP (see Optimization section). Structurally, the benchmark begins, reads a few command-line parameters, allocates and pads the four arrays (current, last, next wave fields, and the spatially varying but isotropic velocity), initializes these arrays, then runs the benchmark proper. The code then benchmarks the naive, SSE (if supported), and AVX (if supported implementations) by applying the wave equation stencil 100 times and taking the average performance. Boundary conditions are ignored and would noiminally be implemented by the user. THus, the benchmark measures only the performance of the wave equation stencil and not a full simulation. The naive implementation is a quadruply (z,y,x, radius) nested loop that can handle arbitrarily order wave equations. The optimized (SSE/AVX) implentations are somewhat more complex as they operate on slabs and include a case statement to select an optimized inner loop depending on wave equation order.

  8. Genesis of charge orders in high temperature superconductors

    NASA Astrophysics Data System (ADS)

    Tu, Wei-Lin; Lee, Ting-Kuo

    2016-01-01

    One of the most puzzling facts about cuprate high-temperature superconductors in the lightly doped regime is the coexistence of uniform superconductivity and/or antiferromagnetism with many low-energy charge-ordered states in a unidirectional charge density wave or a bidirectional checkerboard structure. Recent experiments have discovered that these charge density waves exhibit different symmetries in their intra-unit-cell form factors for different cuprate families. Using a renormalized mean-field theory for a well-known, strongly correlated model of cuprates, we obtain a number of charge-ordered states with nearly degenerate energies without invoking special features of the Fermi surface. All of these self-consistent solutions have a pair density wave intertwined with a charge density wave and sometimes a spin density wave. Most of these states vanish in the underdoped regime, except for one with a large d-form factor that vanishes at approximately 19% doping of the holes, as reported by experiments. Furthermore, these states could be modified to have a global superconducting order, with a nodal-like density of states at low energy.

  9. NMR study of new ruthenates with high magnetic ordering

    NASA Astrophysics Data System (ADS)

    Paulose, P. L.; Chakrabarty, Tanmoy

    The Ru based compounds, Ca3LiRuO6 and Ca3NaRuO6 show unusually high magnetic ordering temperature. Extended super exchange model is invoked to explain the magnetic behavior in the isostructural compound Ca3LiOsO6. We have carried out NMR investigation on these two Ru-based compounds. Ca3LiRuO6 is a weak ferromagnet with a magnetic ordering temperature (TC) of 115 K which is explored by the temperature dependence of 7Li NMR line shift, line-width and spin-lattice relaxation rate (1/T1) . Above TC, a broad maximum is observed in the evolution of line-width of the spectra. We speculate that this feature might be attributed to some low-dimensional magnetic behavior. Contrastingly, Ca3NaRuO6 with similar structure and local geometry of the Ru5+ ions is a conventional antiferromagnet with a transition temperature of 90 K. The temperature dependence of 23Na NMR line shift and 1/T1 is studied across magnetic transition in Ca3NaRuO6. The temperature variation of line-width is found to be different compared to Ca3LiRuO6. In both these systems, 1/T1 decreases significantly below ordering temperature, characteristic of many antiferromagnetic systems.

  10. High Variability of Mitochondrial Gene Order among Fungi

    PubMed Central

    Aguileta, Gabriela; de Vienne, Damien M.; Ross, Oliver N.; Hood, Michael E.; Giraud, Tatiana; Petit, Elsa; Gabaldón, Toni

    2014-01-01

    From their origin as an early alpha proteobacterial endosymbiont to their current state as cellular organelles, large-scale genomic reorganization has taken place in the mitochondria of all main eukaryotic lineages. So far, most studies have focused on plant and animal mitochondrial (mt) genomes (mtDNA), but fungi provide new opportunities to study highly differentiated mtDNAs. Here, we analyzed 38 complete fungal mt genomes to investigate the evolution of mtDNA gene order among fungi. In particular, we looked for evidence of nonhomologous intrachromosomal recombination and investigated the dynamics of gene rearrangements. We investigated the effect that introns, intronic open reading frames (ORFs), and repeats may have on gene order. Additionally, we asked whether the distribution of transfer RNAs (tRNAs) evolves independently to that of mt protein-coding genes. We found that fungal mt genomes display remarkable variation between and within the major fungal phyla in terms of gene order, genome size, composition of intergenic regions, and presence of repeats, introns, and associated ORFs. Our results support previous evidence for the presence of mt recombination in all fungal phyla, a process conspicuously lacking in most Metazoa. Overall, the patterns of rearrangements may be explained by the combined influences of recombination (i.e., most likely nonhomologous and intrachromosomal), accumulated repeats, especially at intergenic regions, and to a lesser extent, mobile element dynamics. PMID:24504088

  11. Genesis of charge orders in high temperature superconductors

    PubMed Central

    Tu, Wei-Lin; Lee, Ting-Kuo

    2016-01-01

    One of the most puzzling facts about cuprate high-temperature superconductors in the lightly doped regime is the coexistence of uniform superconductivity and/or antiferromagnetism with many low-energy charge-ordered states in a unidirectional charge density wave or a bidirectional checkerboard structure. Recent experiments have discovered that these charge density waves exhibit different symmetries in their intra-unit-cell form factors for different cuprate families. Using a renormalized mean-field theory for a well-known, strongly correlated model of cuprates, we obtain a number of charge-ordered states with nearly degenerate energies without invoking special features of the Fermi surface. All of these self-consistent solutions have a pair density wave intertwined with a charge density wave and sometimes a spin density wave. Most of these states vanish in the underdoped regime, except for one with a large d-form factor that vanishes at approximately 19% doping of the holes, as reported by experiments. Furthermore, these states could be modified to have a global superconducting order, with a nodal-like density of states at low energy. PMID:26732076

  12. Single glass nanopore-based regenerable sensing platforms with a non-immobilized polyglutamic acid probe for selective detection of cupric ions.

    PubMed

    Chen, Lizhen; He, Haili; Xu, Xiaolong; Jin, Yongdong

    2015-08-19

    A single glass capillary nanopore-based sensing platform for rapid and selective detection of cupric ions is demonstrated by utilizing polyglutamic acid (PGA) as a non-immobilized probe. The detection is based on the significant decrease of ionic current through nanopore and the reversal of ion current rectification responses induced by the chelated cupric ions on the probes when in the presence of cupric ions. PGA shows high selectivity for detecting cupric ions rather than other metal ions. The sensitivity of the sensing platform can be improved about 1-2 orders of magnitude by employing asymmetric salt gradients during the measurements. And the PGA-based nanopore sensing platform shows excellent regenerability for Cu(2+) sensing applications. In addition, the method is found effective and reliable for the detection of cupric ions in real samples with small volume down to 20 μL. This nanopore-based sensing platform will find promising practical applications for the detection of cupric ions. PMID:26343431

  13. Nanoporous and Nanostructured Materials for Energy Storage and Sensor Applications

    NASA Astrophysics Data System (ADS)

    Vu, Anh D.

    The major objective of this work is to design nanostructured and nanoporous materials targeting the special needs of the energy storage and sensing fields. Nanostructured and nanoporous materials are increasingly finding applications in many fields, including electrical energy storage and explosive sensing. The advancement of energy storage devices is important to the development of three fields that have strong effects on human society: renewable energy, transportation, and portable devices. More sensitive explosive sensors will help to prevent terrorism activities and boost national security. Hierarchically porous LiFePO4 (LFP)/C composites were prepared using a surfactant and colloidal crystals as dual templates. The surfactant serves as the template for mesopores and polymeric colloidal spheres serve as the template for macropores. The confinement of the surfactant-LFP-carbon precursor in the colloidal templates is crucial to suppress the fast crystallization of LFP and helps to maintain the ordered structure. The obtained composites with high surface areas and ordered porous structure showed excellent rate performance when used as cathode materials for LIBs, which will allow them to be used as a power source for EVs and HEVs. The synthesis of LiFePO 4 in three dimensionally confined spaces within the colloidal template resulted in the formation of spherical particles. Densely packed LiFePO 4 spheres in a carbon matrix were obtained by spin-casting the LFP-carbon precursor on a quartz substrate and then pyrolyzing it. The product showed high capacity and could be charged /discharged with very little capacity fading over many cycles. Three-dimensionally ordered mesoporous carbons were prepared from nano-sized silica sphere colloidal crystal templates. These materials with very high surface areas and ordered porous structure showed high capacitance and excellent rate capability when used as electrodes for supercapacitors. Mesoporous silica thin films of different

  14. Clinical Risk Prediction by Exploring High-Order Feature Correlations

    PubMed Central

    Wang, Fei; Zhang, Ping; Wang, Xiang; Hu, Jianying

    2014-01-01

    Clinical risk prediction is one important problem in medical informatics, and logistic regression is one of the most widely used approaches for clinical risk prediction. In many cases, the number of potential risk factors is fairly large and the actual set of factors that contribute to the risk is small. Therefore sparse logistic regression is proposed, which can not only predict the clinical risk but also identify the set of relevant risk factors. The inputs of logistic regression and sparse logistic regression are required to be in vector form. This limits the applicability of these models in the problems when the data cannot be naturally represented vectors (e.g., medical images are two-dimensional matrices). To handle the cases when the data are in the form of multi-dimensional arrays, we propose HOSLR: High-Order Sparse Logistic Regression, which can be viewed as a high order extension of sparse logistic regression. Instead of solving one classification vector as in conventional logistic regression, we solve for K classification vectors in HOSLR (K is the number of modes in the data). A block proximal descent approach is proposed to solve the problem and its convergence is guaranteed. Finally we validate the effectiveness of HOSLR on predicting the onset risk of patients with Alzheimer’s disease and heart failure. PMID:25954428

  15. High-order finite element methods for cardiac monodomain simulations.

    PubMed

    Vincent, Kevin P; Gonzales, Matthew J; Gillette, Andrew K; Villongco, Christopher T; Pezzuto, Simone; Omens, Jeffrey H; Holst, Michael J; McCulloch, Andrew D

    2015-01-01

    Computational modeling of tissue-scale cardiac electrophysiology requires numerically converged solutions to avoid spurious artifacts. The steep gradients inherent to cardiac action potential propagation necessitate fine spatial scales and therefore a substantial computational burden. The use of high-order interpolation methods has previously been proposed for these simulations due to their theoretical convergence advantage. In this study, we compare the convergence behavior of linear Lagrange, cubic Hermite, and the newly proposed cubic Hermite-style serendipity interpolation methods for finite element simulations of the cardiac monodomain equation. The high-order methods reach converged solutions with fewer degrees of freedom and longer element edge lengths than traditional linear elements. Additionally, we propose a dimensionless number, the cell Thiele modulus, as a more useful metric for determining solution convergence than element size alone. Finally, we use the cell Thiele modulus to examine convergence criteria for obtaining clinically useful activation patterns for applications such as patient-specific modeling where the total activation time is known a priori. PMID:26300783

  16. High-order finite element methods for cardiac monodomain simulations

    PubMed Central

    Vincent, Kevin P.; Gonzales, Matthew J.; Gillette, Andrew K.; Villongco, Christopher T.; Pezzuto, Simone; Omens, Jeffrey H.; Holst, Michael J.; McCulloch, Andrew D.

    2015-01-01

    Computational modeling of tissue-scale cardiac electrophysiology requires numerically converged solutions to avoid spurious artifacts. The steep gradients inherent to cardiac action potential propagation necessitate fine spatial scales and therefore a substantial computational burden. The use of high-order interpolation methods has previously been proposed for these simulations due to their theoretical convergence advantage. In this study, we compare the convergence behavior of linear Lagrange, cubic Hermite, and the newly proposed cubic Hermite-style serendipity interpolation methods for finite element simulations of the cardiac monodomain equation. The high-order methods reach converged solutions with fewer degrees of freedom and longer element edge lengths than traditional linear elements. Additionally, we propose a dimensionless number, the cell Thiele modulus, as a more useful metric for determining solution convergence than element size alone. Finally, we use the cell Thiele modulus to examine convergence criteria for obtaining clinically useful activation patterns for applications such as patient-specific modeling where the total activation time is known a priori. PMID:26300783

  17. High-order unified symplectic FDTD scheme for the metamaterials

    NASA Astrophysics Data System (ADS)

    Ren, Xingang; Huang, Zhixiang; Wu, Xianliang; Lu, Silong; Wang, Hui; Wu, Lei; Li, Shen

    2012-06-01

    A high-order unified symplectic finite-difference time-domain (US-FDTD) method, which is energy conserved, for modeling the metamaterials is proposed. The lossless Drude dispersive model is taken into account in US-FDTD scheme, and the detailed formulations of the proposed US-FDTD method are also provided. The high-order split perfectly matched layers (SPML) are used as the absorbing boundary conditions (ABCs) to terminate the computational domain. The analysis of Courant stability and numerical dispersion demonstrate that US-FDTD scheme is more efficient than the traditional time domain numerical methods. Focusing and refocusing of the electromagnetic wave in target detection is validated using the normal incident Gaussian beam with a matched slab. Oblique incidence results associated with the inverse Snell effect and the phase compensation effect of the composite slab further demonstrated the efficiency of the method. Numerical results for a more realistic structure are also included. All the results agree well with the theoretical prediction. The method proposed here can be directly put into using as a time-domain full-wave simulation tool for applications in metamaterials.

  18. Nanoporous polymers for hydrogen storage.

    PubMed

    Germain, Jonathan; Fréchet, Jean M J; Svec, Frantisek

    2009-05-01

    The design of hydrogen storage materials is one of the principal challenges that must be met before the development of a hydrogen economy. While hydrogen has a large specific energy, its volumetric energy density is so low as to require development of materials that can store and release it when needed. While much of the research on hydrogen storage focuses on metal hydrides, these materials are currently limited by slow kinetics and energy inefficiency. Nanostructured materials with high surface areas are actively being developed as another option. These materials avoid some of the kinetic and thermodynamic drawbacks of metal hydrides and other reactive methods of storing hydrogen. In this work, progress towards hydrogen storage with nanoporous materials in general and porous organic polymers in particular is critically reviewed. Mechanisms of formation for crosslinked polymers, hypercrosslinked polymers, polymers of intrinsic microporosity, and covalent organic frameworks are discussed. Strategies for controlling hydrogen storage capacity and adsorption enthalpy via manipulation of surface area, pore size, and pore volume are discussed in detail. PMID:19360719

  19. Rectification of nanopores in aprotic solvents - transport properties of nanopores with surface dipoles

    NASA Astrophysics Data System (ADS)

    Plett, Timothy; Shi, Wenqing; Zeng, Yuhan; Mann, William; Vlassiouk, Ivan; Baker, Lane A.; Siwy, Zuzanna S.

    2015-11-01

    Nanopores have become a model system to understand transport properties at the nanoscale. We report experiments and modeling of ionic current in aprotic solvents with different dipole moments through conically shaped nanopores in a polycarbonate film and through glass nanopipettes. We focus on solutions of the salt LiClO4, which is of great importance in modeling lithium based batteries. Results presented suggest ion current rectification observed results from two effects: (i) adsorption of Li+ ions to the pore walls, and (ii) a finite dipole moment rendered by adsorbed solvent molecules. Properties of surfaces in various solvents were probed by means of scanning ion conductance microscopy, which confirmed existence of an effectively positive surface potential in aprotic solvents with high dipole moments.Nanopores have become a model system to understand transport properties at the nanoscale. We report experiments and modeling of ionic current in aprotic solvents with different dipole moments through conically shaped nanopores in a polycarbonate film and through glass nanopipettes. We focus on solutions of the salt LiClO4, which is of great importance in modeling lithium based batteries. Results presented suggest ion current rectification observed results from two effects: (i) adsorption of Li+ ions to the pore walls, and (ii) a finite dipole moment rendered by adsorbed solvent molecules. Properties of surfaces in various solvents were probed by means of scanning ion conductance microscopy, which confirmed existence of an effectively positive surface potential in aprotic solvents with high dipole moments. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06340j

  20. Dealloying-driven nanoporous palladium with superior electrochemical actuation performance

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Bai, Qingguo; Zhang, Zhonghua

    2016-03-01

    Metal-hydrogen (in particular, Pd-H) interactions have been receiving considerable attention over the past 150 years within the scope of hydrogen storage, catalytic hydrogenation, hydrogen embrittlement and hydrogen-induced interfacial failure. Here, for the first time, we show that the coupling of hydrogen adsorption and absorption could trigger giant reversible strain in bulk nanoporous Pd (np-Pd) in a weakly adsorbed NaF electrolyte. The bulk np-Pd with a hierarchically porous structure and a ligament/channel size of ~10 nm was fabricated using a dealloying strategy with compositional/structural design of the precursor. The np-Pd actuator exhibits a giant reversible strain of up to 3.28% (stroke of 137.8 μm), which is a 252% enhancement in comparison to the state-of-the-art value of 1.3% in np-AuPt. The strain rate (~10-5 s-1) of np-Pd is two orders of magnitude higher than that of current metallic actuators. Moreover, the volume-/mass-specific strain energy density (10.71 MJ m-3/3811 J kg-1) of np-Pd reaches the highest level compared with that of previously reported actuator materials. The outstanding actuation performance of np-Pd could be attributed to the coupling of hydrogen adsorption/absorption and its unique hierarchically nanoporous structure. Our findings provide valuable information for the design of novel high-performance metallic actuators.Metal-hydrogen (in particular, Pd-H) interactions have been receiving considerable attention over the past 150 years within the scope of hydrogen storage, catalytic hydrogenation, hydrogen embrittlement and hydrogen-induced interfacial failure. Here, for the first time, we show that the coupling of hydrogen adsorption and absorption could trigger giant reversible strain in bulk nanoporous Pd (np-Pd) in a weakly adsorbed NaF electrolyte. The bulk np-Pd with a hierarchically porous structure and a ligament/channel size of ~10 nm was fabricated using a dealloying strategy with compositional/structural design of the

  1. Measurement of DNA Translocation Dynamics in a Solid-State Nanopore at 100 ns Temporal Resolution.

    PubMed

    Shekar, Siddharth; Niedzwiecki, David J; Chien, Chen-Chi; Ong, Peijie; Fleischer, Daniel A; Lin, Jianxun; Rosenstein, Jacob K; Drndić, Marija; Shepard, Kenneth L

    2016-07-13

    Despite the potential for nanopores to be a platform for high-bandwidth study of single-molecule systems, ionic current measurements through nanopores have been limited in their temporal resolution by noise arising from poorly optimized measurement electronics and large parasitic capacitances in the nanopore membranes. Here, we present a complementary metal-oxide-semiconductor (CMOS) nanopore (CNP) amplifier capable of low noise recordings at an unprecedented 10 MHz bandwidth. When integrated with state-of-the-art solid-state nanopores in silicon nitride membranes, we achieve an SNR of greater than 10 for ssDNA translocations at a measurement bandwidth of 5 MHz, which represents the fastest ion current recordings through nanopores reported to date. We observe transient features in ssDNA translocation events that are as short as 200 ns, which are hidden even at bandwidths as high as 1 MHz. These features offer further insights into the translocation kinetics of molecules entering and exiting the pore. This platform highlights the advantages of high-bandwidth translocation measurements made possible by integrating nanopores and custom-designed electronics. PMID:27332998

  2. DNA motion induced by electrokinetic flow near an Au coated nanopore surface as voltage controlled gate

    NASA Astrophysics Data System (ADS)

    Sugimoto, Manabu; Kato, Yuta; Ishida, Kentaro; Hyun, Changbae; Li, Jiali; Mitsui, Toshiyuki

    2015-02-01

    We used fluorescence microscopy to investigate the diffusion and drift motion of λ DNA molecules on an Au-coated membrane surface near nanopores, prior to their translocation through solid-state nanopores. With the capability of controlling electric potential at the Au surface as a gate voltage, Vgate, the motions of DNA molecules, which are presumably generated by electrokinetic flow, vary dramatically near the nanopores in our observations. We carefully investigate these DNA motions with different values of Vgate in order to alter the densities and polarities of the counterions, which are expected to change the flow speed or direction, respectively. Depending on Vgate, our observations have revealed the critical distance from a nanopore for DNA molecules to be attracted or repelled—DNA’s anisotropic and unsteady drifting motions and accumulations of DNA molecules near the nanopore entrance. Further finite element method (FEM) numerical simulations indicate that the electrokinetic flow could qualitatively explain these unusual DNA motions near metal-collated gated nanopores. Finally, we demonstrate the possibility of controlling the speed and direction of DNA motion near or through a nanopore, as in the case of recapturing a single DNA molecule multiple times with alternating current voltages on the Vgate.

  3. DNA motion induced by electrokinetic flow near an Au coated nanopore surface as voltage controlled gate.

    PubMed

    Sugimoto, Manabu; Kato, Yuta; Ishida, Kentaro; Hyun, Changbae; Li, Jiali; Mitsui, Toshiyuki

    2015-02-13

    We used fluorescence microscopy to investigate the diffusion and drift motion of λ DNA molecules on an Au-coated membrane surface near nanopores, prior to their translocation through solid-state nanopores. With the capability of controlling electric potential at the Au surface as a gate voltage, Vgate, the motions of DNA molecules, which are presumably generated by electrokinetic flow, vary dramatically near the nanopores in our observations. We carefully investigate these DNA motions with different values of Vgate in order to alter the densities and polarities of the counterions, which are expected to change the flow speed or direction, respectively. Depending on Vgate, our observations have revealed the critical distance from a nanopore for DNA molecules to be attracted or repelled-DNA's anisotropic and unsteady drifting motions and accumulations of DNA molecules near the nanopore entrance. Further finite element method (FEM) numerical simulations indicate that the electrokinetic flow could qualitatively explain these unusual DNA motions near metal-collated gated nanopores. Finally, we demonstrate the possibility of controlling the speed and direction of DNA motion near or through a nanopore, as in the case of recapturing a single DNA molecule multiple times with alternating current voltages on the Vgate. PMID:25611963

  4. DNA Motion Induced by Electrokinetic Flow near an Au Coated Nanopore Surface as Voltage Controlled Gate

    PubMed Central

    Sugimoto, Manabu; Kato, Yuta; Ishida, Kentaro; Hyun, Changbae; Li, Jiali

    2014-01-01

    The diffusion and drift motion of λ DNA molecules on Au coated membrane surface near nanopores prior to their translocation through solid-state nanopores are investigated using fluorescence microscopy. With the capability of controlling electric potential at the Au surface as a gate voltage, Vgate, the motions of DNA molecules vary dramatically near the nanopores in our observations, presumably generated by electrokinetic flow. We carefully investigate theses DNA motions with different values of Vgate in order to alter the densities and polarities of counterions; which are expected to change the flow speed or direction, respectively. Depending on Vgate, our observations have revealed the critical distance from a nanopore for DNA molecules to be attracted or to be repelled, DNA’s anisotropic and unsteady drifting motions and accumulations of DNA molecules near the nanopore entrance. Further finite element method (FEM) numerical simulations indicate that the electrokinetic flow could explain these unusual DNA motions near metal collated gated nanopores qualitatively. Finally, we demonstrate the possibility to control the speed and direction of DNA motion near or through a nanopore, for example, recapturing a single DNA molecule multiple times with AC voltages on the Vgate. PMID:25611963

  5. Highly ordered periodic mesoporous organosilica nanoparticles with controllable pore structures

    NASA Astrophysics Data System (ADS)

    Guan, Buyuan; Cui, Yan; Ren, Zhongyuan; Qiao, Zhen-An; Wang, Li; Liu, Yunling; Huo, Qisheng

    2012-09-01

    A general synthetic procedure for highly ordered and well-dispersed periodic mesoporous organosilica (PMO) nanoparticles is reported based on a single cationic surfactant cetyltrimethylammonium bromide (CTAB) and simple silica sources with organic bridging groups via an ammonia-catalyzed sol-gel reaction. By changing the bridging group in the silica sources, the pore structures of the as-made particles with three-dimensional hexagonal (P63/mmc), cubic (Pm3n), two-dimensional hexagonal (P6mm), and wormlike structure were evidenced by powder X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). The size range of the nanoparticles can be adjusted from 30 nm to 500 nm by variation of the ammonia concentration or the co-solvent content of the reaction medium. The PMO nanoparticles with high concentration of organic groups in the framework offered good thermal stability, good dispersion in low polarity solvent and high adsorption of small hydrophobic molecules. Finally, the dye functionalized PMO nanoparticles show low cytotoxicity and excellent cell permeability, which offers great potential for biomedical applications.A general synthetic procedure for highly ordered and well-dispersed periodic mesoporous organosilica (PMO) nanoparticles is reported based on a single cationic surfactant cetyltrimethylammonium bromide (CTAB) and simple silica sources with organic bridging groups via an ammonia-catalyzed sol-gel reaction. By changing the bridging group in the silica sources, the pore structures of the as-made particles with three-dimensional hexagonal (P63/mmc), cubic (Pm3n), two-dimensional hexagonal (P6mm), and wormlike structure were evidenced by powder X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). The size range of the nanoparticles can be adjusted from 30 nm to 500 nm by variation of the ammonia concentration or the co-solvent content of the reaction medium. The PMO nanoparticles with high concentration of organic

  6. Resistively detected high-order magnetoplasmons in a high-quality 2D electron gas

    NASA Astrophysics Data System (ADS)

    Zudov, M. A.; Shi, Q.; Pfeiffer, L. N.; West, K. W.; Watson, J. D.; Manfra, M. J.

    We report on high-order magnetoplasmon resonances detected in photoresistance in high-mobility GaAs quantum wells. These resonances manifest themselves as a series of resistance extrema in the regime of Shubnikov-de Haas oscillations. Extending to orders above 20, the extrema exhibit alternating strength, being less (more) pronounced at even (odd) order magnetoplasmon modes. The lower magnetoplasmon modes reveal the importance of retardation effects.

  7. Biosensing with integrated CMOS nanopores

    NASA Astrophysics Data System (ADS)

    Uddin, Ashfaque; Yemenicioglu, Sukru; Chen, Chin-Hsuan; Corgliano, Ellie; Milaninia, Kaveh; Xia, Fan; Plaxco, Kevin; Theogarajan, Luke

    2012-10-01

    This paper outlines our recent efforts in using solid-state nanopores as a biosensing platform. Traditionally biosensors concentrate mainly on the detection platform and not on signal processing. This decoupling can lead to inferior sensors and is exacerbated in nanoscale devices, where device noise is large and large dynamic range is required. This paper outlines a novel platform that integrates the nano, micro and macroscales in a closely coupled manner that mitigates many of these problems. We discuss our initial results of DNA translocation through the nanopore. We also briefly discuss the use of molecular recognition properties of aptamers with the versatility of the nanopore detector to design a new class of biosensors in a CMOS compatible platform.

  8. The high-order quantum coherence of thermal light

    NASA Astrophysics Data System (ADS)

    Chen, Hui

    Thermal light, such as sunlight, is usually considered classical light. In a macroscopic picture, classical theory successfully explained the first-order coherence phenomena of thermal light. The macroscopic theory, based on the statistical behavior of light intensity fluctuations, however, can only phenomenologically explain the second- or higher-order coherence phenomena of thermal light. This thesis introduces a microscopic quantum picture, based on the interferences of a large number of randomly distributed and randomly radiated subfields, wavepackets or photons, to the study of high-order coherence of thermal light. This thesis concludes that the second-order intensity fluctuation correlation is caused by nonlocal interference: a pair of wavepackets, which are randomly paired together, interferes with the pair itself at two distant space-time coordinates. This study has the following practical motivations: (1) to simulate N-qbits. Practical quantum computing requires quantum bits(qubits) of N-digit to represent all possible integers from 0 to 2N-1 simultaneously. A large number of independent particles can be prepared to represent a large set of N orthogonal |0> and |1> bits. In fact, based on our recent experiments of simulating the high-order correlation of entangled photons, thermal radiation is suggested as a promising source for quantum information processing. (2) to achieve sunlight ghost imaging. Ghost imaging has three attractive non-classical features: (a) the ghost camera can "see" targets that can never be seen by a classic camera; (2) it is turbulence-free; and (3) its spatial resolution is mainly determined by the angular diameter of the light source. For example, a sunlight ghost image of an object on earth may achieve a spatial resolution of 200 micrometer because the angular diameter of sun is 0.53 degree with respect to Earth. Although ghost imaging has been experimental demonstrated by using entangled photon pairs and "pseudo-thermal light

  9. Ion and water transport in charge-modified graphene nanopores

    NASA Astrophysics Data System (ADS)

    Qiu, Ying-Hua; Li, Kun; Chen, Wei-Yu; Si, Wei; Tan, Qi-Yan; Chen, Yun-Fei

    2015-10-01

    Porous graphene has a high mechanical strength and an atomic-layer thickness that makes it a promising material for material separation and biomolecule sensing. Electrostatic interactions between charges in aqueous solutions are a type of strong long-range interaction that may greatly influence fluid transport through nanopores. In this study, molecular dynamic simulations were conducted to investigate ion and water transport through 1.05-nm diameter monolayer graphene nanopores, with their edges charge-modified. Our results indicated that these nanopores are selective to counterions when they are charged. As the charge amount increases, the total ionic currents show an increase-decrease profile while the co-ion currents monotonically decrease. The co-ion rejection can reach 76.5% and 90.2% when the nanopores are negatively and positively charged, respectively. The Cl- ion current increases and reaches a plateau, and the Na+ current decreases as the charge amount increases in systems in which Na+ ions act as counterions. In addition, charge modification can enhance water transport through nanopores. This is mainly due to the ion selectivity of the nanopores. Notably, positive charges on the pore edges facilitate water transport much more strongly than negative charges. Project supported by the National Basic Research Program of China (Grant Nos. 2011CB707601 and 2011CB707605), the National Natural Science Foundation of China (Grant No. 50925519), the Fundamental Research Funds for the Central Universities, Funding of Jiangsu Provincial Innovation Program for Graduate Education, China (Grant No. CXZZ13_0087), and the Scientific Research Foundation of Graduate School of Southeast University (Grant No. YBJJ 1322).

  10. Raman fingerprinting of single dielectric nanoparticles in plasmonic nanopores

    NASA Astrophysics Data System (ADS)

    Kerman, Sarp; Chen, Chang; Li, Yi; van Roy, Wim; Lagae, Liesbet; van Dorpe, Pol

    2015-11-01

    Plasmonic nano-apertures are commonly used for the detection of small particles such as nanoparticles and proteins by exploiting electrical and optical techniques. Plasmonic nanopores are metallic nano-apertures sitting on a thin membrane with a tiny hole. It has been shown that plasmonic nanopores with a given geometry identify internal molecules using Surface Enhanced Raman Spectroscopy (SERS). However, label-free identification of a single dielectric nanoparticle requires a highly localized field comparable to the size of the particle. Additionally, the particle's Brownian motion can jeopardize the amount of photons collected from a single particle. Here, we demonstrate that the combination of optical trapping and SERS can be used for the detection and identification of 20 nm polystyrene nanoparticles in plasmonic nanopores. This work is anticipated to contribute to the detection of small bioparticles, optical trapping and nanotribology studies.Plasmonic nano-apertures are commonly used for the detection of small particles such as nanoparticles and proteins by exploiting electrical and optical techniques. Plasmonic nanopores are metallic nano-apertures sitting on a thin membrane with a tiny hole. It has been shown that plasmonic nanopores with a given geometry identify internal molecules using Surface Enhanced Raman Spectroscopy (SERS). However, label-free identification of a single dielectric nanoparticle requires a highly localized field comparable to the size of the particle. Additionally, the particle's Brownian motion can jeopardize the amount of photons collected from a single particle. Here, we demonstrate that the combination of optical trapping and SERS can be used for the detection and identification of 20 nm polystyrene nanoparticles in plasmonic nanopores. This work is anticipated to contribute to the detection of small bioparticles, optical trapping and nanotribology studies. Electronic supplementary information (ESI) available: Fig. S1: The

  11. Three-dimensional structures of magnesium nanopores

    NASA Astrophysics Data System (ADS)

    Wu, Shujing; Zheng, He; Jia, Shuangfeng; Sheng, Huaping; Cao, Fan; Li, Lei; Hu, Shuaishuai; Zhao, Penghui; Zhao, Dongshan; Wang, Jianbo

    2016-03-01

    The optimization of nanopore-based devices is closely related to the nanopore three-dimensional (3D) structures. In this paper, faceted nanopores were fabricated in magnesium (Mg) by aligning the electron beam (e-beam) along the [0001] direction. Detailed structural characterization by transmission electron microscopy reveals the existence of two 3D structures: hexagonal prism-shaped and hourglass-shaped 3D morphologies. Moreover, the 3D structures of nanopores are also found to depend on the widest nanopore diameter-to-thickness ratio (D/t). A plausible formation mechanism for different 3D structures is discussed. Our results incorporate a critical piece of information regarding the nanopore 3D structures in Mg and may serve as an important design guidance for the size- and shape-controllable fabrication of solid-state nanopores applying the e-beam sculpting technique.

  12. Nanoporous Metal - Combining Strength and Porosity

    SciTech Connect

    Biener, J; Hodge, A M; Hayes, J R; Volkert, C A; Zepeda-Ruiz, L A; Hamza, A V; Abraham, F F

    2006-05-17

    Recent nanomechanical tests on submicron metal columns and wires have revealed a dramatic increase in yield strength with decreasing sample size. This effect seems to be related to the increased strength observed in metals on decreasing grain size or film thickness, and has been explained by a dislocation nucleation/activation controlled plasticity regime in small sample volumes. The question arises whether one can utilize this new size effect to design materials with improved bulk properties. Here, we demonstrate that nanoporous metal foams can be envisioned as a three-dimensional network of ultrahigh-strength nanocolumns/wires, thus bringing together two seemingly conflicting properties: high strength and high porosity. Specifically, we studied the mechanical properties of nanoporous (np) Au using a combination of nanoindentation and column microcompression tests, as well as supplemental molecular dynamics simulations. We find that np-Au can be as strong as bulk Au, despite being a highly porous material, and that the ligaments in np-Au approach the theoretical yield strength of Au. The combination of high yield strength and high porosity can be used to design a new generation of energy absorbing materials for various engineering applications.

  13. Magnetic nanoporous carbon as an adsorbent for the extraction of phthalate esters in environmental water and aloe juice samples.

    PubMed

    Liu, Li; Hao, Yunhui; Ren, Yiqian; Wang, Chun; Wu, Qiuhua; Wang, Zhi

    2015-05-01

    In this work, magnetic nanoporous carbon with high surface area and ordered structure was synthesized using cheap commercial silica gel as template and sucrose as the carbon source. The prepared magnetic nanoporous carbon was firstly used as an adsorbent for the extraction of phthalate esters, including diethyl phthalate, diallyl phthalate, and di-n-propyl-phthalate, from lake water and aloe juice samples. Several parameters that could affect the extraction efficiency were optimized. Under the optimum conditions, the limit of detection of the method (S/N = 3) was 0.10 ng/mL for water sample and 0.20 ng/mL for aloe juice sample. The linearity was observed over the concentration range of 0.50-150.0 and 1.0-200.0 ng/mL for water and aloe juice samples, respectively. The results showed that the magnetic nanoporous carbon has a high adsorptive capability toward the target phthalate esters in water and aloe juice samples. PMID:25677269

  14. Cross-Talk Between Ionic and Nanoribbon Current Signals in Graphene Nanoribbon-Nanopore Sensors for Single-Molecule Detection.

    PubMed

    Puster, Matthew; Balan, Adrian; Rodríguez-Manzo, Julio A; Danda, Gopinath; Ahn, Jae-Hyuk; Parkin, William; Drndić, Marija

    2015-12-16

    Nanopores are now being used not only as an ionic current sensor but also as a means to localize molecules near alternative sensors with higher sensitivity and/or selectivity. One example is a solid-state nanopore embedded in a graphene nanoribbon (GNR) transistor. Such a device possesses the high conductivity needed for higher bandwidth measurements and, because of its single-atomic-layer thickness, can improve the spatial resolution of the measurement. Here measurements of ionic current through the nanopore are shown during double-stranded DNA (dsDNA) translocation, along with the simultaneous response of the neighboring GNR due to changes in the surrounding electric potential. Cross-talk originating from capacitive coupling between the two measurement channels is observed, resulting in a transient response in the GNR during DNA translocation; however, a modulation in device conductivity is not observed via an electric-field-effect response during DNA translocation. A field-effect response would scale with GNR source-drain voltage (Vds), whereas the capacitive coupling does not scale with Vds . In order to take advantage of the high bandwidth potential of such sensors, the field-effect response must be enhanced. Potential field calculations are presented to outline a phase diagram for detection within the device parameter space, charting a roadmap for future optimization of such devices. PMID:26500023

  15. Global Monte Carlo Simulation with High Order Polynomial Expansions

    SciTech Connect

    William R. Martin; James Paul Holloway; Kaushik Banerjee; Jesse Cheatham; Jeremy Conlin

    2007-12-13

    The functional expansion technique (FET) was recently developed for Monte Carlo simulation. The basic idea of the FET is to expand a Monte Carlo tally in terms of a high order expansion, the coefficients of which can be estimated via the usual random walk process in a conventional Monte Carlo code. If the expansion basis is chosen carefully, the lowest order coefficient is simply the conventional histogram tally, corresponding to a flat mode. This research project studied the applicability of using the FET to estimate the fission source, from which fission sites can be sampled for the next generation. The idea is that individual fission sites contribute to expansion modes that may span the geometry being considered, possibly increasing the communication across a loosely coupled system and thereby improving convergence over the conventional fission bank approach used in most production Monte Carlo codes. The project examined a number of basis functions, including global Legendre polynomials as well as “local” piecewise polynomials such as finite element hat functions and higher order versions. The global FET showed an improvement in convergence over the conventional fission bank approach. The local FET methods showed some advantages versus global polynomials in handling geometries with discontinuous material properties. The conventional finite element hat functions had the disadvantage that the expansion coefficients could not be estimated directly but had to be obtained by solving a linear system whose matrix elements were estimated. An alternative fission matrix-based response matrix algorithm was formulated. Studies were made of two alternative applications of the FET, one based on the kernel density estimator and one based on Arnoldi’s method of minimized iterations. Preliminary results for both methods indicate improvements in fission source convergence. These developments indicate that the FET has promise for speeding up Monte Carlo fission source

  16. Rapid removal of bisphenol A on highly ordered mesoporous carbon.

    PubMed

    Sui, Qian; Huang, Jun; Liu, Yousong; Chang, Xiaofeng; Ji, Guangbin; Deng, Shubo; Xie, Tao; Yu, Gang

    2011-01-01

    Bisphenol A (BPA) is of global concern due to its disruption of endocrine systems and ubiquity in the aquatic environment. It is important, therefore, that efforts are made to remove it from the aqueous phase. A novel adsorbent, mesoporous carbon CMK-3, prepared from hexagonal SBA-15 mesoporous silica was studied for BPA removal from aqueous phase, and compared with conventional powdered activated carbon (PAC). Characterization of CMK-3 by transmission electron microscopy (TEM), X-ray diffraction, and nitrogen adsorption indicated that prepared CMK-3 had an ordered mesoporous structure with a high specific surface area of 920 m2/g and a pore-size of about 4.9 nm. The adsorption of BPA on CMK-3 followed a pseudo second-order kinetic model. The kinetic constant was 0.00049 g/(mg x min), much higher than the adsorption of BPA on PAC. The adsorption isotherm fitted slightly better with the Freundlich model than the Langmuir model, and adsorption capacity decreased as temperature increased from 10 to 40 degrees C. No significant influence of pH on adsorption was observed at pH 3 to 9; however, adsorption capacity decreased dramatically from pH 9 to 13. PMID:21516989

  17. Self assembly of highly-ordered nanoparticle monolayers.

    SciTech Connect

    Bigioni, T. P.; Lin, X.-M.; Nguyen, T. T.; Corwin, E. I.; Witten, T. A.; Jaeger, H. M.; Univ. of Chicago

    2006-01-01

    When a drop of a colloidal solution of nanoparticles dries on a surface, it leaves behind coffee-stain-like rings of material with lace-like patterns or clumps of particles in the interior. These non-uniform mass distributions are manifestations of far-from-equilibrium effects, such as fluid flows and solvent fluctuations during late-stage drying. However, recently a strikingly different drying regime promising highly uniform, long-range-ordered nanocrystal monolayers has been found. Here we make direct, real-time and real-space observations of nanocrystal self-assembly to reveal the mechanism. We show how the morphology of drop-deposited nanoparticle films is controlled by evaporation kinetics and particle interactions with the liquid-air interface. In the presence of an attractive particle-interface interaction, rapid early-stage evaporation dynamically produces a two-dimensional solution of nanoparticles at the liquid-air interface, from which nanoparticle islands nucleate and grow. This self-assembly mechanism produces monolayers with exceptional long-range ordering that are compact over macroscopic areas, despite the far-from-equilibrium evaporation process. This new drop-drying regime is simple, robust and scalable, is insensitive to the substrate material and topography, and has a strong preference for forming monolayer films. As such, it stands out as an excellent candidate for the fabrication of technologically important ultra thin film materials for sensors, optical devices and magnetic storage media.

  18. High-order social interactions in groups of mice

    PubMed Central

    Shemesh, Yair; Sztainberg, Yehezkel; Forkosh, Oren; Shlapobersky, Tamar; Chen, Alon; Schneidman, Elad

    2013-01-01

    Social behavior in mammals is often studied in pairs under artificial conditions, yet groups may rely on more complicated social structures. Here, we use a novel system for tracking multiple animals in a rich environment to characterize the nature of group behavior and interactions, and show strongly correlated group behavior in mice. We have found that the minimal models that rely only on individual traits and pairwise correlations between animals are not enough to capture group behavior, but that models that include third-order interactions give a very accurate description of the group. These models allow us to infer social interaction maps for individual groups. Using this approach, we show that environmental complexity during adolescence affects the collective group behavior of adult mice, in particular altering the role of high-order structure. Our results provide new experimental and mathematical frameworks for studying group behavior and social interactions. DOI: http://dx.doi.org/10.7554/eLife.00759.001 PMID:24015357

  19. Transparent boundary conditions for iterative high-order parabolic equations

    NASA Astrophysics Data System (ADS)

    Petrov, P. S.; Ehrhardt, M.

    2016-05-01

    Recently a new approach to the construction of high-order parabolic approximations for the Helmholtz equation was developed. These approximations have the form of the system of iterative parabolic equations, where the solution of the n-th equation is used as an input term for the (n + 1)-th equation. In this study the transparent boundary conditions for such systems of coupled parabolic equations are derived. The existence and uniqueness of the solution of the initial boundary value problem for the system of iterative parabolic equations with the derived boundary conditions are proved. The well-posedness of this problem is also established and an unconditionally stable finite difference scheme for its solution is proposed.

  20. High-order harmonic generation enhanced by XUV light

    NASA Astrophysics Data System (ADS)

    Buth, Christian; Kohler, Markus C.; Ullrich, Joachim; Keitel, Christoph H.

    2011-09-01

    The combination of high-order harmonic generation (HHG) with resonant XUV excitation of a core electron into the transient valence vacancy that is created in the course of the HHG process is investigated theoretically. In this setup, the first electron performs a HHG three-step process, whereas the second electron Rabi flops between the core and the valence vacancy. The modified HHG spectrum due to recombination with the valence and the core is determined and analyzed for krypton on the 3d→4p resonance in the ion. We assume an 800nm laser with an intensity of about 1014Wcm2 and XUV radiation from the Free Electron Laser in Hamburg (FLASH) with an intensity in the range 1013--1016Wcm2. Our prediction opens perspectives for nonlinear XUV physics, attosecond x rays, and HHG-basedspectroscopy involving core orbitals.

  1. A robust high-order ideal magnetohydrodynamic solver

    NASA Astrophysics Data System (ADS)

    Seal, David; Christlieb, Andrew; Feng, Xiao; Tang, Qi

    In this work we present a robust high-order numerical method for the ideal magnetohydrodynamics (MHD) equations. Our method is single-stage and single-step, and hence amenable to adaptive mesh refinement (AMR) technology. The numerical robustness of the scheme is realized by accomplishing a total of two unrelated tasks: we retain positivity of the density and pressure by limiting fluxes similar to what happens in a flux corrected transport method, and we obtain divergence free magnetic fields by implementing an unstaggered transport method for the evolution of the magnetic potential. We present numerical results in two and three dimensions that indicate the utility of the scheme. These results include several classical test problems such as Orzag-Tang, cloud shock interactions and blast wave problems.

  2. High-order harmonic generation enhanced by XUV light

    SciTech Connect

    Buth, Christian; Kohler, Markus C.; Ullrich, Joachim; Keitel, Christoph H.

    2012-03-19

    The combination of high-order harmonic generation (HHG) with resonant XUV excitation of a core electron into the transient valence vacancy that is created in the course of the HHG process is investigated theoretically. In this setup, the first electron performs a HHG three-step process, whereas the second electron Rabi flops between the core and the valence vacancy. The modified HHG spectrum due to recombination with the valence and the core is determined and analyzed for krypton on the 3d {yields} 4p resonance in the ion. We assume an 800 nm laser with an intensity of about 10{sup 14} Wcm{sup 2} and XUV radiation from the Free Electron Laser in Hamburg (FLASH) with an intensity in the range 10{sup 13}-10{sup 16} Wcm{sup 2}. Our prediction opens perspectives for nonlinear XUV physics, attosecond x rays, and HHG-based spectroscopy involving core orbitals.

  3. High-order jamming crossovers and density anomalies.

    PubMed

    Pica Ciamarra, Massimo; Sollich, Peter

    2013-10-28

    We demonstrate that particles interacting via core-softened potentials exhibit a series of successive density anomalies upon isothermal compression, leading to oscillations in the diffusivity and thermal expansion coefficient, with the latter reaching negative values. These finite-temperature density anomalies are then shown to correspond to zero-temperature high-order jamming crossovers. These occur when particles are forced to come into contact with neighbours in successive coordination shells upon increasing the density. The crossovers induce anomalous behavior of the bulk modulus, which oscillates with density. We rationalize the dependence of these crossovers on the softness of the interaction potential, and relate the jamming crossovers and the anomalous diffusivity via the properties of the vibrational spectrum. PMID:26029762

  4. High-order harmonic generation and Fano resonances

    NASA Astrophysics Data System (ADS)

    Strelkov, V. V.; Khokhlova, M. A.; Shubin, N. Yu

    2014-05-01

    We present a high-order harmonic generation theory which generalizes the strong-field approximation to the resonant case when the harmonic frequency is close to that of the transition from the ground state to an autoionizing state of the generating system. We show that the line shape of the resonant harmonic is a product of the Fano-like factor and the harmonic line which would be emitted in the absence of the resonance. The theory predicts rapid variation of the harmonic phase in the vicinity of the resonance. The calculated resonant harmonic phase is in reasonable agreement with recent measurements. Predicting the phase locking of a group of resonantly enhanced harmonics, our theory allows us to study the perspectives of producing an attosecond pulse train using such harmonics.

  5. Emission times in high-order harmonic generation

    SciTech Connect

    Chirila, C. C.; Dreissigacker, I.; Lein, M.; Zwan, E. V. van der

    2010-03-15

    We calculate the emission times of the radiation in high-order harmonic generation using the Gabor transform of numerical data obtained from solving the time-dependent Schroedinger equation in one, two, and three dimensions. Both atomic and molecular systems, including nuclear motion, are investigated. Lewenstein model calculations are used to gauge the performance of the Gabor method. The resulting emission times are compared against the classical simple man's model as well as against the more accurate quantum orbit model based on complex trajectories. The influence of the range of the binding potential (long or short) on the level of agreement is assessed. Our analysis reveals that the short-trajectory harmonics are emitted slightly earlier than predicted by the quantum orbit model. This partially explains recent experimental observations for atoms and molecules. Furthermore, we observe a distinct signature of two-center interference in the emission times for H{sub 2} and D{sub 2}.

  6. High-order multiphoton photoelectric effect at midinfrared laser wavelengths

    SciTech Connect

    Georges, A.T.

    2002-12-01

    A theoretical model that predicts the unexpectedly high photocurrents that were reported by Farkas et al. [J. Phys. B 31, L461 (1998)] for the photoelectric effect in gold at midinfrared laser wavelengths (12 {mu}m) is presented. It is shown that the observed effect, a nominally 46-photon process at threshold, is a stepwise and multiple-order process, which is strongly saturated at the moderate laser intensity of about {approx}10 MW/cm{sup 2}. The {approx_equal}30-photon-wide energy spectrum of the observed photoelectron current is due to above threshold photoemission. This relatively efficient above threshold effect is due to laser absorption in the long range Coulombic image surface potential.

  7. High-Order Space-Time Methods for Conservation Laws

    NASA Technical Reports Server (NTRS)

    Huynh, H. T.

    2013-01-01

    Current high-order methods such as discontinuous Galerkin and/or flux reconstruction can provide effective discretization for the spatial derivatives. Together with a time discretization, such methods result in either too small a time step size in the case of an explicit scheme or a very large system in the case of an implicit one. To tackle these problems, two new high-order space-time schemes for conservation laws are introduced: the first is explicit and the second, implicit. The explicit method here, also called the moment scheme, achieves a Courant-Friedrichs-Lewy (CFL) condition of 1 for the case of one-spatial dimension regardless of the degree of the polynomial approximation. (For standard explicit methods, if the spatial approximation is of degree p, then the time step sizes are typically proportional to 1/p(exp 2)). Fourier analyses for the one and two-dimensional cases are carried out. The property of super accuracy (or super convergence) is discussed. The implicit method is a simplified but optimal version of the discontinuous Galerkin scheme applied to time. It reduces to a collocation implicit Runge-Kutta (RK) method for ordinary differential equations (ODE) called Radau IIA. The explicit and implicit schemes are closely related since they employ the same intermediate time levels, and the former can serve as a key building block in an iterative procedure for the latter. A limiting technique for the piecewise linear scheme is also discussed. The technique can suppress oscillations near a discontinuity while preserving accuracy near extrema. Preliminary numerical results are shown

  8. A highly ordered cubic mesoporous silica/graphene nanocomposite

    NASA Astrophysics Data System (ADS)

    Lee, Chang-Wook; Roh, Kwang Chul; Kim, Kwang-Bum

    2013-09-01

    A highly ordered cubic mesoporous silica (KIT-6)/graphene nanocomposite and 2D KIT-6 nanoflakes were synthesized using a novel synthesis methodology. The non-ionic triblock copolymer, P123, played a dual role as a structure-directing agent in the formation of the cubic mesoporous structure and as a cross-linking agent between mesoporous silica and graphene. The prepared (KIT-6)/graphene nanocomposite could act as a template for the preparation of mesoporous material/graphene nanocomposites.A highly ordered cubic mesoporous silica (KIT-6)/graphene nanocomposite and 2D KIT-6 nanoflakes were synthesized using a novel synthesis methodology. The non-ionic triblock copolymer, P123, played a dual role as a structure-directing agent in the formation of the cubic mesoporous structure and as a cross-linking agent between mesoporous silica and graphene. The prepared (KIT-6)/graphene nanocomposite could act as a template for the preparation of mesoporous material/graphene nanocomposites. Electronic supplementary information (ESI) available: S1: TEM images of disordered mesoporous silica/graphene nanocomposite; S2: TEM images of KIT-6/GO nanocomposite; S3: Thermogravimetric analysis of KIT-6/GO and KG-400-700; S4: SEM and TEM images of KIT-6; S5: Low angle XRD, Raman spectra, N2 adsorption isotherms, pore size distribution and photographic images of the prepared samples; S6: TEM image and N2 adsorption isotherms of mesoporous carbon/graphene nanocomposite; S7: XPS C1s spectra of the prepared samples. See DOI: 10.1039/c3nr03108j

  9. Synergetic Effects of Nanoporous Support and Urea on Enzyme Activity

    SciTech Connect

    Lei, Chenghong; Shin, Yongsoon; Liu, Jun; Ackerman, Eric J.

    2007-02-01

    Here we report that synergetic effects of functionalized nanoporous support and urea on enzyme activity enhancement. Even in 8.0 M urea, the specific activity of GI entrapped in FMS was still higher than the highest specific activity of GI free in solution, indicating the strong tolerance of GI in FMS to the high concentration of urea.

  10. AAO-assisted synthesis of highly ordered, large-scale TiO2 nanowire arrays via sputtering and atomic layer deposition.

    PubMed

    Yao, Zhao; Wang, Cong; Li, Yang; Kim, Nam-Young

    2015-01-01

    Highly ordered nanoporous anodic aluminum oxide (AAO) thin films were fabricated in oxalic acid under a constant voltage via a two-step anodization process. To investigate the high-aspect-ratio (7.5:1) filling process, both sputtering and atomic layer deposition (ALD) were used to form TiO2 nanowires. Field emission scanning electron microscopy and high-resolution transmission electron microscopy images indicated that mushroom-like TiO2 structures were sputtered onto the AAO template surface, and the ALD-coated TiO2 exhibited fine filling results and clear crystal grain boundaries. Large-scale and free-standing TiO2 nanowire arrays were liberated by selectively removing the aluminum substrate and AAO template via a wet etching process with no collapsing or agglomeration after the drying process. ALD-deposited TiO2 nanowire arrays that were 67 nm in diameter and 400 nm high were transferred from the AAO template. The ALD process enabled the rapid, simple synthesis of highly ordered TiO2 nanowire arrays with desired parameters such as diameter, density, and thickness determined using diverse AAO templates. PMID:25897309

  11. AAO-assisted synthesis of highly ordered, large-scale TiO2 nanowire arrays via sputtering and atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Yao, Zhao; Wang, Cong; Li, Yang; Kim, Nam-Young

    2015-04-01

    Highly ordered nanoporous anodic aluminum oxide (AAO) thin films were fabricated in oxalic acid under a constant voltage via a two-step anodization process. To investigate the high-aspect-ratio (7.5:1) filling process, both sputtering and atomic layer deposition (ALD) were used to form TiO2 nanowires. Field emission scanning electron microscopy and high-resolution transmission electron microscopy images indicated that mushroom-like TiO2 structures were sputtered onto the AAO template surface, and the ALD-coated TiO2 exhibited fine filling results and clear crystal grain boundaries. Large-scale and free-standing TiO2 nanowire arrays were liberated by selectively removing the aluminum substrate and AAO template via a wet etching process with no collapsing or agglomeration after the drying process. ALD-deposited TiO2 nanowire arrays that were 67 nm in diameter and 400 nm high were transferred from the AAO template. The ALD process enabled the rapid, simple synthesis of highly ordered TiO2 nanowire arrays with desired parameters such as diameter, density, and thickness determined using diverse AAO templates.

  12. High-order computational fluid dynamics tools for aircraft design.

    PubMed

    Wang, Z J

    2014-08-13

    Most forecasts predict an annual airline traffic growth rate between 4.5 and 5% in the foreseeable future. To sustain that growth, the environmental impact of aircraft cannot be ignored. Future aircraft must have much better fuel economy, dramatically less greenhouse gas emissions and noise, in addition to better performance. Many technical breakthroughs must take place to achieve the aggressive environmental goals set up by governments in North America and Europe. One of these breakthroughs will be physics-based, highly accurate and efficient computational fluid dynamics and aeroacoustics tools capable of predicting complex flows over the entire flight envelope and through an aircraft engine, and computing aircraft noise. Some of these flows are dominated by unsteady vortices of disparate scales, often highly turbulent, and they call for higher-order methods. As these tools will be integral components of a multi-disciplinary optimization environment, they must be efficient to impact design. Ultimately, the accuracy, efficiency, robustness, scalability and geometric flexibility will determine which methods will be adopted in the design process. This article explores these aspects and identifies pacing items. PMID:25024419

  13. Phase properties of the cutoff high-order harmonics

    NASA Astrophysics Data System (ADS)

    Khokhlova, M. A.; Strelkov, V. V.

    2016-04-01

    The cutoff regime of high-order harmonic generation (HHG) by atoms in an intense laser field is studied numerically and analytically. We find that the cutoff regime is characterized by equal dephasing between the successive harmonics. The change of the harmonic phase locking when HHG evolves from the cutoff to the plateau regime determines the optimal bandwidth of the spectral region which should be used for attosecond pulse generation via the amplitude gating technique. The minimal pulse duration which can be obtained with this technique in argon without using dispersion elements is approximately 0.08-0.1 of the laser cycle for different intensities and frequencies of the fundamental. The cutoff regime is also characterized by a linear dependence of the harmonic phase on the fundamental intensity. The proportionality coefficient grows as the cube of the fundamental wavelength, thus this dependence becomes very important for the HHG by midinfrared fields. Moreover, for every high harmonic there is a range of laser intensities providing the generation in the cutoff regime and the atomic response magnitude in this regime can be greater than that in the plateau regime. Thus, the cutoff regime substantially contributes to the harmonic energy emitted under typical experimental conditions where the laser intensity varies in time and space.

  14. High-order computational fluid dynamics tools for aircraft design

    PubMed Central

    Wang, Z. J.

    2014-01-01

    Most forecasts predict an annual airline traffic growth rate between 4.5 and 5% in the foreseeable future. To sustain that growth, the environmental impact of aircraft cannot be ignored. Future aircraft must have much better fuel economy, dramatically less greenhouse gas emissions and noise, in addition to better performance. Many technical breakthroughs must take place to achieve the aggressive environmental goals set up by governments in North America and Europe. One of these breakthroughs will be physics-based, highly accurate and efficient computational fluid dynamics and aeroacoustics tools capable of predicting complex flows over the entire flight envelope and through an aircraft engine, and computing aircraft noise. Some of these flows are dominated by unsteady vortices of disparate scales, often highly turbulent, and they call for higher-order methods. As these tools will be integral components of a multi-disciplinary optimization environment, they must be efficient to impact design. Ultimately, the accuracy, efficiency, robustness, scalability and geometric flexibility will determine which methods will be adopted in the design process. This article explores these aspects and identifies pacing items. PMID:25024419

  15. Temperature dependence of DNA translocations through solid-state nanopores

    PubMed Central

    Verschueren, Daniel V.; Jonsson, Magnus P.; Dekker, Cees

    2015-01-01

    In order to gain a better physical understanding of DNA translocations through solid-state nanopores, we study the temperature dependence of λ-DNA translocations through 10 nm-in-diameter silicon-nitride nanopores, both experimentally and theoretically. The measured ionic conductance G, the DNA-induced ionic-conductance blockades ΔG and the event frequency Γ all increase with increasing temperature while the DNA translocation time τ decreases. G and ΔG are accurately described when bulk and surface conductances of the nanopore are considered and access resistance is incorporated appropriately. Viscous drag on the untranslocated part of the DNA coil is found to dominate the temperature dependence of the translocation times and the event rate is well described by a balance between diffusion and electrophoretic motion. The good fit between modeled and measured properties of DNA translocations through solid-state nanopores in this first comprehensive temperature study, suggest that our model captures the relevant physics of the process. PMID:25994084

  16. Probe DNA-Cisplatin Interaction with Solid-State Nanopores

    NASA Astrophysics Data System (ADS)

    Zhou, Zhi; Hu, Ying; Li, Wei; Xu, Zhi; Wang, Pengye; Bai, Xuedong; Shan, Xinyan; Lu, Xinghua; Nanopore Collaboration

    2014-03-01

    Understanding the mechanism of DNA-cisplatin interaction is essential for clinical application and novel drug design. As an emerging single-molecule technology, solid-state nanopore has been employed in biomolecule detection and probing DNA-molecule interactions. Herein, we reported a real-time monitoring of DNA-cisplatin interaction by employing solid-state SiN nanopores. The DNA-cisplatin interacting process is clearly classified into three stages by measuring the capture rate of DNA-cisplatin adducts. In the first stage, the negative charged DNA molecules were partially discharged due to the bonding of positive charged cisplatin and forming of mono-adducts. In the second stage, forming of DNA-cisplatin di-adducts with the adjacent bases results in DNA bending and softening. The capture rate increases since the softened bi-adducts experience a lower barrier to thread into the nanopores. In the third stage, complex structures, such as micro-loop, are formed and the DNA-cisplatin adducts are aggregated. The capture rate decreases to zero as the aggregated adduct grows to the size of the pore. The characteristic time of this stage was found to be linear with the diameter of the nanopore and this dynamic process can be described with a second-order reaction model. We are grateful to Laboratory of Microfabrication, Dr. Y. Yao, and Prof. R.C. Yu (Institute of Physics, Chinese Academy of Sciences) for technical assistance.

  17. Irradiation response and stability of nanoporous materials

    SciTech Connect

    Fu, Engang; Wang, Yongqiang; Serrano De Caro, Magdalena; Caro, Jose A.; Zepeda-Ruiz, L; Bringa, E.; Nastasi, Mike; Baldwin, Jon K.

    2012-08-28

    Nanoporous materials consist of a regular organic or inorganic framework supporting a regular, porous structure. Pores are by definition roughly in the nanometre range, that is between 0.2 nm and 100 nm. Nanoporous materials can be subdivided into 3 categories (IUPAC): (1) Microporous materials - 0.2-2 nm; (2) Mesoporous materials - 2-50 nm; and (3) Macroporous materials - 50-1000 nm. np-Au foams were successfully synthesized by de-alloying process. np-Au foams remain porous structure after Ne ion irradiation to 1 dpa. Stacking Fault Tetrahedra (SFTs) were observed in RT irradiated np-Au foams under the highest and intermediate fluxes, but not under the lowest flux. SFTs were not observed in LNT irradiated np-Au foams under all fluxes. The vacancy diffusivity in Au at RT is high enough so that the vacancies have enough time to agglomerate and then collapse to form SFTs. The high ion flux creates more damage per unit time; vacancies don't have enough time to diffuse or recombine. As a result, SFTs were formed at high ion fluxes.

  18. Graphene nanopores as negative differential resistance devices

    SciTech Connect

    Qiu, Wanzhi; Nguyen, Phuong Duc; Skafidas, Efstratios

    2015-02-07

    We present graphene nanopores as new negative differential resistance (NDR) devices, and study their quantum transport properties using non-equilibrium Green's function and the density functional tight binding method. The proposed device structure is created on intrinsic armchair-edged graphene nanoribbons with uniform widths, where the central scattering region has a nanopore in the interior, and the two ends of the nanoribbon act naturally as connecting electrodes. We show that nitrogen-passivated scattering regions generally result in pronounced NDR properties, while hydrogen-passivated ones do not. This NDR effect occurs at low bias voltages, below 1 V, and achieves extraordinarily high peak-to-valley current ratio, while still attaining very high peak current densities. In addition, very sharp current peaks in the μA range can occur in the I-V curves, and through varying structural dimensions of the proposed structure multiple NDR regions can be realized. These results suggest that the device has promising potential in applications such as high frequency oscillators, memory devices, and fast switches.

  19. Resistively detected high-order magnetoplasmons in a high-quality two-dimensional electron gas

    NASA Astrophysics Data System (ADS)

    Shi, Q.; Zudov, M. A.; Pfeiffer, L. N.; West, K. W.; Watson, J. D.; Manfra, M. J.

    2016-04-01

    We report on high-order magnetoplasmon resonances detected in photoresistance in high-mobility GaAs quantum wells. These resonances manifest themselves as a series of photoresistance extrema in the regime of Shubnikov-de Haas oscillations. Extending to orders as high as 25, the extrema exhibit alternating strength, being less (more) pronounced at even- (odd)-order magnetoplasmon modes. This experimental technique provides a sensitive and elegant means to detect and investigate multiple magnetoplasmon modes and could be applied to other systems.

  20. Low-cost photoelectrocatalyst based on a nanoporous oxide layer of low-carbon steel

    NASA Astrophysics Data System (ADS)

    Rangaraju, Raghu R.; Raja, K. S.; Panday, A.; Misra, M.

    2010-11-01

    Low-carbon steel is a commonly used structural material in a wide variety of applications. An anodic oxide layer of this inexpensive alloy has been noted to have interesting photoelectrochemical behaviour similar to that of α-Fe2O3 prepared using other expensive starting materials. An ordered nanoporous oxide layer has been grown on to the low-carbon steel surface by a simple electrochemical anodization process in different electrolytes such as ethylene glycol containing 0.05M NH4F and 3-10 vol% water and 0.5M phosphoric acid solution containing 0.05M NH4F. After anodization, the nanoporous anodic oxide layer has been transformed to α-Fe2O3 by a low-temperature annealing process. Photoelectrochemical characterization of the anodic iron oxide materials has been carried out in 1M KOH electrolyte under a solar simulated illumination using Air Mass (AM) 1.5. The ordered nanoporous oxide layer prepared in ethylene glycol-based electrolyte showed a photocurrent density of about 85 µA cm-2 at 0.4 VAg/AgCl. Whereas the anodic iron oxide prepared by anodization of the low-carbon steel in 0.5M H3PO4 + 0.05M NaF solution showed a photocurrent density of 800 µA cm-2 at 0.4 VAg/AgCl. The improved photoactivity of the phosphate-modified oxide layer could be attributed to the high charge carrier concentration, low charge transfer resistance and better ability to expend holes in the oxygen evolution reaction.